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Sample records for sr-nd isotope study

  1. The origin and geodynamic significance of the Alpine cordierite-bearing granitoids of northern Algeria. A combined petrological, mineralogical, geochemical and isotopic (O, H, Sr, Nd) study

    NASA Astrophysics Data System (ADS)

    Fourcade, Serge; Capdevila, Ramon; Ouabadi, Aziouz; Martineau, François

    2001-06-01

    In northern Algeria, the coastal area displays a very variegated magmatism of Miocene age, extending E-W over 900 km with a width of less than 50 km. This magmatism includes both plutonic and volcanic massifs containing basic, intermediate to acidic rock types. Two groups may be identified on the basis of the chemistry and mineralogy. The first group has a calc-alkaline metaluminous chemistry and contains mainly " high-K" types, sometimes " medium-K" and exceptionally "low-K" types. They are gabbros and basalts, diorites and andesites, tonalites and dacites. Some granitoids (quartz-monzonites, granodiorites and syenogranites) possess affinities with this magmatism (Bejaia-Amizour and Thenia intrusions). Only mafic to intermediate enclaves of magmatic origin are found in granitoids from this group. The second group has strongly peraluminous compositions: they are cordierite-bearing granodiorites, monzogranites and microgranites, as well as dacites and rhyolites (ignimbrites). Two types of enclaves exist in these granitoids: (i) microgranular metaluminous hornblende-bearing enclaves of igneous derivation, (ii) strongly peraluminous enclaves of metapelitic compositions. Textures and mineralogical associations indicate that the enclaves experienced heating at decreasing pressures and also partial melting. Therefore, they are indicative of assimilation, not of restite unmixing. After removing the local effects of hydrothermal alteration, the O, Sr, Nd isotopic compositions of parent magmas were determined: they span a very large range of values, e.g., ɛNd (T) varies from +12 (Cap Bougaroun gabbros) to -10 (Crd-bearing granitoids). From the covariation of Sr-Nd isotopic compositions and the constraints of O isotopic ratios, the following sources are proposed for the different rock types: Mafic to intermediate rocks contain a subduction-related component but most of them require contamination at crustal levels. The source of metaluminous granitoids is predominantly

  2. Potential uses of stable isotope ratios of Sr, Nd, and Pb in geological materials for environmental studies

    PubMed Central

    NAKANO, Takanori

    2016-01-01

    The ratios of stable isotopes of certain elements in rocks and minerals have strong regional characteristics that are reflected in atmospheric components, in water, and in the living organisms that form Earth’s surface environment as well as in agricultural and fishery products. Geologically derived stable isotope ratios can be used as a tracer for the source of many kinds of substances, with current geochemical techniques allowing the precise determination of numerous stable isotope ratios in both natural and manmade objects. This review presents examples of the use of stable isotopes as tracers within diverse dynamic ecosystems, focusing on Sr isotopes but also including examples of Nd and Pb isotopic analysis, and reviewing the potential of this technique for a wide range of environmental research, including determining the geographic origin of food and archeological materials. PMID:27302069

  3. Potential uses of stable isotope ratios of Sr, Nd, and Pb in geological materials for environmental studies.

    PubMed

    Nakano, Takanori

    2016-01-01

    The ratios of stable isotopes of certain elements in rocks and minerals have strong regional characteristics that are reflected in atmospheric components, in water, and in the living organisms that form Earth's surface environment as well as in agricultural and fishery products. Geologically derived stable isotope ratios can be used as a tracer for the source of many kinds of substances, with current geochemical techniques allowing the precise determination of numerous stable isotope ratios in both natural and manmade objects. This review presents examples of the use of stable isotopes as tracers within diverse dynamic ecosystems, focusing on Sr isotopes but also including examples of Nd and Pb isotopic analysis, and reviewing the potential of this technique for a wide range of environmental research, including determining the geographic origin of food and archeological materials. PMID:27302069

  4. The Kipushi Cu-Zn deposit (DR Congo) and its host rocks: A petrographical, stable isotope (O, C) and radiogenic isotope (Sr, Nd) study

    NASA Astrophysics Data System (ADS)

    Van Wilderode, J.; Heijlen, W.; De Muynck, D.; Schneider, J.; Vanhaecke, F.; Muchez, Ph.

    2013-03-01

    Near the city of Kipushi, located in the southern part of the Central African Copperbelt, a major vein-type Cu-Zn ore deposit occurs. A combination of petrographic techniques and both stable (O, C) and radiogenic (Sr, Nd) isotope analysis is used to investigate the influence of the mineralisation on the Neoproterozoic dolomite host rocks. A quantification of the abundance and size of the different host rock constituents (dolomite types, quartz, phyllosilicates) revealed a lithostratigraphical controlled variation, without trends towards the ore body. The bulk oxygen isotopic composition of the host rock varies between -2.54‰ and -9.64‰ V-PDB, with most values within the range of Neoproterozoic marine dolomite. Samples with more positive δ18O all originate from the same stratigraphic interval and are interpreted as the result of reflux dolomitisation by an evaporated brine. Few samples with depleted δ18O signatures could indicate the influence of a depleted or high temperature fluid, but are not related to the ore deposit. Moreover, the presence of the ore body cannot be traced through the host rock oxygen isotopic composition. δ18O of gangue dolomite is significantly depleted in comparison with the host rocks and ranges between -7.67‰ and -12.46‰ V-PDB. For an estimated mineralisation temperature of 310 °C, this implies a δ18Ofluid between 10.7‰ and 15.6‰ V-SMOW. This is a significant enrichment compared to Neoproterozoic seawater, indicating that the mineralising fluid underwent significant fluid-rock interactions. δ13C of both host rock and gangue dolomite are in range of Neoproterozoic marine dolomites. However, a limited stratigraphic interval has clearly more negative δ13C signatures, due to in situ maturation of carbonaceous material. At the time of mineralisation (450 Ma), the host rock dolomite has a strontium isotopic composition partly more radiogenic than Neoproterozoic marine carbonates (0.70793 < 87Sr/86Sr < 0.71167). Nevertheless

  5. A radiogenic isotopic (He-Sr-Nd-Pb-Os) study of lavas from the Pitcairn hotspot: Implications for the origin of EM-1 (enriched mantle 1)

    NASA Astrophysics Data System (ADS)

    Garapić, G.; Jackson, M. G.; Hauri, E. H.; Hart, S. R.; Farley, K. A.; Blusztajn, J. S.; Woodhead, J. D.

    2015-07-01

    We present new He-Sr-Nd-Pb-Os isotopic compositions and major and trace-element concentrations for ten subaerially-erupted lavas and one seamount lava associated with the Pitcairn hotspot. The most geochemically-enriched lavas at the Pitcairn hotspot have signatures that are consistent with recycled sediments derived from upper continental crust. Pitcairn lavas have elevated Ti, which also supports the presence of a mafic protolith in the Pitcairn mantle. A subset of Pitcairn seamount samples, including the seamount sample presented here, are tholeiitic. Tholeiitic lavas are uncommon at ocean hotspots located far from mid-ocean ridges. Like tholeiites that erupted in Hawaii, the presence of tholeiites in the Pitcairn magmatic suite can be explained by melting a silica-saturated recycled mafic component in the Pitcairn mantle source. We also present the highest 3He/4He ratio (12.6 Ra, ratio to atmosphere) from the Pitcairn hotspot. This sample anchors the high 206Pb/204Pb portion of the Pitcairn array and provides evidence for a plume component in the Pitcairn mantle. In contrast, Pitcairn lavas that have the lowest 206Pb/204Pb are the most geochemically enriched, and have the highest 87Sr/86Sr and lowest 143Nd/144Nd in the Pitcairn suite; these EM-1 end-member lavas have MORB-like 3He/4He (~ 8 Ra, ratio to atmosphere). Recycled oceanic crust and sediment suggested to be in the Pitcairn EM-1 mantle are expected to have low 3He/4He (< 0.1 Ra). Therefore, the higher, MORB-like 3He/4He in Pitcairn EM-1 lavas is paradoxical, but might be explained by diffusive exchange of helium, but not the heavy radiogenic isotopes, with the ambient mantle over billion-year timescales.

  6. Modeling crust-mantle evolution using radiogenic Sr, Nd, and Pb isotope systematics

    NASA Astrophysics Data System (ADS)

    Kumari, Seema; Paul, Debajyoti

    2015-04-01

    The present-day elemental and isotopic composition of Earth's terrestrial reservoirs can be used as geochemical constraints to study evolution of the crust-mantle system. A flexible open system evolutionary model of the Earth, comprising continental crust (CC), upper depleted mantle (UM) -source of mid-ocean ridge basalts (MORB), and lower mantle (LM) reservoir with a D" layer -source of ocean island basalts (OIB), and incorporating key radioactive isotope systematics (Rb-Sr, Sm-Nd, and U-Th-Pb), is solved numerically at 1 Ma time step for 4.55 Ga, the age of the Earth. The best possible solution is the one that produces the present-day concentrations as well as isotopic ratios in terrestrial reservoirs, compiled from published data. Different crustal growth scenarios (exponential, episodic, early and late growth), proposed in earlier studies, and its effect on the evolution of isotope systematics of terrestrial reservoirs is studied. Model simulations strongly favor a layered mantle structure satisfying majority of the isotopic constraints. In the successful model, which is similar to that proposed by Kellogg et al. (1999), the present-day UM comprises of 60% of mantle mass and extends to a depth 1600 km, whereas the LM becomes non-primitive and more enriched than the bulk silicate Earth, mainly due to addition of recycled crustal material. Modeling suggest that isotopic evolution of reservoirs is affected by the mode of crustal growth. Only two scenarios satisfied majority of the Rb-Sr and Sm-Nd isotopic constraints but failed to reproduce the present-day Pb-isotope systematics; exponential growth of crust (mean age, tc=2.3 Ga) and delayed and episodic growth (no growth for initial 900 Ma, tc=2.05 Ga) proposed by Patchett and Arndt (1986). However, assuming a slightly young Earth (4.45 Ga) better satisfies the Pb-isotope systematics. Although, the delayed crustal growth model satisfied Sr-Nd isotopic constraints, presence of early Hadean crust (4.03 and 4.4 Ga

  7. Pb-Sr-Nd isotope study of the 100- to 2700-Ma old alkalic rock-carbonatite complexes in the Canadian shield: inferences on the geochemical and structural evolution of the mantle

    SciTech Connect

    Kwon, S.T.

    1986-01-01

    The isotopic signatures of young continental alkalic complexes (CAC) display a remarkable similarity to those of oceanic island basalts (OIB). A study of Sr isotopic evolution showed that the mantle, presumably similar to the source of OIB, beneath the shield appears to have been depleted in large ion lithophile elements (LILE) and to have remained as a closed system since ca. 3000 Ma ago. The present investigations apply Pb and Nd as well as Sr isotopic systems for those complexes to study the secular geochemical evolution of the mantle over the past 2700 million years, and address the question of the processes responsible for the geochemical heterogeneity of the mantle. The data suggest: (1) Like Sr, Pb and Nd isotopic data indicate LILE depleted sources for the southern Canadian shield CAC over at least the past 1900 Ma. (2) Sr, Nd and Pb are compatible with an age of ca. 3000 Ma for the depleted source. (3) In contrast to Sr, and probably Nd, the Pb isotopic data cannot be explained by a closed system model for the depleted mantle source. (4) Coherent fractionation patterns are observed in the mantle sources of CAC since at least 1900 Ma ago: higher U/Pb and Sm/Nd, and lower Th/U and Rb/Sr ratios versus lower U/Pb and Sm/Nd, and higher Th/U and Rb/Sr ratios, indicating OlB-like sources for CAC. (5) The inverse correlation between /sup 206/Pb//sup 204/Pb and /sup 87/Sr//sup 86/Sr initial ratios permit calculation of apparent mean earth Pb isotope ratios with time, which yield 8.35 for the present day /sup 238/U//sup 204/Pb ratio, and 17.82 for /sup 206/Pb//sup 204/Pb. (6) A model for the geochemical and structural evolution of the mantle is based on the diverging isotopic evolution of the midocean ridge basalts (MORB) and OlB sources.

  8. A Sr-Nd isotopic study of sand-sized sediment provenance and transport for the San Francisco Bay coastal system

    USGS Publications Warehouse

    Rosenbauer, Robert J.; Foxgrover, Amy C.; Hein, James R.; Swarzenski, Peter W.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    A diverse suite of geochemical tracers, including 87Sr/86Sr and 143Nd/144Nd isotope ratios, the rare earth elements (REEs), and select trace elements were used to determine sand-sized sediment provenance and transport pathways within the San Francisco Bay coastal system. This study complements a large interdisciplinary effort (Barnard et al., 2012) that seeks to better understand recent geomorphic change in a highly urbanized and dynamic estuarine-coastal setting. Sand-sized sediment provenance in this geologically complex system is important to estuarine resource managers and was assessed by examining the geographic distribution of this suite of geochemical tracers from the primary sources (fluvial and rock) throughout the bay, adjacent coast, and beaches. Due to their intrinsic geochemical nature, 143Nd/144Nd isotopic ratios provide the most resolved picture of where sediment in this system is likely sourced and how it moves through this estuarine system into the Pacific Ocean. For example, Nd isotopes confirm that the predominant source of sand-sized sediment to Suisun Bay, San Pablo Bay, and Central Bay is the Sierra Nevada Batholith via the Sacramento River, with lesser contributions from the Napa and San Joaquin Rivers. Isotopic ratios also reveal hot-spots of local sediment accumulation, such as the basalt and chert deposits around the Golden Gate Bridge and the high magnetite deposits of Ocean Beach. Sand-sized sediment that exits San Francisco Bay accumulates on the ebb-tidal delta and is in part conveyed southward by long-shore currents. Broadly, the geochemical tracers reveal a complex story of multiple sediment sources, dynamic intra-bay sediment mixing and reworking, and eventual dilution and transport by energetic marine processes. Combined geochemical results provide information on sediment movement into and through San Francisco Bay and further our understanding of how sustained anthropogenic activities which limit sediment inputs to the system (e

  9. Changing styles of crustal growth in Southern Africa: Constraints from geochemical and Sr-Nd isotope studies in Archaean to Pan African terrains

    NASA Technical Reports Server (NTRS)

    Mcdermott, F.; Hawkesworth, C. J.; Harris, N. B. W.

    1988-01-01

    Nd isotopic data was presented for southern Africa in support of episodic crustal growth. Over 50 percent of the continental crust there had formed before 2.5 Ga, and less than 10 percent was produced after about 1.0 Ga. The data imply a mean crustal age of about 2.4 Ga for southern Africa, and a higher rate of crustal growth than that derived from Australian shale data, particularly during the Proterozoic. Isotopic data from Damara metasediments imply that there is no need to invoke decoupling of the Rb-Sr and Sm-Nd systems in the continental crust.

  10. Combined Sr, Nd, Pb and Hf isotopic constraints on the origin of Shatsky Rise (NW Pacific)

    NASA Astrophysics Data System (ADS)

    Geldmacher, J.; Heydolph, K.; Murphy, D. T.; Romanova, I.; Mahoney, J. J.; Hoernle, K.

    2012-12-01

    The submarine Shatsky Rise plateau in the northwest Pacific Ocean (ca. 1500 km east of Japan) formed during the Late Jurassic to Early Cretaceous. Based on magnetic reversals combined with bathymetric data, the three main volcanic edifices Tamu, Ori and Shirshov massifs are proposed to have successively formed by massive volcanism along a southwest-northeast moving, rapidly spreading triple junction. To investigate a proposed interaction of a possible mantle plume head with the spreading system, Shatsky Rise was drilled during IODP Expedition 324 in 2009 (Expedition 324 Scientists, 2010). Based on major and trace element compositions, the origin of the vast majority of the recovered rocks can be explained by derivation from a normal mid-ocean ridge basalt (MORB)-like source, although a distinct depletion in heavy rare earth elements implies that melting started at greater depth (Sano et al. in press). A small fraction of samples (all from Ori massif), however, exhibit higher ratios of highly over moderately incompatible trace element ratios indicating an enriched (plume?) source. We present compiled Sr, Nd, Pb and Hf isotope ratios from all three volcanic edifices of Shatsky Rise and will discuss them in the light of the new trace element study. Most isotope data overlap with Pacific MORB composition although regional variations can be seen. Whereas lavas from three drill sites on the oldest edifice, Tamu massif, yield fairly uniform compositions, a wider spread is found for lavas erupted on the younger edifices, Ori and Shirshov, suggesting that the source has become more heterogeneous with time (also consistent with the trace element data). This variation could reflect a decreasing degree of melting (and therefore less homogenization of inherent plume heterogeneities) or less effective stirring and mixing during the interaction of the spreading center with a waning plume head. Interestingly, lavas from the Ori and Shirshov massifs have generally lower 143Nd/144Nd

  11. Elemental and Sr-Nd isotopic geochemistry of Permian Emeishan flood basalts in Zhaotong, Yunnan Province, SW China

    NASA Astrophysics Data System (ADS)

    Li, Juan; Zhong, Hong; Zhu, Wei-Guang; Bai, Zhong-Jie; Hu, Wen-Jun

    2016-05-01

    This study presents new whole-rock elemental and isotopic data for the basalts from the Zhaotong area, located in the intermediate zone of the ~260 Ma Emeishan large igneous province (ELIP). The Zhaotong basalts belong to high-Ti series with TiO2 from 2.93 to 5.26 % and Ti/Y from 519 to 974. The parental magma was subjected to minor crustal contamination as indicated by slight Nb-Ta depletion (Nb/La: 0.72-1.10). Meanwhile, the relatively invariable Sr-Nd isotopes (ɛNd(t): -0.74 to +2.86, mostly +1.10 to +2.86; (87Sr/86Sr)i: 0.7050-0.7072) and the light rare earth elements (LREE) enrichment (La/Yb: 10.3-19.1) of the basalts prefer a mantle plume origin. A garnet-dominated peridotite mantle source was further suggested on the basis of the REE distribution patterns and high Sm/Yb and high La/Yb ratios. This study further confirms the geochemical zoning of the high-Ti basalts in the ELIP, which is in accordance with both the spatial distribution and the thickness of the basalts. The high-Ti basalts in the intermediate and outer zones of ELIP (e.g., Zhaotong and Guizhou) share similar Sr-Nd isotopic and elemental compositions, suggesting that they originated directly from the Emeishan mantle plume. By contrast, the high-Ti basalts in the inner zone (e.g., Longzhoushan and Binchuan) have variable compositions, indicating a rather heterogeneous mantle source possibly involved with subcontinental lithospheric mantle (SCLM) components.

  12. Identification of recycled continental material in the mantle from Sr, Nd and Pb isotope investigations

    NASA Astrophysics Data System (ADS)

    Cohen, R. S.; O'Nions, R. K.

    1982-11-01

    Pb, Nd and Sr isotope compositions of oceanic basalts have been used to identify recycled components of continent derivation in the mantle. The isotopic compositions of Sr, Nd and Pb, together with U, Pb, Sm, Nd, Rb, and Sr abundances have been determined for back-arc basalt glasses from the Scotia Sea and Parece Vela and West Philippine Basins, in addition to basalts from South Sandwich Islands, Ascension, St. Helena and Tristan da Cunha. Comparisons made between the isotopic compositions of South Sandwich Islands basalts and Atlantic MORB glasses permit the identification of recycled components of continent derivation in the source of the island arc basalts. Recycled Sr of continent derivation is also recognisable in back-arc basalt glasses from the Scotia Sea and Parece Vela and West Philippine Basins. However, contemporary reinjection of material with the isotopic structures similar to those identified as a component of island arc and back-arc regions cannot be the sole or dominant influence on the fine structure observed in MORB glasses from the Atlantic Ocean, nor the isotopic compositions of Tristan da Cunha, St. Helena and Ascension basalts. Recycled materials are likely to have been responsible for the generation of these heterogeneities only if they have been stored in the mantle for periods of time exceeding 10 9 years.

  13. Contamination in mafic mineral-rich calc-alkaline granites: a geochemical and Sr-Nd isotope study of the Neoproterozoic Piedade Granite, SE Brazil.

    PubMed

    Leite, Renato J; Janasi, Valdecir A; Martins, Lucelene

    2006-06-01

    The Piedade Granite (approximately 600 Ma) was emplaced shortly after the main phase of granite magmatism in the Agudos Grandes batholith, Apiaí-Guaxupé Terrane, SE Brazil. Its main units are: mafic mineral-rich porphyritic granites forming the border (peraluminous muscovite-biotite granodiorite-monzogranite MBmg unit) and core (metaluminous titanite-bearing biotite monzogranite BmgT unit) and felsic pink inequigranular granite (Bmg unit) between them. Bmg has high LaN/YbN (up to 100), Th/U (> 10) and low Rb, Nb and Ta, and can be a crustal melt derived from deep-seated sources with residual garnet and biotite. The core BmgT unit derived from oxidized magmas with high Mg# (approximately 45), Ba and Sr, fractionated REE patterns (LaN/YbN = 45), 87Sr/86Sr(t) approximately 0.710, epsilonNd(t) approximately -12 to -14, interpreted as being high-K calc-alkaline magmas contaminated with metasedimentary rocks that had upper-crust signature (high U, Cs, Ta). The mafic-rich peraluminous granites show a more evolved isotope signature (87Sr/86Sr(t) = 0.713-0.714; epsilonNd(t) = -14 to -16), similar to Bmg, and Mg# and incompatible trace-element concentrations intermediate between Bmg and BmgT. A model is presented in whichMBmgis envisaged as the product of contamination between a mafic mineral-rich magma consanguineous with BmgT and pure crustal melts akin to Bmg. PMID:16710571

  14. Contamination in mafic mineral-rich calc-alkaline granites: a geochemical and Sr-Nd isotope study of the Neoproterozoic Piedade Granite, SE Brazil.

    PubMed

    Leite, Renato J; Janasi, Valdecir A; Martins, Lucelene

    2006-06-01

    The Piedade Granite (approximately 600 Ma) was emplaced shortly after the main phase of granite magmatism in the Agudos Grandes batholith, Apiaí-Guaxupé Terrane, SE Brazil. Its main units are: mafic mineral-rich porphyritic granites forming the border (peraluminous muscovite-biotite granodiorite-monzogranite MBmg unit) and core (metaluminous titanite-bearing biotite monzogranite BmgT unit) and felsic pink inequigranular granite (Bmg unit) between them. Bmg has high LaN/YbN (up to 100), Th/U (> 10) and low Rb, Nb and Ta, and can be a crustal melt derived from deep-seated sources with residual garnet and biotite. The core BmgT unit derived from oxidized magmas with high Mg# (approximately 45), Ba and Sr, fractionated REE patterns (LaN/YbN = 45), 87Sr/86Sr(t) approximately 0.710, epsilonNd(t) approximately -12 to -14, interpreted as being high-K calc-alkaline magmas contaminated with metasedimentary rocks that had upper-crust signature (high U, Cs, Ta). The mafic-rich peraluminous granites show a more evolved isotope signature (87Sr/86Sr(t) = 0.713-0.714; epsilonNd(t) = -14 to -16), similar to Bmg, and Mg# and incompatible trace-element concentrations intermediate between Bmg and BmgT. A model is presented in whichMBmgis envisaged as the product of contamination between a mafic mineral-rich magma consanguineous with BmgT and pure crustal melts akin to Bmg.

  15. Geochemical and Sr-Nd isotopic characteristics of mantle xenoliths from NE Spain

    NASA Astrophysics Data System (ADS)

    Galán, G.; Oliveras, V.

    2012-04-01

    Mantle xenoliths in alkaline mafic lavas and pyroclasts from the Neogene-Quaternary volcanism in NE Spain are studied using major, trace element geochemistry and Sr-Nd isotopes, to compare the lithospheric mantle of this area with that of other European zones, and to assess the different processes that conditioned its evolution. The xenoliths mostly come from two volcanoes and are mainly formed of anhydrous spinel lherzolites and harzburgites, in approximately equal proportion. Accessory amphibole and phlogopite are occasional, as it happens with plagioclase, which appears in corona textures around lherzolite spinel. Much subordinated cumulate pyroxenite xenoliths (olivine wbsterite, clinopyroxenite types) are also found. Textures are mostly protogranular, but there are also porphyroclastic, transitional between protogranular and porphyroclastic, and equigranular forms among lherzolites. Pyrometamorphic textures are observed in a few xenoliths. Co-variation diagrams for basaltic components and MgO concentrations in whole rock analyses show gradation from lherzolites to harzburgites. This is also the case for compatible and mildly incompatible trace elements, but not for the most incompatible ones. This gradual variation is also confirmed by mineral compositions, most of which correspond to off-craton xenoliths. REE patterns for lherzolites and for their clinopyroxene are LREE and MREE depleted, whereas for harzburgites are LREE and MREE enriched. U-shaped REE patterns are rarely observed in lherzolite clinopyroxene that also shows more significant negative anomalies at Zr and Ti. Clinopyroxene from harzburgites is also remarked by more significant negative anomalies at Nb, Ti and Zr, and by higher Th and U abundances, than lherzolite clinopyroxene . Sr and Nd isotopic compositions for clinopyroxene define a continuous and inverse trend from DMM lherzolites to enriched harzburgites (87Sr/86Sr: 0.702486-0.709772; 143Nd/144Nd: 0.513359-0.512411). Harzburgite

  16. Origin and Dynamics of Rare Earth Elements during Flood Events in Contaminated River Basins: Sr-Nd-Pb Isotopic Evidence.

    PubMed

    Hissler, Christophe; Stille, Peter; Iffly, Jean François; Guignard, Cédric; Chabaux, François; Pfister, Laurent

    2016-05-01

    In order to precisely quantify the contribution of anthropogenic activities and geogenic sources to the dissolved and suspended loads of rivers we have combined for the first time Rare Earth Element (REE) concentrations with Sr-Nd-Pb isotope ratios. We observed enrichments in Anthropogenic Rare Earth Elements (AREE) for dissolved (Gd) and suspended (Ce and Nd) loads of river water. During flood events, AREE anomalies progressively disappeared and gave way to the geogenic chemical signature of the basin in both dissolved and suspended loads. The isotopic data confirm these observations and shed new light on the trace elements sources. On the one hand, dissolved loads have peculiar isotopic characteristics and carry mainly limestone-derived and anthropogenic Sr and Nd as well as significant amounts of anthropogenic Pb. On the other hand, the results clearly indicate that anthropogenic contributions impact the suspended loads in all hydrological conditions. This study demonstrates that anthropogenic contributions to the river may change not only Pb but also Sr and Nd isotopic compositions in both dissolved and suspended loads. This is of importance for future provenance studies. PMID:27045616

  17. Origin and Dynamics of Rare Earth Elements during Flood Events in Contaminated River Basins: Sr-Nd-Pb Isotopic Evidence.

    PubMed

    Hissler, Christophe; Stille, Peter; Iffly, Jean François; Guignard, Cédric; Chabaux, François; Pfister, Laurent

    2016-05-01

    In order to precisely quantify the contribution of anthropogenic activities and geogenic sources to the dissolved and suspended loads of rivers we have combined for the first time Rare Earth Element (REE) concentrations with Sr-Nd-Pb isotope ratios. We observed enrichments in Anthropogenic Rare Earth Elements (AREE) for dissolved (Gd) and suspended (Ce and Nd) loads of river water. During flood events, AREE anomalies progressively disappeared and gave way to the geogenic chemical signature of the basin in both dissolved and suspended loads. The isotopic data confirm these observations and shed new light on the trace elements sources. On the one hand, dissolved loads have peculiar isotopic characteristics and carry mainly limestone-derived and anthropogenic Sr and Nd as well as significant amounts of anthropogenic Pb. On the other hand, the results clearly indicate that anthropogenic contributions impact the suspended loads in all hydrological conditions. This study demonstrates that anthropogenic contributions to the river may change not only Pb but also Sr and Nd isotopic compositions in both dissolved and suspended loads. This is of importance for future provenance studies.

  18. Sr-Nd isotope geology and tectonomagmatic setting of the Dehsalm intrusives (Lut Block, Eastern Iran)

    NASA Astrophysics Data System (ADS)

    Arjmandzadeh, Reza; Francisco Santos, Jose; Ribeiro, Sara

    2013-04-01

    compositions together with major and trace element geochemistry point to the origin of the parental magmas by melting of a metasomatized mantle source, with garnet behaving as a residual phase, whilst phlogopite was an important contributor to the generated melts. Both geochemical features of Dehsalm porphyries and its association with Cu-Mo mineralization agree with a mature continental arc setting related to the convergence of Afghan and Lut plates during Oligocene. The data on the Dehsalm granitoids reveal a strong affinity with the contemporary rocks from Chah-Shaljami, studied in a previous work (Arjmandzadeh et al., 2011). Moreover, the wider range of compositions (including more mafic compositions) at Dehsalm provides additional support for the suggestion that parental magmas have a mantle origin. Acknowledgements This research was financially supported by the Geobiotec Research Unit (funded by the Portuguese Foundation for Science and Technology, through project PEst-C/CTE/UI4035/2011), University of Aveiro, Portugal. Ministry of Sciences, Research and Technology of Iran granted a sabbatical scholarship of R. Arjmandzadeh in Portugal References Arjmandzadeh, R., Karimpour, M.H., Mazaheri, S.A., Santos, J.F., Medina, J., Homam, S.M., 2011. Sr-Nd isotope geochemistry and petrogenesis of the Chah-Shaljami granitoids (Lut Block, Eastern Iran). Journal of Asian Earth Sciences 41: p. 283-296. Arjmandzadeh, R., Karimpour, M.H., Mazaheri, S.A., Santos, J.F., Medina, J., Homam, S.M., 2012. Petrogenesis, tectonomagmatic setting and mineralization potential of Dehsalm granitoids, Lut block, Eastern Iran. Journal of Earth Sciences, accepted.

  19. Uranium-Lead Zircon Ages and Sr, Nd, and Pb Isotope Geochemistry of Selected Plutonic Rocks from Western Idaho

    USGS Publications Warehouse

    Unruh, Daniel M.; Lund, Karen; Kuntz, Mel A.; Snee, Lawrence W.

    2008-01-01

    Across the Salmon River suture in western Idaho, where allochthonous Permian to Cretaceous oceanic rocks are juxtaposed against Proterozoic North American rocks, a wide variety of plutonic rocks are exposed. Available data indicate much variation in composition, source, and structural state of these plutons. The plutonic rocks were long described as the western border zone of the Cretaceous Idaho batholith but limited pre-existing age data indicate more complicated origins. Because the affinity and age of the plutonic rocks cannot be reliably determined from field relations, TIMS U-Pb dating in conjunction with Sr, Nd, and Pb isotopic studies of selected plutons across the suture in western Idaho were undertaken. The data indicate three general groups of plutons including (1) those that intruded the island arc terranes during the Triassic and Jurassic, those that intruded near the western edge of oceanic rocks along the suture in the Early Cretaceous, and the plutons of the Idaho batholith that intruded Proterozoic North American rocks in the Late Cretaceous. Plutons that intruded Proterozoic North American rocks commonly include xenocrystic zircons and in several cases, ages could not be determined. The least radiogenic Sr and most radiogenic Nd are found among the Blue Mountains superterrane island arc samples. Suture-zone plutons have isotopic characteristics that span the range between Idaho batholith and island arc samples but mostly follow island arc signatures. Plutons of the Idaho batholith have the most radiogenic initial Pb and Sr ratios and the least radiogenic Nd of the samples analyzed.

  20. Os, Sr, Nd, and Pb isotope systematics of southern African peridotite xenoliths - Implications for the chemical evolution of subcontinental mantle

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Carlson, R. W.; Shirey, S. B.; Boyd, F. R.

    1989-01-01

    Isotope analyses of Os, Sr, Nd, and Pb elements were caried out on twelve peridotite xenoliths from the Jagersfontein, Letseng-la-terae, Thaba Patsoa, Mothae, and Premier kimberlites of southern Africa, to investigate the timing and the nature of melt extraction from the continental lithosphere and its relation to the continent formation and stabilization. The distinct Os and Pb isotopic characteristics found in these samples suggested that both the low- and the high-temperature peridotites reside in an ancient stable lithospheric 'keel' to the craton that has been isolated from chemical exchange with the sublithospheric mantle for time periods in excess of 2 Ga.

  1. Mixed fluid sources involved in diamond growth constrained by Sr-Nd-Pb-C-N isotopes and trace elements

    NASA Astrophysics Data System (ADS)

    Klein-BenDavid, Ofra; Pearson, D. Graham; Nowell, Geoff M.; Ottley, Chris; McNeill, John C. R.; Cartigny, Pierre

    2010-01-01

    Sub-micrometer inclusions in diamonds carry high-density fluids (HDF) from which the host diamonds have precipitated. The chemistry of these fluids is our best opportunity of characterizing the diamond-forming environment. The trace element patterns of diamond fluids vary within a limited range and are similar to those of carbonatitic/kimberlitic melts that originate from beneath the lithospheric mantle. A convecting mantle origin for the fluid is also implied by C isotopic compositions and by a preliminary Sr isotopic study (Akagi, T., Masuda, A., 1988. Isotopic and elemental evidence for a relationship between kimberlite and Zaire cubic diamonds. Nature 336, 665-667.). Nevertheless, the major element chemistry of HDFs is very different from that of kimberlites and carbonatites, varying widely and being characterized by extreme K enrichment (up to ˜ 39 wt.% on a water and carbonate free basis) and high volatile contents. The broad spectrum of major element compositions in diamond-forming fluids has been related to fluid-rock interaction and to immiscibility processes. Elemental signatures can be easily modified by a variety of mantle processes whereas radiogenic isotopes give a clear fingerprint of the time-integrated evolution of the fluid source region. Here we present the results of the first multi radiogenic-isotope (Sr, Nd, Pb) and trace element study on fluid-rich diamonds, implemented using a newly developed off-line laser sampling technique. The data are combined with N and C isotope analysis of the diamond matrix to better understand the possible sources of fluid involved in the formation of these diamonds. Sr isotope ratios vary significantly within single diamonds. The highly varied but unsupported Sr isotope ratios cannot be explained by immiscibility processes or fluid-mineral elemental fractionations occurring at the time of diamond growth. Our results demonstrate the clear involvement of a mixed fluid, with one component originating from ancient

  2. Origin of Eclogites from the Sanbagawa Metamorphic Belt, Southwestern Japan: Geochemical and Sr-Nd Isotopic Evidence

    NASA Astrophysics Data System (ADS)

    Utsunomiya, Atsushi; Jahn, Bor-Ming; Okamoto, Kazuaki; Ota, Tsutomu; Shinjoe, Hironao

    2010-05-01

    The Sanbagawa belt is a celebrated Cretaceous high-P/T metamorphic belt occurring in SW Japan. Although most metamorphic rocks from the Sanbagawa belt are non-eclogitic, several eclogite-facies metagabbro bodies are exposed in the Besshi area of the Shikoku island. These bodies were earlier recognized as tectonic blocks derived from the lower crust of the former hanging wall (= mantle wedge) in the subduction zone (Takasu et al., 1994). However, more recent studies of field occurrence and metamorphic petrology led to a suggestion that these bodies represent subducted oceanic materials along with their surrounding schists, but not tectonic blocks from mantle wedge (Ota et al., 2004; Terabayashi et al., 2005; Aoya et al., 2006). Furthermore, the protoliths of these eclogites were considered to have formed in a seamount (Aoya et al., 2006) or an oceanic plateau (Terabayashi et al., 2005). In this study, we aim to resolve the controversy about the protoliths and tectonic setting of eclogites and associated rocks using geochemical and Sr-Nd isotopic tracer techniques. All samples were collected from the Iratsu body, the best exposure of eclogitic rocks in the Besshi area. Eclogites, garnet clinopyroxenites and garnet amphibolites from the Iratsu body have flat to LREE-enriched REE patterns, and show Nb and Zr-Hf depletion in the conventional spidergrams. They have Sr-Nd isotopic characteristics of OIB (epsilon Nd (t) = -1 - +4), hence are different from the surrounding mafic schists which are akin to MORB. The overall geochemical and isotopic signatures suggest that the protoliths of the Iratsu body formed in a subduction setting and were produced by melting of mixed sources between a depleted and an enriched mantle components. The geochemical feature of garnet clinopyroxenites (strong Zr-Hf depletion and Ti enrichment) may be explained by accumulation of clinopyroxene + plagioclase + magnetite. A relevant experimental study indicates that the mineral assemblage

  3. Provenances of atmospheric dust over Korea from Sr-Nd isotopes and rare earth elements in early 2006

    NASA Astrophysics Data System (ADS)

    Lee, Min Kyung; Lee, Yong Il; Yi, Hi-Il

    2010-07-01

    Sr and Nd isotopic composition of pre- and syn-Asian dust (Hwangsa) particles collected from three different water depths at two different offshore sites, western Korea and rare earth elemental composition of syn-Asian dust particles collected from three islands around the Korean Peninsula in late April 2006 were analyzed to interpret their provenance. The dust Sr-Nd isotopic compositions vary spatiotemporally, but they show specific values when the Hwangsa event occurred. Satellite images, airmass backward trajectory modeling, and comparison with Sr-Nd isotopic ratios and rare earth elements compositions of soils and desert sands of northern China all suggest the major source of dust particles for the late April 2006 Hwangsa event to be the Mu Us Desert in northern China. Dust particles of the pre-Hwangsa period include both background dusts and the previous Hwangsa event dust particles, and they are interpreted to have been originated from various arid regions of China such as the Hobq Desert, the Mu Us Desert, and the Taklamakan Desert in different times. Different background dust sources during pre-Hwangsa period in early 2006 resulted from the changing route of the westerlies.

  4. Comparative behavior of Sr, Nd and Hf isotopic systems during fluid-related deformation at middle crust levels

    NASA Astrophysics Data System (ADS)

    Luais, Béatrice; Le Carlier de Veslud, Christian; Géraud, Yves; Gauthier-Lafaye, François

    2009-05-01

    We have carried out a comparative Rb-Sr, Sm-Nd and Lu-Hf isotopic study of a progressively deformed hercynian leucogranite from the French Massif Central, belonging to the La Marche ductile shear zone, in order to investigate the respective perturbation of these geochronometers with fluid induced deformation. The one-meter wide outcrop presents a strongly deformed and mylonitized zone at the center, and an asymmetric deformation pattern with a higher deformation gradient on the northern side of the zone. Ten samples have been carefully collected every 10 cm North and South away from the strongest deformed mylonitic zone. They have been analyzed for a complete major, trace element data set, oxygen isotopes, Rb-Sr, Sm-Nd and Lu-Hf isotopic systematics. We show that most of major and trace elements except SiO 2, alkaline elements (K 2O, Rb), and some metal transition elements (Cu), are progressively depleted with increasing deformation. This depletion includes REE + Y, but also HFS elements (Ti, Hf, Zr, Nb) which are commonly considered as immobile elements during upper level processes. Variations in elemental ratios with deformation, e.g. decrease in LREE/MREE- HREE, Nd/Hf, Th/Sr, increase in Rb/Sr, U/Th and constant Sr/Nd, lead to propose the following order of element mobility: U ≫ Th > Sr = Nd ≫ Hf + HREE. We conclude in agreement with previous tectonic and metallogenic studies that trace element patterns across the shear zone result from circulation of oxidizing F-rich hydrothermal fluids associated with deformation. A temperature of the fluid of 470-480 °C can be deduced from the δ 18O equilibrium between quartz-muscovite pairs. Elemental fractionation induces perturbation of the Rb-Sr geochronometer. The well-defined 87Rb/ 86Sr- 87Sr/ 86Sr correlation gives an apparent age of 294 ± 19 Ma, slightly younger than the 323 ± 4 Ma age of leucogranites in this area. This apparent age is interpreted as dating event of intense deformation and fluid circulation

  5. Sr-Nd-Hf-Pb isotopic constraints on the origin of silicic lavas in the northern Cascade Arc

    NASA Astrophysics Data System (ADS)

    Martindale, M.; Mullen, E.; Weis, D.

    2015-12-01

    The Cascade Arc is the type-locality for a 'hot' subduction zone, where the downgoing slab is young and subduction is relatively slow; a unique setting for studying the controls on silicic (>56 wt% SiO2) magma genesis [1,2]. We present high precision Sr-Nd-Hf-Pb isotopic and trace element data for silicic lavas and country rocks from the major centres of the Garibaldi Volcanic Belt (GVB) in British Columbia, which are hosted by the Mesozoic Coast Plutonic Complex and accreted Coast Belt terranes. In isotopic plots, the silicic GVB lavas define mixing curves between northern Cascadia Basin sediment [3] and Juan de Fuca MORB. The silicic GVB lavas have lower ɛNd, and higher ɛHf, 87Sr/86Sr, 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb than co-existing alkalic mafic lavas [2,4] which define a separate isotopic cluster. The alkalic mafic lavas have OIB-like trace element compositions [2,4], but the silicic lavas are calc-alkaline with a typical 'arc' trace element signature. Geochemical systematics suggest that a mafic, isotopically 'depleted' contaminant may be affecting the composition of GVB silicic lavas. However, modelling indicates that slab melts do not constitute a major component of the lavas despite high slab temperatures. Geochemical models also rule out the accreted Coast Belt terranes as an assimilant. However, AFC modelling using 147 Ma Cloudburst quartz diorite [5] as the assimilant can explain both the trace element and isotopic compositional range displayed by GVB silicic magmas, consistent with the Coast Plutonic Complex as a major component of the deep crust in this region. Crustal assimilation would have partially overprinted any alkalic mantle-derived signature of parental magmas, while imparting a calc-alkaline arc signature to resulting silicic magmas. [1] Green & Harry (1999) EPSL, 171; [2] Mullen & Weis (2013) G3, 14; [3] Carpentier et al. (2014) Chem Geol, 382; [4] Mullen & Weis (2015) EPSL, 414; [5] Friedman & Armstrong (1995) GSA

  6. Sr-Nd-Pb-Hf isotope systematics of the Hugo Dummett Cu-Au porphyry deposit (Oyu Tolgoi, Mongolia)

    NASA Astrophysics Data System (ADS)

    Dolgopolova, A.; Seltmann, R.; Armstrong, R.; Belousova, E.; Pankhurst, R. J.; Kavalieris, I.

    2013-04-01

    Major and trace element geochemistry including Sr-Nd-Pb-Hf isotopic data are presented for a representative sample suite of Late Devonian to Early Carboniferous plutonic and volcanic rocks from the Hugo Dummett deposit of the giant Oyu Tolgoi porphyry Cu-Au district in South Gobi, Mongolia. Sr and Nd isotopes (whole-rock) show restricted ranges of initial compositions, with positive ɛNdt mainly between + 3.4 and + 7.4 and (87Sr/86Sr)t predominantly between 0.7037 and 0.7045 reflecting magma generation from a relatively uniform juvenile lithophile-element depleted source. Previously dated zircons from the plutonic rocks exhibit a sample-averaged range of ɛHft values of + 11.6 to + 14.5. Depleted-mantle model ages of 420-830 (Nd) and 320-730 Ma (zircon Hf) limit the involvement of pre-Neoproterozoic crust in the petrogenesis of the intermediate to felsic calc-alkaline magmas to, at most, a minor role. Pb isotopes (whole-rock) show a narrow range of unradiogenic initial compositions: 206Pb/204Pb 17.40-17.94, 207Pb/204Pb 15.43-15.49 and 208Pb/204Pb 37.25-37.64, in agreement with Sr-Nd-Hf isotopes indicating the dominance of a mantle component. All four isotopic systems suggest that the magmas from which the large Oyu Tolgoi porphyry system was generated originated predominantly from juvenile material within the subduction-related setting of the Gurvansayhan terrane.

  7. Melt extraction and enrichment processes in the New Caledonia lherzolites: Evidence from geochemical and Sr-Nd isotope data

    NASA Astrophysics Data System (ADS)

    Secchiari, Arianna; Montanini, Alessandra; Bosch, Delphine; Macera, Patrizia; Cluzel, Dominique

    2016-09-01

    The New Caledonia ophiolite (Peridotite Nappe) is dominated by mantle lithologies, composed of forearc-related refractory harzburgites and minor lherzolites in both the spinel and plagioclase facies. In this study, a comprehensive geochemical data set (major, trace elements and Sr-Nd isotopes) is used to constrain the mantle evolution of the lherzolites and their relationships with the basalts from the Poya Terrane, which tectonically underlies the mantle rocks. The majority of the lherzolites are low-strain porphyroclastic tectonites. They likely record an asthenospheric origin followed by re-equilibration at lithospheric conditions, as supported by geothermometric estimates (T = 1100-940 °C and 920-890 °C for porphyroclastic and neoblastic spinel-facies assemblages, respectively). Olivine composition (Fo = 88.5-90.0 mol%), spinel Cr# ([molar 100 • Cr/(Cr + Al)] = 13-17) and relatively high amounts (7-8 vol%) of Al2O3- and Na2O-rich clinopyroxene (up to 0.5 and 6.5 wt.%, respectively) indicate a moderately depleted geochemical signature for the spinel lherzolites. Bulk rock and clinopyroxene rare earth elements (REE) patterns display a typical abyssal-type signature, i.e. steeply plunging LREE accompanied by nearly flat HREE to MREE. Clinopyroxene REE compositions of the spinel lherzolites may be reproduced by small amounts of fractional melting of a garnet lherzolite precursor (~ 4%), followed by 4%-5% melting in the spinel peridotite field. The plagioclase lherzolites show melt impregnation microstructures, Cr- and Ti-rich spinels and incompatible trace element enrichments (REE, Ti, Y, and Zr) in bulk rocks and clinopyroxenes. Impregnation modelling for these elements suggests that the plagioclase lherzolites originated from residual spinel lherzolites by entrapment of highly depleted (non-aggregated) MORB melt fractions in the shallow oceanic lithosphere. Nd isotope compositions of the investigated peridotites are consistent with derivation from an

  8. The suitability of annual tree growth rings as environmental archives: Evidence from Sr, Nd, Pb and Ca isotopes in spruce growth rings from the Strengbach watershed

    NASA Astrophysics Data System (ADS)

    Stille, Peter; Schmitt, Anne-Désirée; Labolle, François; Pierret, Marie-Claire; Gangloff, Sophie; Cobert, Florian; Lucot, Eric; Guéguen, Florence; Brioschi, Laure; Steinmann, Marc; Chabaux, François

    2012-05-01

    The combination of the Sr, Nd and Pb isotope systems, recognized as tracers of sources, with the Ca isotope system, known to reveal biology-related fractionations, allowed us to test the reliability of spruce (Picea abies) growth rings as environmental archives through time (from 1916 to 1983) in a forest ecosystem affected by acid atmospheric deposition. Sr and Pb isotopes have already been applied in former tree-ring studies, whereas the suitability of Nd and Ca isotope systems is checked in the present article. Our Sr and Nd isotope data indicate an evolution in the cation origin with a geogenic origin for the oldest rings and an atmospheric origin for the youngest rings. Ca isotopes show, for their part, an isotopic homogeneity which could be linked to the very low weathering flux of Ca. Since this flux is weak the spruces' root systems have pumped the Ca mainly from the organic matter-rich top-soil over the past century. In contrast, the annual growth rings studied are not reliable and suitable archives of past Pb pollution.

  9. Pervasive Crustal Melting on a Regional Scale: Sr-Nd Isotopic Evidence from Eocene Intrusions in NE Washington

    NASA Astrophysics Data System (ADS)

    Loewen, M. W.; Tepper, J. H.; Asmerom, Y.

    2007-12-01

    of Proterozoic arc crust (Morris 2000). Geographic variability in Sr-Nd data indicates that isotopically distinct crustal domains are juxtaposed laterally and/or vertically, in some cases on a small scale. The sample with the highest 87Sr/86Srm (0.7262; ɛNdm = -13.3) is a dacite porphyry well west of the 0.706 line, while at Porcupine Bay adjacent plutons differ by almost 10 ɛNd units (-7.4 and 2.2). Ongoing work is designed to further characterize the crustal sources and better understand the nature of the thermotectonic event that drove such widespread crustal melting.

  10. Comprehensive Pb-Sr-Nd-Hf isotopic, trace element, and mineralogical characterization of mafic to ultramafic rock reference materials

    NASA Astrophysics Data System (ADS)

    Fourny, Anaïs.; Weis, Dominique; Scoates, James S.

    2016-03-01

    Controlling the accuracy and precision of geochemical analyses requires the use of characterized reference materials with matrices similar to those of the unknown samples being analyzed. We report a comprehensive Pb-Sr-Nd-Hf isotopic and trace element concentration data set, combined with quantitative phase analysis by XRD Rietveld refinement, for a wide range of mafic to ultramafic rock reference materials analyzed at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. The samples include a pyroxenite (NIM-P), five basalts (BHVO-2, BIR-1a, JB-3, BE-N, GSR-3), a diabase (W-2), a dolerite (DNC-1), a norite (NIM-N), and an anorthosite (AN-G); results from a leucogabbro (Stillwater) are also reported. Individual isotopic ratios determined by MC-ICP-MS and TIMS, and multielement analyses by HR-ICP-MS are reported with 4-12 complete analytical duplicates for each sample. The basaltic reference materials have coherent Sr and Nd isotopic ratios with external precision below 50 ppm (2SD) and below 100 ppm for Hf isotopes (except BIR-1a). For Pb isotopic reproducibility, several of the basalts (JB-3, BHVO-2) require acid leaching prior to dissolution. The plutonic reference materials also have coherent Sr and Nd isotopic ratios (<50 ppm), however, obtaining good reproducibility for Pb and Hf isotopic ratios is more challenging for NIM-P, NIM-N, and AN-G due to a variety of factors, including postcrystallization Pb mobility and the presence of accessory zircon. Collectively, these results form a comprehensive new database that can be used by the geochemical community for evaluating the radiogenic isotope and trace element compositions of volcanic and plutonic mafic-ultramafic rocks.

  11. Major, trace element and isotope geochemistry (Sr-Nd-Pb) of interplinian magmas from Mt. Somma-Vesuvius (Southern Italy)

    USGS Publications Warehouse

    Somma, R.; Ayuso, R.A.; de Vivo, B.; Rolandi, G.

    2001-01-01

    Major, trace element and isotopic (Sr, Nd, Pb) data are reported for representative samples of interplinian (Protohistoric, Ancient Historic and Medieval Formations) activity of Mt. Somma-Vesuvius volcano during the last 3500 years. Tephra and lavas exhibit significant major, trace element and isotopic variations. Integration of these data with those obtained by previous studies on the older Somma suites and on the latest activity, allows to better trace a complete petrological and geochemical evolution of the Mt. Somma-Vesuvius magmatism. Three main groups of rocks are recognized. A first group is older than 12.000 yrs, and includes effusive-explosive activity of Mt. Somma. The second group (8000-2700 yrs B.P.) includes the products emitted by the Ottaviano (8000 yrs. B.P.) and Avellino (3550 yrs B.P.) plinian eruptions and the interplinian activity associated with the Protohistoric Formation. Ancient Historic Formation (79-472 A.D.), Medieval Formation (472-1139 A.D.) and Recent interplinian activity (1631-1944 A.D.) belong to the third group of activity (79-1944 A.D.). The three groups of rocks display distinct positive trends of alkalis vs. silica, which become increasingly steeper with age. In the first group there is an increase in silica and alkalis with time, whereas an opposite tendency is observed in the two younger groups. Systematic variations are also evident among the incompatible (Pb, Zr, Hf, Ta, Th, U, Nb, Rb, Cs, Ba) and compatible elements (Sr, Co, Cr). REE document variable degrees of fractionation, with recent activity displaying higher La/Yb ratios than Medieval and Ancient Historic products with the same degree of evolution. N-MORB normalized multi-element diagrams for interplinian rocks show enrichment in Rb, Th, Nb, Zr and Sm (> *10 N-MORB). Sr isotope ratios are variable, with Protohistoric rocks displaying 87Sr/86Sr= 0.70711-0.70810, Ancient Historic 87Sr/86Sr=0.70665-0.70729, and Medieval 87Sr/86Sr=0.70685-0.70803. Neodymium isotopic

  12. Origin of enormous trace metal enrichments in weathering mantles of Jurassic carbonates: evidence from Sr, Nd and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Hissler, C.; Stille, P.; Juilleret, J.; Iffly, J.; Perrone, T.; Morvan, G.

    2013-12-01

    Weathering mantels are widespread worldwide and include lateritic, sandy and kaolinite-rich saprolites and residuals of partially dissolved carbonate rocks. These old regolith systems have a complex history of formation and may present a polycyclic evolution due to successive geological and pedogenetic processes that affected the profile. Until now, only few studies highlighted the unusual content of associated trace elements in this type of weathering mantle. For instance, these enrichments can represent about five times the content of the underlying Bajocian to Oxfordian limestone/marl complexes, which have been relatively poorly studied compared to weathering mantle developed on magmatic bedrocks. Up to now, neither soil, nor saprolite formation has to our knowledge been geochemically elucidated. Therefore, the aim of this study was to examine more closely the soil forming dynamics and the relationship of the chemical soil composition to potential sources (saprolite, Bajocian silty marls and limestones, atmospheric particles deposition...). Of special interest has also been the origin of trace metals and the processes causing their enrichments. Especially Rare Earth Element (REE) distribution patterns and Sr, Nd and Pb isotope ratios are particularly well suited to identify trace element migration, to recognize origin and mixing processes and, in addition, to decipher possible anthropogenic and/or "natural" atmosphere-derived contributions to the soil. Moreover, leaching experiments shall help to identify mobile phases in the soil system. This may inform on the stability of trace elements and especially on their behaviour in these Fe-enriched carbonate systems. Trace metal migration and enrichments were studied on a cambisol developing on an underlying Jurassic limestone. The base is strongly enriched among others in rare earth elements (ΣREE: 2640ppm) or redox-sensitive elements such as Fe (44 wt.%), V (920ppm), Cr (700ppm), Zn (550ppm), As (260ppm), Co (45ppm

  13. Geochemical and Sr Nd Pb isotopic evidence for a combined assimilation and fractional crystallisation process for volcanic rocks from the Huichapan caldera, Hidalgo, Mexico

    NASA Astrophysics Data System (ADS)

    Verma, Surendra P.

    2001-03-01

    This study reports new geochemical and Sr-Nd-Pb isotopic data for Miocene to Quaternary basaltic to andesitic, dacitic, and rhyolitic volcanic rocks from the Huichapan caldera, located in the central part of the Mexican Volcanic Belt (MVB). The initial Sr and Nd isotopic ratios, except for one rhyolite, range as follows: 87Sr/ 86Sr 0.70357-0.70498 and 143Nd/ 144Nd 0.51265-0.51282. The Sr-Nd-Pb isotopic ratios are generally similar to those for volcanic rocks from other areas of the central and eastern parts of the MVB. The isotopic ratios of one older pre-caldera rhyolite (HP30) from the Huichapan area, particularly its high 87Sr/ 86Sr, are significantly different from rhyolitic rocks from this and other areas of the MVB, but are isotopically similar to some felsic rocks from the neighbouring geological province of Sierra Madre Occidental (SMO), implying an origin as a partial melt of the underlying crust. The evolved andesitic to rhyolitic magmas could have originated from a basaltic magma through a combined assimilation and fractional crystallisation (AFC) process. Different compositions, representing lower crust (LC) and upper crust (UC) as well as a hypothetical crust similar to the source of high 87Sr/ 86Sr rhyolite HP30, were tested as plausible assimilants for the AFC process. The results show that the UC represented by granitic rocks from a nearby Los Humeros area or by Cretaceous limestone (L) rocks outcropping in the northern part of the study area, and the LC represented by granulitic xenoliths from a nearby San Luis Potosı´ (SLP) area are not possible assimilants for Huichapan magmas, whereas a hypothetical crust (HA) similar in isotopic compositions to rhyolite HP30 could be considered a possible assimilant for the AFC process. Chemical composition of assimilant HA, although not well constrained at present, was inferred under the assumption that HP30 type partial melts could be generated from its partial melting. These data were then used to evaluate

  14. Isotope geochemistry of recent magmatism in the Aegean arc: Sr, Nd, Hf, and O isotopic ratios in the lavas of Milos and Santorini-geodynamic implications

    USGS Publications Warehouse

    Briqueu, L.; Javoy, M.; Lancelot, J.R.; Tatsumoto, M.

    1986-01-01

    In this comparative study of variations in the isotopic compositions (Sr, Nd, O and Hf) of the calc-alkaline magmas of the largest two volcanoes, Milos and Santorini, of the Aegean arc (eastern Mediterranean) we demonstrate the complexity of the processes governing the evolution of the magmas on the scale both of the arc and of each volcano. On Santorini, the crustal contamination processes have been limited, effecting the magma gradually during its differentiation. The most differentiated lavas (rhyodacite and pumice) are also the most contaminated. On Milos, by contrast, these processes are very extensive. They are expressed in the 143Nd/144Nd vs. 87Sr/86Sr diagram as a continuous mixing curve between a mantle and a crustal end member pole defined by schists and metavolcanic rocks outcropping on these volcanoes. In contrast with Santorini, the least differentiated lavas on Milos are the most contaminated. These isotopic singularities can be correlated with the geodynamic evolution of the Aegean subduction zone, consisting of alternating tectonic phases of distension and compression. The genesis of rhyolitic magmas can be linked to the two phases of distension, and the contamination of the calc-alkaline mantle-derived magmas with the intermediate compressive phase. The isotopic characteristics of uncontaminated calc-alkaline primitive magmas of Milos and Santorini are directly comparable to those of magmas generated in subduction zones for which a contribution of subducted sediments to partial melts from the mantle is suggested, such as in the Aleutian, Sunda, and lesser Antilles island arcs. However, in spite of the importance of the sediment pile in the eastern Mediterranen oceanic crust (6-10 km), the contribution of the subducted terrigenous materials remains of limited amplitude. ?? 1986.

  15. Geochemical and Sr-Nd-Pb isotopic evidence for ancient lower continental crust beneath the Xi Ujimqin area of NE China

    NASA Astrophysics Data System (ADS)

    Gao, Xiaofeng; Guo, Feng; Xiao, Peixi; Kang, Lei; Xi, Rengang

    2016-05-01

    The Central Asian Orogenic Belt (CAOB) is the largest Phanerozoic accretionary orogen on Earth. The role that Precambrian continental microblocks played in its formation, however, remains a highly controversial topic. New zircon U-Pb age data and whole-rock geochemical and Sr-Nd-Pb isotopic studies on Permian (253-251 Ma) andesites from the Xi Ujimqin area provide the first evidence for the existence of a continental lower mafic crust in the eastern segment of the CAOB. These Permian lavas generally have chemical compositions similar to experimental melts of garnet pyroxenites. Based on Sr-Nd-Pb isotopic compositional differences, they can be further subdivided into two groups. Group 1 has moderately radiogenic Sr (87Sr/86Sr(i) = 0.7060-0.7062) and nonradiogenic Nd (εNd(t) = - 9.0-8.3) and Pb (e.g., 206Pb/204Pb = 17.18-17.23) isotopic compositions similar to the ancient lower mafic crust beneath the North China Craton (NCC). Compared with Group 1, Group 2 has less radiogenic Sr (87Sr/86Sr(i) = 0.7051-0.7055), and more radiogenic Nd (εNd(t) = - 0.2-+1.4) and Pb (e.g., 206Pb/204Pb = 18.04-18.20) isotopic compositions as observed in the Phanerozoic granitoids and felsic lavas of the CAOB. The combined geochemical and isotopic data indicate that Group 1 was derived from ancient lower mafic crust of the NCC affinity, with a residual assemblage of pyroxene + plagioclase + amphibole. The source for Group 2 was a mixture of ancient lower mafic crust and a juvenile crustal component, and melting left a residue of orthopyroxene + clinopyroxene + plagioclase + garnet + amphibole. Generation of these two types of late Permian andesites favors a model whereby breakoff of a subducted slab and subsequent lithospheric extension triggered extensive asthenospheric upwelling and melting of the continental mafic lower crust of the eastern CAOB. The discovery of ancient lower continental crust of the NCC affinity in the CAOB implies that the NCC experienced continental breakup during

  16. Stages of weathering mantle formation from carbonate rocks in the light of rare earth elements (REE) and Sr-Nd-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Hissler, Christophe; Stille, Peter

    2015-04-01

    Weathering mantles are widespread and include lateritic, sandy and kaolinite-rich saprolites and residuals of partially dissolved rocks. These old regolith systems have a complex history of formation and may present a polycyclic evolution due to successive geological and pedogenetic processes that affected the profile. Until now, only few studies highlighted the unusual high content of associated trace elements in weathering mantles originating from carbonate rocks, which have been poorly studied, compared to those developing on magmatic bedrocks. For instance, these enrichments can be up to five times the content of the underlying carbonate rocks. However, these studies also showed that the carbonate bedrock content only partially explains the soil enrichment for all the considered major and trace elements. Up to now, neither soil, nor saprolite formation has to our knowledge been geochemically elucidated. Therefore, the aim of this study was to examine more closely the soil forming dynamics and the relationship of the chemical soil composition to potential sources. REE distribution patterns and Sr-Nd-Pb isotope ratios have been used because they are particularly well suited to identify trace element migration, to recognize origin and mixing processes and, in addition, to decipher possible anthropogenic and/or "natural" atmosphere-derived contributions to the soil. Moreover, leaching experiments have been applied to identify mobile phases in the soil system and to yield information on the stability of trace elements and especially on their behaviour in these Fe-enriched carbonate systems. All these geochemical informations indicate that the cambisol developing on such a typical weathering mantle ("terra fusca") has been formed through weathering of a condensed Bajocian limestone-marl facies. This facies shows compared to average world carbonates important trace element enrichments. Their trace element distribution patterns are similar to those of the soil

  17. REE and Sr, Nd, Pb isotopic geochemistry of Huangyishan basalt, Kuandian, Liaoning, Northeast China

    USGS Publications Warehouse

    Xie, G.-h.; Wang, J.-w.; Wei, K.-j.; Liu, C.-q.; Tatsumoto, M.; Basn, A.R.

    1990-01-01

    In the light of major element geochemistry, mineral chemistry and REE and isotopic data, the small but apparent isotopic differences between the Cenozoic volcanic rocks east and west of the Tancheng-Lujiang fault are believed to be caused by the mixing and metasomatism of crustal and mantle material in the mantle source region in response to Pacific plate subduction. The presence of phlogopite and pargasite in mantle xenoliths lends strong support to mantle metasomatism. ?? 1990.

  18. Midcontinent rift volcanism in the Lake Superior region: Sr, Nd, and Pb isotopic evidence for a mantle plume origin

    SciTech Connect

    Nicholson, S.W. Univ. of Minnesota, MN ); Shirey, S.B. )

    1990-07-10

    Between 1091 and 1098 Ma, most of a 15- to 20-km thickness of dominantly tholeiitic basalt erupted in the Midcontinent Rift System of the Lake Superior region, North American. The Portage Lake Volcanics in Michigan, which are the youngest MRS flood basalts, fall into distinctly high- and low-TiO{sub 2} types having different liquid lines of descent. Incompatible trace elements in both types of tholeiites are enriched compared to depleted or primitive mantle (La/Yb = 4.3-5.3; Th/Ta = 2.12-2.16; Zr/Y = 4.3-4.4), and both basalt types are isotopically indistinguishable. Sr, Nd, and Pb isotopic compositions of the Portage Lake tholeiites have {sup 87}Sr/{sup 86}Sr{sub i} {approx}0.7038, {epsilon}{sub Nd(1095 Ma)} {approx}0 {plus minus} 2, and {mu}{sub 1} {approx}8.2. Model ages with respect to a depleted mantle source (T{sub DM}) average about 1950-2100 Ma. Portage Lake rhyolits fall into two groups. Type I rhyolites have Nd and Pb isotopic characteristics ({epsilon}{sub Nd(1095 Ma)} {approx}0 to {minus}4.7; {mu}{sub 1} {approx}8.2-7.8) consistent with contamination of tholeiitic rocks by 5-10% Archean crust. The one type II rhyolite analyzed has Nd and Pb isotopic compositions ({epsilon}{sub Nd(1095 Ma)} {approx}{minus}13 to {minus}16; {mu}{sub 1} {approx}7.6-7.7) which are consistent with partial melting of Archean crust. Early Proterozoic crust was not a major contaminant of MRS rocks in the Lake Superior region. Most reported Nd and Pb isotopic compositions of MRS tholeiites from the main stage of volcanism in the Lake Superior region and of the Duluth Complex are comparable to the Nd and Pb isotopic data for Portage lake tholeiites. The isotopic enrichment of the MRS source compared to depleted mantle is striking and must have occurred at least 700 m.y. before 1100 Ma.

  19. Sr-Nd-Os-S isotope and PGE geochemistry of the Xiarihamu magmatic sulfide deposit in the Qinghai-Tibet plateau, China

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaowei; Tang, Qingyan; Li, Chusi; Wang, Yalei; Ripley, Edward M.

    2016-03-01

    The newly discovered Xiarihamu Ni-Cu deposit is located in the Eastern Kunlun orogenic belt in the northern part of the Qinghai-Tibet plateau, western China. It is the largest magmatic Ni-Cu sulfide deposit found thus far in an arc setting worldwide and ranks second in China in terms of total Ni resources. Fe-Ni-Cu sulfide mineralization occurs in a small ultramafic body that is part of a larger mafic-ultramafic complex formed by protracted Silurian-Early Devonian basaltic magmatism. The mineralized ultramafic body is composed predominantly of lherzolite and olivine websterite, with minor dunite, websterite and orthopyroxenite. Here we report new PGE (platinum group element) data and the results of a new, integrated Sr-Nd-Os-S isotope study. The initial concentrations of Rh and Pd in the parental magma are estimated to be 0.014 ppb and 0.24 ppb, respectively, which are more than one order of magnitude lower than those in undepleted mantle-derived magmas such as many continental picrites. The observed PGE depletions in the Xiarihamu parental magma are attributed to sulfide retention in the source mantle, because the degree of partial melting required to generate the Xiarihamu primary magma was not high enough for a magma of that composition to dissolve all sulfides in the source. The (87Sr/86Sr) i ratios and ɛNd (t) of the Xiarihamu host rocks range from 0.7062 to 0.7105 and from -1.97 to -5.74, respectively, indicating 5-30 wt% crustal contamination in the Xiarihamu magma. These data also reveal that the source mantle for the Xiarihamu magma is isotopically (Sr-Nd) more enriched than that for the average Cenozoic arc basalt. The γOs(t) and δ34S values of sulfide ores from the Xiarihamu deposit range from 78 to 1393 and from 2 to 6‰, respectively. These values clearly indicate addition of crustal Os and S to the Xiarihamu parental magma. Metal tenors such as Ni and Rh are inversely correlated with γOs(t) and δ34S values. This indicates that mixing between

  20. Sr, Nd, Pb Isotope geochemistry and magma evolution of the potassic volcanic rocks, Wudalianchi, Northeast China

    USGS Publications Warehouse

    Junwen, W.; Guanghong, X.; Tatsumoto, M.; Basu, A.R.

    1989-01-01

    Wudalianchi volcanic rocks are the most typical Cenozoic potassic volcanic rocks in eastern China. Compositional comparisons between whole rocks and glasses of various occurrences indicate that the magma tends to become rich in silica and alkalis as a result of crystal differentiation in the course of evolution. They are unique in isotopic composition with more radiogenic Sr but less radiogenic Pb.87Sr /86 Sr is higher and143Nd/144Nd is lower than the undifferentiated global values. In comparison to continental potash volcanic rocks, Pb isotopes are apparently lower. These various threads of evidence indicate that the rocks were derived from a primary enriched mantle which had not been subjected to reworking and shows no sign of incorporation of crustal material. The correlation between Pb and Sr suggests the regional heterogeneity in the upper mantle in terms of chemical composition. ?? 1989 Institute of Geochemistry, Chinese Academy of Sciences.

  1. Geochronology, geochemistry, and Sr-Nd-Hf isotopes of the early Paleozoic igneous rocks in the Duobaoshan area, NE China, and their geological significance

    NASA Astrophysics Data System (ADS)

    Wu, Guang; Chen, Yuchuan; Sun, Fengyue; Liu, Jun; Wang, Guorui; Xu, Bei

    2015-01-01

    have similar Sr, Nd, and Hf isotopic features, such as low initial 87Sr/86Sr ratios (varying from 0.704404 to 0.705820), very high εHf(t) and εNd(t) values (varying from 11.5 to 17.6 and 5.24 to 5.77, respectively), and young Hf and Nd single-stage and two-stage model ages. Both geochemical characteristics and Sr-Nd-Hf isotope compositions of the volcanic rocks suggest that the late Ordovician volcanic rocks occurred in an island-arc setting and were formed by partial melting of a depleted mantle wedge modified by predominant slab fluids. Our study in this work indicates that the collision of the Xing'an and Argun massifs at least took place ∼500 Ma ago and that a westward subduction of an oceanic plate, which is located between the Songnen-Zhangguangcai Range and Xing'an massifs, took place during the late Ordovician.

  2. Zircon U-Pb geochronology, Sr-Nd-Hf isotopic composition and geological significance of the Late Triassic Baijiazhuang and Lvjing granitic plutons in West Qinling Orogen

    NASA Astrophysics Data System (ADS)

    Duan, Meng; Niu, Yaoling; Kong, Juanjuan; Sun, Pu; Hu, Yan; Zhang, Yu; Chen, Shuo; Li, Jiyong

    2016-09-01

    The Qinling Orogen was a consequence of continental collision of the South China Craton with the North China Craton in the Triassic and caused widespread granitoid magmatism. However, the petrogenesis of these granitoids remains controversial. In this paper, we choose the Baijiazhuang (BJZ) and Lvjing (LJ) plutons in the West Qinling Orogen for a combined study of the zircon U-Pb geochronology, whole-rock major and trace element compositions and Sr-Nd-Hf isotopic characteristics. We obtained zircon crystallization ages of ~ 216 Ma and ~ 212 Ma for the BJZ and the LJ plutons, respectively. The granitoid samples from both plutons have high K2O metaluminous to peraluminous compositions. They are enriched in large ion lithophile elements (LILEs), light rare earth elements (LREEs) and depleted in high field-strength elements (HFSEs) with significant negative Eu anomalies. The BJZ samples have initial Sr isotopic ratios of 0.7032 to 0.7078, εNd(t) of - 10.99 to - 8.54 and εHf (t) of - 10.22 to - 6.41. The LJ granitoids have initial Sr isotopic ratios of 0.7070 to 0.7080, εNd(t) of - 5.37 to - 4.58 and εHf(t) of - 3.64 to - 1.78. The enriched isotopic characteristics of the two plutons are consistent with their source being dominated by ancient continental crust. However, two BJZ samples show depleted Sr isotope compositions, which may infer possible involvement of mantle materials. Mantle-derived melt, which formed from partial melting of mantle wedge peridotite facilitated by dehydration of the subducted/subducting Mianlue ocean crust, provide the required heat for the crustal melting while also contributing to the compositions of these granitoids. That is, the two granitic plutons are magmatic responses to the closure of the Mianlue ocean basin and the continental collision between the Yangtze and South Qinling crustal terranes.

  3. Geochemical study (major, trace elements and Pb-Sr-Nd isotopes) of mantle material obducted onto the North African margin (Edough Massif, North Eastern Algeria): Tethys fragments or lost remnants of the Liguro-Provençal basin?

    NASA Astrophysics Data System (ADS)

    Bosch, Delphine; Hammor, Dalila; Mechati, Mehdi; Fernandez, Laure; Bruguier, Olivier; Caby, Renaud; Verdoux, Patrick

    2014-06-01

    The Maghrebides, Betics and some parts of the Calabrian, NE Sicilian and Tuscan allochtons constitute dismembered fragments of the Alpine belt that resulted from the Cenozoic collision between Africa and Eurasia and the opening of the Western Mediterranean basin. Mineral and whole-rock geochemical analyses have been performed on three distinct outcrops of mantle material from the Edough Massif of NE Algeria, namely the Bou Maiza (BM) gabbros, the La Voile Noire (LVN) amphibolites and the Sidi Mohamed (SM) peridotites. In all samples, Sr isotopes are largely affected by seawater alteration (87Sr/86Sract. > 0.70384 and up to 0.70888) and cannot be used to evaluate the nature of the source reservoirs. SM peridotites display variable depleted mantle Nd isotopic signatures (εNdact. from + 7.0 to + 12.2) and geochemical features suggesting no significant chemical depletion as a result of partial melting and melt extraction (Mg# < 90; slightly LREE-depleted patterns with La/YbN = 0.33-0.39). These rocks are interpreted as parts of the subcontinental lithospheric mantle incorporated into the crustal units of the Edough Massif during the early stages of opening of the Algerian basin. BM gabbros and LVN amphibolites show geochemical signatures indicating derivation from a common depleted mantle reservoir (εNd > + 7.9) and are likely cogenetic, but without filiation with the SM peridotites. Pb isotopes indicate a contribution of sediments in the source reservoir, which is attributed to contamination solely by hydrous fluids released from a sedimentary component. This observation, together with a LILE-enrichment, suggests a back-arc basin environment. These results indicate that BM and LVN units were obducted onto the North African margin and subsequently fragmented, probably during doming and exhumation of the lower continental crust of the Edough massif. Doming resulted in opposite movements of the overlying oceanic units, southward for the BM units and northward for LVN

  4. Geochemical Fingerprinting of Trans-Atlantic African Dust Based on Radiogenic Sr-Nd-Hf Isotopes and Rare Earth Element Anomalies

    NASA Astrophysics Data System (ADS)

    Pourmand, Ali; Prospero, Joseph; Sharifi, Arash

    2015-04-01

    Mineral dust is an important component of Earth's climate system and biogeochemical cycles on a global scale. In order to understand the relationship between climate processes in the source areas and the properties of aerosols at distant receptor sites, we must be able to identify the source provenance of dust. Here we present a multiproxy study that characterizes the temporal variability in the geochemical composition of long-range African dust (LRAD) collected between 2003 and 2011 in the trade winds on the Caribbean island of Barbados. We find systematic differences between Sr-Nd-Hf isotopic composition and rare earth element anomalies of individual dust events and evidence of seasonal shifts in dust source activity and transport. These results indicate that coherent geochemical source signatures of LRAD can be preserved even after transport across thousands of kilometers. We investigated the possibility of identifying the potential source areas through comparisons with literature data. However, these data are almost entirely based on measurements of soil and sediment samples; this could lead to biases because of soil-aerosol particle size and composition differences. Nonetheless, our data suggest that many samples are linked to sources in Mali and sub-Saharan regions. Radiogenic Nd-Hf composition of aerosols can potentially be a useful proxy to study the proximity of mineral dust sources to depositional sites. In order to establish firmer links between LRAD and dust source areas, however, we require much more data on the geochemical composition of aerosols from potential source areas in North Africa.

  5. Geochemical Fingerprinting of Trans-Atlantic African Dust Based on Radiogenic Sr-Nd-Hf Isotopes and Rare Earth Element Anomalies

    NASA Astrophysics Data System (ADS)

    Pourmand, A.; Prospero, J. M.; Sharifi, A.

    2014-12-01

    Mineral dust is an important component of Earth's climate system and biogeochemical cycles on a global scale. In order to understand the relationship between climate processes in the source areas and the properties of aerosols at distant receptor sites, we must be able to identify the source provenance of dust. Here we present a multiproxy study that characterizes the temporal variability in the geochemical composition of long-range African dust (LRAD) collected between 2003 and 2011 in the trade winds on the Caribbean island of Barbados. We find systematic differences between Sr-Nd-Hf isotopic composition and rare earth element anomalies of individual dust events and evidence of seasonal shifts in dust source activity and transport. These results indicate that coherent geochemical source signatures of LRAD can be preserved even after transport across thousands of kilometers. We investigated the possibility of identifying the potential source areas through comparisons with literature data. However, these data are almost entirely based on measurements of soil and sediment samples; this could lead to biases because of soil-aerosol particle size and composition differences. Nonetheless, our data suggest that many samples are linked to sources in Mali and sub-Saharan regions. Radiogenic Nd-Hf composition of aerosols can potentially be a useful proxy to study the proximity of mineral dust sources to depositional sites. In order to establish firmer links between LRAD and dust source areas, however, we require much more data on the geochemical composition of aerosols from potential source areas in North Africa.

  6. Magmatic processes at Popocatepetl volcano, Mexico: petrology, geochemistry and Sr-Nd-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Schaaf, P.; Stimac, J.; Siebe, C.; Mac¡as, J.

    2003-12-01

    Popocatepetl volcano is one of the most famous and most active stratovolcanoes of the Trans-Mexican Volcanic Belt (TMVB). It is located 60 km south-east of Mexico-City and 40 km west of the city of Puebla, both cities have more than 30 million inhabitants. In this contribution we present a study of Late Pleistocene to Recent products of Popocatépetl (Popo) volcano and surrounding scoria cones to better establish their genetic relationship and magmatic history. Popo and flanking vents are located within the central portion of the Trans Mexican Volcanic Belt, which is related to oblique subduction of young oceanic lithosphere. Current activity of Popo can be understood in the context of its past eruptions and those from surrounding scoria cones. The latest cycle of eruption began Dec. 21, 1994 with continuous to pulsating emission of phreatic ash. The last important event happened on July 19, 2003, covering Mexico-City with a thin ash-layer. Both Popo and surrounding scoria cones produced moderate-K, calc-alkaline rocks, with the two groups differing mainly in degree of differentiation, water content, and oxidation state. Some vent samples on the immediate flanks of Popo and have phenocryst assemblages and compositions transitional between typical flanking vent and stratovolcano samples. Monogenetic vents produced mainly basaltic andesites to andesites, primarily by crystal fractionation of Ol (Fo80-90)+chromite, 2PyxñOl, and 2PyxñPlagñHb assemblages, with minor assimilation of crustal debris. The andesitic to dacitic rocks of Popo are dominated by Plag-2Pyx-2OxideñHbl assemblages, with variable amounts of Ol (Fo70-90)+chromite xenocrysts. A few Popo samples contain locally abundant xenolithic debris of cognate-granitoid intrusions and their metasedimentary wallrocks. The two suites share parental Mg-rich basaltic andesite magmas, with the Popo magmas reflecting longer residence in the crust, and enhanced hydration and oxidation due to the resulting processes of

  7. Constraints on slab inputs and mantle source compositions in the northern Cascade arc (Garibaldi belt) from Sr-Nd-Pb-Hf isotopes and trace elements in primitive basalts

    NASA Astrophysics Data System (ADS)

    Mullen, E. K.; Carpentier, M.; Weis, D.

    2011-12-01

    The northernmost segment of the Cascade arc, known as the Garibaldi volcanic belt (GVB), extends from Glacier Peak in Washington to the Bridge River cones in British Columbia. GVB primitive basalts display strong arc-parallel geochemical gradients, most prominently a northerly progression from calc-alkaline to highly alkalic compositions, which present an ideal opportunity to address key questions regarding the origin of primary arc basalts including the compositions and relative inputs of sub-arc mantle sources and slab-derived fluids/melts. The gradient in GVB basalt alkalinity was proposed to result from a northerly reduction in slab-derived contributions to the sub-arc mantle wedge, a consequence of the ~4 myr decrease in slab age at the trench [1-3]. As a test of this hypothesis, we have obtained new whole-rock high-precision isotopic (Sr, Nd, Pb, Hf) and trace element data for the GVB basalt suites previously investigated by Green and others. La/Nb decreases from south (4.25 at Glacier Peak) to north (0.78 at Bridge River), confirming a progressive reduction in the "arc signature" (elevated LILE and LREE abundances relative to HFSE and HREE). 87Sr/86Sr ranges from 0.70310 to 0.70396, 206Pb/204Pb from 18.65 to 18.92, ɛNd from 8.5 to 3.8, and ɛHf from 13.3 to 8.7. Our data overlap the Sr-Nd-Pb isotopic compositions of primitive samples at Mt. Baker and Chilliwack batholith [4], but extend to more depleted compositions. GVB basalts are isotopically distinct from other Cascade arc primitive basalts, with systematically lower 208Pb/206Pb at a given 206Pb/204Pb and higher ɛNd at a given 87Sr/86Sr. In Pb-Pb space, GVB basalts define a linear trend extending from Explorer MORB to local subducting sediments drilled at ODP Sites 888 and 1027 in the northern Cascadia basin. We interpret this array as a mixing line reflecting variable sediment input to the mantle. However, Sr, Pb and Nd isotope ratios are only weakly correlated with La/Nb and latitude, whereas 208Pb

  8. Chemical and isotopical characterisation of atmospheric pollution from urban and rural environments of the Rhine Valley (PCBs, trace elements and Sr-, Nd- and Pb- isotope determinations)

    NASA Astrophysics Data System (ADS)

    Guéguen, F.; Stille, P.; Millet, M.; Dietze, V.; Gieré, R.

    2010-05-01

    Atmosheric samples (gas and particulate matter (PM)) have been collected in the urban environment of the cities of Strasbourg and Kehl and in the rural environment of the Vosges mountains. For sampling of gas phase pollutants and particles two different passive sampler devices have been applied (PAS and Sigma-2, respectively). The PAS has been used for gas phase Polychlorinated Biphenyls (PCBs) sampling and is based on the passive adsorption of gas phase pollutants onto XAD-2 resin. The Sigma-2 sampler is based on the sedimentation principle (Stoke's law), collects particles in the size range 2.5-100 μm and allows the calculation of ambient air concentration. The sampler is mainly used for routine air quality measurements in German health and recreation resorts and in this field study the first time for collection of samples for subsequent trace element and isotope analysis. The collection time for the Sigma-2 and PAS are four and two weeks, respectively. Major and trace elements have been analyzed by ICP-MS and the Sr, Nd and Pb isotope ratios by a sector field MC-ICP-MS (Neptune) while PCBs were ASE extracted and analysed by GC-ECD. The aerosol data are compared with those from tree barks which have previously been used successfully as biomonitors of atmospheric pollution (Lahd Geagea et al. 2008)1. The outer 1 mm thick part of the bark has been analyzed corresponding to about 2 to 8 years of accumulation. Some of the trace elements (Cr, Ni and Mo) of the aerosol samples are strongly (up to 1000 times) enriched compared to average 'upper continental crust (UCC)'. Normalization to a « natural » sample with an atmospheric baseline composition allows to identify industrial contributions: transition metals (Cr, Mn, Fe, Co, Ni, Zn, Mo, Cd), Ba and Pb appear to be important elements in steel plant and incinerator (chemical waste) emissions. Similarly enrichment in light rare earth elements (La, Pr, Nd) is observable. The enrichments increase with decreasing distance

  9. Repeated kimberlite magmatism beneath Yakutia and its relationship to Siberian flood volcanism: Insights from in situ U-Pb and Sr-Nd perovskite isotope analysis

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Liu, Chuan-Zhou; Tappe, Sebastian; Kostrovitsky, Sergey I.; Wu, Fu-Yuan; Yakovlev, Dmitry; Yang, Yue-Heng; Yang, Jin-Hui

    2014-10-01

    We report combined U-Pb ages and Sr-Nd isotope compositions of perovskites from 50 kimberlite occurrences, sampled from 9 fields across the Yakutian kimberlite province on the Siberian craton. The new U-Pb ages, together with previously reported geochronological constraints, suggest that kimberlite magmas formed repeatedly during at least 4 episodes: Late Silurian-Early Devonian (419-410 Ma), Late Devonian-Early Carboniferous (376-347 Ma), Late Triassic (231-215 Ma), and Middle/Late Jurassic (171-156 Ma). Recurrent kimberlite melt production beneath the Siberian craton - before and after flood basalt volcanism at 250 Ma - provides a unique opportunity to test existing models for the origin of global kimberlite magmatism. The internally consistent Sr and Nd isotope dataset for perovskites reveals that the Paleozoic and Mesozoic kimberlites of Yakutia have distinctly different initial radiogenic isotope compositions. There exists a notable increase in the initial 143Nd/144Nd ratios through time, with an apparent isotopic evolution that is intermediate between that of Bulk Earth and Depleted MORB Mantle. While the Paleozoic samples range between initial 87Sr/86Sr of 0.7028-0.7034 and 143Nd/144Nd of 0.51229-0.51241, the Mesozoic samples show values between 0.7032-0.7038 and 0.51245-0.51271, respectively. Importantly, perovskites from all studied Yakutian kimberlite fields and age groups have moderately depleted initial εNd values that fall within a relatively narrow range between +1.8 and +5.5. The perovskite isotope systematics of the Yakutian kimberlites are interpreted to reflect magma derivation from the convecting upper mantle, which appears to have a record of continuous melt depletion and crustal recycling throughout the Phanerozoic. The analyzed perovskites neither record highly depleted nor highly enriched isotopic components, which had been previously identified in likely plume-related Siberian Trap basalts. The Siberian craton has frequently been suggested

  10. Mixing and melt sources in the Miocene Aztec Wash pluton (Nevada, USA) as revealed by zircon Hf and O and whole rock Sr, Nd, and Hf isotopes

    NASA Astrophysics Data System (ADS)

    Ryan, M.; Miller, J. S.; Miller, C. F.; Bromley, S.; Davies, G. R.; Schmitt, A. K.

    2011-12-01

    The 15.6 Ma Aztec Wash Pluton (AWP) is one of several Miocene intrusions located within the northern Colorado River extensional corridor. Extensive E-W tilting of fault blocks has exposed the pluton from the roof to 5 km structural depth. Earlier field and petrologic studies subdivided the AWP into two distinct zones: (1) a Granite Zone (GZ) comprised of relatively homogeneous granite with subtle differences in textures and mineralogy; (2) a Heterogeneous Zone (HZ), which interfingers the GZ, contains evidence for mafic and felsic magma input with a wide compositional range (42-78 wt% SiO2), and abundant field evidence for hybridization. Previous whole rock geochemistry and zircon trace element analyses indicated that compositional variation was produced by multi-component mixing between mafic and felsic melts within the HZ. New whole rock Sr, Nd, and Hf isotope data from the HZ show that all rocks (including high-silica granites) formed by mixing Precambrian crust and enriched mantle, with mixtures having a large mantle fraction (≥50%). New Hf (n=189) and O (n=241) isotope analyses of zircon from samples in the HZ confirm these melt sources and provide a broader perspective on hybridization processes within the AWP. Zircon grains from all samples show heterogeneous Hf and O isotopic compositions (-5 to -18 ɛHf; 4.5-7.5% δ18O), but despite the clear signature of Precambrian crust in the whole rock data, obvious Precambrian zircons (or cores) were mostly absent; only one zircon was clearly Precambrian (ɛHf = -25). Resolvable intragrain variability is relatively limited (including the Precambrian grain, which is unzoned). Zircons from hand samples and from compositional groups also show heterogeneous ɛHf and δ18O values, although the spreads are more restricted than in the whole data set (6-10 ɛHf in granites, 5-7 ɛHf in intermediate "hybrids", 5-6 ɛHf in gabbro/diorite sheets). Oxygen isotope values for the zircons also show intra-handsample heterogeneity

  11. Petrogenesis of the Late Triassic volcanic rocks in the Southern Yidun arc, SW China: Constraints from the geochronology, geochemistry, and Sr-Nd-Pb-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Leng, Cheng-Biao; Huang, Qiu-Yue; Zhang, Xing-Chun; Wang, Shou-Xu; Zhong, Hong; Hu, Rui-Zhong; Bi, Xian-Wu; Zhu, Jing-Jing; Wang, Xin-Song

    2014-03-01

    Studies on zircon ages, petrology, major and trace element geochemistry, and Sr-Nd-Hf-Pb isotopic geochemistry of intermediate volcanic rocks from the Southern Yidun arc, Sanjiang-Tethyan Orogenic Belt, SW China have been undertaken in this paper. They are used to discuss the petrogenesis of these rocks and to constrain the tectonic setting and evolution of the Yidun arc. These intermediate volcanic rocks were erupted at ca. 220 Ma (U-Pb zircon ages). Trachyandesite is the dominant lithology among these volcanic rocks, and is mainly composed of hornblende and plagioclase, with minor clinopyroxene and biotite. A hornblende geobarometer suggests that the stagnation of magma in the lower crust, where plagioclase crystallization was suppressed while hornblende crystallized, giving rise to high Sr/Y ratios that are one of the distinguishing features of adakites, after the primary magma originated from the lithospheric mantle wedge. Steeply right-inclined Rare Earth Element (REE) pattern combined with high La/Yb ratios suggests adakitic affinity of these volcanic rocks, implying that slab-melt from the subducting oceanic crust is a necessary component in the primary magma. Besides, trace element geochemistry and isotopic geochemistry also indicate that partial melting of pelagic sediments in the subduction zone and noticeable contamination with the lower crust were involved in the evolution of parental magma of these volcanic rocks. Based on previous work on the Northern Yidun arc and this study, we propose that the subduction was initiated in the Northern Yidun arc and extended to the southern part and that the Northern Yidun arc is an island arc while the Southern Yidun arc represents a continental arc, probably caused by the existence of the Zhongza Massif, that was invoked to be derived from Yangtze Block, as a possible basement of the Southern Yidun arc.

  12. Target rocks, impact glasses, and melt rocks from the Lonar crater, India: Highly siderophile element systematics and Sr-Nd-Os isotopic signatures

    NASA Astrophysics Data System (ADS)

    Schulz, Toni; Luguet, Ambre; Wegner, Wencke; Acken, David; Koeberl, Christian

    2016-07-01

    The Lonar crater is a ~0.57-Myr-old impact structure located in the Deccan Traps of the Indian peninsula. It probably represents the best-preserved impact structure hosted in continental flood basalts, providing unique opportunities to study processes of impact cratering in basaltic targets. Here we present highly siderophile element (HSE) abundances and Sr-Nd and Os isotope data for target basalts and impactites (impact glasses and impact melt rocks) from the Lonar area. These tools may enable us to better constrain the interplay of a variety of impact-related processes such as mixing, volatilization, and contamination. Strontium and Nd isotopic compositions of impactites confirm and extend earlier suggestions about the incorporation of ancient basement rocks in Lonar impactites. In the Re-Os isochron plot, target basalts exhibit considerable scatter around a 65.6 Myr Re-Os reference isochron, most likely reflecting weathering and/or magma replenishment processes. Most impactites plot at distinctly lower 187Re/188Os and 187Os/188Os ratios compared to the target rocks and exhibit up to two orders of magnitude higher abundances of Ir, Os, and Ru. Moreover, the impactites show near-chondritic interelement ratios of HSE. We interpret our results in terms of an addition of up to 0.03% of a chondritc component to most impact glasses and impact melt rocks. The magnitude of the admixture is significantly lower than the earlier reported 12-20 wt% of extraterrestrial component for Lonar impact spherules, reflecting the typical difference in the distribution of projectile component between impact glass spherules and bulk impactites.

  13. Petrological and Sr-Nd-Os isotopic constraints on the origin of the Fanshan ultrapotassic complex from the North China Craton

    NASA Astrophysics Data System (ADS)

    Niu, Xiaolu; Chen, Bin; Liu, Ankun; Suzuki, K.; Ma, Xu

    2012-09-01

    The Fanshan ultramafic-syenitic complex is located on the northern margin of North China Craton, with zircon U-Pb ages of 220 Ma. It is a concentrically zoned complex, with syenite in the core, surrounded by ultramafic rocks (clinopyroxenite, glimmerite) and garnet-clinopyroxene syenite, respectively, towards the rim. Diopside, biotite, orthoclase, melanite, magnetite and apatite are the major minerals, with subordinate sphene and calcite. Mineralogy, petrology and geochemical studies point to the formation of the complex through fractional crystallization and accumulation from a SiO2-undersaturated ultrapotassic alkaline-peralkaline parent magma that is characterized by high CaO, Fe2O3, K2O and fluid compositions (P2O5, CO2, H2O, F), and by high temperature and high oxygen fugacity. Rocks from the complex are highly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE; e.g., Rb, Ba, Sr), depleted in high field strength elements (HFSE; e.g., Nb, Ta, Ti), and show relatively homogeneous Sr-Nd isotopic compositions with initial 87Sr/86Sr = 0.70513-0.70597 and ɛNd(t) = - 5.8 to - 5.3. The data suggest that the Fanshan complex originated from a phlogopite-clinopyroxenite-rich lithosphere mantle source that had previously been metasomatized by melts from carbonated oceanic crust above a subduction zone. Highly radiogenic Os isotope compositions (initial 187Os/188Os = 0.299-2.449) suggest that the parent magma to the Fanshan complex has been contaminated by Precambrian mafic crustal rocks during magma emplacement in crustal levels. The occurrence of the Fanshan complex, together with many other ultramafic/alkaline plutons of similar ages, on the northern margin of the North China Craton suggests that the northern margin of the craton entered into a large-scale extensional regime in late Triassic after the final amalgamation between Mongolian microcontinent and the craton.

  14. Sr-Nd-Hf-Pb Isotopic Constraints on the Role of South China Sea Sediments in Mantle Wedge Metasomatism Beneath the North Luzon Arc

    NASA Astrophysics Data System (ADS)

    Kuo, T.; Yang, H.; Lee, D.; Lai, Y.

    2007-12-01

    Recycling sediments into mantle through subduction zones causes mantle heterogeneity and is critical on chemical evolution of the Earth. Because the compositions of subducted sediments vary significantly between subduction zones, there is a need to characterize the sediments from individual subduction zones and evaluate their contributions to mantle wedge metasomatism. This study investigates the role of South China Sea (SCS) sediments in the chemical characteristics of the North Luzon arc (NLA) magmatism. Thirty-five sediment samples (0-35 Ma) recovered by ODP Leg 184 at sites 1148 and 1147 were analyzed for Sr, Nd, Hf, and Pb isotope ratios and trace element abundances. Results were compared to the data of the North Luzon arc lavas to establish models for mantle wedge metasomatism. The NLA lavas deviate from the terrestrial array to higher 176Hf/177Hf values at a given 143Nd/144Nd value, consistent with involving subducted sediments in source regions. Since Hf in the subducted slabs cannot be transported to mantle wedges by hydrous fluids, slab-derived siliceous melts are the most probable metasomatic agents. This algorithm leads to three metasomatism models: (I) addition of bulk sediments to depleted mantle, (II) depleted mantle metasomatized by sediment-derived melts, and (III) depleted mantle metasomatized by melts derived from sediments and altered oceanic crust (AOC). Although not considered in model calculations, the contributions of sediment-derived and AOC-derived fluids are also addressed qualitatively. The first model results in mixing curves overlapping with the mantle array in Sr versus Nd and Hf isotope plots, inconsistent with the distributions of the NLA lavas, which deviate from mantle array to lower 143Nd/144Nd and 176Hf/177Hf values. The involvement of sediment-derived melts (Model II) leads to source compositions with larger deviation from the NLA lavas in Sr versus Nd and Hf isotope plots, because sediment-derived melts have higher Sr/Nd and

  15. Re-Assessment of Cascade Arc Mantle Heterogeneity and Slab Inputs using High-Precision Pb-Hf-Sr-Nd Isotopic Data

    NASA Astrophysics Data System (ADS)

    Mullen, E.; Weis, D.; Martindale, M.

    2015-12-01

    In the Cascade Arc of western North America, several primitive magma lineages are distinguished by major and trace elements: calc-alkaline basalt (CAB), high-alumina olivine tholeiite (HAOT) and relatively minor intraplate basalt (IPB). Previous studies have concluded that these basalt groups represent distinct mantle sources 1. However, new high precision Sr-Nd-Hf-Pb isotope data for primitive magmas from 7 High Cascades volcanic centers show that CAB and HAOT are derived from the same isotopically depleted mantle, with the exception of Mt. Adams-Simcoe backarc basalts. In isotope space, High Cascades CAB and HAOT have similar compositional ranges, forming a single mixing array between two end members that coincide with Juan de Fuca (JdF) MORB and bulk average northern Cascadia sediment2. The High Cascades array is consistent with a depleted sub-arc mantle similar to JdF MORB-source, modified by a homogenized subducted sediment component. The High Cascades array does not intersect Astoria Fan compositions, consistent with the young depositional age of this sediment3. Trace element data for CAB also indicate contributions from a third end member that is a match to fluid derived from subducting JdF MORB. Glacier Peak, the southernmost Garibaldi Belt center, also plots on the High Cascades array. More northerly Garibaldi Belt basalts have lower 208Pb*/206Pb* and ɛHf, reflecting influx of enriched mantle at the northern slab edge that generates IPB4. Mt. Adams-Simcoe HAOT and IPB tap a second enriched mantle component that is consistent with a slab tear in this backarc region. The most isotopically 'enriched' High Cascades CAB and HAOT overlap in isotope and trace element compositions with the Imnaha (C2) component of the Columbia River basalts5, indicating that this mantle is a widespread and long-lived feature in the Pacific Northwest. 1Schmidt et al. 2008, EPSL 266, 166. 2Carpentier et al. 2014, Chem. Geol. 382, 67. 3Prytulak et al. 2006, Chem. Geol. 233, 276. 4

  16. Zircon U-Pb ages, geochemical and Sr-Nd-Pb-Hf isotopic constraints on petrogenesis of the Tarom-Olya pluton, Alborz magmatic belt, NW Iran

    NASA Astrophysics Data System (ADS)

    Nabatian, Ghasem; Jiang, Shao-Yong; Honarmand, Maryam; Neubauer, Franz

    2016-02-01

    A petrological, geochemical and Sr-Nd-Pb isotopic study was carried out on the Tarom-Olya pluton, Iran, in the central part of the Alpine-Himalayan orogenic belt. The pluton is composed of diorite, monzonite, quartz-monzonite and monzogranite, which form part of the Western Alborz magmatic belt. LA-ICP-MS analyses of zircons yield ages from 35.7 ± 0.8 Ma to 37.7 ± 0.5 Ma, interpreted as the ages of crystallization of magmas. Rocks from the pluton have SiO2 contents ranging from 57.0 to 69.9 wt.%, high K2O + Na2O (5.5 to 10.3 wt.%) and K2O/Na2O ratio of 0.9 to 2.0. Geochemical discrimination criteria show I-type and shoshonitic features for the studied rocks. All investigated rocks are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs), depleted in high-field strength elements (HFSEs), and show weak or insignificant Eu anomalies (Eu/Eu* = 0.57-1.02) in chondrite-normalized trace element patterns. The Tarom-Olya pluton samples also show depletions in Nb, Ta and Ti typical of subduction-related arc magmatic signatures. The samples have relatively low ISr (0.7047-0.7051) and positive εNd(36 Ma) (+ 0.39 to + 2.10) values. The Pb isotopic ratios show a (206Pb/204Pb)i ratio of 18.49-18.67, (207Pb/204Pb)i ratio of 15.58-15.61 and (208Pb/204Pb)i ratio of 38.33-38.77. The εHf(t) values of the Tarom-Olya pluton zircons vary from - 5.9 to + 8.4, with a peak at + 2 to + 4. The depleted mantle Hf model ages for the Tarom-Olya samples are close to 600 Ma. These isotope evidences indicate contribution of juvenile sources in petrogenesis of the Tarom-Olya pluton. Geochemical and isotopic data suggest that the parental magma of the Tarom-Olya pluton was mainly derived from a sub-continental lithospheric mantle source, which was metasomatized by fluids and melts from the subducted Neotethyan slab with a minor crustal contribution. Subsequent hot asthenospheric upwelling and lithospheric extension caused decompression melting in the final stage of

  17. Inferences on sediment provenance and source weathering using major, trace and Sr-Nd isotopic compositional variations in alluvial sediments from Sirhind, Punjab, India

    NASA Astrophysics Data System (ADS)

    Paul, D.; Amir, M.; Sinha, R.; Singh, A.; Balakrishnan, S.

    2013-12-01

    Variations in major oxides and selected trace element concentrations, and Sr and Nd isotope ratios in sediments from two ~45m long cores drilled on the trace of a paleochannel near Sirhind, Sutlej plains, are used to characterize sediment provenance and source weathering vis-à-vis climate change. Drill core lithostratigraphy shows slit/clay layers down to a depth of 4m, and coarse to fine channel-sand bodies between ~4 and ~45m, occasionally interspersed by thin slity-clay layers. OSL ages of three samples constrain an age of 15.8 Ka at ~10m depth, corresponding to post Last Glacial Maximum (LGM) period. Major elemental abundances in de-carbonated bulk sediments (44 samples) fall within the range of surface sediments of present-day rivers sourced in the Himalayas. Strong positive correlations (R2>0.8) of Al2O3 (8.7-19.3 wt%) with K2O (2.23-4.03), MgO (0.49-2.72), Fe2O3 (0.89-7.21) and TiO2 (0.35-0.95), and negative correlation (R2=0.95) with SiO2 (62.5-83.7 wt%) are observed. Fe2O3/K2O ratio in these sediments suggest that sands are chemically immature and dominantly arkosic. A-CN-K plot reveals a weathering trend towards illite running parallel to the A-CN line, indicating weak to moderate weathering at source; similar conclusion is drawn from the chemical index of alternation (CIA) values ranging between 54 and 79. The Cr/Th ratios as well as the La-Th-Sc ternary plot suggest that sediments are dominantly derived from granitic to granodioritic sources. The radiogenic Sr-Nd isotopic composition in 18 samples from one drill-core shows range of values (87Sr/86Sr: 0.7409-0.7946; ɛNd: -23.2 to -15) similar to those of silicate rocks from the Higher and Lesser Himalaya, and the down-core variation pattern is similar to that reported for the Ganga-Yamuna interfluve sediments of similar age1. Down-core variations in 87Sr/86Sr and ɛNd reflect mixing of varying proportions of Higher and Lesser Himalayan sediments, the two dominant sources to the core site. Holocene

  18. The geochemical and Sr-Nd-Pb-He isotopic characterization of the mantle source of Rungwe Volcanic Province: comparison with the Afar mantle domain

    NASA Astrophysics Data System (ADS)

    Castillo, P. R.; Hilton, D. R.; Halldorsson, S. A.; Wang, R.

    2012-12-01

    The ultimate source of heat and magmatism associated with continental rifting in the East African Rift System (EARS) is generally viewed to be the African Superplume, but there is continuing debate on the surface expression of this large anomalous feature, which originates in the lower mantle. Previous studies have demonstrated an insignificant role for crustal contamination thereby identifying a single mantle plume signature in Quaternary basalts from the Main Ethiopian Rift in the northern EARS. This is designated to be the Afar plume and is characterized by, e.g., 3He/4He >15 RA, 206Pb/204Pb = 19.5 and 87Sr/86Sr = 0.7035 [Rooney et al., J. Pet. 53, 2012]. In contrast, the signature of plume(s) in the southern EARS is less constrained. Rogers et al. [EPSL 176, 2000] proposed a plume in the sub-lithospheric Kenyan mantle with characteristically lower 43Nd/144Nd than the Afar plume whereas Furman [JAES 48, 2007] advocated a high μ [HIMU] plume based primarily on the high 206Pb/204Pb ratios of lavas in all areas within and south of the Turkana Depression: both models assume a 3He/4He lower than the Afar plume. Here we report the trace element and Sr-Nd-Pb isotopic composition of basaltic lavas from the Rungwe Volcanic Province (RVP) in the southern extreme of the Western Rift previously identified as a high 3He/4He locality (~15 RA; [Hilton et al., GRL 38, 2011]). Trace element analyses are within the previously reported range of lava compositions that include a relatively large lithospheric component. More importantly, we identify correlations among incompatible trace element and isotopic ratios (e.g., 3He/4He vs 206Pb/204Pb, Rb/Sr, Nb/Ta; 87Sr/86Sr vs 208Pb/204Pb). Our new results suggest the presence of a distinct, high 3He/4He mantle source beneath RVP that is more radiogenic (e.g., 206Pb/204Pb up to ~19.8; 87Sr/86Sr up to 0.7055) than the Afar mantle plume. There is also very little or no HIMU signature in RPV basalts based on their high Sr and low Nd isotopic

  19. Sr, Nd and Pb Isotope Geochemistry for the Volcanic Rocks From the Aono and Abu Volcanic Groups in the SW Japan arc

    NASA Astrophysics Data System (ADS)

    Shimoda, G.; Morishita, Y.; Nohda, S.

    2002-12-01

    Although, there is no deep seismic activity beneath the W. Honshu Island in the SW Japan arc, recent seismic studies have revealed the existence of an aseismic slab beneath the area. Thus, the volcanism in the W. Honshu Island is considered to be related to the subduction. Since the subducting Philippine Sea plate caused inter-arc spreading, the volcanism of the Aono and Abu volcanic groups in the W. Honshu Island are inferred to be produced at the high temperature condition. The Aono volcanic group is one of volcanic groups, which comprise the volcanic front on the SW Japan arc, while the Abu volcanic group is on rather backarc side of the Aono volcanic group. In order to evaluate the origin of the volcanic rocks from the Aono and Abu volcanic groups, Sr, Nd and Pb isotopic and trace element compositions were determined. Nb troughs on a spider diagram indicate that these rocks are related to subduction process. Furthermore, high Sr/Y ratios and low Y concentrations of these rocks indicate that these are adakitic magma, which suggests that the magmas were produced by altered oceanic crust melting. Isotopic compositions of these rocks are situated between those of the Shikoku basin basalt and mantle xenoliths from the SW Japan arc on 87Sr/86Sr vs. 143Nd/144Nd and Pb-Pb diagrams. These show that geochemical characteristics of these rocks were produced by the mixing of a depleted slab derived component with an enriched mantle component. A 1/Sr vs. 87Sr/86Sr diagram designates that the depleted and enriched components have high and low Sr concentrations, respectively. Considering phase assemblages during melting processes of mantle peridotite and subducting altered oceanic crust, lower and higher Sr concentrations reflect lherzolite and eclogite melting respectively. This is consistent with the isotopic composition. To test the altered oceanic crust melting as a possible mechanism for the production of Aono and Abu volcanic rocks, melting calculations were conducted

  20. The Iceland plume in space and time: a Sr-Nd-Pb-Hf study of the North Atlantic rifted margin

    NASA Astrophysics Data System (ADS)

    Kempton, P. D.; Fitton, J. G.; Saunders, A. D.; Nowell, G. M.; Taylor, R. N.; Hardarson, B. S.; Pearson, G.

    2000-04-01

    New Sr-Nd-Pb-Hf data require the existence of at least four mantle components in the genesis of basalts from the the North Atlantic Igneous Province (NAIP): (1) one (or more likely a small range of) enriched component(s) within the Iceland plume, (2) a depleted component within the Iceland plume (distinct from the shallow N-MORB source), (3) a depleted sheath surrounding the plume and (4) shallow N-MORB source mantle. These components have been available since the major phase of igneous activity associated with plume head impact during Paleogene times. In Hf-Nd isotope space, samples from Iceland, DSDP Leg 49 (Sites 407, 408 and 409), ODP Legs 152 and 163 (southeast Greenland margin), the Reykjanes Ridge, Kolbeinsey Ridge and DSDP Leg 38 (Site 348) define fields that are oblique to the main ocean island basalt array and extend toward a component with higher 176Hf/ 177Hf than the N-MORB source available prior to arrival of the plume, as indicated by the compositions of Cretaceous basalts from Goban Spur (˜95 Ma). Aside from Goban Spur, only basalts from Hatton Bank on the oceanward side of the Rockall Plateau (DSDP Leg 81) lie consistently within the field of N-MORB, which indicates that the compositional influence of the plume did not reach this far south and east ˜55 Ma ago. Thus, Hf-Nd isotope systematics are consistent with previous studies which indicate that shallow MORB-source mantle does not represent the depleted component within the Iceland plume [Thirlwall, J. Geol. Soc. London 152 (1995) 991-996; Hards et al., J. Geol. Soc. London 152 (1995) 1003-1009; Fitton et al., Earth Planet. Sci. Lett. 153 (1997) 197-208]. They also indicate that the depleted component is a long-lived and intrinsic feature of the Iceland plume, generated during an ancient melting event in which a mineral (such as garnet) with a high Lu/Hf was a residual phase. Collectively, these data suggest a model for the Iceland plume in which a heterogeneous core, derived from the lower

  1. New Sr, Nd, and Pb isotopic data from plutons in the northern Great Basin: Implications for crustal structure and granite petrogenesis in the hinterland of the Sevier thrust belt

    SciTech Connect

    Wright, J.E. ); Wooden, J.L. )

    1991-05-01

    The influence of tectonic setting and age on the variation of isotopic signatures of granitic plutons in the northern Great Basin has, in general, not been apparent from previous investigations. None of these studies revealed the remarkable correlation shown by this expanded Sr, Nd, and Pb isotopic data base. Jurassic-Early Cretaceous plutons in the northern Great Basin have a limited range of Sr and Nd isotopic values that cluster near bulk earth. Construction of Sr 0.706 and {epsilon}{sub Nd} = {minus}7 isotopic boundaries is virtually impossible for plutons of this age range. In contrast, Upper Cretaceous peraluminous granites east of the {epsilon}{sub Nd} = {minus}7 line have very negative {epsilon}{sub Nd} values and high initial Sr ratios, and they appear to represent essentially pure crustal melts. The data favor a model that equates generation of these plutons via crustal thickening associated with the Sevier thrust belt. Cenozoic plutons appear to be mixtures of mantle and crustal reservoirs, and their isotopic systematics, along with those of the Late Cretaceous age plutonic suite, define a previously unrecognized, approximately east-west-trending crustal boundary between predominantly Archean crust to the north and predominantly Proterozoic crust to the south. The isotopic data from the Jurassic-Early Cretaceous plutonic suite do not reflect the presence of this boundary, suggesting that the isotopic systematics of this plutonic suite may not have been controlled by the same variations in crustal and/or mantle lithospheric structure at depth.

  2. Large scale isotopic Sr, Nd and O isotopic anatomy of altered oceanic crust: DSDP/ODP sites 417/418

    NASA Astrophysics Data System (ADS)

    Staudigel, Hubert; Davies, G. R.; Hart, Stanley R.; Marchant, K. M.; Smith, Brian. M.

    1995-02-01

    Large-scale compositional domains at DSDP/ODP drill sites 417A, 417D and 418A were analyzed for O, Sr and Nd isotope ratios, and REE, U, K, Rb and Sr abundances, to constrain the bulk chemical composition of the oceanic crust that is recycled at subduction zones. The combination of the three sites gives the composition of the upper oceanic crust in this region over a distance of about 8 km. The δ 18O SMOW and 87Sr/ 86Sr meas of compositional domains 10-100 m in size correlate well, with a range of 7.7-19.2 and 0.70364-0.70744, and mean of 9.96 and 0.70475, respectively. The Rb inventory of the upper crust increases by about an order of magnitude, while Sr contents remain constant. U abundances increase moderately under oxidizing alteration conditions and nearly triple in the commonly reducing alteration environments of the upper oceanic crust. REEs are influenced by alteration only to a small extent, and recycled oceanic crust is similar to MORB with respect to 143Nd/ 144Nd. Even though the average composition of the upper oceanic crust is well defined, the large scale composition varies widely. Highly altered compositional domains may not have a large impact on the average composition of the oceanic crust, but they may preferentially contribute to fluids or partial melts derived from the crust by prograde metamorphic reactions.

  3. U-Pb zircon dating, geochemical and Sr-Nd-Hf isotopic compositions of Motuo quartz-monzonite: Implication for the genesis and diversity of the high Ba-Sr granitoids in orogenic belt

    NASA Astrophysics Data System (ADS)

    Pan, Fa-Bin; Zhang, Hong-Fei; Xu, Wang-Chun; Guo, Liang; Luo, Bi-Ji; Wang, Shuai

    2016-02-01

    Early Paleogene granitoids in Southern Lhasa subterrane have been widely investigated and many petrogenesis and geodynamic models have been proposed in the past few years. However, contemporaneous granitoids in the Motuo tectono-magmatic belt, southeast Lhasa terrane, are still limitedly studied. Here we present the petrology, zircon U-Pb geochronology, whole-rock geochemistry, and Sr-Nd-Hf isotope data of the Damu and 52 K quartz-monzonite in the Motuo area. LA-ICP-MS U-Pb zircon dating shows that they have magma crystallization ages of 49 and 69 Ma, respectively. The Damu quartz-monzonite (SiO2 = 63.76-68.33 wt.%) is high-K calc-alkaline (K2O = 2.54-4.02 wt.% with K2O/Na2O = 0.59-1.09) and metaluminous to weakly peraluminous (A/CNK = 0.99-1.07). The 52 K quartz-monzonite (SiO2 = 61.12-66.12 wt.%) shows slightly higher K2O contents (3.80-5.28 wt.% with K2O/Na2O = 1.03-1.45) and metaluminous series (A/CNK = 0.96-1.00). The analyzed samples are characterized by high Ba (850-2573 ppm), Sr (534-986 ppm) contents, and fractionated REE patterns ((La/Yb)N = 22-72 and (Sm/Yb)N = 4.55-8.24). These geochemical features are comparable with those of high Ba-Sr granite. They display weakly evolved Sr-Nd-Hf compositions (whole-rock (87Sr/86Sr)0 = 0.7068 to 0.7086, εNd(t) = - 4.20 to - 3.41, and zircon εHf(t) = - 5.2 to - 0.9). Geochemical and Sr-Nd-Hf isotopic data reflect that the Damu and 52 K quartz-monzonite represent residual magma from AFC processes of lithospheric mantle-derived mafic melts. The over-thickened lower crust in the eastern Lhasa terrane had been delaminated during ca. 83-70 Ma, which led to the replacement of ancient lithospheric mantle by the juvenile lithospheric mantle. The juvenile mantle wedge in the study area was suspected to be metasomatized by melts that were derived from the foundering arc root, rather than the subducted sediments. Thus, the early Paleogene high Ba-Sr magmas from the SE Lhasa terrane may provide evidence for recycling of

  4. Mantle heterogeneity during the formation of the North Atlantic Igneous Province: Constraints from trace element and Sr-Nd-Os-O isotope systematics of Baffin Island picrites

    NASA Astrophysics Data System (ADS)

    Kent, A. J. R.; Stolper, E. M.; Francis, D.; Woodhead, J.; Frei, R.; Eiler, J.

    2004-11-01

    Sr-Nd-Os-O isotope and major and trace element data from ˜62 Ma picrites from Baffin Island constrain the composition of mantle sources sampled at the inception of North Atlantic Igneous Province (NAIP) magmatism. We recognize two compositional types. Depleted (N-type) lavas have low 87Sr/86Sri (0.702990-0.703060) and 187Os/188Osi (0.1220-0.1247) and high 143Nd/144Ndi (0.512989-0.512999) and are depleted in incompatible elements relative to primitive mantle. Enriched (E-type) lavas have higher 87Sr/86Sri (0.703306-0.703851) and 187Os/188Osi (0.1261-0.1303), lower 143Nd/144Ndi (0.512825-0.512906), and incompatible element concentrations similar to, or more enriched than, primitive mantle. There is also a subtle difference in oxygen isotope composition; E-type lavas are marginally lower in δ18Oolivine value (5.16-4.84‰) than N-type lavas (5.15-5.22‰). Chemical and isotopic variations between E- and N-type lavas are inconsistent with assimilation of crust and/or subcontinental lithospheric mantle and appear to instead reflect mixing between melts derived from two distinct mantle sources. Strontium-Nd-O isotope compositions and incompatible trace element abundances of N-type lavas suggest these are largely derived from the depleted upper mantle. The 187Os/188Osi ratios of N-type lavas can also be explained by such a model but require that the depleted upper mantle had γOs of approximately -5 to -7 at 62 Ma. This range overlaps the lowest γOs values measured in abyssal peridotites. Baffin Island lava compositions are also permissive of a model involving recharging of depleted upper mantle with 3He-rich material from the lower mantle (Stuart et al., Nature, 424, 57-59, 2003), with the proviso that recharge had no recognizable effect on the lithophile trace element and Sr-Nd-Os-O isotope composition. The origin of the enriched mantle component sampled by Baffin Island lavas is less clear but may be metasomatized and high-temperature-altered recycled oceanic

  5. Mode and timing of granitoid magmatism in the Västervik area (SE Sweden, Baltic Shield): Sr-Nd isotope and SIMS U-Pb age constraints

    NASA Astrophysics Data System (ADS)

    Kleinhanns, I. C.; Whitehouse, M. J.; Nolte, N.; Baero, W.; Wilsky, F.; Hansen, B. T.; Schoenberg, R.

    2015-01-01

    Observed geochemical and geophysical signatures in the southern Svecofennian domain (SD) and the Transscandinavian Igneous Belt (TIB) are explained through a model of tectonic cycling and episodic south-westward migration of a subduction zone system. The Västervik area is located between these two major tectonic domains and as such has received much attention. Granitoids of the Västervik area were recently re-grouped and classified within the context of this larger regional tectonic model, but a discrepancy between previous relative age estimations and the few available granitoid age determinations was noted. To address this issue, we have dated 13 granitoid samples using a high spatial resolution secondary ion mass spectrometry (SIMS) U-Pb technique. Our new results constrain the intrusion of the majority of granitoids to 1819-1795 Ma, thus placing them into the TIB-1 period. This age range also encompasses our new ages from the central granodiorite belt and the Örö-Hamnö pluton, demonstrating a previous overestimation of older granitoid generations in the Västervik area. Nonetheless, it is shown that Askersund/TIB-0 magmatism, represented by an augen gneiss sample dated to 1846 Ma, is unambiguously present as far south as the Västervik region. The anatectically generated leucogranites reveal TIB-1 ages and, as expected, older inherited zircon derived from the parental metasedimentary Västervik formation. By simple Sr-Nd isotope modeling it is further possible to deduce that most TIB-1 granitoids follow a simple (assimilation-) fractional crystallization petrogenetic trend. The youngest granitoid generation was produced through low-pressure fluid-absent crustal melting. In conclusion, granitoids of the Västervik area fit well into the proposed model for south-westward migration of a subduction zone system active in the Svecofennian domain and represent a new tectonic cycle. It is therefore possible to link the Svecofennian domain and the Transscandinavian

  6. The role of magma mixing in the evolution of high-K calc-alkaline granitoid suites: in situ trace element and Sr-Nd-Hf isotope constraints

    NASA Astrophysics Data System (ADS)

    Laurent, Oscar; Zeh, Armin; Gerdes, Axel; Slaby, Ewa; Villaros, Arnaud

    2015-04-01

    The so-called "I-type", high-K calc-alkaline granitoids are often considered as "hybrid" in origin, i.e. involving both mantle and crustal components in their petrogenesis. The interactions between both components either take place (1) at mantle levels (i.e. enriched mantle source); (2) at emplacement levels (i.e. crustal contamination and/or magma mixing with crustal melts) or (3) both. Magma mixing is, in particular, frequently invoked to explain the compositional range of high-K calc-alkaline granitoid suites, especially phases of intermediate composition (SiO2 = 60-65 wt.%) such as quartz-diorites or granodiorites. We investigated the role of magma mixing in the origin of such rocks using elemental and isotope (Sr-Nd-Hf) chemistry of magmatic minerals (plagioclase, zircon, apatite, titanite, epidote), measured in situ by LA-(MC-)ICPMS, allowing a much greater spatial resolution than classical whole-rock geochemistry. We focused on a suite of late-Archaean (2.69 Ga-old) high-K, calc-alkaline granitoids from the Pietersburg block, northern Kaapvaal Craton (South Africa): the Mashashane, Matlala, Matok and Moletsi plutons. Those plutons range from diorites to monzogranites, emplaced at different crustal levels but all within a relatively short time span and showing evidence for interactions (mingling), both at the outcrop and mineral scale. Hf isotope data on zircon confirm that all rocks are cogenetic (identical ɛHf(t)), but trace element and Sr isotopes in plagioclase point to the involvement of several components in their petrogenesis, at different stages of the magma evolution. The most mafic rocks (diorites) derive from the interaction, at mantle levels, between depleted peridotite and a sedimentary component of quartzofeldspathic nature. The mineral chemistry of more felsic rocks can be explained by (1) differentiation from the diorite magmas through Amp + Plag fractionation; (2) interactions with magmas derived from melting of local crust (tonalites

  7. Mineralogy and Sr-Nd isotopes of SPM and sediment from the Mandovi and Zuari estuaries: Influence of weathering and anthropogenic contribution

    NASA Astrophysics Data System (ADS)

    Purnachandra Rao, V.; Shynu, R.; Singh, Sunil K.; Naqvi, S. W. A.; Kessarkar, Pratima M.

    2015-04-01

    Clay minerals and Sr-Nd isotopes of suspended particulate matter (SPM) and bottom sediment were investigated along transect stations of the Mandovi and Zuari estuaries, western India to determine the provenance and role of estuarine processes on their distribution. Kaolinite and illite, followed by minor goethite, gibbsite and chlorite were present in SPM and bottom sediment at all stations, both during monsoon and pre-monsoon. Smectite occurred in traces at river end stations but its contents increased downstream in both estuaries. Smectite contents were much higher in Zuari than in Mandovi estuary. The 87Sr/86Sr ratios and ɛNd of SPM were higher than those in hinterland rocks and laterite soils. The Sr ratios were highest at river end stations of both estuaries and decreased sharply seaward. The Sm/Nd ratios of SPM and sediment were close to that of iron ore material flushed into the estuaries. The mean ɛNd of SPM and sediment were similar in both estuaries. It is suggested that the smectite is formed in coastal plains and its distribution downstream is controlled by lithology and drainage basin of rivers. Abundant kaolinite and high Sr ratios reflect chemical weathering and lateritization of source rocks. Sr isotopic ratios along transects are influenced by changes in salinity, organic matter and turbidity. High and near identical ɛNd values along transect stations of both estuaries suggest that the Nd isotopic compositions are influenced by the lateritization of source rocks and anthropogenic contribution of ore material.

  8. Plume-Lithosphere Interaction beneath the Snake River Plain, Idaho: Constraints from Pb, Sr, Nd, and Hf Isotopes

    NASA Astrophysics Data System (ADS)

    Jean, M. M.; Hanan, B. B.; Shervais, J. W.

    2011-12-01

    The Yellowstone-Snake River Plain (YSRP) volcanic province links 17 million years of volcanic activity that extends from the Owyhee Plateau in western Idaho/eastern Oregon to its current terminus underlying the Yellowstone Plateau. This investigation presents new Strontium, Neodymium, Lead, and Hafnium isotopic compositions of 25 basalts that represent four distinct areas of the YSRP (i.e., eastern province, central province, western province, Owyhee Plateau), which transect the ancient cratonic boundary of North America. The purpose of this study is to test and refine models for plume-lithosphere interaction and determines the mantle origin for YSRP basalts. New results shows: (1) low-K tholeiites from the eastern, central, and western SRP have ɛNd (-2 to -5.5), 87Sr/86Sr (0.7060-0.7071) and similar Pb-isotopes [206Pb/204Pb (17.8-18.6), 207Pb/204Pb (15.5-15.66), 208Pb/204Pb (38.4-39.1)]; (2) central SRP tholeiites are enriched in 208Pb/204Pb (~38.5-38.9), relative to eastern SRP basalts and define a 208Pb/204Pb trend, intermediate between the eastern SRP and Craters of the Moon lavas; (3) western SRP high-K basalts are depleted in ɛNd (> -1) and 87Sr/86Sr (0.7050-0.7057), relative to low-K tholeiites, and plot closer to "bulk silicate earth," but are enriched in 206Pb/204Pb (18.66-18.71), and have 207Pb/204Pb (15.62-15.65) and 208Pb/204Pb (39.1-39.2) isotope ratios similar to high-K basalts of Smith Prairie (Boise River Group 2); (4) Silver City basalt (>16.6 Ma) overlaps in Pb-isotope space with Imnaha basalt compositions (Columbia River Basalt Group); (5) new 177Hf/176Hf isotopic data lie above and parallel to the Mantle array in Nd and Hf isotope space and define a linear trend between Leucite Hills lavas and OIB basalts (i.e., Steens and Hawaii); (6) these basalts follow a systematic geographic pattern: eastern and central plain low-K tholeiites have low ɛNd (-3 to -5) and intermediate 206Pb/204Pb (~17.7-18.5), while western plain low-K tholeiites are

  9. A comparison of Sr-Nd-Pb isotopes in young and old continental lithospheric mantle: Patagonia and eastern China

    USGS Publications Warehouse

    Zartman, R.E.; Futa, K.; Peng, Z.C.

    1991-01-01

    It is commonly accepted that beneath the continental crust lies a keel of lithospheric mantle, which extends 50-200 kilometres downward to a transition zone into the asthenosphere. The chemical and physical properties of this reservoir are best known through studies of the basalts and xenoliths that provide samples of the subcrustal mantle. Although sharing many characteristics with oceanic island basalts, some continental basalts become increasingly distinct isotopically as crustal age increases, strongly supporting a permanent association between crust and mantle. Five models are discussed that relate the isotopic composition of the continental lithospheric mantle to that of other parts of the terrestrial system, which may be involved in its origin and evolution. The potential locations of the contribution components and the mechanisms and timing of their assembly into lithosphere are considered. -from Authors

  10. Elemental and Sr Nd isotopic systematics of the early Mesozoic volcanic sequence in southern Jiangxi Province, South China: petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Wang, Yuejun; Fan, Weiming; Peng, Touping; Guo, Feng

    2005-02-01

    Elemental and Sr Nd isotopic results are presented for the early Mesozoic volcanic sequence (~172 Ma) in southern Jiangxi Province, South China. The sequence is voluminously composed of ~45% subalkaline basaltic rocks (group 1), <5% high-mg andesite dacites (group 2) and ~50% rhyolites (group 3). The group 1 rocks are characterized by (La/Yb)cn = 3.8 7.2, Eu/Eu* = 0.65 1.15, Nb/La = 0.64 0.99, 87Sr/86Sr(t) = 0.70602~0.70822 and ɛNd(t) = -1.63 to +0.11, similar to those of an EMII-like source. The group 2 rocks have mg=0.42~0.60, SiO2=60.24~66.71%, MgO=2.65~ 5.54%, Ni=24~102 ppm and Cr=84~266 ppm, classified as high-mg andesitic rocks. These rocks are more enriched in LILEs and LREE with more significant negative Eu anomaly (0.63~0.79), are more depleted in HFSEs with Nb/La ratios of 0.40 0.56 and have lower ɛNd(t) (-9.44 to -7.78) and higher 87Sr/86Sr(t) (0.70985~0.71016), in comparison with the group 1 rocks. They most likely originated from metasomatised veins in the lithospheric mantle. The origination of the group 1 and group 2 magma suggests the development of a peridotite-plus-vein lithospheric mantle during early Mesozoic era beneath the interior of the Cathaysian block. The group 3 rhyolites are characterized by high SiO2 (72.75~77.97%), Zr (99~290 ppm), Hf (3.9~9.7 ppm) and Ga/Al (2.76~3.87) and significant Nb Ta, Ba Sr and P Ti depletions. These rhyolites exhibit Sr Nd isotopic compositions (87Sr/86Sr(t) = 0.70962~0.71104, ɛNd(t) = -4.63 to -5.80) similar to the contemporaneous Zhaibei and Pitou A-type granites in the area. Such characteristics suggest that they might be derived from the underplating basaltic magma contaminated by crustal materials. Therefore, an early Mesozoic rifting model in response to intracontinental lithospheric extension is proposed to account for the early Mesozoic volcanism in southern Jiangxi Province, South China.

  11. Geochronology, geochemistry and Sr-Nd-Pb isotopic constraints on the origin of the Qian’echong porphyry Mo deposit, Dabie orogen, east China

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Mao, Jingwen; Ye, Huishou; Li, Faling; Li, Yongfeng; Luo, Zhengzhuan; Xiong, Bikang; Meng, Fang

    2014-05-01

    The giant Qian’echong porphyry molybdenum deposit is located in the Dabie orogen, east China. The molybdenum mineralization mainly occurs as molybdenite-bearing quartz veins hosted by the Devonian Nanwan Formation in the external contact zone of the Qian’echong stock. The Qian’echong stock comprises an earlier formed monzogranite and a later formed granite porphyry. Sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb dating constrains the timing of crystallization of the monzogranite and granite porphyry to 130 ± 2 and 129 ± 2 Ma, respectively. The Re-Os model ages of six molybdenite samples range from 127.9 ± 1.9 to 129.7 ± 1.9 Ma with an isochron age of 129.4 ± 1.5 Ma, which are all consistent within errors with the zircon U-Pb ages, indicating an Early Cretaceous magmatic and mineralization event. The Qian’echong granites have moderate negative Eu anomalies and are relatively enriched in light rare earth elements (REE), but depleted in heavy REE, Y, and high field strength elements (HFSE; e.g., Nb, Ta, and Ti). The Qian’echong granites are I-type rather than A- or S-type, and they have high (87Sr/86Sr)i (0.706771-0.710326) and low ɛNd(t) (-25.5 to -16.8). Two-stage Nd model ages (T2DM) vary between 2.29 and 2.99 Ga. Sr-Nd-Pb isotopic data suggest that the Qian’echong granites were not derived from the North China Craton (NCC), but rather were generated from the Yangtze Craton (YC) lower crust. Paleoproterozoic inherited zircon age and whole-rock chemical and Sr-Nd-Pb isotopic data suggest that the Qian’echong granites were derived mainly from partial melting of ultrahigh pressure eclogites, with incorporation of some Paleoproterozoic to Archean YC crustal materials at lower crustal levels. Delamination or foundering of eclogitic lower crust, which extensively occurred in the Dabie orogen during the Early Cretaceous, had not taken place beneath the Qian’echong deposit when it formed. The Qian’echong molybdenum deposit formed in

  12. Multiple magma evolution and ore-forming processes of the Hongge layered intrusion, SW China: Insights from Sr-Nd isotopes, trace elements and platinum-group elements

    NASA Astrophysics Data System (ADS)

    Liao, Mingyang; Tao, Yan; Song, Xieyan; Li, Yubang; Xiong, Feng

    2015-12-01

    The Hongge layered intrusion (259 Ma), which is located in the inner zone of the Emeishan large igneous province (ELIP), is one of the most typical Fe-Ti-V ore deposits in the Pan-Xi area. Mafic-ultramafic layered intrusions of the ELIP have attracted a lot of attention lately because these intrusions host world class Fe-Ti-V oxide deposits plus interesting Cu-Ni-(PGE) mineralization which may have economic potential. This paper, reports new whole-rock major and trace element compositions, PGE abundances and Sr-Nd isotopic data for selected cumulate rocks and basalts. We use these data to investigate the nature of parental magmas and the controls on its evolution from the source mantle en route to the surface involving the Hongge ore-bearing intrusion. Two abrupt changes in Mt/Ilm and trace element ratios such as Ba/Th with depths in the Hongge layered intrusion indicate that this intrusion formed by at least two pluses of relatively primitive magma. The whole rock Sr-Nd isotopic data of basaltic and intrusive rocks plot in the region of Emeishan low-Ti basalts and the compositions of residual liquid (at ∼1260 °C and 1155 °C) calculated by MELTS are similar to our actual high-Ti (BFQ-2) and low-Ti (BC-1) basltic samples, indicate they are co-magmatic rather than derivation from a distinct source. Total PGE abundances in the Hongge samples are extremely low, ranging from 0.5 to 10 ppb. Sulfide-bearing rocks in the Hongge intrusion and the nearby coeval Banfangqing and Baicao basalts have similar mantle-like Pd/Pt ratios (2-6) and extremely high Cu/Pd ratios (3 × 104 to 4 × 105), indicating that sulfide segregation took place at depth prior to emplacement at Hongge and eruption in this region. Sulfide saturation in the Hongge magma may have resulted from such crustal contamination event. Crystallization of silicate minerals under the anhydrous magma, magma hydration plus Fe-Ti enrichments in the parental magma are three critical factors for the formation of Fe

  13. Pb-Sr-Nd isotopes in surficial materials at the Pebble Porphyry Cu-Au-Mo Deposit, Southwestern Alaska: can the mineralizing fingerprint be detected through cover?

    USGS Publications Warehouse

    Ayuso, Robert A.; Kelley, Karen D.; Eppinger, Robert G.; Forni, Francesca

    2013-01-01

    The Cretaceous Pebble porphyry Cu-Au-Mo deposit is covered by tundra and glacigenic sediments. Pb-Sr-Nd measurements were done on sediments and soils to establish baseline conditions prior to the onset of mining operations and contribute to the development of exploration methods for concealed base metal deposits of this type. Pebble rocks have a moderate range for 206Pb/204Pb = 18.574 to 18.874, 207Pb/204Pb = 15.484 to 15.526, and 208,Pb/204Pb = 38.053 to 38.266. Mineralized granodiorite shows a modest spread in 87Sr/86Sr (0.704354–0.707621) and 143Nd/144Nd (0.512639–0.512750). Age-corrected (89 Ma) values for the granodiorite yield relatively unradiogenic Pb (e.g., 207Pb/204Pb 87Sr/86Sr, and positive values of ɛNd (1.00–4.52) that attest to a major contribution of mantle-derived source rocks. Pond sediments and soils have similar Pb isotope signatures and 87Sr/86Sr and 143Nd/144Nd values that resemble the mineralized granodiorites. Glacial events have obscured the recognition of isotope signatures of mineralized rocks in the sediments and soils. Baseline radiogenic isotope compositions, prior to the onset of mining operations, reflect natural erosion, transport and deposition of heterogeneous till sheets that included debris from barren rocks, mineralized granodiorite and sulfides from the Pebble deposit, and other country rocks that pre- and postdate the mineralization events. Isotopic variations suggest that natural weathering of the deposit is generally reflected in these surficial materials. The isotope data provide geochemical constraints to glimpse through the extensive cover and together with other geochemical observations provide a vector to concealed mineralized rocks genetically linked with the Pebble deposit.

  14. Sr, Nd and Pb Isotope Geochemistry of Near-ridge Seamounts in Eastern Pacific: Implications for Upper Mantle Composition and EPR Magmatic Segmentation

    NASA Astrophysics Data System (ADS)

    Castillo, P. R.; White, W. M.; Batiza, R.

    2005-12-01

    Near-ridge seamount lavas tend to reflect the true composition of the upper mantle source of MORB because these are generated by relatively smaller degrees of melting of smaller volumes of the mantle compared to nearby axial lavas; they also by-pass the axial chamber mixing and fractionation processes that are responsible for the relatively more uniform chemical and isotopic composition of normal-MORB. New Sr, Nd and Pb isotope data combined with published data for lavas from near-ridge seamounts on either side of the EPR segment between the 11o45' OSC and Orozco Transform at 15o00' show latitudinal isotopic variation very similar to that shown by the rise axial lavas (Castillo et al., G3 1, 1999). Seamount and axial lavas at both ends of the rise segment have on average slightly higher and more limited range of 143Nd/144Nd, but slightly lower 206Pb/204Pb and 87Sr/86Sr ratios than lavas at the center of the segment. Some of the seamounts are located on ~8 Ma rise flank crust although most of the seamount lavas are fairly young (e.g., lavas from Seamount 6 on ~3 Ma crust are only 3 to 900 kyr - Graham et al., Nature 326, 1987). Thus near-ridge seamount isotope data provide the first documentation for a large-scale (~350 km long x ~720 km wide), systematic compositional variation of the upper mantle source of EPR MORB. Such a scale of variation is larger and longer than the size and <1 myr life span of the majority of non-transform offsets, which are supposed to be responsible for the along-axis compositional variations of EPR MORB according to the "bottoms up" model of magmatic segmentation.

  15. A hybrid origin for two Cretaceous monzonitic plutons in eastern Zhejiang Province, Southeast China: Geochronological, geochemical, and Sr-Nd-Hf isotopic evidence

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Qiu, Jian-Sheng; Zhao, Jiao-Long

    2016-01-01

    Monzonites can provide important information about the nature of the mantle sources and the mechanism of crust-mantle interactions. However, details on the origin of Late Mesozoic monzonites in the Southeastern China remain poorly constrained. This paper presents whole-rock geochemical, Sr-Nd isotopic and zircon U-Pb and Hf isotopic data for two monzonitic plutons (Huangtanyang and Kanggu) in eastern Zhejiang Province, with the aim of elucidating their petrogenesis, and providing important insights into the process of crust-mantle interaction. LA-ICP-MS zircon U-Pb dating results imply that the Huangtanyang and Kanggu quartz monzonites were emplaced in Cretaceous (104-109 Ma). All quartz monzonites are intermediate to acidic, metaluminous to weakly peraluminous, subalkaline, and K-rich in composition. They are enriched in large ion lithophile (e.g., Rb, Ba and Pb) and light rare earth elements, depleted in high-field strength elements (e.g., Nb, Ta, and Ti), and show weakly negative or no Eu anomalies (δEu = 0.78-1.02). All quartz monzonites have homogeneous initial ISr values (0.7084-0.7090) and εNd(t) values (-7.50 to -6.84). They are characterised by highly variable zircon Hf isotopic compositions, with εHf(t) values ranging from -13.3 to -5.7. The combined geochemical evidences (such as high Mg# values, low Nb/U and Ta/U ratios, and variable zircon Hf isotopic compositions) suggests that both depleted asthenospheric and metasomatically enriched mantle components were involved in the formation of the monzonites. The existence of some zircons with unusually low εHf(t) values (low to -13.3) and Palaeoproterozoic two-stage Hf model ages from the Huangtanyang and Kanggu quartz monzonites also argues strongly for Palaeoproterozoic crustal involvement. Magma mixing played a dominated role in the genesis of these monzonites, as indicated by their wide range in zircon Hf isotopic compositions and the occurrence of mafic microgranular enclaves (MMEs). The MMEs show

  16. Clinopyroxene-host disequilibrium (Sr-Nd-Pb isotope systematics) in ultra-potassic magmas from East-African Rift: Implications for magma mixing and source heterogeneity

    NASA Astrophysics Data System (ADS)

    Muravyeva, Natalya; Belyatsky, Boris; Senin, Valeriy

    2014-05-01

    Nd, Pb and Sr isotope ratios have been determined for kamafugite lava and clinopyroxene and phlogopite phenocrysts from Toro-Ankole and Virunga volcanic fields of the East African Rift. The whole rock Sr - Nd isotopic signatures of kamafugites (87Sr/86Sr: 0.70463 - 0.70536; 143Nd/144Nd: 0.51249 - 0.51255) suggest derivation from an EM1-type mantle source. In contrast, Pb isotopic compositions of the same samples (206Pb/204Pb: 19.00 - 19.57; 207Pb/204Pb: 15.69 - 15.74; 208Pb/204Pb: 39.30 - 40.26) reveal a similarity to EM2-type mantle. New Nd, Pb and Sr isotopic data for clinopyroxene (87Sr/86Sr: 0.70473 - 0.70503; 143Nd/144Nd: 0.51250 - 0.51254; 206Pb/204Pb: 18.04 - 18.17; 207Pb/204Pb: 15.58 - 15.60; 208Pb/204Pb: 38.09 - 38.23) suggest derivation from an EM1-like source, and indicate Sr and Pb isotope disequilibrium between clinopyroxene and corresponding host rock. Moreover, clinopyroxenes demonstrating a greater degree of isotopic disequilibrium with their host rock are more sodic in composition. The isotopic disequilibrium is corroborated by the presence of chemical zoning within clinopyroxene, which suggests rapid magma ascent rates preventing melt homogenization. The Pb isotopic ratios for both mineral and corresponding whole rock, together with published data on East African rift-related alkaline centers, define a trend interpreted to represent a mixing line for melts derived from sources such as EM1 and as HIMU. The similar isotopic compositions for clinopyroxene from the different volcanic rocks within the East African Rift suggest the existence of a common, older mantle source for their parental melts. The origin of these melts can be attributed to an enrichment event ~ 400-500 Ma, i.e., significantly prior the younger (Quaternary) ultrapotassic magmatism. Our preferred interpretation for the results reported here involves the mixing of the melts derived from EM1- and HIMU-like sources, which were rapidly transported to the Earth's surface. The primary

  17. 40Ar/39Ar ages and Sr-Nd-Pb isotopic compositions of alkaline and tholeiitic rocks from the northern Deccan Traps

    NASA Astrophysics Data System (ADS)

    Marzoli, A.; Parisio, L.; Jourdan, F.; Melluso, L.; Sethna, S. F.; Bellieni, G.

    2015-12-01

    The Deccan large igneous province in India was emplaced close to the Cretaceous-Paleogene boundary (K-Pg; 66.0 Ma) and is formed by tholeiitic and alkaline rocks. Definition of the origin of Deccan magmatism and of its environmental impact relies on precise and accurate geochronological analyses. We present new 40Ar/39Ar ages from the northern sector of the province. In this area, tholeiitic and alkaline rocks were contemporaneously emplaced at 66.60±0.35 to 65.25±0.29 Ma in the Phenai Mata area, while rocks from Rajpipla and Mt. Pavagadh yielded ages ranging from 66.40±2.80 to 64.90±0.80 Ma. Indistinguishable ages for alkaline and tholeiitic magmatism, coupled with distinct major and trace element and Sr-Nd-Pb isotopic compositions suggest that distinct mantle sources, necessary for the two magmatic series were synchronously active. The new ages are compared with previous ages, which were carefully screened and filtered and then recalculated in order to be comparable. The entire data set of geochronological data does not support a time-related migration of the magmatism related to the northward Indian Plate movement relative to the Reunion mantle plume. The main phase of magmatism, including the newly dated rocks from the Northern Deccan occurred across the K-Pg boundary, confirming a causal link between the emplacement of the province and the K-Pg mass extinction.

  18. Sr-Nd isotopic variations in the 4,965 yr BP "Ochre Pumice" plinian fallout of Popocatépetl: Preliminary results and interpretation

    NASA Astrophysics Data System (ADS)

    Orsi, G.; Arana-Salinas, L.; Civetta, L.; Siebe, C.

    2013-05-01

    becomes more silicic towards the top (SiO2 = 63 wt.%). Pumice clasts have a crystallinity index that ranges between 10 and 25 Vol.% and display a seriate texture. Phenocrysts of plagioclase are the most abundant phase and typically display labradoritic cores (An54-59) and andesine rims (An41-46). Augites (En40-44 Wo41-45) and hypersthenes (En66-40) are less common, occur either isolated or in clusters with plagioclase and/or olivine. Ol-crystals are slightly zoned with forsteritic core compositions (Fo65-Fo84). Apatite and opaques occur subordinately. This study aims to determine systematically the Sr-Nd isotopic ratios in the different layers that compose the plinian "Ochre pumice" fallout sequence in order to make inferences regarding magmatic processes (mafic injection, mixing, mingling, etc.) prior to eruption. Preliminary results and interpretations will be presented.

  19. U, Th and Ra disequilibria, Sr, Nd and Pb isotope and trace element variations in Sunda arc lavas: predominance of a subducted sediment component

    NASA Astrophysics Data System (ADS)

    Turner, S.; Foden, J.

    The time scales of magma formation, transfer and storage beneath island arc volcanoes are important because of the insights they provide into the physical processes of magma formation and evolution with possible links to the prediction of eruptive hazards. Here we present new mass spectrometric U, Th and Ra, and Sr, Nd and Pb isotope data, along with major and trace element data, from 19 lavas along the Sunda arc, Indonesia. The lavas range in SiO2 from 49 to 75% and the combination of high SiO2 and low 143Nd/144Nd indicates an important role for shallow-level contamination by ancient crustal materials in Sumatra. Diagrams of 143Nd/144Nd versus Th/Ce and U/Th versus 87Sr/86Sr reveal negative trends which allow contributions from both subducted sediments and fluids to be identified. The fluid component as expressed in elevated U/Th, (238U/230Th) and (226Ra/230Th)o ratios is ubiquitous in all of the lavas including near primary lavas from Galunggung. Sr isotope data indicate that the fluids had variable composition and derived from altered oceanic crust, and the U, Th and Ra isotope data suggest that some fluid components must have been added less than 8,000 years ago. Tholeiitic lavas from Flores have the lowest Th contents in the arc and accordingly the highest (226Ra/230Th)o and (238U/230Th). For these there is evidence that both U and Ra addition probably occurred less than a few thousand years ago. This suggests that the onset of melting was linked to fluid fluxing and cannot have been due to decompression alone. In contrast, the sediment component may have been added as a partial melt and sediment addition can account for the observed along-arc variations in Sr, Nd, Pb and Th isotopes. There is no requirement in our data for an OIB component in the mantle wedge. Increases in SiO2 in the Galunggung lavas are accompanied by decreases in both (238U/230Th) and (226Ra/230Th)o, which are inferred to reflect mixing with melts of pre-existing mafic lavas. Mixing and

  20. The significance of PGE variations with Sr-Nd isotopes and lithophile elements in the Emeishan flood basalt province from SW China to northern Vietnam

    NASA Astrophysics Data System (ADS)

    Li, Chusi; Ripley, Edward M.; Tao, Yan; Hu, Ruizhong

    2016-04-01

    New analyses of siderophile-lithophile elements and Sr-Nd isotopes in the Permian basalts and picrites from northern Vietnam, the southernmost occurrence of the Emeishan flood basalt province, together with previously published data, are used to address the question of whether any meaningful correlation between these elements and isotopes exists at a province scale. The available data show that negative correlations between εNd, (87Sr/86Sr)i and mantle-normalized (Nb/Th)n are present in the basalts but not in the associated picrites. This indicates that crustal contamination is negligible in the picrites but significant in some of the basalts. The picrites and basalts from the entire province show negative correlations between (Rh/Ru)n, (Pt/Ru)n, (Pd/Ru)n and Mg-number. This indicates that Ru behaves compatibly whereas Rh, Pt and Pd behave incompatibly during magma differentiation. The incompatible behavior of Rh in natural basaltic systems is also supported by the fact that (Pt/Rh)n remains constant with decreasing Mg-number in the lavas. Depletions of Pd and Pt, and to a lesser degree Cu, in some basaltic samples characterized by relatively low εNd and (Nb/Th)n support the notion that sulfide saturation in the magmas was triggered by a combination of siliceous crustal contamination and addition of external sulfur. Within the entire flood basalt province only the picrites from Song Da, northern Vietnam show clear depletion in Ir relative to Ru. These picrites are also characterized higher Al2O3/TiO2 and lower mantle-normalized La/Yb (0.2-2.4) than those from elsewhere in the province, possibly due to the involvement of an Ir-depleted, fertile mantle component in magma generation at this location.

  1. New petrological constraints on the last eruptive phase of the Sabatini Volcanic District (central Italy): Clues from mineralogy, geochemistry, and Sr-Nd isotopes

    NASA Astrophysics Data System (ADS)

    Del Bello, Elisabetta; Mollo, Silvio; Scarlato, Piergiorgio; von Quadt, Albrecht; Forni, Francesca; Bachmann, Olivier

    2014-09-01

    We report results from mineralogical, geochemical and isotopic analyses of the three youngest pyroclastic products (ca. 86 ky) belonging to the Sabatini Volcanic District (Roman Province, central Italy). By means of thermometers, hygrometers and oxygen barometers, we have estimated that the crystallization temperature of magma progressively decreases over time (910-740 °C), whereas the amount of water dissolved in the melt and fO2 progressively increases as compositions of magmas become more differentiated (4.5-6.4 wt.% H2O and 0.4-2.6 ΔQFM buffer, respectively). Thermodynamic simulations of phase equilibria indicate that geochemical trends in mafic magmas (MgO > 4 wt.%) can be reproduced by abundant fractionation of olivine and clinopyroxene (~ 50 wt.% crystallization), while the trends of more evolved magmas (MgO ≤ 4 wt.%) originated by fractional crystallization of plagioclase and sanidine (~ 45 wt.% crystallization). The behavior of trace elements highlights that magmatic differentiation is controlled by polybaric differentiation that includes: (1) prolonged fractionation of mafic, anhydrous minerals from a primitive, H2O-poor magma at depth and (2) extraction of a more evolved, H2O-rich magma that crystallizes abundant felsic and subordinated hydrous minerals at shallow crustal levels. Assimilation and fractional crystallization modeling also reveal that magmas interacted with the carbonate rocks of the subvolcanic basement. The effect of carbonate assimilation accounts for both trace element and Sr-Nd isotopic variations in magmas, suggesting a maximum degree of carbonate assimilation of less than 5 wt.%.

  2. Geochemical and Sr-Nd-Pb-Os isotopic compositions of Miocene ultrapotassic rocks in southern Tibet: Petrogenesis and implications for the regional tectonic history

    NASA Astrophysics Data System (ADS)

    Wang, BaoDi; Chen, JianLin; Xu, JiFeng; Wang, LiQuan

    2014-11-01

    Ultrapotassic lavas are widespread throughout southern Tibet and are generally thought to have formed from magmas generated by partial melting of an enriched mantle source that was metasomatized during earlier subduction events. Here, we report new geochemical and Sr-Nd-Pb-Os isotope data for Miocene ultrapotassic rocks within the Sailipu area of the western Lhasa terrane, southern Tibet. The Sailipu ultrapotassic rocks are enriched in the large ion lithophile elements relative to the high field strength elements, and have extremely radiogenic Sr (87Sr/86Sr(i) = 0.714480-0.727323), Pb (206Pb/204Pb = 18.414-18.787, 207Pb/204Pb = 15.693-15.749, 208Pb/204Pb = 39.439-39.765), and Os isotopic signatures (187Os/188Os(i) = 0.1095-0.37454), and unradiogenic Nd (εNd(t) = - 11.5 to - 15.2) isotopic compositions. These geochemical and isotopic characteristics, coupled with high K2O (> 5 wt.%) and MgO (5.20-13.70 wt.%) concentrations, Mg# values of 68-76, high Rb/Sr (0.13-0.95) and low Ba/Rb (3.33-12.3) ratios, and the relatively low Os contents and radiogenic Os isotopic compositions of the Sailipu ultrapotassic rocks, do not support any significant crustal contamination. Instead, we consider these rocks to be analogous to the Cenozoic ultrapotassic rocks from Italy and the Balkans, suggesting that they were produced by interaction between melts derived from phlogopite-rich clinopyroxene veins and surrounding peridotitic mantle material. The Sailipu ultrapotassic rocks can be divided into type-1 and type-2 suites based on differences in major and trace element concentrations, and isotopic compositions. Type-1 ultrapotassic rocks are relatively enriched in the heavy rare earth elements, most likely as a result of interaction between melts derived from phlogopite-rich clinopyroxene veins and the surrounding spinel-bearing peridotite material, whereas the type-2 rocks are enriched in rare earth elements and have high (Gd/Yb)N values (8.3-12.2), both of which are indicative of

  3. Multiple S isotopes, zircon Hf isotopes, whole-rock Sr-Nd isotopes, and spatial variations of PGE tenors in the Jinchuan Ni-Cu-PGE deposit, NW China

    NASA Astrophysics Data System (ADS)

    Duan, Jun; Li, Chusi; Qian, Zhuangzhi; Jiao, Jiangang; Ripley, Edward M.; Feng, Yanqing

    2016-04-01

    Previous geochemical data for the Jinchuan Ni-Cu-(platinum-group elements, PGE) deposit, the single largest magmatic sulfide deposit in the world, are derived primarily from the upper parts of the deposit. This paper reports new PGE and S-Hf-Sr-Nd isotope data for the lower parts of the deposit that have become accessible for sampling by ongoing underground mining activity. New PGE data from this study, together with previous results, indicate that PGE tenors in the bulk sulfide ores of the deposit increase eastward, except for two fault-offset ore zones which occur together within the western part of the deposit. Generally, these two ore zones show depletions in IPGE (Ir, Ru, Rh) but not in PPGE (Pt, Pd) and Cu, and more fractionated olivine and Cr-spinel compositions than the rest of the deposit. These differences can be explained by a more evolved parental magma for the IPGE-depleted ore zones. The eastward increase of PGE tenors in the rest of the deposit can be explained by upgrading of preexisting sulfide liquid in a subhorizontal conduit by a new surge of magma moving through the conduit from west to east, which took place before the formation of the IPGE-depleted ore zones. The Jinchuan ultramafic rocks are characterized by elevated initial 87Sr/86Sr ratios from 0.7077 to 0.7093, negative ɛ Nd values from -9.2 to -10.5, and zircon ɛ Hf values from -4 to -7. These data indicate up to 20 % of crustal contamination in the Jinchuan magma. Four of nine multiple sulfur isotope analyses for the Jinchuan deposit show anomalous ∆33S values varying from 0.12 to 2.67 ‰. These results, together with elevated δ34S values (>2 ‰) for some of the samples analyzed previously by other researchers, indicate the involvement of external sulfur from Archean and Proterozoic sedimentary rocks. Modeling results based on our olivine data and magma compositions estimated previously by other researchers indicate that fractional crystallization did not play a major role in

  4. Sr, Nd and Pb isotopes in Proterozoic intrusives astride the Grenville Front in Labrador: Implications for crustal contamination and basement mapping

    USGS Publications Warehouse

    Ashwal, L.D.; Wooden, J.L.; Emslie, R.F.

    1986-01-01

    We report Sr, Nd and Pb isotopic compositions of mid-Proterozoic anorthosites and related rocks (1.45-1.65 Ga) and of younger olivine diabase dikes (1.4 Ga) from two complexes on either side of the Grenville Front in Labrador. Anorthositic or diabasic samples from the Mealy Mountains (Grenville Province) and Harp Lake (Nain-Churchill Provinces) complexes have very similar major, minor and trace element compositions, but distinctly different isotopic signatures. All Mealy Mountains samples have ISr = 0.7025-0.7033, ??{lunate}Nd = +0.6 to +5.6 and Pb isotopic compositions consistent with derivation from a mantle source depleted with respect to Nd/Sm and Rb/Sr. Pb isotopic compositions for the Mealy Mountains samples are slightly more radiogenic than model mantle compositions. All Harp Lake samples have ISr = 0.7032-0.7066, ??{lunate}Nd = -0.3 to -4.4 and variable, but generally unradiogenic 207Pb 204Pb and 206Pb 204Pb compared to model mantle, suggesting mixing between a mantle-derived component and a U-depleted crustal contaminant. Crustal contaminants are probably a variety of Archean high-grade quartzofeldspathic gneisses with low U/Pb ratios and include a component that must be isotopically similar to the early Archean (>3.6 Ga) Uivak gneisses of Labrador or the Amitsoq gneisses of west Greenland. This would imply that the ancient gneiss complex of coastal Labrador and Greenland is larger than indicated by present surface exposure and may extend in the subsurface as far west as the Labrador Trough. If Harp Lake and Mealy Mountains samples were subjected to the same degree of contamination, as suggested by their chemical similarities, then the Mealy contaminants must be much younger, probably early or middle Proterozoic in age. The Labrador segment of the Grenville Front, therefore, appears to coincide with the southern margin of the Archean North Atlantic craton and may represent a pre mid-Proterozoic suture. ?? 1986.

  5. O-, Sr-, Nd-isotope, and trace element relationships in lavas from Mount Shasta in northern California

    SciTech Connect

    Mertzman, S.A.; Savin, S.M.

    1985-01-01

    If subducted oceanic material is involved in the genesis of lavas in island arc and continental margin tectonic settings, its influence on the chemical and isotopic composition of orogenic volcanic rocks ought to be greatest on the oceanic side of the arc. Andesites and dacites (58-66% SiO/sub 2/) from Mt. Shasta, the westernmost large composite volcano in the California segment of the Cascade volcanic belt, are characterized by a concave downward curve on a /sup 143/Nd//sup 144/Nd-/sup 87/Sr//sup 86/Sr diagram. This trend begins at 0.70285 and 0.51300 and terminates near 0.70397 and 0.51280 respectively. The shape of the curve, being slightly displaced to the left of the mantle array, precludes involvement of altered oceanic crust in the generation of Shasta andesites and dacties. delta /sup 18/O data concerning these same silicic extrusives range from +7 to +9 per thousands values clearly higher than most orogenic andesites and seemingly incompatible with a mantle source without significant modification. A delta /sup 18/O-/sup 87/Sr//sup 86/Sr diagram of this data produces a curve with some scatter that is convex upward, suggesting crustal contamination with deep-sea or geosynclinal sediments as the causative process. Hf-Ta-Th data are in agreement with this suggestion; however, preliminary Pb isotope data on these silicic lavas is ambiguous. O-, Sr-, and Nd-isotope data from concurrently erupted basalts in the Shasta region clearly indicate they are not parental to any of the andesites or dacites extruded at this volcano.

  6. Geochemical and Sr-Nd isotopic constraints on the petrogenesis of late Cenozoic basalts from the Abaga area, Inner Mongolia, eastern China

    NASA Astrophysics Data System (ADS)

    Chen, Sheng-Sheng; Fan, Qi-Cheng; Zou, Hai-Bo; Zhao, Yong-Wei; Shi, Ren-Deng

    2015-10-01

    Over the past 30 years, the Cenozoic basalts in eastern China have been the subject of many investigations, but their origin remains highly controversial. The Abaga-Dalinuoer volcanic field in Inner Mongolia consists of an approximately 10,000 km2 lava plateau and more than 300 volcanic cones and extends northwestward to the adjacent Dariganga lava plateau of Mongolia, forming one of the largest Cenozoic volcanic fields in eastern Asia. In this paper, we concentrate on the Abaga volcanic field that comprises more than 200 monogenetic cones, including scoria cones, lava flows, and maars. Phreatomagmatism has contributed to the generation of several volcanic edifices, and the diameter of the maars craters can reach 3 to 6 km, which are among the largest in eastern China. The volcanic rocks in the Abaga area can be divided into alkaline basalts and tholeiites. According to trace element and Sr-Nd isotopic characteristics, the Abaga magmas were primarily derived from a relatively homogeneous garnet peridotite source within the asthenosphere. Variable degrees and depths of partial melting played a key role in the genesis of magma from alkaline basalts to tholeiites. In contrast to the surrounding Cenozoic volcanic fields, such as Datong, Jining, and Hanuoba, in the western block of the North China Craton, the Abaga volcanic region in the southern part of the Central Asian Orogenic Belt is distinguished by the deepest melting and the thickest lithosphere. Negative Ba-, Rb-, K-, and Ti anomalies and relatively high 87Sr/86Sr ratios suggest the presence of residual phlogopite/amphibole during mantle melting. The origin of the Abaga magma most likely required involvement of fluids released from the stagnant Pacific slab in the mantle transition zone.

  7. Midcontinent rift volcanism in the Lake Superior region: Sr, Nd, and Pb isotopic evidence for a mantle plume origin

    USGS Publications Warehouse

    Nicholson, S.W.; Shirey, S.B.

    1990-01-01

    Between 1091 and 1098 Ma, most of a 15- to 20-km thickness of dominantly tholeiitic basalt erupted in the Midcontinent Rift System of the Lake Superior region, North America. The Portage Lake Volcanics in Michigan, which are the younget MRS flood basalts, fall into distinctly high- and low-TiO2 types having different liquid lines of descent. Incompatible trace elements in both types of tholeiites are enriched compared to depleted or primitive mantle and both basalt types are isotopically indistinguishable. The isotopic enrichment of the MRS source compared to depleted mantle is striking and must have occurred at least 700 m.y. before 1100 Ma. There are two likely sources for such magmatism: subcontinental lithospheric mantle enriched during the early Proterozoic or enriched mantle derived from an upwelling plume. Decompression melting of an upwelling enriched mantle plume in a region of lithosphere thinned by extension could have successfully generated the enormous volume (850 ?? 103 km3) of relatively homogeneous magma in a restricted time interval. -from Authors

  8. New data on genesis of the crust in the eastern segment of the Middle Urals: Sr-Nd isotopic constraints

    NASA Astrophysics Data System (ADS)

    Smirnov, V. N.; Ronkin, Yu. L.; Puchkov, V. N.; Soloshenko, N. G.; Streletskaya, M. V.

    2016-04-01

    The analysis of the Sr and Nd isotopic composition in different granitoids of the Verkhisetsk, Shartash, Krasnopolsk, Petrokamensk, and Shabry massifs, which were successively formed in the island arc, continental marginal, and collisional geodynamic settings during the period from the Middle Devonian to the early Permian, revealed that 87Sr/86Sr0 values in them vary from 0.70331 to 0.70431 and ɛNd( t), from +1.9 to +6.2. The two-stage model Nd age of granitoids (938-629 Ma) indicates that their magma originates from material at least Neoproterozoic in age, not younger. The observed variations in the Nd model ages of granitoids and 87Sr/86Sr0 values provide grounds for assuming the primary heterogeneity of the source of granitoid melts.

  9. Sr-Nd-Pb Isotopic Signatures of High-Ti Basalts From the Pacific Rivera Plate, Western Margin of Mexico.

    NASA Astrophysics Data System (ADS)

    Schaaf, P.; Bandy, W. L.; Mortera, C.; Canet, C.

    2008-12-01

    Knowledge of the chemical and isotopic composition of ocean floor basalts is crucial for petrogenetic modeling of continental arc magmas. However, for Mexico few information is available, which was primarily that obtained from the DSDP perforations front of Acapulco and in the mouth of the Gulf of California. In this contribution we present new geochemical and geochronological analyses of Mid Ocean Ridge basalts, dredged at a depth of approx 2.800 m, offshore Manzanillo. The sampled area lies at the southeastern edge of the Rivera Plate close to its poorly defined boundary with the Cocos Plate and the Middle America Trench. Hand sized pillow fragments are glass-free and characterized by a fresh interior zone with porphyritic texture and a slightly more altered outer rim. Four tholeiitic samples were analyzed. Two generations of olivine phenocrysts were observed. Large grains without chrome spinel and smaller grains with chrome spinel and other inclusions. Both occur together with microphenocrysts of uninverted (monoclinic) pidgeonite and plagioclase (An60-80) in the fresh interior zone whereas the outer rim zone shows more alterated olivines, smectite, and secondary carbonates in vesicles. SiO2 contents are between 48.6 and 50.5 wt.% and TiO2 is substantially elevated with 2.5 to 3.9 wt.%. On the other hand, MgO is heterogeneous at relatively low levels (3.2 to 6.2 wt.%; Mg # 32-45). 87Sr/86Sr and epsilon Nd values are quite homogeneous with MORB-like ratios of 0.7025 and +11.8, respectively. Pb isotopic ratios, on the other hand, are somewhat lower than typical Pacific MORB values but lie well in the depleted mantle field. Within error, consistently young 39Ar/40Ar ages of 1.3 +/- 0.3 Ma and 1.4 +/- 0.7 Ma were obtained from the interior zone and the outer rim. More than 99% of the Ar was of atmospheric origin, which was responsible for the relatively large errors. Our high-Ti basalts are best interpreted as resulting from a propagating rift magmatism, probably as

  10. Sr-Nd isotopes constrain on the deposit history of the basins in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Li, Y.; Jiang, S.

    2015-12-01

    The Brazos-Trinity Basin IV and Ursa Basin are situated on the northern slope of the Gulf of Mexico. The Ursa basin lies in the center of late Pleistocene Mississippi River deposition, received the sediment deposition during Marine Isotope Stage (MIS) 2- 4. The Brazos-Trinity Basin IV belongs to a part of the Brazos-Trinity fan, it recorded the turbidite deposition and hemiplegic deposition during MIS1- 5. The Sr and Nd isotopic composition of the detrital composition of the sediment in both basins indicates the change of the sediment provenance during the basin-filled process. In the Ursa basin, The difference of 87Sr/86Sr ratio and ɛNd of the detrital component between MIS1,2 (87Sr/86Sr ~ 0.7219 - 0.7321, ɛNd ~ -12 - -13.4) and MIS3,4(87Sr/86Sr ~ 0.7310 - 0.7354, ɛNd ~ -16 - -17.9) is suggested to be related with the provenance change of the detrital particles since LGM. The addition of detrital particle from Appalachians with less radiogenic 87Sr/86Sr and positive ɛNd altered the character of the sediment of the Mississippi River during the last glaciation and deglaciation. In the Brazos-Trinity Basin IV, the narrow range of 87Sr/86Sr and ɛNd indicate that the sediment source of Brazos-Trinity Basin IV had not changed obviously during MIS5e to MIS2, mostly from coastal rivers such as Brazos River, Trinity River and Sabine River. The pre-fan with 87Sr/86Sr ~0.735 and ɛNd ~ -14.5 to -16.9, which is very similar to the deep sediment in the Ursa Basin with 87Sr/86Sr ~0.733 to 0.735 and ɛNd ~ -16 to -18. It is suggested that sediments of the pre-fan of the Brazos-Trinity Basin IV were supplied from the ancestral Mississippi River Delta during the low sea level (MIS 6). During the MIS5, the discharge of Mississippi River is thought switched to its present course, ~300 km to the east.

  11. Sr-Nd-Pb isotopic compositions of the lower crust beneath northern Tarim: insights from igneous rocks in the Kuluketage area, NW China

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Wei, Xun; Xu, Yi-Gang; Long, Xiao-Ping; Shi, Xue-Fa; Zhao, Jian-Xin; Feng, Yue-Xing

    2016-09-01

    The composition of lower crust of the Tarim Craton in NW China is essential to understand the petrogenesis of the ~290-275 Ma Tarim basalts and associated intermediate-felsic rocks. However, it remains poorly constrained because extremely sparse granulite terrains or granulite xenoliths have been found in the Tarim Craton. New trace element and Sr-Nd-Pb isotopic data are reported for the Neoarchean and Neoproterozoic igneous rocks widely distributed in the northern margin of the Tarim Craton. The Neoarchean granitic gneisses show fractionated REE (rare earth element) patterns [(La/Yb) N = 12-58, YbN = 10.6-36] with pronounced negative Nb-Ta and Ti anomalies. These features, together with negative ɛNdi (-0.7 to -3.2) suggest that they were derived from melting of mafic lower crust. The Neoproterozoic biotite granodiorites are strongly depleted in HREE with (La/Yb) N up to 55. They are characterized by high Sr (671-789 ppm) but very low Y (7.10-8.06 ppm) and Yb contents (0.47-0.58 ppm), showing typical features of adakitic rocks. The samples with different SiO2 contents display identical 87Sr/86Sri (0.7101-0.7103), ɛNdi (-14.1 to -15.7) and Pb isotopes (208Pb/204Pbi = 36.94-37.07). These features together with arc-like trace element patterns suggest that they were derived from melting of thickened lower crust. In comparison, the Neoproterozoic hornblende-biotite granodiorites have similar trace element compositions except for weaker depletion in HREE and have lower 87Sr/86Sri (0.7078) and initial Pb isotopes, and higher ɛNdi (-12.3 to -12.7). This suggests that they were formed by melting of old lower continental crust at a shallower depth than the biotite granodiorites. These rocks were derived from the lower crust, thus providing valuable information on the nature of the lower crust beneath northern Tarim. Combined with published data, the 87Sr/86Sri, ɛNdi, 206Pb/204Pbi and ɛHfi of the northern Tarim lower crust ranges from 0.7055 to 0.7103, from -12 to -17

  12. Sources of granite magmatism in the Embu Terrane (Ribeira Belt, Brazil): Neoproterozoic crust recycling constrained by elemental and isotope (Sr-Nd-Pb) geochemistry

    NASA Astrophysics Data System (ADS)

    Alves, Adriana; Janasi, Valdecir de Assis; Campos Neto, Mario da Costa

    2016-07-01

    Whole rock elemental and Sr-Nd isotope geochemistry and in situ K-feldspar Pb isotope geochemistry were used to identify the sources involved in the genesis of Neoproterozoic granites from the Embu Terrane, Ribeira Belt, SE Brazil. Granite magmatism spanned over 200 Ma (810-580 Ma), and is dominated by crust-derived relatively low-T (850-750 °C, zircon saturation) biotite granites to biotite-muscovite granites. Two Cryogenian plutons show the least negative εNdt (-8 to -10) and highest mg# (30-40) of the whole set. Their compositions are strongly contrasted, implying distinct sources for the peraluminous (ASI ∼ 1.2) ∼660 Ma Serra do Quebra-Cangalha batholith (metasedimentary rocks from relatively young upper crust with high Rb/Sr and low Th/U) and the metaluminous (ASI = 0.96-1.00) ∼ 630 Ma Santa Catarina Granite. Although not typical, the geochemical signature of these granites may reflect a continental margin arc environment, and they could be products of a prolonged period of oceanic plate consumption started at ∼810 Ma. The predominant Ediacaran (595-580 Ma) plutons have a spread of compositions from biotite granites with SiO2 as low as ∼65% (e.g., Itapeti, Mauá, Sabaúna and Lagoinha granites) to fractionated muscovite granites (Mogi das Cruzes, Santa Branca and Guacuri granites; up to ∼75% SiO2). εNdT are characteristically negative (-12 to -18), with corresponding Nd TDM indicating sources with Paleoproterozoic mean crustal ages (2.0-2.5 Ga). The Guacuri and Santa Branca muscovite granites have the more negative εNdt, highest 87Sr/86Srt (0.714-0.717) and lowest 208Pb/206Pb and 207Pb/206Pb, consistent with an old metasedimentary source with low time-integrated Rb/Sr. However, a positive Nd-Sr isotope correlation is suggested by data from the other granites, and would be consistent with mixing between an older source predominant in the Mauá granite and a younger, high Rb/Sr source that is more abundant in the Lagoinha granite sample. The

  13. Geochemical and Sr-Nd isotopic constraints on the mantle source of Neoproterozoic mafic dikes of the rifted eastern Laurentian margin, north-central Appalachians, USA

    NASA Astrophysics Data System (ADS)

    Volkert, Richard A.; Feigenson, Mark D.; Mana, Sara; Bolge, Louise

    2015-01-01

    Abundant and widely distributed unmetamorphosed mafic dikes intrude Mesoproterozoic rocks of the New Jersey Highlands. The age of the dikes is imprecisely known but interpreted to fall between 615 and 576 Ma, which is consistent with the range of ages of mafic dikes from Labrador and Nova Scotia south to Pennsylvania that were emplaced along the rifted eastern Laurentian margin. New Jersey Highlands dikes are a few cm to 18 m wide and have lengths of as much as several km. They have sharp, largely discordant contacts against enclosing Mesoproterozoic rocks and aphanitic chilled margins that grade into coarser grained interiors. Columnar joints are present locally and suggest emplacement at a shallow crustal level. Geochemical compositions of the dikes range from alkalic to less common tholeiitic basalt having generally high TiO2, P2O5, Zr, Nb, Y, and La/Yb, and low MgO, Cr, and Ni. TiO2 contents define high-Ti and low-Ti dikes that differ in high field strength elements (HFSE) and light rare earth elements (LREE) but overlap in abundances of most other elements. Dike magma evolved in an ascending mantle plume of OIB-like asthenosphere from enriched higher TiO2 compositions to more depleted lower TiO2 compositions. Subtle differences in the dike compositions are due to variations in the amount of partial melting within the plume and the depth of melt segregation. Sr-Nd isotope values of both dike compositions overlap and are characterized by εNd (T) of + 1.5 to + 3.8 and initial 87Sr/86Sr ranging from 0.7032 to 0.7077. Higher Sr isotope ratios are interpreted as resulting from local interaction of the dike magma with heterogeneous, high 87Sr/86Sr lithospheric mantle having EMI or EMII-like geochemical characteristics. Dikes form tabular structures that have long segments striking an average of N44°E and short segments striking about east-west. Their regional geometries form right-stepping, rhomb-shaped patterns due to emplacement into rift-related dilational

  14. Zircon U-Pb geochronology, geochemistry, and Sr-Nd-Hf isotopes of granitoids in the Yulekenhalasu copper ore district, northern Junggar, China: Petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Yang, Fuquan; Chai, Fengmei; Zhang, Zhixin; Geng, Xinxia; Li, Qiang

    2014-03-01

    The Yulekenhalasu porphyry copper deposit is located in the Kalaxiange'er metallogenic belt in northern Junggar, China. We present the results from zircon U-Pb geochronology, and geochemical and Sr-Nd-Hf isotope analyses of the granitoids associated with the ore deposits with a view to constrain their petrogenesis and tectonic setting. The granitoids consist of quartz diorite, diorite porphyry, porphyritic monzonite, and quartz porphyry, emplaced at 382, 379, 375-374, and 348 Ma, respectively, which span Late Devonian to early Carboniferous ages. The ore-bearing intrusion is mainly diorite porphyry, with subordinate porphyritic monzonite. The Late Devonian intrusions are characterized by SiO2 contents of 54.5-64.79 wt.%, Na2O contents of 3.82-8.24 wt.%, enrichment in Na, light rare-earth elements (LREEs), and large ion lithophile elements. They also display relative depletion in Y, Ba, P, Nb, Ta, and Ti, and weak negative Eu anomalies (δEu = 0.6-0.87). The early Carboniferous quartz porphyry is characterized by high SiO2 content (72.26-73.35 wt.%), enrichment in LREEs, K, and Sr, and relative depletion in Y (10.82-12.52 ppm) and Yb (1.06-1.15 ppm). The Late Devonian and early Carboniferous granitoids are characterized by positive ɛNd(t) values (5.2-10.1, one sample at - 1.9), positive ɛHf(t) values (7.46-18.45), low (87Sr/86Sr)i values (0.70363-0.70476), and young crustal residence ages. These data indicate that the sources of the granitoids were mainly mantle-derived juvenile rocks. Geochemical and Nd-Sr-Hf isotopic data demonstrate that the Late Devonian granitoids formed in an oceanic island arc, and they were formed from different sources, among which the mineralized diorite porphyry might have originated from a mixed slab-derived and mantle wedge melt source. The early Carboniferous quartz porphyry was likely emplaced in a mature island arc environment, and was probably derived from juvenile crust.

  15. Zircon U-Pb dating, geochemical and Sr-Nd-Hf isotopic characteristics of the Jintonghu monzonitic rocks in western Fujian Province, South China: Implication for Cretaceous crust-mantle interactions and lithospheric extension

    NASA Astrophysics Data System (ADS)

    Li, Bin; Jiang, Shao-Yong; Lu, An-Huai; Zhao, Hai-Xiang; Yang, Tang-Li; Hou, Ming-Lan

    2016-09-01

    Comprehensive petrological, in situ zircon U-Pb dating, Ti-in-zircon temperature and Hf isotopic compositions, whole rock geochemical and Sr-Nd isotopic data are reported for the Jintonghu monzonitic intrusions in the western Fujian Province (Interior Cathaysia Block), South China. The Jintonghu monzonitic intrusions were intruded at 95-96 Ma. Their Sr-Nd-Hf isotopic compositions are similar to the coeval and nearby enriched lithospheric mantle-derived mafic and syenitic rocks, indicating that the Jintonghu monzonitic rocks were likely derived from partial melting of the enriched mantle sources. Their high Nb/Ta ratios (average 21.6) suggest that the metasomatically enriched mantle components were involved, which was attributed to the modification of slab-derived fluid and melt by the subduction of the paleo-Pacific Plate. The presence of mafic xenoliths, together with geochemical and isotopic features indicates a mafic-felsic magma mixing. Furthermore, the Jintonghu intrusions may have experienced orthopyroxene-, biotite- and plagioclase-dominated crystallization. Crust-mantle interaction can be identified as two stages, including that the Early Cretaceous mantle metasomatism and lithospheric extension resulted from the paleo-Pacific slab subduction coupled with slab rollback, and the Late Cretaceous crustal activation and enhanced extension induced by dip-angle subduction and the underplating of mantle-derived mafic magma.

  16. Paleoproterozoic crustal evolution in the East Sarmatian Orogen: Petrology, geochemistry, Sr-Nd isotopes and zircon U-Pb geochronology of andesites from the Voronezh massif, Western Russia

    NASA Astrophysics Data System (ADS)

    Terentiev, R. A.; Savko, K. A.; Santosh, M.

    2016-03-01

    Andesites and related plutonic rocks are major contributors to continental growth and provide insights into the interaction between the mantle and crust. Paleoproterozoic volcanic rocks are important components of the East Sarmatian Orogen (ESO) belonging to the East European Craton, although their petrogenesis and tectonic setting remain controversial. Here we present petrology, mineral chemistry, bulk chemistry, Sr-Nd isotopes, and zircon U-Pb geochronological data from andesites and related rocks in the Losevo and Vorontsovka blocks of the ESO. Clinopyroxene phenocrysts in the andesites are depleted in LREE, and enriched in HFSE (Th, Nb, Zr, Hf, Ti) and LILE (Ba, Sr). Based on the chemistry of pyroxenes and whole rocks, as well as Fe-Ti oxides, we estimate a temperature range of 1179 to 1262 °C, pressures of 11.3 to 13.0 kbar, H2O content of 1-5 wt.%, and oxygen fu gacity close to the MH buffer for the melts of the Kalach graben (KG) and the Baygora area (BA) andesites. Our zircon U-Pb geochronological data indicate new zircon growth during the middle Paleoproterozoic as displayed by weighted mean 207Pb/206Pb ages of 2047 ± 17 Ma and 2040 ± 16 Ma for andesite and dacite-porphyry of the BA, and 2050 ± 16 Ma from high-Mg basaltic andesite of the KG. The andesites and related rocks of the KG and BA are characterized by high magnesium contents (Mg # up to 0.68). All these volcanic rocks are depleted in LREE and HFSE, and display negative Nb and Ti anomalies relative to primitive mantle. The high-Mg bulk composition, and the presence of clinopyroxene phenocrysts suggests that the parent melts of the KG and BA suite were in equilibrium with the mantle rocks. The rocks show positive εNd(T) values and low initial 87Sr/86Sr, suggesting that the magmas were mostly derived from metasomatized mantle source. The geochemical differences between the two andesite types are attributed to: the predominance of fractional crystallization, and minor role of contamination in the

  17. Eocene Granitoids of the Okhotsk Complex in Sakhalin Island, Russian Far East: Petrogenesis and tectonic implications from zircon U-Pb ages, geochemical and Sr-Nd isotopic characteristics

    NASA Astrophysics Data System (ADS)

    Liao, Jia Ping; Alexandrov, Igor; Jahn, Bor-ming

    2016-04-01

    Sakhalin Island represents an important part of the Western Pacific Orogenic Belt (or "Nipponides"). The island comprises several accreted terrains that have recorded strike-slip displacements and block rotations from Cretaceous to Tertiary. These terrains include fore-arc basins, accretionary complexes and island arc assemblages. The stratigraphic features of most terrains can be correlated to those of Hokkaido Island of Japan. However, little research has been undertaken on the magmatic activities on Sakhalin, so a direct comparison of crustal development and tectonic activities with Hokkaido has not been fulfilled. We intend to study the petrogenesis of granitic complexes of Sakhalin to resolve this problem. In this work, we present new results of age determination and geochemical analyses of the Okhotsk Complex and discuss the tectonic implications. The Okhotsk complex is one of the three main granitoid complexes in Sakhalin Island. It intruded into the Ozersk accretionary terrain that is composed of island arc assemblages and marine sediments and has traveled northward and accreted to Sakhalin Island in Eocene. Eleven samples from the Okhotsk Complex, including 7 granitoids, 1 enclave, 2 rhyolites, and 1 dacite, were subject to zircon U-Pb dating, whole-rock geochemical and Sr-Nd isotopic analyses. The results show that the entire complex was emplaced within 42 to 44 Ma. The 7 granitoids are slightly peraluminous, ferroan, and alkali-calcic. The REE abundances of granitoids show consistent patterns with weak LREE enrichment and negative Eu anomaly. The spidergrams show negative Ta-Nb-Ti anomaly as expected in most granitoids. They possess transitional characteristics between I- and A-type granites. For isotopic signatures, the granitoids have ɛNd(t) values of +2.8 to +3.7, initial 87Sr/86Sr ratios of 0.7047 to 0.7050, and Sm-Nd model ages (TDM-1) of 700-1100 Ma. The middle Eocene magmatic episode (42-44 Ma) of the Okhotsk Complex can find its counterpart in

  18. Overlapping Sr-Nd-Hf-O isotopic compositions in Permian mafic enclaves and host granitoids in Alxa Block, NW China: Evidence for crust-mantle interaction and implications for the generation of silicic igneous provinces

    NASA Astrophysics Data System (ADS)

    Dan, Wei; Wang, Qiang; Wang, Xuan-Ce; Liu, Yu; Wyman, Derek A.; Liu, Yong-Sheng

    2015-08-01

    In general, the mantle provides heat and/or material for the generation of the silicic igneous provinces (SIPs). The rarity of mafic microgranular enclaves (MMEs), however, hampers understanding of the mantle's role in generating SIPs and the process of crust-mantle interaction. The widespread distributed MMEs in the newly reported Alxa SIP provide an opportunity to study these processes. This study integrates in situ zircon U-Pb age and Hf-O isotope analyses, whole-rock geochemistry and Sr-Nd isotope results for the MMEs and host granitoids in the Alxa Block. SIMS zircon U-Pb dating reveals that there are two generations of MMEs and host granitoids. The MMEs in the Bayannuoergong batholith were formed at ca. 278 Ma, similar to the age (280 Ma) of host granitoids, and the MMEs and host granitoids in the Yamaitu pluton were formed at ca. 272-270 Ma. All MMEs have relatively low SiO2 (50.7-61.4 wt.%) and Th (0.8-2.8 ppm), but relatively high MgO (2.6-4.9 wt.%), Cr (23-146 ppm) and Ni (6-38 ppm) contents compared to the host granitoids, with SiO2 (63.6-77.5 wt.%), Th (5.2-41 ppm), MgO (0.23-2.1 wt.%), Cr (10-38 ppm) and Ni (5-14 ppm). All MMEs have whole rock Sr-Nd and zircon Hf-O isotope compositions similar to their corresponding host granitoids. The 280 Ma MMEs have lower whole rock εNd(t) (- 13.5) and higher initial 87Sr/86Sr values (0.7095) and zircon δ18O values (6.3‰) compared to the εNd(t) (- 11.5), initial 87Sr/86Sr values (0.7070) and zircon δ18O values (5.6‰) of the 270 Ma MMEs. The occurrences of quartz xenocrysts, K-feldspar megacrysts, corroded feldspars and acicular apatites indicate that the MMEs are the products of the mixing between mantle- and crust-derived magmas. The striking similarities in the zircon Hf-O isotopic compositions in both MME-host granitoid pairs indicate that the granitoids and MMEs have similar sources. The granitoids are proposed to be mainly sourced from magmas generated by remelting of newly formed mafic rocks, which

  19. The role of recycled oceanic crust in magmatism and metallogeny: Os-Sr-Nd isotopes, U-Pb geochronology and geochemistry of picritic dykes in the Panzhihua giant Fe-Ti oxide deposit, central Emeishan large igneous province, SW China

    NASA Astrophysics Data System (ADS)

    Hou, Tong; Zhang, Zhaochong; Encarnacion, John; Santosh, M.; Sun, Yali

    2013-04-01

    The picritic dykes occurring within fine-grained gabbro in the marginal zone and in the surrounding Proterozoic wall-rock marbles of the Panzhihua Fe-Ti oxide deposit closely correspond in bulk composition with the nearby Panzhihua intrusion. These dykes offer important constraints on the nature of the mantle source of the Panzhihua ore-bearing intrusion and its possible link to the Emeishan plume. U-Pb zircon dating of the picritic dyke yields a crystallization age of 261.4 ± 4.6 Ma, coeval with the timing of the main Panzhihua gabbroic intrusion and Late Permian Emeishan flood basalts. The Panzhihua picritic dykes contain 37.63-43.41 wt% SiO2, 1.15-1.56 wt% TiO2, 11.43-13.25 wt% TFe2O3, and 20.96-28.87 wt% MgO. Primitive-mantle-normalized patterns of the rocks are comparable to those of ocean island basalt. The rocks define a relatively small range of Os isotopic compositions and a low Os signature of -0.13 to +2.76 for γOs (261 Ma). In combination with their Sr-Nd-Os isotopic compositions, we interpret that these rocks were derived from the Emeishan plume sources as well as the interactions of plume melts with the overlying lithosphere which had been extensively affected by eclogite-derived melts from the deep-subducted oceanic slab. Partial melting induced by an upwelling mantle plume that involved an eclogite or pyroxenite component in the lithospheric mantle could have produced the parental Fe-rich magma. Our study suggests that plume-lithosphere interaction might have played a key role in generating many world-class Fe-Ti oxide deposits clustered in the Panxi area.

  20. Geochemical and Sr-Nd isotope variations within Cretaceous continental flood-basalt suites of the Canadian High Arctic, with a focus on the Hassel Formation basalts of northeast Ellesmere Island

    NASA Astrophysics Data System (ADS)

    Estrada, Solveig

    2015-11-01

    Early- to mid-Cretaceous flood-basalt suites of the northeast Canadian High Arctic assigned to a High Arctic Large Igneous Province (HALIP) were studied for their whole-rock geochemistry and Sr-Nd isotopes. Data from basalt flows within the upper Albian to lower Cenomanian Hassel Formation of northeast Ellesmere Island are compared with former published data and new inductively coupled plasma mass spectrometry data of the stratigraphic equivalent Strand Fiord basalts and the older, late Hauterivian to Aptian Isachsen basalts from Axel Heiberg Island. The transitional to mildly alkaline aphyric Hassel basalts, with ocean island basalt (OIB)-like geochemical signatures in parts, have an Ar-Ar whole-rock age of on average 96.4 ± 1.6 Ma. They represent two geochemically different flow units without a fractional crystallization relationship: the high-phosphorous (HP) and low-phosphorous (LP) basalts. The Hassel HP basalts differ from the LP basalts by additionally higher Ba, K, Rb, Th and LREE contents, a pronounced positive Eu anomaly (Eu/Eu* = 1.74-1.76), as well as lower Ta, Nb, Zr and Hf concentrations. The Nd and Sr isotope ratios of the Hassel HP basalts [ ɛ Nd( t) of -1.3 to -1.4, 87Sr/86Sr( t) of 0.70706-0.70707] and the LP basalts [ ɛ Nd( t) of 4.5-4.9, 87Sr/86Sr( t) of 0.7038-0.7040] indicate an origin from different mantle sources. The geochemically similar tholeiitic Isachsen (ca. 130-113 Ma) and Strand Fiord basalts (ca. 105-95 Ma) are also incompatible element enriched relative to the primitive mantle, however, with negative Sr-P anomalies as well as partially negative K, Ta and Nb anomalies. In terms of incompatible element ratios (Zr/Nb, Nb/Th), several mantle components are involved in the formation of the flood-basalt suites: a component with primitive mantle composition, an OIB-like component (probably subducted and recycled oceanic crust) and an enriched lithospheric component. The latter component, probably metasomatized subcontinental

  1. Dating the Indo-Asia collision in NW Himalaya: constraints from Sr-Nd isotopes and detrital zircon (U-Pb) and Hf isotopes of Paleogene-Neogene rocks in the Katawaz basin, NW Pakistan

    NASA Astrophysics Data System (ADS)

    Zhuang, Guangsheng; Najman, Yani; Millar, Ian; Chauvel, Catherine; Guillot, Stephane; Carter, Andrew

    2015-04-01

    The time of collision between the Indian and Asian plates is key for understanding the convergence history and the impact on climatic systems and marine geochemistry. Despite much active research, the fundamental questions still remain elusive regarding when and where the Indian plate collided with the Asian plate. Especially in the west Himalaya, the questions become more complex due to disputes on the amalgamation history of interoceanic Kohistan-Ladakh arcs (KLA) with Karakoram of the Asian plate and the Indian plate. Here, we present a result of multiple-isotopic geochemistry and geochronology study in the Katawaz Basin in NW Pakistan, a remnant oceanic basin on the western Indian plate which was the repository for the sediments eroded from the west Himalaya ( Qayyum et al., 1996, 1997a, 1997b, 2001; Carter et al., 2010), to evaluate the time and character of collision in this region. In this study, we analyzed 22 bulk mudstone samples for Sr-Nd isotopes and 11 medium-grained sandstones for detrital zircon (U-Pb) geochronology and Hf isotopes. We constructed the Cenozoic chronology in the Katawaz Basin based on our newly collected detrital zircon U-Pb ages and fission track ages. We present the first record of Katawaz chronology that constrained the Khojak Formation to be < 40 Ma to < 22 Ma. The result is consistent with the previous nanofossil study that constrained the upper part of underlying Nisai Formation to be the Middle to Late Eocene. Our current study revealed that the Katawaz sedimentary sequence ranges in age from Eocene to the earliest Miocene. The samples from the Nisai Formation show the 87Sr/86Sr - ɛNd values overlapping those of the end member of the Karakoram of Asian origin, revealing the arrival of Asian detritus on the Indian plate prior to 50 Ma. There are two parallel lines of evidence supporting this conclusion: (1) young zircon grains (< 120 Ma), characterizing the KLA and Karakoram, persistently exist throughout the whole sedimentary

  2. Zircon U-Pb dating, geochemistry and Sr-Nd-Pb-Hf isotopes of the Wajilitag alkali mafic dikes, and associated diorite and syenitic rocks: Implications for magmatic evolution of the Tarim large igneous province

    NASA Astrophysics Data System (ADS)

    Zou, Si-Yuan; Li, Zi-Long; Song, Biao; Ernst, Richard E.; Li, Yin-Qi; Ren, Zhong-Yuan; Yang, Shu-Feng; Chen, Han-Lin; Xu, Yi-Gang; Song, Xie-Yan

    2015-01-01

    The Early Permian Tarim large igneous province (Tarim LIP) consists mainly of basaltic lavas, mafic-ultramafic intrusions including dikes and, syenite bodies in the Tarim Basin, NW China. A major unit of the Tarim LIP, the Wajilitag intrusive complex, consists of olivine pyroxenite, clinopyroxenite and gabbro units (from bottom to top), diorite and syenite rocks occurred in the upper part of the complex and alkali mafic dikes intrude the clinopyroxenite phase. Here we report the zircon U-Pb age and Hf isotopes, geochemical characteristics and Sr-Nd-Pb isotopic data of the alkali mafic dikes, and diorite, aegirine-nepheline syenite and syenite porphyry units in the Wajilitag intrusive complex. Zircons from the diorite and alkali mafic rocks yield concordant crystallization ages of 275.2 ± 1.2 Ma and 281.4 ± 1.7 Ma, respectively. The diorite and syenitic rocks in Wajilitag area have a narrow range of SiO2 contents (51.9-57.3 wt.%), and are enriched in total alkalis (Na2O + K2O = 8.3-14.3 wt.%), among which the aegirine-nepheline syenite and syenite porphyry have the geochemical affinity of A-type granites. The alkali mafic rocks and syenitic rocks have high Al2O3 (19.4-21.1 wt.%), Zr, Hf, Ba contents, total rare earth element abundances and LREE/HREE ratios and low Mg# value, K, P and Ti contents. Diorites have lower Al2O3 contents, total REE abundances and LREE/HREE ratios and higher Mg# values than the alkali mafic rocks and syenitic rocks. The diorites and syenitic rocks have low initial 87Sr/86Sr ratios (0.7034-0.7046), and high εNd(t) values (0.1-4.1) and zircon εHf(t) values (- 0.9-4.4). All the diorites and syenitic rocks show the 206Pb/204Pb ratios ranging of 18.0-19.5, 207Pb/204Pb of 15.4-15.6 and 208Pb/204Pb of 38.0-39.9. Sr-Nd isotopic ratios indicate a FOZO-like mantle source for the diorite and syenitic rocks, similar to that of the mafic-ultramafic rocks in the Wajilitag complex. In contrast, zircon Hf isotopes of basalt and syenite elsewhere in the

  3. Zircon U-Pb geochronology, geochemical and Sr-Nd-Hf isotopic compositions of the Triassic granite and diorite dikes from the Wulonggou mining area in the Eastern Kunlun Orogen, NW China: Petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Ding, Qing-Feng; Jiang, Shao-Yong; Sun, Feng-Yue

    2014-09-01

    The Wulonggou mining area in the Eastern Kunlun Orogen of NW China is characterized by extensive granitoid magmatism, ductile faulting, and skarn-type Cu-Pb-Zn and orogenic gold mineralizations. The Balugou granite dike, which hosts skarn-type Cu-Pb-Zn mineralizations, is located in northeast Wulonggou, whereas the Huanglonggou diorite dike, which is cut by the Huanglonggou gold veins, is located in the central part of the area. This study investigated the major and trace-element compositions, zircon U-Pb dates, and Sr-Nd-Hf isotopic compositions of these rocks. Three Balugou granite dike samples yielded an average zircon U-Pb age of ~ 244 Ma (Anisian), and two Huanglonggou diorite dike samples yielded an average zircon U-Pb age of ~ 215 Ma (Norian). Therefore, the skarn-type mineralizations in the Wulonggou area formed during the early Anisian (~ 244 Ma), and the orogenic gold mineralizations formed after 215 Ma. The Anisian Balugou granite dike is metaluminous to slightly peraluminous and has high alkali contents of 7.19-9.57 wt.%, high Zr + Nb + Ce + Y contents, high Fe2O3T/MgO ratios, and high Rb/Nb and Y/Nb ratios, which suggest an A-type affinity. The Norian Huanglonggou diorite dike is metaluminous and has high Al2O3 contents (15.61-16.40 wt.%), high Mg# values (0.49-0.54), relatively high Sr contents (370-507 ppm), high Sr/Y ratios, high (La/Yb)N ratios, and low HREE and Y contents, which suggest an adakite-like high-Mg diorite. The Anisian granite dike has initial 87Sr/86Sr (ISr) ratios of 0.707289 to 0.708981, εNd(t) values of - 3.6 to - 3.1, and zircon εHf(t) values of - 3.9 to + 1.3. The Norian diorite dike has initial 87Sr/86Sr (ISr) ratios of 0.709166 to 0.709529, εNd(t) values of - 5.7 to - 5.1, and zircon εHf(t) values of - 4.9 to - 1.0. The Sr-Nd-Hf isotopic data suggest that the Anisian granite dike was likely derived from partial melting of dominantly Mesoproterozoic mafic lower crust, whereas the Norian diorite dike was likely derived from

  4. Petrogenesis and tectonic settings of volcanic rocks of the Ashele Cu-Zn deposit in southern Altay, Xinjiang, Northwest China: Insights from zircon U-Pb geochronology, geochemistry and Sr-Nd isotopes

    NASA Astrophysics Data System (ADS)

    Wu, Yufeng; Yang, Fuquan; Liu, Feng; Geng, Xinxia; Li, Qiang; Zheng, Jiahao

    2015-11-01

    The Early-Mid-Devonian Ashele Formation of the southern margin of the Chinese Altay hosts the Ashele Cu-Zn volcanogenic massive sulfide (VMS) deposit and consists of intercalated volcanic and sedimentary rocks that have experienced regional greenschist-facies metamorphism. We studied the petrography, zircon U-Pb geochronology, geochemistry, and Sr-Nd isotopes of dacites and basalts in order to understand the petrogenesis of these rocks and the regional tectonic evolution. Two dacites yielded LA-MC-ICP-MS zircon U-Pb ages of 402 ± 6 Ma and 403 ± 2 Ma. The dacites are calc-alkaline, and characterized by high Na2O/K2O ratios (3.6-9.3), and high Mg# values (47-63), enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), depletion in Nb, Ta, Ti, and P, and relatively positive εNd(t) values (+3.6 to +7.5), collectively suggesting a sanukitic magma affinity. The variations in the major and trace elements of the dacites indicate that Fe-Ti oxide, plagioclase, and apatite were fractionated during their petrogenesis. The basalts are tholeiitic, and are characterized by high Mg# values (66-73), and negative Nb and Ta anomalies. The geochemical characteristics of the basalts are similar to those of N-MORB. Those characteristics together with the positive εNd(t) values (+6.8 to +9.2) of the basalts, indicate that the precursor magma was derived mainly from an N-MORB-type depleted asthenospheric mantle in an island arc setting. The geochemical similarities between the basalts and dacites indicate that they both originated from a similar depleted mantle source via partial melting under different magmatic conditions in each case, possibly related to ridge subduction.

  5. Origin of the granites and related Sn and Pb-Zn polymetallic ore deposits in the Pengshan district, Jiangxi Province, South China: constraints from geochronology, geochemistry, mineral chemistry, and Sr-Nd-Hf-Pb-S isotopes

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Jiang, Shao-Yong; Luo, Lan; Zhao, Kui-Dong; Ma, Liang

    2016-05-01

    The Pengshan Sn and Pb-Zn polymetallic deposits are located in the south margin of the Jiujiang-Ruichang (Jiurui) district of the Middle-Lower Yangtze River Metallogenic Belt in South China. Four large deposits include Huangjinwa, Zengjialong, Jianfengpo, and Zhangshiba, the former three are Sn-dominant deposits which occur as stratiform orebodies in the contact zones of the Pengshan granites and within the country rock strata, whereas Zhangshiba consists of stratiform Pb-Zn orebodies within the Precambrian metasedimentary strata. In this study, we present results on zircon U-Pb ages, major and trace elements, and mineral chemistry as well as Sr-Nd-Hf isotope data of the granites, Pb and S isotopes of both the Sn-dominant and Pb-Zn dominant deposits, and U-Pb dating of cassiterite from the Pengshan district. SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the Pengshan granites were emplaced in the Early Cretaceous (129-128 Ma), which is in good agreement with the U-Pb dating (130-128 Ma) of cassiterite from the Jianfengpo Sn deposit. The Pengshan granites consist mainly of weakly peraluminous highly fractionated I-type affinity granitic rocks. Detailed elemental and isotopic data suggest that the granites formed by partial melting of Mesoproterozoic metamorphic basement materials with minor input of mantle-derived melts. The mineral chemistry of biotite demonstrates that the Pengshan granitic magma had a low oxygen fugacity, thereby precluding the tin dominantly partitioning into the rock-forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages. Sulfur isotopes show a relatively heavy sulfur isotopic composition from 5.8 to 17.6 ‰, and no difference for sulfur isotopes between the Sn deposits (5.8-13.4 ‰, Huangjinwa, Zengjialong, Jianfengpo) and the Pb-Zn deposit (mostly 7.1-13.0 ‰, except for one 17.6 ‰, Zhangshiba). The sulfur isotope data of pyrite from the host sedimentary rocks show

  6. Geochemical and Sr-Nd-Pb Isotopic Insights of the Low-Ti basalts from Paraná-Etendeka Igneous Province, Southern Brazil: Constraints on Petrogenesis and the Role of Crustal Contamination

    NASA Astrophysics Data System (ADS)

    Raposo, I.; Barreto, C. J.; Lima, E. F. D.; Lafon, J. M.; Sommer, C. A.; Waichel, B. L.

    2015-12-01

    The south hinge of the Torres Syncline in southernmost Brazil hosts a volcanic succession of pahoehoe and rubbly Gramado-type lavas belonging to the ~132 Ma Paraná-Etendeka Igneous Province. We employ local-scale stratigraphy in three distinct profiles (Santa Cruz do Sul-Herveiras, Morro da Cruz and Lajeado geologic sections) as guidelines for geochemical and Sr-Nd-Pb isotope studies in order to discuss the petrogenesis of lava flows in a single magma type and to quantitatively evaluate the role of crustal contamination and the potential contaminants involved. In all profiles, the lava flows exhibit compositions ranging from basalt to andesite with tholeiitic affinity. The compositional and isotopic variations are not systematic according to stratigraphy, implying that the magma chamber could have undergone periodic replenishments or distinct magma pulses through time or multiple plumbling systems may have existed. The andesites (SiO2 55-58 wt.%) with ponded pahoehoe morphology represent evolved melts at early stages of volcanism with strong susceptibility to crustal contamination as they established pathways to the surface. The olivine basalts (SiO2 47-50 wt.%) and basaltic andesites (SiO2 51-56 wt.%) showing compound morphology and simple pahoehoe morphology, respectively, could be explained by longer time residence of liquids in the crust with higher degrees of crustal assimilation than the ponded pahoehoe lavas. The basaltic andesites (SiO2 52-56 wt. %) with rubbly morphology are related to late differentiation process in shallow magma chambers. Crustal assimilation process accounts for the high initial 87Sr/86Sr ratios at 0.707798-0.715751, very low ɛNd between -8.36 and -5.41, high 206Pb/204Pb ratios at 18.424-18.865, with intermediate 207Pb/204Pb and 208Pb/204Pb ratios at 15.649-15.710 and 38.618-39.369, respectively. The isotopic variations require assimilation of both Paleoproterozoic and Neoproterozoic contaminants at variable degrees.

  7. Sr-Nd isotopes and mineralogy as tracers of continental erosion and sediment transport to the Red Sea and the Gulf of Aden during the last 20,000 years

    NASA Astrophysics Data System (ADS)

    Rojas, V. P.; Meynadier, L.; Bassinot, F. C.; Christophe, C.; Valet, J. P.

    2014-12-01

    During the transition from the last glacial maximum to the Holocene, production and transport of matter into the southern part of Red Sea and Gulf of Aden were sensitive to changes in monsoon winds, rain intensity and ITCZ position. We studied two marine cores on each side of the Bab-el-Mandeb strait in order to compare the open ocean and a more isolated basin at the Eastern limit of the Arabic peninsula. Erosion and matter transfer from the continent have been documented by different approaches, which include radiogenic isotopes and mineralogy of bulk samples and clay fraction. The Sr-Nd fingerprint of detrital sediments is an effective tool for discriminating between sediment sources. Mineralogical composition also depends on lithology of the source area and can provide insight on the environmental conditions at the time of deposition. ɛNd and 87Sr/86Sr from the detrital fraction in both cores show large changes linked to the Glacial-Interglacial transition, following the foraminifera δ18O data. The isotopic values evolved towards a lower volcanic contribution from the last glaciation to the Holocene with a more pronounced change in the Gulf of Aden and more volcanic values for the Red Sea. The sediment mineralogy includes quartz, feldspar, muscovite, biotite, amphibole and pyroxene. Clay mineralogy is dominated by smectite and lesser amounts of illite and palygorskite. Correlation of percentage of smectite and Nd-Sr isotope composition agrees with a volcanic origin of smectite and shows a 2-pole mixture of sediment sources. The first end member is characterized by a large amount of smectite, positive values of ɛNd and a low 87Sr/86Sr ratio and was identified as Afar volcanic rocks. The second one with more negative values of ɛNd and a higher 87Sr/86Sr ratio is enriched in illite and palygorskite and was defined as originating from the Central Arabian region. Changes in sediment composition during the Glacial-Interglacial transition denote a variation in the

  8. Major and trace element and Sr-Nd isotope signatures of lavas from the Central Lau Basin: Implications for the nature and influence of subduction components in the back-arc mantle

    NASA Astrophysics Data System (ADS)

    Tian, Liyan; Castillo, Paterno R.; Hawkins, James W.; Hilton, David R.; Hanan, Barry B.; Pietruszka, Aaron J.

    2008-12-01

    New major and trace element and Sr-Nd isotope data are presented for basaltic glasses from active spreading centers (Central Lau Spreading Center (CLSC), Relay Zone (RZ) and Eastern Lau Spreading Center (ELSC)) in the Central Lau Basin, SW Pacific. Basaltic lavas from the Central Lau Basin are mainly tholeiitic and are broadly similar in composition to mid-ocean ridge basalts (MORB). Their generally high 87Sr/ 86Sr ratios, combined with relatively low 143Nd/ 144Nd ratios are more akin to MORB from the Indian rather than Pacific Ocean. In detail, the CLSC, RZ and ELSC lavas are generally more enriched in large ion lithophile elements (Rb, Ba, Sr, and K) than average normal-MORB, which suggests that the mantle beneath the Central Lau Basin was modified by subducted slab-derived components. Fluid mobile/immobile trace element and Sr - Nd isotope ratios suggest that the subduction components were essentially transferred into the mantle via hydrous fluids derived from the subducted oceanic crust; contributions coming from the subducted sediments are minor. Compared to CLSC lavas, ELSC and RZ lavas show greater enrichment in fluid mobile elements and depletion in high field strength elements, especially Nb. Thus, with increasing distance away from the arc, the influence of subduction components in the mantle source of Lau Basin lavas diminishes. The amount of hydrous fluids also influences the degree of partial melting of the mantle beneath the Central Lau Basin, and hence the degree of melting also decreases with increasing distance from the arc.

  9. U Pb zircon age, geochemical and Sr Nd Pb Hf isotopic constraints on age and origin of alkaline intrusions and associated mafic dikes from Sulu orogenic belt, Eastern China

    NASA Astrophysics Data System (ADS)

    Liu, Shen; Hu, Ruizhong; Gao, Shan; Feng, Caixia; Qi, Youqiang; Wang, Tao; Feng, Guangying; Coulson, Ian M.

    2008-12-01

    Post-orogenic alkaline intrusions and associated mafic dikes from the Sulu orogenic belt of eastern China consist of quartz monzonites, A-type granites and associated mafic dikes. We report here U-Pb zircon ages, geochemical data and Sr-Nd-Pb-Hf isotopic data for these rocks. The SHRIMP U-Pb zircon analyses yield consistent ages ranging from 120.3 ± 2.1 Ma to 126.9 ± 1.9 Ma for five samples from the felsic rocks, and two crystallization ages of 119.0 ± 1.7 Ma and 120.2 ± 1.9 Ma for the mafic dikes. The felsic rocks and mafic dikes are characterized by high ( 87Sr/ 86Sr) i ranging from 0.7079 to 0.7089, low ɛNd( t) values from - 15.3 to - 19.2, 206Pb/ 204Pb = 16.54-17.25, 207Pb/ 204Pb = 15.38-15.63, 208Pb/ 204Pb = 37.15-38.45, and relatively uniform ɛHf( t) values of between - 21.6 ± 0.6 and - 23.7 ± 1.0, for the magmatic zircons. The results suggest that they were derived from a common enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials before magma generation. Geochemical and isotopic characteristics imply that the primary magma to these rocks originated through partial melting of ancient lithospheric mantle that was variably hybridized by melts derived from foundered lower crustal eclogite. The mafic dikes may have been generated by subsequent fractionation of clinopyroxene, whereas the felsic rocks resulted from fractionation of potassium feldspar, plagioclase and ilmenite or rutile. Both were not affected by crustal contamination. Combined with previous studies, these findings provide new evidence that the intense lithospheric thinning beneath the Sulu belt of eastern China occurred between 119 and 127 Ma, and that this was caused by the removal of the lower lithosphere (mantle and lower crust).

  10. Zircon U-Pb ages and Sr-Nd-Hf isotopes of the highly fractionated granite with tetrad REE patterns in the Shamai tungsten deposit in eastern Inner Mongolia, China: Implications for the timing of mineralization and ore genesis

    NASA Astrophysics Data System (ADS)

    Jiang, Si-Hong; Bagas, Leon; Hu, Peng; Han, Ning; Chen, Chun-Liang; Liu, Yuan; Kang, Huan

    2016-09-01

    The Shamai tungsten deposit is located in the eastern part of the Central Asian Orogenic Belt (CAOB). Tungsten mineralization is closely related to the emplacement of fine- to medium-grained biotite monzogranite (G1) and porphyritic biotite monzogranite (G2) in the Shamai Granite. NW-trending joints and faults host orebodies in the Shamai Granite and Devonian hornfels. The mineralization is characterized by a basal veinlet zone progressing upwards to a thick vein zone followed by a mixed zone, a veinlet zone, and a thread vein zone at the top. The ore-related alteration typically consists of muscovite, greisen, and hornfels. In order to constrain the timing of the Shamai mineralization and discuss the ore genesis, muscovite Ar-Ar, molybdenite Re-Os, and zircon U-Pb geochronological, geochemical, and Sr-Nd-Hf isotopic studies were completed on the deposit. The U-Pb zircon dating yielded weighted mean ages of 153 ± 1 Ma for G1 and 146 ± 1 Ma for G2. Muscovite from a wolframite-bearing quartz vein yielded an Ar-Ar plateau age of 140 ± 1 Ma, whereas two molybdenite samples yielded identical Re-Os model ages of 137 ± 2 Ma. These two ages are younger than the two monzogranites, suggesting a prolonged magmatic-hydrothermal interaction during tungsten mineralization. Major and trace element geochemistry shows that both G1 and G2 are characterized by high SiO2 and K2O contents, high A/CNK values (1.08-1.40), a spectacular tetrad effect in their REE distribution patterns, and non-CHARAC (charge-and-radius-controlled) trace element behavior. This suggests that both G1 and G2 are highly differentiated peraluminous rocks with strong hydrothermal interaction. The Nd-Hf isotope data for the Shamai Granite (εNd(t) between - 1.9 and + 7.4, ɛHf(t) from 5.2 to 12.8) are largely compatible with the general scenario for much of the Phanerozoic granite emplaced in the CAOB. It is here suggested that the Shamai Granite originated from partial melting of a juvenile lower crust with

  11. Unraveling protolith ages of meta-gabbros from Samos and the Attic-Cycladic Crystalline Belt, Greece: Results of a U-Pb zircon and Sr-Nd whole rock study

    NASA Astrophysics Data System (ADS)

    Bröcker, Michael; Löwen, Kersten; Rodionov, Nikolay

    2014-06-01

    The focus of this study is on meta-ophiolitic rocks from Samos and the Attic-Cycladic Crystalline Belt, Greece. SHRIMP U-Pb zircon geochronology, Sr-Nd isotope and bulk-rock geochemistry have been applied to meta-gabbros that occur as blocks and lenses in blueschist-facies mélanges on Samos and Evia, and in the greenschist-facies Upper Unit on Tinos. The geodynamic significance of these meta-ophiolite fragments within the overall pattern of the Eastern Mediterranean region is unclear. Regional correlations within the Cyclades archipelago and with the Jurassic meta-ophiolites of the Balkan region or the Cretaceous occurrences in Turkey are uncertain. Although field, petrological and geochemical similarities among some mélange occurrences suggest a common genetic relationship, such interpretations remain speculative if not supported by robust geochronological data. SHRIMP U-Pb zircon dating of three meta-gabbro blocks from Samos yielded Cretaceous ages with weighted mean 206Pb/238U ages of 78.3 ± 1.3 Ma, 76.8 ± 1.4 Ma and 77.8 ± 1.4 Ma and almost identical intercept ages, interpreted to indicate the time of magmatic crystallization. These results further substantiate models suggesting a correlative relationship with mélanges on the islands of Syros and Tinos, central Aegean Sea, where similar rocks yielded almost identical U-Pb zircon ages. Published and new Sr-Nd isotope data of meta-gabbros from Andros, Samos, Tinos (Lower Unit) and from mainland Greece (Pindos, Othris) reveal distinctive differences among ion probe-dated samples with Jurassic and Cretaceous protolith ages. Three groups can clearly be distinguished in a 87Sr/86Sr vs. 143Nd/144Nd diagram. However, these geochemical parameters do not allow assigning tentative age estimates for yet undated meta-gabbros from southern Evia and the Upper Unit of Tinos. The situation is further complicated by the observation that the Jurassic and Cretaceous meta-gabbros do not show other discriminating geochemical

  12. Elemental dispersion and stable isotope fractionation during reactive fluid-flow and fluid immiscibility in the Bufa del Diente aureole, NE-Mexico: evidence from radiographies and Li, B, Sr, Nd, and Pb isotope systematics

    NASA Astrophysics Data System (ADS)

    Romer, Rolf L.; Heinrich, Wilhelm; Schröder-Smeibidl, Birgit; Meixner, Anette; Fischer, Carl-Otto; Schulz, Cathrin

    2005-06-01

    The 31.6±0.3 Ma old Bufa del Diente alkali-syenite (NE Mexico) intruded a sequence of Cretaceous limestones with intercalated sub-horizontal chert layers. The cherts acted as aquifers that facilitated transport of brines and pegmatitic melts within the shallow-level (<1 kbar) contact-metamorphic aureole. Fluid-driven reactions between chert and marble wallrock, and the influx of late melts and various fluids gave rise to distinct chemical and isotopic signatures within the aquifer and across the zones of infiltration and fluid-driven reaction. Aqueous brines of magmatic origin produced thick wollastonite mantles around the chert layers. Wollastonite formation occurred at the expense of limestone and chert and generated CO2. This CO2-induced fluid unmixing into an aqueous brine and a low-density CO2-rich fluid, which was lost to the overlying marble where it oxidized organic matter and caused δ13C and δ18O shifts in a zone some 5 10 cm wide. After wollastonite formation, the chert aquifers were locally intruded by pegmatite veins carrying alkali feldspar, quartz, aegirine-augite, eudialyte, zircon, and apatite. Aqueous fluids that exsolved during crystallization of the pegmatite veins escaped along late cross-fractures and migrated along the inner and outer borders of the wollastonite margins. Chemical dispersion patterns of U, Al, Na + K, P, S, Fe, and REE across the chert-to-marble boundary and its metasomatic rims are shown by autoradiography and neutron-induced radiography. Scavenging of cations at mineralogical contacts and cation transport into the marbles occurred only on the mm to cm scale. Isotopic data for Pb and Sr across a simple metachert-marble boundary and for Pb, Sr, Nd, B, and Li across a metachert-pegmatite-marble sequence demonstrate the following: (1) The Pb and Sr isotopic signature of early fluids was buffered by the carbonate wallrock. Only late fluids, shielded from wallrock interaction by a wollastonite mantle, variably preserved a memory

  13. Nd isotopic composition of Jurassic Tethys seawater and the genesis of Alpine Mn-deposits: Evidence from Sr-Nd isotope data

    SciTech Connect

    Stille, P.; Clauer, N. ); Abrecht, J. )

    1989-05-01

    Jurassic metabasalts, metasediments and Mn ores from the Pennine realm of the Alps were examined in order to establish the Nd isotopic composition of the Jurassic Tethys seawater and to elucidate the genesis of the Mn deposits. The highly positive initial {epsilon}{sub Nd} values (+7 to +9.8) of the metabasalts and their low {sup 87}Sr/{sup 86}Sr ratios (0.7028 to 0.7049) indicate that they originated from a depleted mantle. The initial {epsilon}{sub Nd} values of the cherts range between {minus}5 and {minus}9. The Sm-Nd isotope data indicate that they are primary mixtures of basalt and continental detritus. The smaller than 2 {mu}m fractions of the cherts and of a marble, which probably represent the formerly authigenic material, show initial {epsilon}{sub Nd} values ranging between {minus}5.9 and {minus}6.6. The average initial Sr isotopic composition of five Mn ores is 0.70730 {plus minus} 22, identical to that of contemporaneous Jurassic seawater. The initial Nd isotopic composition values of the Mn ores are very homogeneous. The average value of five ores, a leachate and residue of one of them, calculated for an age of 170 Ma, is 0.512082 {plus minus} 19. It is suggested that the ores, together with the smaller than 2 {mu}m fractions of the sediments, define the Jurassic Tethys seawater isotopic composition. The resulting average {sup 143}Nd/{sup 144}Nd initial value is 0.512089 {plus minus} 17 ({epsilon}{sub Nd} {minus}6.5 {plus minus} 0.6).

  14. Nd isotopic composition of Jurassic Tethys seawater and the genesis of Alpine Mn-deposits: Evidence from Sr-Nd isotope data

    NASA Astrophysics Data System (ADS)

    Stille, P.; Clauer, N.; Abrecht, J.

    1989-05-01

    Jurassic metabasalts, metasediments and Mn ores from the Pennine realm of the Alps were examined in order to establish the Nd isotopic composition of the Jurassic Tethys seawater and to elucidate the genesis of the Mn deposits. The highly positive initial ɛNd values (+7 to +9.8) of the metabasalts and their low 87Sr /86Sr ratios (0.7028 to 0.7049) indicate that they originated from a depleted mantle. The initial ɛNd values of the cherts range between -5 and -9. The Sm-Nd isotope data indicate that they are primary mixtures of basalt and continental detritus. The smaller than 2 μm fractions of the cherts and of a marble, which probably represent the formerly authigenic material, show initial ɛnd values ranging between -5.9 and -6.6. The average initial Sr isotopic composition of five Mn ores is 0.70730 ± 22, identical to that of contemporaneous Jurassic seawater. The initial Nd isotopic composition values of the Mn ores are very homogeneous. The average value of five ores, a leachate and residue of one of them, calculated for an age of 170 Ma, is 0.512082± 19. It is suggested that the ores, together with the smaller than 2μm fractions of the sediments, define the Jurassic Tethys seawater isotopic composition. The resulting average 143Nd /144Nd initial value is 0.512089 ± 17 ( ɛNd -6.5 ± 0.6).

  15. Sr, Nd, and Pb isotopes in Proterozoic intrusives astride the Grenville Front in Labrador - Implications for crustal contamination and basement mapping

    NASA Technical Reports Server (NTRS)

    Ashwal, L. D.; Wooden, J. L.; Emslie, R. F.

    1986-01-01

    Trace element and Pb, Sr, and Nd isotopic compositions of anorthosites and related rocks, and of younger mafic dikes from Harp Lake and Mealy Mountains in Labrador, Canada are estimated and compared. The effects of crustal component contaminants on the isotopic compositions of the dikes are investigated. The correlation between the isotopic data and the crustal contamination model is studied. It is observed that for Harp Lake the initial Sr ratios are higher and the Nd values are lower than Mealy samples, and the data do not correspond to the crustal contamination model; however, the Pb isotope data favor a crustal contamination model. It is noted that the Labrador segment of the Grenville Front appears to coincide with the southern margin of the Archean North Atlantic craton, and may represent a pre mid-Proterozoic suture.

  16. Crystal structures and high-temperature phase-transitions in SrNdMRuO{sub 6} (M=Zn,Co,Mg,Ni) new double perovskites studied by symmetry-mode analysis

    SciTech Connect

    Iturbe-Zabalo, E.; Larranaga, A.; Cuello, G.J.

    2013-02-15

    Crystal structures of SrNdZnRuO{sub 6}, SrNdCoRuO{sub 6}, SrNdMgRuO{sub 6} and SrNdNiRuO{sub 6} double perovskites have been studied by X-ray, synchrotron radiation and neutron powder diffraction method, at different temperatures, and using the symmetry-mode analysis. All compounds adopt the monoclinic space group P2{sub 1}/n at room-temperature, and contain a completely ordered array of the tilted MO{sub 6} and RuO{sub 6} octahedra, whereas Sr/Nd cations are completely disordered. The analysis of the structures in terms of symmetry-adapted modes of the parent phase allows the identification of the modes responsible for the phase-transition. The high-temperature study (300-1250 K) has shown that the compounds present a temperature induced structural phase-transition: P2{sub 1}/n{yields}P4{sub 2}/n{yields}Fm3{sup Macron }m. - Graphical abstract: Representation of the dominant distortion modes of the symmetry mode decomposition of the room-temperature (P2{sub 1}/n), intermediate (P4{sub 2}/n) and cubic (Fm-3m) phase SrNdMRuO{sub 6} (M=Zn,Co,Mg,Ni), with respect to the parent phase Fm-3m. The dominant distortion modes are: in the monoclinic phase-GM{sub 4}{sup +} (blue arrow), X{sub 3}{sup +} (green arrow) and X{sub 5}{sup +} acting on A-site cations (red arrow); in the tetragonal phase-GM{sub 4}{sup +} (pink arrow), X{sub 3}{sup +} (light blue arrow) and X{sub 5}{sup +} acting on A-site cations (brown arrow). Highlights: Black-Right-Pointing-Pointer Structural study of four ruthenate double perovskites. Black-Right-Pointing-Pointer Room-temperature structural determination using symmetry-mode procedure. Black-Right-Pointing-Pointer Determination of temperature induced structural phase-transitions. Black-Right-Pointing-Pointer Symmetry adapted-mode analysis.

  17. Late Eocene to present isotopic (Sr-Nd-Pb) and geochemical evolution of sediments from the Lomonosov Ridge, Arctic Ocean: Implications for continental sources and linkage with the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Stevenson, Ross; Poirier, André; Véron, Alain; Carignan, Jean; Hillaire-Marcel, Claude

    2015-09-01

    New geochemical and isotopic (Sr, Nd, Pb) data are presented for a composite sedimentary record encompassing the past 50 Ma of history of sedimentation on the Lomonosov Ridge in the Arctic Ocean. The sampled sediments encompass the transition of the Arctic basin from an enclosed anoxic basin to an open and ventilated oxidized ocean basin. The transition from anoxic basin to open ventilated ocean is accompanied by at least three geochemical and isotopic shifts and an increase in elements (e.g., K/Al) controlled by detrital minerals highlighting significant changes in sediment types and sources. The isotopic compositions of the sediments prior to ventilation are more variable but indicate a predominance of older crustal contributions consistent with sources from the Canadian Shield. Following ventilation, the isotopic compositions are more stable and indicate an increased contribution from younger material consistent with Eurasian and Pan-African crustal sources. The waxing and waning of these sources in conjunction with the passage of water through Fram Strait underlines the importance of the exchange of water mass between the Arctic and North Atlantic Oceans.

  18. Emplacement ages, geochemical and Sr-Nd-Hf isotopic characterization of Mesozoic to early Cenozoic granitoids of the Sikhote-Alin Orogenic Belt, Russian Far East: Crustal growth and regional tectonic evolution

    NASA Astrophysics Data System (ADS)

    Jahn, Bor-ming; Valui, Galina; Kruk, Nikolai; Gonevchuk, V.; Usuki, Masako; Wu, Jeremy T. J.

    2015-11-01

    The Sikhote-Alin Range of the Russian Far East is an important accretionary orogen of the Western Pacific Orogenic Belt. In order to study the formation and tectonic evolution of the orogen, we performed zircon U-Pb dating, as well as geochemical and Sr-Nd-Hf isotopic analyses on 24 granitoid samples from various massifs in the Primorye and Khabarovsk regions. The zircon dating revealed that the granitoids were emplaced from 131 to 56 Ma (Cretaceous to Paleogene). In the Primorye Region, granitoids in the coastal Sikhote-Alin intruded the Cretaceous Taukha Accretionary Terrane from ca. 90 to 56 Ma, whereas those along the Central Sikhote-Alin Fault zone intruded the Jurassic Samarka Accretionary Terrane during ca. 110-75 Ma. The "oldest" monzogranite (131 Ma) was emplaced in the Lermontovka area of the NW Primorye Region. Granitoid massifs along the Central Sikhote-Alin Fault zone in the Khabarovsk Region formed from 109 to 58 Ma. Thus, the most important tectonothermal events in the Sikhote-Alin orogen took place in the Cretaceous. Geochemical analysis indicates that most samples are I-type granitoids. They have initial 87Sr/86Sr ratios ranging from 0.7040 to 0.7083, and initial Nd isotopic ratios, expressed as εNd(t) values, from +3.0 to -5.0 (mostly 0 to -5). The data suggest that the granitoid magmas were generated by partial melting of sources with mixed lithologies, including the subducted accretionary complex ± hidden Paleozoic-Proterozoic basement rocks. Based on whole-rock Nd isotopic data, we estimated variable proportions (36-77%) of juvenile component (=mantle-derived basaltic rocks) in the generation of the granitic magmas. Furthermore, zircon Hf isotopic data (εHf(t) = 0 to +15) indicate that the zircon grains crystallized from melts of mixed sources and that crustal assimilation occurred during magmatic differentiation. The quasi-continuous magmatism in the Sikhote-Alin orogen suggests that the Paleo-Pacific plate subduction was very active in the

  19. U-Pb Dating, whole rock and Sr-Nd-Pb-O isotope geochemistry of collisional magmatism in the CACC: Çiçekdaǧ igneous complex (ÇIC)

    NASA Astrophysics Data System (ADS)

    Deniz, Kiymet; Kagan Kadioglu, Yusuf; Stuart, Finlay; Ellam, Rob; Boyce, Adrian; Condon, Daniel

    2015-04-01

    The closure of Neotethys induced from calcalkaline through alkaline magmatism within the Central Anatolia Crystalline Complex (CACC) during the late Cretaceous-early Paleogene. Timing of these magmatism is very important for understanding the magmato-tectonic evolution and the relation with the collision. Despite the genesis of felsic products are well understood, there is lack of petrogenetic explanation about especially alkaline mafic products. The relation between Neotethyan ophiolites and late alkaline dykes which haven't reported before is the most important undeclared gap. Çiçekdağ igneous complex (ÇIC) is one of the best area for explaining all of these problems within the CACC. In accordance with these purposes, we have carried out detailed petrographic, whole rock geochemical, Sr-Nd-Pb-O isotopic and geochronological (U/Pb and Ar/Ar) study of the rocks in the ÇIC in order to unravel the magmatic history of the CACC and thus constrain the tectonic history. The intrusive rocks of the ÇIC are differentiated into four main group as an ophiolites, calcalkaline series, alkaline series and late alkaline dykes. The felsic and mafic units intruded to the ophiolitic rocks. The calcalkaline series mostly composed of monzonites and monzodiorite porphyry whereas the alkaline series consist of syenites and feldspathoid-bearing gabbros. Variations in the major oxide compositions of both rock series can be attributed with fractionation of clinopyroxene, plagioclase, amphibole, apatite and iron titan oxide minerals. The high 87Sr/86Sr and low 143Nd/144Nd of both series are indicative of mantle sources with large continental crustal components. Feldspar and quartz oxygen isotope data from calcalkaline and alkaline series have a range of δ18O values 5.1-11.4o 8.3-9.2o and 7.7-14.1o 10.2-13.7o respectively and are compatible with the values for I-A-type granitoids. Both rock series represent the mixed (mantle-crustal) origin. The combination of all data suggest that

  20. A Sr-Nd-Hf isotope characterization of dust source areas in Victoria Land and the McMurdo Sound sector of Antarctica

    NASA Astrophysics Data System (ADS)

    Blakowski, Molly A.; Aciego, Sarah M.; Delmonte, Barbara; Baroni, Carlo; Salvatore, Maria Cristina; Sims, Kenneth W. W.

    2016-06-01

    Determining the geographical provenance of dust provides crucial insight into the global dust cycle. For the East Antarctic Ice Sheet (EAIS), the importance of Southern hemisphere potential dust sources has been thoroughly investigated using radiogenic isotopes, whereas proximal dust source areas located on the periphery of the ice sheet remain poorly documented from a geochemical standpoint. In this work, we expand the existing isotopic (Srsbnd Nd) catalogue of dust and sand-sized sediments from Victoria Land and the McMurdo Sound sector, and incorporate Hf isotopic data to place additional constraints on dust source identification. The isotopic field for materials considered in this study is characterized by 87Sr/86Sr ratios ranging from 0.703 to 0.783, εNd between -12.01 and 6.36, and εHf from -16.77 to 6.89. As reported in previous works, the data reveal close relationships between Antarctic sediments and distinct parent lithologies; in addition, our findings emphasize the background presence of very fine dusts originating from dominant global sources and regional volcanic activity as barriers to direct source-to-sink comparison of isotopic signatures. Thus, geochemical characterizations of dust sources to the Antarctic ice sheet involving multiple size fractions, including coarser-grained particles more susceptible to short-range transport, can help us to rule out global sources of dust when examining local sediment cores and ice cores.

  1. Zircon U-Pb age and Sr-Nd-Hf isotope geochemistry of the Ganluogou dioritic complex in the northern Triassic Yidun arc belt, Eastern Tibetan Plateau: Implications for the closure of the Garzê-Litang Ocean

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Xiao, Long; Wilde, Simon A.; Ma, Chang-Qian; Li, Zi-Long; Sun, Yi; Zhan, Qiong-Yao

    2016-04-01

    The Triassic Yidun arc belt (YAB) lies between the Jinshajiang suture zone to the west and the Garzê-Litang suture zone to the east, Eastern Tibetan Plateau. To study the YAB can not only help us to better understand the evolutionary history of the Garzê-Litang Ocean but can also provide some important information to constrain the evolution of the eastern Paleo-Tethys. In this paper, the geochronological and geochemical data of the Ganluogou dioritic complex were systematically investigated in order to decipher the geodynamic setting of the complex and to further determine the final closure time of the Garzê-Litang Ocean. The Ganluogou dioritic complex is located in the northern part of the YAB. It consists of ferrodiorite, diorite and a mixing zone between them and is the largest intermediate-mafic pluton in the YAB. The ferrodiorites were emplaced at 213 ± 2 Ma have low SiO2 and high Fe2O3* contents, whereas the diorites formed at 209 ± 2 Ma and have relatively higher SiO2, Na2O + K2O, Th, U, Zr, and Hf contents, but lower Al2O3, MgO, CaO, Co, and Sr contents than the ferrodiorites. Relative to the primitive mantle both the ferrodiorites and diorites are depleted in Nb and Ta. However, the ferrodiorites exhibit strong depletion in Zr and Hf, whereas the diorites contain relatively higher Th and U contents without negative Zr and Hf anomalies. Both rock-types have similar chondrite-normalized rare earth element patterns with (La/Yb)N ratios = 4.4 to 18.2, and show weak Eu anomalies, with Eu/Eu* of 0.47 to 1. They both show narrow ranges in Sr-Nd-Hf isotopic compositions. However, the ferrodiorites contain lower initial 87Sr/86Sr ratios (0.7052-0.7057) and relatively higher εNd(t) values (- 3.8 to - 2.4) than the diorites, which record values of 0.7062-0.7066 and - 5.5 to - 5.7, respectively. For the zircon Hf isotopic composition, the ferrodiorites also exhibit higher 176Hf/177Hf ratios (0.282738-0.282804) and more depleted εHf(t) values (3.4-5.6) than

  2. Elemental geochemistry and Sr-Nd isotopic fingerprinting of sediments in monsoon dominated river systems along the west coast of India.

    NASA Astrophysics Data System (ADS)

    Pradhan, S. U.; Zhang, J.; Baskaran, M. M.; Shirodkar, P.; Wu, Y.

    2014-12-01

    water (0.7160) values, suggesting dominant authigenic origin representing the isotopic signatures of the dissolved phase of these rivers. Among the two rivers studied, the NR seems to be dominated by carbonate weathering and whereas silicate weathering dominates the NT. The contrasting differences between these two river systems serve as model for other large and small Indian rivers.

  3. 40Ar/39Ar Geochronology, Isotope Geochemistry (Sr, Nd, Pb), and petrology of alkaline lavas near Yampa, Colorado: migration of alkaline volcanism and evolution of the northern Rio Grande rift

    USGS Publications Warehouse

    Cosca, Michael A.; Thompson, Ren A.; Lee, John P.; Turner, Kenzie J.; Neymark, Leonid A.; Premo, Wayne R.

    2014-01-01

    Volcanic rocks near Yampa, Colorado (USA), represent one of several small late Miocene to Quaternary alkaline volcanic fields along the northeast margin of the Colorado Plateau. Basanite, trachybasalt, and basalt collected from six sites within the Yampa volcanic field were investigated to assess correlations with late Cenozoic extension and Rio Grande rifting. In this paper we report major and trace element rock and mineral compositions and Ar, Sr, Nd, and Pb isotope data for these volcanic rocks. High-precision 40Ar/39Ar geochronology indicates westward migration of volcanism within the Yampa volcanic field between 6 and 4.5 Ma, and the Sr, Nd, and Pb isotope values are consistent with a primary source in the Proterozoic subcontinental lithospheric mantle. Relict olivine phenocrysts have Mg- and Ni-rich cores, whereas unmelted clinopyroxene cores are Na and Si enriched with finely banded Ca-, Mg-, Al-, and Ti-enriched rims, thus tracing their crystallization history from a lithospheric mantle source region to one in contact with melt prior to eruption. A regional synthesis of Neogene and younger volcanism within the Rio Grande rift corridor, from northern New Mexico to southern Wyoming, supports a systematic overall southwest migration of alkaline volcanism. We interpret this Neogene to Quaternary migration of volcanism toward the northeast margin of the Colorado Plateau to record passage of melt through subvertical zones within the lithosphere weakened by late Cenozoic extension. If the locus of Quaternary alkaline magmatism defines the current location of the Rio Grande rift, it includes the Leucite Hills, Wyoming. We suggest that alkaline volcanism in the incipient northern Rio Grande rift, north of Leadville, Colorado, represents melting of the subcontinental lithospheric mantle in response to transient infiltration of asthenospheric mantle into deep, subvertical zones of dilational crustal weakness developed during late Cenozoic extension that have been

  4. U-Pb zircon geochronology, petrochemical and Sr-Nd isotopic characteristic of Late Neoproterozoic granitoid of the Bornaward Complex (Bardaskan-NE Iran)

    NASA Astrophysics Data System (ADS)

    Bagherzadeh, R. Monazzami; Karimpour, M. H.; Farmer, G. Lang; Stern, C. R.; Santos, J. F.; Rahimi, B.; Heidarian Shahri, M. R.

    2015-11-01

    The Bornaward Granitoid Complex (BGC) in the Taknar Zone is located in the northeast of Central Iranian Block. The BGC consists of granite, alkaligranite, syenogranite, leucogranite, granophyre, monzogranite, granodiorite, tonalite and diorite that have intruded into the center of Taknar Zone. These intrusive rocks affected by low grade metamorphism. Because of there are no reliable isotope dating data, for the Bornaward Granitoid Complex rocks have been proposed discordant ages (Jurassic, Cretaceous or even younger ages) by many studies. In the present study, new isotopic information based on zircon U-Pb dating has revealed the origin and time of the formation of the BGC. These new results do not confirm previously proposed ages. The results obtained from zircon U-Pb dating of the BGC rocks suggest late-Neoproterozoic (Precambrian) age (540-550 Ma). The Bornaward Granitoid Complex is middle-high metaluminous to lower-middle peraluminous and belongs to tholeiite, calc-alkaline to high-K calc-alkaline rock series with enrichment in LIL (Cs, Rb and Ba, U, K, Zr, Y, Th) and depletion in HIL (Sr and Nb, Ta, Ti) elements. Chondrite-normalized Rare Earth Elements (REE) plots indicate minor enrichment of LREE compared to HREE, and strong negative anomaly of Eu compared to other Rare Earth Elements. Furthermore, initial 87Sr/86Sr and 143Nd/144Nd range from 0.70351 to 0.71689 and 0.511585 to 0.512061, respectively, and initial εNd isotope values for granite, granodiorite and diorite range from -6.73 to 2.52. These all indicate that the BGC has derived from partial melting of distinct basement source regions with very high initial 87Sr/86Sr and undergoing extensive crustal contamination (S-type granite).

  5. Zircon U-Pb age and Sr-Nd-Hf-O isotope geochemistry of the Paleocene-Eocene igneous rocks in western Gangdese: Evidence for the timing of Neo-Tethyan slab breakoff

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Richards, Jeremy P.; Hou, Zeng-qian; An, Fang; Creaser, Robert A.

    2015-05-01

    Northward Neo-Tethyan oceanic lithosphere subduction beneath southern Tibet in the Mesozoic-Early Cenozoic produced continental arc magmas in the ~ 1600 km-long Gangdese belt. The most voluminous magmatism occurred in the Paleocene-Eocene, and is characterized by extensive I-type calc-alkaline to high-K calc-alkaline Linzizong volcanic rocks, and coeval plutons. These rocks have been extensively studied in the eastern Gangdese belt (east of ∼ 89°E), but few data exist from the western Gangdese belt. New data for eleven samples of these rocks, combined with existing data from the literature, show that they are similar to the eastern Gangdese belt rocks, with relative depletions in Nb, Ta, P, and Ti, and enrichments in Rb, Ba, Th, U, K, Pb, Zr, and Hf on a primitive mantle-normalized trace element diagrams, typical of continental arc-related igneous rocks. However, compared to the east, western Gangdese igneous rocks range to higher K2O contents (up to 6.1 wt.%), higher (87Sr/86Sr)i ratios (up to 0.7151), and lower εNdi values (down to - 8.1), suggesting that an evolved crustal source was involved in arc magmatism. The Gangdese arc magmatism lasted to ~ 80 Ma, and has a gap or quiescent period afterwards. Starting at ~ 69 Ma, the arc magmatism initiated and shifted southward from ~ 30.5°N to ~ 29.5°N in southern Tibet with an abrupt change of India-Asia convergence rate. The magmas through the whole Gangdese belt at ~ 69-53 Ma are characterized by intermediate εNdi values (- 0.6 to + 4.0), positive εHfi values (+ 3.8 to + 7.1), intermediate δ18O values (+ 5.0‰ to + 6.5‰), and low Th/Y and La/Yb ratios (< 20). These magmas were likely derived from the mantle with crustal contamination by MASH process in response to Neo-Tethyan slab rollback as proposed by previous studies. The Sr-Nd-Hf-O isotopic compositions of Linzizong volcanic rocks and coeval intrusions are relatively homogeneous during ~ 69-53 Ma, but show a wide range at ~ 53-50 Ma. Zircon

  6. Sr, Nd, and Pb isotopes of ultramafic xenoliths in volcanic rocks of Eastern China: enriched components EMI and EMII in subcontinental lithosphere

    USGS Publications Warehouse

    Tatsumoto, M.; Basu, A.R.; Wankang, H.; Junwen, W.; Guanghong, X.

    1992-01-01

    The UThPb, SmNd, and RbSr isotopic systematics of mafic and ultramafic xenolithic rocks and associated megacrystic inclusions of aluminous augite and garnet, that occur in three alkalic volcanic suites: Kuandian in eastern Liaoning Province, Hanluoba in Hebei Province, and Minxi in western Fujian Province, China are described. In various isotopic data plots, the inclusion data invariably fall outside the isotopic ranges displayed by the host volcanic rocks, testifying to the true xenolithic nature of the inclusions. The major element partitioning data on Ca, Mg, Fe, and Al among the coexisting silicate minerals of the xenoliths establish their growth at ambient mantle temperatures of 1000-1100??C and possible depths of 70-80 km in the subcontinental lithosphere. Although the partitioning of these elements reflects equilibrium between coexisting minerals, equilibria of the Pb, Nd, and Sr isotopic systems among the minerals were not preserved. The disequilibria are most notable with respect to the 206Pb 204Pb ratios of the minerals. On a NdSr isotopic diagram, the inclusion data plot in a wider area than that for oceanic basalts from a distinctly more depleted component than MORB with higher 143Nd 144Nd and a much broader range of 87Sr 86Sr values, paralleling the theoretical trajectory of a sea-water altered lithosphere in NdSr space. The garnets consistently show lower ?? and ?? values than the pyroxenes and pyroxenites, whereas a phlogopite shows the highest ?? and ?? values among all the minerals and rocks studied. In a plot of ??207 and ??208, the host basalts for all three areas show lower ??207 and higher ??208 values than do the xenoliths, indicating derivation of basalts from Th-rich (relative to U) sources and xenoliths from U-rich sources. The xenolith data trends toward the enriched mantle components, EMI and EMII-like, characterized by high 87Sr 86Sr and ??207 values but with slightly higher 143Nd 144Nd. The EMI trend is shown more distinctly by the host

  7. Influx of Different Galapagos Plume Components to the Galapagos Spreading Center: Evidence From Sr-Nd-Pb-Hf Isotope Variations in Axial Lavas Between 86W and 92.5W

    NASA Astrophysics Data System (ADS)

    Hauff, F.; Hanan, B.; Hoernle, K. A.; Kokfelt, T. F.; Christie, D.; Werner, R.

    2006-12-01

    We present new Sr-Nd-Pb-Hf isotope data of basaltic glasses from the GSC between 86W and 92.5W. In this part of the ridge the main structural inventory includes an overlapping spreading center (OSC) at 87.3W, a transform fault (TF) at 91W and a series of seamount chains intersecting the GSC West of the 91W TF. The systematic transition from an axial-valley and rift morphology at axial depths of 2450 m.b.s.l. in the 86W area to an axial-high morphology at progressively shallower depths of 1500 m.b.s.l in the 90.5W area together with gradational changes in major and trace element chemistry of the axial lavas is believed to reflect increasing mantle temperature and compositional changes related to the Galapagos plume [1]. Previous work from 83W to 105W revealed a broad symmetric gradational pattern at around 91W and lead to the conclusion that this region is the main point of plume influx on the GSC [2]. Based on published isotope data Christie et al. (2005) inferred the probable existence of two enrichment peaks immediately East and West of the 91TF. Indeed, along axis variations of our new Sr-Nd-Pb-Hf isotope data map two distinct peaks of enrichment at 92W and 90.5W, suggesting that mantle from the Galapagos hotspot enters the GSC melting zone on both sides of the 91W transform fault. Lavas from within the 91W TF are isotopically intermediate and show a distinct depletion in incompatible trace elements, which may reflect repeated melting at shallow depth of passively upwelling mantle in this unique extensional regime. At least three different components are required to generate the observed isotope correlations. When compared to the geographically distinct isotopic domains of the Galapagos islands; GSC lavas East of the 91W TF form tight correlations from the rim of the Central Galapagos domain through the Eastern Galapagos domain towards DMM. Most axial lavas and corresponding off axis seamounts West of the 91W TF have higher 87Sr/86Sr, 207Pb/204Pb, 208Pb/204Pb

  8. Sr-Nd-Pb isotope systematics and clinopyroxene-host disequilibrium in ultra-potassic magmas from Toro-Ankole and Virunga, East-African Rift: Implications for magma mixing and source heterogeneity

    NASA Astrophysics Data System (ADS)

    Muravyeva, N. S.; Belyatsky, B. V.; Senin, V. G.; Ivanov, A. V.

    2014-12-01

    Nd, Pb and Sr isotope ratios have been determined for kamafugite lava and clinopyroxene phenocrysts from Bunyaruguru (Toro-Ankole) and Virunga volcanic fields of the East African Rift. The whole rock Sr-Nd isotopic signatures of kamafugites (87Sr/86Sr: 0.70463-0.70536; 143Nd/144Nd: 0.51249-0.51255) suggest derivation from an EM1-type mantle source. In contrast, Pb isotopic compositions of the same samples (206Pb/204Pb: 19.00-19.57; 207Pb/204Pb: 15.69-15.74; 208Pb/204Pb: 39.30-40.26) reveal a similarity to EM2-type mantle. New Nd, Pb and Sr isotopic data for clinopyroxene (87Sr/86Sr: 0.70473-0.70503; 143Nd/144Nd: 0.51250-0.51254; 206Pb/204Pb: 18.04-18.17; 207Pb/204Pb: 15.58-15.60; 208Pb/204Pb: 38.09-38.23) suggest derivation from an EM1-like source, and indicate Sr and Pb isotope disequilibrium between clinopyroxene and corresponding host rock. Moreover, clinopyroxenes exhibiting a greater degree of isotopic disequilibrium with their host rock are more sodic in composition. The isotopic disequilibrium is corroborated by the presence of chemical zoning within clinopyroxene, which suggests rapid magma ascent rates preventing melt homogenization. The Pb isotopic ratios for both mineral and corresponding whole rock, together with published data on East African rift-related alkaline centers, define a trend interpreted to represent a mixing line for melts derived from sources such as EM1 and as HIMU. The similar isotopic compositions for clinopyroxene from the different volcanic rocks within the East African Rift suggest the existence of a common, older mantle source for their parental melts. The origin of these melts can be attributed to an enrichment event ~ 400-500 Ma, i.e., significantly prior the younger ultrapotassic magmatism. Our preferred interpretation for the results reported here involves the mixing of melts derived from EM1- and HIMU-like sources, which were rapidly transported to the Earth's surface. The primary magmas formed as the result of melting of a

  9. Zircon U-Pb geochronology and Sr-Nd isotopes of volcanic rocks from the Dahalajunshan Formation: implications for Late Devonian-Middle Carboniferous tectonic evolution of the Chinese Western Tianshan

    NASA Astrophysics Data System (ADS)

    Yu, Xinqi; Wang, Zongxiu; Zhou, Xiang; Xiao, Weifeng; Yang, Xinpeng

    2016-07-01

    The widespread Late Devonian-Middle Carboniferous volcanic rocks in the Chinese Western Tianshan provide important constraints on the subduction history of the South Tianshan oceanic lithosphere. Here, we investigate the basalt, basaltic andesite, andesite, trachyandesite, and rhyolite from the Dahalajunshan Formation from Western Tianshan. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon geochronology constrains their age of formation to between 376 and 333 Ma (i.e., Late Devonian-Middle Carboniferous) with distinct variation in space (from west to east) and time (from early to late). Based on geochemical, zircon geochronological, and Sr-Nd isotopic data, we demonstrate that the Dahalajunshan volcanic was generated in a continental arc setting associated with the subduction of the south Tianshan Ocean during Late Devonian to Middle Carboniferous. The volcanic rocks belonging to Dahalajunshan Formation in the northwestern part of the Yili Block suggest that the northward subduction of the south Tianshan Ocean was initiated in the Early Devonian; those in the southern and eastern part of the Yili Block were probably produced by a northward subduction of South Tianshan Ocean during Late Devonian to Middle Carboniferous.

  10. Hybrid genesis of Jurassic fayalite-bearing felsic subvolcanic rocks in South China: Inspired by petrography, geochronology, and Sr-Nd-O-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Guo, Chunli; Zeng, Lingsen; Li, Qiuli; Fu, Jianming; Ding, Tiping

    2016-11-01

    Fayalite-bearing felsic (FBF) magmatic rocks are a special type of granitic rocks with controversial origins. A suite of fayalite- and ferrosilite-bearing subvolcanic rocks, namely, the Xishan FBF rocks in South China, is investigated in this study. The Xishan FBF rocks have high SiO2 contents of 69-70 wt.%, high K2O/Na2O ratios of 1.71-1.95, and high FeOt/(FeOt + MgO) ratios of 0.88-0.89. Fayalite (Fo = 7.3-9.6) and ferrosilite (Fs = 74.1-76.5) minerals are found in the Xishan FBF rocks. According to the Unmix function of Isoplot, the zircon U-Pb ages and initial Hf isotope compositions are categorized into two groups with ages of 156.6 Ma and 151.5 Ma and εHf(t) values of - 7.1 and - 5.2, respectively. The minerals show δ18O values of 8.8-9.8‰ for zircon, 6.0-8.1‰ for fayalite, and 7.0-8.2‰ for ferrosilite. The oxygen isotope fractionations between ferrosilite and fayalite (ΔOpx-Ol) vary from - 0.8‰ to + 1.5‰, which indicates disequilibrium crystallization. Whole-rock analyses show high initial 87Sr/86Sr ratios of 0.7169 to 0.7180 and negative εNd(t) values of - 7.3 to - 6.8; zircon analyses show εHf(t) values of - 9.1 to - 3.8 and δ18O values of 8.8-9.8‰. So whole rock and zircon isotopes indicate a crustal signature. Based on these mineralogical and geochemical data, the Xishan FBF rocks were attributed to A-type granites and derived from the mixing of two batches of crustal magmas, which were all derived from the partial melting of ancient igneous protolith under the conditions of high temperature (683-893 °C), moderate water (3-5 wt.%), and low oxygen fugacity (lg fO2 = - 1.21). Such rigorous physical conditions may be common for the FBF igneous rocks all over the world, which may be the primary factors controlling occurrence of the FBF rocks in limited volume and quantity.

  11. A Sr, Nd, Hf, and Pb isotope perspective on the genesis and long-term evolution of alkaline magmas from Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Sims, Kenneth W. W.; Blichert-Toft, Janne; Kyle, Philip R.; Pichat, Sylvain; Gauthier, Pierre-Jean; Blusztajn, Jurek; Kelly, Peter; Ball, Lary; Layne, Graham

    2008-11-01

    We report new Nd, Hf, Sr, and high-precision Pb isotopic data for 44 lava and tephra samples from Erebus volcano. The samples cover the entire compositional range from basanite to phonolite and trachyte, and represent all three phases of the volcanic evolution from 1.3 Ma to the present. Isotopic analyses of 7 samples from Mt. Morning and the Dry Valley Drilling Project (DVDP) are given for comparison. The Erebus volcano samples have radiogenic 206Pb/ 204Pb, unradiogenic 87Sr/ 86Sr, and intermediate 143Nd/ 144Nd and 176Hf/ 177Hf, and lie along a mixing trajectory between the two end-member mantle components DMM and HIMU. The Erebus time series data show a marked distinction between the early-phase basanites and phonotephrites, whose Nd, Hf, Sr, and Pb isotope compositions are variable (particularly Pb), and the current 'phase-three' evolved phonolitic lavas and bombs, whose Nd, Hf, Sr, and Pb isotope compositions are essentially invariant. Magma mixing is inferred to play a fundamental role in establishing the isotopic and compositional uniformity in the evolved phase-three phonolites. In-situ analyses of Pb isotopes in melt inclusions hosted in an anorthoclase crystal from a 1984 Erebus phonolite bomb and in an olivine from a DVDP basanite are uniform and identical to the host lavas within analytical uncertainties. We suggest that, in both cases, the magma was well mixed at the time melt inclusions were incorporated into the different mineral phases.

  12. Sr-Nd isotope and geochemical characterisation of the Paleoproterozoic Västervik formation (Baltic Shield, SE-Sweden): a southerly exposure of Svecofennian metasiliciclastic sediments

    NASA Astrophysics Data System (ADS)

    Kleinhanns, I. C.; Fischer-Gödde, M.; Hansen, B. T.

    2012-01-01

    The Paleoproterozoic Västervik formation represents the southernmost exposure of Svecofennian metasediments and comprises a large psammitic succession of up to 5,000 m thickness dominated by quartzite with minor pelite and arkose. The Västervik formation was deposited in a time interval of ~30 m.y. from 1.88 until 1.85 Ga. Whole-rock geochemical data and Rb-Sr-Sm-Nd analyses in combination with bulk zircon U-Pb ID-TIMS studies help to gain insight into the depositional and geodynamic history of the metasiliciclastic units of the Västervik formation. Discrimination function diagrams show good agreement of major element composition with petrographic characterisation pointing towards a quartzose sedimentary provenance area with a tendency towards felsic igneous provenance. Trace element characteristics show typical upper crustal composition and remarkably similar patterns despite the respective petrographic differences. Sm-Nd isotope systematics reveal a restricted range of TDM with 2.3 ± 0.1 Ga and initial Nd (1.80 Ga) values from -4 to -2. These values are in agreement with known values from other Svecofennian sedimentary basins and support the interpretation of the Västervik formation as a typical Svecofennian metasedimentary sequence. Three samples were analysed with the zircon U-Pb ID-TIMS technique, and resulting mixing ages of ~2.1 Ga are typical for Svecofennian metasediments. The final stage of the geodynamic history of the Västervik area was a HT/LP overprint that caused intense migmatisation and anatectic production of in situ granite melts. This was accompanied by large-scale metasomatism, which led to a regional disturbance of the Rb-Sr isotope system indicating an age of ~1,750 Ma for this event. This age overlaps with timing of the tectonic activity of the Loftahammar-Linköping deformation zone (LLDZ), a large-scale deformation zone, lying directly to the north of the study area, presumably linking these two events.

  13. Petrogenesis and tectonic setting of the early Mesozoic Xitian granitic pluton in the middle Qin-Hang Belt, South China: Constraints from zircon U-Pb ages and bulk-rock trace element and Sr-Nd-Pb isotopic compositions

    NASA Astrophysics Data System (ADS)

    Wu, Qianhong; Cao, Jingya; Kong, Hua; Shao, Yongjun; Li, Huan; Xi, Xiaoshuang; Deng, Xuantong

    2016-10-01

    The Xitian pluton in southeast Hunan province is one of the early Mesozoic (Indosinian) granitic plutons in the South China Block. It is composed of biotite adamellite with K-feldspar megacrysts, biotite adamellite, and biotite granite that have U-Pb zircon ages of 229.9 ± 1.4 Ma, 223.6 ± 1.3 Ma, and 224.0 ± 1.4 Ma, respectively. The Indosinian granitoids in the Xitian pluton belong to S-type granites, with highly radiogenic initial 87Sr/86Sr ratios (0.71397-0.71910), negative εNd(t) values ranging from -10.1 to -9.4, and old Nd model ages (1858-1764 Ma). They are enriched in radiogenic Pb isotopes, with (206Pb/204Pb)t ranging from 18.130 to 18.903, (207Pb/204Pb)t from 15.652 to 15.722, and (208Pb/204Pb)t from 38.436 to 39.037, respectively. These features indicate that the granitoidswithin the Xitian pluton were formed from magmas generated by remelting of metapelite and metapsammite of the Paleoproterozoic metamorphic basement at temperatures of ca. 800 °C, with low oxygen fugacity. The Sr-Nd isotopic compositions of the rocks from Xitian pluton indicate that the granitic magmas were mixed with less than 10% mantle-derived magmas. We suggest that the Xitian pluton was emplaced in an extensional tectonic setting related to release of compressional stresses within the thickened crust during the early Mesozoic.

  14. The role of crustal contamination in the formation of Ni-Cu sulfide deposits in Eastern Tianshan, Xinjiang, Northwest China: Evidence from trace element geochemistry, Re-Os, Sr-Nd, zircon Hf-O, and sulfur isotopes

    NASA Astrophysics Data System (ADS)

    Tang, Dong-Mei; Qin, Ke-Zhang; Sun, He; Su, Ben-Xun; Xiao, Qing-Hua

    2012-04-01

    Tulaergen, Xiangshan, Huangshan, Tianyu, and Baishiquan magmatic Ni-Cu sulfide deposits, which are all located in the eastern part of the Central Asian Orogenic Belt, and associated with small mafic-ultramafic intrusions with high-grade Cu and Ni orebodies have similar ages of formation. Their magma sources are MORB-like and OIB-like depleted mantle. Modeling calculations of Sr-Nd and zircon Hf isotopic data show that about 10-15% of oceanic slab components are added into the source of Baishiquan and Tianyu intrusions, but only less than 5% are in the three other intrusions. The higher degree of subduction metasomatism in the Baishiquan and Tianyu magma sources is likely the result of the Paleozoic multiple-stage subduction. Moreover, the relative enrichment of LILE, depletion of HFSE, and lower Ce/Pb ratios indicate that these intrusions experienced crustal contaminations. The effects of crustal contamination are also identified in the magmatic sulfide deposits by the higher zircon δ18O, higher sulfide γOs, and δ34S values observed. We propose a two-stage crustal contamination model of the Tulaergen, Xiangshan, Tianyu, and Baishiquan intrusions. However, the Huangshan intrusion, which has the highest degree of crustal contamination, likely experienced only single-stage upper crustal contamination (˜14.2%). The addition of crustal S appears to be directly related to triggering S saturation in these deposits. According to a simple S isotopic modeling calculation, 11%, 2.9%, 1.2% and 2.1% of the crustal sulfur addition into the parental magma would be required to form the Tianyu, Baishiquan, Xiangshan, and Tulaergen deposits, respectively.

  15. Whole-rock geochemistry and Sr-Nd-Pb isotope systematics of the Late Carboniferous volcanic rocks of the Awulale metallogenic belt in the western Tianshan Mountains (NW China): Petrogenesis and geodynamical implications

    NASA Astrophysics Data System (ADS)

    Ge, Songsheng; Zhai, Mingguo; Safonova, Inna; Li, Dapeng; Zhu, Xiyan; Zuo, Pengfei; Shan, Houxiang

    2015-07-01

    The Awulale metallogenic belt (AMB) of the western Tianshan (NW China) includes Late Carboniferous (ca. 320 Ma) ore-bearing volcanic rocks of the Dahalajunshan Formation. The petrogenesis and tectonic setting of these volcanic rocks are important for the understanding of the tectonic evolution and metallogeny of the western Tianshan. This paper presents new major and trace elements and Sr-Nd-Pb isotope data from the Dahalajunshan volcanic rocks, which are mainly calc-alkaline basaltic trachy-andesite and trachy-andesite with subordinate basalt, trachy-basalt and rhyolite. The variations of major and trace elements in the mafic and intermediate volcanic rocks indicate the fractionation of pyroxene and magnetite or hornblende, magnetite, apatite and plagioclase, respectively, during their petrogenesis. The Dahalajunshan volcanic rocks have similar primitive mantle-normalized diagrams and chondrite-normalized rare-earth element (REE) patterns suggesting their similar mantle source(s). They are characterized by enrichment in large ion lithophile elements (LILEs) and light REEs (LREEs), depletion in heavy REEs (LaN/YbN ≈ 2.80 to 9.59) and high field strength elements (HFSEs) and εNd(t) ranging from + 1.2 to + 6.0 at 86Sr/87Sr(t) = 0.7047-0.7063 and 206Pb/204Pbi = 17.49-18.19. Both the geochemical and isotopic data indicate that the volcanic rocks were probably derived by low-degree melting of sub-arc lithospheric mantle modified by fluids in a continental arc setting. Our obtained results, in conjunction with previous published data, allow us to suggest that the southward subduction of Junggar oceanic crust continued until the Late Carboniferous and was followed by a tectonic shift from continental arc to post-collisional extension environment.

  16. Chapter 9 The magma feeding system of Somma-Vesuvius (Italy) strato-volcano: new inferences from a review of geochemical and Sr, Nd, Pb and O isotope data

    USGS Publications Warehouse

    Piochi, M.; de Vivo, B.; Ayuso, R.A.

    2006-01-01

    A large database of major, trace and isotope (Sr, Nd, Pb, O) data exists for rocks produced by the volcanic activity of Somma-Vesuvius volcano. Variation diagrams strongly suggest a major role for evolutionary processes such as fractional crystallization, contamination, crystal trapping and magma maxing, occurring after magma genesis in the mantle. Most mafic magmas are enriched in LILE (Light Ion Lithophile Elements; K. Rb, Ba), REE (Ce, Sm) and Y, show small Nb-Ta negative anomalies, and have values of Nb/Zr at about 0.15. Enrichments in LILE, REE, Nb and Ta do not correlate with Sr isotope values or degree of both K enrichment and silica undersaturation. The results indicate mantle source heterogeneity produced by slab-derived components beneath the volcano. However, the Sr isotope values of Somma-Vesuvius increase from 0.7071 up to 0.7081 with transport through the uppermost 11-12 km of the crust. The Sr isotope variation suggests that the crustal component affected the magmas during ascent through the lithosphere to the surface. Our new geochemical assessment based on chemical, isotopic and fluid inclusion data points to the existence of three main levels of magma storage. Two of the levels are deep and may represent long-lived reservoirs; the uppermost crustal level probably coincides with the volcanic conduit. The deeper level of magma storage is deeper than 12 km and fed the 1944 AD eruption. The intermediate level coincides with the seismic discontinuity detected by Zollo et al. (1996) at about 8 km. This intermediate level supplies magmas with 87Sr/86Sr values between 0.7071 and 0.7074, and ??O18<8% that typically erupted both during interplinian (i.e. 1906 AD) and sub-plinian (472 AD, 1631 AD) events. The shallowest level of magma storage at about 5 km was the site of magma chambers for the Pompei and Avellino plinian eruptions. New investigations are necessary to verify the proposed magma feeding system. ?? 2006 Elsevier B.V. All rights reserved.

  17. Petrogenesis of synorogenic diorite-granodiorite-granite complexes in the Damara Belt, Namibia: Constraints from U-Pb zircon ages and Sr-Nd-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Jung, S.; Kröner, A.; Hauff, F.; Masberg, P.

    2015-01-01

    The synorogenic Palmental complex (central Damara Belt, Nambia) consists of ca. 545 Ma old quartz diorites and rare granodiorites and ca. 520 Ma-old leucogranites, representing one of the earliest and most primitive phase of crustal plutonism predating the main high-T regional metamorphism. Most quartz diorites and one granodiorite evolved through multistage, polybaric evolutionary processes involving fractionation from a lithospheric mantle-derived melt, followed by fractional crystallization of mainly hornblende, plagioclase and apatite which is shown by decreasing MgO, FeO, CaO, TiO2 and P2O5 with increasing SiO2. Assimilation of felsic basement gneisses was also important during formation of these granitoids. Although their chemical characteristics (high LILE, low HFSE) resemble those of quartz diorites and granodiorites with calc-alkaline affinity, they differ in their enriched Sr (initial 87Sr/86Sr: 0.7061-0.7098) and Nd (initial εNd: -2.7 to -9.9) isotopic composition. Neodymium depleted mantle mean crustal residence ages range from 1.3 to 1.9 Ga for the quartz diorites including the granodiorite. These model ages correlate with major and trace element abundances, further substantiating that AFC processes modified the initial isotopic systematics. Lead (206Pb/204Pb: 17.43-17.68, 207Pb/204Pb: 15.61-15.66, 208Pb/204Pb: 38.19-38.49) isotopic composition are unradiogenic relative to other Damaran intrusive rocks but plot above the Stacey and Kramers (1975) reference line, indicating that the source underwent an ancient (pre Pan-African) increase in U/Pb and Th/U, followed by more recent U-depletion. Some variation in 206Pb/204Pb at high 207Pb/204Pb further indicates involvement of ancient crustal material, most likely through AFC processes. A cross-cutting leucogranite dyke has also evolved isotopic compositions (initial 87Sr/86Sr: 0.7326; initial εNd: -15.6; 206Pb/204Pb: 17.42, 207Pb/204Pb: 15.62, 208Pb/204Pb: 38.16) but in view of the apparent younger age of

  18. Speculations on nature and extent of Archean basement in Labrador as indicated by SR, ND and PB isotopic systematics of proterozoic intrusives

    NASA Technical Reports Server (NTRS)

    Ashwal, L. D.; Wooden, J. L.; Emslie, R. F.

    1986-01-01

    The Sm-Nd and Rb-Sr isotopic compositions of mid to late Proterozoic (approximately 1.6 to 1.1 Ga) massif-type anorthosites and mafic intrusives in the eastern Canadian shield are correlated with geographic location. Complexes in the Grenville province have positive epsilon sub Nd values and initial Sr-87/Sr-86 (I sub Sr) generally less than 0.703, suggesting derivation from depleted mantle. In Labrador, similar complexes close to or northwest of a line roughly corresponding to the Grenville Front have negative epsilon sub Nd values and I sub Sr 0.703. This contrast was intrepreted as reflecting either enriched mantle under the Nain Province, or contamination of the Nain intrusives with older crustal components. Lead isotopic compositions, however, favor the latter. The possibility of using these Proterozoic intrusives as tracers to characterize the nature and extent of older basement types in Labrador is discussed.

  19. Petrogenesis of gold-mineralized magmatic rocks of the Taerbieke area, northwestern Tianshan (western China): Constraints from geochronology, geochemistry and Sr-Nd-Pb-Hf isotopic compositions

    NASA Astrophysics Data System (ADS)

    Tang, Gong-Jian; Wang, Qiang; Wyman, Derek A.; Sun, Min; Zhao, Zhen-Hua; Jiang, Zi-Qi

    2013-09-01

    Many Late Paleozoic Cu-Au-Mo deposits occur in the Central Asian Orogenic Belt (CAOB). However, their tectonic settings and associated geodynamic processes have been disputed. This study provides age, petrologic and geochemical data for andesites and granitic porphyries of the Taerbieke gold deposit from the Tulasu Basin, in the northwestern Tianshan Orogenic Belt (western China). LA-ICP-MS zircon U-Pb dating indicates that the granitic porphyries have an Early Carboniferous crystallization age (349 ± 2 Ma) that is broadly contemporaneous with the eruption age (347 ± 2 Ma) of the andesites. The andesites have a restricted range of SiO2 (58.94-63.85 wt.%) contents, but relatively high Al2O3 (15.39-16.65 wt.%) and MgO (2.51-6.59 wt.%) contents, coupled with high Mg# (57-69) values. Geochemically, they are comparable to Cenozoic sanukites in the Setouchi Volcanic Belt, SW Japan. Compared with the andesites, the granitic porphyries have relatively high SiO2 (72.68-75.32 wt.%) contents, but lower Al2O3 (12.94-13.84 wt.%) and MgO (0.10-0.33 wt.%) contents, coupled with lower Mg# (9-21) values. The andesites and granitic porphyries are enriched in both large ion lithophile and light rare earth elements, but depleted in high field strength elements, similar to those of typical arc magmatic rocks. They also have similar Nd-Hf-Pb isotope compositions: ɛNd(t) (+0.48 to +4.06 and -0.27 to +2.97) and zircons ɛHf(t) (+3.4 to +8.0 and -1.7 to +8.2) values and high (206Pb/204Pb)i (18.066-18.158 and 17.998-18.055). We suggest that the Taerbieke high-Mg andesitic magmas were generated by the interaction between mantle wedge peridotites and subducted oceanic sediment-derived melts with minor basaltic oceanic crust-derived melts, and that the magmas then fractionated to produce the more felsic members (i.e., the Taerbieke granitic porphyries) during late-stage evolution. Taking into account the Carboniferous magmatic record from the western Tianshan Orogenic Belt, we suggest that

  20. Anthropogenic versus natural control on trace element and Sr-Nd-Pb isotope stratigraphy in peat sediments of southeast Florida (USA), ˜1500 AD to present

    NASA Astrophysics Data System (ADS)

    Kamenov, George D.; Brenner, Mark; Tucker, Jaimie L.

    2009-06-01

    Analysis of a well-dated peat core from Blue Cypress Marsh (BCM) provides a detailed record of natural and anthropogenic factors that controlled the geochemical cycles of a number of trace elements in Florida over the last five centuries. The trace elements were divided into "natural" and "anthropogenic" groups using concentration trends from the bottom to the top of the core. The "natural" group includes Li, Sc, Cr, Co, Ga, Ge, Zr, Nb, Cs, Ba, Hf, Y, Ta, Th, and REE (Rare Earth Elements). These elements show similar concentrations throughout the core, indicating that changes in human activities after European arrival in the "New World" did not affect their geochemical cycles. The "anthropogenic" group includes Pb, Cu, Zn, V, Sb, Sn, Bi, and Cd. Upcore enrichment of these elements indicates enhancement by anthropogenic activities. From the early 1500s to present, fluxes of the "anthropogenic" metals to the marsh increased significantly, with modern accumulation rates several-fold (e.g., V) to hundreds of times (e.g., Zn) greater than pre-colonial rates. The dominant input mechanism for trace elements from both groups to the marsh has been atmospheric deposition. Atmospheric input of a number of the elements, including the anthropogenic metals, was dominated by local sources during the last century. For several elements, long-distant transport may be important. For instance, REE and Nd isotopes provide evidence for long-range atmospheric transport dominated by Saharan dust. The greatest increase in flux of the "anthropogenic" metals occurred during the 20th century and was caused by changes in the chemical composition of atmospheric deposition entering the marsh. Increased atmospheric inputs were a consequence of several anthropogenic activities, including fossil fuel combustion (coal and oil), agricultural activities, and quarrying and mining operations. Pb and V exhibit similar trends, with peak accumulation rates in 1970. The principal anthropogenic source of V

  1. Sr-Nd isotope data of basement rocks from the northernmost argentine Precordillera and its implications for the early Paleozoic evolution of SW Gondwana margin

    NASA Astrophysics Data System (ADS)

    Martina, Federico; Astini, Ricardo A.; Pimentel, Marcio M.

    2014-12-01

    The Precordillera terrane (Cuyania) in western Argentina is commonly accepted as an exotic fragment derived from Laurentia in the Early Paleozoic. Evidence supporting such an interpretation is manly based on similarities in the sedimentary cover successions and their paleontological content. Little is known about the basement of the Precordillera terrane. Its isotopic characterization is essential to better constrain the present areal distribution of the terrane and it may provide more insight into the pre-rifting evolution of the Precordillera terrane along the Iapetan margin of Laurentia. We present new Sr and Nd isotope data of pre-Late Ordovician meta-igneous rocks from the Río Bonete region in NW Argentina, interpreted as the northernmost extent of the Precordillera. The Nd systematics of the Río Bonete basement rocks including greenschists and metagabbros (ɛNd(470) = +2.14--0.19; TDM = 0.99-1.2 Ga), a garnet-amphibolite (ɛNd(470) = -0.53; TDM = 1.32 Ga) and a quartz-phyllite (ɛNd(470) = -3.83; TDM = 1.55 Ga), are similar to other pre-Ordovician meta-igneous rocks from Sierra de Umango, Pie de Palo and the Ullum xenoliths, usually interpreted as the basement of the Precordillera terrane. Nd model ages around 1.2 Ga are also typical from the Mesoproterozoic Grenvillian basement of southern North America, currently exposed in the Llano region. In addition, the greenschists and metagabbros show a robust correlation with the Late Neoproterozoic Catoctin volcanics in the central Appalachians. The Sr isotope data (when not disturbed) also supports this novel interpretation and suggests the presence of the Blue Ridge rifting event in Precordillera. According to our interpretation, some lithotypes included within the basement complex of the Río Bonete area belonged to the basement of the Precordillera terrane supporting previous correlation between both regions.

  2. Sr-Nd-Pb-Hf isotope results from ODP Leg 187: evidence for mantle dynamics of the Australian-Antarctic Discordance

    NASA Astrophysics Data System (ADS)

    Kempton, P. D.; Pearce, J. A.; Barry, T. L.; Fitton, J. G.; Langmuir, C. H.; Christie, D. M.

    2003-04-01

    New high precision PIMMS Hf and Pb isotope data for 14-28 Ma basalts recovered during ODP Leg 187 are compared with zero-age dredge samples from the Australian-Antarctic Discordance (AAD) in order to extend the characterization of the Indian/Pacific mantle domain boundary from on-axis to older (14-28 Ma) off-axis crust and to address questions relating to the origin and evolution of the AAD. Based on our new Nd-Hf isotope data we demonstrate that Pacific MORB-source mantle (PMM) was present near the eastern margin of the AAD from as early as 28 Ma―its boundary with Indian MORB-source mantle (IMM) coinciding with the eastern edge of a basin-wide arcuate depth anomaly that is centered on the AAD. This observation rules out models requiring rapid migration of Pacific MORB mantle into the Indian Ocean basin since separation of Australia from Antarctica. Although PMM does not occur west of the fracture zone at 127^oE, IMM is recovered along with PMM up to 100 km east of this transform; at two localities, basalts derived from both mantle domains occur within the same site. Even here, however, IMM and PMM retain their compositional distinctiveness, indicating that the boundary between the two mantle domains is remarkably sharp. Hf isotope data also place constraints on the origin of the mantle reservoirs underlying the AAD. Nd-Hf isotope systematics can be explained by a model in which IMM basalts from the AAD are derived from mantle previously processed above a subduction zone. Such mantle could have been generated within the convergent margin that existed off the east coast of Gondwana throughout most of the Paleozoic and Mesozoic Eras and subsequently recycled into the upper mantle. Upwelling of a stagnated, subducted slab beneath the SEIR (Gurnis et al., 1998) is responsible for the progressive displacement of low-eHf (lithosphere-contaminated) IMM by high-eHf (uncontaminated but subduction-processed) IMM. Gurnis, M., R. D. Muller, R.D., &L. Moresi, Science, 279

  3. Zircon U-Pb geochronological, geochemical, and Sr-Nd isotope data for Early Cretaceous mafic dykes in the Tancheng-Lujiang Fault area of the Shandong Province, China: Constraints on the timing of magmatism and magma genesis

    NASA Astrophysics Data System (ADS)

    Liu, Shen; Feng, Caixia; Hu, Ruizhong; Zhai, Mingguo; Gao, Shan; Lai, Shaocong; Yan, Jun; Coulson, Ian M.; Zou, Haibo

    2015-02-01

    The timing and source of magmatism that formed Early Cretaceous dolerite dykes in the Tancheng-Lujiang (Tan-Lu) Fault area of the southeastern North China Craton was determined using geochronological, geochemical, and whole-rock Sr-Nd isotopic data. Laser ablation-inductively coupled plasma-mass (LA-ICP-MS) spectrometry U-Pb analysis of zircon yielded consistent ages of 129.6 ± 0.7, 126.8 ± 0.7, 125.5 ± 0.7, 124.9 ± 0.9, 126.4 ± 0.7, and 125.5 ± 0.7 Ma for six samples of the mafic dykes within the NCC. The K2O + Na2O concentrations (5.02-5.21 wt.%) of the dykes indicate they are alkaline and these dykes have K2O concentrations (2.35-2.48 wt.%) that indicate they are shoshonitic. These dolerites are also characterized by high and wide ranging (La/Yb)N (14.5-36.0), have slightly negative Eu anomalies (δEu = 0.70-0.91) and positive Ba, U, K, and Pb anomalies, and are depleted in the high field strength elements (Nb, Ta, P, and Ti). In addition, these mafic dykes are characterized by high radiogenic Sr [(87Sr/86Sr)i = 0.7099-0.7100] and negative εNd (t) values (-14.4 to -13.7). These data suggest that the magmas that formed the dykes were derived through the partial melting (12.0-15.0%) of an enriched region of the mantle that was hybridized during interaction with subducted sedimentary rocks from the Yangtze Craton. The parental magmas then fractionated olivine and Fe-Ti oxides during ascent and underwent negligible crustal contamination during magma emplacement. These mafic magmas were finally emplaced as dyke swarms associated with lithospheric extension.

  4. Zircon U-Pb geochronology and Sr-Nd-Hf isotopic compositions of the Yuanzhuding granitoid porphyry within the Shi-Hang Zone, South China: Petrogenesis and implications for Cu-Mo mineralization

    NASA Astrophysics Data System (ADS)

    Zhong, Lifeng; Li, Jie; Peng, Touping; Xia, Bin; Liu, Liwen

    2013-09-01

    The Shi-Hang Zone is an important NE-SW-trending Mesozoic magmatic belt in South China, which is dominated by granites with relatively high εNd(t) values and young TDM model ages. Here, we present laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb ages, major and trace element compositions, and Sr-Nd-Hf isotope data for the Yuanzhuding porphyritic granitoids within the southwestern Shi-Hang Zone, and use these data to determine the origin of this granitoid and its relationship with Cu-Mo mineralization. Zircon U-Pb dating indicates that these granitoids were emplaced at 157.8 ± 1.1 Ma. They have initial 87Sr/86Sr ratios of 0.70941-0.71398, εNd(t) values of - 3.15 to - 2.02, and in situ zircon εHf(t) values of + 1.71 to + 6.17. Geochemically, most of them are high-K calc-alkaline and show an adakitic affinity. They are more likely emplaced in a continental arc setting related to westward subduction of the paleo-Pacific plate. Their parental magma originated chiefly from the overlying sediments of the downgoing slab, and subsequently interacted with the lithospheric mantle wedge at the temperatures of ~ 790 °C. High oxygen fugacity during magmatic evolution played a crucial role in the development of Cu-Mo mineralization within the Yuanzhuding. The discovery of the Yuanzhuding deposit implies that the Chenzhou-Huaiji fault belt is most likely prospective for mineral exploration for porphyry Cu-Mo deposits.

  5. Trace-element and Sr, Nd, Pb, and O isotopic composition of Pliocene and Quaternary alkali basalts of the Patagonian Plateau lavas of southernmost South America

    USGS Publications Warehouse

    Stern, C.R.; Frey, F.A.; Futa, K.; Zartman, R.E.; Peng, Z.; Kurtis, Kyser T.

    1990-01-01

    The Pliocene and Quaternary Patagonian alkali basalts of southernmost South America can be divided into two groups. The "cratonic" basalts erupted in areas of Cenozoic plateau volcanism and continental sedimentation and show considerable variation in 87Sr/86Sr (0.70316 to 0.70512), 143Nd/144Nd (e{open}Nd) and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios (18.26 to 19.38, 15.53 to 15.68, and 38.30 to 39.23, respectively). These isotopic values are within the range of oceanic island basalts, as are the Ba/La, Ba/Nb, La/Nb, K/Rb, and Cs/Rb ratios of the "cratonic" basalts. In contrast, the "transitional" basalts, erupted along the western edge of the outcrop belt of the Pliocene and Quaternary plateau lavas in areas that were the locus of earlier Cenozoic Andean orogenic arc colcanism, have a much more restricted range of isotopic composition which can be approximated by 87Sr/86Sr=0.7039??0.0004, e{open}Nd, 206Pb/204Pb=18.60??0.08, 207Pb/204Pb=15.60??0.01, and 208Pb/204Pb=38.50??0.10. These isotopic values are similar to those of Andean orogenic are basalts and, compared to the "cratonic" basalts, are displaced to higher 87Sr/86Sr at a given 143Nd/144Nd and to higher 207Pb/204Pb at a given 208Pb/204Pb. The "transitional" basalts also have Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios higher than the "cratonic" and oceanic island basalts, although not as high as Andean orogenic are basalts. In contrast to the radiogenic isotopes, ??18O values for both groups of the Patagonian alkali basalts are indistinguishable and are more restricted than the range reported for Andean orogenic are basalts. Whole rock ??18O values calculated from mineral separates for both groups range from 5.3 to 6.5, while measured whole rock ??18O values range from 5.1 to 7.8. The trace element and isotopic data suggest that decreasing degrees of partial melting in association with lessened significance of subducted slabderived components are fundamental factors in the west to east transition from arc

  6. Late Cenozoic volcanism in the western Woodlark Basin area, SW Pacific: the sources of marine volcanic ash layers based on their elemental and Sr-Nd isotope compositions

    NASA Astrophysics Data System (ADS)

    Lackschewitz, K. S.; Mertz, D. F.; Devey, C. W.; Garbe-Schönberg, C.-D.

    2002-12-01

    Tephra fallout layers and volcaniclastic deposits, derived from volcanic sources around and on the Papuan Peninsula, form a substantial part of the Woodlark Basin marine sedimentary succession. Sampling by the Ocean Drilling Program Leg 180 in the western Woodlark Basin provides the opportunity to document the distribution of the volcanically-derived components as well as to evaluate their chronology, chemistry, and isotope compositions in order to gain information on the volcanic sources and original magmatic systems. Glass shards selected from 57 volcanogenic layers within the sampled Pliocene-Pleistocene sedimentary sequence show predominantly rhyolitic compositions, with subordinate basaltic andesites, basaltic trachy-andesites, andesites, trachy-andesites, dacites, and phonolites. It was possible to correlate only a few of the volcanogenic layers between sites using geochemical and age information apparently because of the formation of strongly compartmentalised sedimentary realms on this actively rifting margin. In many cases it was possible to correlate Leg 180 volcanic components with their eruption source areas based on chemical and isotope compositions. Likely sources for a considerable number of the volcanogenic deposits are Moresby and Dawson Strait volcanoes (D'Entrecasteaux Islands region) for high-K calc-alkaline glasses. The Dawson Strait volcanoes appear to represent the source for five peralkaline tephra layers. One basaltic andesitic volcaniclastic layer shows affinities to basaltic andesites from the Woodlark spreading tip and Cheshire Seamount. For other layers, a clear identification of the sources proved impossible, although their isotope and chemical signatures suggest similarities to south-west Pacific subduction volcanism, e.g. New Britain and Tonga-Kermadec island arcs. Volcanic islands in the Trobriand Arc (for example, Woodlark Island Amphlett Islands and/or Egum Atoll) are probable sources for several volcaniclastic layers with ages

  7. Petrogenesis of Sierra Nevada plutons inferred from the Sr, Nd, and O isotopic signatures of mafic igneous complexes in Yosemite Valley, California

    NASA Astrophysics Data System (ADS)

    Nelson, Wendy R.; Dorais, Michael J.; Christiansen, Eric H.; Hart, Garret L.

    2013-02-01

    Mafic complexes in the central Sierra Nevada batholith record valuable geochemical information regarding the role mafic magmas play in arc magmatism and the generation of continental crust. In the intrusive suite of Yosemite Valley, major and trace element compositions of the hornblende-bearing gabbroic rocks from the Rockslides mafic complex and of the mafic dikes in the North America Wall are compositionally similar to high-alumina basalt. Of these rocks, two samples have higher Ni and Cr abundances as well as higher ɛNd values than previously recognized for the intrusive suite. Plagioclase crystals in rocks from the North America Wall and the Rockslides have prominent calcic cores and sharply defined sodic rims, a texture commonly associated with mixing of mafic and felsic magmas. In situ analyses of 87Sr/86Sr in plagioclase show no significant isotopic difference from the cores to the rims of these grains. We propose that the high 87Sr/86Sr (~0.7067) and low ɛNd (~-3.4) of bulk rocks, the homogeneity of 87Sr/86Sr in plagioclase, and the high δ18O values of bulk rocks (6.6-7.3 ‰) and zircon (Lackey et al. in J Petrol 49:1397-1426, 2008) demonstrate that continental crust was assimilated into the sublithospheric mantle-derived basaltic precursors of the mafic rocks in Yosemite Valley. Contamination (20-40 %) likely occurred in the lower crust as the magma differentiated to high-alumina basalt prior to plagioclase (and zircon) crystallization. As a consequence, the isotopic signatures recorded by whole rocks, plagioclase, and zircon do not represent the composition of the underlying lithospheric mantle. We conclude that the mafic and associated felsic members of the intrusive suite of Yosemite Valley represent 60-80 % new additions to the crust and include significant quantities of recycled ancient crust.

  8. Geological, geochronological, geochemical, and Sr-Nd-O-Hf isotopic constraints on origins of intrusions associated with the Baishan porphyry Mo deposit in eastern Tianshan, NW China

    NASA Astrophysics Data System (ADS)

    Wang, Yinhong; Xue, Chunji; Liu, Jiajun; Zhang, Fangfang

    2016-10-01

    The Baishan porphyry Mo deposit (0.72 Mt; 0.06 % Mo) is located in the interior of the eastern Tianshan orogenic belt in Xinjiang, NW China. The deposit comprises 15 orebodies that are associated with monzogranite and granite porphyry stocks and are structurally controlled by roughly EW-trending faults. Secondary ion mass spectrometry (SIMS) zircon U-Pb dating of the monzogranite and granite porphyry yielded the Middle Triassic age (228 ± 2 to 227 ± 2 Ma), which coincide with the molybdenite Re-Os model ages ranging from 226 ± 3 to 228 ± 3 Ma. The Triassic monzogranite and granite porphyry belong to high-K calc-alkaline series and are characterized by high SiO2 and Al2O3 and low MgO, TiO2, and P2O5 concentrations, with negative Eu anomalies (δEu = 0.55-0.91). The least-altered monzogranite and granite porphyry yield uniform ɛ Nd( t) values from +1.6 to +3.6, and wide (87Sr/86Sr) i ratios ranging between 0.7035 and 0.7071, indicating that they were derived from the lower crust. In situ O-Hf isotopic analyses on zircon using SIMS and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) indicate that the δ18O and ɛ Hf( t) values of zircon from a monzogranite sample vary from 6.1 to 7.3 ‰ and +8.0 to +11.7, respectively, whereas zircon from a granite porphyry sample vary from 6.2 to 6.9 ‰ and +7.3 to +11.2, respectively. The geochemical and isotopic data imply that the primary magmas of the Baishan granite were likely derived from partial melts from the lower crust involving some mantle components. The Baishan Mo deposit and granitic emplacement were proposed to be most likely related to post-orogenic lithospheric extension and magmatic underplating. An extensional event coupled with the rising of hot mantle-derived melts triggered partial melting of the lower crust, as well as provided metals (Mo).

  9. Geochemistry and Sr-Nd isotopic compositions of mantle xenoliths from the Monte Vulture carbonatite-melilitite volcano, central southern Italy

    NASA Astrophysics Data System (ADS)

    Downes, H.; Kostoula, T.; Jones, A. P.; Beard, A. D.; Thirlwall, M. F.; Bodinier, J.-L.

    2002-08-01

    Spinel peridotite xenoliths found in the Monte Vulture carbonatite-melilitite volcano have been derived from the subcontinental lithospheric mantle beneath central southern Italy. Clinopyroxene-poor lherzolites and harzburgites are the most common rock types, with subordinate wehrlites and dunites. Small quantities of phlogopite and carbonate are present in a few samples. The peridotites record a large degree of partial melting and have experienced subsequent enrichment which has increased their LILE and LREE contents, but in most cases their HFSE contents are low. Despite being carried to the surface by a carbonatite-melilitite host, the whole-rock and clinopyroxene compositions of the xenoliths have a trace-element signature more closely resembling that of silicate-melt metasomatised mantle rather than carbonatite-metasomatised peridotites. 87Sr/86Sr and 143Nd/144Nd isotopic ratios for clinopyroxene from the Vulture peridotites are 0.7042-0.7058 and 0.51260-0.5131 respectively. They form a trend away from the depleted mantle to the composition of the host magmas, and show a significant enrichment in 87Sr/86Sr compared with most European mantle samples. The mantle beneath Monte Vulture has had a complex evolution - we propose that the lithosphere had already undergone extensive partial melting before being affected by metasomatism from a silicate melt which may have been subduction-related.

  10. Geochemical and Sr-Nd-Pb-O isotope composition of granitoids of the Early Cretaceous Copiapó plutonic complex (27°30'S), Chile

    NASA Astrophysics Data System (ADS)

    Marschik, Robert; Fontignie, Denis; Chiaradia, Massimo; Voldet, Pia

    2003-10-01

    Early Cretaceous plutonic rocks exposed south of Copiapó form part of the Coastal Batholith of northern Chile. These rocks intrude arc-derived volcanic and volcaniclastic rocks and marine limestones that were deposited in the Early Cretaceous Atacama backarc basin. The Copiapó plutonic complex consists mainly of calc-alkaline, medium- to coarse-grained diorite, granodiorite, tonalite, monzodiorite, and quartz monzonite. The plutonic rocks are subalkaline to alkaline, metaluminous, magnetite-series, volcanic arc, I-type granitoids. Batholithic magmas are a heat, potential fluid, metal, and sulphur source for the hydrothermal iron oxide-rich Cu-Au mineralization in the Candelaria-Punta del Cobre district. Ore-related hydrothermal alteration affected large portions of the Copiapó complex. The least altered batholithic rocks have initial 87Sr/ 86Sr of 0.703070-0.703231; initial 143Nd/ 144Nd of 0.512733-0.512781; and 206Pb/ 204Pb, 207Pb/ 204Pb, and 208Pb/ 204Pb of 18.428-18.772, 15.550-15.603, and 38.127-38.401, respectively. The δ18O values for these rocks range from +6.9 to +8.6‰. Isotope signatures and trace element distributions suggest that the magmas are mantle derived. A subduction fluid-modified mantle source may explain the geochemical characteristics of the Copiapó complex. The ascent of magmas occurred along deep-rooted structures without significant crustal contamination, though minor contamination by relatively young (e.g. Jurassic) igneous rocks during ascent is possible. Intrusive rocks with high-K to shoshonitic characteristics probably represent residual liquids of less evolved magmas. The regional geologic context suggests that the plutons of the Copiapó complex were emplaced at a relatively shallow crustal level of 2-3 km.

  11. Depletion, cryptic metasomatism, and modal metasomatism (refertilization) of Variscan lithospheric mantle: Evidence from major elements, trace elements, and Sr-Nd-Os isotopes in a Saxothuringian garnet peridotite

    NASA Astrophysics Data System (ADS)

    Gordon Medaris, L.; Ackerman, Lukáš; Jelínek, Emil; Michels, Zachary D.; Erban, Vojtěch; Kotková, Jana

    2015-06-01

    Orogenic garnet peridotites of diverse origins and histories in the Bohemian Massif attest to a variety of mantle processes, including partial melting, cryptic metasomatism, and modal metasomatism (refertilization), all of which are recorded by Saxothuringian garnet peridotite from the T-7 borehole in northern Bohemia. The T-7 peridotite consists of interlayered garnet lherzolite, harzburgite, and phlogopite-garnet pyroxenite lenses that yield peak temperatures and pressures of 1030-1150 °C and 36.1-48.0 kbar. Olivine crystallographic preferred orientations exhibit [axial](010) slip, corresponding to a pure shear component of deformation under relatively low flow stress conditions. Some lherzolite samples are fertile, resembling primitive mantle in major and trace element composition, but other lherzolites are slightly depleted in incompatible major elements, HREE, and HFSE, and slightly enriched in LREE. Harzburgite is depleted in incompatible major elements, HREE, and HFSE, but enriched in LREE. Harzburgite adjacent to pyroxenite has been refertilized, containing phlogopite, less olivine, more orthopyroxene, and more garnet than distal harzburgite. The T-7 peridotite compositions are the result of variable degrees of partial melting in the spinel stability field, followed by cryptic metasomatism and modal metasomatism by transient basaltic melts in the garnet field. Trace elements, Sr and Nd isotopes, and occurrence of phlogopite reflect a subduction component in the metasomatising melts. Partial melting of the T-7 peridotite was a Proterozoic event, as indicated by Rhenium depletion model ages (TRD); the age of cryptic and modal metasomatism is unconstrained, but is thought to be related to Variscan subduction and amalgamation of the Bohemian Massif.

  12. A-type granites from the Pan-African orogenic belt in south-western Chad constrained using geochemistry, Sr-Nd isotopes and U-Pb geochronology

    NASA Astrophysics Data System (ADS)

    Isseini, Moussa; André-Mayer, Anne-Sylvie; Vanderhaeghe, Olivier; Barbey, Pierre; Deloule, Etienne

    2012-11-01

    The Zabili granitic pluton (SW Chad) exposed in the Mayo Kebbi massif is dominated by a coarse-grained hornblende biotite granite grading into a fine-grained biotite granite along its southern margin. Petrologic (micrographic intergrowth of quartz and alkali feldspars, granophyric microstructures, the presence of fluorite and bastnaesite as accessory minerals) and geochemical data (high silica, alkalis and Fe/Mg, depletions in CaO, MgO, TiO2; high Ga, Nb, Zr, Ga/Al, REE, depletions in Ba, Sr, Eu and compatible elements) indicate that this pluton consists of A-type granites crystallized from hot (apatite and zircon saturation temperatures ranging from 744 °C to 923 °C), extremely differentiated magmas. U-Pb zircon geochronology indicates that the magmas crystallized at 567 ± 10 Ma and reveals the presence of older Neoproterozoic xenocrystic zircons at 668 ± 5 Ma in both facies. Within the fine-grained biotite granite, discordant zircons with U-Pb and Pb-Pb ages ranging from Neoproterozoic to Archaean are also reported. The 668 ± 5 Ma old zircons are considered to derive from country-rocks while discordant zircons, characterized by angular shapes, internal fractures and inherited cores, are likely to represent multi-sources detrital crystals that have recorded at least one metamorphic event. Old pre-Neoproterozoic zircons are reported for the first time for rocks of the Mayo Kebbi massif and they attest to the contribution of an old basement (likely to be the Eastern Nigeria basement and/or the Congo craton) involved in a collisional event with a juvenile Neoproterozoic crust prior to the emplacement of the Zabili granitic pluton. Initial ɛNd values calculated for the Zabili pluton range from + 2.6 to + 7.0, the highest value recorded by one sample from the coarse-grained hornblende-biotite granite being close to the one of the depleted mantle at 570 Ma (ɛNd = + 7.4). Combining geochronology, Nd isotopes composition and geochemical modeling, leads us to

  13. Geochemistry and Sr-Nd isotopes of the subvolcanic sill complex and sandstone geochronology from María Magdalena island, Nayarit, Mexico

    NASA Astrophysics Data System (ADS)

    Villanueva, D.; Schaaf, P. E.; Hernandez, T.; Solis, G.; Weber, B.; Pompa, V.

    2013-12-01

    María Magdalena island is part of the Islas Marías archipielago, located at the mouth of the Gulf of California. Understanding the nature and origin of the archipelago is very important for reconstructing the paleoposition of Baja California Peninsula prior to the opening of the Gulf of California. We present the first geochemical, isotopic and geochronologic data from María Magdalena, a lithologically different island compared to the rest of the archipelago. María Magdalena island is located southeast of María Madre and northeast of María Cleofas islands and is composed by a sedimentary sequence of sandstones and minor shale, which is intruded by gabbroic sills. The sedimentary sequence dips approximately 20 degrees to the NW. The thickness of sills range from 1 to 3 meters with mineralogical variations of plagioclase +/- orthopyroxene +/- clinopyroxene +/- hornblende and some altered olivine crystals. Textures are mostly porphyritic with plagioclase crystals sizes up to 5 cm and olivines up to 5 mm. The gabbroic sills show SiO2 contents from 42.7 to 47.5 wt. %; TiO2 from 0.8 to 2 wt. %; Fe2O3t from 7.7 to 11.9 wt. %; MgO from 6.2 to 19.8 wt. % and of CaO from 6 to 11.6 wt. %, indicating mafic to ultramafic compositions. A multielement spider diagram as well as REE patterns show compositions very similar to N-MORB or even peridotites, which is confirmed by 87Sr/86Sr values from 0.70273 to 0.70497, and 143Nd/144Nd values from 0.513003 to 0.513100. U-Pb single zircon geochronology of the intruded sandstones display the following age distribution: eight crystals show ages from 80 to 86 Ma, three crystals have ages from 61 to 72 Ma, and three are around 21 Ma which constrains a maximum sandstone deposition age. Consequently, the sills must be younger than 21 Ma. There is not much lithological similarity with neighboring María Madre island to the NW (containing a metamorphic complex, granitoids and acid volcanic roks) and with María Cleofas island to the SE

  14. U-Pb zircon, geochemical and Sr-Nd-Hf-O isotopic constraints on age and origin of the ore-bearing intrusions from the Nurkazgan porphyry Cu-Au deposit in Kazakhstan

    NASA Astrophysics Data System (ADS)

    Shen, Ping; Pan, Hongdi; Seitmuratova, Eleonora; Jakupova, Sholpan

    2016-02-01

    Nurkazgan, located in northeastern Kazakhstan, is a super-large porphyry Cu-Au deposit with 3.9 Mt metal copper and 229 tonnage gold. We report in situ zircon U-Pb age and Hf-O isotope data, whole rock geochemical and Sr-Nd isotopic data for the ore-bearing intrusions from the Nurkazgan deposit. The ore-bearing intrusions include the granodiorite porphyry, quartz diorite porphyry, quartz diorite, and diorite. Secondary ion mass spectrometry (SIMS) zircon U-Pb dating indicates that the granodiorite porphyry and quartz diorite porphyry emplaced at 440 ± 3 Ma and 437 ± 3 Ma, respectively. All host rocks have low initial 87Sr/86Sr ratios (0.70338-0.70439), high whole-rock εNd(t) values (+5.9 to +6.3) and very high zircon εHf(t) values (+13.4 to +16.5), young whole-rock Nd and zircon Hf model ages, and consistent and slightly high zircon O values (+5.7 to +6.7), indicating that the ore-bearing magmas derived from the mantle without old continental crust involvement and without marked sediment contamination during magma emplacement. The granodiorite porphyry and quartz diorite porphyry are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) and depleted in high-field strength elements (HFSE), Eu, Ba, Nb, Sr, P and Ti. The diorite and quartz diorite have also LILE and LREE enrichment and HFSE, Nb and Ti depletion, but have not negative Eu, Ba, Sr, and P anomalies. These features suggest that the parental magma of the granodiorite porphyry and quartz diorite porphyry originated from melting of a lithospheric mantle and experienced fractional crystallization, whereas the diorite and quartz diorite has a relatively deeper lithospheric mantle source region and has not experienced strong fractional crystallization. Based on these, together with the coeval ophiolites in the area, we propose that a subduction of the Balkhash-Junggar oceanic plate took place during the Early Silurian and the ore-bearing intrusions and associated Nurkazgan

  15. H, O, Sr, Nd, and Pb isotope geochemistry of the Latir volcanic field and cogenetic intrusions, New Mexico, and relations between evolution of a continental magmatic center and modifications of the lithosphere

    USGS Publications Warehouse

    Johnson, C.M.; Lipman, P.W.; Czamanske, G.K.

    1990-01-01

    Over 200 H, O, Sr, Nd, and Pb isotope analyses, in addition to geologic and petrologic constraints, document the magmatic evolution of the 28.5-19 Ma Latir volcanic field and associated intrusive rocks, which includes multiple stages of crustal assimilation, magma mixing, protracted crystallization, and open- and closed-system evolution in the upper crust. In contrast to data from younger volcanic centers in northern New Mexico, relatively low and restricted primary ??18O values (+6.4 to +7.4) rule out assimilation of supracrustal rocks enriched in 18O. Initial 87Sr/86Sr ratios (0.705 to 0.708), ??18O values (-2 to-7), and 206Pb/204Pb ratios (17.5 to 18.4) of metaluminous precaldera volcanic rocks and postcaldera plutonic rocks suggest that most Latir rocks were generated by fractional crystallization of substantial volumes of mantle-derived basaltic magma that had near-chondritic Nd isotope ratios, accompanied by assimilation of crustal material in two main stages: 1) assimilation of non-radiogenic lower crust, followed by 2) assimilation of middle and upper crust by inter-mediate-composition magmas that had been contaminated during the first stage. Magmatic evolution in the upper crust peaked with eruption of the peralkaline Amalia Tuff (???26 Ma), which evolved from metaluminous parental magmas. A third stage of late, roofward assimilation of Proterozoic rocks in the Amalia Tuff magma is indicated by trends in initial 87Sr/86Sr and 206Pb/204Pb ratios from 0.7057 to 0.7098 and 19.5 to 18.8, respectively, toward the top of the pre-eruptive magma chamber. Highly evolved postcaldera plutons are generally fine grained and are zoned in initial 87Sr/86Sr and 206Pb/204Pb ratios, varying from 0.705 to 0.709 and 17.8 to 18.6, respectively. In contrast, the coarser-grained Cabresto Lake (???25 Ma) and Rio Hondo (???21 Ma) plutons have relatively homogeneous initial 87Sr/86Sr and 206Pb/204Pb ratios of approximately 0.7053 and 17.94 and 17.55, respectively. ??18O values for

  16. Sr-Nd-Hf isotopes of the intrusive rocks in the Cretaceous Xigaze ophiolite, southern Tibet: Constraints on its formation setting

    NASA Astrophysics Data System (ADS)

    Zhang, Liang-Liang; Liu, Chuan-Zhou; Wu, Fu-Yuan; Zhang, Chang; Ji, Wei-Qiang; Wang, Jian-Gang

    2016-08-01

    The Cretaceous Xigaze ophiolite is best exposed at the central part of the Yarlung-Zangbo Suture Zone, Tibet Plateau. It consists of a thick section of mantle peridotites, but a relatively thin mafic sequence. This study presents geochronological and geochemical data for intrusive dykes (both mafic and felsic) and basalts to revisit the formation setting of the Xigaze ophiolite. The rodingites are characterized by high CaO and low Na2O contents relative to mafic dykes and show big variations in trace element compositions. Both gabbros and diabases have similar geochemical compositions, with MgO contents of 6.42-11.48 wt% and Mg# of 0.56-0.71. They display REE patterns similar to N-MORB and are variably enriched in large ion lithophile elements. Basalts have fractionated compositions and display LREE-depleted patterns very similar to N-MORB. They do not show obvious enrichment in LILE and depletion in high-field-strength elements, but a negative Nb anomaly is present. The studied plagiogranites have compositions of trondhjemite to tonalite, with high Na2O and low K2O contents. They have low TiO2 contents less than 1 wt%, consistent with melts formed by anatexis of gabbros rather than by differentiation of basalts. Zircons from seven samples, including three rodingites, three plagiogranites, and one gabbro, have been dated and yielded U-Pb ages of 124.6 ~ 130.5 Ma, indicating the Xigaze ophiolite was formed during the Early Cretaceous. They have mantle-like δ18O values of + 4.92 ~ + 5.26‰ and very positive εHf(t) values of + 16 ~ + 13.3. Ages of the rodingites and less altered gabbros indicate that serpentinization was occurred at ~ 125 Ma. Occurrence of both gabbroic and diabase dykes within the serpentinites suggests that the mantle lithosphere of the Xigaze ophiolite was rapidly exhumed. Both mafic and felsic dykes have slightly more radiogenic 87Sr/86Sr ratios relative to MORB, but depleted Hf-Nd isotpe compositions. They have a limited range of ε

  17. Petrogenesis of subvolcanic rocks from the Khunik prospecting area, south of Birjand, Iran: Geochemical, Sr-Nd isotopic and U-Pb zircon constraints

    NASA Astrophysics Data System (ADS)

    Samiee, Somayeh; Karimpour, Mohammad Hassan; Ghaderi, Majid; Haidarian Shahri, Mohammad Reza; Klöetzli, Urs; Santos, José Francisco

    2016-01-01

    The Khunik prospecting area is located 106 km south of Birjand in eastern Iran, and is considered as an epithermal gold prospecting area. The mineralization is related to subvolcanic rocks. There are several outcrops of subvolcanic intrusions in the area which intruded into Paleocene-Eocene volcanic rocks (andesite, trachy-andesite and pyroclastic rocks). Petrographic studies indicate that subvolcanic rocks consist mainly of diorite, monzonite, quartz-monzonite, monzodiorite and quartz-monzodiorite. Mineralogically, these rocks contain plagioclase, K-feldspar, amphibole, pyroxene, biotite and quartz. Geochemically, they have features typical of high-K calk-alkaline to shoshonitic and are metaluminous, and also belong to magnetite granitoid series (I-type). Primitive mantle normalized trace element spider diagrams display enrichment in LILE, such as Rb, Ba, and Cs, compared to HFSE. Chondrite-normalized REE plots show moderately LREE enriched patterns (7.45 < LaN/YbN < 10.54), and no significant Eu anomalies. Tectonic discrimination diagrams also show affinities with modern convergent margin magmas, suggesting that magmas of Khunik area formed in volcanic arc setting related to subduction of the oceanic crust under the Lut Block plate. The initial 87Sr/86Sr ratios (0.704196-0.704772) and εNdi values (+1.3 to +3.3) are compatible with an origin of the parental melts in a supra-subduction mantle wedge. Zircon U-Pb dating by LA-ICP-MS indicates the age of 38 ± 1 Ma (late Eocene) for subvolcanic units that are related to mineralization. A biotite granodiorite porphyry is the testimony of the youngest magmatic activity in the area, with an age of 31 ± 1 Ma (early Oligocene). The represented dates are interpreted as magmatic crystallization ages of subvolcanic intrusions.

  18. Tectonic significance of the Dongqiao ophiolite in the north-central Tibetan plateau: Evidence from zircon dating, petrological, geochemical and Sr-Nd-Hf isotopic characterization

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Zhai, Qing-guo; Wang, Jun; Bao, Pei-sheng; Qiangba, Zhaxi; Tang, Suo-han; Tang, Yue

    2016-02-01

    The Dongqiao ophiolite occurs in the central segment of the Bangong-Nujiang suture zone, in north-central Tibet, China. It is still debated on the tectonic setting of the Dongqiao ophiolite despite after more than 30 years' studies. The Dongqiao ophiolite has a complete section of a typical ophiolite, composed of harzburgite, dunite, layered and isotropic gabbros, pillow and massive basalts, as well as radiolarian chert. Whole-rock geochemical analyses show that harzburgite displays a broad U-shaped REE pattern and has a fore-arc affinity, whereas basalts show affinities of E-MORB, OIB and IAB. The basalts were probably formed in different tectonic settings, that is, mid-ocean ridge, oceanic island and island arc. The gabbros and basalts are characterized by positive εNd(t) (+1.6 to +6.7) and εHf(t) (+8.1 to +13.9) values. Zircon U-Pb dating yielded ages of 188 ± 1 Ma for the layered gabbro and 181 ± 1 Ma for the amphibole gabbro. The new ages and the published age data of the Dingqing and Dong Co ophiolites led us to conclude that the Bangong-Nujiang Ocean existed from the Late Triassic to Early Cretaceous. The new geochemical data also suggested that the Dongqiao ophiolite was a typical SSZ-type ophiolite formed in an initial fore-arc oceanic basin. Fore-arc ophiolites are probably widely distributed along the Bangong-Nujiang suture zone. If so, the Tethys Ocean of the Bangong-Nujiang area probably existed as a fore-arc oceanic basin during the Late Triassic to Early Jurassic.

  19. Late Cretaceous back-arc extension and arc system evolution in the Gangdese area, southern Tibet: Geochronological, petrological, and Sr-Nd-Hf-O isotopic evidence from Dagze diabases

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Wang, Qiang; Wyman, Derek A.; Jiang, Zi-Qi; Wu, Fu-Yuan; Li, Xian-Hua; Yang, Jin-Hui; Gou, Guo-Ning; Guo, Hai-Feng

    2015-09-01

    Back-arc extension and asthenosphere upwelling associated with oceanic lithospheric subduction affect the structure and thermal regime of the arc lithosphere, which often triggers widespread extension-related mafic magmatism. Although it is commonly accepted that the Neo-Tethyan oceanic lithosphere subducted beneath the southern Lhasa block, resulting in the well-known Late Mesozoic Gangdese magmatic arc, the possible role of contemporary back-arc extension and asthenosphere upwelling has been disputed due to a lack of evidence for extension-related mafic magmatism. Here, we report detailed petrological, geochronological, geochemical, and Sr-Nd-Hf-O isotopic data for the Dagze diabases located in the north of the Gangdese district, southern Lhasa block. The zircon U-Pb analyses indicate that they were generated in the Late Cretaceous (ca. 92 Ma) instead of the Eocene (42-38 Ma) as previously believed. These mafic rocks are characterized by variable MgO (4.0-12.2 wt %) and Mg# (42 to 71) values combined with flat to slightly enriched ([La/Yb]N = 1.87-5.23) light rare earth elements (REEs) and relative flat heavy REEs ([Gd/Yb]N = 1.36-1.87) with negative Ta, Nb, and Ti anomalies (e.g., [Nb/La]PM = 0.16-0.51). They also have slightly variable ɛNd(t) (-1.25 to +4.71) and low initial 87Sr/86Sr (0.7045-0.7058) values with strong positive igneous zircon ɛHf(t) (+8.0 to +12.1) and low δ18O (5.31-6.12‰) values. The estimated primary melt compositions are similar to peridotite-derived experimental melts. Given their high melting temperature (1332 to 1372°C) and hybrid geochemical characteristics, we propose that the Dagze mafic magmas likely represent mixtures of asthenospheric and enriched lithospheric mantle-derived melts that underwent minor crustal assimilation and fractional crystallization of clinopyroxene. Taking into account the spatial and temporal distribution of Mesozoic mafic-felsic magmatic rocks and regional paleomagnetic and basin data, we suggest that

  20. Sulfide mineralization associated with arc magmatism in the Qilian Block, western China: zircon U-Pb age and Sr-Nd-Os-S isotope constraints from the Yulonggou and Yaqu gabbroic intrusions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao-Wei; Li, Wen-Yuan; Gao, Yong-Bao; Li, Chusi; Ripley, Edward M.; Kamo, Sandra

    2014-02-01

    The sulfide-bearing Yulonggou and Yaqu mafic intrusions are located in the southern margin of the Qilian Block, Qinghai Province, western China. They are small dike-like bodies mainly composed of gabbros and diorites. Disseminated sulfides (pyrrhotite, pentlandite, and chalcopyrite) are present as concordant lenses within the intrusions. Precise CA-ID-TIMS zircon U-Pb dating yields the crystallization ages of 443.39 ± 0.42 and 440.74 ± 0.33 Ma for the Yulonggou and Yaqu intrusions, respectively. Whole rock samples from both intrusions show light rare earth element (REE) enrichments relative to heavy REE and pronounced negative Nb-Ta anomalies relative to Th and La, which are consistent with the products of arc basaltic magmatism. The Yulonggou intrusion has negative ɛ Nd values from -5.7 to -7.7 and elevated (87Sr/86Sr) i ratios from 0.711 to 0.714. In contrast, the Yaqu intrusion has higher ɛ Nd values from -4.1 to +8.4 and lower (87Sr/86Sr) i ratios from 0.705 to 0.710. The δ34S values of sulfide separates from the Yulonggou and Yaqu deposits vary from 0.8 to 2.4 ‰ and from 2 to 4.3 ‰, respectively. The γ Os values of sulfide separates from the Yulonggou and Yaqu deposits vary between 80 and 123 and between 963 and 1,191, respectively. Higher γ Os values coupled with higher δ34S values for the Yaqu deposit relative to the Yulonggou deposit indicate that external sulfur played a bigger role in sulfide mineralization in the Yaqu intrusion than in the Yulonggou intrusion. Mixing calculations using Sr-Nd isotope data show that contamination with siliceous crustal materials is more pronounced in the Yulonggou intrusion (up to 20 wt%) than in the Yaqu intrusion (<15 wt%). The distribution of sulfides in both intrusions is consistent with multiple emplacements of sulfide-saturated magmas from depth. The Yulonggou and Yaqu sulfide deposits are not economically valuable under current market condition due to small sizes and low Ni grades, which can be explained

  1. Petrogenesis of syntectonic granites emplaced at the transition from thrusting to transcurrent tectonics in post-collisional setting: Whole-rock and Sr-Nd-Pb isotope geochemistry in the Neoproterozoic Quatro Ilhas and Mariscal Granites, Southern Brazil

    NASA Astrophysics Data System (ADS)

    Florisbal, Luana Moreira; Bitencourt, Maria de Fátima; Janasi, Valdecir de Assis; Nardi, Lauro Valentim Stoll; Heaman, Larry M.

    2012-11-01

    The Neoproterozoic post-collisional period in southern Brazil (650-580 Ma) is characterized by substantial volumes of magma emplaced along the active shear zones that compose the Southern Brazilian Shear Belt. The early-phase syntectonic magmatism (630-610 Ma) is represented by the porphyritic, high-K, metaluminous to peraluminous Quatro Ilhas Granitoids and the younger heterogranular, slightly peraluminous Mariscal Granite. Quatro Ilhas Granitoids include three main petrographic varieties (muscovite-biotite granodiorite — mbg; biotite monzogranite — bmz; and leucogranite — lcg) that, although sharing some significant geochemical characteristics, are not strictly comagmatic, as shown by chemical and Sr-Nd-Pb isotope data. The most primitive muscovite-biotite granodiorite was produced by contamination of more mafic melts (possibly with some mantle component) with peraluminous crustal melts; the biotite monzogranite, although more felsic, has higher Ca, MgO, TiO2 and Ba, and lower K2O, FeOt, Sr and Rb contents, possibly reflecting some mixing with coeval mafic magmas of tholeiitic affinity; the leucogranite may be derived from pure crustal melts. The Mariscal Granite is formed by two main granite types which occur intimately associated in the same pluton, one with higher K (5-6.5 wt.% K2O) high Rb and lower CaO, Na2O, Ba and Zr as compared to the other (3-5 wt.% of K2O). The two Mariscal Granite varieties have compositional correspondence with fine-grained granites (fgg) that occur as tabular bodies which intruded the Quatro Ilhas Granoitoids before they were fully crystallized, and are inferred to correspond to the Mariscal Granite feeders, an interpretation that is reinforced by similar U-Pb zircon crystallization ages. The initial evolution of the post-collisional magmatism, marked by the emplacement of the Quatro Ilhas Granitoids varieties, activated sources that produced mantle and crustal magmas whose emplacement was controlled both by flat-lying and

  2. Melt evolution beneath a rifted craton edge: 40Ar/39Ar geochronology and Sr-Nd-Hf-Pb isotope systematics of primitive alkaline basalts and lamprophyres from the SW Baltic Shield

    NASA Astrophysics Data System (ADS)

    Tappe, Sebastian; Smart, Katie A.; Stracke, Andreas; Romer, Rolf L.; Prelević, Dejan; van den Bogaard, Paul

    2016-01-01

    A new high-precision 40Ar/39Ar anorthoclase feldspar age of 176.7 ± 0.5 Ma (2-sigma) reveals that small-volume alkaline basaltic magmatism occurred at the rifted SW margin of the Baltic Shield in Scania (southern Sweden), at a time of global plate reorganization associated with the inception of Pangea supercontinent break-up. Our combined elemental and Sr-Nd-Hf-Pb isotope dataset for representative basanite and nephelinite samples (>8 wt.% MgO) from 16 subvolcanic necks of the 30 by 40 km large Jurassic volcanic field suggests magma derivation from a moderately depleted mantle source (87Sr/86Sri = 0.7034-0.7048; εNdi = +4.4 to +5.2; εHfi = +4.7 to +8.1; 206Pb/204Pbi = 18.8-19.5). The mafic alkaline melts segregated from mixed peridotite-pyroxenite mantle with a potential temperature of ∼1400 °C at 2.7-4.2 GPa (∼90-120 km depths), which places ultimate melt generation within the convecting upper mantle, provided that the lithosphere-asthenosphere boundary beneath the southern Baltic Shield margin was at ⩽100 km depth during Mesozoic-Cenozoic rifting. Isotopic shifts and incompatible element enrichment relative to Depleted Mantle reflect involvement of at least 20% recycled oceanic lithosphere component (i.e., pyroxenite) with some minor continent-derived sediment during partial melting of well-stirred convecting upper mantle peridotite. Although pargasitic amphibole-rich metasomatized lithospheric mantle is excluded as the main source of the Jurassic magmas from Scania, hydrous ultramafic veins (i.e., hornblendite) may have caused subtle modifications to the compositions of passing sublithospheric melts. For example, modeling suggests that the more radiogenic Hf (εHfi = +6.3 to +8.1) and Pb (206Pb/204Pbi = 18.9-19.5) isotopic compositions of the more sodic and H2O-rich nephelinites, compared with relatively homogenous basanites (εHfi = +4.7 to +6.1; 206Pb/204Pbi = 18.8-18.9), originate from minor interactions between rising asthenospheric melts and

  3. Zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopes of the Nuri intrusive rocks in the Gangdese area, southern Tibet: Constraints on timing, petrogenesis, and tectonic transformation

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Qin, Ke-Zhang; Li, Guang-Ming; Li, Jin-Xiang; Xiao, Bo; Zhao, Jun-Xing; Fan, Xin

    2015-01-01

    Abundant magmatic rocks of various ages are exposed in Gangdese, southern Tibet. These rocks play an important role in understanding the tectonic transformation from the subduction of Neo-Tethyan oceanic crust to the collision of the Indian and Asian continents. Based on zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopic data of the Late Cretaceous to early Oligocene (~ 96-30 Ma) intrusive rocks in the Nuri Cu-W-Mo deposit, we discuss the Late Cretaceous to early Oligocene tectonic transformation of the region and the origin of Oligocene Cu-W-Mo mineralization in southern Gangdese. The Nuri intrusive rocks represent three magmatic episodes: 96-91, 56-52, and 33-30 Ma. The 96-91 and 56-52 Ma rocks have relatively low (87Sr/86Sr)i (0.7041 to 0.7060), and high εNd(t) (+ 3.1 to + 3.5) and εHf(t) values (+ 3.7 to + 15); the 33-30 Ma rocks have relatively high (87Sr/86Sr)i (0.7061 to 0.7063) and Pb isotopes, and low εNd(t) (- 3.8 to - 1.8) and εHf(t) values (+ 0.6 to + 10.1). The three stages of intrusive rocks have geochemical characteristics that are similar to those of coeval rocks in Gangdese. The 96-91 and 33-30 Ma rocks are adakitic, whereas the 56-52 Ma rocks have characteristics of arc calc-alkaline magmatic rocks. The 96-91 Ma rocks were produced by the partial melting of Neo-Tethyan basaltic oceanic crust and minor sediments, whereas the 56-52 Ma rocks were generated by the partial melting of juvenile crust and the 33-30 Ma rocks were formed by the melting of Indian plate lower crust contaminated with overlying mantle materials. On the basis of the regional tectonic and magmatic characteristics, we suggest that Neo-Tethyan oceanic slab subduction and slab roll-back occurred from ~ 100 to 65 Ma, collision between the Indian and Asian continents occurred at 65 to 40 Ma, Neo-Tethyan oceanic slab break-off took place at ~ 50 Ma, and the Indian continent subducted northwards beneath the Asian continent at ~ 30 Ma. From the Late Cretaceous (96-91 Ma) to

  4. Age of nephrite-bearing dikes of the Uzunkyr Belt (South Urals): Local U-Pb isotope analysis of zircon and Sr-Nd isotope data of rock-forming minerals

    NASA Astrophysics Data System (ADS)

    Arkhireev, I. E.; Makagonov, E. P.; Belyatskii, B. V.; Maslennikov, V. V.

    2012-01-01

    Through local U-Pb isotope analysis of zircon and Sir-Need data on rock-forming minerals, the age of nephrite-bearing monzonite-diorite dikes of the Uzunkyr Belt has been determined. The derived datings coincide with known geological events that took place in the Phanerozoic on the territory of the South Urals. Xenogenic zircons prove the participation of the Upper Ordovician units in the tectonic structure of the studied area. Devonian zircons are associated with assimilation of subvolcanic rocks which are middle and basic in composition and whose formation time correlates with the appearance of the subduction zone with the Magnitogorsk island arc above it. Early Carboniferous datings indicate the relationship between dike formation and formation of the continental arc-shaped structure to which the Syrostan massif (monzodiorite-granite formation) belongs. The age range of the Uzunkyr nephrite-bearing dikes coincides with that of intrusives (350-336 Ma) of the Magnitogorsk Belt, where formation of gabbro series was also changed by formation of subalkali and alkali igneous rocks. According to the analogous data on zircon datings from metamorphic rocks of the Il'menogorskii Complex, the given territory later evolved as a whole.

  5. Petrogenesis of metaluminous A-type granitoids in the Tengchong-Lianghe tin belt of southwestern China: Evidences from zircon U-Pb ages and Hf-O isotopes, and whole-rock Sr-Nd isotopes

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Cui; Hu, Rui-zhong; Bi, Xian-Wu; Zhong, Hong; Lan, Jiang-Bo; Zhao, Cheng-Hai; Zhu, Jing-Jing

    2015-01-01

    The Tengchong-Lianghe tin belt is the most importantpart of the tin metallogenic belt in southwest China's Sanjiang Metallogenic province. In this district, two A-type granite plutons that are spatially associated with the tin deposits have recently been discovered. These granitoids are dominated by biotite granites with weakly peraluminous to metaluminous compositions, high SiO2 contents (73.3-76.2 wt.%), and high alkali contents (K2O + Na2O = 8.3-9.17 wt.%). Trace element spider diagrams show that these granitoids are also clearly enriched with the large-ion lithophile elements Rb, Th, U, and K, but are markedly depleted in Ba and Sr. They are significantly depleted in the high field-strength elements Nb and Ti, but are enriched with Zr and Hf. These rocks have relatively high zircon saturation temperatures (774-833 °C), high Zr + Nb + Ce + Y contents (272-416 ppm), and 10,000 × Ga/Al ratios (almost > 2.7) that are typical of A-type granites. They also have high total rare earth element (REE) contents (174-404 ppm) and relatively flat chondrite-normalized REE patterns with significantly negative Eu anomalies. LA-ICP-MS zircon U-Pb dating results indicate that the emplacement of these two granite plutons occurred during the early Tertiary (52.7 ± 0.3-53.0 ± 0.4 Ma) and the Late Cretaceous (73.3 ± 0.5-73.3 ± 0.5 Ma) periods, respectively. Isotopic compositions show that the granitoids have highly variable (87Sr/86Sr)i ratios (0.7182-0.7457), relatively constant low εNd(t) values (- 11.2 to - 12.4), and ancient Nd and Hf model ages (1.56-1.88 Ga), suggesting that they were derived from the partial melting of the Paleoproterozoic continental crust. Their zircon δ18O values (6.6-8.5‰) and εHf values (from - 8.6 to - 11.3) also suggest that these granitoids mainly originated from the middle-lower continental crust consisting of mafic and metasedimentary rocks. Such geochemical characteristics indicate that these two A-type granite plutons were generated by

  6. Rapid Environmental Fluctuations Recorded over the Last Glacial/Interglacial Cycle in the Sediments from Borehole PRGL1-4 (Gulf of Lions; Western Mediterranean) using Radiogenic Isotopes (Sr & Nd)

    NASA Astrophysics Data System (ADS)

    Nizou, J.

    2015-12-01

    The study of sediments deposited and preserved in oceanic basins unable us to examine how terrigenous sediment supply varied through time in relation to paleoenvironmental and climatic changes on land. The geochemical and isotopic compositions of marine sediment are used to unravel its provenance, and provide information about its formation. Providing that the paleoclimatic frame is known, such data give an insight into the rock-source location and allow us to decipher between genetic processes of mechanical erosion and chemical alteration. Borehole PRGL1-4 (European project PROMESS), located in the Gulf of Lions (W Mediterranean) at 300 mwd, was investigated geochemically at high-temporal resolution over the last glacial/interglacial cycle (i.e. 130 ka) to study sediment-source variations during rapid climate changes. Besides, sediments originating from the Rhône's and the Pyreneo-Languedocian's catchment areas have been analyzed to measure the isotopic composition of five source end-members that are the Alps, the Higher Rhône valley, the Lower Rhône valley, the Languedoc and the Pyrenees. Epsilon Nd and 87Sr/86Sr were measured on 60 samples encompassing 4 marine isotopic stages with an emphasis on Heinrich events. The epsilon Nd values of PRGL1-4 lean towards the Lower Rhône valley unradiogenic end-member during cold stadial intervals, and towards the Alpine radiogenic end-member during warm interstadials. The presence of an ice cap over the crystalline Alpine watershed during cold phases could prevent the sediments originating from this region from reaching the Gulf of Lions. The same pattern is observed during the time of Heinrich events. An influence of the sea level variations on the sedimentation at the borehole site during the Heinrich events is unlikely since they are only 10 to 15 m in amplitude. Furthermore, a major isotopic shift in epsilon Nd mean values is displayed around 40 ka that coincides with the connection of the Durance to the Rhône River

  7. In situ chemical and Sr-Nd-O isotopic compositions of apatite from the Tongshi intrusive complex in the southern part of the North China Craton: Implications for petrogenesis and metallogeny

    NASA Astrophysics Data System (ADS)

    Xu, Wen-Gang; Fan, Hong-Rui; Hu, Fang-Fang; Santosh, M.; Yang, Kui-Feng; Lan, Ting-Guang

    2015-06-01

    The Tongshi intrusive complex from the southeastern margin of the North China Craton is composed of syenite and monzonite, and was emplaced at ca. 180 Ma. Apatite from the syenite and monzonite were analyzed to better understand the petrogenesis of the complex and its mineralization potential. The cathodoluminescence images of some apatites from the monzonite exhibit core-rim texture, whereas the apatites from the syenite display uniform inner texture. The core and rim domains of the apatites exhibit distinct Sr isotopes and major-trace element compositions, whereas only little variation is displayed by the oxygen isotopes. The core portions of the apatites were inferred to be inherited from the protolith of the monzonite during remelting process. The calculated δ18O values of the syenite range from 3.5‰ to 4.1‰ with an average of 3.8‰ (SE = 0.21), which is significantly lower than that of the monzonite sample (with a range of 6.4-6.9‰, and mean at 6.7‰). In conjunction with the heterogeneity of Nd isotopic compositions (with normalized 143Nd/144Nd ratios varying from 0.51151 to 0.51236, and εNd (t = 180 Ma) values from -20.3 to -4.8) of the apatites from the syenite, it is proposed that the syenite melts may have been contaminated by crustal components which were earlier hydrothermally altered at high temperature. Based on element diffusion theory, we calculate the temperature of this crustal contamination to be higher than 637 °C, the closure temperature of Sm-Nd isotopic diffusion in apatite, and estimate that the duration of this process is probably shorter than 0.13 Ma. The oxygen fugacity of the syenite and monzonite calculated by apatite Mn content indicate that high oxidization state of the syenite magma can enhance the metallic mineralization potential. In contrast, the lower oxygen fugacity of the monzonite melt was unfavorable for metal enrichment, thus leading to insignificant mineralization. Our study recommends more focus for gold

  8. Asthenosphere-lithosphere interaction triggered by a slab window during ridge subduction: Trace element and Sr-Nd-Hf-Os isotopic evidence from Late Carboniferous tholeiites in the western Junggar area (NW China)

    NASA Astrophysics Data System (ADS)

    Tang, Gong-Jian; Wyman, Derek A.; Wang, Qiang; Li, Jie; Li, Zheng-Xiang; Zhao, Zhen-Hua; Sun, Wei-Dong

    2012-05-01

    Tholeiites occur in a variety of geological settings, e.g., mid-ocean ridge, back-arc basin, ocean island, island arc and intra-continent, and their geochemical and isotopic characteristics vary according to the corresponding geodynamic environments. Here we investigated the Hatu tholeiitic basalts and basaltic andesites of the western Junggar region, Central Asian Orogenic Belt (CAOB). LA-ICPMS zircon U-Pb analyses indicate that the Hatu tholeiites were generated in the Late Carboniferous (~ 315 Ma). All the studied rock samples are characterized by flat rare earth elements pattern on chondrite-normalized plot, and negligible Nb, Ta and Ti anomalies on mid-ocean-ridge basalt normalized plots. They are also characterized by moderate positive ɛNd(t) (+ 5.25 to + 5.94), ɛHf(t) (+ 13.24 to + 14.89), highly radiogenic Os isotope compositions (187Os/188Os315Ma = 0.1338-0.3547), and relatively low (87Sr/86Sr)i ratios (0.7044 to 0.7048). Taking into account their geological characteristics, the occurrence of nearby ophiolites and the types of contemporaneous magmatic rocks found in the western Junggar region, we propose that the Hatu basalts were generated by slab window-related processes following a spreading ridge subduction beneath the Keramay intra-oceanic island arc. During this process, deep and enriched asthenospheric mantle rose to the edge of the subducted oceanic lithosphere, its melts infiltrating the subducted oceanic lithosphere and reacting with peridotites. Therefore, the Hatu tholeiites are interpreted as a result of melting of a mixed mantle source consisting of subducted depleted oceanic lithosphere and a deep, enriched upwelling asthenospheric mantle. Incongruent dynamic melting modeling of trace element compositions indicates that the Hatu basalts could have been derived from large degrees of melting (~ 10%) of such a mixed mantle source. This newly recognized mechanism is a natural consequence of the diversity of contemporaneous potential mantle

  9. Petrology and Sr, Nd, and Pb isotope geochemistry of mid-ocean ridge basalt glasses from the 11°45'N to 15°00'N segment of the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Castillo, P. R.; Klein, E.; Bender, J.; Langmuir, C.; Shirey, S.; Batiza, R.; White, W.

    2000-11-01

    Basaltic glasses from the geophysically well-studied section of the East Pacific Rise (EPR) between 11°45'N to 15°00'N range from normal mid-ocean ridge basalts (MORB) to transitional MORB and their major element variations correlate with isotopic and trace element indices of enrichment. To first order, basalts enriched in Na8.0, incompatible elements, 87Sr/86Sr, and 206Pb/204Pb but low in Fe8.0 and 143Nd/144Nd are more prevalent along the shallow portions of the ridge axis. In detail, the samples can be divided into two chemical and geographical Groups: the southern bathymetric dome, extending from the 11°45'N overlapping spreading center to ~14°10'N, and the northern Group, extending from ~14°10'N to the Orozco transform. The boundary between these two Groups is apparent in a change in isotopic composition. Results indicate that there are three mantle source components that produce the compositional variability observed among samples from the 11°45'N to 15°00'N segment of the EPR: a depleted mantle component, a seamount-type enriched mantle component, and an Indian MORB-like mantle component. South of ~14°10'N, the geochemical variability is dominated by binary mixing between a depleted mantle component and an enriched component similar to near-ridge seamounts. North of ~14°10'N, the low 206Pb/204Pb, high 207Pb/204Pb Indian MORB-like component exerts a major influence on the geochemical variability of the axial lavas. Regional averages of major element composition (e.g., Na8.0 and Fe8.0) show relatively limited variability consistent with the restricted range in depth for this region and plot within the Pacific field of the previously defined global trends. Major element variations among individual samples, however, parallel the global array, and their correlation with indices of mantle enrichment supports the idea that the ``Pacific-type local trend'' results from small-scale heterogeneities in the mantle beneath the EPR. Our results also indicate that

  10. Geodynamic control on melt production in the central Azores : new insights from major and trace elements, Sr, Nd, Pb, Hf isotopic data and K/Ar ages on the islands of Terceira, Sao Jorge and Faial

    NASA Astrophysics Data System (ADS)

    Hildenbrand, A.; Weis, D. A.; Madureira, P.; Marques, F. O.

    2012-12-01

    A combined geochronological and geochemical study has been carried out on the volcanic islands of Terceira, São Jorge, and Faial (central Azores) to examine the relationships between mantle dynamics, melt production and regional deformation close to the triple junction between the American, the Eurasian and the Nubian lithospheric plates. The lavas analyzed span the last 1.3 Myr, and have been erupted during two main periods prior to 800 ka and after 750 ka, respectively. They range in composition from alkaline basalts/basanites to trachytes, and overall exhibit a strong enrichment in highly incompatible elements. The whole range of isotopic compositions here reported (87Sr/86Sr: 0.703508-0.703913; 143Nd/144Nd: 0.512882-0.513010; 206Pb/204Pb: 19.0840- 20.0932; 207Pb/204Pb: 15.5388-15.6409; 208Pb/204Pb: 38.7416-39.3921; 176Hf/177Hf: 0.282956-0.283111) suggests the involvement of three components: (1) a weakly radiogenic component reflecting the source of regional MORBs, (2) a main HIMU-type component represented in the three islands, and (3) an additional component in Faial recent lavas, which appears similar to the EM type end-member previously recognized on other Azores eruptive complexes. The geographical distribution of the enriched components and the synchronous construction of various islands at the regional scale rules out a single narrow active plume. They suggest in turn the presence of dispersed residual enriched mantle blobs, interpreted as remnants from a large heterogeneous plume probably responsible for edification of the Azores plateau several Myr ago. The lavas erupted in São Jorge and Faial prior to 800 ka have similar and homogeneous isotopic ratios, which partly overlap the compositional field of MORBs from the adjacent portion of the Mid-Atlantic Ridge (MAR). Their genesis can be explained by the regional development of N150 transtensive tectonic structures, which promoted significant decompression melting of the upper mantle, with correlative

  11. Single crystal U-Pb zircon age and Sr-Nd isotopic composition of impactites from the Bosumtwi impact structure, Ghana: Comparison with country rocks and Ivory Coast tektites.

    PubMed

    Ferrière, Ludovic; Koeberl, Christian; Thöni, Martin; Liang, Chen

    2010-08-01

    The 1.07 Myr old Bosumtwi impact structure (Ghana), excavated in 2.1-2.2 Gyr old supracrustal rocks of the Birimian Supergroup, was drilled in 2004. Here, we present single crystal U-Pb zircon ages from a suevite and two meta-graywacke samples recovered from the central uplift (drill core LB-08A), which yield an upper Concordia intercept age of ca. 2145 ± 82 Ma, in very good agreement with previous geochronological data for the West African Craton rocks in Ghana. Whole rock Rb-Sr and Sm-Nd isotope data of six suevites (five from inside the crater and one from outside the northern crater rim), three meta-graywacke, and two phyllite samples from core LB-08A are also presented, providing further insights into the timing of the metamorphism and a possibly related isotopic redistribution of the Bosumtwi crater rocks. Our Rb-Sr and Sm-Nd data show also that the suevites are mixtures of meta-greywacke and phyllite (and possibly a very low amount of granite). A comparison of our new isotopic data with literature data for the Ivory Coast tektites allows to better constrain the parent material of the Ivory Coast tektites (i.e., distal impactites), which is thought to consist of a mixture of metasedimentary rocks (and possibly granite), but with a higher proportion of phyllite (and shale) than the suevites (i.e., proximal impactites). When plotted in a Rb/Sr isochron diagram, the sample data points (n = 29, including literature data) scatter along a regression line, whose slope corresponds to an age of 1846 ± 160 Ma, with an initial Sr isotope ratio of 0.703 ± 0.002. However, due to the extensive alteration of some of the investigated samples and the lithological diversity of the source material, this age, which is in close agreement with a possible "metamorphic age" of ∼ 1.8-1.9 Ga tentatively derived from our U-Pb dating of zircons, is difficult to consider as a reliable metamorphic age. It may perhaps reflect a common ancient source whose Rb-Sr isotope

  12. Single crystal U-Pb zircon age and Sr-Nd isotopic composition of impactites from the Bosumtwi impact structure, Ghana: Comparison with country rocks and Ivory Coast tektites.

    PubMed

    Ferrière, Ludovic; Koeberl, Christian; Thöni, Martin; Liang, Chen

    2010-08-01

    The 1.07 Myr old Bosumtwi impact structure (Ghana), excavated in 2.1-2.2 Gyr old supracrustal rocks of the Birimian Supergroup, was drilled in 2004. Here, we present single crystal U-Pb zircon ages from a suevite and two meta-graywacke samples recovered from the central uplift (drill core LB-08A), which yield an upper Concordia intercept age of ca. 2145 ± 82 Ma, in very good agreement with previous geochronological data for the West African Craton rocks in Ghana. Whole rock Rb-Sr and Sm-Nd isotope data of six suevites (five from inside the crater and one from outside the northern crater rim), three meta-graywacke, and two phyllite samples from core LB-08A are also presented, providing further insights into the timing of the metamorphism and a possibly related isotopic redistribution of the Bosumtwi crater rocks. Our Rb-Sr and Sm-Nd data show also that the suevites are mixtures of meta-greywacke and phyllite (and possibly a very low amount of granite). A comparison of our new isotopic data with literature data for the Ivory Coast tektites allows to better constrain the parent material of the Ivory Coast tektites (i.e., distal impactites), which is thought to consist of a mixture of metasedimentary rocks (and possibly granite), but with a higher proportion of phyllite (and shale) than the suevites (i.e., proximal impactites). When plotted in a Rb/Sr isochron diagram, the sample data points (n = 29, including literature data) scatter along a regression line, whose slope corresponds to an age of 1846 ± 160 Ma, with an initial Sr isotope ratio of 0.703 ± 0.002. However, due to the extensive alteration of some of the investigated samples and the lithological diversity of the source material, this age, which is in close agreement with a possible "metamorphic age" of ∼ 1.8-1.9 Ga tentatively derived from our U-Pb dating of zircons, is difficult to consider as a reliable metamorphic age. It may perhaps reflect a common ancient source whose Rb-Sr isotope

  13. Zircon U-Pb and molybdenite Re-Os geochronology and Sr-Nd-Pb-Hf isotopic constraints on the genesis of the Xuejiping porphyry copper deposit in Zhongdian, Northwest Yunnan, China

    NASA Astrophysics Data System (ADS)

    Leng, Cheng-Biao; Zhang, Xing-Chun; Hu, Rui-Zhong; Wang, Shou-Xu; Zhong, Hong; Wang, Wai-Quan; Bi, Xian-Wu

    2012-10-01

    The Xuejiping porphyry copper deposit is located in northwestern Yunnan Province, China. Tectonically, it lies in the southern part of the Triassic Yidun island arc. The copper mineralization is mainly hosted in quartz-dioritic and quartz-monzonitic porphyries which intruded into clastic-volcanic rocks of the Late Triassic Tumugou Formation. There are several alteration zones including potassic, strong silicific and phyllic, argillic, and propylitic alteration zones from inner to outer of the mineralized porphyry bodies. The ages of ore-bearing quartz-monzonitic porphyry and its host andesite are obtained by using the zircon SIMS U-Pb dating method, with results of 218.3 ± 1.6 Ma (MSWD = 0.31, N = 15) and 218.5 ± 1.6 Ma (MSWD = 0.91, N = 16), respectively. Meanwhile, the molybdenite Re-Os dating yields a Re-Os isochronal age of 221.4 ± 2.3 Ma (MSWD = 0.54, N = 5) and a weighted mean age of 219.9 ± 0.7 Ma (MSWD = 0.88). They are quite in accordance with the zircon U-Pb ages within errors. Furthermore, all of them are contemporary with the timing of the Garzê-Litang oceanic crust subduction in the Yidun arc. Therefore, the Xuejiping deposit could be formed in a continental margin setting. There are negative ɛNd(t) values ranging from -3.8 to -2.1 and relatively high initial 87Sr/86Sr ratios from 0.7051 to 0.7059 for the Xuejiping porphyries and host andesites. The (206Pb/204Pb)t, (207Pb/204Pb)t and (208Pb/204Pb)t values of the Xuejiping porphyries and host andesites vary from 17.899 to 18.654, from 15.529 to 15.626, and from 37.864 to 38.52, respectively, indicative of high radiogenic Pb isotopic features. In situ Hf isotopic analyses on zircons by using LA-MC-ICP-MS exhibit that there are quite uniform and slightly positive ɛHf(t) values ranging from -0.2 to +3.2 (mostly between 0 and +2), corresponding to relatively young single-stage Hf model ages from 735 Ma to 871 Ma. These isotopic features suggest that the primary magmas of the Xuejiping porphyries and

  14. Petrogenesis of the Yaochong granite and Mo deposit, Western Dabie orogen, eastern-central China: Constraints from zircon U-Pb and molybdenite Re-Os ages, whole-rock geochemistry and Sr-Nd-Pb-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Xu, Zhaowen; Qiu, Wenhong; Li, Chao; Yu, Yang; Wang, Hao; Su, Yang

    2015-05-01

    The Dabie orogen is among the most famous continent-continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U-Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re-Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87Sr/86Sr ratios of 0.7087-0.7096, and Pb isotopic ratios of (206Pb/204Pb)i = 16.599-16.704, (207Pb/204Pb)i = 15.170-15.618 and (208Pb/204Pb)i = 36.376-38.248. The granite has εNd(t) of -18.0 to -16.3 and εHf(t) values of -26.5 to -20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8-74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region.

  15. Petrology, 40Ar/39Ar age, Sr-Nd isotope systematics, and geodynamic significance of an ultrapotassic (lamproitic) dyke with affinities to kamafugite from the easternmost margin of the Bastar Craton, India

    NASA Astrophysics Data System (ADS)

    Rao, N. V. Chalapathi; Atiullah; Burgess, R.; Nanda, Purnendu; Choudhary, A. K.; Sahoo, Samarendra; Lehmann, B.; Chahong, Ngazipmi

    2016-04-01

    We report the mineralogy, bulk-rock geochemistry, 40Ar/39Ar (whole-rock) age and radiogenic (Sr and Nd) isotope composition of an ultrapotassic dyke from Sakri (Nuapada lamproite field) located at the tectonic contact between the easternmost margin of the Bastar craton and Eastern Ghats Mobile Belt, India. The Sakri dyke has a mineralogy which strongly resembles a lamproite sensu stricto (viz.,Ti-rich phlogopite, Na-poor diopside, Fe-rich sanidine, ulvospinel trend and Sr-rich apatite). However, its bulk-rock major element geochemical characteristics (viz., extreme silica-undersaturated nature) resemble sensu lato kamafugite from Toro Ankole, Uganda, East African Rift, and Alto Paranaiba Province, Brazil. The Sakri dyke also displays certain compositional peculiarities (viz., high degree of evolution of mica composition from phlogopite to biotite, elevated titanium and aluminum in clinopyroxene and significantly lower bulk Mg#) when compared to the ultrapotassic rocks from various Indian cratons. 40Ar/39Ar dating gave a plateau age of 1045 ± 9 Ma which is broadly similar to that of other Mesoproterozoic (i) lamproites from the Bastar and Bundelkhand cratons, and (ii) kimberlites from the Eastern Dharwar craton. Initial bulk-rock Sr (0.705865-0.709024) and Nd (0.511063-0.511154) isotopic ratios reveal involvement of an `enriched' source region with long-term incompatible element enrichment and a depleted mantle (TDM) Nd model age of 2.56 Ga straddling the Archaean-Proterozoic chronostratigraphic boundary. The bulk-rock incompatible trace element ratios (Ta/Yb, Th/Yb, Rb/Ba and Ce/Y) of the Sakri ultrapotassic dyke negate any significant influence of crustal contamination. Small-degree melting (1 to 1.5 %) of a mixed garnet-facies and spinel-facies phlogopite lherzolite can account for its observed REE concentrations. Whereas the emplacement of the Sakri ultrapotassic dyke is related to the amalgamation of the supercontinent of Rodinia, its overlapping geochemical

  16. Influence of bacteria on lanthanide and actinide transfer from specific soil components (humus, soil minerals and vitrified municipal solid waste incinerator bottom ash) to corn plants: Sr-Nd isotope evidence.

    PubMed

    Aouad, Georges; Stille, Peter; Crovisier, Jean-Louis; Geoffroy, Valérie A; Meyer, Jean-Marie; Lahd-Geagea, Majdi

    2006-11-01

    Experiments have been performed to test the stability of vitrified municipal solid waste (MSW) incinerator bottom ash under the presence of bacteria (Pseudomonas aeruginosa) and plants (corn). The substratum used for the plant growth was a humus-rich soil mixed with vitrified waste. For the first time, information on the stability of waste glasses in the presence of bacteria and plants is given. Results show that inoculated plant samples contained always about two times higher lanthanide and actinide element concentrations. Bacteria support the element transfer since plants growing in inoculated environment developed a smaller root system but have higher trace element concentrations. Compared with the substratum, plants are light rare earth element (LREE) enriched. The vitrified bottom ash has to some extent been corroded by bacteria and plant activities as indicated by the presence of Nd (REE) and Sr from the vitrified waste in the plants. (87)Sr/(86)Sr and (143)Nd/(144)Nd isotope ratios of plants and soil components allow the identification of the corroded soil components and confirm that bacteria accelerate the assimilation of elements from the vitrified bottom ash. These findings are of importance for landfill disposal scenarios, and similar experiments should be performed in order to better constrain the processes of microbially mediated alteration of the MSW glasses in the biosphere.

  17. Geochemical and Sr-Nd-Pb isotope constraints on the petrogenesis of the K-rich Pedra Branca Syenite: Implications for the Neoproterozoic post-collisional magmatism in SE Brazil

    NASA Astrophysics Data System (ADS)

    Carvalho, Bruna Borges; Janasi, Valdecir de Assis; Henrique-Pinto, Renato

    2014-09-01

    The Pedra Branca Syenite is a 610 Ma post-collisional pluton intrusive in the Socorro-Guaxupé Nappe, an allochthonous terrain emplaced at the SW border of the São Francisco craton, Brazil. The pluton is largely dominated by laminated syenites with colour index 20-25 displayed in a zoned structure, with a first unit of marginally peralkaline silica-saturated syenites exposed at its E and N border intruded by silica-oversaturated metaluminous syenites making up its core. Mafic to ultramafic coarse-grained enclaves and lenses are frequent in the laminated units, and must correspond to disrupted cumulate layers. Fine-grained enclaves are rare, and vary from microsyenites, which seem to be products of new magma pulses frozen within mushy portions of the magma chamber, to monzonites and diorites, which reflect the existence of contemporaneous “basalt” (plagioclase-bearing) magmas that interacted with the syenitic magmas at greater depths and were carried up during ascension. All syenitic units share important geochemical signatures with high contents of LILE such as Ba (4000-10,000 ppm) and Sr (2000-4500 ppm), as well as P2O5 (1-2%) and have strongly fractionated LREE patterns ((La/Yb)N = 40-120; La = 100-400 ppm). An important contrast between silica-oversaturated and saturated syenites is the higher Al2O3 content in the former, reflected in higher normative anorthite, mostly hosted in high temperature alkali feldspar. The Pedra Branca syenites have 87Sr/86Sr(t) = 0.7077 to 0.7078 and unradiogenic Nd (ɛNd(t) ~ - 8) and Pb (206Pb/204Pb = 17.2-17.3); this isotope signature, associated with high LREE/HFS ratios indicates that the parent melts were generated in enriched (metasomatic phlogopite-clinopyroxenite) portions of the shallow (lithospheric) continental mantle affected by previous subduction. The chemical characteristics of the silica-oversaturated syenites and their association with microgranular dioritic enclaves are suggestive that their contrasts with the

  18. Molecular mapping and validation of SrND643: a new wheat gene for resistance to the stem rust pathogen Ug99 race group

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study reports the identification of a new gene conferring resistance to Puccinia graminis f. sp. tritici (Pgt) race Ug99 in wheat (Triticum aestivum L.). Advanced wheat breeding line ND643/2*Weebill1 carries stem rust resistance gene, temporarily designated as SrND643, effective against Ug99 gr...

  19. Mafic dykes intrusive into Pre-Cambrian rocks of the São Luís cratonic fragment and Gurupi Belt (Parnaíba Province), north-northeastern Brazil: Geochemistry, Sr-Nd-Pb-O isotopes, 40Ar/39Ar geochronology, and relationships to CAMP magmatism

    NASA Astrophysics Data System (ADS)

    Klein, Evandro L.; Angélica, Rômulo S.; Harris, Chris; Jourdan, Fred; Babinski, Marly

    2013-07-01

    /86Sr200 = 0.7035, and 206Pb/204Pb of 16.88, and the more enriched trace-elements signature among the four groups. The chemical and isotopic compositions and trends of the HTi-1/HTi-2/EHTi types are consistent with their derivation from an asthenosphere-derived parental magma further modified by differentiation and minimal crust contamination (higher in the HTi-2 and EHTi types), and by the derivation of one type from another via fractional crystallization. These high- and evolved high-TiO2 types show ages and some chemical and isotopic features that are consistent with those of the CAMP magmatism. Some differences found are ascribed to petrogenetic processes, such as magma differentiation. A combination of warming of the mantle and edge-driven convection beneath the Pangea supercontinent after the closure of the Neoproterozoic (Brasiliano/Pan-African) orogenies in the Ediacaran-Cambrian boundary might have triggered the magmatic event. The low-Si type shows paired Ta-Nb and Zr-Hf depletions, and depleted Sr-Nd (average 143Nd/144Nd200 = 0.512687; 87Sr/86Sr200 = 0.703) and enriched Pb (206Pb/204Pb of 18.66) isotopic compositions that may be interpreted to result either from interaction of a subcontinental lithospheric mantle with products of an earlier subduction or by contamination of the mantle-derived magma during ascent and emplacement in the continental crust. It is hypothesized that these dykes were emplaced in the Ediacaran-Cambrian boundary, after the Neoproterozoic orogeny that built up the Gurupi Belt and in the early extensional stages that preceded the formation of the Parnaíba Basin.

  20. Chronology, geochemistry and Sr-Nd isotope studies of Jurassic intrusions in the Diyanqinamu porphyry Mo mine, central Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Sun, Hairui; Huang, Zhilong; Li, Wenbo; Leng, Chengbiao; Ma, Deyun; Zhang, Xingchun

    2014-07-01

    Available cores of porphyritic granite and aplitic granite from the Diyanqinamu porphyry Mo deposit in the north central Great Xing’an Range presented an opportunity to examine and analyze Mesozoic igneous rocks far from the Paleo-Pacific subduction zone. The Diyanqinamu granites are highly fractionated I-type, distinguished from the M-, A- or S-type granite by: high SiO2, and Rb; low Zr, Nb, Y, and Ce; low Fe2O3total/MgO and (K2O + Na2O)/CaO ratios; low alumina saturation index (<1.1); low initial ISr ratios (0.70137-0.70451); positive εNd(t) values (2.37-3.77); and negative correlation between P2O5 and SiO2. The aplitic granites were generated by fractional crystallization of the porphyritic granite, as evidenced by: spatial proximity; consistent zircon U-Pb ages (156 Ma) within error; correlations between other oxides and SiO2 in Haker diagrams; low Ba, Sr, Nb, P, Ti, Eu; linear relationship in both (La/Yb)N vs. La and Sr vs. Ba diagrams; and, decreasing LREE and ∑REE with increasing SiO2. The Diyanqinamu granites have young depleted-mantle two-stage model ages (avg. TDM2 = 660 Ma) similar to those of most Mesozoic voluminous felsic magmas in northeastern China, and were likely sourced from pre-existent crustal components both “old” and juvenile that had been juxtaposed during the tectonic evolution of the Paleo-Asian Ocean. These granites project in the transitional field from syn-collision to post-collision tectonic settings on tectonic discrimination diagrams, implying emplacement in an extensional environment. Extensional volcanism and basin formation in the Great Xing’an Range region in Late Jurassic is coeval with the Diyanqinamu granites, demonstrating that post-orogenic lithospheric extension related to the closure of the Mongol-Okhotsk Ocean was the main driving force for Late Jurassic magmatism in this region.

  1. Molecular Mapping and Validation of SrND643: A New Wheat Gene for Resistance to the Stem Rust Pathogen Ug99 Race Group.

    PubMed

    Basnet, Bhoja R; Singh, Sukhwinder; Lopez-Vera, Eric E; Huerta-Espino, Julio; Bhavani, Sridhar; Jin, Yue; Rouse, Matthew N; Singh, Ravi P

    2015-04-01

    This study reports the identification of a new gene conferring resistance to the Ug99 lineage of races of Puccinia graminis f. sp. tritici in wheat (Triticum aestivum L.). Because the virulent races of stem rust pathogen continue to pose a serious threat in global wheat production, identification and molecular characterization of new resistance genes remains of utmost important to enhance resistance diversity and durability in wheat germplasm. Advanced wheat breeding line 'ND643/2*Weebill1' carries a stem rust resistance gene, temporarily designated as SrND643, effective against the Ug99 group of P. graminis f. sp. tritici races at both seedling and adult growth stages. This study was conducted to map the chromosomal location of SrND643 and identify closely linked molecular markers to allow its selection in breeding populations. In total, 123 recombinant inbred lines, developed by crossing ND643/2*Weebill1 with susceptible line 'Cacuke', were evaluated for stem rust response in field nurseries at Njoro, Kenya, during two growing seasons in 2010, and were genotyped with DNA markers, including Diversity Arrays Technology, simple sequence repeats (SSR), and single-nucleotide polymorphisms. Linkage mapping tagged SrND643 at the distal end of chromosome 4AL, showing close association with SSR markers Xgwm350 (0.5 centimorgans [cM]), Xwmc219 (4.1 cM), and Xwmc776 (2.9 cM). The race specificity of SrND643 is different from that of Sr7a and Sr7b, indicating that the resistance is conferred by a gene at a new locus or by a new allele of Sr7. The flanking markers Xgwm350 and Xwmc219 were predictive of the presence of SrND643 in advanced germplasm, thus validating the map location and their use in marker-assisted selection.

  2. Isotopic studies of the Eye-Dashwa Lakes pluton and the long-term integrity of whole-rock and mineral systems

    USGS Publications Warehouse

    Peterman, Zell E.; Kamineni, D.C.

    1990-01-01

    This report presents results of isotopic studies of the Eye-Dashwa Lakes pluton, located near Atikokan, Ontario. Suites of pristine 'unaltered' and 'highly altered' core samples from deep boreholes were used to study Rb-Sr, U-Th-Pb and Sr-Nd systematics, whole-rock Pb isotopes and fission track dating of apatite. The results have been used to investigate natural analogues for radionuclide migration in the geosphere, the tectonic stability of the pluton and the extent of water-rock interaction in fracture zones.

  3. Isotopic and REE studies of lunar basalt 12038 - Implications for petrogenesis of aluminous mare basalts

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Wooden, J. L.; Shih, C.-Y.; Wiesmann, H.; Bansal, B. M.

    1981-01-01

    Sr, Nd, and Sm isotopic studies of lunar basalt 12038, one of the so-called aluminous mare basalts, are reported. The evolution of the Sr and Nd isotopic compositions and the rare earth element (REE) abundances is successfully modeled within the framework of the model developed by Nyquist et al. (1977, 1979) for Apollo 12 olivine-pigeonite and ilmenite basalts. It is pointed out that the isotopic and trace element features of 12038 can by modeled as produced by partial melting of a cumulate mantle source which crystallized from a lunar magma ocean with a chondrite-normalized REE pattern of constant negative slope. Chondrite-normalized La/Yb is equal to 2.2 for this hypothetical magma ocean pattern.

  4. Petrogenesis and economic potential of the Erhongwa mafic-ultramafic intrusion in the Central Asian Orogenic Belt, NW China: Constraints from olivine chemistry, U-Pb age and Hf isotopes of zircons, and whole-rock Sr-Nd-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Qian, Zhuang-Zhi; Li, Chusi; Xia, Ming-Zhe; Yang, Su-Hong

    2013-12-01

    The Erhongwa mafic-ultramafic intrusion is located in the southern margin of the Central Asian Orogenic Belt in northern Xinjiang where many early-Permian mafic-ultramafic intrusions host important Ni-Cu sulfide deposits. In this paper we report zircon U-Pb age, olivine chemistry and integrated whole-rock chemical and isotopic compositions for the Erhongwa mafic-ultramafic intrusion. This intrusion is composed of lherzolites and gabbroic rocks. The U-Pb age of zircon from a large olivine gabbro sample from the intrusion is 283.1 ± 1.5 Ma, which indicates that the Erhongwa intrusion is contemporaneous with the early-Permian sulfide ore-bearing mafic-ultramafic intrusions in the central Tianshan region. Olivine from the Erhongwa intrusion contains up to 89.5 mol% Fo and 3000 ppm Ni, which are the highest among all known early-Permian mafic-ultramafic intrusions in the region. The occurrence of small sulfide inclusions in the most primitive olivine and significant Ni depletion in more fractionated olivine in the Erhongwa intrusion indicate that sulfide segregation took place during olivine fractional crystallization. The Erhongwa intrusive rocks are characterized by light REE enrichment relative to heavy REE, negative Nb anomalies, positive εNd (t = 283 Ma) values from + 6.3 to + 7.7, low initial 87Sr/86Sr ratios from 0.7034 to 0.7036, initial 206Pb/204Pb ratios from 17.8 to 17.9 and zircon εHf values from 8.0 to 15.5. The Erhongwa mafic-ultramafic rocks and coeval A-type granites in the region have similar isotopic compositions but the former have lower Th/Nb ratios than the latter. These similarities and differences are consistent with the interpretation that the Erhongwa magma formed by the mixing of a mafic magma derived from a depleted mantle with a granitic melt derived from a juvenile arc crust. It is deduced that sulfide saturation in the Erhongwa magmatic system was related to the magma mixing event at depth. More significant sulfide mineralization may

  5. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    NASA Technical Reports Server (NTRS)

    Patchett, P. J.

    1983-01-01

    The Lu-176-Hf-176 isotope method and its applications in earth sciences are discussed with regard to planetary-evolution studies. From new data on basalts from oceanic islands, Hf-176/Hf-177 and Nd-143/Nd-144 are found to display a single linear isotopic variation in the suboceanic mantle, whereas considerable divergences occur in Hf-176/Hf-177-Sr-87/Sr-86 and Nd-143/Nd-144-Sr87/Sr-86 diagrams. With the acquisition of further Hf-Sr-Nd isotopic data, these discordant Sr-87/Sr-86 relationships may allow a distinction between processes such as mantle metasomatism, influence of sea-water altered material in the magma source, or recycling of sediments into the mantle. The best quality Hf isotope data are obtained from granitoid or zircons, and are most suitable for studying ancient terrestrial Hf isotopic variations. Lu-Hf is shown to be a viable method for dating ancient terrestrial and extraterrestrial samples, but is unlikely to find wide application in pure chronological studies because it offers little advantage over existing methods.

  6. Stable isotope studies

    SciTech Connect

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  7. Minerals as mantle fingerprints: Sr-Nd-Pb-Hf in clinopyroxene and He in olivine distinguish an unusual ancient mantle lithosphere beneath the East African Rift System

    NASA Astrophysics Data System (ADS)

    Nelson, W. R.; Shirey, S. B.; Graham, D. W.

    2011-12-01

    The East African Rift System is a complex region that holds keys to understanding the fundamental geodynamics of continental break-up. In this region, the volcanic record preserves over 30 Myrs of geochemical variability associated with the interplay between shallow and deep asthenospheric sources, continental lithospheric mantle, and continental crust. One fundamental question that is still subject to debate concerns the relationship between the lithospheric mantle and the voluminous flood basalt province that erupted at ~30 Ma in Ethiopia and Yemen. Whole-rock Re-Os isotopic data demonstrate the high-Ti (HT2) flood basalts (187Os/188Ost = 0.1247-0.1329) and peridotite xenoliths (187Os/188Ost = 0.1235-0.1377) from NW Ethiopia have similar isotopic compositions. However, Sr-Nd-Pb-Hf isotopic signatures from peridotite clinopyroxene grains are different from those of the flood basalts. The peridotite clinopyroxene separates bear isotopic affinities to anciently depleted mantle (87Sr/86Sr = 0.7019-0.7029; ɛNd = 12.6-18.5; ɛHf = 13.8-27.6) - more depleted than the MORB source - rather than to the OIB-like 30 Ma flood basalts (87Sr/86Sr ~ 0.704; ɛNd = 4.7-6.7; ɛHf = 12.1-13.5). Peridotite clinopyroxenes display two groups of 206Pb/204Pb compositions: the higher 206Pb/204Pb group (18.7-19.3) is compositionally similar to the flood basalts (206Pb/204Pb = 18.97-19.02) whereas the lower 206Pb/204Pb group (17.1-17.9) overlaps with depleted mantle. This suggests that the Pb isotope systematics in some of the peridotites have been metasomatically perturbed. Helium isotopes were analyzed by crushing olivine separated from the peridotites and the flood basalts. Olivine in the peridotites has low He concentrations (0.78-4.7 ncc/g) and low 3He/4He (4.6-6.6 RA), demonstrating that they cannot be the petrogenetic precursor to the high 3He/4He (>12 RA) flood basalts. Notably, these peridotites have 3He/4He signatures consistent with a lithospheric mantle source. Therefore

  8. Isotope fractionation studies of molybdenum

    NASA Astrophysics Data System (ADS)

    Wieser, M. E.; de Laeter, J. R.; Varner, M. D.

    2007-08-01

    Mass spectrometric studies of the isotopic composition of molybdenum have become an active area of research in stable isotope geochemistry, biogeochemistry and cosmochemistry. The redox chemistry of Mo, together with its proclivity for covalent bonding, indicates its importance in isotope fractionation studies such as palaeoceanography. The measurement of the magnitude of isotope fractionation of Mo in natural systems is a challenging task, in that natural fractionation has to be carefully distinguished from chemical and instrumental isotope fractionation. An ion exchange chemical separation procedure has been developed with high efficiency and low blank, to ensure that the isobaric elements Zr and Ru are removed from the samples before mass spectrometric analysis. The isotope fractionation resulting from this procedure is 0.14[per mille sign] per u. The isotopic composition of Mo of a Laboratory Standard has been measured by positive and negative thermal ionization mass spectrometry (P-TIMS and N-TIMS, respectively), to give an isotope fractionation of 6.4[per mille sign] and 0.5[per mille sign] per u, respectively, with respect to the absolute isotope abundances of Mo. In both cases the lighter isotopes are enhanced with respect to the heavier isotopes. An ascorbic acid activator has enabled the sensitivity of P-TIMS to be improved as compared to traditional methods. The same experiment was repeated using a multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS) to give an isotope fractionation of approximately 17.0[per mille sign] per u. In this case the heavier isotopes are enhanced with respect to the lighter isotopes. The strengths and weaknesses of these three mass spectrometric techniques are evaluated. We conclude that MC-ICP-MS is the optimum mass spectrometric method for accurately measuring the isotope fractionation of Mo in natural materials, provided chemical and instrumental isotope fractionation can be resolved from naturally

  9. The longevity of the South Pacific isotopic and thermal anomaly

    USGS Publications Warehouse

    Staudigel, H.; Park, K.-H.; Pringle, M.; Rubenstone, J.L.; Smith, W.H.F.; Zindler, A.

    1991-01-01

    The South Pacific is anomalous in terms of the Sr, Nd, and Pb isotope ratios of its hot spot basalts, a thermally enhanced lithosphere, and possibly a hotter mantle. We have studied the Sr, Nd, and Pb isotope characteristics of 12 Cretaceous seamounts in the Magellans, Marshall and Wake seamount groups (western Pacific Ocean) that originated in this South Pacific Isotopic and Thermal Anomaly (SOPITA). The range and values of isotope ratios of the Cretaceous seamount data are similar to those of the island chains of Samoa, Tahiti, Marquesas and Cook/Austral in the SOPITA. These define two major mantle components suggesting that isotopically extreme lavas have been produced at SOPITA for at least 120 Ma. Shallow bathymetry, and weakened lithosphere beneath some of the seamounts studied suggests that at least some of the thermal effects prevailed during the Cretaceous as well. These data, in the context of published data, suggest: 1. (1)|SOPITA is a long-lived feature, and enhanced heat transfer into the lithosphere and isotopically anomalous mantle appear to be an intrinsic characteristic of the anomaly. 2. (2)|The less pronounced depth anomaly during northwesterly plate motion suggests that some of the expressions of SOPITA may be controlled by the direction of plate motion. Motion parallel to the alignment of SOPITA hot spots focusses the heat (and chemical input into the lithosphere) on a smaller cross section than oblique motion. 3. (3)|The lithosphere in the eastern and central SOPITA appears to have lost its original depleted mantle characteristics, probably due to enhanced plume/lithosphere interaction, and it is dominated by isotopic compositions derived from plume materials. 4. (4)|We speculate (following D.L. Anderson) that the origin of the SOPITA, and possibly the DUPAL anomaly is largely due to focussed subduction through long periods of the geological history of the earth, creating a heterogeneous distribution of recycled components in the lower mantle

  10. A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

    USGS Publications Warehouse

    Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

    2014-01-01

    Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and

  11. Late Eocene-Miocene tectono-magmatic response to the Indian- Eurasian plate collision: constraints from structural analysis, and Sr-Nd and Hf geochemistry of leucocratic intrusions along the Ailao Shan Red-River shear zone, SE Tibet

    NASA Astrophysics Data System (ADS)

    Liu, J.; Tang, Y.; Cao, S.; Ngyuen, Q.; Song, Z.; Tran, M.; Chen, Y.; Ji, M.; Zhang, Z.; Zhao, Z.

    2010-12-01

    The over 1000 km Ailao Shan-Red River (ASRR) shear zone is one of the most important geological discontinuities in Southeast Asia. Great controversies remain on the nature of the shear zone and its role in shaping the tectonic framework of Southeast Asia. Our observation reveals the existence of the Paleogene high potassic alkaline rocks and calc-alkaline intrusions (>30Ma) and the late Oligocene to early Miocene calc-alkaline granitic rocks (28-21Ma). The former are concordant dykes and are generally strongly sheared into mylonitic rocks. The latter are either concordant and show weak strain fabric, or discordant and show no strain fabric. Meanwhile, they have distinct REE, Sr-Nd, Hf isotope signatures and are different in mineralizing features. The Paleogene intrusions are characterized by enriched LREE and depleted HREE without any Eu anomalies (whole rock). Whole rock Sr-Nd (87Sr/86Sr(i): 0.7069 to 0.7098; ɛNd(t): -7.98 to -3.31) and in situ Zircon Hf isotope (-0.79 to +6.2) analyses yield a binary mixing trend between the mantle- and supracrustal-derived melts for the Paleogene magma. Here our new data suggest that most of the Paleogene magmatic rocks are either sheared high potassium alkaline rocks or deformed calc-alkaline intrusions. They are identical to and are the deformed counterparts of rocks from the two Paleogene mineralizing magmatic provinces on both sides of the ASRR shear zone, i.e. the Jinping-Fan Si Pan province and the Dali-Beiya province. These two types of leucocratic rocks are formed as the result of post-collisional delamination of a thickened crust, and deformed and offset by the left lateral shearing along the ASSR shear zone. The late Oligo-Miocene calc-alkaline granitic rocks are localized within the ASRR shear zone. They are in overall concordant to the mylonitic foliation in the shear zone and preserve microstructures typical of syn- to late kinematic emplacement. They have negative Eu anomalies, variable but mostly higher Sr ratios

  12. Oxygen isotope studies and compilation of isotopic dates from Antarctica

    SciTech Connect

    Grootes, P.M.; Stuiver, M.

    1986-01-01

    The Quaternary Isotope Laboratory, alone or in collaboration with other investigators, is currently involved in a number of oxygen-isotope studies mainly in Antarctica. Studies of a drill core from the South Pole, seasonal oxygen-18 signals preserved in the Dominion Range, isotope dating of the Ross Ice Shelf, oxygen-18 profiles of the Siple Coast, McMurdo Ice Shelf sampling, and a data compilation of radiometric dates from Antarctica are discussed.

  13. 40Ar/ 39Ar ages and Sr-Nd-Pb-Os geochemistry of CAMP tholeiites from Western Maranhão basin (NE Brazil)

    NASA Astrophysics Data System (ADS)

    Merle, Renaud; Marzoli, Andrea; Bertrand, Hervé; Reisberg, Laurie; Verati, Chrystèle; Zimmermann, Catherine; Chiaradia, Massimo; Bellieni, Giuliano; Ernesto, Marcia

    2011-03-01

    The Central Atlantic Magmatic Province (CAMP), emplaced at the Triassic-Jurassic (T-J) boundary (~ 200 Ma), is among the largest igneous provinces on Earth. The Maranhão basin in NE Brazil is located around 700 km inland and 2000 km from the site of the earliest Pangea disruption. The CAMP tholeiites occur only in the western part of the basin and have been described as low and high-Ti. Here we document the occurrence of two sub-groups among the high-Ti tholeiites in the Western Maranhão basin. The major and trace elements and the Sr-Nd-Pb isotopic ratios define three chemical groups corresponding to the low-Ti (TiO 2 < 1.3 wt.%), high-Ti (TiO 2 ~ 2.0 wt.%) and evolved high-Ti (TiO 2 > 3 wt.%) western Maranhão basin tholeiites (WMBT). The new 40Ar/ 39Ar plateau ages obtained on plagioclase separates for high-Ti (199.7 ± 2.4 Ma) and evolved high-Ti WMBT (197.2 ± 0.5 Ma and 198.2 ± 0.6 Ma) are indistinguishable and identical to those of previously analyzed low-Ti WMBT (198.5 ± 0.8 Ma) and to the mean 40Ar/ 39Ar age of the CAMP (199 ± 2.4 Ma). We also present the first Re-Os isotopic data for CAMP basalts. The low and high-Ti samples display mantle-like initial ( 187Os/ 188Os) i ranging from 0.1267 to 0.1299, while the evolved high-Ti samples are more radiogenic (( 187Os/ 188Os) i up to 0.184) We propose that the high-Ti WMBT were derived from the sub-lithospheric asthenosphere, and contaminated during ascent by interaction with the subcontinental lithospheric mantle (SCLM). The evolved high-Ti WMBT were derived from the same asthenospheric source but experienced crustal contamination. The chemical characteristics of the low-Ti group can be explained by partial melting of the most fertile portions of the SCLM metasomatized during paleo-subduction. Alternatively, the low-Ti WMBT could be derived from the sub-lithospheric asthenosphere but the resulting melts may have undergone contamination by the SCLM. The occurrences of high-Ti basalts are apparently not

  14. Hf-Nd-Sr isotopic fingerprinting of mineral dust from Asian and North African deserts

    NASA Astrophysics Data System (ADS)

    Ji, J.; Zhao, W.; Balsam, W.

    2015-12-01

    Mineral dust accounts for more than 50% of the atmospheric dust loading and plays an important role in the marine and terrestrial geochemical cycles. The deserts in North Africa, Northern China and Southern Mongolia are the major sources of mineral dust and have been studied intensively over past decades, especially with Sr, Nd and recently Hf isotopes which are seen as powerful tools to identify source areas. However, the isotopic compositions of dust are highly dependent on particle size hindering the ability to accurately identify dust provenance. The clay fraction (<2 μm) comprises about half of all mineral dust and has unique minerals phases dominanted by clay minerals. Once the clay-sized particles are deflated to the upper troposphere, they are transported over long distances and are removed from the atmosphere mainly by wet deposition. Thus, the clay-sized isotopic fingerprints from deserts may be ideal targets not only for tracking the provenance tracing of long-distance transported mineral dust, but also to provide an unparalleled window for understanding the global dust cycle, especially eolian dust preserved in deep-sea sediments and ice cores. In this work we investigate multivariate joint radiogenic Sr, Nd, and Hf isotopic compositions obtained from complete dissolution of clay-sized fractions of surface sediments from Asian and North African deserts. Asian dust source samples included the ten Northern China deserts and sandy lands - the Taklimakan, Gurbantunggut, Qaidam, Badaim Jaran, Tengger and Mu Us deserts, and the Hobq, Hulun Buirm, Onqin Daga and Horqin sandy land - and Mongolian Gobi desert. North African dust samples were from four transects in the Sahara and Sahel from Mali, Togo, Egypt and Morocco . Our results on the clay-sized isotopic measurements of these samples describe (1) the general characteristics of dusts from the Asian with ɛNd from -17.3 to 0.98, ɛHf from -5.95 to 3.68 and 87Sr/86Sr from 0.710113 to 0.73306, and North

  15. Isotopic variations within upper oceanic crust at IODP Site 1256: Implications for crustal recycling and the formation of ocean island basalts

    NASA Astrophysics Data System (ADS)

    Duggen, S.; Hoernle, K.; Geldmacher, J.; Hauff, F.

    2007-12-01

    The origin of ocean island basalts (OIBs) is a fundamental question facing Earth scientists. It is commonly agreed that lithospheric material recycled in the mantle is involved in the magma source of OIBs. The relative importance of 1) subducted altered oceanic basaltic crust (AOC), 2) subducted marine sediments and/or 3) delaminated metasomatised subcontinental lithosphere and continental lower crust remains to be resolved. We examine the geochemical composition of a complete in situ section of oceanic crust drilled at Site 1256 during IODP Expeditions 309 and 312. It includes the extrusive layer, sheeted dikes and gabbros of ca. 15 Ma old oceanic crust of the Cocos Plate formed during a period of superfast spreading at the East Pacific Rise. Modeling in the Sr-Nd-Pb-isotope space and comparison with present day radiogenic isotope ratios of OIBs provides constraints on the significance of recycled oceanic crust in the OIB mantle source(s). Our study shows that the generation of sulphides during low- and high-temperature alteration of oceanic crust has a strong influence on U/Pb and Th/Pb ratios and whether an AOC domain evolves relatively low or high Pb-isotope ratios over geological timescales. The model suggests that AOC as the sole precursor material, modified during the subduction process, and after relatively low to moderate recycling ages of ca. 300-800 Ma, is sufficient to explain the Sr-Nd-Pb-isotopic composition of OIBs with Pb-isotopic compositions along or below the Northern Hemisphere Reference Line (NHRL) and relatively high Nd-isotope ratios (e.g. Canaries, Galapagos, Iceland, Madeira). This indicates that additional EM-components, potentially associated with recycled lithospheric material such as subducted sediments, lower continental crust or subcontinental lithosphere, are not required for an array of OIBs, but are only necessary to explain OIBs with Pb-isotope ratios above the NHRL and relatively low Nd- isotope ratios (e.g. Pitcairn, Tristan

  16. Weathering geochemistry and Sr-Nd fingerprints of equatorial upper Nile and Congo muds

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; Padoan, Marta; Setti, Massimo; Najman, Yani; Peruta, Luigi; Villa, Igor M.

    2013-02-01

    Abstract This <span class="hlt">study</span> investigates processes of sediment generation in equatorial central Africa. An original, complete and integrated mineralogical-geochemical database on silt-sized sediments derived from different parent rocks (basalt, granite, gneiss, metapsammite, sandstone) along the East African Rift from 5°S in Tanzania to 5°N in Sudan is presented and used to assess the incidence of diverse factors controlling sediment composition (source-rock lithology, geomorphology, hydraulic sorting, grain size, recycling), with particular emphasis on chemical weathering.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeCoA.167..286B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeCoA.167..286B"><span id="translatedtitle"><span class="hlt">Isotopic</span> disequilibrium and lower crustal contamination in slowly ascending magmas: Insights from Proterozoic anorthosites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bybee, G. M.; Ashwal, L. D.</p> <p>2015-10-01</p> <p>Many Proterozoic anorthosite massifs show crustal <span class="hlt">isotopic</span> signatures that have, for decades, fuelled debate regarding the source of these temporally-restricted magmas. Are these signatures indicative of lower crustal melting or of significant assimilation of crustal material into mantle-derived magmas? Traditional whole rock <span class="hlt">isotopic</span> tracers (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb and Os), like other geochemical, petrological and experimental tools, have failed to identify unambiguously the origins of the crust-like signature and resolve the source controversies for these feldspathic, cumulate intrusives. We make use of high precision <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopic</span> compositions of mineral phases (plag, opx, mag) and comagmatic, high-pressure orthopyroxene megacrysts as well as whole rock anorthosites/leuconorites from the Mealy Mountains Intrusive Suite (MMIS) and the Nain Plutonic Suite (NPS) to probe the origin of the crustal <span class="hlt">isotopic</span> signatures and assess the importance of differentiation at lower crustal depths. This selection of samples represents fragments from various stages of the polybaric ascent of the magmas, while the <span class="hlt">study</span> of the Mealy Mountains Intrusive Suite and the Nain Plutonic Suite is instructive as each is intruded into crust of significantly different age and <span class="hlt">isotopic</span> composition. We observe marked differences in the whole-rock <span class="hlt">isotopic</span> composition of Proterozoic anorthosites and high-pressure megacrysts (e.g. εNd;T = +2 to -10) intruded into crustal terranes of different ages and <span class="hlt">isotopic</span> compositions. Evidence for varying degrees of internal <span class="hlt">isotopic</span> disequilibrium (ΔNd, ΔSr, ΔPb) in anorthosites from these different terranes reinforces the notion that crustal contamination, and more importantly, the nature of the crustal assimilant, has a profound influence on the chemical signature of Proterozoic anorthosites. While most samples from the MMIS and NPS show significant and measurable ΔNd and ΔPb disequilibrium, ΔSr compositions cluster around zero. This decoupling in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.189..236C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.189..236C"><span id="translatedtitle">High-precision lead <span class="hlt">isotopes</span> and stripy plumes: Revisiting the Society chain in French Polynesia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cordier, Carole; Chauvel, Catherine; Hémond, Christophe</p> <p>2016-09-01</p> <p>An increasing number of geochemical <span class="hlt">studies</span> looked for spatial organization of the <span class="hlt">isotopic</span> variations along Pacific volcanic island chains (e.g., Hawaii, Marquesas, Samoa and Society Islands) in order to discuss the possible zoning of the plume conduits. Here, we reexamine the occurrence of <span class="hlt">isotopic</span> stripes in the Society archipelago in French Polynesia, using new <span class="hlt">Sr-Nd</span>-Hf-Pb <span class="hlt">isotope</span> ratios of sixty-six lavas from six islands (Mehetia, Moorea, Maupiti, Huahine, Raiatea, Bora-Bora). We demonstrate that the Pb <span class="hlt">isotope</span> variability observed using literature data is an analytical artifact related to the poor control of mass fractionation during Pb measurements by conventional TIMS technique. New MC-ICP-MS Pb data demonstrate that the <span class="hlt">isotopic</span> stripes as previously defined disappear. They rather show that individual islands cover a significant part of the entire <span class="hlt">isotopic</span> range of the chain. We suggest, therefore, that the dominant characteristic of the Society plume is small-scale heterogeneities, evenly distributed within the plume conduit. At a global scale, we show that some ocean island chains with similar geochemical and <span class="hlt">isotopic</span> characteristics, such as Samoa and Society Islands, define different arrays when variations of Nd with high-precision Pb <span class="hlt">isotopes</span> are considered. We proposed that this puzzling observation might record differences in recycling age of the basalt + sediment mixture subducted into the mantle and sampled by mantle plume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V33A2714J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V33A2714J"><span id="translatedtitle">Mantle Heterogeneity and Mixing Beneath the Bouvet Triple Junction Region: Hf <span class="hlt">Isotope</span> Constraints from the Westernmost Southwest Indian Ridge (0-11deg.E)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Janney, P. E.; le Roex, A. P.</p> <p>2013-12-01</p> <p>We have undertaken new Hf (and supplementary <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb) <span class="hlt">isotope</span> and trace element measurements of MORB from the westernmost Southwest Indian Ridge (SWIR; 0 to 11 deg. E) in order to clarify mixing relationships and the effect of the Bouvet and other local hot spots on the composition of the upper mantle beneath the Bouvet Triple Junction (BTJ) region. The new data are fully consistent with the findings of previous <span class="hlt">studies</span> (le Roex et al., J. Petrol., 1983; Kurz et al., GCA, 1998) that <span class="hlt">isotopic</span> heterogeneity in this region is largely explained by mixing between a moderately depleted mantle source (i.e., ɛHf ≈ +14, ɛNd ≈ +9, 87Sr/86Sr ≈ 0.7026; 206Pb/204Pb ≈ 18.5) and an enriched component <span class="hlt">isotopically</span> similar to Bouvet OIB. Unlike the pattern expressed by He <span class="hlt">isotopes</span> (Kurz et al., GCA, 1998; Georgen et al., EPSL, 2003) the strength of the Bouvet hot spot signature in terms of Hf-<span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotope</span> ratios is not well correlated with distance from Bouvet Island along ridge, except in the most general sense. Some MORB from 0-11E do approach the Hf-<span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopic</span> composition of Bouvet OIB. However, the most extreme <span class="hlt">isotopic</span> compositions (with ɛHf values that are slightly lower than, and Nd and Pb <span class="hlt">isotope</span> compositions that are equivalent to, those of Bouvet OIB), are actually found in MORB from the 11-16E oblique spreading segment of the SWIR (le Roex et al., CMP, 1992; Janney et al., J. Petrol., 2005), located further from Bouvet Island than the segments at 0-11E. The lack of a strong correlation between the radiogenic <span class="hlt">isotope</span> ratios of SWIR MORB and proximity to the Bouvet hot spot in this region supports the notion that local conditions of melting of a lithologically heterogeneous mixture of enriched, Bouvet hot spot-derived and depleted mantle materials plays the dominant role in controlling the radiogenic <span class="hlt">isotope</span> composition of western SWIR MORB (le Roex et al., CMP, 1992; Salters & Dick, Nature, 2002). The depleted mantle present beneath the western</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Litho.160...98L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Litho.160...98L"><span id="translatedtitle">Adakitic-like magmatism in western Ossa-Morena Zone (Portugal): Geochemical and <span class="hlt">isotopic</span> constraints of the Pavia pluton</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lima, S. M.; Neiva, A. M. R.; Ramos, J. M. F.</p> <p>2013-02-01</p> <p>Granitic rocks are a major component of the Earth's continental crust and occur in a wide variety of tectonic settings. Their chemical and <span class="hlt">isotopic</span> characterization is crucial to the recognition of the potential sources and mechanisms involved in their generation. In this <span class="hlt">study</span>, we present the first whole rock chemical and <span class="hlt">isotopic</span> (<span class="hlt">Sr-Nd</span>-O) data for the Pavia pluton (328-317 Ma), located near the western border of the Ossa-Morena Zone (Évora Massif, Portugal). Major and trace element geochemistry suggests that the different granitic phases composing this intrusive body (enclaves, granites (s.l.) and crosscutting dikes) represent independent magma pulses and the majority is similar to TTGs and adakites. The little <span class="hlt">Sr-Nd</span>-O <span class="hlt">isotopic</span> variation, with (87Sr/86Sr)328 = 0.70428-0.70560, ɛNd328 ranging between - 3.4 and + 0.4 and δ18O varying from + 5.6‰ to + 8.4‰ implies an <span class="hlt">isotopically</span> similar protolith for all phases. The most viable mechanism for the generation of the Pavia pluton adakitic-like magmatism is assimilation-fractional crystallization of a mantle-derived magma. This mechanism was also invoked to explain the genesis of other plutons within the Évora Massif but they have a distinct chemistry (typical arc calc-alkaline rocks). The chemical differences between them and the Pavia pluton granitic rocks are interpreted as the result of lower degrees of crustal assimilation and higher degrees of contamination of mantle-derived magmas by the sinking slab (after subduction blocking and subsequent slab break-off).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V33B4869K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V33B4869K"><span id="translatedtitle">Distinguishing Mantle Components by Sr and Nd <span class="hlt">Isotope</span> Analysis of Single Melt Inclusions: Case <span class="hlt">Study</span> on Italian Potassium-rich Lavas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koornneef, J.; Nikogosian, I.; van Bergen, M.; Smeets, R.; Bouman, C.; Schwieters, J. B.; Davies, G. R.</p> <p>2014-12-01</p> <p>Melt inclusions record more extreme <span class="hlt">isotopic</span> variability than their bulk host lavas and offer the potential to better constrain mantle components that contribute to magmatism. <span class="hlt">Isotopic</span> analyses of melt inclusions are, however, challenging because of their limited size. To date, Sr and Pb <span class="hlt">isotope</span> data have been obtained for oceanic islands by application of in situ analysis techniques, either by SIMS or LA-(MC)-ICPMS. Comprehensive <span class="hlt">studies</span> of inclusions from other settings have yet to be performed. Here, we report the first combined Sr and Nd <span class="hlt">isotope</span> data on individual melt inclusions from Pliocene-Quaternary K-rich lavas from mainland Italy, obtained using wet chemistry techniques and TIMS analysis. We use newly developed 1013 Ohm resistors mounted in the feedback loop of Faraday cup amplifiers. Compared to default 1011 Ohm resistors, use of 1013 Ohm resistors results in a 10-fold improvement of the signal-to-noise ratio and more precise data when analysing small ion beams (< 20 mV). Twenty-one olivine hosted (85 - 92 mol % Fo) melt inclusions from seven volcanic centres along the Italian peninsula were analysed. Inclusions were homogenised and analysed for trace elements prior to <span class="hlt">isotopic</span> analysis. 87Sr/86Sr ratios in the melt inclusions range from 0.70508 to 0.71543; 143Nd/144Nd ratios from 0.51175 to 0.51268. Significant differences in 87Sr/86Sr and 143Nd/144Nd were found between melt inclusions and host lavas indicating distinct evolution paths for the lava groundmasses and the primitive melts that were trapped in the phenocrysts. The <span class="hlt">isotopic</span> variability is interpreted to be the result of (1) mixing of melts derived from a heterogeneous mantle modified by subduction-related metasomatism, (2) mingling of distinct batches of olivine-bearing magma within a plumbing system, and (3) local assimilation of crustal material. These preliminary data suggest that combined analysis of individual melt inclusions for trace elements and <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> ratios is a promising</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.181..217N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.181..217N"><span id="translatedtitle">Tracking along-arc sediment inputs to the Aleutian arc using thallium <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nielsen, Sune G.; Yogodzinski, Gene; Prytulak, Julie; Plank, Terry; Kay, Suzanne M.; Kay, Robert W.; Blusztajn, Jerzy; Owens, Jeremy D.; Auro, Maureen; Kading, Tristan</p> <p>2016-05-01</p> <p>Sediment transport from the subducted slab to the mantle wedge is an important process in understanding the chemical and physical conditions of arc magma generation. The Aleutian arc offers an excellent opportunity to <span class="hlt">study</span> sediment transport processes because the subducted sediment flux varies systematically along strike (Kelemen et al., 2003) and many lavas exhibit unambiguous signatures of sediment addition to the sub-arc mantle (Morris et al., 1990). However, the exact sediment contribution to Aleutian lavas and how these sediments are transported from the slab to the surface are still debated. Thallium (Tl) <span class="hlt">isotope</span> ratios have great potential to distinguish sediment fluxes in subduction zones because pelagic sediments and low-temperature altered oceanic crust are highly enriched in Tl and display heavy and light Tl <span class="hlt">isotope</span> compositions, respectively, compared with the upper mantle and continental crust. Here, we investigate the Tl <span class="hlt">isotope</span> composition of lavas covering almost the entire Aleutian arc a well as sediments outboard of both the eastern (DSDP Sites 178 and 183) and central (ODP Hole 886C) portions of the arc. Sediment Tl <span class="hlt">isotope</span> compositions change systematically from lighter in the Eastern to heavier in the Central Aleutians reflecting a larger proportion of pelagic sediments when distal from the North American continent. Lavas in the Eastern and Central Aleutians mirror this systematic change to heavier Tl <span class="hlt">isotope</span> compositions to the west, which shows that the subducted sediment composition is directly translated to the arc east of Kanaga Island. Moreover, quantitative mixing models of Tl and Pb, Sr and Nd <span class="hlt">isotopes</span> reveal that bulk sediment transfer of ∼0.6-1.0% by weight in the Eastern Aleutians and ∼0.2-0.6% by weight in the Central Aleutians can account for all four <span class="hlt">isotope</span> systems. Bulk mixing models, however, require that fractionation of trace element ratios like Ce/Pb, Cs/Tl, and <span class="hlt">Sr/Nd</span> in the Central and Eastern Aleutians occurs after</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMDI31A2558G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMDI31A2558G"><span id="translatedtitle">Hot N Sour Mantle Soup on Indian Plate During Cretaceous- Evidence from Clumped <span class="hlt">Isotope</span> and Geochemical <span class="hlt">Studies</span> of Sung Valley Carbonatite, India</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh, P.; Banerjee, Y.; Tiwari, A.; Srivastava, R. K.</p> <p>2015-12-01</p> <p>Geological processes involved in the formation of Carbonatite rocks are complex and so is the understanding about its formational temperature. Fluid inclusion <span class="hlt">studies</span> (1) on Carbonatite and their associated Ijolites showed a homogenization temperature of 1000-1100°C for Ijoltes and a temperature (T) range of 200-600°C was assigned to the carbonatite melts. Liquid immiscibility process is held responsible for the origin of parental carbonated (ijolititic/ nephelinitic) magma. The homogenization T signifies about a time interval during which there must be a considerable amount of T dropdown soon after the formation of Ijolite and subsequent crystallization of the residual carbonatite magma. However the lack of information about the T of the primary carbonated melt remains as an important area of petrological research. Experimental <span class="hlt">studies</span> suggest a T range of 950-1400°C for the primary carbonate melt (2). Advent of Clumped <span class="hlt">isotope</span> thermometry (3) allowed independent method for estimation of the formational T and provide avenues to derive composition of CO2 in equilibrium with carbonate melt. Earlier attempt involving carbonatites from several locations (4) captured range of T between 83°-416°C . Here we present our observation on calcite growth T in the carbonatites from the Cretaceous Sung valley ultramafic-alkaline-carbonatite complex. Based on stable C,O <span class="hlt">isotope</span> <span class="hlt">study</span> and <span class="hlt">Sr</span>, <span class="hlt">Nd</span> <span class="hlt">isotopic</span> composition a mantle origin- genetically linked with the Kerguelen plume was proposed (5). Clumped <span class="hlt">isotope</span> <span class="hlt">study</span> on the same samples revealed consistent C and O <span class="hlt">isotope</span> compositions, providing Δ47 values ranging from 0.32 to 0.48. δ13C and δ18O (in VPDB) values of the present <span class="hlt">study</span> falls within the "Primary Igneous Carbonatite Field" (6). Using high T thermometry equation (7) we obtained a T range of 137-474 °C for the calcite present in the samples. The T recorded in our <span class="hlt">study</span> is lower than that deduced experimental values of 960-625°C at 0.1 GPa (8) and fluid inclusion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720006187','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720006187"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">studies</span> in returned lunar samples</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alexander, E. C., Jr.</p> <p>1971-01-01</p> <p>Analysis of lunar soil samples returned by Apollo 11 and 12 flights are discussed. <span class="hlt">Isotopic</span> <span class="hlt">studies</span> of the rare gases from Apollo 11 flight lunar samples are presented. The lunar soil analyses indicated the following: (1) high concentrations of solar wind rare gases, (2) <span class="hlt">isotopic</span> match between solar wind gases and gas components in gas-rich meteorites, and (3) rare gases attributable to spallation reactions induced in heavier nuclides by cosmic ray particles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V31A3000M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V31A3000M"><span id="translatedtitle">Re-Os <span class="hlt">Isotopes</span> Distinguish Crust vs. Slab Inputs to Northern Cascade Arc Basalts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mullen, E.; Gannoun, A.; Nauret, F.; Schiano, P.; Weis, D.</p> <p>2015-12-01</p> <p>Delineating the relative contributions of mantle, slab, and crust to arc magmas is particularly challenging in the Cascades where the continental crust is juvenile and contrasts little with magmas in traditional radiogenic <span class="hlt">isotope</span> systems (<span class="hlt">Sr-Nd</span>-Hf-Pb). The Re-Os <span class="hlt">isotope</span> system offers a sensitive technique for evaluating these contributions because even young crust has significantly higher Os ratios than the mantle. We analyzed Re-Os <span class="hlt">isotope</span> ratios in 33 primitive basalts from 9 volcanic centers of the northern Cascade Arc (Garibaldi Volcanic Belt, GVB). Although GVB basalts have mantle-like Sr-Pb-Nd-Hf ratios (Mullen & Weis, 2015, EPSL), the range in 187Os/188Os is very large (0.13-0.99) with [Os] of <1 to 17 ppt. Ten samples of subducting Cascadia Basin sediment and altered Juan de Fuca MORB are associated with high 187Os/188Os (0.68-0.92) and [Os] = 25-132 ppt. The GVB basalts define two groups: Group 1 (Cinder Cone/Mt. Garibaldi, Salal Glacier, Mt. Meager, Indian Pass/Glacier Peak) has low Os <span class="hlt">isotopic</span> ratios (0.13-0.19), only slightly elevated relative to global mantle wedge peridotites (≤0.16), indicating minimal crustal contamination. Group 1 samples lie on Os-Sr <span class="hlt">isotope</span> mixing curves indicating variable sediment input to the mantle. Os ratios of Group 2 basalts (Silverthrone, Bridge River, Elaho, Cheakamus, Mt. Baker, Glacier Peak) extend to extremely high values, up to 0.99, and lie on different Os-Sr mixing curves indicating addition of a crustal contaminant. <span class="hlt">Sr-Nd</span>-Hf-Pb <span class="hlt">isotopic</span> ratios cannot be used to identify this crustal input because Groups 1 and 2 are identical in these <span class="hlt">isotope</span> systems. Interaction with a mafic underplate from older Cenozoic or accreted Mesozoic arcs is likely, and Re-Os analyses of basement samples (in progress) will provide a test of this hypothesis. This <span class="hlt">study</span> reveals that most primitive magmas in the Cascades have suffered variable crustal contamination, but only the Re-Os <span class="hlt">isotope</span> system has the potential to delineate the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/841110','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/841110"><span id="translatedtitle">Advanced diffusion <span class="hlt">studies</span> with <span class="hlt">isotopically</span> controlled materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bracht, Hartmut A.; Silvestri, Hughes H.; Haller, Eugene E.</p> <p>2004-11-14</p> <p>The use of enriched stable <span class="hlt">isotopes</span> combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion <span class="hlt">studies</span> with <span class="hlt">isotopically</span> enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of <span class="hlt">isotopically</span> enriched materials ushered in a new era in the <span class="hlt">study</span> of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of <span class="hlt">studying</span> atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000935','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000935"><span id="translatedtitle">Sudbury project (University of Muenster-Ontario Geological Survey): <span class="hlt">Sr-Nd</span> in heterolithic breccias and gabbroic dikes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Buhl, D.; Deutsch, A.; Lakomy, R.; Brockmeyer, P.; Dressler, B.</p> <p>1992-01-01</p> <p>One major objective of our Sudbury project was to define origin and age of the huge breccia units below and above the Sudbury Igneous Complex (SIC). The heterolithic Footwall Breccia (FB) represents a part of the uplifted crater floor. It contains subrounded fragments up to several meters in size and lithic fragments with shock features (greater than 10 GPa) embedded into a fine- to medium-grained matrix. Epsilon(sub Nd)-epsilon(sub Sr) relationships point to almost exclusively parautochthonous precursor lithologies. The different textures of the matrix reflect the metamorphic history of the breccia layer; thermal annealing by the overlying hot impact melt sheet (SIC) at temperatures greater than 1000 C resulted in melting of the fine crushed material, followed by an episode of metasomatic K-feldspar growth and, finally, formation of low-grade minerals such as actinolite and chlorite. <span class="hlt">Isotope</span> relationships in the Onaping breccias (Gray and Green Member) are much more complex. All attempts to date the breccia formation failed: Zircons are entirely derived from country rocks and lack the pronounced Pb loss caused by the heat of the slowly cooling impact melt sheet (SIC). Rb-Sr techniques using either lithic fragments of different shock stages or the thin slab method, set time limits for the apparently pervasive alkali mobility in these suevitic breccias. The data array and the intercept in the plots point to a major Rb-Sr fractionation around 1.54 Ga ago. This model age is in the same range as the age obtained for the metasomatic matrix of the FB. Rb-Sr dating of a shock event in impact-related breccias seems to be possible only if their matrix had suffered total melting by the hot melt sheet (FB) or if they contain a high fraction of impact melt (suevitic Onaping breccias), whereas the degree of shock metamorphism in rock or lithic fragments plays a minor role. In the Sudbury case, however, the impact melt in the seuvitic breccias is devitrified and recrystallized</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5289979','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5289979"><span id="translatedtitle"><span class="hlt">Isotopic</span> and geochemical <span class="hlt">studies</span> of a Pliocene porphyry-Mo system, Rico, Colorado</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wareham, C.D.</p> <p>1991-01-01</p> <p>The historic mining district of Rico in southern Colorado Mineral Belt contains a Pliocene porphyry-Mo deposit and peripheral epithermal Pb-Zn-Ag deposits, and hot-springs. The porphyry-Mo mineralization is confined almost exclusively to Precambrian greenstone. The epithermal mineralization is hosted by a Paleozoic and Mesozoic sequence dominated by carbonates, but containing evaporites. The system is geologically complex and focused on a resurgent dome which is cored by a horst of Precambrian strata, and cut by reactivated Precambrian basement shears. The shears have controlled the emplacement of the Laramide and Pliocene granitoids in area. The mineralization is associated with more evolved members of the latter suite. <span class="hlt">Sr-Nd</span>-Pb-O <span class="hlt">isotope</span> and minor element data on the granitoid intrusions indicate that they are not simply differentiates of mantle magmas. However, Nd model ages indicate that they are not purely remelts of 1800Ma Precambrian crust. Realistically it is impossible to quantify the relative proportions of crust and mantle material involved in the genesis of the intrusions. Notwithstanding this, the Rico granitoids are <span class="hlt">isotopically</span> distinct from those associated with Climax-type porphyry-Mo deposits in Colorado. Sd-Nd-Pb <span class="hlt">isotope</span> and trace element data on a lamprophyre suite in the area suggest two episodes of mafic magmatism; a period whereby the source was predominantly, OIB-type, asthenospheric mantle. [sigma][sup 34]S data and ore deposit paragenesis indicate that the sulphide S has an igneous origin and that the sulphate S was derived by mobilization of Pennsylvanian evaporites. Modelling of the S <span class="hlt">isotopic</span> data indicates a common S source for the epithermal and porphyry mineralization. The sulphate and sulphide S reservoirs remained essentially decoupled during mineralization. [sigma][sup 34]C data are compatible with the hydrothermal C having been derived by the dissolution and re-precipitation of host sequence carbonate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.3324L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.3324L"><span id="translatedtitle">Origins of diamond-forming fluids: An <span class="hlt">isotopic</span> and trace element <span class="hlt">study</span> of diamonds and silicates from diamondiferous xenoliths</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laiginhas, Fernando; Pearson, D. Graham; McNeill, John; Gurney, John; Nowell, Geoff; Ottley, Chris</p> <p>2010-05-01</p> <p>.W. Harris and O. Navon (2009). A new model for the evolution of diamond-forming fluids: Evidence from microinclusion-bearing diamonds from Kankan, Guinea. Lithos 112, Supp. 2: 660-674. 2) O. Klein-BenDavid, D.G. Pearson, G.M. Nowell, C. Ottley, J.C.R. McNeill, P. Cartigny (2010). Mixed fluid sources involved in diamond growth constrained by <span class="hlt">Sr-Nd</span>-Pb-C-N <span class="hlt">isotopes</span> and trace elements. EPSL 289, 1-2: 123-133. 3) J. McNeill, D.G. Pearson, O. Klein-BenDavid, G.M. Nowell, C.J. Ottley and I. Chinn (2009). Quantitative analysis of trace element concentrations in some gem-quality diamonds. J. Phys.: Condens. Matter 21: 364207 (13pp).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Litho.154..147M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Litho.154..147M"><span id="translatedtitle">Geochemistry, geochronology, and <span class="hlt">Sr-Nd</span> <span class="hlt">isotopes</span> of the Late Neoproterozoic Wadi Kid volcano-sedimentary rocks, Southern Sinai, Egypt: Implications for tectonic setting and crustal evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moghazi, Abdel-Kader M.; Ali, Kamal A.; Wilde, Simon A.; Zhou, Qin; Andersen, Tom; Andresen, Arild; Abu El-Enen, Mahrous M.; Stern, Robert J.</p> <p>2012-12-01</p> <p>The Kid Group is one of the few exposures of Neoproterozoic metavolcano-sedimentary rocks in the basement of southern Sinai in the northernmost Arabian-Nubian Shield. It is divided into the mostly metamorphosed volcaniclastic Melhaq and siliciclastic Um Zariq formations in the north and the mostly volcanic Heib and Tarr formations in the south. The Heib, Tarr, and Melhaq formations reflect an intense episode of igneous activity and immature clastic deposition associated with core-complex formation during Ediacaran time, but Um Zariq metasediments are relicts of an older (Cryogenian) sedimentary sequence. The latter yielded detrital zircons with concordant ages as young as 647 ± 12 Ma, which may indicate that the protolith of Um Zariq schist was deposited after ~ 647 Ma but 19 concordant zircons gave a 206Pb/238U weighted mean age of 813 ± 6 Ma, which may represent the maximum depositional age of this unit. In contrast, a cluster of 11 concordant detrital zircons from the Melhaq Formation yield a weighted mean 206Pb/238U age of 615 ± 6 Ma. Zircons from Heib Formation rhyolite clast define a 206Pb/238U weighted mean age of 609 ± 5 Ma, which is taken to approximate the age of Heib and Tarr formation volcanism. Intrusive syenogranite sample from Wadi Kid yields a 206Pb/238U weighted mean age of 604 ± 5 Ma. These constraints indicate that shallow-dipping mylonites formed between 615 ± 6 Ma and 604 ± 5 Ma. Geochemical data for volcanic samples from the Melhaq and Heib formations and the granites show continuous major and trace element variations corresponding to those expected from fractional crystallization. The rocks are enriched in large ion lithophile and light rare earth elements, with negative Nb anomalies. These reflect magmas generated by melting of subduction-modified lithospheric mantle, an inference that is further supported by ɛNd(t) = + 2.1 to + 5.5. This mantle source obtained its trace element characteristics by interaction with fluids and melts from subducting oceanic crust during the Late Cryogenian time, prior to terminal collision between fragments of East and West Gondwana at ~ 630 Ma. Positive ɛNd(t) values and the absence of pre-Ediacaran zircons in all but Um Zariq metasediments indicate minor interaction with Cryogenian and older crust. A model of extensional collapse following continental collision, controlled mainly by lithospheric delamination and slab break-off is suggested for the origin of the post-collision volcanics and granites at Wadi Kid. No evidence of pre-Neoproterozoic sources was found. Kid Group Ediacaran volcanic rocks are compositionally and chronologically similar to the Dokhan Volcanics of NE Egypt, which may be stratigraphic equivalents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Litho.264..189S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Litho.264..189S"><span id="translatedtitle">Two stage mantle-derived granitic rocks and the onset of the Brasiliano orogeny: Evidence from <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and O <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silva, Thyego R.; Ferreira, Valderez P.; Lima, Mariucha Maria C.; Sial, Alcides N.</p> <p>2016-11-01</p> <p>The elongate Monteirópolis batholith (270 km2) is composed of alkali feldspar granite to granodiorite, it is part of the Águas Belas-Canindé composite batholith and it intruded rocks of the Pernambuco-Alagoas Domain, northeastern Brazil. This batholith is bounded by the NNE-SSW-trending Jacaré dos Homens transpressional shear zone on its southwestern margin, and displays low-angle foliation, coeval to the development of a regional flat-lying foliation. Microgranular dioritic enclaves and amphibole-rich clots are abundant. The mineralogy of this pluton comprises biotite and amphibole as major accessory phases, and titanite and magmatic epidote as trace minerals. Major and trace element chemistry shows high SiO2, total alkalis, Ba and Sr, low Fe# and Nb contents, all of these conferring a high-K calc-alkaline character. The rocks are enriched in LREE and LILE and depleted in HFSE, and show fractionated chondrite-normalized REE patterns with Eu/Eu* = 0.67 to 1.25. Chondrite-normalized spidergrams show marked negative Nb-Ta and Ti anomalies, typical of subduction-related magmas. U-Pb SHRIMP zircon data yielded a crystallization age of 626 ± 4 Ma. Regional structures and U-Pb geochronological data for the Jacaré dos Homens transpressional shear zone suggest that shearing was initiated at ca. 640 Ma. Dilatational movements along this shear zone opened space for magma emplacement. The rocks in this batholith are characterized by slightly negative to slightly positive εNd values (- 0.78 to + 1.06), average Nd-model age of 1.0 Ga, low initial 87Sr/86Sr(626 Ma) values of 0.7050 to 0.7052, and low δ18O values (zircon) of + 5.00 to + 5.94‰ V-SMOW. A possible protolith, Tonian mantle-derived rocks in the lower continental crust, could have been partially melted by underplating of mantle-derived mafic magma during collision of the São Francisco Craton and the Pernambuco-Alagoas Domain during onset of the Brasiliano orogeny.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GGG....13.7005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GGG....13.7005C"><span id="translatedtitle">The size of plume heterogeneities constrained by Marquesas <span class="hlt">isotopic</span> stripes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauvel, Catherine; Maury, René C.; Blais, Sylvain; Lewin, Eric; Guillou, Hervé; Guille, GéRard; Rossi, Philippe; Gutscher, Marc-André</p> <p>2012-07-01</p> <p>The scale and geometry of chemical and <span class="hlt">isotopic</span> heterogeneities in the source of plumes have important scientific implications on the nature, composition and origin of plumes and on the dynamics of mantle mixing over time. Here, we address these issues through the <span class="hlt">study</span> of Marquesas Islands, one of the Archipelagoes in Polynesia. We present new <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb, Hf <span class="hlt">isotopes</span> as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different <span class="hlt">isotopic</span> compositions. For the entire 5.5 Ma construction period, the northern islands, hereafter called the Ua Huka group, has had systematically higher 87Sr/86Sr and lower 206Pb/204Pb ratios than the southern Fatu Hiva group at any given 143Nd/144Nd value. The shape and curvature of mixing arrays preclude the ambient depleted MORB mantle as one of the mixing end-members. We believe therefore that the entire <span class="hlt">isotopic</span> heterogeneity originates in the plume itself. We suggest that the two Marquesas <span class="hlt">isotopic</span> stripes originate from partial melting of two adjacent filaments contained in small plumes or "plumelets" that came from a large dome structure located deep in the mantle under Polynesia. Low-degree partial melting under Marquesas and other "weak" Polynesian hot spot chains (Pitcairn-Gambier, Austral-Cook, Society) sample small areas of the dome and preserve source heterogeneities. In contrast, more productive hot spots build up large islands such as Big Island in Hawaii or Réunion Island, and the higher degrees of melting blur the <span class="hlt">isotopic</span> variability of the plume source.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=74955&keyword=effects+AND+food+AND+waste&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=66697015&CFTOKEN=56113570','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=74955&keyword=effects+AND+food+AND+waste&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=66697015&CFTOKEN=56113570"><span id="translatedtitle">STABLE <span class="hlt">ISOTOPES</span> IN ECOLOGICAL <span class="hlt">STUDIES</span>: NEW DEVELOPMENTS IN MIXING MODELS</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Stable <span class="hlt">isotopes</span> are increasingly being used as tracers in ecological <span class="hlt">studies</span>. One application uses <span class="hlt">isotopic</span> ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include food sources for animals, water sources for plants, pollution sources...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790017541','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790017541"><span id="translatedtitle"><span class="hlt">Study</span> report on a double <span class="hlt">isotope</span> method of calcium absorption</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1978-01-01</p> <p>Some of the pros and cons of three methods to <span class="hlt">study</span> gastrointestinal calcium absorption are briefly discussed. The methods are: (1) a balance <span class="hlt">study</span>; (2) a single <span class="hlt">isotope</span> method; and (3) a double <span class="hlt">isotope</span> method. A procedure for the double <span class="hlt">isotope</span> method is also included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22407991','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22407991"><span id="translatedtitle">Microturbulence <span class="hlt">study</span> of the <span class="hlt">isotope</span> effect</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bustos, A.; Bañón Navarro, A.; Görler, T.; Jenko, F.</p> <p>2015-01-15</p> <p>The influence of the ion mass on the dynamics of magnetized plasmas is an important challenge in fusion research. The discrepancies between the improvement of the magnetic confinement with the ion mass in tokamak experiments and diffusive turbulent transport predictions have remained unexplained for several decades. We refer to this phenomenon as the <span class="hlt">isotope</span> effect. In this paper, we <span class="hlt">study</span> this effect with gyrokinetic theory using the GENE code. We find several sets of plasma parameters that correspond to low wavenumber turbulence for which the <span class="hlt">isotope</span> effect is present, although the intensity is smaller than the experimental observations. We also relate these results to the zonal flow intensity of the system, which is characterized by the average shear flow rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMDI31A2548T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMDI31A2548T"><span id="translatedtitle">Multi-<span class="hlt">Isotopic</span> evidence from West Eifel Xenoliths</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thiemens, M. M.; Sprung, P.</p> <p>2015-12-01</p> <p>Mantle Xenoliths from the West Eifel intraplate volcanic field of Germany provide insights into the nature and evolution of the regional continental lithospheric mantle. Previous <span class="hlt">isotope</span> <span class="hlt">studies</span> have suggested a primary Paleoproterozoic depletion age, a second partial melting event in the early Cambrian, and a Variscan metasomatic overprint. Textural and <span class="hlt">Sr-Nd</span> <span class="hlt">isotopic</span> observations further suggest two episodes of melt infiltration of early Cretaceous and Quaternary age. We have investigated anhydrous, vein-free lherzolites from this region, focusing on the Dreiser Weiher and Meerfelder Maar localities. Hand separated spinel, olivine, ortho- and clinopryoxene, along with host and bulk rocks were dissolved and purified for Rb-Sr, Sm-Nd, and Lu-Hf analysis on the Cologne/Bonn Neptune MC-ICP-MS. We find an unexpected discontinuity between mineral separates and whole rocks. While the latter have significantly more radiogenic ɛNd and ɛHf, mineral separates imply close-to chondritic compositions. Our Lu-Hf data imply resetting of the Lu-Hf systematic after 200 Ma. Given the vein-free nature of the lherzolites, this appears to date to the second youngest metasomatic episode. We suggest that markedly radiogenic Nd and Hf were introduced during the Quarternary metasomatic episode and most likely reside on grain boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70033815','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70033815"><span id="translatedtitle">GSD-1G and MPI-DING Reference Glasses for In Situ and Bulk <span class="hlt">Isotopic</span> Determination</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jochum, K.P.; Wilson, S.A.; Abouchami, W.; Amini, M.; Chmeleff, J.; Eisenhauer, A.; Hegner, E.; Iaccheri, L.M.; Kieffer, B.; Krause, J.; McDonough, W.F.; Mertz-Kraus, R.; Raczek, I.; Rudnick, R.L.; Scholz, Donna K.; Steinhoefel, G.; Stoll, B.; Stracke, A.; Tonarini, S.; Weis, D.; Weis, U.; Woodhead, J.D.</p> <p>2011-01-01</p> <p>This paper contains the results of an extensive <span class="hlt">isotopic</span> <span class="hlt">study</span> of United States Geological Survey GSD-1G and MPI-DING reference glasses. Thirteen different laboratories were involved using high-precision bulk (TIMS, MC-ICP-MS) and microanalytical (LA-MC-ICP-MS, LA-ICP-MS) techniques. Detailed <span class="hlt">studies</span> were performed to demonstrate the large-scale and small-scale homogeneity of the reference glasses. Together with previously published <span class="hlt">isotopic</span> data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Hf, Pb, Th and U <span class="hlt">isotopes</span> using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD-1G and the MPI-DING glasses are suitable reference materials for microanalytical and bulk analytical purposes. Ce document contient les r??sultats d'une importante ??tude isotopique des verres de r??f??rence USGS GSD-1G et MPI-DING. Treize laboratoires diff??rents ont particip?? au travers de techniques analytiques de haute pr??cision travaillant soit sur ??chantillon total (TIMS, MC-ICP-MS) soit par microanalyse ??in situ?? (LA-MC-ICP-MS, LA-ICP-MS). ?? 2010 The Authors. Geostandards and Geoanalytical Research ?? 2010 International Association of Geoanalysts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.2431I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.2431I"><span id="translatedtitle"><span class="hlt">Isotope</span> pattern deconvolution as rising tool for <span class="hlt">isotope</span> tracer <span class="hlt">studies</span> in environmental research</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas</p> <p>2014-05-01</p> <p>During the last decade stable <span class="hlt">isotope</span> tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' <span class="hlt">isotope</span> tracers caused by the natural variation of <span class="hlt">isotopes</span>, the intentional introduction of 'extrinsic' enriched stable <span class="hlt">isotope</span> tracers into biological systems has gained significant interest. Hereby the induced change in the natural <span class="hlt">isotopic</span> composition of an element allows amongst others for <span class="hlt">studying</span> the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of <span class="hlt">isotope</span> (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some <span class="hlt">isotope</span> systems like the natural Sr <span class="hlt">isotopic</span> system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the <span class="hlt">isotope</span> dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. <span class="hlt">Isotope</span> pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike <span class="hlt">isotope</span> dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the <span class="hlt">isotope</span> pattern in a spiked sample without knowing the quantities of enriched <span class="hlt">isotope</span> tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/83382','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/83382"><span id="translatedtitle">NMR <span class="hlt">studies</span> of <span class="hlt">isotopically</span> labeled RNA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pardi, A.</p> <p>1994-12-01</p> <p>In summary, the ability to generate NMR quantities of {sup 15}N and {sup 13}C-labeled RNAs has led to the development of heteronuclear multi-dimensional NMR techniques for simplifying the resonance assignment and structure determination of RNAs. These methods for synthesizing <span class="hlt">isotopically</span> labeled RNAs are only several years old, and thus there are still relatively few applications of heteronuclear multi-dimensional NMR techniques to RNA. However, given the critical role that RNAs play in cellular function, one can expect to see an increasing number of NMR structural <span class="hlt">studies</span> of biologically active RNAs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.1588K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.1588K"><span id="translatedtitle">Radiogenic <span class="hlt">isotope</span> evidence for transatlantic atmospheric dust transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumar, Ashwini; Abouchami, Wafa; Garrison, Virginia H.; Galer, Stephen J. G.; Andreae, Meinrat O.</p> <p>2013-04-01</p> <p>Early <span class="hlt">studies</span> by Prospero and colleagues [1] have shown that African dust reaches all across the Atlantic and into the Caribbean. It may contribute to fertilizing the Amazon rainforest [2,3,4], in addition to enhancing the ocean biological productivity via delivery of iron, a key nutrient element[5]. Radiogenic <span class="hlt">isotope</span> ratios (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb) are robust tracers of dust sources and can thus provide information on provenance and pathways of dust transport. Here we report <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotope</span> data on atmospheric aerosols, collected in 2008 on quartz filters, from three different locations in Mali (12.6° N, 8.0° W; 555 m a.s.l.), Tobago (11.3° N, 60.5° W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7° N, 64.6° W; 27 m a.s.l.) to investigate the hypothesis of dust transport across the Atlantic. About 2 cm2 of filter were acid-leached in 0.5 N HBr for selective removal of the anthropogenic labile Pb component (leachate) and possibly the fine soluble particle fraction. The remainder of the filter was subsequently dissolved using a mixture of HF and HNO3 acids, and should be representative of the silicate fraction. <span class="hlt">Isotopic</span> compositions were measured by TIMS on a ThermoFisher Triton at MPIC, with Pb <span class="hlt">isotope</span> ratios determined using the triple-spike method. Significant Pb <span class="hlt">isotope</span> differences between leachates and residues were observed. The variability in Pb <span class="hlt">isotopic</span> composition among leachates may be attributed to variable and distinct anthropogenic local Pb sources from Africa and South America [6], however, residues are imprinted by filter blank contribution suggesting to avoid the quartz fiber filter for <span class="hlt">isotopic</span> <span class="hlt">study</span> of aerosols. The Nd and Sr <span class="hlt">isotope</span> ratios of aerosol leachates show similar signatures at all three locations investigated. The nearly identical Nd and Sr <span class="hlt">isotopic</span> compositions in the Mali, Tobago and Virgin islands leachates are comparable to those obtained on samples from the Bodélé depression, Northern Chad [7] and suggest a possible common</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/884796','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/884796"><span id="translatedtitle">Identification of <span class="hlt">isotopically</span> primitive interplanetary dust particles: A NanoSIMS <span class="hlt">isotopic</span> imaging <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Floss, C; Stadermann, F J; Bradley, J P; Dai, Z R; Bajt, S; Graham, G; Lea, A S</p> <p>2005-09-02</p> <p>We have carried out a comprehensive survey of the <span class="hlt">isotopic</span> compositions (H, B, C, N, O, S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. <span class="hlt">Isotopic</span> imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in {sup 15}N, including the largest {sup 15}N enrichments ({approx}1300 {per_thousand}) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in {sup 15}N, leading to average bulk N <span class="hlt">isotopic</span> compositions that are {sup 15}N-enriched in these IDPs. Although C <span class="hlt">isotopic</span> compositions are normal in most of the IDPs, two {sup 15}N-rich N-hotspots have correlated {sup 13}C anomalies. CN{sup -}/C{sup -} ratios suggest that most of the {sup 15}N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H <span class="hlt">isotopic</span> distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N <span class="hlt">isotopic</span> anomalies are not directly correlated, consistent with results from previous <span class="hlt">studies</span>. Oxygen <span class="hlt">isotopic</span> imaging shows the presence of abundant presolar silicate grains in the IDPs. The O <span class="hlt">isotopic</span> compositions of the grains are similar to those found in presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have <span class="hlt">isotopic</span> ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the {sup 17}O and {sup 18}O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N <span class="hlt">isotopic</span> compositions, the IDPs <span class="hlt">studied</span> here can be divided into two groups. One group is characterized as being ''<span class="hlt">isotopically</span> primitive'' and consists of those IDPs that have anomalous bulk N <span class="hlt">isotopic</span> compositions. These</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70018247','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70018247"><span id="translatedtitle">A <span class="hlt">study</span> of REE and Pb, Sr and Nd <span class="hlt">isotopes</span> in garnet-lherzolite xenoliths from Mingxi, Fujian Province</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wankang, H.; Junwen, W.; Basu, A.R.; Tatsumoto, M.</p> <p>1993-01-01</p> <p>The REE and Pb, <span class="hlt">Sr</span>, <span class="hlt">Nd</span> <span class="hlt">isotopes</span> in three xenoliths from limburgite and scoria-breccias, including spinel-lherzolite, spinel-garnet-lherzolite and phlogopite-gamet-lherzolite, were analysed. The REE contents of the xenoliths are 1.3 to 3.3 times those of the chondrites with their REE patterns characterized by weak LREE depletion. The143Nd/144Nd values of whole rocks and minerals range from 0.51306 to 0.51345 with ??Nd=+ 8.2- +15.8,206Pb/204 Pb < 18.673, and207Pb/204Pb < 15.574. All this goes to show that the upper mantle in Mingxi at the depth of 67-82 km is a depleted mantle of MORB type, with87Sr/86 Sr ratios 0.70237-0.70390. In Nd-Sr diagram the data points of whole rocks are all out of the mantle array, implying that the xenoliths from Mingxi have more radiogenic Sr <span class="hlt">isotopes</span> than those of the mantle array. ?? 1993 Institute of Geochemistry, Chinese Academy of Sciences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780057737&hterms=thorium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dthorium','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780057737&hterms=thorium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dthorium"><span id="translatedtitle">Lead <span class="hlt">isotope</span> <span class="hlt">studies</span> of mare basalt 70017</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mattinson, J. M.; Tilton, G. R.; Todt, W.; Chen, J. H.</p> <p>1977-01-01</p> <p>Uranium, thorium, and <span class="hlt">isotopic</span> lead data for components of basalt 70017 are reported, and it is found that the whole rock, pyroxene, and ilmenite points in a concordia diagram plot along a chord intersecting the curve at 3.7 and 4.33 eons. The plagioclase data do not seem to lie on this line. The data for 70017 appear to plot along a distinctly different chord in a concordia diagram than do the data for 75055 and 75035, two other Apollo 17 mare basalts. The lead data are in accord with Sm-Nd results. A 3.7 eon crystallization age for 70017 would be consistent with the same kind of parentless lead that is indicated by previous <span class="hlt">studies</span> of soils and soil breccias from stations at Taurus-Littrow. The Th/U ratio in ilmenite is 2.2, and the concentrations of these two elements are approximately twice those in pyroxene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100003466','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100003466"><span id="translatedtitle">Stable Chlorine <span class="hlt">Isotope</span> <span class="hlt">Study</span>: Application to Early Solar System Materials</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mala,ira. M/; Nyquist, L. E.; Reese, Y.; Shih, C-Y; Fujitani, T.; Okano, O.</p> <p>2010-01-01</p> <p>A significantly large mass fractionation between two stable chlorine <span class="hlt">isotopes</span> is expected during planetary processes In addition, in view of the <span class="hlt">isotopic</span> heterogeneity of other light elements, the chlorine <span class="hlt">isotopes</span> can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine <span class="hlt">isotope</span> <span class="hlt">studies</span> on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the Cl-37/Cl-35 ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For example, almost no differences of Cl <span class="hlt">isotope</span> composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl <span class="hlt">isotope</span> variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl <span class="hlt">isotope</span> analyses are now required to confirm real chlorine <span class="hlt">isotope</span> variations for planetary materials including carbonaceous chondrites [5]. A significantly large mass fractionation between two stable chlorine <span class="hlt">isotopes</span> is expected during planetary processes In addition, in view of the <span class="hlt">isotopic</span> heterogeneity of other light elements, the chlorine <span class="hlt">isotopes</span> can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine <span class="hlt">isotope</span> <span class="hlt">studies</span> on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.183...94S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.183...94S"><span id="translatedtitle">He, Ne and Ar <span class="hlt">isotope</span> signatures of mid-ocean ridge basalts and their implications for upper mantle structure: A case <span class="hlt">study</span> from the Mid-Atlantic Ridge at 4-12°S</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroncik, Nicole A.; Niedermann, Samuel</p> <p>2016-06-01</p> <p>The geochemical structure of the upper mantle in general and its noble gas <span class="hlt">isotopic</span> structure in particular have been the subject of countless <span class="hlt">studies</span>, as both provide important insights into mantle dynamic processes and are essential for the formulation of mantle geodynamic models. This contribution presents a noble gas <span class="hlt">study</span> of basaltic glasses derived from the Mid-Atlantic Ridge (MAR) between 4° and 12°S, an area well known for its high degree of lithophile <span class="hlt">isotope</span> heterogeneity and its anomalous crustal thickness. The <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb and Hf <span class="hlt">isotopic</span> systematics along this segment of the MAR range from strongly depleted (i.e. more depleted than N-MORB) to highly enriched. Different concepts have been proposed to explain the observed <span class="hlt">isotopic</span> signatures. Here we show that the high degree of heterogeneity is not confined to the <span class="hlt">isotopes</span> of the lithophile elements, but is also shown by the noble gas <span class="hlt">isotopes</span> and noble gas interelement ratios, such as 3He/22NeM or 4He/40Ar∗. Helium <span class="hlt">isotopic</span> ratios (3He/4He), 21Ne/22Neextra and 40Ar/36Ar range from 7.34 ± 0.06 to 9.38 ± 0.08 RA, from 0.039 ± 0.020 to 0.075 ± 0.007, and from 346 ± 5 to 37,400 ± 1300, respectively. However, the majority of the Ne <span class="hlt">isotope</span> data are clearly aligned along a single mixing line in the Ne three-<span class="hlt">isotope</span> diagram, represented by the equation 20Ne/22Ne = 70.5 × 21Ne/22Ne + 7.782, with a slope distinctly less than that of the MORB line. This indicates that the strongly depleted material is characterised by a significantly more nucleogenic Ne <span class="hlt">isotopic</span> composition than the normal depleted mantle. We show, based on covariations between 3He/4He and 21Ne/22Neextra with 206Pb/204Pb and 178Hf/177Hf that the strongly depleted material erupted at this MAR segment was most likely produced by an ancient melting event. This implies that <span class="hlt">isotopic</span> heterogeneities in the upper mantle are not solely caused by the injection of enriched materials from deep-seated mantle plumes or by crustal recycling but may</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993CoMP..114..452B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993CoMP..114..452B"><span id="translatedtitle">Evaluating crustal contamination in continental basalts: the <span class="hlt">isotopic</span> composition of the Picture Gorge Basalt of the Columbia River Basalt Group</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandon, Alan D.; Hooper, Peter R.; Goles, Gordon G.; Lambert, Richard St J.</p> <p>1993-09-01</p> <p>Crustal contamination of basalts located in the western United States has been generally under-emphasized, and much of their <span class="hlt">isotopic</span> variation has been ascribed to multiple and heterogeneous mantle sources. Basalts of the Miocene Columbia River Basalt Group in the Pacific Northwest have passed through crust ranging from Precambrian to Tertiary in age. These flows are voluminous, homogenous, and underwent rapid effusion, all of which are disadvantages for crustal contamination while en route to the surface. The Picture Gorge Basalt of the Columbia River Basalt Group erupted through Paleozoic and Mesozoic oceanic accreted terranes in central Oregon, and earlier <span class="hlt">studies</span> on these basalts provided no <span class="hlt">isotopic</span> evidence for crustal contamination. New <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb, and O <span class="hlt">isotopic</span> data presented here indicate that the <span class="hlt">isotopic</span> variation of the Picture Gorge Basalt is very small, 87Sr/86Sr=0.70307 0.70371, ɛNd=+7.7-+4.8, δ18O=+5.6±6.1, and 206Pb/204Pb=18.80 18.91. Evaluation of the Picture Gorge compositional variation supports a model where two <span class="hlt">isotopic</span> components contributed to Picture Gorge Basalt genesis. The first component (C1) is reflected by low 87Sr/86Sr, high ɛNd, and nonradiogenic Pb <span class="hlt">isotopic</span> compositions. Basalts with C1 <span class="hlt">isotopic</span> compositions have large MgO, Ni, and Cr contents and mantle-like δ18O=+5.6. C1 basalts have enrichments in Ba coupled with depletions in Nb and Ta. These characteristics are best explained by derivation from a depleted mantle source which has undergone a recent enrichment by fluids coming from a subducted slab. This C1 mantle component is prevalent throughout the Pacific Northwest. The second <span class="hlt">isotopic</span> component has higher 87Sr/ 86Sr and δ18O, lower ɛNd, and more radiogenic Pb <span class="hlt">isotopic</span> compositions than C1. There is a correlation in the Picture Gorge data of <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotopes</span> with differentiation indicators such as decreasing Mg#, and increasing K2O/TiO2, Ba, Ba/Zr, Rb/Sr, La/Sm, and La/Yb. Phase equilibrium and mineralogical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17175008','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17175008"><span id="translatedtitle">REE characteristics and Pb, Sr and Nd <span class="hlt">isotopic</span> compositions of steel plant emissions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Geagea, M Lahd; Stille, P; Millet, M; Perrone, Th</p> <p>2007-02-01</p> <p>A comprehensive Pb-<span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> and REE tracer <span class="hlt">study</span> of atmospheric trace metal pollution by a steel plant situated to the north of the urban communities of Strasbourg (France) and Kehl (Germany) has been performed using tree barks as biomonitors. The 206Pb/207Pb and 208Pb/207Pb <span class="hlt">isotopic</span> ratios of the steel plant's filter dust are similar to values found in dust of waste incinerators. The 87Sr/86Sr ratio is similar to present-day ratios of Phanerozoic or Precambrian granitic rocks. The 143Nd/144Nd <span class="hlt">isotopic</span> composition is very low and corresponds to an (Nd) value of -17.5. Such a low value is characteristic of old Precambrian granitic rocks and banded iron formations. Thus, this low (Nd) value might point to the origin of the iron necessary for the steel production. The fact, that this <span class="hlt">isotopic</span> composition does not occur in crustal rocks of Western Central Europe makes the Nd <span class="hlt">isotope</span> ratio a powerful tool to trace steel plants atmospheric emissions. The rare earth element (REE) distribution pattern of the steel plant's filter dust shows very specific fractionations like La and Nd enrichments which are traceable in tree barks over a distance of 4 km. The Pb, Sr and Nd <span class="hlt">isotope</span> ratios not only enable the steel plant's emissions to be traced in a north-easterly direction, along the principal wind pathway but also enables the interference of this emission at 4 km NE from the steel plant with another atmospheric component originating from the Strasbourg Rhine harbour to be identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983AREPS..11..371L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983AREPS..11..371L"><span id="translatedtitle">Terrestrial inert gases - <span class="hlt">Isotope</span> tracer <span class="hlt">studies</span> and clues to primordial components in the mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lupton, J. E.</p> <p></p> <p>The use of He-3/He-4 measurements for characterizing terrestrial materials and tracing natural-system processes is surveyed. Terrestrial He is classified according to its He-3/He-4 ratio, expressed as R/R-A where R-A is the He-3/He-4 ratio of atmospheric He, 1.4 x 10 to the -6th; radiogenic He typical of continental rocks has R/R-A of 0.01-0.1, while mantle He, typical of midoceanic ridge basalts (MORB) and other geothermal environments and attributed to gas entrapment during the earth's formation, has R/R-A of 5-30. Determinations of R/R-A for MORB and for samples from hot spots, from Tristan da Cunha, and from subduction zones are compared with <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Ar, Ne, and Xe data and shown to support a two-layer (depleted/fertile) model of the mantle, with mixing processes accounting for tectonic variations in R/R-A. The use of He-3 as a tracer for mapping ocean circulation patterns, <span class="hlt">studying</span> ridge-crest tectonic and hydrothermal processes, and geothermal and hydrologic prospecting is described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/842020','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/842020"><span id="translatedtitle"><span class="hlt">Isotope</span> constraints on the involvement of fluids in the San Andreas Fault System, California</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pili, E.; Kennedy, B.M.; Conrad, S.M.; Gratier, J.-P.; Poitrasson, F.</p> <p>1998-07-01</p> <p>Fluids are suspected to play a major role in earthquake mechanics, especially in the case of the weak San Andreas Fault (SAF). Models developed to explain the weakness of the fault are similar but rely on different fluid sources. A recent <span class="hlt">study</span> of groundwaters associated with the SAF has provided evidence for a geopressured mantle fluid source (Kennedy et al., 1997). We present here an <span class="hlt">isotope</span> <span class="hlt">study</span> comparing deformation zones (gouges, breccias, fault veins, slickensides, cataclasites), and vein fillings with their hosts and the fluids associated with these materials, as sampled by fluid inclusions. We are investigating ca. 250 samples from over 20 localities along the San Andreas and adjacent faults from South San Francisco to East Los Angeles. Samples from the exhumed San Gabriel Fault, a deeper equivalent of the SAF, are included as well as samples from the Santa Ynez Fault, another former strand of the SAF embedded in Miocene limestones. All the major lithologies (granites, gneisses, sandstones, limestones, marbles and serpentinites) have been sampled for <span class="hlt">isotope</span> analyses of C, O, H, He, Ne, Ar, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013E%26PSL.380..112A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013E%26PSL.380..112A"><span id="translatedtitle">Geochemical and <span class="hlt">isotopic</span> characterization of the Bodélé Depression dust source and implications for transatlantic dust transport to the Amazon Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abouchami, Wafa; Näthe, Kerstin; Kumar, Ashwini; Galer, Stephen J. G.; Jochum, Klaus Peter; Williams, Earle; Horbe, Adriana M. C.; Rosa, João W. C.; Balsam, William; Adams, David; Mezger, Klaus; Andreae, Meinrat O.</p> <p>2013-10-01</p> <p>The Bodélé Depression (Chad) in the central Sahara/Sahel region of Northern Africa is the most important source of mineral dust to the atmosphere globally. The Bodélé Depression is purportedly the largest source of Saharan dust reaching the Amazon Basin by transatlantic transport. Here, we have undertaken a comprehensive <span class="hlt">study</span> of surface sediments from the Bodélé Depression and dust deposits (Chad, Niger) in order to characterize geochemically and <span class="hlt">isotopically</span> (<span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopes</span>) this dust source, and evaluate its importance in present and past African dust records. We similarly analyzed sedimentary deposits from the Amazonian lowlands in order to assess postulated accumulation of African mineral dust in the Amazon Basin, as well as its possible impact in fertilizing the Amazon rainforest. Our results identify distinct sources of different ages and provenance in the Bodélé Depression versus the Amazon Basin, effectively ruling out an origin for the Amazonian deposits, such as the Belterra Clay Layer, by long-term deposition of Bodélé Depression material. Similarly, no evidence for contributions from other potential source areas is provided by existing <span class="hlt">isotope</span> data (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>) on Saharan dusts. Instead, the composition of these Amazonian deposits is entirely consistent with derivation from in-situ weathering and erosion of the Precambrian Amazonian craton, with little, if any, Andean contribution. In the Amazon Basin, the mass accumulation rate of eolian dust is only around one-third of the vertical erosion rate in shield areas, suggesting that Saharan dust is "consumed" by tropical weathering, contributing nutrients and stimulating plant growth, but never accumulates as such in the Amazon Basin. The chemical and <span class="hlt">isotope</span> compositions found in the Bodélé Depression are varied at the local scale, and have contrasting signatures in the "silica-rich" dry lake-bed sediments and in the "calcium-rich" mixed diatomites and surrounding sand material. This</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012E%26PSL.337..164R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012E%26PSL.337..164R"><span id="translatedtitle">Re-Os <span class="hlt">isotope</span> and highly siderophile element systematics of the Paraná continental flood basalts (Brazil)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rocha-Júnior, Eduardo R. V.; Puchtel, Igor S.; Marques, Leila S.; Walker, Richard J.; Machado, Fábio B.; Nardy, Antônio J. R.; Babinski, Marly; Figueiredo, Ana M. G.</p> <p>2012-07-01</p> <p>Basalts of the Paraná continental flood basalt (PCFB) province erupted through dominantly Proterozoic continental crust during the Cretaceous. In order to examine the mantle source(s) of this major flood basalt province, we <span class="hlt">studied</span> Os, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotope</span> systematics, and highly siderophile element (HSE) abundances in tholeiitic basalts that were carefully chosen to show the minimal effects of crustal contamination. These basalts define a precise Re-Os isochron with an age of 131.6±2.3 Ma and an initial 187Os/188Os of 0.1295±0.0018 (γ187Os=+2.7±1.4). This initial Os <span class="hlt">isotopic</span> composition is considerably more radiogenic than estimates of the contemporary Depleted Mantle (DM). The fact that the Re-Os data define a well constrained isochron with an age similar to 40Ar/39Ar age determinations, despite generally low Os concentrations, is consistent with closed-system behavior for the HSE. Neodymium, Sr, and Pb <span class="hlt">isotopic</span> data suggest that the mantle source of the basalts had been variably hybridized by melts derived from enriched mantle components. To account for the combined Os, Nd, Sr, and Pb <span class="hlt">isotopic</span> characteristics of these rocks, we propose that the primary melts formed from metasomatized asthenospheric mantle (represented by arc-mantle peridotite) that underwent mixing with two enriched components, EM-I and EM-II. The different enriched components are reflected in minor <span class="hlt">isotopic</span> differences between basalts from southern and northern portions of the province. The Tristan da Cunha hotspot has been previously suggested to be the cause of the Parana continental flood basalt magmatism. However, present-day Tristan da Cunha lavas have much higher 187Os/188Os <span class="hlt">isotopic</span> compositions than the source of the PCFB. These data, together with other <span class="hlt">isotopic</span> and elemental data, preclude making a definitive linkage between the Tristan plume and the PCFB.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.V31C0948G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.V31C0948G"><span id="translatedtitle">Sr-Pb <span class="hlt">isotopic</span> <span class="hlt">studies</span> of primitive and near-primitive basaltic magmas, Garibaldi volcanic belt, northern Cascadia subduction system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Green, N. L.; Sinha, A. K.</p> <p>2003-12-01</p> <p>The northern Cascadia subduction system is intimately associated with aseismic subduction of extremely young and presumably `hot' oceanic lithosphere beneath northwestern Washington and southwestern British Columbia. Sr and Pb <span class="hlt">isotopic</span> analyses are presented for primitive and near-primitive (>6.0 wt. % MgO) basalts from a southeast-northwest transect along the Garibaldi volcanic belt (GVB), which overlies subducted oceanic lithosphere that decreases in age from ca. 22 m.y. below Glacier Peak at its southern end to about 13 m.y. beneath the northernmost eruptive centers in the Mosaic (Meager Mountain) and Salal Glacier-Bridge River areas. The basaltic rocks have initial 87Sr/86Sr ratios of 0.70317-0.70426, with minimum observed values in individual lava suites decreasing northward. Values of Pb <span class="hlt">isotopic</span> ratios for GVB basaltic suites range from 18.22 to 18.97 for 206Pb/204Pb, from 15.51 to 15.59 for 207Pb/204Pb, and from 37.73 to 38.49 for 208Pb/204Pb. Sr <span class="hlt">isotopic</span> compositions, unsupported by lava Rb contents, show positive correlations with Cs/Rb, La/Nb, Ba/La, Ba/Nb, Ba/Ta, B/La, B/Zr, <span class="hlt">Sr/Nd</span>, and primitive mantle normalized Sr/P; and negative correlations with high field strength elements (HFSE: Nb, and Ta), FeO and other transition metals (Co and Zn), Ce/Pb,Cr/Ni, Sm/Yb, Ta/Yb, Hf/Yb, K/Ba, K/Sr, and La/Yb. Moderate to strong correlations between 87Sr/86Sr and ratios involving fluid-mobile and less-fluid-mobile elements are compatible with decreased slab input northward along the volcanic front as the subducted plate becomes hotter. The Pb <span class="hlt">isotopic</span> compositions exhibit only limited variations when examined against position along the volcanic arc, but show uniform to extremely weak positive correlations of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb with 87Sr/86Sr, Ba/La, <span class="hlt">Sr/Nd</span>, Ba/Nb, Zr/Nb, Mg-Number and SiO2; and similarly weak negative correlation of Ce/Pb with 206Pb/204Pb and 207Pb/204Pb. The <span class="hlt">isotopic</span> data suggest that GVB basaltic magmas have experienced with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050166979','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050166979"><span id="translatedtitle">Li <span class="hlt">Isotope</span> <span class="hlt">Studies</span> of Olivine in Mantle Xenoliths by SIMS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bell, D. R.; Hervig, R. L.; Buseck, P. R.</p> <p>2005-01-01</p> <p>Variations in the ratio of the stable <span class="hlt">isotopes</span> of Li are a potentially powerful tracer of processes in planetary and nebular environments [1]. Large differences in the 7Li/6Li ratio between the terrestrial upper mantle and various crustal materials make Li <span class="hlt">isotope</span> composition a potentially powerful tracer of crustal recycling processes on Earth [2]. Recent SIMS <span class="hlt">studies</span> of terrestrial mantle and Martian meteorite samples report intra-mineral Li <span class="hlt">isotope</span> zoning [3-5]. Substantial Li <span class="hlt">isotope</span> heterogeneity also exists within and between the components of chondritic meteorites [6,7]. Experimental <span class="hlt">studies</span> of Li diffusion suggest the potential for rapid <span class="hlt">isotope</span> exchange at elevated temperatures [8]. Large variations in 7Li, exceeding the range of unaltered basalts, occur in terrestrial mantle-derived xenoliths from individual localities [9]. The origins of these variations are not fully understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B21A0459M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B21A0459M"><span id="translatedtitle"><span class="hlt">Isotopic</span> Forced-Diffusion Technique for Soil Respiration <span class="hlt">Studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McArthur, G.; Nickerson, N. R.; Egan, J.; Risk, D. A.; Jacobson, G. A.; Cunningham, K. L.; Saad, N.</p> <p>2013-12-01</p> <p><span class="hlt">Isotopic</span> ratio measurements of soil-respired CO2 can provide a wealth of insight into soil-level carbon-cycle processes that is not available using bulk CO2 emission measurements alone. Soil contains substantial amounts of carbon, and can contribute CO2 to the atmosphere through various respiration pathways. <span class="hlt">Isotopic</span> analysis can distinguish autotrophic root and rhizosphere respiration from heterotrophic respiration due to the catabolism of soil organic matter (SOM). Because of this, researchers have shifted their efforts toward the use of natural abundance and tracer <span class="hlt">isotopic</span> techniques in ecosystem respiration <span class="hlt">studies</span>. However, recent experimental and theoretical evidence indicates that these traditional techniques yield biased estimates of the soil <span class="hlt">isotopic</span> flux, largely owing to disturbances to the soil's natural diffusive regime. To help eliminate these biases, we have developed a new technique called <span class="hlt">Isotopic</span> Forced-Diffusion (IsoFD). The <span class="hlt">Isotopic</span> Forced-Diffusion technique integrates a Forced Diffusion dynamic chamber with a cavity ringdown spectrometer measuring d13C-CO2, which are operated together as an integrated system. The system produces real-time, high temporal resolution <span class="hlt">isotopic</span> soil efflux data. Here, we will present the theory behind this technique, present laboratory data demonstrating the accuracy and precision of the technique in controlled environments and finally field data from two campaigns, showing the ability of the Iso-FD chamber to detect natural diurnal changes in <span class="hlt">isotopic</span> signature as well as differentiate sources in C3-C4 transitional systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007E%26PSL.259..134I&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007E%26PSL.259..134I&link_type=ABSTRACT"><span id="translatedtitle">Ancient recycled crust beneath the Ontong Java Plateau: <span class="hlt">Isotopic</span> evidence from the garnet clinopyroxenite xenoliths, Malaita, Solomon Islands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ishikawa, Akira; Kuritani, Takeshi; Makishima, Akio; Nakamura, Eizo</p> <p>2007-07-01</p> <p>We present a <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Hf and Pb <span class="hlt">isotope</span> investigation of a set of garnet clinopyroxenite xenoliths from Malaita, Solomon Islands in order to constrain crustal recycling in the Pacific mantle. Geological, thermobarometric and petrochemical evidence from previous <span class="hlt">studies</span> strongly support an origin as a series of high-pressure (> 3 GPa) melting residues of basaltic material incorporated in peridotite, which was derived from Pacific convective mantle related to the Ontong Java Plateau magmatism. The present <span class="hlt">study</span> reveals <span class="hlt">isotopic</span> variations in the pyroxenites that are best explained by different extents of chemical reaction with ambient peridotite in the context of a melting of composite source mantle. <span class="hlt">Isotopic</span> compositions of bimineralic garnet clinopyroxenites affected by ambient peridotite fall within the oceanic basalt array, similar to those of Ontong Java Plateau lavas. In contrast, a quartz-garnet clinopyroxenite, whose major element compositions remain intact, has lower 206Pb/ 204Pb- 143Nd/ 144Nd and higher 87Sr/ 86Sr- 207Pb/ 204Pb ratios than most oceanic basalts. These <span class="hlt">isotopic</span> signatures show some affinity with proposed recycled sources such as the so-called EM-1 or DUPAL types. Constraints from major and trace element characteristics of the quartz-garnet clinopyroxenite, the large extent of Hf-Nd <span class="hlt">isotopic</span> decoupling and the good coincidence of Pb <span class="hlt">isotopes</span> to the Stacey-Kramers curve, all indicate that pollution of southern Pacific mantle occurred by the subduction or delamination of Neoproterozoic granulitic lower crust (0.5-1 Ga). This crustal recycling could have taken place around the suture of Rodinia supercontinent, a part of which resurfaced during mantle upwelling responsible for creating the Cretaceous Ontong Java Plateau.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011E%26PSL.302..154H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011E%26PSL.302..154H"><span id="translatedtitle">Geochemical portray of the Pacific Ridge: New <span class="hlt">isotopic</span> data and statistical techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamelin, Cédric; Dosso, Laure; Hanan, Barry B.; Moreira, Manuel; Kositsky, Andrew P.; Thomas, Marion Y.</p> <p>2011-02-01</p> <p>Samples collected during the PACANTARCTIC 2 cruise fill a sampling gap from 53° to 41° S along the Pacific Antarctic Ridge (PAR). Analysis of <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb, Hf, and He <span class="hlt">isotope</span> compositions of these new samples is shown together with published data from 66°S to 53°S and from the EPR. The recent advance in analytical mass spectrometry techniques generates a spectacular increase in the number of multidimensional <span class="hlt">isotopic</span> data for oceanic basalts. Working with such multidimensional datasets generates a new approach for the data interpretation, preferably based on statistical analysis techniques. Principal Component Analysis (PCA) is a powerful mathematical tool to <span class="hlt">study</span> this type of datasets. The purpose of PCA is to reduce the number of dimensions by keeping only those characteristics that contribute most to its variance. Using this technique, it becomes possible to have a statistical picture of the geochemical variations along the entire Pacific Ridge from 70°S to 10°S. The incomplete sampling of the ridge led previously to the identification of a large-scale division of the south Pacific mantle at the latitude of Easter Island. The PCA method applied here to the completed dataset reveals a different geochemical profile. Along the Pacific Ridge, a large-scale bell-shaped variation with an extremum at about 38°S of latitude is interpreted as a progressive change in the geochemical characteristics of the depleted matrix of the mantle. This Pacific <span class="hlt">Isotopic</span> Bump (PIB) is also noticeable in the He <span class="hlt">isotopic</span> ratio along-axis variation. The linear correlation observed between He and heavy radiogenic <span class="hlt">isotopes</span>, together with the result of the PCA calculation, suggests that the large-scale variation is unrelated to the plume-ridge interactions in the area and should rather be attributed to the partial melting of a marble-cake assemblage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930000943','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930000943"><span id="translatedtitle">Sudbury project (University of Muenster-Ontario Geological Survey): <span class="hlt">Isotope</span> systematics support the impact origin</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deutsch, A.; Buhl, D.; Brockmeyer, P.; Lakomy, R.; Flucks, M.</p> <p>1992-01-01</p> <p>Within the framework of the Sudbury project a considerable number of <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> analyses were carried out on petrographically well-defined samples of different breccia units. Together with <span class="hlt">isotope</span> data from the literature these data are reviewed under the aspect of a self-consistent impact model. The crucial point of this model is that the Sudbury Igneous Complex (SIC) is interpreted as a differentiated impact melt sheet without any need for an endogenic 'magmatic' component such as 'impact-triggered' magmatism or 'partial' impact melting of the crust and mixing with a mantle-derived magma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034726','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034726"><span id="translatedtitle">Fundamental <span class="hlt">studies</span> on kinetic <span class="hlt">isotope</span> effect (KIE) of hydrogen <span class="hlt">isotope</span> fractionation in natural gas systems</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ni, Y.; Ma, Q.; Ellis, G.S.; Dai, J.; Katz, B.; Zhang, S.; Tang, Y.</p> <p>2011-01-01</p> <p>Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen <span class="hlt">isotope</span> fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen <span class="hlt">isotopic</span> substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic <span class="hlt">isotope</span> effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen <span class="hlt">isotope</span> fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen <span class="hlt">isotope</span> values. Calculated gas maturity values determined by the proposed mathematical model using ??D values in ethane from several basins in the world are in close agreement with similar predictions based on the ??13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic <span class="hlt">isotopic</span> models do not agree as closely. It is possible that ??D values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this <span class="hlt">study</span> is quite preliminary, the results demonstrate that kinetic <span class="hlt">isotope</span> fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that ??D values in ethane might be more suitable for modeling than comparable values in methane and propane. ?? 2011 Elsevier Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.V51D..08B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.V51D..08B"><span id="translatedtitle">Ultra-depleted <span class="hlt">isotopic</span> compositions in fertile asthenosphere-derived peridotites: constraints on the composition of the upper mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Byerly, B. L.; Lassiter, J. C.</p> <p>2012-12-01</p> <p>Recent <span class="hlt">studies</span> of abyssal peridotites (AP) and OIB xenoliths have reported refractory, <span class="hlt">isotopically</span> ultra-depleted domains within the convecting upper mantle with Nd- and Hf-<span class="hlt">isotope</span> compositions that extend far beyond the MORB field. These results have important implications regarding the average composition of the depleted upper mantle and the genetic relationship between MORB and AP. However, the abundance of ultra-depleted domains in the mantle is unclear. In addition, recent melt extraction processes at mid-ocean ridges make it difficult to evaluate the compositions of ultra-depleted domains prior to exhumation and thus evaluate their role in melt generation. To better constrain the abundance and composition of typical convecting upper mantle, we examined a suite of spinel peridotite xenoliths from the central Rio Grande Rift (RGR) where most of the preexisting lithosphere has been convectively removed and replaced with depleted upper mantle. Seismic tomography indicates that the lithosphere beneath the RGR has been substantially removed (Gao, 2004), and geochemical evidence supports this. Two distinct populations of xenoliths are observed from Elephant Butte, central RGR. One population, interpreted to derive from residual Proterozoic lithospheric mantle, is refractory (bulk Al2O3 <2.3 wt.%), LREE- and LILE-enriched, has enriched <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotopic</span> compositions and along with xenoliths from the Eastern Colorado Plateau define a strong Lu/Hf-176Hf/177Hf "pseudo-isochron" with an apparent age of ~1.6 Ga. In contrast, the majority of the RGR xenoliths have fertile major element compositions (bulk Al2O3 ~ 4.0 wt %), low spinel Cr# (~10), and LREE-depleted trace element patterns, and overlap with composition estimates for the depleted mantle (Workman & Hart, 2005). We interpret these xenoliths to reflect recent replacement of the pre-existing lithosphere with material from the convecting upper mantle. The fertile xenoliths have cpx <span class="hlt">Sr</span>-, <span class="hlt">Nd</span>-, and Hf-<span class="hlt">isotope</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5000590','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5000590"><span id="translatedtitle">Embryotoxicity of stable <span class="hlt">isotopes</span> and use of stable <span class="hlt">isotopes</span> in <span class="hlt">studies</span> of teratogenetic mechanisms</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Spielmann, H.; Nau, H.</p> <p>1986-07-01</p> <p>Experiments on teratogenic effects of stable <span class="hlt">isotopes</span> from our own and other laboratories are evaluated. In the first series of investigations, the enrichment of the stable <span class="hlt">isotope</span> /sup 13/C derived from U-/sup 13/C-glucose was <span class="hlt">studied</span> in mouse embryos at various stages of development, including limb buds in organ culture. Preimplantation mouse embryos incubated in vitro in /sup 13/C-enriched medium for 48 hours showed normal development during subsequent differentiation in vitro and also in vivo after embryo transfer to faster mothers. These embryos were 15% to 20% enriched in /sup 13/C. Administration of U-13-C-glucose to pregnant mice during organogenesis led to an increase of the absolute /sup 13/C content of the embryo for several days after the end of <span class="hlt">isotope</span> administration, whereas the enrichment in maternal tissue decreased. No alterations of embryonic development were detected due to stable <span class="hlt">isotope</span> enrichment. Development of cultured mouse limb buds was unaffected by incubation with 82 mol% U-/sup 13/C-glucose as judged from morphologic and biochemical criteria. The second part of the article describes the value of deuterium-labeled drugs as probes into the mechanism of activation of teratogenic metabolites. A comparison of the pharmacokinetics as well as the teratogenicity between cyclophosphamide and some specific deuterium-labeled analogues showed that the <span class="hlt">isotope</span> effect observed can be related to a particular metabolic pathway crucial for teratogenic activation by this drug.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5033317','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5033317"><span id="translatedtitle">Preliminary <span class="hlt">study</span>: <span class="hlt">isotopic</span> safeguards techniques (IST) LMFBR fuel cycles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Persiani, P. J.; Kroc, T. K.</p> <p>1980-06-01</p> <p>This memorandum presents the preliminary results of the effort to investigate the applicability of <span class="hlt">isotope</span> correlation techniques (ICT), formulated for the LWR system, to the LMFBR fuel cycle. The detailed <span class="hlt">isotopic</span> compositional changes with burnup developed for the CRBR was utilized as the reference case. This differs from the usual LMFBR design <span class="hlt">studies</span> in that the core uranium is natural uranium rather than depleted. Nevertheless, the general <span class="hlt">isotopic</span> behavior should not differ significantly and does allow an initial insight into the expected behavior of <span class="hlt">isotopic</span> correlations for the LMFBR power systems such as: the U.K. PFR and reprocessing plant; the French Phenix and Superphenix; and the US reference conceptual design <span class="hlt">studies</span> (CDS) of homogeneous and heterogeneous LMFBR systems as they are developed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015630','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015630"><span id="translatedtitle">Carbon <span class="hlt">isotope</span> systematics of a mantle "hotspot": a comparison of Loihi Seamount and MORB glasses</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Exley, R.A.; Mattey, D.P.; Clague, D.A.; Pillinger, C.T.</p> <p>1986-01-01</p> <p>The carbon <span class="hlt">isotope</span> geochemistry of glasses from Loihi Seamount has been compared with that of MORB glasses. Stepped heating shows two carbon components in both sample suites: (1) <span class="hlt">isotopically</span> light carbon (avg. ??13C = -26.3???) released 600??C, regarded as indigenous. The high-temperature component in MORB samples varied from 52 to 169 ppm C, average ??13C = -6.6???, consistent with previous <span class="hlt">studies</span> (overall MORD average ??13C = -6.4 ?? 0.9???), and new results for Indian Ocean glasses are similar to Atlantic and Pacific Ocean samples. Carbon release profiles produced by stepped heating may be typical of locality, but there are no significant differences in ??13C values between MORB samples from different areas. Lower yields (17-110 ppm C) correlated with depth in the Loihi samples suggest that they are partially degassed. This degassing has not affected ??13C values significantly (avg. -5.8???). Loihi tholeiites have higher ??13C (avg. -5.6???) than the alkali basalts (avg. -7.1???). Carbon abundances correlate well with He concentration data. Comparison of the ??13C values with trace element and He, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotope</span> data from the literature suggests that the Loihi samples with highest ??13C have high 3He/4He and possibly the least depleted 143Nd/144Nd and 87Sr/86Sr. The carbon <span class="hlt">isotope</span> data are consistent with previous models for Loihi involving several mantle sources, lithospheric contamination, and mixing. The slightly higher ??13C of Loihi tholeiites suggests that the undegassed "plume" component manifested by high 3He/4He values might have ??13C about 1??? higher than the MORB average. ?? 1986.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/924676','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/924676"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of Contaminant Transport at the Hanford Site, Washington.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Christensen, John N.; Conrad, Mark E.; DePaolo, Donald J.; Dresel, P. Evan</p> <p>2007-11-01</p> <p>Processes of fluid flow and chemical transport through the vadose zone can be characterized through the <span class="hlt">isotopic</span> systematics of natural soils, minerals, pore fluids and groundwater. In this contribution, we first review our research using measured <span class="hlt">isotopic</span> variations, due both to natural and site related processes, of the elements H, O, N, Sr and U, to <span class="hlt">study</span> the interconnection between vadose zone and groundwater contamination at the Hanford Site in south-central Washington. We follow this brief review with a presentation of new data pertaining to vadose zone and groundwater contamination in the WMA T-TX-TY vicinity. Uranium (U) <span class="hlt">isotopic</span> data for the C3832 core (WMA TX) indicates the involvement of processed natural U fuel, and links the observed U contamination to the nearby single shelled tank TX-104. The data also precludes contamination from an early 1970’s TX-107 leak. In the case of the C4104 core (WMA T), the U <span class="hlt">isotopic</span> data indicates a mixture of processed natural and enriched U fuels consistent with the major leak from T-106 in 1973. Uranium and Strontium <span class="hlt">isotopic</span> data for the cores also provides direct evidence for chemical interaction between high-pH waste fluid and sediment. <span class="hlt">Isotopic</span> data for groundwater nitrate contamination in the vicinity of WMA-T strongly suggests high-level tank waste (most likely from T-106) as the source of very high 99Tc concentrations recently observed at the NE corner of WMAT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003TrGeo...5..319K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003TrGeo...5..319K"><span id="translatedtitle">Stable <span class="hlt">Isotope</span> Applications in Hydrologic <span class="hlt">Studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kendall, C.; Doctor, D. H.</p> <p>2003-12-01</p> <p>The topic of stream flow generation has received considerable attention over the last two decades, first in response to concern about "acid rain" and more recently in response to the increasingly serious contamination of surface and shallow groundwaters by anthropogenic contaminants. Many sensitive, low-alkalinity streams in North America and Europe are already acidified (see Chapter 9.10). Still more streams that are not yet chronically acidic may undergo acidic episodes in response to large rainstorms and/or spring snowmelt. These acidic events can seriously damage local ecosystems. Future climate changes may exacerbate the situation by affecting biogeochemical controls on the transport of water, nutrients, and other materials from land to freshwater ecosystems.New awareness of the potential danger to water supplies posed by the use of agricultural chemicals and urban industrial development has also focused attention on the nature of rainfall-runoff and recharge processes and the mobility of various solutes, especially nitrate and pesticides, in shallow systems. Dumping and spills of other potentially toxic materials are also of concern because these chemicals may eventually reach streams and other public water supplies. A better understanding of hydrologic flow paths and solute sources is required to determine the potential impact of contaminants on water supplies, develop management practices to preserve water quality, and devise remediation plans for sites that are already polluted.<span class="hlt">Isotope</span> tracers have been extremely useful in providing new insights into hydrologic processes, because they integrate small-scale variability to give an effective indication of catchment-scale processes. The main purpose of this chapter is to provide an overview of recent research into the use of naturally occurring stable <span class="hlt">isotopes</span> to track the movement of water and solutes in hydrological systems where the waters are relatively fresh: soils, surface waters, and shallow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70011413','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70011413"><span id="translatedtitle">Rb-Sr, Sm-Nd, K-Ca, O, and H <span class="hlt">isotopic</span> <span class="hlt">study</span> of Cretaceous-Tertiary boundary sediments, Caravaca, Spain: evidence for an oceanic impact site</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>DePaolo, D.J.; Kyte, F.T.; Marshall, B.D.; O'Neil, J.R.; Smit, J.</p> <p>1983-01-01</p> <p><span class="hlt">Isotopic</span> ratios and trace element abundances were measured on samples of Ir-enriched clay at the Cretaceous-Tertiary boundary, and in carbonate and marl from 5 cm below and 3 cm above the boundary. Samples were leached with acetic acid to remove carbonate, and with hydrochloric acid. Leachates and residues were measured. The <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, O and H <span class="hlt">isotopic</span> compositions of the boundary clay residues are distinct from those of the stratigraphically neighboring materials. The data indicate that most of the clay material was derived from a terrestrial source with relatively low 87Sr/86Sr and high 143Nd/144Nd ratios. The ??18O data suggest that the detritus has been modified by submarine weathering. K-Ca and Rb-Sr systematics, as well as O <span class="hlt">isotope</span> ratios of K-feldspar spherules within the boundary clay, suggest that they are predominantly authigenic and may have formed after the time of deposition. However, Sm-Nd and Rb-Sr <span class="hlt">isotopic</span> data indicate that the spherules contain relict material that provides information on the nature of the original detritus. The <span class="hlt">isotopic</span> evidence for foreign terrestrial detritus in the boundary clay, the low rare earth element concentrations and high Ni concentration, support the hypothesis of a terminal Cretaceous asteroidal impact that produced a global layer of fallout. The data are most easily explained if the impact site was on oceanic crust rather than continental crust, and if a substantial fraction of the fallout was derived from relatively deep within the lithosphere (>3 km). This would probably require a single large impactor. ?? 1983.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26747521','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26747521"><span id="translatedtitle">Nitrogen and Oxygen <span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of the Marine Nitrogen Cycle.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Casciotti, Karen L</p> <p>2016-01-01</p> <p>The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable <span class="hlt">isotopes</span> of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-<span class="hlt">isotope</span> <span class="hlt">studies</span> applied at regional to global scales and their incorporation into oceanic biogeochemical models. These <span class="hlt">studies</span> represent significant new advances in the use of <span class="hlt">isotopic</span> measurements to understand the modern nitrogen cycle, with implications for the <span class="hlt">study</span> of past ocean productivity, oxygenation, and nutrient status.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ARMS....8..379C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ARMS....8..379C"><span id="translatedtitle">Nitrogen and Oxygen <span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of the Marine Nitrogen Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Casciotti, Karen L.</p> <p>2016-01-01</p> <p>The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable <span class="hlt">isotopes</span> of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-<span class="hlt">isotope</span> <span class="hlt">studies</span> applied at regional to global scales and their incorporation into oceanic biogeochemical models. These <span class="hlt">studies</span> represent significant new advances in the use of <span class="hlt">isotopic</span> measurements to understand the modern nitrogen cycle, with implications for the <span class="hlt">study</span> of past ocean productivity, oxygenation, and nutrient status.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26747521','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26747521"><span id="translatedtitle">Nitrogen and Oxygen <span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of the Marine Nitrogen Cycle.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Casciotti, Karen L</p> <p>2016-01-01</p> <p>The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable <span class="hlt">isotopes</span> of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-<span class="hlt">isotope</span> <span class="hlt">studies</span> applied at regional to global scales and their incorporation into oceanic biogeochemical models. These <span class="hlt">studies</span> represent significant new advances in the use of <span class="hlt">isotopic</span> measurements to understand the modern nitrogen cycle, with implications for the <span class="hlt">study</span> of past ocean productivity, oxygenation, and nutrient status. PMID:26747521</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18323089','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18323089"><span id="translatedtitle">Tracing of industrial aerosol sources in an urban environment using Pb, Sr, and Nd <span class="hlt">isotopes</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Geagea, Majdi Lahd; Stille, Peter; Gauthier-Lafaye, François; Millet, Maurice</p> <p>2008-02-01</p> <p>A comprehensive Pb-<span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> tracer <span class="hlt">study</span> of atmospheric trace metal pollution has been performed in the urban environment of Strasbourg-Kehl. Filter dust of the principal pollutant sources (waste incinerators, thermal power plant and steel plant) and soot of car and ship exhausts have been analyzed. In addition tree barks (as biomonitors) and PM10 have been analyzed to trace and determine the distribution of the pollution in the environment. The industrial sources have highly variable epsilonNd values (-9.7 and -12.5 for incinerators and -17.5 for steel plant). Much higher epsilonNd values have been found for soot of car exhausts (-6 and -6.9). These high values make the Nd <span class="hlt">isotope</span> system a powerful tool for the discrimination of traffic emissions but especially for the identification of diesel derived particles in the urban environment. The 206Pb/207Pb <span class="hlt">isotope</span> ratios of gasoline are low (1.089) compared to diesel soot (1.159). The 26Pb/207Pb ratios of 1.151-1.152 for the steel plant and 1.152 for the solid waste incinerator are close to the Pb <span class="hlt">isotope</span> ratio of diesel. The 87Sr/ 8Sr <span class="hlt">isotope</span> ratios of the principal industrial sources vary significantly: 0.7095 for the domestic solid waste incinerator, 0.709 for the steel plant, and 0.7087 for car exhaust soot. PM10 aerosols collected in the urban center of Strasbourg show the influence of the pollutant sources at 3-7 km distance from the center. Most of the aerosols Pb <span class="hlt">isotopic</span> compositions suggest Pb admixtures from at least three sources: a natural background and in function of the wind direction the domestic waste incinerator (S-wind) or the steel plant and the chemical waste incinerator (NE-wind). The traffic contribution can only be estimated with help of Nd <span class="hlt">isotopes</span>. Therefore the clear identification of different pollutant sources in the urban environment is only possible by combining the three different <span class="hlt">isotope</span> systems and is based on the fact that significant differences exist between the Pb, Sr, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A21O..02A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A21O..02A"><span id="translatedtitle">Can Transport of Saharan Dust Explain Extensive Clay Deposits in the Amazon Basin? A Test Using Radiogenic <span class="hlt">Isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andreae, M. O.; Abouchami, W.; Näthe, K.; Kumar, A.; Galer, S. J.; Jochum, K. P.; Williams, E.; Horbe, A. M.; Rosa, J. W.; Adams, D. K.; Balsam, W. R.</p> <p>2012-12-01</p> <p>The Bodélé Depression, located in the Southern Sahara, is a huge source of atmospheric dust and thus an important element in biogeochemical cycles and the radiative budget of Earth's atmosphere. Previous <span class="hlt">studies</span> have shown that Saharan dust transport across the Atlantic acts as an important source of mineral nutrients to the Amazon rainforest. The Belterra Clay, which outcrops extensively across the Amazon Basin in Brazil, has been proposed to result from dry deposition of African dusts. We have investigated this hypothesis by measuring the radiogenic <span class="hlt">isotopic</span> composition (<span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb) of a suite of samples from the Belterra Clay, the Bodélé Depression, dusts deposits collected at various locations along the airmass transport trajectory, as well as loess from the Cape Verde Islands. Radiogenic <span class="hlt">isotope</span> systems are powerful tracers of provenance and can be used to fingerprint dust sources and atmospheric transport patterns. Our results identify distinct <span class="hlt">isotopic</span> signatures in the Belterra Clay samples and the African sources. The Belterra Clay display radiogenic Sr and Pb <span class="hlt">isotope</span> ratios associated with non-radiogenic Nd <span class="hlt">isotope</span> signatures. In contrast, Bodélé samples and dusts deposits show lower Pb <span class="hlt">isotope</span> ratios, variable 87Sr/86Sr, and relatively homogeneous Nd <span class="hlt">isotopic</span> compositions, albeit more radiogenic than those of the Belterra Clay. Our data show unambiguously that the Belterra Clay is not derived from African dust deposition, nor from the Andean chain, as originally suggested by W. Sombroek. Rather, <span class="hlt">isotopic</span> compositions and Nd model ages are consistent with simple mixing of Archean and younger Proterozoic terranes within the Amazon Basin as a result of weathering and erosion under humid tropical conditions. Whether Saharan dusts contribute to the fertilization in the Amazon Basin cannot be ruled out, however, since the African dust <span class="hlt">isotopic</span> signature is expected to be entirely overprinted by local sources. Radiogenic <span class="hlt">isotope</span> data obtained on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70030333','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70030333"><span id="translatedtitle">Ammonium transport and reaction in contaminated groundwater: Application of <span class="hlt">isotope</span> tracers and <span class="hlt">isotope</span> fractionation <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Böhlke, J.K.; Smith, R.L.; Miller, D.N.</p> <p>2006-01-01</p> <p>Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this <span class="hlt">study</span>, processes affecting NH4+ movement in a treated wastewater plume were <span class="hlt">studied</span> by a combination of techniques including large-scale monitoring of NH4+ distribution; <span class="hlt">isotopic</span> analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial <span class="hlt">isotope</span> fractionation) and sorption (no <span class="hlt">isotope</span> fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ <span class="hlt">isotopic</span> tracers and fractionation <span class="hlt">studies</span> provided critical information about processes affecting NH4+ movement and N speciation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012APS..APRD12001F&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012APS..APRD12001F&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Study</span> of neutron rich carbon <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fallon, Paul</p> <p>2012-03-01</p> <p>Electric quadrupole (E2) matrix elements are important quantities in nuclear structure. In particular they are sensitive to nuclear deformation, the decoupling of proton and neutron degrees of freedom, and are often affected by small components of the nuclear wave function. Neutron-rich carbon <span class="hlt">isotopes</span> have attracted a great deal of attention recently, both experimentally and theoretically, with regards to the question of spatially extended (halo-like) and decoupled valence neutrons. For example, 19C and the drip-line nucleus 22C are proposed to have ground-state neutron halo structures. Electric quadrupole transition rates in 16C 18C and 20C are among the lowest found throughout the nuclear chart and this fact has been cited by some as evidence for a reduced coupling between the valence neutrons and the core nucleons. In this talk I will present the results from our experiments to measure the transition rates in 16,18,20C and discuss the evidence for a ``decoupling'' of valence neutrons from the core that goes beyond the usual shell model approach. Data will be compared to shell model and no-core (ab-initio) shell model calculations with NN and NN+NNN interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ARPC...57..625S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ARPC...57..625S"><span id="translatedtitle">Dynamical <span class="hlt">Studies</span> of the Ozone <span class="hlt">Isotope</span> Effect: a Status Report</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schinke, R.; Grebenshchikov, S. Yu.; Ivanov, M. V.; Fleurat-Lessard, P.</p> <p>2006-05-01</p> <p>Dynamical <span class="hlt">studies</span> of the recombination of O and O2 to form ozone are reviewed. The focus is the intriguing <span class="hlt">isotope</span> dependence of the recombination rate coefficient as observed by Mauersberger and coworkers in the last decade. The key quantity for understanding of this dependence appears to be the difference of zero-point energies of the two fragmentation channels to which excited ozone can dissociate, i.e., X + YZ ← XYZ* → XY + Z, where X, Y, and Z stand for the three <span class="hlt">isotopes</span> of oxygen. Besides the <span class="hlt">isotope</span> dependence, the variation of the recombination rate coefficient with pressure and temperature is also addressed. Despite the numerous approaches of recent years, the recombination of ozone is far from being satisfactorily explained; there are still several essential questions to be solved by detailed theoretical analysis. We mainly discuss—and critically assess—the results of our own investigations of the ozone kinetics. The work of other research groups is also evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Litho.170..224G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Litho.170..224G"><span id="translatedtitle">A composite, <span class="hlt">isotopically</span>-depleted peridotite and enriched pyroxenite source for Madeira magmas: Insights from olivine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gurenko, Andrey A.; Geldmacher, Jörg; Hoernle, Kaj A.; Sobolev, Alexander V.</p> <p>2013-06-01</p> <p>The Madeira and Canary island/seamount chains represent two adjacent hotspot tracks in the eastern North Atlantic, which were derived from mixed peridotite-pyroxenite mantle sources. They possess systematically different <span class="hlt">Sr-Nd</span>-Pb, Os and Hf <span class="hlt">isotope</span> signatures, implying mixing of DMM-, HIMU- and EM-type components from different mantle lithologies. The lithological nature of these postulated mantle endmembers (e.g., if formed by peridotite, pyroxenite and/or eclogite) is still a subject of debate. We <span class="hlt">studied</span> the chemical composition of olivine phenocrysts (focusing on their Ni, Mn and Ca concentrations) from the lavas covering the entire volcanic history of the Madeira Archipelago (~ 0-5 Ma). We demonstrate that Ni × FeO/MgO and Mn/FeO ratios and Ca-concentrations of olivine correlate with <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopic</span> compositions of their host lavas. The amounts of peridotite- and pyroxenite-derived melt fractions in the parental Madeira magmas were inferred from olivine compositions and independently confirmed by modeling of two-component source melting using trace elements. Our calculations demonstrate that the amount of recycled crust (= eclogite) in the Madeira magma source varies but does not exceed ~ 10%. Strong linear relationships between chemical composition of olivine and radiogenic <span class="hlt">isotopes</span> of the host lavas allow us to determine the <span class="hlt">isotopic</span> composition of peridotite and pyroxenite endmembers of the Madeira hotspot. The peridotite endmember has a highly depleted <span class="hlt">isotopic</span> composition 87Sr/86Sr = 0.7022-0.7026, 143Nd/144Nd = 0.5132-0.5135, 206Pb/204Pb = 17.4-18.6, 207Pb/204Pb = 15.4-15.49, and 208Pb/204Pb = 36.8-38.2, whereas the pyroxenite endmember has an enriched composition 87Sr/86Sr = 0.7031-0.7035, 143Nd/144Nd = 0.5127-0.5130, 206Pb/204Pb = 19.9-21.3, 207Pb/204Pb = 15.59-15.69, and 208Pb/204Pb = 39.6-41.2. Our new data confirm the existence of recycled (pyroxenitic) lithology in the Madeira magma source that was previously interpreted to represent</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011GGG....12.AC14H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011GGG....12.AC14H&link_type=ABSTRACT"><span id="translatedtitle">Insights into the Galápagos plume from uranium-series <span class="hlt">isotopes</span> of recently erupted basalts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Handley, Heather K.; Turner, Simon; Berlo, Kim; Beier, Christoph; Saal, Alberto E.</p> <p>2011-09-01</p> <p>Uranium-series <span class="hlt">isotopes</span> (238U-230Th-226Ra-210Pb), major element, trace element, and <span class="hlt">Sr-Nd</span> <span class="hlt">isotopic</span> data are presented for recent (<60 years old) Galápagos archipelago basalts. Volcanic rocks from all centers <span class="hlt">studied</span> (Fernandina, Cerro Azul, Sierra Negra, and Wolf Volcano) display 230Th excesses (4%-15%) and steep rare earth element (REE) patterns indicative of residual garnet during partial melting of their mantle source. Rare earth element modeling suggests that only a few percent of garnet is involved. Correlations between (238U/232Th), radiogenic <span class="hlt">isotopes</span> and Nb/Zr ratio suggest that the U/Th ratio of these Galápagos volcanic rocks is primarily controlled by geochemical source variations and not fractionation during partial melting. The lowest (230Th/238U) ratio is not observed at Fernandina (the supposed center of the plume) but at the more geochemically "depleted" Wolf Volcano, further to the north. Small radium excesses are observed for all samples with (226Ra/230Th) ranging from 1.107 to 1.614. The 226Ra-230Th disequilibria do not correlate with other uranium-series parent-daughter nuclide pairs or geochemical data, suggesting modification at shallow levels on timescales relevant to the half-life of 226Ra (1600 years). The combination of 226Ra and 210Pb excesses is inconsistent with interaction of magma with cumulate material unless decoupling of 210Pb (or an intermediate daughter, such as 222Rn) occurs prior to modification of Ra-Th disequilibria. An intriguing correlation of (210Pb/226Ra)0 with Nb/Zr and radiogenic <span class="hlt">isotopes</span> requires further investigation but suggests possible control via magmatic degassing and accumulation that may somehow be related to source heterogeneities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6967820','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6967820"><span id="translatedtitle">Helium- and lead-<span class="hlt">isotope</span> geochemistry of oceanic volcanic rocks from the East Pacific and South Atlantic. Doctoral thesis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Graham, D.W.</p> <p>1987-01-01</p> <p>Glassy basalts erupted at young Pacific seamounts and along the mid-ocean ridge in the South Atlantic, and volcanic rocks from the island of St. Helena were <span class="hlt">studied</span> for He and Pb <span class="hlt">isotopes</span>. (U+TH)/He ages of seamount alkali basalts were determined from the <span class="hlt">isotope</span> disequilibrium of (3)He/(4)He between He trapped in vesicles and that dissolved in the glass phase. The method allows alkalic lavas to be dated in the age range of 103 to 106 years. Tholclites at the EPR seamounts have He, Pb, Sr and Nd <span class="hlt">isotope</span> compositions indistinguishable from MORB, while associated alkali basalts show more radiogenic signatures. The low (3)He/(4)He in the vesicles of alkali basalts (1.2-2.6 RA), their low helium concentrations, and systematic variations with extent of differentiation suggest that magmatic processes influence (3)He/(4)He in these alkalic lavas. Pb-<span class="hlt">Sr-Nd</span> <span class="hlt">isotopes</span> at Shimada seamount (17 deg N, 117 deg W) indicate the presence of enriched mantle beneath the East Pacific which resembles that beneath Samoa. Low (3)He/(4)He (4-5 RA) appears to be an inherent characteristic of the component. Much of the South Atlantic ridge axis displays (3)He/(4)He lower than normal MORB, and is apparently contaminated by off-axis hotspots. He-Pb systematics along the ridge suggest that (3)He/(4)He at St. Helena is less than MORB, consistent with values measured by in vacuo crushing of olivine and pyroxene in St. Helena rocks (approx. 5.8 RA).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/899557','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/899557"><span id="translatedtitle">The Enriched Background <span class="hlt">Isotope</span> <span class="hlt">Study</span> (EBIS)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hanson, Paul J.; Trumbore, Susan; Swanston, Chris; Torn, Margaret; Jastrow, Julie; Parton, William A; Post, Wilfred M.; Froberg, Mats J; Hainsworth, Laura J; Kleber, Markus; Kramer, Christiane; Matamala-Paradeda, Roser; Garten, Jr, Charles T.</p> <p>2007-02-05</p> <p>A unique, large release of radiocarbon occurred near the Oak Ridge Reservation (ORR), Oak Ridge, TN in July/August 1999. Measurements of 14C in tree ring cellulose throughout the ORR area demonstrate that the 1999 release was unprecedented in its uptake by vegetation. We are taking advantage of the whole-ecosystem <span class="hlt">isotopic</span> label generated by this release to address five outstanding issues in the terrestrial carbon cycle: (1) partitioning of soil respiration between autotrophic and heterotrophic sources, and quantification of that partitioning seasonally and inter-annually, (2) partitioning of heterotrophic respiration sources between above-ground litter decomposition and below-ground root detritus decomposition, (3) identification of pathways leading from leaf and root detritus to long-term stabilization of soil organic matter, including the role of soil fauna, (4) the role of dissolved organic carbon (DOC) transport in distributing carbon within the soil profile, and, (5) the longevity and turnover time of fine roots. The first four issues are being addressed through a reciprocal litter transplant experiment set up at four sites on the ORR encompassing two soil types and two levels of 14C exposure in 1999. The fifth issue, longevity and turnover of fine roots, is being addressed by tracing the radiocarbon label through the fine root pool over time. With a combination of incubation, soil surface chamber and soil CO2 profiles, and continuous measurements of soil temperature and moisture controls, we are tracking changes in soil respiration partitioning over several years. The nature and source of organic matter pools that reside in soils for years to decades are being tracked with differently labeled root and surface litter, and experiments to exclude soil fauna have been initiated to elucidate their role in vertical transport. Periodic sampling of soils and soil solutions and the use of inert tracers, allow us to investigate the chemical nature and form of DOC and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V43C4903B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V43C4903B"><span id="translatedtitle"><span class="hlt">Isotopic</span> Disequilibrium and High-Crystallinity Magma Ascent: Clues to the Temporal Restriction of Proterozoic Anorthosites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bybee, G. M.</p> <p>2014-12-01</p> <p>Many Proterozoic anorthosite massifs show crustal <span class="hlt">isotopic</span> signatures that have fuelled debate regarding the source (mantle vs. lower crust) of these temporally restricted magmas. The models advocating a mantle derivation for these rocks suggest that lower crustal assimilation plays an important role in developing the <span class="hlt">isotopic</span> signature of the massifs, but no evidence exists to support this. We make use of <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopic</span> compositions of anorthosites from the Mealy Mountains Intrusive Suite (MMIS), the Nain Plutonic Suite (NPS) and the Rogaland Anorthosite Province (RAP), their internal mineral phases and comagmatic, high-pressure pyroxene megacrysts, which represent samples from various stages of the polybaric ascent of the magmas, to probe the origin of the crustal <span class="hlt">isotopic</span> signatures and assess the importance of differentiation at lower crustal depths. <span class="hlt">Study</span> of the MMIS and NPS is instructive as each is intruded into crust of significantly different age and <span class="hlt">isotopic</span> composition. We observe varying degrees of internal <span class="hlt">isotopic</span> disequilibrium, enforcing the notion that the nature of the crustal assimilant has a profound influence on the chemical signature of the magmas (Fig. 1). We also find unexpected patterns of internal <span class="hlt">isotopic</span> disequilibrium, such as <span class="hlt">isotopically</span> depleted orthopyroxene relative to plagioclase (Fig. 1), which suggests that anorthosite petrogenesis is not a "simple" case of progressive crustal contamination during polybaric magma ascent, but is more likely to involve significant differentiation and solidification at lower crust depths. The 100 m.y. magmatic timescales observed in these anorthosite systems may be caused by significant magmatic differentiation at Moho/lower crustal levels, as well as formation in long-lived arc environments. These long-lived magmatic timescales contrast with recent observations suggesting that the duration of magma ascent from the Moho to surface in arc environments is on the order of months to years. Such</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6152S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6152S"><span id="translatedtitle">Noble gas <span class="hlt">isotope</span> signals of mid-ocean ridge basalts and their implication for upper mantle structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroncik, Nicole A.; Niedermann, Samuel</p> <p>2016-04-01</p> <p>The geochemical structure of the upper mantle in general and its noble gas <span class="hlt">isotopic</span> structure in particular have been the subject of countless <span class="hlt">studies</span>, as both provide important insights into mantle dynamic processes and are essential for the formulation of mantle geodynamic models. This contribution presents a noble gas <span class="hlt">study</span> of basaltic glasses derived from the Mid-Atlantic-Ridge (MAR) between 4 and 12° S, an area well known for its high degree of lithophile <span class="hlt">isotope</span> heterogeneity and exhibiting anomalous crustal thickness. The <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb and Hf isotopies along this segment of the MAR range from ultra-depleted (more than NMORB) to highly enriched, and different concepts have been proposed to explain the observed <span class="hlt">isotopic</span> signatures. Here we show that the high degree of heterogeneity is not confined to the <span class="hlt">isotopes</span> of the lithophile elements, but is also shown by the noble gas <span class="hlt">isotopes</span> and noble gas interelement ratios, such as e.g. 3He/22NeM or 4He/40Ar*. 3He/4He, 21Ne/22Neextra and 40Ar/36Ar range from 7.3 to 9.3 RA, from 0.05 to 0.08, and from 346 to 37,400, respectively. Nevertheless, the majority of the Ne <span class="hlt">isotope</span> data are clearly aligned along a single mixing line in the Ne-three-<span class="hlt">isotope</span> diagram, represented by the equation 20Ne/22Ne=70.5 x 21Ne/22Ne + 7.782, with a slope distinctly different from that of the MORB line, indicating that the ultra-depleted material is characterised by a significantly more nucleogenic 21Ne/22Ne isotopy than the normal depleted mantle. We show, based on covariations between 3He/4He and 21Ne/22Neextra with 206Pb/204Pb and 178Hf/177Hf, that the ultra-depleted material erupted at this MAR segment was most likely produced by an ancient, deep melting event. This implies that <span class="hlt">isotopic</span> heterogeneities in the upper mantle are not solely caused by the injection of enriched materials from deep-seated mantle plumes or by crustal recycling but may also be due to differences in the depth and degree of melting of upper mantle material within</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005EPJD...36..249W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005EPJD...36..249W"><span id="translatedtitle">Hyperfine structure and <span class="hlt">isotope</span> shift <span class="hlt">study</span> in singly ionized lead</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wąsowicz, T. J.; Drozdowski, R.; Kwela, J.</p> <p>2005-12-01</p> <p>Hyperfine structure and <span class="hlt">isotope</span> shifts in five optical transitions: 424.5 nm (6s^25f ^2textrm{F}_{7/2} 6s^26d^2 textrm{D}_{5/2}), 537.2 nm (6s^25f ^2textrm{F}_{7/2} 6s6p^2 ^4textrm{P}_{5/2}), 554.5 nm (6s^27d ^2textrm{D}_{5/2} 6s^27p ^2textrm{P}_{3/2}), 560.9 nm (6s^27p^2 textrm{P}_{3/2} 6s^27s ^2textrm{S}_{1/2}) and 666.0 nm (6s^27p ^2textrm{P}_{1/2} 6s^27s ^2textrm{S}_{1/2}) of Pb II have been measured. As a light source the discharge tube was used. The hyperfine structure measurements were performed using metallic <span class="hlt">isotope</span> 207Pb. For <span class="hlt">isotope</span> shifts measurements natural lead was used. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. The hyperfine structure observations yielded the splitting constants A for seven levels of Pb II. The <span class="hlt">isotope</span> shift <span class="hlt">studies</span> enabled to separate the mass and the field shifts and to determine values of changes of the mean square nuclear charge radii.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5477505','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5477505"><span id="translatedtitle">Venous obstruction in permanent pacemaker patients: an <span class="hlt">isotopic</span> <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pauletti, M.; Di Ricco, G.; Solfanelli, S.; Marini, C.; Contini, C.; Giuntini, C.</p> <p>1981-01-01</p> <p><span class="hlt">Isotope</span> venography was used to <span class="hlt">study</span> the venous circulation proximal to the superior vena cava in two groups of pacemaker patients, one with a single endocavitary electrode and the other with multiple pacing catheters. A control group of patients without pacemakers was also <span class="hlt">studied</span>. Numerous abnormalities were found, especially in the group with multiple electrodes. These findings suggest that venous obstruction is a common complication of endocardial pacing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032429','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032429"><span id="translatedtitle"><span class="hlt">Isotopically</span> modified nanoparticles for enhanced detection in bioaccumulation <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Misra, S.K.; Dybowska, A.; Berhanu, D.; Croteau, M.-N.; Luoma, S.N.; Boccaccini, A.R.; Valsami-Jones, E.</p> <p>2012-01-01</p> <p>This work presents results on synthesis of <span class="hlt">isotopically</span> enriched (99% 65Cu) copper oxide nanoparticles and its application in ecotoxicological <span class="hlt">studies</span>. 65CuO nanoparticles were synthesized as spheres (7 nm) and rods (7 ?? 40 nm). Significant differences were observed between the reactivity and dissolution of spherical and rod shaped nanoparticles. The extreme sensitivity of the stable <span class="hlt">isotope</span> tracing technique developed in this <span class="hlt">study</span> allowed determining Cu uptake at exposure concentrations equivalent to background Cu concentrations in freshwater systems (0.2-30 ??g/L). Without a tracer, detection of newly accumulated Cu was impossible, even at exposure concentrations surpassing some of the most contaminated water systems (>1 mg/L). ?? 2011 American Chemical Society.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JVGR..304...24A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JVGR..304...24A"><span id="translatedtitle"><span class="hlt">Isotopic</span> microanalysis sheds light on the magmatic endmembers feeding volcanic eruptions: The Astroni 6 case <span class="hlt">study</span> (Campi Flegrei, Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arienzo, I.; D'Antonio, M.; Di Renzo, V.; Tonarini, S.; Minolfi, G.; Orsi, G.; Carandente, A.; Belviso, P.; Civetta, L.</p> <p>2015-10-01</p> <p> caldera feeding system in the past 5 ka, the previously recognized Astroni 6 component. However, diopside crystals in Astroni 6 are characterized by even lower 87Sr/86Sr, in the range of 0.7060-0.7068 and by the highest 143Nd/144Nd ratios measured in the products of Astroni activity. These diopsides may represent another common magmatic component, as they have been found in most of the Phlegrean Volcanic District products emplaced over the past 75 ka. These diopsides, crystallized in a mantle-derived mafic magma, were entrapped by the Astroni 6 magma during ascent, before it mingled/mixed with the more differentiated and enriched in radiogenic Sr resident magma, thus attaining an intermediate <span class="hlt">Sr-Nd</span> <span class="hlt">isotopic</span> fingerprint. These results have an important outcome on the understanding of the volcano behavior, as renewed activity can be triggered by the arrival of fresh magma in the feeding system that would mingle/mix with the resident magma. Such an event may be able to start an unrest phase at the volcano that could last for years or decades, perhaps culminating in a new eruption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6788265','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6788265"><span id="translatedtitle">Probe <span class="hlt">studies</span> of hydrogen <span class="hlt">isotopes</span> in PLT, PDX, and TMX</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wampler, W.R.</p> <p>1982-01-01</p> <p>Recent <span class="hlt">studies</span> of hydrogen <span class="hlt">isotopes</span> incident on solid probes exposed to discharges in PLT, PDX and TMX are described. These experiments used nuclear reaction analysis to measure retained amounts of deuterium, SIMS depth profiling and a new technique based on the resistance change in carbon films caused by energetic particle bombardment. Methods are discussed whereby the energy and flux of the hydrogen incident on the samples can be determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15556172','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15556172"><span id="translatedtitle">Applications of C and N stable <span class="hlt">isotopes</span> to ecological and environmental <span class="hlt">studies</span> in seagrass ecosystems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lepoint, Gilles; Dauby, Patrick; Gobert, Sylvie</p> <p>2004-12-01</p> <p>Stable <span class="hlt">isotopes</span> of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental <span class="hlt">studies</span>. Here, we examine some applications of stable <span class="hlt">isotopes</span> as ecological integrators or tracers in seagrass ecosystem <span class="hlt">studies</span>. We focus on both the use of natural <span class="hlt">isotope</span> abundance as food web integrators or environmental tracers and on the use of stable <span class="hlt">isotopes</span> as experimental tools. As ecosystem integrators, stable <span class="hlt">isotopes</span> have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable <span class="hlt">isotopes</span> have proven their utility in sewage impact measuring and mapping. However, to make such environmental <span class="hlt">studies</span> more comprehensible, future works on understanding of basic reasons for variations of N and C stable <span class="hlt">isotopes</span> in seagrasses should be encouraged. At least, as experimental tracers, stable <span class="hlt">isotopes</span> allow the <span class="hlt">study</span> of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem. PMID:15556172</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=155445&keyword=Uruguay&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=68446604&CFTOKEN=69081236','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=155445&keyword=Uruguay&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=68446604&CFTOKEN=69081236"><span id="translatedtitle">STABLE <span class="hlt">ISOTOPES</span> IN ECOLOGICAL <span class="hlt">STUDIES</span>: NEW DEVELOPMENTS IN MIXING MODELS (URUGUAY)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Stable <span class="hlt">isotopes</span> are increasingly being used as tracers in ecological <span class="hlt">studies</span>. One application uses <span class="hlt">isotopic</span> ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include pollution sources for air or water bodies, food sources for animals, ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=155446&keyword=solutions+AND+mixtures&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=70522446&CFTOKEN=19535960','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=155446&keyword=solutions+AND+mixtures&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=70522446&CFTOKEN=19535960"><span id="translatedtitle">STABLE <span class="hlt">ISOTOPES</span> IN ECOLOGICAL <span class="hlt">STUDIES</span>: NEW DEVELOPMENTS IN MIXING MODELS (BRAZIL)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Stable <span class="hlt">isotopes</span> are increasingly being used as tracers in ecological <span class="hlt">studies</span>. One application uses <span class="hlt">isotopic</span> ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include pollution sources for air or water bodies, food sources for animals, ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990032215&hterms=hydroxide+calcium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dhydroxide%2Bcalcium','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990032215&hterms=hydroxide+calcium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dhydroxide%2Bcalcium"><span id="translatedtitle">Mars Molecular and <span class="hlt">Isotopic</span> Analysis Research <span class="hlt">Study</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Manning, Heidi L. K.</p> <p>1998-01-01</p> <p>Recently, the Martian atmosphere and surface constituents have become of great interest. The Viking in situ gas chromatograph mass spectrometer experiment contributed greatly to our knowledge of the composition of the Martian atmosphere. However, important questions remain such as the abundance of water on Mars. The Viking experiment employed solid reagents to enhance their carbon measurements. Techniques of chemical conversion using simple solid reagents have advanced considerably in the past 20 years. In this investigation we researched the advancements in techniques to reversibly adsorb and desorb water and focused on the techniques potentially useful for the temperatures and pressures on the Martian surface. During the granting period from June 15, 1998 to August 14, 1998, a literature <span class="hlt">study</span> of the material appropriate for use in a chemical conversion device and the availability of these materials were undertaken. The focus of this investigation was searching for methods and materials potentially useful in enhancing the measurements of water. Three different methods were considered for the means to extract water from a given gas sample. These methods included adsorption in a desiccant, adsorption on a clean metal surface, and adsorption in a carbon molecular sieve or zeolite. Each method was evaluated with feasibility and reversibility in mind. By far the simplest and perhaps cheapest way to remove water from a gaseous sample is by means of a bulk desiccant. Desiccants are commercially available from many companies including those that supply chemicals. The main feature of a desiccant is its ability to rapidly bind or absorb water from the atmosphere. Calcium chloride, for example, is frequently incorporated into drying tubes by organic chemists when reactions require the absence of water. Other desiccants include sodium hydroxide, calcium hydride, and commercial products such as Drierite, available from Aldrich Chemical. The disadvantage to most desiccants is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850024876','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850024876"><span id="translatedtitle"><span class="hlt">Isotopic</span> Biogeochemistry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hayes, J. M.</p> <p>1985-01-01</p> <p>An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon <span class="hlt">isotopic</span> records; <span class="hlt">isotopic</span> <span class="hlt">studies</span> of banded iron formations; <span class="hlt">isotope</span> effects in microbial systems; <span class="hlt">studies</span> of organic compounds in ancient sediments; and development in <span class="hlt">isotopic</span> geochemistry and analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009E%26PSL.277...91S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009E%26PSL.277...91S"><span id="translatedtitle">Helium <span class="hlt">isotopes</span> in early Iceland plume picrites: Constraints on the composition of high 3He/ 4He mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Starkey, Natalie A.; Stuart, Finlay M.; Ellam, Robert M.; Fitton, J. Godfrey; Basu, Sudeshna; Larsen, Lotte M.</p> <p>2009-01-01</p> <p>A detailed <span class="hlt">study</span> of the geochemistry of a new suite of early Iceland plume picrites shows that extremely high 3He/ 4He ratios (up to 50 Ra) are found in picrites from Baffin Island and West Greenland. High 3He/ 4He picrites display a wide range in 87Sr/ 86Sr (0.70288-0.70403), 143Nd/ 144Nd (0.51288-0.51308) and incompatible trace element ratios (e.g. La/Sm n = 0.5-1.6). These overlap the complete range of compositions of mid-ocean ridge basalts and most northern hemisphere ocean island basalts, including Iceland. Crustal contamination modelling in which high-grade Proterozoic crustal basement rocks for the region are mixed with a depleted parent cannot account for the trend displayed by the Baffin Island and West Greenland picrites. This rules out the possibility that the incompatible trace element, Sr and Nd <span class="hlt">isotope</span> range of the high 3He/ 4He picrites is due to crustal contamination. The compositional range at high 3He/ 4He is also inconsistent with derivation from a primordial-He-rich reservoir that is a residue of ancient mantle depletion. This implies that the composition of the high 3He/ 4He mantle cannot be determined simply by extrapolating ocean island basalt He-<span class="hlt">Sr-Nd</span>-Pb-Os <span class="hlt">isotope</span> data. The apparent decoupling of He from trace element and lithophile radiogenic <span class="hlt">isotope</span> tracers is difficult to attain by simple mixing of a high-[He], high 3He/ 4He reservoir with various depleted and enriched He-poor mantle reservoirs. The possibility that primordial He has diffused into a reservoir with a composition typical of convecting upper mantle cannot be ruled out. If so, the process must have occurred after the development of existing mantle heterogeneity, and requires the existence of a deep, primordial He-rich reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2463K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2463K"><span id="translatedtitle">Detrital zircons (U-Pb and Lu-Hf) and host hemipelagic sediments (Pb-<span class="hlt">Sr-Nd</span>-Os) from the Polar Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kapitonov, Igor; Belyatsky, Boris; Petrov, Eugeny; Sergeev, Sergey</p> <p>2015-04-01</p> <p>We <span class="hlt">studied</span> deep-sea sediments from 6 sampling sites on the steep slopes of seamounts that accumulate during the last one million years. The goal of the <span class="hlt">study</span> - to characterize the bedrock, which are coming to the surface from the overlying deposits for most of these steep slopes and weathering give talus deposits accumulating at the foot of the slopes.. The result proved to be similar enough for heavy fraction of all sediment columns spaced along the Alpha-Mendeleev Ridge on a 450 km. This suggest provenance similarity, which can be achieved either by erosion of the same rocks composing this ridge or by continental origin of material. We conducted control sampling of deep-water pelagic sediments in several remote places and held various positions with respect to the morphological ocean structure: on the flatten top surface of the deep-water ridge, on the bottom surface of the Amundsen Basin, 100 km to the west of the Lomonosov Ridge, at the Geophysicists Spur from the eastern side of the Lomonosov Ridge, and from the Laptev Sea. There are five control samples, which showed some local differences in the composition and distribution of zircon ages, with a total general similarity of these distributions. This fact indicates move the character of precipitation, as on the surface elevations and depressions in the sediment at the expense of local erosion of bedrock can not be formed. One of the sources of the Arctic Ocean sediments are traditionally considered «dirty» sea ice carrying material from the Canadian Archipelago, which are moved into the central part of the ocean due to Bofourt Gear flow. However, the distribution of zircon ages, revealed in the sediments, differs significantly from similar distributions for detrital zircon of Arctic coast of Alaska, the Canadian Archipelago, Greenland, Europe (Baltic Shield) and North America. But there are a lot more similarities with the zircon ages distributions typical for Asian continent, excluding China and India</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5711219','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5711219"><span id="translatedtitle">Strontium <span class="hlt">isotope</span> <span class="hlt">study</span>, Pine Barrens, Long Island, NY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xin, Geng; Hanson, G.N. . Dept. of Earth and Space Sciences)</p> <p>1993-03-01</p> <p>Twenty-four samples representing precipitation, through-fall, soil water, ground water, vegetation and soil were analyzed for strontium concentration and the [sup 87]Sr/[sup 86]Sr ratio. The Pine Barrens, which consists of forests and dense vegetation, covers approximately 300 square miles of the coastal plain of Long Island, New York. This <span class="hlt">study</span> estimates the relative importance of atmospheric and weathering inputs of Sr to vegetation in this ecosystem. The values of the [sup 87]Sr/[sup 86]Sr ratios and Sr concentration in the Pine Barrens are shown in the attached figure. Precipitation has Sr <span class="hlt">isotopic</span> ratios that are close to that of sea water (0.7092). The Sr in through-fall is dominated by the Sr from the canopy foliage. The [sup 87]Sr/[sup 86]Sr ratios of soil water and ground water increase with depth. The Sr <span class="hlt">isotopic</span> ratio for a composite sample of pine (0.71181) is a mixture of atmosphere Sr and soil or ground waters. The Sr <span class="hlt">isotopic</span> ratios and concentrations in pine suggest that plants are a major reservoir of Sr in the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780066146&hterms=Krypton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DKrypton','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780066146&hterms=Krypton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DKrypton"><span id="translatedtitle">s-process <span class="hlt">studies</span> - Xenon and krypton <span class="hlt">isotopic</span> abundances</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clayton, D. D.; Ward, R. A.</p> <p>1978-01-01</p> <p>We propose an analysis of the s-process contributions to the <span class="hlt">isotopes</span> of xenon and krypton. The object is to aid <span class="hlt">studies</span> of the possibility that meteorites may contain gas that was carried in presolar grains that were grown in stellar ejecta and that were not degassed prior to incorporation into parent bodies. That model suggests routine interstellar fractionation of s-<span class="hlt">isotopes</span> from r-<span class="hlt">isotopes</span> owing to differential incorporation into dust. We show that a deficiency of s-process nuclei cannot yield details of Xe-X, but the gross similarities are strong enough to lead one to think that such a deficiency may play a role in a more complicated explanation. We predict the existence of an s-rich complement somewhere if fractional separation of this type has played a role in Xe-X. We show that the analogous decomposition of krypton is more uncertain, and we call for measurements of neutron-capture cross sections to alleviate these uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19419008','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19419008"><span id="translatedtitle">Digenean trematodes-marine mollusc relationships: a stable <span class="hlt">isotope</span> <span class="hlt">study</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dubois, S Y; Savoye, N; Sauriau, P-G; Billy, I; Martinez, P; de Montaudouin, X</p> <p>2009-03-01</p> <p>The stable carbon and nitrogen <span class="hlt">isotopic</span> composition of digenean trematode parasites and their marine mollusc hosts was investigated to describe the potential influence of parasites on their host and its different tissues, and to obtain further insight into their trophic relationships. Four parasite-host systems were <span class="hlt">studied</span>: Labratrema minimus-Cerastoderma edule, Monorchis parvus-C. edule, Lepocreadiidae parasites-Nassarius reticulatus and Zoogonidae parasites-N. reticulatus. Among the 4 sampling occasions reported here and corresponding to the 4 parasite-host systems, <span class="hlt">isotopic</span> shifts from pathologic (i.e. linked to disturbances in host metabolism) and mass-balance (i.e. linked to significant differences between host and parasite <span class="hlt">isotopic</span> signatures) origins were observed only once. Both corresponded to delta 13C measurements of the L. minimus-C. edule system when the infestation load (percentage parasite dry weight compared to total flesh dry weight) was highest (9 to 25%, mean = 16%) over the sampling period. Overall, measurements indicate that digenean trematode parasitism induced low or no shifts in <span class="hlt">isotopic</span> signatures of C. edule and N. reticulatus tissues. The 2 endoparasites L. minimus and M. parvus appeared to be slightly depleted in 13C compared to C. edule digestive gland and gonads, which were the most parasitized tissues. In contrast, no fractionation or low 15N trophic enrichments occurred in the parasites. These results highly contrast with the classical trophic enrichment reported in prey-predator systems but are in agreement with the scarce literature regarding other parasite-host systems. Our results indicate that (1) digenean trematodes mainly feed on digestive glands (the cockle tissue with which they are mainly associated) with a possible slight preference for lipids, and (2) fractionation due to parasite metabolism should be low due to abbreviated metabolic pathways and/or slight loss of materials through excretion, tegument diffusion and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V13A2587S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V13A2587S"><span id="translatedtitle"><span class="hlt">Isotopic</span> Analysis of Fingernails as a USGS Open House Demonstration of the Use of Stable <span class="hlt">Isotopes</span> in Foodweb <span class="hlt">Studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silva, S. R.; Kendall, C.; Young, M. B.; Choy, D.</p> <p>2011-12-01</p> <p>The USGS <span class="hlt">Isotope</span> Tracers Project uses stable <span class="hlt">isotopes</span> and tritium to add a unique dimension of chemical information to a wide range of environmental investigations. The use and application of <span class="hlt">isotopes</span> is usually an unfamiliar and even esoteric topic to the general public. Therefore during three USGS open house events, as a public outreach effort, we demonstrated the use of stable <span class="hlt">isotopes</span> by analyzing nitrogen and carbon <span class="hlt">isotopes</span> from very small fragments of fingernail from willing participants. We titled the exhibit "You Are What You Eat". The results from all participants were plotted on a graph indicating the general influence of different food groups on the composition of body tissues as represented by fingernails. All participants were assigned a number and no personal-identification information was collected. A subset of participants provided us with an estimate of the number of days a week various foods were eaten and if they were vegetarians, vegans or non-vegetarians. Volunteers from our research group were on hand to explain and discuss fundamental concepts such as how foods attain their <span class="hlt">isotopic</span> composition, the difference between C3 and C4 plants, the effects of assimilation, trophic enrichment, and the various uses of stable <span class="hlt">isotopes</span> in environmental <span class="hlt">studies</span>. The results of the fingernail analyses showed the variation of the range of <span class="hlt">isotopic</span> compositions among about 400 people at each event, the distinct influence of C4 plants (mainly corn and cane sugar) on our carbon <span class="hlt">isotopic</span> composition, and the <span class="hlt">isotopic</span> differences between vegetarians and non vegetarians among other details (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/). A poll of visitors attending the open house event in 2006 indicated that "You Are What You Eat" was among the most popular exhibits. Following the first two open house events we were contacted by a group of researchers from Brazil who had completed a very similar <span class="hlt">study</span>. Our collaboration resulted in a publication in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Litho.262..107Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Litho.262..107Z"><span id="translatedtitle">Hf <span class="hlt">isotope</span> systematics of seamounts near the East Pacific Rise (EPR) and geodynamic implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yu; Meng, Fanxue; Niu, Yaoling</p> <p>2016-10-01</p> <p>We report new Hf <span class="hlt">isotopic</span> data for basaltic glasses from seamounts flanking the East Pacific Rise (EPR) between 5° and 15°N that have been previously analyzed for <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopes</span> as well as major and trace elements. The Hf <span class="hlt">isotopic</span> data offer new perspectives on the petrogenesis of these samples in a broader context on mantle dynamics. The Hf <span class="hlt">isotope</span> compositions show significant correlations with <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopes</span> and with both abundances and ratios of incompatible elements. The seamount lavas are thus best interpreted as products of melting-induced mixing in a two-component mantle. The range in composition of EPR seamount lavas cannot be generated by simple mixing of melt and melting of variably heterogeneous mantle in which enriched and depleted materials contribute equally to melting (source mixing). Instead, the trace element and <span class="hlt">isotope</span> compositions of seamount lavas can be reproduced by melting models in which more enriched, fertile mantle component are preferentially melted during mantle upwelling. At progressively lower degrees of melting, erupted lavas are thus more enriched in incompatible trace elements, have higher 87Sr/86Sr, 208Pb/204Pb ratios and lower 143Nd/144Nd, 176Hf/177Hf ratios. The "EM1" and "pyroxenite" endmember might be the suitable enriched component. The Hf-Nd <span class="hlt">isotopic</span> variations on global scale might result from the variations in amounts of residual continental lithospheric mantle that detached into upper mantle during continental rifting. The significant correlations of Rb/Sr vs 87Sr/86Sr, Sm/Nd vs 143Nd/144Nd and Lu/Hf vs 176Hf/177Hf give pseudochron ages of 182 ± 33 Ma, 276 ± 50 Ma and 387 ± 93 Ma, respectively. These different "ages" have no significance, but result from melting-induced mixing with the pseudochron slopes controlled by the compositions of enriched component and depleted end-member.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMDI31A2567L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMDI31A2567L"><span id="translatedtitle">Magnesium and calcium <span class="hlt">isotopic</span> characteristics of Tengchong volcanics: Recycling of marine carbonates into the SE Tibetan mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, F.; Zhang, Z.; Liu, Y.; Zhu, H.; Kang, J.; Zhang, C.; Sun, W.; Wang, G. Q.</p> <p>2015-12-01</p> <p>Post-collisional high-K calc-alkaline volcanic rocks are widely distributed in Tengchong in the southeastern margin of Tibetan Plateau. Previous considerable petrological and <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopic</span> researches undoubtedly indicate that the mantle beneath Tengchong is heterogeneous and enriched. However, the genesis of such a kind of mantle is still poor understood and needs more constrains. One of the key points lead to the answer to this question is that, is there any recycled carbonate involved? Therefore, Magnesium and calcium <span class="hlt">isotopic</span> compositions of mantle-derived volcanics should be investigated because they are good candidates to be potentially used to trace recycling of ancient marine carbonates into the mantle. In this <span class="hlt">study</span>, we report high-precision Mg and Ca <span class="hlt">isotopic</span> compositions for calc-alkaline volcanic rocks in Tengchong. These volcanic rocks show significantly lighter δ26Mg values (-0.44 to -0.36‰) than the mantle value (-0.25±0.07‰). Similarly, they display lighter δ44Ca values (0.65-0.80‰) than the mantle value (1.05±0.04‰). Because neither δ26Mg nor δ44Ca are correlated with SiO2 (50.8-61.6 wt.%) contents, and there is no relationships between δ26Mg or δ44Ca and typical trace element abundance ratios (e.g. Sm/Yb, Ba/Y), we conclude that magma differentiation or partial melting would lead to limited Mg and Ca <span class="hlt">isotopes</span> fractionation. Thus, low δ26Mg and δ44Ca signatures of Tengchong volcanic rocks probably reflect that the δ26Mg and δ44Ca characteristics of the underneath mantle source, and are resulted from adding ancient marine carbonates into the primitive mantle which has low Mg and Ca <span class="hlt">isotopic</span> compositions. Our model simulation using a two end-member mixing between Mg-Ca <span class="hlt">isotopic</span> compositions of primitive mantle and ancient marine carbonate indicates that carbonates involved in the mantle source is mainly dolostone with minor limestone. Combined with the geotectonic evolution history in Tengchong, we propose that the enriched</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.tmp...50Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.tmp...50Q"><span id="translatedtitle">Zircon U-Pb geochronology, and elemental and <span class="hlt">Sr-Nd</span>-Hf-O <span class="hlt">isotopic</span> geochemistry of post-collisional rhyolite in the Chiang Khong area, NW Thailand and implications for the melting of juvenile crust</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qian, Xin; Wang, Yuejun; Feng, Qinglai; Zi, Jian-Wei; Zhang, Yuzhi; Chonglakmani, Chongpan</p> <p>2016-06-01</p> <p>Volcanic rocks are widely exposed within the Chiang Khong-Lampang-Tak igneous zone in NW Thailand. A representative rhyolite sample from the Chiang Khong area yielded a zircon U-Pb age of 230.7 ± 1.1 Ma (n = 20, MSWD = 0.98). The Chiang Khong rhyolites are characterized by low TiO2 (0.29-0.62 wt%) and MgO (0.04-0.82 wt%) with A/CNK values of 0.95-1.06 (one outlier at 1.47), and can be classified as highly fractionated I-type rhyolites. They are enriched in LILEs and LREEs, and depleted in HFSEs. Two representative samples have 87Sr/86Sr (i) ratios of 0.70497 and 0.70527, and the ɛNd (t) values fall at +1.1 and +1.3, respectively. ɛHf (t) and δ18O in zircon are between +4.7 to +12.0 and 5.3 to 5.9 ‰, respectively. Our geochemical data suggest that the Chiang Khong rhyolites formed by partial melting of juvenile mafic lower crust in a post-collisional setting. Deep crustal anatexis was probably induced by upwelling asthenospheric mantle, shortly after slab detachment subsequent to closure of the Paleo-Tethys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAESc.127..137Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAESc.127..137Z"><span id="translatedtitle">Petrogenesis and tectonic implications of the high-K Alamas calc-alkaline granitoids at the northwestern margin of the Tibetan Plateau: Geochemical and <span class="hlt">Sr-Nd</span>-Hf-O <span class="hlt">isotope</span> constraints</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Qichao; Liu, Yan; Huang, He; Wu, Zhenhan; Zhou, Qing</p> <p>2016-09-01</p> <p>The Alamas granitoid pluton in the eastern part of the Western Kunlun Orogen, the northwestern margin of the Tibetan Plateau, is composed of quartz diorite. Zircon separates from the pluton has SIMS U-Pb age of ∼446 Ma. Rocks from the pluton have a narrow range of SiO2 (56.84-62.57 wt%), MgO (1.76-2.94 wt%), and total alkalis (Na2O + K2O = 5.14-9.59 wt%), and are metaluminous and high-K calc-alkaline to shoshonitic in composition. They are enriched in light rare earth elements (LREEs), with (La/Yb)N = 14-25, and show weakly negative Eu anomalies. These rocks are relatively enriched in Sr (472-676 ppm) and Ba (435-2388 ppm), and depleted in Nb, Ta, Th, and Ti. Their εNd(t) values range from -6.4 to -8.4, and (87Sr/86Sr)i = 0.7184-0.7200. Zircons from the pluton show εHf(t) values of -1.4 to -8.8, and δ18O = 6.4-9.0‰. Geochemical data indicate that the granitoids were likely derived from the reworking of an ancient, deep crustal source, influenced by a minor mantle-derived component. Magmatic differentiation was dominated by the fractional crystallization of hornblende, biotite, and accessory minerals such as apatite, allanite, and Fe-Ti oxides. In summary, the Late Ordovician Alamas pluton is an I-type granitoid that was emplaced in a post-collisional environment, suggesting that this tectonic stage had already initiated prior to ∼445 Ma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025663','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025663"><span id="translatedtitle">New osmium <span class="hlt">isotope</span> evidence for intracrustal recycling of crustal domains with discrete ages</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hart, G.L.; Johnson, C.M.; Hildreth, W.; Shirey, S.B.</p> <p>2003-01-01</p> <p>New 187Os/188Os ratios of Quaternary Mount Adams volcanic rocks from the Cascade arc in southern Washington vary by >300% (187Os/188Os = 0.165-0.564) and fall into high (>0.319) and low (0.166 to 0.281) groups of 187Os/188Os ratios that are substantially more radiogenic than mantle values. These Os <span class="hlt">isotope</span> compositions and groupings are interpreted to reflect recycling of discrete intracrustal domains with high 187Os/188Os ratios but differing ages, thus recording the process of crustal hybridization and homogenization. Os <span class="hlt">isotope</span> compositions provide new constraints on amounts of intracrustal recycling in young subduction-zone environments that reflect the magmatic history of the arc. <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Hf, and Pb <span class="hlt">isotope</span> variations in this young, mafic are complex are too small to allow such constraints.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.H53A1204C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.H53A1204C"><span id="translatedtitle">A "Tail" Of Two Mines: Determining The Sources Of Lead In Mine Waters Using Pb <span class="hlt">Isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cousens, B. L.; Allen, D. M.; Lepitre, M. E.; Mortensen, J. K.; Gabites, J. E.; Nugent, M.; Fortin, D.</p> <p>2004-12-01</p> <p>, all water samples collected downstream from the mine site have low Pb concentrations and variably more radiogenic Pb <span class="hlt">isotope</span> ratios. Water samples from a well on the mine site and a pipe discharging water from below the tailings dam also have non-ore Pb <span class="hlt">isotope</span> ratios. The <span class="hlt">isotopic</span> compositions of low-Pb samples do not lie on a mixing line between ore and local host rocks, but rather lie on a mixing line between agricultural ditch and stream waters upstream of the mine and New Calumet ore. These waters may form a groundwater system flowing under the mine site that is virtually uncontaminated by the overlying ores and tailings. Compared to the Sullivan case, metals from the New Calumet ore and tailings are only weakly mobilized into local waters, probably due to buffering of waters by carbonate-bearing host rocks. We are impressed with the fingerprinting ability of Pb <span class="hlt">isotopes</span> to track the sources of heavy metals in water systems, and suggest that other radiogenic <span class="hlt">isotopes</span> (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>) may also be useful in environmental <span class="hlt">studies</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1910520','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1910520"><span id="translatedtitle">Stable carbon <span class="hlt">isotopes</span> and the <span class="hlt">study</span> of prehistoric human diet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boutton, T W; Lynott, M J; Bumsted, M P</p> <p>1991-01-01</p> <p>Mass spectrometric analysis of the stable carbon <span class="hlt">isotope</span> composition (13C/12C or delta 13C) of bone collagen from human remains recovered at archaeological sites provides a direct chemical method for investigating dietary patterns of prehistoric human populations. This methodology is based on the facts that (1) different food items within the human diet have distinct delta 13C values, and (2) the delta 13C value of human bone collagen is determined by the delta 13C value of the diet. <span class="hlt">Studies</span> of the development of subsistence patterns based on corn agriculture, one of the most significant developments in North American prehistory, can benefit from the use of stable carbon <span class="hlt">isotope</span> techniques because corn has a high delta 13C value relative to other components of the human diet. Measurements of delta 13C of bone collagen from prehistoric human skeletal remains from southeastern Missouri and northeastern Arkansas indicate that intensive corn agriculture began in this region around A.D. 1000, that the incorporation of corn into the human diet was a rapid phenomenon, and that 35 to 77% of the human diet from A.D. 1000 to A.D. 1600 consisted of corn. Results from an isochronous population in southeastern South Dakota (A.D. 1400) suggest that 78 to 90% of the diet of this group consisted of corn, with no difference between males and females. Coupled with more traditional archaeological methods, stable carbon <span class="hlt">isotope</span> analysis of bone collagen can significantly enhance reconstruction of dietary patterns of prehistoric humans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1411264G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1411264G"><span id="translatedtitle"><span class="hlt">Study</span> of Urban environmental quality through <span class="hlt">Isotopes</span> δ13C</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>González-Sosa, E.; Mastachi-Loza, C.; Becerril-Piña, R.; Ramos-Salinas, N. M.</p> <p>2012-04-01</p> <p>Usually, trees with similar pH values on their bark develop epiphytes of similar species, the acidity to be a factor for growth. The aim of the <span class="hlt">study</span> was evaluate the air quality through <span class="hlt">isotope</span> δ13C in order to define the levels of environmental quality in the city of Queretaro, Mexico. In this work were collected at least 4 epiphytes positioned in trees of the species Prosopis Laevigata at 25 sites of Queretaro City. The samples were analyzed for trace elements with an inductively coupled plasma atomic emission spectroscopy (ICP). The collecting took place during dry period, in May and early rain June 2011 period, and on four sectors to identify the spatial distribution of pollution, using <span class="hlt">isotopic</span> analysis of concentration of δ 13C. According with the results there are significant differences among the species in each of the sampled areas. The 5 February Avenue presented greater diversity and richness of δ13C, followed by those who were surveyed in the proximity of the UAQ and finally in the middle-east area. An average value of δ13C-17.92%, followed by those surveyed in the vicinity of the UAQ that correspond to sector I and II with an concentration of δ13C-17.55% and δ13C-17.22%, and finally the samples collected in trees scattered in the East-Sector II and IV with a value of δ13C-17.02% and δ13C-15.62%, respectively. Also were observed differences between the dry and wet period. It is likely that these results of δ 13C in moist period reflect the drag of the <span class="hlt">isotopes</span> due to rain events that could mark a trend in the dilution of this element, however there is a trend in terms of abundance and composition of finding more impact in those species sampled in dry period, in May and early June 2011.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/112990','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/112990"><span id="translatedtitle">Neutron-rich B <span class="hlt">isotopes</span> <span class="hlt">studied</span> with antisymmetrized molecular dynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kanada-En`yo, Y.; Horiuchi, H.</p> <p>1995-08-01</p> <p>Structure of odd-even B <span class="hlt">isotopes</span> up to the neutron dripline is <span class="hlt">studied</span> systematically with the antisymmetrized molecular dynamics (AMD). The AMD method has already proved to be a powerful theoretical approach for the systematic <span class="hlt">study</span> of nuclear structure in extensive region including exotic neutron-rich nuclei as well as ordinary nuclei. It is owing to its flexible nature free from any model assumptions such as the existence of clusters. The energies and other observed data of B <span class="hlt">isotopes</span> are reproduced well. Especially very good reproduction of electromagnetic properties is obtained. The systematic behavior of the electromagnetic properties is explained in relation to the drastic change between clustering structure and shell-model-like structure. This explanation gives us an important indication that clustering structure in neutron-rich B nuclei is strongly suggested by the experimental data. It is shown that the structure change with increase of the neutron number is largely governed by the shell effect of neutron orbits. Exotic structure with new type of clustering is suggested to evolve in neutron-rich nuclei near the dripline.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..APR.R3003C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..APR.R3003C"><span id="translatedtitle">Inelastic proton scattering of Sn <span class="hlt">isotopes</span> <span class="hlt">studied</span> with GRETINA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Campbell, Christopher</p> <p>2014-03-01</p> <p>The chain of semi-magic Sn nuclei, with many stable <span class="hlt">isotopes</span>, has been a fertile ground for experimental and theoretical <span class="hlt">studies</span>. Encompassing a major neutron shell from N = 50 to 82, the properties and structure of these nuclei provided important data for the development of the pairing-plus-quadrupole model. Recent experimental information on B(E2) for 106,108,110,112Sn came as a surprise as it indicated a larger collectivity than the predicted parabolic trend of quadrupole collectivity. These data, instead, show an unexpectedly flat trend even as the number of valence particles is reduced from 12 to 6. To fully understand how collectivity is evolving in these <span class="hlt">isotopes</span>, 108,110,112Sn have been <span class="hlt">studied</span> using thick-target, inelastic proton scattering with GRETINA tagging inelastic scattering events by detecting gamma-rays from the prompt decay of states excited in the reaction. We will present the trend of 2 + excitation cross-sections, the deduced quadrupole deformation parameters, and observations of other low-lying collective states. Comparison of these (p,p') quadrupole deformation parameters with B(E2) data will provide new insights into the relative importance of proton and neutron contributions to collectivity in these nuclei. GRETINA was funded by the US DOE - Office of Science. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY-1102511(NSCL) and DOE under grant DE-AC02-05CH11231(LBNL).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V42B..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V42B..07M"><span id="translatedtitle">Correlations between Pb <span class="hlt">isotopes</span> and volatile elements in melt inclusions from Sao Miguel, Azores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreira, M. A.; Rose-Koga, E. F.; Koga, K. T.; Vlastelic, I.; Shimizu, N.; Whitehouse, M.</p> <p>2009-12-01</p> <p>Sao Miguel is the biggest eastern-most island of the Azores archipelago in the northern Atlantic and is known to have a very peculiar <span class="hlt">isotopic</span> systematics including <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb. We <span class="hlt">studied</span> 4 lavas of Sao Miguel, one is from the 1563 historical lava flow Queimado peak eruption, one is from Picos Volcanic zone and the two others are Pliocene ankaramites from the Nordest. The olivine phenocrysts of these samples have been documented for helium <span class="hlt">isotopes</span> and show very radiogenic 3He/4He ratios (<6Ra). We analyzed 9 primitive olivine-hosted melt inclusions for both Pb <span class="hlt">isotopes</span> and volatile element concentrations (H2O, CO2, F, S, and Cl). The Pb <span class="hlt">isotope</span> ratios were measured by a multicollection SIMS 1280 (NMNH Stockholm, Sweden) and volatiles by a monocollection SIMS 1280 (WHOI, USA). The repeated 207Pb/206Pb measurements of the GOR132 glass standard (20 ppm Pb) yielded a 0.15% relative variation (1 sigma of the distribution). All the melt inclusions have 207Pb/206Pb (0.782 to 0.797) and 208Pb/206Pb (1.969 to 2.041) lower than MORB value (DMM: 0.857, 2.053), i.e., more radiogenic compositions. We found positive linear correlations between 207Pb/206Pb and CO2, F, S, and Cl. The correlations further improve when Pb <span class="hlt">isotope</span> ratios are plotted against F/P2O5, and Cl/K2O. The Sao Miguel source is characterized by a mixing between a low 207Pb/206Pb and low 208Pb/206Pb in the Nordest coming from a long time residence of high (U+Th)/Pb recycled material, and a component with higher ratios, more similar to other islands from the central group. The low 3He/4He ratio measured on Nordest samples also suggests a high (U+Th)/3He in its source, which may be due to degassing presumably during an early stage of the recycling. The low 207Pb/206Pb with low volatiles samples could also be explain this early degassing. Samples with the highest 207Pb/206Pb are richer in volatile suggesting the presence of a volatile rich lithology beneath the Azores central group, which was also proposed by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22321257','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22321257"><span id="translatedtitle">Concrete under sulphate attack: an <span class="hlt">isotope</span> <span class="hlt">study</span> on sulphur sources.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mittermayr, Florian; Bauer, Christoph; Klammer, Dietmar; Böttcher, Michael E; Leis, Albrecht; Escher, Peter; Dietzel, Martin</p> <p>2012-01-01</p> <p>The formation of secondary sulphate minerals such as thaumasite, ettringite and gypsum is a process causing severe damage to concrete constructions. A major key to understand the complex reactions, involving concrete deterioration is to decipher the cause of its appearance, including the sources of the involved elements. In the present <span class="hlt">study</span>, sulphate attack on the concrete of two Austrian tunnels is investigated. The distribution of stable sulphur <span class="hlt">isotopes</span> is successfully applied to decipher the source(s) of sulphur in the deteriorating sulphate-bearing minerals. Interestingly, δ(34)S values of sulphate in local groundwater and in the deteriorating minerals are mostly in the range from+14 to+27 ‰. These δ(34)S values match the <span class="hlt">isotope</span> patterns of regional Permian and Triassic marine evaporites. Soot relicts from steam- and diesel-driven trains found in one of the tunnels show δ(34)S values from-3 to+5 ‰, and are therefore assumed to be of minor importance for sulphate attack on the concretes. In areas of pyrite-containing sedimentary rocks, the δ(34)S values of sulphate from damaged concrete range between-1 and+11 ‰. The latter range reflects the impact of sulphide oxidation on local groundwater sulphate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22321257','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22321257"><span id="translatedtitle">Concrete under sulphate attack: an <span class="hlt">isotope</span> <span class="hlt">study</span> on sulphur sources.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mittermayr, Florian; Bauer, Christoph; Klammer, Dietmar; Böttcher, Michael E; Leis, Albrecht; Escher, Peter; Dietzel, Martin</p> <p>2012-01-01</p> <p>The formation of secondary sulphate minerals such as thaumasite, ettringite and gypsum is a process causing severe damage to concrete constructions. A major key to understand the complex reactions, involving concrete deterioration is to decipher the cause of its appearance, including the sources of the involved elements. In the present <span class="hlt">study</span>, sulphate attack on the concrete of two Austrian tunnels is investigated. The distribution of stable sulphur <span class="hlt">isotopes</span> is successfully applied to decipher the source(s) of sulphur in the deteriorating sulphate-bearing minerals. Interestingly, δ(34)S values of sulphate in local groundwater and in the deteriorating minerals are mostly in the range from+14 to+27 ‰. These δ(34)S values match the <span class="hlt">isotope</span> patterns of regional Permian and Triassic marine evaporites. Soot relicts from steam- and diesel-driven trains found in one of the tunnels show δ(34)S values from-3 to+5 ‰, and are therefore assumed to be of minor importance for sulphate attack on the concretes. In areas of pyrite-containing sedimentary rocks, the δ(34)S values of sulphate from damaged concrete range between-1 and+11 ‰. The latter range reflects the impact of sulphide oxidation on local groundwater sulphate. PMID:22321257</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001E%26PSL.186..527S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001E%26PSL.186..527S"><span id="translatedtitle">Correlated Os-Pb-Nd-Sr <span class="hlt">isotopes</span> in the Austral-Cook chain basalts: the nature of mantle components in plume sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schiano, P.; Burton, K. W.; Dupré, B.; Birck, J.-L.; Guille, G.; Allègre, C. J.</p> <p>2001-04-01</p> <p>Osmium (Os), strontium (Sr), neodymium (Nd) and lead (Pb) <span class="hlt">isotopes</span> have been measured on a suite of aphyric basalts from 12 islands of the Austral-Cook island archipelago, an area which exhibits a range in Pb <span class="hlt">isotope</span> compositions that encompasses almost the entire range displayed by ocean island basalts (OIB). Although the samples have Os concentrations (1.69-34.80 ppt) at the lower end of the range measured for OIB, they display a range of initial 187Os/ 188Os ratios (between 0.1279 and 0.1594) similar to that defined by olivine-phyric, Os-rich OIB. Positive Os-Nd, Os-Pb and negative Os-Sr <span class="hlt">isotope</span> correlations are documented, indicating that the <span class="hlt">isotopic</span> arrays represent various proportions of mixing between a HIMU-type end-member represented by Mangaia and Tubuai islands and characterized by radiogenic Os and Pb <span class="hlt">isotopic</span> compositions, and an end-member represented by Rarotonga island which is characterized by unradiogenic Os and intermediate <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopic</span> compositions. The HIMU signature of the mantle component involved in Tubuai-Mangaia mantle sources requires long-term enrichments of U and Th relative to Pb and Re relative to Os, without associated increase in Rb/Sr, that are consistent with recycled oceanic crust. The end-member represented by Rarotonga basalts shows Os, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotopic</span> signatures similar to those presumed for the 'bulk silicate earth' (BSE), which cannot be obtained by mixing the four mantle components (DMM, HIMU and EM1 and 2) generally used to circumscribe the <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopic</span> data of OIB. The primitive-like <span class="hlt">isotopic</span> characters of this end-member might be ascribed to the presence of undepleted material from a lower segment of the mantle in the source of the Austral-Cook island basalts (and more specifically Rarotonga basalts); however, such a hypothesis is challenged by both the absence of a primordial 3He signature and the non-primitive Ce/Pb and Nb/U values for the Austral-Cook island basalts. Alternatively, assuming</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70011488','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70011488"><span id="translatedtitle"><span class="hlt">Isotope</span> <span class="hlt">studies</span> of dolomite formation under sedimentary conditions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Clayton, R.N.; Jones, B.F.</p> <p>1968-01-01</p> <p>Measurements of stable <span class="hlt">isotope</span> abundances of the carbonate portion of the sediment in Deep Springs Lake, California, indicate the presence of at least three phases: a magnesian calcite, a primary sedimentary dolomite, and a detrital dolomite. The former two have <span class="hlt">isotopic</span> compositions consistent with precipitation at <span class="hlt">isotopic</span> equilibrium from waters of the lake area. The measured <span class="hlt">isotopic</span> fractionation factor between sedimentary dolomite and its interstitial water is 1.0351, which is outside the range possible for calcite-water. This indicates that the dolomite has formed by direct crystallization from solution and not from a caloite precursor without further <span class="hlt">isotope</span> exchange. <span class="hlt">Isotopic</span> and X-ray evidence does not support the contention of Peterson et al. (1966) that Deep Springs Lake dolomite crystals grow by means of a calcite-like surface layer. ?? 1968.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.tmp..120G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.tmp..120G"><span id="translatedtitle">U-Pb ages, geochemistry, C-O-Nd-Sr-Hf <span class="hlt">isotopes</span> and petrogenesis of the Catalão II carbonatitic complex (Alto Paranaíba Igneous Province, Brazil): implications for regional-scale heterogeneities in the Brazilian carbonatite associations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guarino, Vincenza; Wu, Fu-Yuan; Melluso, Leone; de Barros Gomes, Celso; Tassinari, Colombo Celso Gaeta; Ruberti, Excelso; Brilli, Mauro</p> <p>2016-09-01</p> <p>The Catalão II carbonatitic complex is part of the Alto Paranaíba Igneous Province (APIP), central Brazil, close to the Catalão I complex. Drill-hole sampling and detailed mineralogical and geochemical <span class="hlt">study</span> point out the existence of ultramafic lamprophyres (phlogopite-picrites), calciocarbonatites, ferrocarbonatites, magnetitites, apatitites, phlogopitites and fenites, most of them of cumulitic origin. U-Pb data have constrained the age of Catalão I carbonatitic complex between 78 ± 1 and 81 ± 4 Ma. The initial strontium, neodymium and hafnium <span class="hlt">isotopic</span> data of Catalão II (87Sr/86Sri = 0.70503-0.70599; ɛNdi = -6.8 to -4.7; 176Hf/177Hf = 0.28248-0.28249; ɛHfi = -10.33 to -10.8) are similar to the <span class="hlt">isotopic</span> composition of the Catalão I complex and fall within the field of APIP kimberlites, kamafugites and phlogopite-picrites, indicating the provenance from an old lithospheric mantle source. Carbon <span class="hlt">isotopic</span> data for Catalão II carbonatites (δ13C = -6.35 to -5.68 ‰) confirm the mantle origin of the carbon for these rocks. The origin of Catalão II cumulitic rocks is thought to be caused by differential settling of the heavy phases (magnetite, apatite, pyrochlore and sulphides) in a magma chamber repeatedly filled by carbonatitic/ferrocarbonatitic liquids (s.l.). The <span class="hlt">Sr-Nd</span> <span class="hlt">isotopic</span> composition of the Catalão II rocks matches those of APIP rocks and is markedly different from the <span class="hlt">isotopic</span> features of alkaline-carbonatitic complexes in the southernmost Brazil. The differences are also observed in the lithologies and the magmatic affinity of the igneous rocks found in the two areas, thus demonstrating the existence of regional-scale heterogeneity in the mantle sources underneath the Brazilian platform.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6599337','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6599337"><span id="translatedtitle">Carbon and nitrogen <span class="hlt">isotope</span> <span class="hlt">studies</span> in an arctic ecosystem</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schell, D.M.</p> <p>1989-01-01</p> <p>This proposal requests funding for the completion of our current ecological <span class="hlt">studies</span> at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our <span class="hlt">study</span> including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen <span class="hlt">isotope</span> abundances vary between species of plants and along hydrologic gradients.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10137214','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10137214"><span id="translatedtitle">Carbon and nitrogen <span class="hlt">isotope</span> <span class="hlt">studies</span> in an arctic ecosystem</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schell, D.M.</p> <p>1989-12-31</p> <p>This proposal requests funding for the completion of our current ecological <span class="hlt">studies</span> at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our <span class="hlt">study</span> including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen <span class="hlt">isotope</span> abundances vary between species of plants and along hydrologic gradients.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/83371','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/83371"><span id="translatedtitle"><span class="hlt">Isotope</span> labeling for NMR <span class="hlt">studies</span> of macromolecular structure and interactions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wright, P.E.</p> <p>1994-12-01</p> <p>Implementation of biosynthetic methods for uniform or specific <span class="hlt">isotope</span> labeling of proteins, coupled with the recent development of powerful heteronuclear multidimensional NMR methods, has led to a dramatic increase in the size and complexity of macromolecular systems that are now amenable to NMR structural analysis. In recent years, a new technology has emerged that combines uniform {sup 13}C, {sup 15}N labeling with heteronuclear multidimensional NMR methods to allow NMR structural <span class="hlt">studies</span> of systems approaching 25 to 30 kDa in molecular weight. In addition, with the introduction of specific {sup 13}C and {sup 15}N labels into ligands, meaningful NMR <span class="hlt">studies</span> of complexes of even higher molecular weight have become feasible. These advances usher in a new era in which the earlier, rather stringent molecular weight limitations have been greatly surpassed and NMR can begin to address many central biological problems that involve macromolecular structure, dynamics, and interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000108939&hterms=Fractionation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DFractionation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000108939&hterms=Fractionation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DFractionation"><span id="translatedtitle">Iron-<span class="hlt">Isotopic</span> Fractionation <span class="hlt">Studies</span> Using Multiple Collector Inductively Coupled Plasma Mass Spectrometry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anbar, A. D.; Zhang, C.; Barling, J.; Roe, J. E.; Nealson, K. H.</p> <p>1999-01-01</p> <p>The importance of Fe biogeochemistry has stimulated interest in Fe <span class="hlt">isotope</span> fractionation. Recent <span class="hlt">studies</span> using thermal ionization mass spectrometry (TIMS) and a "double spike" demonstrate the existence of biogenic Fe <span class="hlt">isotope</span> effects. Here, we assess the utility of multiple-collector inductively-coupled plasma mass spectrometry(MC-ICP-MS) with a desolvating sample introduction system for Fe <span class="hlt">isotope</span> <span class="hlt">studies</span>, and present data on Fe biominerals produced by a thermophilic bacterium. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGeo...12.3289K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGeo...12.3289K"><span id="translatedtitle">Technical Note: A simple method for vaterite precipitation for <span class="hlt">isotopic</span> <span class="hlt">studies</span>: implications for bulk and clumped <span class="hlt">isotope</span> analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kluge, T.; John, C. M.</p> <p>2015-06-01</p> <p>Calcium carbonate (CaCO3) plays an important role in the natural environment as a major constituent of the skeleton and supporting structure of marine life and has high economic importance as an additive in food, chemicals and medical products. Anhydrous CaCO3 occurs in the three different polymorphs calcite, aragonite and vaterite, whereof calcite is the most abundant and best characterized mineral. In contrast, little is known about the rare polymorph vaterite, in particular with regard to the oxygen <span class="hlt">isotope</span> fractionation between H2O and the mineral. Synthetic precipitation of vaterite in the laboratory typically involves rapid processes and <span class="hlt">isotopic</span> non-equilibrium, which excludes <span class="hlt">isotope</span> <span class="hlt">studies</span> focused on the characterization of vaterite under equilibrium conditions. Here, we used a new experimental approach that enables vaterite mineral formation from an <span class="hlt">isotopically</span> equilibrated solution. The solution consists of a ~0.007 mol L-1 CaCO3 solution that is saturated with NaCl at room temperature (up to 6.4 mol L-1). Vaterite precipitated as single phase or major phase (≥94%) in experiments performed between 23 and 91 °C. Only at 80 °C was vaterite a minor phase with a relative abundance of 27%. The high mineral yield per experiment of up to 235 mg relative to the initially dissolved CaCO3 amount of on average 360 mg enables an investigation of the oxygen <span class="hlt">isotope</span> fractionation between the mineral and water, and the determination of clumped <span class="hlt">isotope</span> values in vaterite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110013324','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110013324"><span id="translatedtitle"><span class="hlt">Isotope</span> Fractionation <span class="hlt">Studies</span> in Prestellar Cores: The Case of Nitrogen</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Milam, Stefanie N.; Charnley, Steven B.</p> <p>2011-01-01</p> <p><span class="hlt">Isotopically</span> fractionated material is found in many solar system objects, including meteorites and comets. It is considered, in some cases, to trace interstellar material that was incorporated into the solar system without undergoing significant processing, thus preserving the fractionation. In interstellar molecular clouds, ion-molecule chemistry continually cycles nitrogen between the two main reservoirs - N and N2 - leading to only minor N-15 enrichments. Charnley and Rodgers showed that depletion of CO removes oxygen from the gas and weakens this cycle such that significant N-15 fractionation can occur for N2 and other N-bearing species in such cores. Observations are being conducted at millimeter and submillimeter wavelengths employing various facilities in order to both spatially and spectrally, resolve emission from these cores. A preliminary <span class="hlt">study</span> to obtain the N-14/N-15 ratio in nitriles (HCN and HNC) was conducted at the Arizona Radio Observatory's 12m telescope on Kitt Peak, AZ. Spectra were obtained at high resolution (0.08 km/s) in order to resolve dynamic properties of each source as well as to resolve hyperfine structure present in certain isotopologues. This <span class="hlt">study</span> included four dark cloud cores, observed to have varying levels of molecular depletion: L1521E, L1498, L1544, and L1521F. Previous <span class="hlt">studies</span> of the N-14/N-15 ratio towards LI544 were obtained with N2H+ and NIH3, yielding ratios of 446 and >700, respectively. The discrepancy observed in these two measurements suggests a strong chemical dependence on the fractionation of nitrogen. Ratios (C,N, and D) obtained from isotopologues for a particular molecule are likely tracing the same chemical heritage and are directly comparable within a given source. Results and comparisons between the protostellar evolutionary state and isomer <span class="hlt">isotope</span> fractionation as well as between other N-bearing species will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24437700','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24437700"><span id="translatedtitle">The <span class="hlt">isotope</span> altitude effect reflected in groundwater: a case <span class="hlt">study</span> from Slovenia.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mezga, Kim; Urbanc, Janko; Cerar, Sonja</p> <p>2014-01-01</p> <p>This paper presents the stable <span class="hlt">isotope</span> data of oxygen (δ(18)O) and hydrogen (δ(2)H) in groundwater from 83 sampling locations in Slovenia and their interpretation. The <span class="hlt">isotopic</span> composition of water was monitored over 3 years (2009-2011), and each location was sampled twice. New findings on the <span class="hlt">isotopic</span> composition of sampled groundwater are presented, and the data are also compared to past <span class="hlt">studies</span> regarding the <span class="hlt">isotopic</span> composition of precipitation, surface water, and groundwater in Slovenia. This <span class="hlt">study</span> comprises: (1) the general characteristics of the <span class="hlt">isotopic</span> composition of oxygen and hydrogen in groundwater in Slovenia, (2) the spatial distribution of oxygen <span class="hlt">isotope</span> composition (δ(18)O) and d-excess in groundwater, (3) the groundwater <span class="hlt">isotope</span> altitude effect, (4) the correlation between groundwater d-excess and the recharge area altitude of the sampling location, (5) the relation between hydrogen and oxygen <span class="hlt">isotopes</span> in groundwater in comparison to the global precipitation <span class="hlt">isotope</span> data, (6) the groundwater <span class="hlt">isotope</span> effect of distance from the sea, and (7) the estimated relation between the mean temperature of recharge area and δ(18)O in groundwater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880012217','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880012217"><span id="translatedtitle"><span class="hlt">Isotopic</span> and chemical <span class="hlt">studies</span> of early crustal metasedimentary rocks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jacobsen, Stein B.</p> <p>1988-01-01</p> <p>The aim, within the bounds of the Early Crustal Genesis Project, was the <span class="hlt">isotopic</span> and chemical <span class="hlt">study</span> of selected early crustal meta-sedimentary rocks. Western Australia was chosen as the first field area to examine, as the Yilgarn and Pilbara Blocks comprise one of the largest and most varied Precambrian terranes. Furthermore, the Western Gneiss Terrane (on the western flank of the Yilgarn Block) and the Pilbara Block are both non-greenstone in character; these types of terrane were relatively neglected, but are of great significance in the understanding of early crustal meta-sediments. The meta-sediments of aluminous or peraluminous character, commonly also enriched in Mg and/or Fe relative to the more common pelitic meta-sediments, and at many locations, deficient in one or more of the elements Ca, N, and K, were initially chosen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5709467','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5709467"><span id="translatedtitle">Decay <span class="hlt">studies</span> of neutron deficient rare earth <span class="hlt">isotopes</span> with OASIS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gilat, J.; Nitschke, J.M.; Wilmarth, P.A.; Vierinen, K.; Firestone, R.B.</p> <p>1987-09-01</p> <p>We report results on the decay of /sup 124/Pr, /sup 124,125/Ce, /sup 124,125/La, /sup 134-136/Eu, /sup 134-136/Sm, /sup 134-136/Pm, /sup 144/Ho, /sup 141,142,144/Dy, /sup 140,141,142,144/Tb, /sup 140-142/Gd, and /sup 140-142/Eu, produced by /sup 92/Mo(H.I.,xpyn) reactions at the Berkeley SuperHILAC, and <span class="hlt">studied</span> with the OASIS on-line mass separator facility. Half-lives, delayed proton branching ratios, ..gamma..-ray energies and intensities, partial decay schemes and several J/sup ..pi../ assignments are presented. Level systematics of the even mass Nd and Sm <span class="hlt">isotopes</span> and of the nu h/sub 11/2/ - nu s/sub 1/2/ isomers for N = 77 are discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10407314','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10407314"><span id="translatedtitle">A dynamic <span class="hlt">study</span> of earthworm feeding ecology -using stable <span class="hlt">isotopes</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Briones; Bol; Sleep; Sampedro; Allen</p> <p>1999-07-01</p> <p>Changes in the specific diet of earthworms with time in relation to landuse changes and two different climates were <span class="hlt">studied</span> by analysing (13)C and (15)N natural abundance in soils and animals. Soil samples from three depths (0-10, 10-20 and 20-30 cm) and earthworms were collected from two sites: Santiago (Northwest Spain) and North Wyke (Southwest England) both consisting of replicated long-term grasslands and recently converted to maize plots. Earthworms were hand-sorted in the field at the peak of the maize growth and after harvesting at both sites. In the Spanish plots, nine and eight earthworm species, all belonging to the three ecological categories (epigeic, anecic and endogeic), were found under maize and permanent pasture, whereas at the English site five and seven different species were, respectively, identified. At both sites (13)C <span class="hlt">isotopic</span> values of the earthworm tissues reflected changes in diet from C(3) to C(4) with epigeic and epi/anecic worms in the maize plots showing one delta unit difference in relation to the ones found in the grassland plots. Anecic worms seemed to be less responsive to landuse changes. The higher (13)C values of the Spanish soils were also reflected in the earthworm tissues when compared with the English samples. (15)N values showed no clear relationship with the cropping treatments but were clearly related to the ecological grouping, with endogeic worms reaching the highest values whereas for the epigeic and epi/anecic species the lowest values were obtained. This finding was also previously recorded by other authors1 and suggests that, in the future, stable <span class="hlt">isotope</span> techniques could also be a useful tool in taxonomic <span class="hlt">studies</span>. Copyright 1999 John Wiley & Sons, Ltd. PMID:10407314</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994Metic..29S.519P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994Metic..29S.519P"><span id="translatedtitle">Petrologic and oxygen <span class="hlt">isotopic</span> <span class="hlt">study</span> of ALH 85085-like chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prinz, M.; Weisberg, M. K.; Clayton, R. N.; Mayeda, T. K.; Ebihara, M.</p> <p>1994-07-01</p> <p>Four meteorites (PAT 91546, PCA 91328, PCA 91452, PCA 91467) petrologically similar to ALH 85085 chondrite have now been found. Previous <span class="hlt">studies</span> of ALH 85085 showed it be a new kind of CR-related microchondrule-bearing chondrite, although one called it a sub-chondrite. The purpose of this <span class="hlt">study</span> is to learn more about ALH 85085-like meteorites and their relationship to CR and CR-related (LEW 85332, Acfer 182, Bencubbin) chondrites. The methods used included petrology, INA bulk chemical analysis (PAT 91546, PCA 91467), and O <span class="hlt">isotopic</span> analyses of the whole rocks and separated chondrules and dark inclusions (DIs) from PAT 91546. Since microchondrules and fragments are approximately 20 microns it was necessary to analyze composite samples for O; one was of approximately 100 chondrules, and another was of 5 DIs. Petrologically, the four meteorites are similar to ALH 85085, and there is no basis for determining if all of them, or any combinations, are paired. Mineralogically, olivine and pyroxene are highly magnesian FeNi metal generally has 3-10% Ni, and has a positive Ni-Co correlation similar to that in CR and CR-related chondrites. Refractory inclusions are similar in size to the chondrules and have the following assemblages: (1) hibonite-perovskite, (2) melilite-fassaite-forsterite, (3) grossite (Ca-dialuminate)-melilite-perovskite, (4) spinel-melilite, and (5) spinel-pyroxene aggregates. Chemically, INA analyses indicate that PAT 91546 and PCA 91467 are generally similar to ALH 85085. Oxygen <span class="hlt">isotopic</span> analyses of the four whole-rock compositions fall along the CR mixing line as does ALH 85085; they are also close to LEW 85332, Acfer 182, and Bencubbin. This supports the concept that these are all CR-related chondrites. Even stronger support is found in the compositions of the chondrules and DIs in PAT 91546, which also plot on or near the CR line.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=83025&keyword=forensic&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=80466415&CFTOKEN=45206457','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=83025&keyword=forensic&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=80466415&CFTOKEN=45206457"><span id="translatedtitle">USE OF STABLE <span class="hlt">ISOTOPES</span> IN ENVIRONMENTAL AND FORENSIC GEOCHEMISTRY <span class="hlt">STUDIES</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Stable carbon and hydrogen <span class="hlt">isotopes</span> have been used for many decades in the petroleum industry, but the development of combined gas chromatography-<span class="hlt">isotope</span> ratio mass spectrometry (GCIRMS) has led to a virtual explosion in application of this technique not only in petroleum explora...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.1469M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.1469M"><span id="translatedtitle">An improved pyrite pretreatment protocol for kinetic and <span class="hlt">isotopic</span> <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mirzoyan, Natella; Kamyshny, Alexey; Halevy, Itay</p> <p>2014-05-01</p> <p>An improved pyrite pretreatment protocol for kinetic and <span class="hlt">isotopic</span> <span class="hlt">studies</span> Natella Mirzoyan1, Alexey Kamyshny Jr.2, Itay Halevy1 1Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel 2Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively <span class="hlt">studied</span> in various experimental investigations of the kinetics of its dissolution and oxidation, the <span class="hlt">isotopic</span> fractionations associated with these reactions, and the microbiological processes involved. Pretreatment of pyrite for removal of oxidation impurities to prevent experimental artifacts and inaccuracies is often practiced. While numerous pyrite-cleaning methods have been used in experiments, a common pyrite pretreatment method, often used to investigate pyrite chemistry by the <span class="hlt">isotopic</span> fractionations associated with it, includes several rinses by HCl, acetone and deionized water. Elemental sulfur (S0) is a common product of incomplete pyrite oxidation. Removal of S0 is desirable to avoid experimental biases associated with its participation in pyrite transformations, but is more complicated than the removal of sulfate. Although rinsing with an organic solvent is in part aimed at removing S0, to the best of our knowledge, the extraction efficiency of S0 in existing protocols has not been assessed. We have developed and tested a new protocol for elemental sulfur removal from the surface of pyrite by ultrasonication with warm acetone. Our data demonstrate the presence of large fractions of S0 on untreated pyrite particle surfaces, of which only approximately 60% was removed by the commonly used pretreatment method. The new protocol described here was found to be more efficient at S0 removal than the commonly used method</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.426...23D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.426...23D"><span id="translatedtitle">Combined petrological, geochemical and <span class="hlt">isotopic</span> modeling of a plume source: Example of Gambier Island, Pitcairn chain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delavault, Hélène; Chauvel, Catherine; Sobolev, Alexander; Batanova, Valentina</p> <p>2015-09-01</p> <p>Mantle plumes have been increasingly <span class="hlt">studied</span> in the past years, yet they remain not well understood. While geophysical approaches attempt to locate the depth of sources, petrological approaches characterize the nature of the materials that melt and geochemical approaches trace their history and origin. However, combined <span class="hlt">studies</span> remain rare while they could provide strong constraints on the processes that give rise to mantle plumes. Here we present a new model that combines petrological and geochemical approaches to constrain the nature of source materials, their temperature of melting, their composition and their age. We focus on Gambier Island, Pitcairn chain in Polynesia because it has the advantage of combining two important features, (a) most lavas are tholeiites, a necessary feature to perform an accurate petrological modeling that can be compared to other plumes and (b) it belongs to the Pitcairn Chain, whose composition varies through time and samples today the extreme EM1-type source. We present geochemical analyses as well as <span class="hlt">Sr-Nd</span>-Pb-Hf <span class="hlt">isotopes</span> of lavas and high-precision olivine analyses. Using in situ olivine analyses and REE modeling, we constrain the composition of the mantle source (5% recycled oceanic crust - 95% peridotite), how both components melt (25-30% versus 0.5-1.5%) and we estimate the temperature of Gambier source at about 1400 °C, a rather low temperature compared to Hawaii for example. We also constrain both the age and the nature of the recycled material using the <span class="hlt">isotopic</span> data. They require the presence of about 3% sediment associated to recycled basalt in the pyroxenitic component and its age is about 1.5 Gyr. We also attribute the marked Nb-Ta positive anomalies and the elevated Ce/Pb ratios to the presence of recycled basalt in the mantle source. These features resemble typical HIMU lavas but the younger age of the recycled material together with the presence of sediment in the plume source explains the lower Pb <span class="hlt">isotopic</span> ratios</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040089515&hterms=eukaryotic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Deukaryotic','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040089515&hterms=eukaryotic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Deukaryotic"><span id="translatedtitle">An <span class="hlt">isotopic</span> biogeochemical <span class="hlt">study</span> of the Green River oil shale</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Collister, J. W.; Summons, R. E.; Lichtfouse, E.; Hayes, J. M.</p> <p>1992-01-01</p> <p>Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented <span class="hlt">study</span> of the Shell 22x-l well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon <span class="hlt">isotopic</span> compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (delta approximately -30% vs PDB), products of methanotrophic bacteria (delta approximately -85%), and products of unknown bacteria (delta approximately -40%). For individual compounds synthesized by primary producers, delta-values ranged from -28 to -32%. 13C contents of individual primary products (beta-carotane, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting diverse origins for these materials. 13C contents of numerous hopanoids were inversely related to sulfur abundance, indicating that they derived both from methanotrophs and from other bacteria, with abundances of methanotrophs depressed when sulfur was plentiful in the paleoenvironment. gamma-Cerane coeluted with 3 beta(CH3),17 alpha(H),21 beta(H)-hopane, but delta-values could be determined after deconvolution. gamma-Cerane (delta approximately -25%) probably derives from a eukaryotic heterotroph grazing on primary materials, the latter compound (delta approximately -90%) must derive from methanotrophic organisms. 13C contents of n-alkanes in bitumen differed markedly from those of paraffins generated pyrolytically. <span class="hlt">Isotopic</span> and quantitative relationships suggest that alkanes released by pyrolysis derived from a resistant biopolymer of eukaryotic origin and that this was a dominant constituent of total organic carbon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11540064','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11540064"><span id="translatedtitle">An <span class="hlt">isotopic</span> biogeochemical <span class="hlt">study</span> of the Green River oil shale.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Collister, J W; Summons, R E; Lichtfouse, E; Hayes, J M</p> <p>1992-12-01</p> <p>Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented <span class="hlt">study</span> of the Shell 22x-l well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon <span class="hlt">isotopic</span> compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (delta approximately -30% vs PDB), products of methanotrophic bacteria (delta approximately -85%), and products of unknown bacteria (delta approximately -40%). For individual compounds synthesized by primary producers, delta-values ranged from -28 to -32%. 13C contents of individual primary products (beta-carotane, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting diverse origins for these materials. 13C contents of numerous hopanoids were inversely related to sulfur abundance, indicating that they derived both from methanotrophs and from other bacteria, with abundances of methanotrophs depressed when sulfur was plentiful in the paleoenvironment. gamma-Cerane coeluted with 3 beta(CH3),17 alpha(H),21 beta(H)-hopane, but delta-values could be determined after deconvolution. gamma-Cerane (delta approximately -25%) probably derives from a eukaryotic heterotroph grazing on primary materials, the latter compound (delta approximately -90%) must derive from methanotrophic organisms. 13C contents of n-alkanes in bitumen differed markedly from those of paraffins generated pyrolytically. <span class="hlt">Isotopic</span> and quantitative relationships suggest that alkanes released by pyrolysis derived from a resistant biopolymer of eukaryotic origin and that this was a dominant constituent of total organic carbon. PMID:11540064</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983GeCoA..47.2015M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983GeCoA..47.2015M"><span id="translatedtitle"><span class="hlt">Isotopic</span> and incompatible element constraints on the genesis of island arc volcanics from Cold Bay and Amak Island, Aleutians, and implications for mantle structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, J. D.; Hart, S. R.</p> <p>1983-11-01</p> <p>Cold Bay and Amak Island, two Quaternary volcanic centers in the eastern Aleutians, are orthogonal relative to the trench and separated by ~50 km. <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopic</span> compositions of the calc-alkaline andesite magmas show no sign of contamination from continental crust (average 87Sr /86Sr = 0.70323 , 143Nd /144Nd = 0.51301 , 206Pb /204Pb = 18.82 , 207Pb /204Pb = 15.571 ). These samples plot within the mantle arrays for <span class="hlt">Sr-Nd</span> and for Pb and are similar to arcs such as the Marianas and New Britain (<span class="hlt">Sr-Nd</span>) and Marianas and Tonga (Pb). Incompatible element ratios for the Aleutian andesites (K/Rb ~ 332, K/Cs ~ 10,600, K/Sr ~ 22.4, K/Ba ~ 18.3, Ba/La ~ 60) are within the range reported for arc basalts, despite the difference in degree of fractionation. Average K content, K/Rb, K/Ba and K/Sr are approximately the same for basalts from arcs and from oceanic islands (OIB); K/Cs is a factor of 4 lower and Ba/La almost 3 times higher in arcs. Abundance ratio correlations indicate that arcs are enriched in Cs and depleted in La relative to OIB, with other incompatible element abundances very similar. Histograms of Sr and Nd <span class="hlt">isotopic</span> compositions for MORB, OIB, and intraoceanic arcs show remarkably similar peaks and distribution patterns for intraoceanic arcs and OIB. A "plum pudding" model for the upper mantle best accommodates a) geochemical coherence of OIB and IAV, b) the existence of mantle plumes at some oceanic islands, and c) the presence of a MORB-type source at back arc spreading centers. In this model, OIB plums are imbedded in a MORB matrix; small degrees of melting generate OIB-type magmas while larger degrees of melting dilute the OIB magma with MORB matrix melts. OIB plums are merely less robust lower mantle plumes ( i.e., blobs) which are distributed throughout the upper mantle by convection. The existence of at least two types of OIB, as indicated by <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotopes</span>, suggests that nuggets of recycled oceanic lithosphère may coexist with lower</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/113824','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/113824"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">studies</span> of Yucca Mountain soil fluids and carbonate pedogenesis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McConnaughey, T.A.; Whelan, J.F.; Wickland, K.P.; Moscati, R.J.</p> <p>1994-12-31</p> <p>Secondary carbonates occurring within the soils, faults, and subsurface fractures of Yucca Mountain contain some of the best available records of paleoclimate and palehydrology for the potential radioactive waste repository site. This article discusses conceptual and analytical advances being made with regard to the interpretation of stable <span class="hlt">isotope</span> data from pedogenic carbonates, specifically related to the {sup 13}C content of soil CO{sub 2}, CaCO{sub 3}, precipitation mechanisms, and <span class="hlt">isotopic</span> fractionations between parent fluids and precipitating carbonates. The {sup 13}C content of soil carbon dioxide from Yucca Mountain and vicinity shows most of the usual patterns expected in such contexts: Decreasing {sup 13}C content with depth decreasing {sup 13}C with altitude and reduced {sup 13}C during spring. These patterns exist within the domain of a noisy data set; soil and vegetational heterogeneities, weather, and other factors apparently contribute to <span class="hlt">isotopic</span> variability in the system. Several soil calcification mechanisms appear to be important, involving characteristic physical and chemical environments and <span class="hlt">isotopic</span> fractionations. When CO{sub 2} loss from thin soil solutions is an important driving factor, carbonates may contain excess heavy <span class="hlt">isotopes</span>, compared to equilibrium precipitation with soil fluids. When root calcification serves as a proton generator for plant absorption of soil nutrients, heavy <span class="hlt">isotope</span> deficiencies are likely. Successive cycles of dissolution and reprecipitation mix and redistribute pedogenic carbonates, and tend to <span class="hlt">isotopically</span> homogenize and equilibrate pedogenic carbonates with soil fluids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20006272','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20006272"><span id="translatedtitle">Dynamics of the Galapagos hotspot from helium <span class="hlt">isotope</span> geochemistry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kurz, M.D.; Geist, D.</p> <p>1999-12-01</p> <p>The authors have measured the <span class="hlt">isotopes</span> of He, <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb in a number of lava flows from the Galapagos Archipelago; the main goal is to use magmatic helium as a tracer of plume influence in the western volcanoes. Because the Galapagos lava flows are so well preserved, it is also possible to measure surface exposure ages using in situ cosmic-ray-produced {sup 3}He. The exposure ages range from {lt}0.1 to 580 Ka, are consistent with other chronological constrains, and provide the first direct dating of these lava flows. The new age data demonstrate the utility of the technique in this important age range and show that the western Galapagos volcanoes have been erupting distance compositions simultaneously for the last {approximately}10 Ka. The magmatic {sup 3}He/{sup 4}He ratios range from 6.0 to 27 times atmospheric (R{sub a}), with the highest values found on the islands of Isabella (16.8 R{sub a} for Vulcan Sierra Negra) and Fernandina (23 to 27 R{sub a}). Values from Santa Cruz are close to typical mid-ocean ridge basalt values (MORB, of {approximately}9 R{sub 2}) and Pinta has a {sup 3}He/{sup 4}He ratio lower than MORB (6.9 R{sub a}). These data confirm that the plume is centered beneath Fernandina which is the most active volcano in the archipelago and is at the leading edge of plate motion. The data are consistent with previous <span class="hlt">isotopic</span> <span class="hlt">studies</span>, confirming extensive contributions from depleted asthenospheric or lithospheric mantle sources, especially to the central islands. The most striking aspect of the helium <span class="hlt">isotopic</span> data is that the {sup 3}He/{sup 4}He ratios decrease systematically in all directions from Fernandina. This spatial variability is assumed to reflect the contribution of the purest plume component to Fernandina magmatism, and shows that helium is a sensitive indicator of plume influence. The highest {sup 3}He/{sup 4}He ratios are found in volcanoes with lowest Na{sub 2}O(8) and FeO(8), which may relate to source composition as well as degree</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhDT.......361S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhDT.......361S"><span id="translatedtitle">Surface <span class="hlt">studies</span> of metals after interaction with hydrogen <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silver, David Samuel</p> <p>1998-12-01</p> <p>The objective of this research is to characterize surfaces of metals after interaction with hydrogen <span class="hlt">isotopes</span>. Iron, which does not readily bond with hydrogen, and palladium, which strongly bonds with hydrogen, were <span class="hlt">studied</span>. Observations of surfaces are used to determine the nature of their metamorphosis due to such exposures. An experimental <span class="hlt">study</span> of pure iron foil (99.99%) exposed to a hot, dense hydrogen and argon gas mixture in a ballistic compressor yielded evidence for new structural and compositional changes of the metal due to the exposure. Atomic force microscope (AFM) <span class="hlt">studies</span> demonstrated surfaces to be highly uneven, where height variations were often 2 mum for many micron-sized regions scanned. An iron foil exposed to argon gases alone revealed unique dendritic patterns but negligible height variations for micron-size scans. A cold rolled single crystal palladium cathode was electrolyzed in a solution of Dsb2O and 15% Hsb2SOsb4 by volume for 12 minutes. The cathode bent toward the anode during electrolysis. Examination of both concave and convex surfaces using the scanning electron microscope (SEM), scanning tunneling microscope (STM), and AFM revealed rimmed craters with faceted crystals inside and multi-textured surfaces. Also pairs of cold rolled polycrystalline palladium cathodes underwent electrolysis for six minutes or less, in Dsb2O and Hsb2O solutions, each solution containing 15% Hsb2SOsb4, by volume. Surface morphologies of the heavy water electrolyzed samples revealed asperities, craters, and nodules, and evidence of recrystallization and crystal planes. After 1.5 years, new AFM <span class="hlt">studies</span> of the same Pd surfaces exposed to heavy water electrolyte exhibited loose, nanometer-sized particles. However, the surfaces of Pd cathodes exposed to light water electrolyte remained nearly identical to morphologies of foils not electrolyzed, and did not change with time. No surface asperities or loose grains were observed on the latter. Secondary ion mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880036224&hterms=swan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dswan','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880036224&hterms=swan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dswan"><span id="translatedtitle"><span class="hlt">Study</span> of the <span class="hlt">isotopic</span> features of Swan bands in comets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krishna Swamy, K. S.</p> <p>1987-01-01</p> <p>It is shown from a detailed statistical equilibrium calculation of the (C-12)(C-13) molecule that the interpretation of the observed intensities of Swan bands of the normal and the <span class="hlt">isotopic</span> molecule of C2 in terms of the abundance ratio of C-12 and C-13 is a reasonable one. The synthetic profile of some <span class="hlt">isotopic</span> features in the (0.0) Swan band is compared with the observed profiles for comet West.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26446900','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26446900"><span id="translatedtitle">Application of non-traditional stable <span class="hlt">isotopes</span> in analytical ecogeochemistry assessed by MC ICP-MS--A critical review.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Irrgeher, Johanna; Prohaska, Thomas</p> <p>2016-01-01</p> <p>Analytical ecogeochemistry is an evolving scientific field dedicated to the development of analytical methods and tools and their application to ecological questions. Traditional stable <span class="hlt">isotopic</span> systems have been widely explored and have undergone continuous development during the last century. The variations of the <span class="hlt">isotopic</span> composition of light elements (H, O, N, C, and S) have provided the foundation of stable <span class="hlt">isotope</span> analysis followed by the analysis of traditional geochemical <span class="hlt">isotope</span> tracers (e.g., Pb, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Hf). Questions in a considerable diversity of scientific fields have been addressed, many of which can be assigned to the field of ecogeochemistry. Over the past 15 years, other stable <span class="hlt">isotopes</span> (e.g., Li, Zn, Cu, Cl) have emerged gradually as novel tools for the investigation of scientific topics that arise in ecosystem research and have enabled novel discoveries and explorations. These systems are often referred to as non-traditional <span class="hlt">isotopes</span>. The small <span class="hlt">isotopic</span> differences of interest that are increasingly being addressed for a growing number of <span class="hlt">isotopic</span> systems represent a challenge to the analytical scientist and push the limits of today's instruments constantly. This underlines the importance of a metrologically sound concept of analytical protocols and procedures and a solid foundation of data processing strategies and uncertainty considerations before these small <span class="hlt">isotopic</span> variations can be interpreted in the context of applied ecosystem research. This review focuses on the development of <span class="hlt">isotope</span> research in ecogeochemistry, the requirements for successful detection of small <span class="hlt">isotopic</span> shifts, and highlights the most recent and innovative applications in the field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/wri/1995/4213/report.pdf','USGSPUBS'); return false;" href="http://pubs.usgs.gov/wri/1995/4213/report.pdf"><span id="translatedtitle">An <span class="hlt">isotope</span> hydrology <span class="hlt">study</span> of the Kilauea volcano area, Hawaii</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Scholl, M.A.; Ingebritsen, S.E.; Janik, C.J.; Kauahikaua, J.P.</p> <p>1995-01-01</p> <p><span class="hlt">Isotope</span> tracer methods were used to determine flow paths, recharge areas, and relative age for ground water in the Kilauea volcano area on the Island of Hawaii. Stable <span class="hlt">isotopes</span> in rainfall show three distinct <span class="hlt">isotopic</span> gradients with elevation, which are correlated with trade-wind, rain shadow, and high-elevation climatological patterns. Temporal variations in <span class="hlt">isotopic</span> composition of precipitation are controlled more by the frequency of large storms than b.y seasonal temperature fluctuations. Consistency in results between two separate areas with rainfall caused by tradewinds and thermally-driven upslope airflow suggests that <span class="hlt">isotopic</span> gradients with elevation may be similar on other islands in the tradewind belt, especially the other Hawaiian Islands, which have similar climatology and temperature lapse rates. Areal contrasts in ground-water stable <span class="hlt">isotopes</span> and tritium indicate that the volcanic ri~ zones compartmentalize the regional ground-water system. Tritium levels in ground water within and downgradient of Kilauea's ri~ zones indicate relatively long residence times. Part of Kilauea's Southwest Ri~ Zone appears to act as a conduit for water from higher elevation, but there is no evidence for extensive down-ri~ flow in the lower East Ri~ Zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....9219V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....9219V"><span id="translatedtitle">Evolution of the Cretaceous magmatism in the Apuseni-Timok-Srednogorie metallogenic belt and implications for the geodynamic reconstructions: new insight from geochronology, geochemistry and <span class="hlt">isotope</span> <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>von Quadt, A.; Peytcheva, I.; Heinrich, C. A.; Frank, M.; Cvetkovic, V.</p> <p>2003-04-01</p> <p> magmatic pulses (< 1.Ma) led to several important Cu-Au-PGE ore deposits within the Central Srednogorie zone. <span class="hlt">Sr</span>-, <span class="hlt">Nd</span>-, Pb- and Hf-<span class="hlt">isotope</span> tracing on whole rocks and minerals provides evidence for mixed crust-mantle origin of the magma with specific trends in the single deposits. Presented data suggest subduction related magmatism in the Upper Cretaceous with subduction rollback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080009707','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080009707"><span id="translatedtitle">Coordinated Chemical and <span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of GEMS in IDPS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Keller, L. P.; Messenger, S.</p> <p>2008-01-01</p> <p>Cometary IDPs contain a record of the building blocks of the solar system including presolar grains, molecular cloud material, and materials formed in the early solar nebula [1]. Following their accretion, these materials have remained relatively unaltered because of the lack of parent body hydrothermal alteration. We are using coordinated transmission electron microscope (TEM) and ion microprobe <span class="hlt">studies</span> to establish the origins of the various components within cometary IDPs. Of particular interest is the nature and abundance of presolar silicates in these IDPs because astronomical observations suggest that crystalline and amorphous silicates are the dominant grain types produced in young main sequence stars and evolved O-rich stars [e.g. 2]. Amorphous silicates (in the form of GEMS grains) are a major component of cometary IDPs and so a major objective of this work is to elucidate their origins. In rare cases, GEMS grains have highly anomalous O <span class="hlt">isotopic</span> compositions that establish their origins as circumstellar condensates [3]. Here we present data on a systematic <span class="hlt">study</span> of the silicate components within a primitive IDP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=87414&keyword=Composite+AND+restoration&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=68447716&CFTOKEN=52881599','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=87414&keyword=Composite+AND+restoration&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=68447716&CFTOKEN=52881599"><span id="translatedtitle">COMPOUND-SPECIFIC <span class="hlt">ISOTOPE</span> ANALYSIS OF MTBE AND TBA FOR BIOREMEDIATION <span class="hlt">STUDIES</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The utility of stable <span class="hlt">isotope</span> ratios to detect biodegradation for a number of chemical compounds including MTBE and TBA has been demonstrated in a number of laboratory or field <span class="hlt">studies</span>. Chemical reactions tend to favor molecules with the lighter <span class="hlt">isotopic</span> species (e.g., 12C, 1H), ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V23B3124M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V23B3124M"><span id="translatedtitle">Zircon-apatite U-Pb geochronology, zircon Hf <span class="hlt">isotope</span> composition and geochemistry of granite batholith in the northern Mexico: Implications for Tectonomagmatic evolution of southern Cordillera.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahar, M. A.; Goodell, P.</p> <p>2015-12-01</p> <p>We present the zircon-apatite U-Pb ages and zircon Hf <span class="hlt">isotope</span> composition of the granite batholith exposed at the western boundary of Chihuahua. Granidiorite samples were analyzed from both, north and south of the Rio El Fuerte and Sinforosa Lineament. Based on previous <span class="hlt">studies</span>, the WWN-EES trending Sinforosa Lineament is proposed as the manifestation of a terrane boundary between Seri in the north and Tahue terrane in the south. Zircon U-Pb data indicate that the magmatism spans a time period of 36 Ma from 89 to 53 Ma to the north of the Sinforosa Lineament while granodiorites in the south of the Sinforosa Lineament are dated at 59 Ma. The U-Pb apatite ages are variable in the north of the Sinforosa Lineament and range from 86-51 Ma. These apatite dates are 1-28 Ma younger than the corresponding zircon U-Pb crystallization ages. This indicates variable cooling rates and moderate to shallow emplacement. In contrast, in the south of the Sinforosa Lineament, the U-Pb apatite ages (64-59 Ma) are indistinguishable from the zircon U-Pb age (59 Ma), indicating rapid cooling and shallow emplacement. Zircon morphology and U-Pb dating revealed the absence of inherited component in the zircon ages, as no inheritance of any age has been observed. Most of the northwestern Mexico is underlain by Precambrian-Paleozoic-Jurassic basement. However, in the <span class="hlt">study</span> area, U-Pb dating does not support the involvement of the older basement in generating the granite magmas. The weighted mean initial ɛHf (t) <span class="hlt">isotope</span> composition of granodiorites on both sides of the Sinforosa Lineament varies from +2 to +5. However, Hf <span class="hlt">isotope</span> composition in the south of the Sinforosa Lineament is more heterogeneous and relatively evolved with weighted Mean ɛHf (t) = +1.45. The Hf <span class="hlt">isotope</span> composition is consistent with the previously reported near bulk silicate <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> values. We suggest that the magmatic rocks in this region are not derived from melting of a felsic older crust beneath the batholith</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A23C0306W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A23C0306W"><span id="translatedtitle">Reconstruction of Sothern Ocean dust fluxes and dust provenance areas at highest spatial resolution: implications from 230Thxs, <span class="hlt">isotopic</span> and REE data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wengler, M.; Lamy, F.; Geibert, W.; Pahnke, K.; Kuhn, G.; Gersonde, R.; Tiedemann, R.</p> <p>2015-12-01</p> <p>The <span class="hlt">study</span> of dust fluxes in the Southern Ocean (SO) is crucial to understand processes and feedback mechanisms in the SO since atmospheric dust is considered to play a key role in past atmospheric CO2 variability by affecting the marine biological production through iron fertilization. We present 230Thxs, <span class="hlt">isotopic</span> (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb) and REE data of numerous surface samples across the Pacific sector of the SO in order to determine lithogenic mass accumulation rates (MAR) (corrected for sediment focusing) and possible dust provenance areas. Our MAR data display highest values near New Zealand´s east coast (South Island), however this may not reflect a pure Australian/New Zealand dust signal due to a strong influence of fluvial sediment input from New Zealand sources. In contrast, we interpret the open ocean MAR values as derived from the Australian/New Zealand dust plume, which might reach as far east as ~100° W. The highest MAR values among the open ocean samples are found south of the winter sea ice front (WSI), and likely reflect the admixture of ice rafted debris (IRD). Further east of ~100° W, the MAR data exceed the open ocean samples by up to a factor of ~6, consistent with predominating terrigenous input from southernmost Patagonia and Antarctica. Combining the MAR data set with provenance sensitive proxies (<span class="hlt">isotopic</span> and REE data) enables us to identify at least 3 different possible provenance areas (Australia/New Zealand, Antarctica and Patagonia) and to reconstruct the possible pathway of the Australian/New Zealand dust plume. Since the atmospheric circulation (westerly winds) is one controlling factor influencing the distribution of dust over the SO this data set also allows us to infer variations of wind speed and strength of the westerly wind belt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/171305','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/171305"><span id="translatedtitle">Feasibility <span class="hlt">study</span> of medical <span class="hlt">isotope</span> production at Sandia National Laboratories</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Massey, C.D.; Miller, D.L.; Carson, S.D.</p> <p>1995-12-01</p> <p>In late 1994, Sandia National Laboratories in Albuquerque, New Mexico, (SNL/NM), was instructed by the Department of Energy (DOE) <span class="hlt">Isotope</span> Production and Distribution Program (IPDP) to examine the feasibility of producing medically useful radioisotopes using the Annular Core Research Reactor (ACRR) and the Hot Cell Facility (HCF). Los Alamos National Laboratory (LANL) would be expected to supply the targets to be irradiated in the ACRR. The intent of DOE would be to provide a capability to satisfy the North American health care system demand for {sup 99}Mo, the parent of {sup 99m}Tc, in the event of an interruption in the current Canadian supply. {sup 99m}Tc is used in 70 to 80% of all nuclear medicine procedures in the US. The goal of the SNL/NM <span class="hlt">study</span> effort is to determine the physical plant capability, infrastructure, and staffing necessary to meet the North American need for {sup 99}Mo and to identify and examine all issues with potential for environmental impact.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25685410','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25685410"><span id="translatedtitle"><span class="hlt">Isotope</span> effects of neodymium in different ligands exchange systems <span class="hlt">studied</span> by ion exchange displacement chromatography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ismail, Ibrahim; Fawzy, Ahmed S; Ahmad, Mohammad I; Aly, Hisham F; Nomura, Masao; Fujii, Yasuhiko</p> <p>2013-03-01</p> <p>The <span class="hlt">isotope</span> effects of neodymium in Nd-glycolate ligand exchange system were <span class="hlt">studied</span> by using ion exchange chromatography. The separation coefficients of neodymium <span class="hlt">isotopes</span>, ε's, were calculated from the observed <span class="hlt">isotopic</span> ratios at the front and rear boundaries of the neodymium adsorption band. The values of separation coefficients of neodymium <span class="hlt">isotopes</span>, ε's, for the Nd-glycolate ligand exchange system were compared with those of Nd-malate and Nd-citrate, which indicated that the <span class="hlt">isotope</span> effects of neodymium as <span class="hlt">studied</span> by the three ligands takes the following direction Malate > Citrate > Glycolate. This order agrees with the number of available sites for complexation of each ligand. The values of the plate height, HETP of Nd in Nd-ligand exchange systems were also calculated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021409','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021409"><span id="translatedtitle">Oxygen and iron <span class="hlt">isotope</span> <span class="hlt">studies</span> of magnetite produced by magnetotactic bacteria</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Mandernack, K.W.; Bazylinski, D.A.; Shanks, Wayne C.; Bullen, T.D.</p> <p>1999-01-01</p> <p>A series of carefully controlled laboratory <span class="hlt">studies</span> was carried out to investigate oxygen and iron <span class="hlt">isotope</span> fractionation during the intracellular production of magnetite (Fe3O4) by two different species of magnetotactic bacteria at temperatures between 4??and 35??C under microaerobic and anaerobic conditions. No detectable fractionation of iron <span class="hlt">isotopes</span> in the bacterial magnetites was observed. However, oxygen <span class="hlt">isotope</span> measurements indicated a temperature-dependent fractionation for Fe3O4 and water that is consistent with that observed for Fe3O4 produced extracellularly by thermophilic Fe3+-reducing bacteria. These results contrast with established fractionation curves estimated from either high-temperature experiments or theoretical calculations. With the fractionation curve established in this report, oxygen-18 <span class="hlt">isotope</span> values of bacterial Fe3O4 may be useful in paleoenvironmental <span class="hlt">studies</span> for determining the oxygen-18 <span class="hlt">isotope</span> values of formation waters and for inferring paleotemperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/83399','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/83399"><span id="translatedtitle">NMR <span class="hlt">studies</span> of two spliced leader RNAs using <span class="hlt">isotope</span> labeling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lapham, J.; Crothers, D.M.</p> <p>1994-12-01</p> <p>Spliced leader RNAs are a class of RNA molecules (<200 nts) involved in the trans splicing of messenger RNA found in trypanosomes, nematodes, and other lower eukaryotes. The spliced leader RNA from the trypanosome Leptomonas Collosoma exists in two alternate structural forms with similar thermal stabilities. The 54 nucleotides on the 5{prime} end of the SL molecule is structurally independent from the 3{prime} half of the RNA, and displays the two structural forms. Furthermore, the favored of the two structures was shown to contain anomalous nuclease sensitivity and thermal stability features, which suggests that there may be tertiary interactions between the splice site and other nucleotides in the 5{prime} end. Multidimensional NMR <span class="hlt">studies</span> are underway to elucidate the structural elements present in the SL RNAs that give rise to their physical properties. Two spliced leader sequences have been <span class="hlt">studied</span>. The first, the 54 nucleotides on the 5{prime} end of the L. Collosoma sequence, was selected because of earlier <span class="hlt">studies</span> in our laboratory. The second sequence is the 5{prime} end of the trypanosome Crithidia Fasciculata, which was chosen because of its greater sequence homology to other SL sequences. Given the complexity of the NMR spectra for RNA molecules of this size, we have incorporated {sup 15}N/{sup 13}C-labeled nucleotides into the RNA. One of the techniques we have developed to simplify the spectra of these RNA molecules is <span class="hlt">isotope</span> labeling of specific regions of the RNA. This has been especially helpful in assigning the secondary structure of molecules that may be able to adopt multiple conformations. Using this technique one can examine a part of the molecule without spectral interference from the unlabeled portion. We hope this approach will promote an avenue for <span class="hlt">studying</span> the structure of larger RNAs in their native surroundings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.U14A..04P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.U14A..04P"><span id="translatedtitle">Mixing the mantle marble-cake: timescale constraints from Os <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parman, S.; Pearson, G.; Nowell, G.; van Hunen, J.</p> <p>2007-12-01</p> <p>In their seminal paper, Allegre and Turcotte (1986) presented a model in which the upper mantle is a mixture of depleted, harzburgitic mantle and subducted basalt that has been mechanically mixed together, the mantle marble-cake. Since their publication, most <span class="hlt">studies</span> of mantle heterogeneity have focused on the enriched components, which are equated with subducted basalt and/or sediments, and successfully explain OIB <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopic</span> systematics. In this talk, we will focus on a different part of the marble-cake, depleted (harzburgitic) heterogeneities. Though abundant in abyssal peridotites and ophiolites, these have been difficult to <span class="hlt">study</span> geochemically because they have very low concentrations of typical trace elements and radiogenic <span class="hlt">isotopes</span>, and are overprinted by any mixing with enriched mantle or melts. However, Os is compatible during mantle melting, is enriched in depleted mantle and thus is robust with respect to mixing with enriched components or metasomatism. Somewhat surprisingly, Os <span class="hlt">isotope</span> <span class="hlt">studies</span> of the convecting mantle show clear evidence for depleted heterogeities up to 2 billion years old, but the relative paucity of data (less than 100 analyses), makes it difficult to extract meaningful mixing information. Rapid analysis of osmiridium grains by laser-ablation inductively coupled multi-collector plasma mass spectrometry now allows large Os datasets to be acquired (100s of datapoints), which are suitable for statistical analyses (Meibom, 2002). Here we present new and published laser-ablation analyses of osmiridiums from a global collection. The data generally show an exponential decrease in heterogeneities with age, such that over 90% of heterogeneities are destroyed within 2 billion years, though rare heterogeneities as old as 2.7 Ga survive. The exponential decrease in survivorship is generally consistent with the mechanical mixing model of Allegre & Turcotte (1986). Subsequent 2-dimensional mixing models suggest that high-viscosity blobs can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6353975','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6353975"><span id="translatedtitle">Sr <span class="hlt">isotopic</span> tracer <span class="hlt">study</span> of the Samail ophiolite, Oman</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lanphere, M.A.; Coleman, R.G.; Hopson, C.A.</p> <p>1981-04-10</p> <p>We have measured Rb and Sr concentrations and Sr <span class="hlt">isotopic</span> compositions in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite diabase dikes, and gabbro and websterite dikes within the metamorphic peridotite. Ten samples of cummulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have mean /sup 87/Sr//sup 86/Sr ratios and standard deviations of 0.70314 +- 0.00030 and 0.70306 +- 0.00034, respectively. The dispersion in Sr <span class="hlt">isotopic</span> composition may reflect real heterogeneities in the magma source region. The average Sr <span class="hlt">isotopic</span> composition of cumulate gabbro falls in the range of <span class="hlt">isotopic</span> compositions of modern midocean ridge basalt. The /sup 87/Sr//sup 86/Sr ratios of noncumulate gabbro, plagiogranite, and diabase dikes range from 0.7034 to 0.7047, 0.7038 to 0.7046, and 0.7037 to 0.7061, respectively. These higher /sup 87/Sr//sup 86/Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with seawater. Mineral separates from dikes that cut harzburgite tectonite have Sr <span class="hlt">isotopic</span> compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dikes were derived from partial melting of source regions that had similar long-term histories and chemical compositions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70011691','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70011691"><span id="translatedtitle">Sr <span class="hlt">isotopic</span> tracer <span class="hlt">study</span> of the Samail ophiolite, Oman.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lanphere, M.A.; Coleman, R.G.; Hopson, C.A.</p> <p>1981-01-01</p> <p>Rb and Sr concentrations and Sr-<span class="hlt">isotopic</span> compositions were measured in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite, diabase dykes, and gabbro and websterite dykes within the metamorphic peridotite. Ten samples of cumulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have 87Sr/86Sr ratios of 0.70314 + or - 0.00030 and 0.70306 + or - 0.00034, respectively. The dispersion in Sr- <span class="hlt">isotopic</span> composition may reflect real heterogeneities in the magma source region. The average Sr-<span class="hlt">isotopic</span> composition of cumulate gabbro falls in the range of <span class="hlt">isotopic</span> compositions of modern MORB. The 87Sr/86Sr ratios of noncumulate gabbro, plagiogranite, and diabase dykes range 0.7034-0.7047, 0.7038-0.7046 and 0.7037- 0.7061, respectively. These higher 87Sr/86Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with sea-water. Mineral separates from dykes that cut harzburgite tectonite have Sr-<span class="hlt">isotopic</span> compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dykes were derived from partial melting of source regions that had similar long-term histories and chemical compositions.-T.R.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21499256','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21499256"><span id="translatedtitle">Collectivity in the light xenon <span class="hlt">isotopes</span>: A shell model <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Caurier, E.; Nowacki, F.; Sieja, K.; Poves, A.</p> <p>2010-12-15</p> <p>The lightest xenon <span class="hlt">isotopes</span> are <span class="hlt">studied</span> in the shell model framework, within a valence space that comprises all the orbits lying between the magic closures N=Z=50 and N=Z=82. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) N=Z nucleus {sup 108}Xe. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the 0h{sub 11/2} orbit. We also have <span class="hlt">studied</span> the effect of the excitations from the {sup 100}Sn core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the 0h{sub 11/2} orbit. In the N=Z case, one neutron and one proton align to J=11 and T=0. In {sup 110,112}Xe the alignment begins in the J=10, T=1 channel and it is dominantly of neutron-neutron type. Approaching the band termination the alignment of a neutron-proton pair to J=11 and T=0 takes over. In a more academic mood, we have <span class="hlt">studied</span> the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of {sup 108,110}Xe and examined the possible existence of isovector and isoscalar pairing condensates in these N{approx}{approx}Z nuclei.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007EOSTr..88..537A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007EOSTr..88..537A"><span id="translatedtitle">New Capabilities for <span class="hlt">Studies</span> Using <span class="hlt">Isotopes</span> in the Water Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aggarwal, Pradeep K.; Alduchov, Oleg; Araguás, Luis Araguás; Dogramaci, Shawan; Katzlberger, Gernot; Kriz, Karel; Kulkarni, Kshitij M.; Kurttas, Türker; Newman, Brent D.; Pucher, Alexander</p> <p>2007-12-01</p> <p>The characterization and quantification of hydrological fluxes within components of the water cycle and across interfaces (e.g., atmosphere/land surface, aquifer/river, soil/plant) are critical for assessing and managing water resources and for understanding the impacts of climate change and variability on the hydrological cycle. Stable <span class="hlt">isotopes</span> of oxygen and hydrogen, and radioactive <span class="hlt">isotopes</span> such as tritium and carbon-14, provide unique insights into hydrological and climatic processes at local, regional, and global scales, including the role of groundwater in rivers and lakes, groundwater recharge rates, and sources and recycling rates of atmospheric moisture [Aggarwal et al., 2005; Gat, 1996; Kendall and McDonnell, 1998]. <span class="hlt">Isotopes</span> also provide critical insights into understanding feedbacks and interactions between physical and biological processes (e.g., ecohydrology).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22109404','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22109404"><span id="translatedtitle">Experimental stand for <span class="hlt">studies</span> of hydrogen <span class="hlt">isotopes</span> permeation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brad, S.; Stefanescu, I.; Stefan, L.; Lazar, A.; Vijulie, M.; Sofilca, N.; Bornea, A.; Vasut, F.; Zamfirache, M.; Bidica, N.; Postolache, C.; Matei, L.</p> <p>2008-07-15</p> <p>As a result of the high probability of hydrogen <span class="hlt">isotope</span> permeation through materials used in high-temperature reactor operations, the interaction of hydrogen <span class="hlt">isotopes</span> with metallic structural materials proposed to be used for fusion reactor designing is of great importance for safety considerations. Determining the parameters of the interaction between hydrogen <span class="hlt">isotopes</span> and different materials, is therefore essential to accurately calculate recycling, outgassing, loading, permeation and hydrogen embrittlement. The permeation tests were made in collaboration with IFIN Bucuresti inside of a special glove-box to avail their radioactive protection expertise. This investigation programme is ongoing. In this paper we describe the permeation stand facility and the preliminary tests carried out to date. (authors)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6353998','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6353998"><span id="translatedtitle">Lead <span class="hlt">isotopic</span> <span class="hlt">studies</span> of the Samail ophiolite, Oman</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen, J.H.; Pallister, J.S.</p> <p>1981-04-10</p> <p>The <span class="hlt">isotopic</span> composition of Pb and the concentrations of U, Th, and Pb have been determined for samples from various lithologic units and massive sulfides of the Samail ophiolite. The observed /sup 206/Pb//sup 204/Pb ratios range from 17.90 to 19.06, /sup 207/Pb//sup 204/Pb ratios from 15.43 to 15.63, and /sup 208/Pb//sup 204/Pb from 37.66 to 38.78. In Pb <span class="hlt">isotopic</span> evolution diagrams, the initial Pb <span class="hlt">isotopic</span> compositions of most of the samples from the Samail ophiolite plot within the field of oceanic basalt, clearly distinct from island arc data, and define some of the least radiogenic Pb observed from oceanic rocks. Lead data from the Samail are compatible with a model involving magma generation from an oceanic mantle source and formation of the ophiolite at an oceanic spreading center. U--Th--Pb <span class="hlt">isotopic</span> systematics demonstrate that vertical heterogeneity in the oceanic crust can be created through differential concentration of U, Th, and Pb during crystal fractionation and alteration at, or near, the spreading ridge. Calcite form amygdules in the ophiolite basalt has similar Pb <span class="hlt">isotopic</span> composition to the igneous rocks, suggesting precipitation of the calcite from seawater which contained Pb derived mostly from the oceanic crust. Lead <span class="hlt">isotopic</span> data on Fe--Cu sulfides are also similar to the results from the igneous suite suggesting that the source of the sulfides is predominently from the oceanic crust. Lead data from serpentinized peridotite and a galena sample from below the ophiolite suggest that part of the serpentinization process and the formation of galena could involve addition of radiogenic Pb from either a continental source or from oceanic sediments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19720039830&hterms=Precambrian&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DPrecambrian','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720039830&hterms=Precambrian&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DPrecambrian"><span id="translatedtitle">Carbon <span class="hlt">isotopic</span> <span class="hlt">studies</span> of organic matter in Precambrian rocks.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oehler, D. Z.; Schopf, J. W.; Kvenvolden, K. A.</p> <p>1972-01-01</p> <p>A survey has been undertaken of the carbon composition of the total organic fraction of a suite of Precambrian sediments to detect <span class="hlt">isotopic</span> trends possibly correlative with early evolutionary events. Early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa were examined for this purpose. Reduced carbon in these cherts was found to be <span class="hlt">isotopically</span> similar to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts was found to be anomalously heavy; it is suggested that this discontinuity may reflect a major event in biological evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvC..92b5806S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvC..92b5806S"><span id="translatedtitle">Systematic <span class="hlt">study</span> of (α ,γ ) reactions for stable nickel <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simon, A.; Beard, M.; Spyrou, A.; Quinn, S. J.; Bucher, B.; Couder, M.; DeYoung, P. A.; Dombos, A. C.; Görres, J.; Kontos, A.; Long, A.; Moran, M. T.; Paul, N.; Pereira, J.; Robertson, D.; Smith, K.; Stech, E.; Talwar, R.; Tan, W. P.; Wiescher, M.</p> <p>2015-08-01</p> <p>A systematic measurement of the (α ,γ ) reaction for all the stable nickel <span class="hlt">isotopes</span> has been performed using the γ -summing technique. For two of the <span class="hlt">isotopes</span>, 60Ni and 61Ni, the α -capture cross sections have been experimentally measured for the first time. For 58,62,64Ni, the current measurement is in excellent agreement with earlier results found in the literature, and additionally extends the energy range of the measured cross sections up to 8.7 MeV. The data provided a tool for testing the cross section predictions of Hauser-Feshbach calculations. The experimental results were compared to the cross sections calculated with the talys 1.6 code and commonly used databases non-smoker and bruslib. For each of the investigated <span class="hlt">isotopes</span> a combination of input parameter for talys was identified that best reproduces the experimental data, and recommended reaction rate has been calculated. Additionally, a set of inputs for Hauser-Feshbach calculations was given that, simultaneously for all the <span class="hlt">isotopes</span> under consideration, reproduces the experimental data within the experimental uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985PhDT.......167M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985PhDT.......167M"><span id="translatedtitle">Development of a Laser Probe for Argon <span class="hlt">Isotope</span> <span class="hlt">Studies</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McConville, Paul</p> <p></p> <p>Available from UMI in association with The British Library. The first objective of this <span class="hlt">study</span> was to develop a laser outgassing facility for argon <span class="hlt">isotope</span> <span class="hlt">studies</span>. Apart from the laser and construction of the laser sample port, existing vacuum and mass spectrometer systems were used. Laser performance and optimum operating conditions were investigated. The second objective was test and evaluate the laser extraction technique by <span class="hlt">studies</span> of simple geological samples. Previous laser ^{40} Ar-^{39}Ar dating <span class="hlt">studies</span> by other workers had not systematically established the basis or characteristics of the method. Results from laser and complementary stepped heating <span class="hlt">studies</span> of the ^{40}Ar-^ {39}Ar dating standard hornblende, hb3gr; a phlogopite sample from the Palabora (Phalaborwa) Complex; and biotites in a thin section of the Hamlet Bjerg granite from East Greenland, verified that: (1) Laser extraction reproduced within experimental error the stepped heating ^{40}Ar-^ {39}Ar and K-Ar ages of simple samples. (2) The precision of the technique i.e. the amount of sample required to give reliable ages, was limited in the present experiments largely by the level of the blanks and backgrounds to 10-100 ug samples. (3) Sample outgassing appeared to be limited to the order of 10 um outside the physical size of the laser pit, consistent with other estimates of the spatial definition in the literature. This could be understood by thermal diffusion and the length of the laser pulse. (4) The efficiency of the laser pulse in melting and outgassing mineral samples was shown to be dependent on silicate latent heats and mineral absorption at the laser wavelength. In addition, the ^{40} Ar-^{39}Ar age of the geologically significant Palabora Complex was determined as (2053 +/- 5) Ma. Excess argon led to a discrepancy between the laser and stepped heating ages of biotite and muscovite, (405 +/- 5) Ma, and laser ages of feldspars (510 +/- 20) Ma in the Hamlet Bjerg granite. This illustrated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeCoA..91...75S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeCoA..91...75S"><span id="translatedtitle">Mg <span class="hlt">isotope</span> fractionation during calcite precipitation: An experimental <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saulnier, Ségolène; Rollion-Bard, Claire; Vigier, Nathalie; Chaussidon, Marc</p> <p>2012-08-01</p> <p>Experimental precipitations of calcite and other carbonate minerals were performed under various conditions of pH, temperature and solution Mg/Ca to determine the Mg partition coefficient and Mg <span class="hlt">isotope</span> fractionation. Fifteen experiments were performed at pH ranging from 7.41 ± 0.07 to 8.51 ± 0.39, temperature ranging from 16.2 ± 0.7 to 26.5 ± 0.3 °C and Mg/Casolution ranging from 0.11 to 0.52 mol/mol. The apparent Mg partition coefficient between calcite and solution (DMg) spans a large range of values from 0.018 ± 0.014 to 0.15 ± 0.11 and carbonate Mg <span class="hlt">isotope</span> fractionation (Δ26Mg) ranges from -2.53 ± 0.25‰ to -1.33 ± 0.14‰ and does not correlate with either pH or temperature. The range in DMg and Δ26Mg suggests non-equilibrium partitioning controlled by the processes of calcite growth, i.e. mixing between calcite grown at equilibrium and fluid inclusions, and entrapment of a surface Mg-rich calcite layer in <span class="hlt">isotopic</span> equilibrium with the solution. The equilibrium Mg <span class="hlt">isotope</span> fractionation between inorganic calcite and solution is estimated to be -2.13 ± 0.24‰. Additional Mg elemental and <span class="hlt">isotopic</span> fractionations are observed to occur during biogenic formation of calcite due to variable removal of Mg by the organisms (high-Mg calcite corals, foraminifera) of seawater Mg from their calcification medium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V51A2627L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V51A2627L"><span id="translatedtitle">Calcium <span class="hlt">isotope</span> analytical technique for mafic rocks and its applications on constraining the source of Cenozoic ultra-potassic rocks in the Tibetan Plateau</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Y.; Zhang, Z.; Xu, J.</p> <p>2013-12-01</p> <p>Ca <span class="hlt">isotope</span> analytical technique for mafic rocks has been recently developed and set up at our lab. About mg level of a mafic rock sample was digested, and then a sub portion of the solution contains about 100ug Ca was spiked with a 42Ca-43Ca double spike and went through the column chemistry. Generally the Ca recovery is almost 100% and the procedure blank is about 50-150ng. Finally, about 5-10ug of the collected Ca cut was measured on our Triton TIMS. The precision of the data was around 0.1 per mil and the data we collected for standards are consistent with those reported by previous <span class="hlt">studies</span>. There are two groups of Cenozoic ultra-potassic rocks that are widespread in Tibetan Plateau: a northern group in Songpan-Ganzi and Qiangtang Terranes and a southern group in Lhasa Terrane. Previous petrology evidence, such as a relative enrichment in large ion lithophile element (LILE); negative Ta,Nb and Ti anomalies and high LREE/HREE ratio, support that those rocks are both derived from sub-continental lithospheric mantle (SCLM). However, differences between these two groups of rocks do exist: the southern group has higher K2O, Rb, Zr, Th, contents and a higher Rb/Ba, coupled with lower Al2O3, CaO, Na2O, Sr; the southern 87Sr/86Sr ratios are higher while the 143Nd/144Nd ratios are lower, etc. These suggest that the rocks could be derived from different mantle sources or produced by different geological processes. Ca <span class="hlt">isotope</span> is chosen in this <span class="hlt">study</span> to better understand the source of the ultra-potassic rocks because Ca <span class="hlt">isotope</span> has been a great tracer of different geological reservoirs and the <span class="hlt">isotopic</span> compositions of Ca may represent different genesic processes. We propose that the ultra-potassic rocks in the Tibet should have significant 40Ca enrichments due to the decay from 40K to 40Ca, therefore the variation of Ca <span class="hlt">isotopic</span> compositions among these ultra-potassic rocks could be obvious. We believe that based on our calcium data together with earlier <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25463204','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25463204"><span id="translatedtitle"><span class="hlt">Isotope</span> labeling pattern <span class="hlt">study</span> of central carbon metabolites using GC/MS.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jung, Joon-Young; Oh, Min-Kyu</p> <p>2015-01-01</p> <p>Determination of fluxes by (13)C tracer experiments depends on monitoring the (13)C labeling pattern of metabolites during <span class="hlt">isotope</span> experiments. In metabolome-based (13)C metabolic flux analysis, liquid chromatography combined with mass spectrometry or tandem mass spectrometry (LC/MS or LC/MS/MS, respectively) has been mainly used as an analytical platform for <span class="hlt">isotope</span> pattern <span class="hlt">studies</span> of central carbon metabolites. However, gas chromatography with mass spectrometry (GC/MS) has several advantages over LC/MS, such as high sensitivity, low cost, ease of operation, and availability of mass spectra databases for comparison. In this <span class="hlt">study</span>, analysis of <span class="hlt">isotope</span> pattern for central carbon metabolites using GC/MS was demonstrated. First, a proper set of mass ions for central carbon metabolites was selected based on carbon backbone information and structural isomers of mass fragment ions. A total of 34 mass fragment ions was selected and used for the quantification of 25 central carbon metabolites. Then, to quantify <span class="hlt">isotope</span> fractions, a natural mass isotopomer library for selected mass fragment ions was constructed and subtracted from isotopomer mass spectra data. The results revealed a surprisingly high abundance of partially labeled (13)C intermediates, such as 56.4% of fructose 6-phosphate and 47.6% of dihydroxyacetone phosphate at <span class="hlt">isotopic</span> steady state, which were generated in the pentose phosphate pathway. Finally, dynamic changes of <span class="hlt">isotope</span> fragments of central metabolites were monitored with a U-(13)C glucose stimulus response experiment in Kluyveromyces marxianus. With a comprehensive <span class="hlt">study</span> of <span class="hlt">isotope</span> patterns of central carbon metabolites using GC/MS, 25 central carbon metabolites and their <span class="hlt">isotopic</span> fractions were successfully quantified. Dynamic and precise acquisition of <span class="hlt">isotope</span> pattern can then be used in combination with proper kinetic models to calculate metabolic fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920004377','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920004377"><span id="translatedtitle"><span class="hlt">Isotopic</span> composition of Murchison organic compounds: Intramolecular carbon <span class="hlt">isotope</span> fractionation of acetic acid. Simulation <span class="hlt">studies</span> of cosmochemical organic syntheses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yuen, G. U.; Cronin, J. R.; Blair, N. E.; Desmarais, D. J.; Chang, S.</p> <p>1991-01-01</p> <p>Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon <span class="hlt">isotopic</span> composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being <span class="hlt">studied</span>, especially those processes capable of involving two or more starting carbon sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.V11B2268J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.V11B2268J"><span id="translatedtitle">Space-Time-<span class="hlt">Isotopic</span> Trends of Snake River Plain Basalts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jean, M. M.; Hanan, B. B.; Shervais, J. W.</p> <p>2010-12-01</p> <p>The Snake River Plain (SRP) volcanic province is an 800 km track of basalt extending from the Owyhee Plateau to its current terminus, the Yellowstone Plateau. It is one of several late-Tertiary magmatic terranes that also include the Cascades magmatic arc, the Columbia River basalts, and the Oregon Plateau basalts; all of which are adjacent to the Basin and Range Province extensional system (Hughes and McCurry, 2002). This province represents the track of the Yellowstone plume and consists of basalt that is compositionally similar to ocean-island basalt. This basalt overlies a series of rhyolitic eruptive centers (overlapping caldera complexes, ignimbrites, and caldera-filling eruptions) that signal the arrival of the plume head (Christiansen, 2001) and herald the onset of plume-related rhyolitic and basaltic volcanism (Pierce et al., 2002). Observed within the SRP are two basalt types: the dominant low-K olivine tholeiites and less common high-K alkaline basalts. We report new <span class="hlt">Sr</span>-, <span class="hlt">Nd</span>-, and Pb-<span class="hlt">isotopic</span> analyses of these two basalt types from all three SRP provinces: eastern, central, and western. Low-K tholeiites are enriched in 143Nd/144Nd and 86Sr/87Sr and forms a quasi-linear array in Pb-<span class="hlt">isotope</span> space, along with Craters of the Moon and eastern SRP basalts. High-K lavas are found largely in the western plain, and have a uniquely different <span class="hlt">isotopic</span> signature. They are depleted in 143Nd/144Nd and 86Sr/87Sr, relative to the low-K tholeiites, and plot closer to the BSE component of Zindler and Hart (1986). They also share the same Pb-<span class="hlt">isotopic</span> space with high-K basalts from Smith Prairie (Boise River Group 2 of Vetter and Shervais, 1992). One low-K tholeiite - Eureka North, plots with these high alkali basalts. Mass balance models have demonstrated an increasing plume component from the Yellowstone caldera in the east to the craton edge in the west. The lavas analyzed in this <span class="hlt">study</span> conform remarkably to this model. The mass fraction of plume component in western</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25532497','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25532497"><span id="translatedtitle">Copper <span class="hlt">isotope</span> effect in serum of cancer patients. A pilot <span class="hlt">study</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Télouk, Philippe; Puisieux, Alain; Fujii, Toshiyuki; Balter, Vincent; Bondanese, Victor P; Morel, Anne-Pierre; Clapisson, Gilles; Lamboux, Aline; Albarede, Francis</p> <p>2015-02-01</p> <p>The <span class="hlt">isotope</span> effect describes mass-dependent variations of natural <span class="hlt">isotope</span> abundances for a particular element. In this pilot <span class="hlt">study</span>, we measured the (65)Cu/(63)Cu ratios in the serums of 20 breast and 8 colorectal cancer patients, which correspond to, respectively, 90 and 49 samples taken at different times with molecular biomarker documentation. Copper <span class="hlt">isotope</span> compositions were determined by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). When compared with the literature data from a control group of 50 healthy blood donors, abundances of Cu <span class="hlt">isotopes</span> predict mortality in the colorectal cancer group with a probability p = 0.018. For the breast cancer patients and the group of control women the probability goes down to p = 0.0006 and the AUC under the ROC curve is 0.75. Most patients considered in this preliminary <span class="hlt">study</span> and with serum δ(65)Cu lower than the threshold value of -0.35‰ (per mil) did not survive. As a marker, a drop in δ(65)Cu precedes molecular biomarkers by several months. The observed decrease of δ(65)Cu in the serum of cancer patients is assigned to the extensive oxidative chelation of copper by cytosolic lactate. The potential of Cu <span class="hlt">isotope</span> variability as a new diagnostic tool for breast and colorectal cancer seems strong. Shifts in Cu <span class="hlt">isotope</span> compositions fingerprint cytosolic Cu chelation by lactate mono- and bidentates. This simple scheme provides a straightforward explanation for <span class="hlt">isotopically</span> light Cu in the serum and <span class="hlt">isotopically</span> heavy Cu in cancer cells: Cu(+) escaping chelation by lactate and excreted into the blood stream is <span class="hlt">isotopically</span> light. Low δ(65)Cu values in serum therefore reveal the strength of lactate production by the Warburg effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25532497','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25532497"><span id="translatedtitle">Copper <span class="hlt">isotope</span> effect in serum of cancer patients. A pilot <span class="hlt">study</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Télouk, Philippe; Puisieux, Alain; Fujii, Toshiyuki; Balter, Vincent; Bondanese, Victor P; Morel, Anne-Pierre; Clapisson, Gilles; Lamboux, Aline; Albarede, Francis</p> <p>2015-02-01</p> <p>The <span class="hlt">isotope</span> effect describes mass-dependent variations of natural <span class="hlt">isotope</span> abundances for a particular element. In this pilot <span class="hlt">study</span>, we measured the (65)Cu/(63)Cu ratios in the serums of 20 breast and 8 colorectal cancer patients, which correspond to, respectively, 90 and 49 samples taken at different times with molecular biomarker documentation. Copper <span class="hlt">isotope</span> compositions were determined by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). When compared with the literature data from a control group of 50 healthy blood donors, abundances of Cu <span class="hlt">isotopes</span> predict mortality in the colorectal cancer group with a probability p = 0.018. For the breast cancer patients and the group of control women the probability goes down to p = 0.0006 and the AUC under the ROC curve is 0.75. Most patients considered in this preliminary <span class="hlt">study</span> and with serum δ(65)Cu lower than the threshold value of -0.35‰ (per mil) did not survive. As a marker, a drop in δ(65)Cu precedes molecular biomarkers by several months. The observed decrease of δ(65)Cu in the serum of cancer patients is assigned to the extensive oxidative chelation of copper by cytosolic lactate. The potential of Cu <span class="hlt">isotope</span> variability as a new diagnostic tool for breast and colorectal cancer seems strong. Shifts in Cu <span class="hlt">isotope</span> compositions fingerprint cytosolic Cu chelation by lactate mono- and bidentates. This simple scheme provides a straightforward explanation for <span class="hlt">isotopically</span> light Cu in the serum and <span class="hlt">isotopically</span> heavy Cu in cancer cells: Cu(+) escaping chelation by lactate and excreted into the blood stream is <span class="hlt">isotopically</span> light. Low δ(65)Cu values in serum therefore reveal the strength of lactate production by the Warburg effect. PMID:25532497</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900015282','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900015282"><span id="translatedtitle">Rare-<span class="hlt">isotope</span> and kinetic <span class="hlt">studies</span> of Pt/SnO2 catalysts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Upchurch, Billy T.; Wood, George M.; Schryer, David R.; Hess, Robert V.; Miller, Irvin M.; Kielin, Erik J.</p> <p>1990-01-01</p> <p>Closed-cycle pulsed CO2 laser operation requires the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The catalyst must not only operate at low temperatures but also must operate efficiently for long periods. In the case of the Laser Atmospheric Wind Sounder (LAWS) laser, an operational lifetime of 3 years is required. Additionally, in order to minimize atmospheric absorption and enhance aerosol scatter of laser radiation, the LAWS system will operate at 9.1 micrometers with an oxygen-18 <span class="hlt">isotope</span> CO2 lasing medium. Consequently, the catalyst must not only operate at low temperatures but must also preserve the <span class="hlt">isotopic</span> integrity of the rare-<span class="hlt">isotope</span> composition in the recombination mode. Several years ago an investigation of commercially available and newly synthesized recombination catalysts for use in closed-cycle pulsed common and rare-<span class="hlt">isotope</span> CO2 lasers was implemented at the NASA Langley Research Center. Since that time, mechanistic efforts utilizing both common and rare oxygen <span class="hlt">isotopes</span> have been implemented and continue. Rare-<span class="hlt">isotope</span> <span class="hlt">studies</span> utilizing commercially available platinum-tin oxide catalyst have demonstrated that the catalyst contributes oxygen-16 to the product carbon dioxide thus rendering it unusable for rare-<span class="hlt">isotope</span> applications. A technique has been developed for modification of the surface of the common-<span class="hlt">isotope</span> catalyst to render it usable. Results of kinetic and <span class="hlt">isotope</span> label <span class="hlt">studies</span> using plug flow, recycle plug flow, and closed internal recycle plug flow reactor configuration modes are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EPJA...43...35A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EPJA...43...35A"><span id="translatedtitle"><span class="hlt">Studies</span> of neutron-deficient mendelevium <span class="hlt">isotopes</span> at SHIP</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Antalic, S.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Heinz, S.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Šáro, Š.</p> <p>2010-01-01</p> <p>The radioactive decay of the <span class="hlt">isotopes</span> 247Md , 246Md and their daughter products was investigated by means of α - α and α - γ coincidence spectroscopy. The <span class="hlt">isotopes</span> were produced using the fusion reaction 40Ar + 209Bi. Decay schemes are suggested for 247Md and 243Es . A new isomeric state in 246Md with a half-life of ( 4.4±0.8 s was observed. Previous data of electron-capture delayed fission of 246Md and 242Es were confirmed. The probability for this decay branch in 246Md was measured to be P ECDF > 0.10 . The probability for electron-capture delayed fission in the case of 242Es was determined to be P ECDF = 0.013+0.012 -0.007.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19810048177&hterms=isotope+ophiolite&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Disotope%2Bophiolite','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19810048177&hterms=isotope+ophiolite&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Disotope%2Bophiolite"><span id="translatedtitle">Lead <span class="hlt">isotopic</span> <span class="hlt">studies</span> of the Samail ophiolite, Oman</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, J. H.; Pallister, J. S.</p> <p>1981-01-01</p> <p>The <span class="hlt">isotopic</span> composition of Pb and the concentrations of U, Th, and Pb are determined for samples from massive sulfides and lithologic units of the Samail ophiolite. It is shown that the magma that formed the ophiolite was probably derived from a depleted mantle, similar in Pb <span class="hlt">isotopic</span> composition to the source area of mid-ocean ridge basalt. The gross geochemical characteristics of the mantle sources have remained almost unchanged for the last 100 million years. It is also shown that the U-Th-Pb systematics of the Samail formation indicate that local vertical heterogeneity in the oceanic crust can result from crystal fractionation and metasomatism at, and near, an oceanic spreading center.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17794201','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17794201"><span id="translatedtitle">Carbon <span class="hlt">isotopic</span> <span class="hlt">studies</span> of organic matter in precambrian rocks.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oehler, D Z; Schopf, J W; Kvenvolden, K A</p> <p>1972-03-17</p> <p>Reduced carbon in early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa is <span class="hlt">isotopically</span> similar (the average value of delta(13)C(PDB) is -28.7 per mil) to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts (Theespruit formation) is anomalously heavy (the average value of delta(13)C(PDB) is -16.5 per mil). This discontinuity may reflect a major event in biological evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012JPhCS.388o2009W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012JPhCS.388o2009W&link_type=ABSTRACT"><span id="translatedtitle">Theoretical <span class="hlt">study</span> of hyperfine structure constants of Ga <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Q. M.; Li, J. G.; Fritzsche, S.; Godefroid, M.; Chang, Z. W.; Dong, C. Z.</p> <p>2012-11-01</p> <p>The hyperfine structure constants for the ground 4s24p 2P°3/2 and lowest excited states 4s25s 2S1/2 of 71Ga are calculated using the GRASP2K package based on the multi-configuration Dirac-Hartree-Fock method. Furthermore, the magnetic dipole (μ) and the electric quadrupole (Q) moments of the Ga <span class="hlt">isotopes</span> from 67Ga to 81Ga are derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6014161','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6014161"><span id="translatedtitle">Oxygen <span class="hlt">isotope</span> fractionation between analcime and water: An experimental <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Karlsson, H.R.; Clayton, R.N. )</p> <p>1990-05-01</p> <p>The fractionation of oxygen <span class="hlt">isotopes</span> between natural analcime ({approximately}100 {mu}m) and water has been determined at 300, 350, and 400{degree}C at fluid pressures ranging from 1.5 to 5.0 kbar. <span class="hlt">Isotope</span> ratios were obtained for the analcime framework, the channel water, and bulk water. Analcimes from Surtsey (145{degree}C), DSDP Hole 417A (30 to 55{degree}C), and Guam (25{degree}C) were used to constrain the fractionation factors below 300{degree}C. Analcime channel water exchanged completely with external water in all runs. Although some retrograde exchange may have occurred during quenching, the results indicate that the channel water is depleted in {sup 18}O relative to bulk water by a constant value of {approximately}5{per thousand}, nearly independent of temperature. Analcime is the first hydrated mineral found to have water of hydration depleted in {sup 18}O. Analcime framework oxygen exchanged 80, 90, and 96% at 300{degree}C for 412 h, 350{degree}C for 178 h, and 400{degree}C for 120 h, respectively. Equilibrium {Delta}{sup 18}O ({per thousand}) are as follows: 2.9 (400{degree}C), 4.5 (350{degree}C), and 5.8 (300{degree}C) for the experimental runs and 12.2 (145{degree}C) and 24.2 to 28.2 (30-55{degree}C) for the empirical data. The analcime-water fractionation curve is within experimental error of that of calcite-water. The exchange had little effect on grain morphology and does not involve recrystallization. This is the fastest exchange observed for a silicate. The rapid exchange rates indicate that zeolites in active high-temperature geothermal areas are in oxygen <span class="hlt">isotopic</span> equilibrium with ambient fluids. Once calibrated, zeolites may be among the best low-temperature oxygen <span class="hlt">isotope</span> geothermometers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988GeCoA..52..593Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988GeCoA..52..593Y"><span id="translatedtitle">Stable <span class="hlt">isotope</span> <span class="hlt">studies</span> of nephrite deposits from Fengtien, Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yui, Tzen-Fu; Yeh, Hsueh-Wen; Lee, Chihming Wang</p> <p>1988-03-01</p> <p>Metasomatic nephrite deposits ( i.e., rodingites) occur between serpentinites and muscovite-quartz schist in the Fengtien area, eastern Taiwan. The δ 18O values of nephrite range from +4.5 to +5.3%. and the δD values, from -33 to -68%. The narrow range in the δ 18O values and wide variation in the δD values indicate low water/rock ratios and multiple origins of the ambient H 2O during nephrite formation. The ultimate sources of the ambient H 2O are largely sea water for the early nephrite and meteoric water for the late nephrite. The temperature of nephrite formation is 320-420°C: the estimated O-<span class="hlt">isotopic</span> fractionation between nephrite (tremolite) and serpentine (antigorite) is 1.0 ± 0.2%. in this temperature range. Diopsidefels and epidotite are two other kinds of rodingite in the deposits. The δ 18O values of diopside from diopsidefels range from +3.7 to +4.5%., theδD values of clinozoisite from epidotite range from -31 to -34%. and the δ 18O value of one clinozoisite analyzed is +3.9%. These data suggest that most diopsidefels formed in <span class="hlt">isotopic</span> equilibrium with nephrite and that clinozoisite was not in <span class="hlt">isotopic</span> equilibrium with either nephrite or diopsidefels. O-<span class="hlt">isotope</span> compositions of both nephrite and diopsidefels cannot give conclusive evidence of their parental rocks. Circumstantial evidence, however, implies that the nephrite is derived from serpentinite whereas diopsidefels formed from unaltered ultramafic rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NucFu..56e6012L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NucFu..56e6012L"><span id="translatedtitle">Multi-scale <span class="hlt">study</span> of the <span class="hlt">isotope</span> effect in ISTTOK</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, B.; Silva, C.; Figueiredo, H.; Pedrosa, M. A.; van Milligen, B. Ph.; Pereira, T.; Losada, U.; Hidalgo, C.</p> <p>2016-05-01</p> <p>The <span class="hlt">isotope</span> effect, namely the <span class="hlt">isotope</span> dependence of plasma confinement, is still one of the principal scientific conundrums facing the magnetic fusion community. We have investigated the impact of <span class="hlt">isotope</span> mass on multi-scale mechanisms, including the characterization of radial correlation lengths (\\boldsymbol{L}{r} ) and long-range correlations (LRC) of plasma fluctuations using multi-array Langmuir probe system, in hydrogen (H) and deuterium (D) plasmas in the ISTTOK tokamak. We found that when changing plasma composition from the H dominated to D dominated, the LRC amplitude increased markedly (10-30%) and the \\boldsymbol{L}{r} increased slightly (~10%). The particle confinement also improved by about 50%. The changes of LRC and \\boldsymbol{L}{r} are congruent with previous findings in the TEXTOR tokamak (Xu et al 2013 Phys. Rev. Lett. 110 265005). In addition, using biorthogonal decomposition, both geodesic acoustic modes and very low frequency (<5 kHz) coherent modes were found to be contributing to LRC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110004947','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110004947"><span id="translatedtitle">Sm-Nd <span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of Ureilite Novo Urei</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shih, C.-Y.; Nyquist, L. E.; Reese, Y.; Goodrich, C. A.</p> <p>2011-01-01</p> <p>Ureilites are ultramafic (harzburgitic) achondrites composed predominantly of olivine and pyroxenes, abundant carbon (graphites and shock-produced diamonds), some metal and sulfides. These rocks probably represent ultramafic mantles of differentiated parent asteroidal bodies. Age determinations of these rocks by Rb-Sr and Sm-Nd methods have been difficult because of their extremely low abundances of these parent-daughter elements. Nevertheless, Sm-Nd isochron ages were reported for Kenna, Goalpara, MET 78008 and PCA 82506 yielding ages of 3.74+/-0.02 Ga, approx.3.7 Ga, 4.09+/-0.08 Ga, 4.23+/-0.06 Ga, respectively [1-4]. These "young" Sm-Nd ages may represent secondary metasomatism events [1] related to impacts [5], as indicated by the similarly young Ar-39-Ar-40 degassing ages of 3.3-4.1 Ga for ureilites Kenna, Novo Urei and Havero [6]. Alternatively, it has been suggested that these rocks may have been contaminated with terrestrial crustal materials and the isochrons do not have any age significance [2,7]. Indications of old approx.4.56 Ga ages for ureilites were reported from the U-Pb and Sm-Nd model ages for MET 78008 [8]. More reliable evidences for old formation ages of ureilites were reported recently using the short-lived chronometers Hf-182-W-182, Al-26-Mg-26 and Mn-53-Cr-53. The deficits of 182W in ureilites suggest the metal-silicate segregation occurred very early, approx.1-2 Ma after CAI [9]. The Al-26-Mg-26 and Mn-53-Cr-53 <span class="hlt">studies</span> for a feldspathic lithology [10] and the Mn-53-Cr-53 for olivine- and pyroxene-dominant lithologies [11] in ureilites revealed that they crystallized approx.5.4 Ma after CAI, i.e., at 4563.8+/-0.5 Ma relative to D.Orbigny. In this report, we present Sm-Nd <span class="hlt">isotopic</span> data for a relatively fresh ureilite, Novo Urei, a rare ureilite fall (1886). We compare these data to Sm-Nd data for other ureilites, and discuss Novo Urei's petrogenesis</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5462682','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5462682"><span id="translatedtitle">Use of stable <span class="hlt">isotopes</span> of selenium in human metabolic <span class="hlt">studies</span>: development of analytical methodology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Janghorbani, M.; Ting, B.T.; Young, V.R.</p> <p>1981-12-01</p> <p>Use of stable <span class="hlt">isotopes</span> of selenium in relation to enrichment of diets for <span class="hlt">studies</span> of selenium absorption and metabolism in human subjects is discussed. A method based on radiochemical neutron activation analysis is described which allows accurate measurement of stable <span class="hlt">isotopes</span> 74Se, 76Se, and 80Se in matrices (feces, plasma, red blood cells, and urine) of interest in metabolic <span class="hlt">studies</span>. We show that these <span class="hlt">isotopes</span> can routinely be measured with analytical precision and accuracy of 10% in samples of available size. This precision and accuracy is satisfactory for conduct of many nutritional experiments concerned with gastrointestinal absorption, plasma and red cell selenium turnover, and urinary excretion of the element, using an oral dose of 74Se. Original, experimental data are presented to illustrate the degree of enrichment of 74Se in feces, plasma, and urine after a single oral ingestion of 50 micrograms of the <span class="hlt">isotope</span> with a breakfast meal in healthy young men.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeCoA.113...38R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeCoA.113...38R"><span id="translatedtitle">From evaporated seawater to uranium-mineralizing brines: <span class="hlt">Isotopic</span> and trace element <span class="hlt">study</span> of quartz-dolomite veins in the Athabasca system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richard, Antonin; Boulvais, Philippe; Mercadier, Julien; Boiron, Marie-Christine; Cathelineau, Michel; Cuney, Michel; France-Lanord, Christian</p> <p>2013-07-01</p> <p>Stable <span class="hlt">isotope</span> (O, H, C), radiogenic <span class="hlt">isotope</span> (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>) and trace element analyses have been applied to quartz-dolomite veins and their uranium(U)-bearing fluid inclusions associated with Proterozoic unconformity-related UO2 (uraninite) ores in the Athabasca Basin (Canada) in order to trace the evolution of pristine evaporated seawater towards U-mineralizing brines during their migration through sediments and basement rocks. Fluid inclusion data show that quartz and dolomite have precipitated from brines of comparable chemistry (excepted for relatively small amounts of CO2 found in dolomite-hosted fluid inclusions). However, δ18O values of quartz veins (δ18O = 11‰ to 18‰) and dolomite veins (δ18O = 13‰ to 24‰) clearly indicate <span class="hlt">isotopic</span> disequilibrium between quartz and dolomite. Hence, it is inferred that this <span class="hlt">isotopic</span> disequilibrium primarily reflects a decrease in temperature between the quartz stage (˜180 °C) and the dolomite stage (˜120 °C). The δ13C values of CO2 dissolved in dolomite-hosted fluid inclusions (δ13C = -30‰ to -4‰) and the δ13C values of dolomite (δ13C = -23.5‰ to -3.5‰) indicate that the CO2 dissolved in the mineralizing brines originated from brine-graphite interactions in the basement. The resulting slight increase in the fluid partial pressure of CO2 (pCO2) may have triggered dolomite precipitation instead of quartz. δ18O values of quartz veins and previously published δ18O values of the main alteration minerals around the U-ores (illite, chlorite and tourmaline) show that quartz and alteration minerals were <span class="hlt">isotopically</span> equilibrated with the same fluid at ˜180 °C. The REE concentrations in dolomite produce PAAS-normalized patterns that show some similarities with that of UO2 and are clearly distinct from that of the other main REE-bearing minerals in these environments (monazite, zircon and aluminum phosphate-sulfate (APS) minerals). The radiogenic <span class="hlt">isotope</span> compositions of dolomite (87Sr/86Sri = 0.7053 to 0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017556','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017556"><span id="translatedtitle">Multiple <span class="hlt">isotopic</span> components in Quaternary volcanic rocks of the Cascade Arc near Crater lake, Oregon</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bacon, C.R.; Gunn, S.H.; Lanphere, M.A.; Wooden, J.L.</p> <p>1994-01-01</p> <p>Quaternary lavas and pyroclastic rocks of Mount Mazama, Crater lake caldera, and the surrounding area have variable <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotopic</span> compositions. High-alumina olivine tholeiites have 87Ar/86Ar ratios of 0.70346-0.70364; basaltic andesite, 0.70349-0.70372; shoshonitic basaltic andesite, 0.70374-0.70388; and andesite, 0.70324-0.70383. Dacites of Mount Mazama have 87Sr/ 86Sr ratios of 0.70348-0.70373. Most rhyodacites converge on 0.7037. Andesitic to mafic-cumulate scoriae of the climatic eruption, and enclaves in pre-climactic rhyodacites, cluster in two groups but show nearly the entire 87Sr/86Sr range of the data set, confirming previously suggested introduction of diverse parental magmas into the growing climactic chamber. Magma evolution is described. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991IJMSI.111..355F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991IJMSI.111..355F"><span id="translatedtitle">The <span class="hlt">study</span> of trace metal absoption using stable <span class="hlt">isotopes</span> and mass spectrometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fennessey, P. V.; Lloyd-Kindstrand, L.; Hambidge, K. M.</p> <p>1991-12-01</p> <p>The absorption and excretion of zinc stable <span class="hlt">isotopes</span> have been followed in more than 120 human subjects. The <span class="hlt">isotope</span> enrichment determinations were made using a standard VG 7070E HF mass spectrometer. A fast atom gun (FAB) was used to form the ions from a dry residue on a pure silver probe tip. <span class="hlt">Isotope</span> ratio measurements were found to have a precision of better than 2% (relative standard deviation) and required a sample size of 1-5 [mu]g. The average true absorption of zinc was found to be 73 ± 12% (2[sigma]) when the metal was taken in a fasting state. This absorption figure was corrected for tracer that had been absorbed and secreted into the gastrointestinal (GI) tract over the time course of the <span class="hlt">study</span>. The average time for a majority of the stable <span class="hlt">isotope</span> tracer to pass through the GI tract was 4.7 ± 1.9 (2[sigma]) days.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25647577','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25647577"><span id="translatedtitle"><span class="hlt">Isotope</span> effects on chemical shifts in the <span class="hlt">study</span> of intramolecular hydrogen bonds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hansen, Poul Erik</p> <p>2015-01-30</p> <p>The paper deals with the use of <span class="hlt">isotope</span> effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between "static" and tautomeric systems. <span class="hlt">Isotope</span> effects on chemical shifts are particularly useful in such <span class="hlt">studies</span>. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N-. The paper will be deal with both secondary and primary <span class="hlt">isotope</span> effects on chemical shifts. These two types of <span class="hlt">isotope</span> effects monitor the same hydrogen bond, but from different angles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12..675B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12..675B"><span id="translatedtitle">Osmium <span class="hlt">isotopes</span> suggest fast and efficient mixing in the oceanic upper mantle.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bizimis, Michael; Salters, Vincent</p> <p>2010-05-01</p> <p> samples with TRD older than 2Ga have been reported. The TRD age peaks overlap with two major crustal building events recorded in the U/Pb crustal zircon ages. Therefore, peridotites from the convecting upper mantle can retain some memory of ancient depletion events, and these depletions are perhaps linked to major crustal building or large-scale mantle melting events. In the case of the Hawaiian peridotites, an ancient depletion event is further supported by some extremely radiogenic Hf <span class="hlt">isotope</span> compositions. However, the vast majority of oceanic mantle samples show a narrow rage of Os <span class="hlt">isotope</span> compositions (187Os/188Os = 0.123-0.126) with TRDs at 300-600 Ma. If the upper mantle has been produced continuously (or episodically) since at least the early Archean, it is then surprising that almost all oceanic mantle samples record such young depletion ages. We suggest that convective mixing in the mantle is rigorous enough that effectively re-homogenizes and resets the Os <span class="hlt">isotope</span> composition of previously depleted peridotites within short time scales (<500Ma). Similarly recent ages have been derived from modeling the <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Hf, Pb <span class="hlt">isotopic</span> composition of MORBs. This resetting and homogenization can be due to re-equilibration of depleted mantle with enriched components, e.g. recycled basaltic crust or more fertile mantle. Ancient depletion events are only effectively preserved in the sublithospheric mantle samples (e.g. Kaapval, Slave, Wyoming cratons) because they remain isolated from the convective mantle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4101500','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4101500"><span id="translatedtitle">Application of Stable <span class="hlt">Isotope</span>-Assisted Metabolomics for Cell Metabolism <span class="hlt">Studies</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>You, Le; Zhang, Baichen; Tang, Yinjie J.</p> <p>2014-01-01</p> <p>The applications of stable <span class="hlt">isotopes</span> in metabolomics have facilitated the <span class="hlt">study</span> of cell metabolisms. Stable <span class="hlt">isotope</span>-assisted metabolomics requires: (1) properly designed tracer experiments; (2) stringent sampling and quenching protocols to minimize <span class="hlt">isotopic</span> alternations; (3) efficient metabolite separations; (4) high resolution mass spectrometry to resolve overlapping peaks and background noises; and (5) data analysis methods and databases to decipher <span class="hlt">isotopic</span> clusters over a broad m/z range (mass-to-charge ratio). This paper overviews mass spectrometry based techniques for precise determination of metabolites and their isotopologues. It also discusses applications of <span class="hlt">isotopic</span> approaches to track substrate utilization, identify unknown metabolites and their chemical formulas, measure metabolite concentrations, determine putative metabolic pathways, and investigate microbial community populations and their carbon assimilation patterns. In addition, 13C-metabolite fingerprinting and metabolic models can be integrated to quantify carbon fluxes (enzyme reaction rates). The fluxome, in combination with other “omics” analyses, may give systems-level insights into regulatory mechanisms underlying gene functions. More importantly, 13C-tracer experiments significantly improve the potential of low-resolution gas chromatography-mass spectrometry (GC-MS) for broad-scope metabolism <span class="hlt">studies</span>. We foresee the <span class="hlt">isotope</span>-assisted metabolomics to be an indispensable tool in industrial biotechnology, environmental microbiology, and medical research. PMID:24957020</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25448013','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25448013"><span id="translatedtitle">Combining solvent <span class="hlt">isotope</span> effects with substrate <span class="hlt">isotope</span> effects in mechanistic <span class="hlt">studies</span> of alcohol and amine oxidation by enzymes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fitzpatrick, Paul F</p> <p>2015-11-01</p> <p>Oxidation of alcohols and amines is catalyzed by multiple families of flavin- and pyridine nucleotide-dependent enzymes. Measurement of solvent <span class="hlt">isotope</span> effects provides a unique mechanistic probe of the timing of the cleavage of the OH and NH bonds, necessary information for a complete description of the catalytic mechanism. The inherent ambiguities in interpretation of solvent <span class="hlt">isotope</span> effects can be significantly decreased if <span class="hlt">isotope</span> effects arising from <span class="hlt">isotopically</span> labeled substrates are measured in combination with solvent <span class="hlt">isotope</span> effects. The application of combined solvent and substrate (mainly deuterium) <span class="hlt">isotope</span> effects to multiple enzymes is described here to illustrate the range of mechanistic insights that such an approach can provide. This article is part of a Special Issue entitled: Enzyme Transition States from Theory and Experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5319882','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5319882"><span id="translatedtitle">Trace element and <span class="hlt">isotopic</span> constraints on magmatic evolution at Lassen volcanic center</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bullen, T.D.; Clynne, M.A. )</p> <p>1990-11-10</p> <p>Magmatic evolution at the Lassen volcanic center (LVC) is characterized by a transition from predominantly andesitic to predominantly silicic volcanism with time. Magmas of the adesitic, or Brokeoff phase of volcanism range in composition from basaltic andesite to dacite, whereas those of silicic, or Lassen phase range in composition from basaltic andesite to rhyolite. The distinctive mixing-dominated arrays for each volcanic phase manifest the generation and evolution of two physically distinct, but genetically related magma systems. The LVC magmas have <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotope</span> characteristics that approximate two-component mixing arrays. One <span class="hlt">isotopic</span> component is similar in composition to that of NE Pacific Ocean ridge and seamount basalts (MORB component), the other to mafic Mesozoic granitoids sampled from the neighboring Klamath and Sierra Nevada provinces (KSN component). The lack of a correlation between the major element and <span class="hlt">isotopic</span> compositions of LVC magmas seriously limits any model for magmatic evolution that relies on assimilation of old middle to upper crust by <span class="hlt">isotopically</span> homogeneous mafic magmas during their ascent through the crust. Alternatively, the <span class="hlt">isotopic</span> and geochemical uniformity of the most silicic magmas of the Brokeoff and Lassen phases suggests that they are well-homogenized partial melts. The likely source region for these silicic melts is the lower crust, which the authors envision to consist primarily of mafic igneous rocks that are similar in geochemical and <span class="hlt">isotopic</span> diversity to the regional mafic lavas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18702535','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18702535"><span id="translatedtitle">Application of stable <span class="hlt">isotope</span>-labeled compounds in metabolism and in metabolism-mediated toxicity <span class="hlt">studies</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mutlib, Abdul E</p> <p>2008-09-01</p> <p>Stable <span class="hlt">isotope</span>-labeled compounds have been synthesized and utilized by scientists from various areas of biomedical research during the last several decades. Compounds labeled with stable <span class="hlt">isotopes</span>, such as deuterium and carbon-13, have been used effectively by drug metabolism scientists and toxicologists to gain better understanding of drugs' disposition and their potential role in target organ toxicities. The combination of stable <span class="hlt">isotope</span>-labeling techniques with mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, which allows rapid acquisition and interpretation of data, has promoted greater use of these stable <span class="hlt">isotope</span>-labeled compounds in absorption, distribution, metabolism, and excretion (ADME) <span class="hlt">studies</span>. Examples of the use of stable <span class="hlt">isotope</span>-labeled compounds in elucidating structures of metabolites and delineating complex metabolic pathways are presented in this review. The application of labeled compounds in mechanistic toxicity <span class="hlt">studies</span> will be discussed by providing an example of how strategic placement of a deuterium atom in a drug molecule mitigated specific-specific renal toxicity. Other examples from the literature demonstrating the application of stable <span class="hlt">isotope</span>-labeled compounds in understanding metabolism-mediated toxicities are presented. Furthermore, an example of how a stable <span class="hlt">isotope</span>-labeled compound was utilized to better understand some of the gene changes in toxicogenomic <span class="hlt">studies</span> is discussed. The interpretation of large sets of data produced from toxicogenomics <span class="hlt">studies</span> can be a challenge. One approach that could be used to simplify interpretation of the data, especially from <span class="hlt">studies</span> designed to link gene changes with the formation of reactive metabolites thought to be responsible for toxicities, is through the use of stable <span class="hlt">isotope</span>-labeled compounds. This is a relatively unexplored territory and needs to be further investigated. The employment of analytical techniques, especially mass spectrometry and NMR, used in conjunction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4859758','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4859758"><span id="translatedtitle">Stable <span class="hlt">Isotope</span> Resolved Metabolomics <span class="hlt">Studies</span> in Ex Vivo TIssue Slices</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fan, Teresa W-M.; Lane, Andrew N.; Higashi, Richard M.</p> <p>2016-01-01</p> <p>An important component of this methodology is to assess the role of the tumor microenvironment on tumor growth and survival. To tackle this problem, we have adapted the original approach of Warburg 1, by combining thin tissue slices with Stable <span class="hlt">Isotope</span> Resolved Metabolomics (SIRM) to determine detailed metabolic activity of human tissues. SIRM enables the tracing of metabolic transformations of source molecules such as glucose or glutamine over defined time periods, and is a requirement for detailed pathway tracing and flux analysis. In our approach, we maintain freshly resected tissue slices (both cancerous and non- cancerous from the same organ of the same subject) in cell culture media, and treat with appropriate stable <span class="hlt">isotope</span>-enriched nutrients, e.g. 13C6-glucose or 13C5, 15N2 -glutamine. These slices are viable for at least 24 h, and make it possible to eliminate systemic influence on the target tissue metabolism while maintaining the original 3D cellular architecture. It is therefore an excellent pre-clinical platform for assessing the effect of therapeutic agents on target tissue metabolism and their therapeutic efficacy on individual patients 2,3. PMID:27158639</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5347674','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5347674"><span id="translatedtitle">Positional <span class="hlt">isotope</span> exchange <span class="hlt">studies</span> on enzyme using NMR spectroscopy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Matsunaga, T.O.</p> <p>1987-01-01</p> <p>The <span class="hlt">isotopically</span> enriched compounds, /sup 18/O-..beta..,..gamma..-ATP and /sup 18/O bridge-labeled pyrophosphate, synthesized previously in this laboratory, were used to investigate and measure the exchange vs. turnover of substrates and products from their central complexes in four selected enzyme systems. Using hi-field /sup 31/P NMR, we were able to differentiate between /sup 18/O labeled in the bridge vs. the non-bridge positions by virtue of the <span class="hlt">isotope</span> shift upon the phosphorus nuclei. The bridge to non-bridge scrambling of the label was quantitated and the exchange vs. turnover ratios under a variety of conditions was determined. Using the substrate inhibitor carboxycreatinine, PIX experiments with /sup 18/O-..beta..,..gamma..-ATP and creatine kinase were conducted. It was shown that carboxycreatinine and creatine kinase promoted exchange of the /sup 18/O label as determined by NMR. We have concluded that carboxycreatinine is either a substrate that catalyzes very slow turnover or it catalyzes exchange by a dissociative (SN/sub 1//sub P/) type of mechanism</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6909680','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6909680"><span id="translatedtitle">The hydrothermal stability of zircon: Preliminary experimental and <span class="hlt">isotopic</span> <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sinha, A.K.; Wayne, D.M.; Hewitt, D.A. )</p> <p>1992-09-01</p> <p>Experimental investigations of the stability of the U-Pb <span class="hlt">isotopic</span> system in nonmetamict zircons show that appreciable losses of Pb and U can be induced at amphibolite-grade conditions (400 C to 600 C, 4 to 6 kb) in 2 M NaCl and 2% HNO[sub 3] solutions. The severity of U loss and, to a lesser extent Pb loss, varies with solution composition: in this case the 2 M NaCl solution induced more Pb and U loss than the 2% HNO[sub 3] solution at the same P-T conditions. Scanning electron microscopy of the run products also revealed a range of corrosion-related surface features, which suggests that some of the observed trends in Pb and U loss must be attributed to zircon dissolution. Backscattered electron (BSE) imaging of the run products further suggests that partial homogenization of chemical zoning patterns occurred during the experiments. Microprobe analyses of treated and untreated grain show that both populations have a similar range of Hf contents. Thus, the apparent loss of sharp, well-defined zoning features is most likely due to small-scale 'smearing out' of formerly sharp chemical gradients and is perhaps related to the annealing of lattice defects caused by alpha-recoil damage. Thus, experimentally induced U-Pb <span class="hlt">isotopic</span> discordance in zircon is a complex function of zircon stability and annealing effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5274846','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5274846"><span id="translatedtitle">Experimental and computer modeling <span class="hlt">studies</span> of <span class="hlt">isotopically</span> selective two-step laser photodissociation of small molecules</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zittel, P.F.</p> <p>1992-03-25</p> <p>The approach to laser <span class="hlt">isotope</span> separation taken in this <span class="hlt">study</span> is based on <span class="hlt">isotopically</span> selective, two-step, laser photodissociation of small molecules. A primary goal of this <span class="hlt">study</span> is the measurement of fundamental molecular processes which control the two-step, photodissociative <span class="hlt">isotope</span> enrichment process. This objective has led to experimental measurements of uv photodissociation cross sections for vibrationally excited states of several small molecules, including the first cross section reported for any neutral molecule in a specific, excited vibrational state. A second goal of this <span class="hlt">study</span> has been the laboratory demonstration of <span class="hlt">isotope</span> enrichment for <span class="hlt">isotopes</span> of practical interest and for processes with a potential for larger scale production. Where possible, efforts have focussed on the separation of middle <span class="hlt">isotopes</span>, such as {sup 17}O and {sup 33}S, which are expensive and difficult to separate using other techniques. Considerable success has been achieved in demonstrating the enrichment of <span class="hlt">isotopes</span> of bromine, carbon, oxygen and a third goal of this <span class="hlt">study</span> has been the application of computer modeling to the two-step enrichment process. Experimental measurements define as many as possible of the critical photophysical and chemical parameters required by an ab initio computer model of the enrichment process. Progress toward these goals has been documented in detail in a variety of journal articles and technical reports. It is not the objective of this final report to discuss each aspect of the work done under this contract/grant in detail. A general overview of the program, touches briefly on each of the problems addressed by the <span class="hlt">study</span> and provides references to more detailed discussions. 19 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21289628','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21289628"><span id="translatedtitle"><span class="hlt">Study</span> of the Photon Strength Functions for Gadolinium <span class="hlt">Isotopes</span> with the DANCE Array</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dashdorj, D.; Mitchell, G. E.; Baramsai, B.; Chankova, R.; Chyzh, A.; Walker, C.; Agvaanluvsan, U.; Becker, J. A.; Parker, W.; Sleaford, B.; Wu, C. Y.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Krticka, M.</p> <p>2009-03-10</p> <p>The gadolinium <span class="hlt">isotopes</span> are interesting for reactor applications as well as for medicine and astrophysics. The gadolinium <span class="hlt">isotopes</span> have some of the largest neutron capture cross sections. As a consequence they are used in the control rod in reactor fuel assembly. From the basic science point of view, there are seven stable <span class="hlt">isotopes</span> of gadolinium with varying degrees of deformation. Therefore they provide a good testing ground for the <span class="hlt">study</span> of deformation dependent structure such as the scissors mode. Decay gamma rays following neutron capture on Gd <span class="hlt">isotopes</span> are detected by the DANCE array, which is located at flight path 14 at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. The high segmentation and close packing of the detector array enable gamma-ray multiplicity measurements. The calorimetric properties of the DANCE array coupled with the neutron time-of-flight technique enables one to gate on a specific resonance of a specific <span class="hlt">isotope</span> in the time-of-flight spectrum and obtain the summed energy spectrum for that <span class="hlt">isotope</span>. The singles gamma-ray spectrum for each multiplicity can be separated by their DANCE cluster multiplicity. Various photon strength function models are used for comparison with experimentally measured DANCE data and provide insight for understanding the statistical decay properties of deformed nuclei.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8523488','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8523488"><span id="translatedtitle">Stable <span class="hlt">isotope</span> identification of lead sources in preschool children--the Omaha <span class="hlt">Study</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Angle, C R; Manton, W I; Stanek, K L</p> <p>1995-01-01</p> <p>The objective was to determine, from analysis of the naturally occurring stable <span class="hlt">isotopes</span> of lead, the relative contribution of food, handdust, housedust, soil and air lead to the absorbed (urinary) lead and the blood lead of children living in a former smelter city. A longitudinal 12 month <span class="hlt">study</span> was conducted of 21 children, 2 - 3 years of age, living in central Omaha, balanced for race, gender and socioeconomic status. Field clean samples were collected monthly of 24 hour duplicate diet, handwipe and urine, with quarterly blood lead, annual environmental lead, weekly air for total lead and 206Pb, 207Pb and 208Pb by thermal ionization/mass spectrometry with a 205Pb spike in a Class II laboratory. Despite residence in a smelter city each child had a unique <span class="hlt">isotopic</span> ratio of handwipe, blood and urine lead, the latter being identical. There was no correlation of handwipe <span class="hlt">isotopic</span> ratio with proximity to a lead emission source or to the decade of the housing stock. The <span class="hlt">isotopic</span> ratio of the annual mean handwipe lead predicted 43% of the variance of the annual mean blood and urine lead ratio (r2 = .43; p = .001). Handwipe lead ratios correlated (p < or = .05) with those of the windowsills and air ducts. The mean <span class="hlt">isotopic</span> ratios of blood and urine lead were lower than those of handwipe and food, consistent with a contribution by endogenous bone lead. Clean catch urine provides a noninvasive index of blood lead <span class="hlt">isotopic</span> ratio in children, as in adults.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23495640','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23495640"><span id="translatedtitle">Hydrogen <span class="hlt">isotope</span> variability in prairie wetland systems: implications for <span class="hlt">studies</span> of migratory connectivity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bortolotti, Lauren E; Clark, Robert G; Wassenaar, Leonard I</p> <p>2013-01-01</p> <p>Hydrogen <span class="hlt">isotopes</span> (delta2H) are often used to infer the origins of migratory animals based on the strong correlation between deuterium content of tissues and long-term patterns of precipitation. However, the extreme flood and drought dynamics of surface waters in prairie wetland systems could mask these expected correlations. We investigated H <span class="hlt">isotopic</span> variability in an aquatic food web associated with Tree Swallows (Tachycineta bicolor) that rely heavily on wetland-derived aerial insects for food. We evaluated <span class="hlt">isotopic</span> turnover and incorporation of environmental water into tissue, processes that could affect H <span class="hlt">isotopic</span> composition. Wetland water and aquatic invertebrates showed intra- and interannual H <span class="hlt">isotopic</span> variation mainly related to evaporation and the amount and timing of precipitation. Snails showed rapid turnover of tissue deuterium and a large contribution of environmental water to their tissues. Swallow feather deuterium (delta2Hf) was variable but did not clearly follow changes in any of the food web compartments measured. Instead, <span class="hlt">isotopic</span> variability may have been driven by shifts in the type or relative amounts of grey consumed and types of wetlands used. Nevertheless, despite relatively high variance in delta2Hf, the majority of birds fell within the predicted range of delta2Hf for the <span class="hlt">study</span> area, revealing that significant trophic averaging occurred. However, both (presumed) diet shifts and variable hydrological conditions have the potential to greatly increase variance that must be considered when assigning origins of migratory animals based on delta2H.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V54A..02H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V54A..02H"><span id="translatedtitle">Deciphering The Sources Of Cenozoic Volcanism In Central Mongolia Using Trace Element And <span class="hlt">Isotope</span> Geochemistry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hunt, A. C.; Parkinson, I. J.; Harris, N.; Rogers, N. W.; Barry, T.; Yondon, M.</p> <p>2009-12-01</p> <p>One of the largest regions of Cenozoic intra-plate volcanism stretches across central Asia from the Baikal Rift in Siberia, through central Mongolia to China. In Mongolia this is expressed as numerous small-volume alkali-basaltic cones and lavas, erupted since ca. 30 Ma. Currently, accepted models of melt generation for intraplate magmatism, such as mantle plumes, lithospheric extension and convective removal of the lithosphere, are difficult to reconcile with some aspects of volcanism and tectonics in this region. A suite of basalts erupted across an area of Cenozoic uplift in central Mongolia, known as the Hangai Dome, has been analysed for trace elements and <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopes</span>. New Pb <span class="hlt">isotope</span> data were collected by double spike MC-ICP-MS at the Open University and have a long-term 2σ reproducibility better than 175 ppm for NBS 981. These data suggest progressive mixing between two distinct source regions in the genesis of the Hangai basalts. Older basalts, previously dated at 5.91 ± 0.02 Ma (Barry et al., 2003), are derived from a component with an asthenospheric signature similar to depleted Indian MORB. Younger basalts are increasingly mixed with a component with lower Pb and Sr ratios and an enriched trace element signature, which is similar in composition to some lamproites erupted in the western USA (Mirnejad and Bell, 2006). This represents a transition from asthenospheric to lithospheric melting through time. Furthermore, <span class="hlt">studies</span> on mantle xenoliths from across the Hangai Dome indicate an elevated geotherm under the centre of the dome and significantly cooler conditions at its margins, interpreted to be the result of mantle upwellling (Harris et al., in review). Further numerical modelling will assess the relative contributions from lithospheric and asthenospheric sources in the genesis of these basalts, and contribute to understanding this enigmatic volcanic region. Barry, T. L., Saunders, A. D., Kempton, P. D., Windley, B.F., Pringle, M.S., Dorjnamjaa</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70023489','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70023489"><span id="translatedtitle"><span class="hlt">Isotope</span> geochemistry and fluid inclusion <span class="hlt">study</span> of skarns from Vesuvius</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Gilg, H.A.; Lima, A.; Somma, R.; Belkin, H.E.; de Vivo, B.; Ayuso, R.A.</p> <p>2001-01-01</p> <p>We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd <span class="hlt">isotope</span> data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopite, F-bearing vesuvianite, wollastonite, gehlenite, meionite, forsterite, clinohumite, anorthite and Mg-poor calcite with accessory apatite, spinell, magnetite, perovskite, baddeleyite, and various REE-, U-, Th-, Zr- and Ti-rich minerals. Four major types of fluid inclusions were observed in wollastonite, vesuvianite, gehlenite, clinopyroxene and calcite: a) primary silicate melt inclusions (THOM = 1000-1050??C), b) CO2 ?? H2S-rich fluid inclusions (THOM = 20-31.3??C into the vapor phase), c) multiphase aqueous brine inclusions (THOM = 720-820??C) with mainly sylvite and halite daughter minerals, and d) complex chloride-carbonate-sulfate-fluoride-silicate-bearing saline-melt inclusions (THOM = 870-890??C). The last inclusion type shows evidence for immiscibility between several fluids (silicate melt - aqueous chloride-rich liquid - carbonate/sulfate melt?) during heating and cooling below 870??C. There is no evidence for fluid circulation below 700??C and participation of externally derived meteoric fluids in skarn formation. Skarns have considerably variable 206Pb/204Pb (19.047-19.202), 207Pb/204Pb (15.655-15.670), and 208Pb/204Pb (38.915-39.069) and relatively low 143Nd/144Nd (0.51211-0.51244) ratios. The carbon and oxygen <span class="hlt">isotope</span> compositions of skarn calcites (??13CV-PDB = -5.4 to -1.1???; ??18OV-SMOW = 11.7 to 16.4???) indicate formation from a 18O- and 13C-enriched fluid. The <span class="hlt">isotope</span> composition of skarns and the presence of silicate melt inclusion-bearing wollastonite nodules suggests assimilation of carbonate wall rocks by the alkaline magma at moderate depths (< 5</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP21A1303C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP21A1303C"><span id="translatedtitle">Lead <span class="hlt">isotopes</span> in Southern Ocean marine sediments: implications for paleoclimatic provenance and seawater <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cook, C. P.; Martin, E. E.</p> <p>2014-12-01</p> <p> major and trace elements. Preliminary results, along with those of parallel detrital <span class="hlt">studies</span>, suggest Pb <span class="hlt">isotopes</span> are a viable tool for paleoclimatic <span class="hlt">studies</span> in areas of the Southern Ocean proximal to Antarctica, and our new data forms an important framework for future <span class="hlt">studies</span> in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.V51B2787T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.V51B2787T"><span id="translatedtitle">Juvenile accretion (2360-2330 Ma) in the São Francisco Craton, and implications for the Columbia supercontinent: evidence from U-Pb zircon ages, <span class="hlt">Sr-Nd</span>-Hf and geochemical constraints</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Teixeira, W.; Ávila, C.</p> <p>2012-12-01</p> <p>The Mineiro and the Itabuna-Salvador-Curaçá belts are segments of an Early Proterozoic orogen, in the São Francisco/West Congo-North Gabon craton. The latter segment includes island-arc rocks with preserved portions of the accretionary prism and back-arc basins, developed between 2.4 and 2.0 Ga. The Mineiro belt evolved marginally to the Minas passive margin basin (<2.55 to 2.35 Ga). It contains mainly granitoid rocks with ages between 2.25-2.20 Ga and 2.12-2.08 Ga, along with coeval back arc sequences. The overall framework includes regional metamorphism and related faults and shear zones across both belts. Similar tectonic features are portrayed by the West Central African belt (of Eburnean age) by considering the early contiguous African counterpart. We present an integrated geochronologic and geochemical <span class="hlt">study</span> for the Resende Costa orthogneiss (Mineiro belt): the gneissic rocks are slightly metaluminous to peraluminous, subalkaline, show varied SiO2 (69 to 73wt.%) contents, and low K2O and high- Na2O +CaO ones. Chemically, they are compatible with high Al2O3 trondhjemites. They also show weak positive Eu/Eu* anomalies, low Rb (24 to 70ppm), Ba (500 to 1000ppm), Th (2.1 to 8.5ppm) contents, very high Sr/Y ratios (75 to 158) and variable LREE and low HREE patterns (Yb < 1.23 ppm). The Resende Costa pluton yields two U-Pb (LA-ICPMS) zircon crystallization ages (2358±10 Ma and 2356±12 Ma), while the zircon rims yield 2133±32 Ma, interpreted as the age of metamorphism. The Sm/Nd TDM whole rock model ages are between 2.35-2.50 Ga, whereas the ɛNd(t) values range from +1.2 to +3.0, ɛSr(t) from +10 to -6, and ɛHf(t) in zircon between -3 to +6. The nearby Ramos gneissic pluton gives U-Pb zircon age of 2331±17 Ma, TDM age of 2.4 Ga, ɛNd(t) +2.2, ɛHf(t) (-9/+9) and ɛSr(t) +40 values. The overall signature implies to short crustal residence for the protholiths with minor contamination during the petrogenesis. Published data reveal that the nearby Lagoa Dourada</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JSAES..41...65G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JSAES..41...65G"><span id="translatedtitle"><span class="hlt">Sr-Nd</span> constraints and trace-elements geochemistry of selected Paleo and Mesoproterozoic mafic dikes and related intrusions from the South American Platform: Insights into their mantle sources and geodynamic implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Girardi, V. A. V.; Teixeira, W.; Mazzucchelli, M.; Corrêa da Costa, P. C.</p> <p>2013-01-01</p> <p>The <span class="hlt">study</span> of selected mafic intrusions from cratonic areas of the South American Platform shows considerable differences among their mantle sources and geodynamic features, particularly regarding the dikes from the SW Amazonian and São Francisco Cratons. The tholeiites from the SW Amazonian Craton, which belong to the Serra da Providência Intrusive Suite (1.55 Ga), the Nova Lacerda swarm (1.44 Ga), the Colorado Complex (1.35 Ga), and the Nova Brasilândia Group (1.10 Ga), originated from a mantle source composed mainly of a N-MORB end-member, with a variable addition of slab fluids (up to 30%, according to the adopted model) from oceanic lithosphere due to episodic subductions during the Mesoproterozoic. Mafic intrusions from Nova Lacerda swarm and Colorado Complex are related to arc settings formed during the 1.47-1.35 Ga closure of the oceanic domain separating the Amazonian Craton and the Paraguá Terrane, whereas the tholeiites from the Serra da Providência Intrusive Suite and the Nova Brasilândia Group are considered intracratonic. The dike swarms of the São Francisco Craton are associated with intra-plate events. The inferred composition of the mantle source of the Lavras swarm (1.9 Ga) has a predominant E-MORB signature, and a modest contribution of up to 10% of an OIB component. The mantle composition underwent considerable changes during the Proterozoic, as indicated by the sources of the younger dikes, represented by the Diamantina (0.93 Ga) and the Salvador-Olivença swarms (0.92 Ga), to which considerable amount of slab derived fluids, probably from recycled crustal material, and OIB component were added. Changes in mantle composition and dikes intrusions could be related to the initial disruption of the Rodinia Supercontinent. The Florida (1.79 Ga) and Tandil (2.0 Ga) dikes are associated with extensional events of the Rio de La Plata Craton. In spite of the similarities between the tectonic framework of these swarms and that of Lavras (1.9 Ga</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211485J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211485J"><span id="translatedtitle">Column experiment to <span class="hlt">study</span> <span class="hlt">isotope</span> fractionation of volatile organic contaminants in porous media under unsaturated conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeannottat, Simon; Hunkeler, Daniel; Breider, Florian</p> <p>2010-05-01</p> <p>Pollution by organic contaminants such as petroleum hydrocarbons and chlorinated solvents is common in industrialized countries. The use of stable <span class="hlt">isotope</span> analysis is increasingly recognized as a powerful technique for investigating the behaviour of organic or inorganic contaminants. Recently, compound-specific <span class="hlt">isotope</span> analysis (CSIA) has proven to be an effective tool to confirm and quantify in-situ biodegradation by indigenous microbial populations in groundwater.In contrast, only few <span class="hlt">studies</span> have investigated the use of CSIA in the unsaturated zone. In the unsaturated zone, the main potential applications of CSIA include the assessment of biodegradation and the fingerprinting of different sources of petroleum hydrocarbon or chlorinated solvents vapours. However, it has to be taken into account that <span class="hlt">isotope</span> ratios in the unsaturated zone can vary due to diffusion and volatilization in addition to biodegradation. For application of <span class="hlt">isotope</span> methods in the unsaturated zone, it is crucial to quantify <span class="hlt">isotopic</span> fractionation resulting from physico-chemical and transport processes. The <span class="hlt">study</span> is focused on laboratory experiments that investigate the effect of vaporization and diffusion on <span class="hlt">isotope</span> ratios. The effect of diffusion is carried out using a column experiment setup that can be considered to represent VOC transport from a floating NAPL towards the atmosphere. Furthermore, additional column and batch experiments will be conducted to better understand the effect of biodegradation. Volatilization is <span class="hlt">studied</span> with an other experimental setup. In addition, a mathematical framework was developed to simulate the <span class="hlt">isotope</span> evolution in the column <span class="hlt">study</span>. Since the initial experiments aimed at investigating the effect of vaporization and diffusion only, the column is filled with dry quartz sand in order to avoid perturbations of concentration profiles by humidity or adsorption on organic matter. An activated sand will later be used for the biodegradation experiments. A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6149171','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6149171"><span id="translatedtitle">Neodymium <span class="hlt">isotopic</span> <span class="hlt">studies</span> of Precambrian banded iron formations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pimentel-Klose, M.R.</p> <p>1986-01-01</p> <p>The <span class="hlt">isotopic</span> composition of Nd is reported for 11 different Precambrian BIFs and suggests a trend of increasingly positive epsilon/sub Nd/(T) values with age. This trend is interpreted to reflect <span class="hlt">isotopic</span> variations in precambrian sea water. The Urucum and the Gunflint BIFs, both younger than 1.8 AE, yield negative epsilon/sub Nd/(T) values, between -4.6 and -1.1. The remaining BIFs, with ages between 1.85 and 3.4 AE, have predominantly positive values, between -0.7 and +4.0. The low UXSm/ UUNd ratio in BIFs is inconsistent with their REE being derived from rivers draining large proportions of greenstones. The positive, mantle-like values of BIFs older than 1.8 AE contrasts strongly with the negative, continental-like values of Phanerozoic sea water. Therefore, the REE budget of the oceans during most of the Precambrian was probably dominated by the hydrothermal circulation of sea water through MORBs and not by river waters, as today. A one order of magnitude higher hydrothermal contribution of Nd is suggested by the data for the Early Precambrian. This is most likely due to a higher hydrothermal water to river water flux ratio and/or a higher Nd concentration in hotter hydrothermal waters (>375 C) during this period. The large hydrothermal contribution of REE during the Early Precambrian can be explained best if the temperature of sea water fluxing through MORBs was higher than today. Experiments investigating the interaction between sea water and basalt have shown that the concentration of iron might have been about 20 times larger if the temperature of interaction was about 425 C. Such hot hydrothermal solutions could have been the most important source of iron in Precambrian BIFs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..APR.J9003L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..APR.J9003L"><span id="translatedtitle"><span class="hlt">Study</span> on nuclear structures of Te <span class="hlt">isotopes</span> beyond N = 82 shell closure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Pilsoo; Lee, Chun Sik; Moon, Chang-Bum; Eurica Ribf-87 Collaboration Collaboration</p> <p>2016-03-01</p> <p>Tellurium which has two valence protons above the Z = 50 proton shell closure is well known for collective behavior in low-lying states. Therefore, Te <span class="hlt">isotopes</span> are known to be a good test ground for <span class="hlt">studying</span> nuclear collective modes but also the effect of neutron-proton interaction on the shell evolution with variation of neutron numbers owing to the valence protons above Z = 50 . For this reason Te <span class="hlt">isotopes</span> always attract our attention, however, most available spectroscopic nuclear data of Te <span class="hlt">isotopes</span> remains below N = 82 , and experimental data is severely limited above N = 82 . Meanwhile, recent <span class="hlt">study</span> of 138Te by means of β- γ spectroscopy with fission fragments of 238U has provided us with new clues on excited states in 138Te, and the new experimental result has proposed new excited states that were unexpected in the previous theoretical <span class="hlt">studies</span>. This <span class="hlt">study</span> aims at understanding structural evolution in Te <span class="hlt">isotopes</span> above N = 82 with respect to below N = 82 including the new data set available today. In this presentation we discuss the nuclear structures and effective interactions in Te <span class="hlt">isotopes</span> above N = 82 based on the nuclear shell model and interacting boson approximations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16521167','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16521167"><span id="translatedtitle">The role of stable <span class="hlt">isotopes</span> in human identification: a longitudinal <span class="hlt">study</span> into the variability of <span class="hlt">isotopic</span> signals in human hair and nails.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fraser, I; Meier-Augenstein, W; Kalin, R M</p> <p>2006-01-01</p> <p>Recent natural catastrophes with large-scale loss of life have demonstrated the need for a new technique to provide information for disaster victim identification when DNA methods fail to yield the identification of an individual, or in other situations where authorities need to determine the recent geographical life history of people. The latter may be in relation to the identification of individuals detained on suspicion of terrorism or in relation to people-trafficking or smuggling. One proposed solution is the use of stable <span class="hlt">isotope</span> profiling (SIP) using <span class="hlt">isotope</span> ratio mass spectrometry (IRMS). Exploiting the link between the <span class="hlt">isotopic</span> signal of dietary components and the <span class="hlt">isotopic</span> composition of body tissue, the aim of this <span class="hlt">study</span> was to refine a non-invasive method of analysing human material such as scalp hair and fingernails using SIP and to assess the degree of natural variability in these profiles. Scalp hair and fingernail samples were collected from British and non-British volunteers at Queen's University Belfast every 2 weeks for a minimum of 8 months. Samples were analysed using IRMS to determine their <span class="hlt">isotopic</span> composition for 13C, 15N, 2H and 18O. The results of this longitudinal <span class="hlt">study</span> yielded information on the natural variability of the <span class="hlt">isotopic</span> composition of these tissues. The data demonstrate the relatively low degree of natural variation in the 13C/15N <span class="hlt">isotopic</span> abundance of scalp hair and fingernails whilst greater variations were recorded in the hydrogen and oxygen values of the same samples. The 15N and 18O values of nail are noticeably more variable than that of scalp hair from the same subject. A hypothesis explaining this trend is put forward based on the faster rate of formation of hair than of nails. This means that there is less time for the compounds forming hair to be affected by biochemical processes that could alter their <span class="hlt">isotopic</span> signature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007E%26PSL.254..272B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007E%26PSL.254..272B"><span id="translatedtitle">Tracing paleofluid circulations using iron <span class="hlt">isotopes</span>: A <span class="hlt">study</span> of hematite and goethite concretions from the Navajo Sandstone (Utah, USA)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Busigny, Vincent; Dauphas, Nicolas</p> <p>2007-02-01</p> <p>Iron concentrations and <span class="hlt">isotopic</span> compositions were measured in spherical hematite and goethite concretions, together with associated red (Fe-oxide coated) and white (bleached) sandstones from the Jurassic Navajo formation, Utah (USA). Earlier <span class="hlt">studies</span> showed that, in the Navajo Sandstone, reducing fluids (presumably rich in hydrocarbons) mobilized Fe present as Fe-oxide coatings on detrital quartz grains. Dissolved Fe then precipitated as spherical concretions by interaction with oxidizing groundwater. Despite being depleted in Fe by ˜ 50%, the bleached sandstones have Fe <span class="hlt">isotopic</span> compositions similar to adjacent red sandstones (˜ 0‰/amu relative to IRMM-014). This shows that dissolution of Fe-oxide did not produce significant <span class="hlt">isotope</span> fractionation, in agreement with previous experimental <span class="hlt">studies</span> of abiotic Fe-oxide dissolution. In contrast, the concretions are depleted in the heavy <span class="hlt">isotopes</span> of iron by - 0.07 to - 0.68‰/amu. This is opposite to the expected fractionation for partial Fe oxidation, which tends to enrich the precipitate in the heavy <span class="hlt">isotopes</span>. Several scenarios are considered for explaining the measured Fe <span class="hlt">isotopic</span> compositions. Although diffusion might be an important process in controlling the growth of spherical concretions, the associated <span class="hlt">isotopic</span> fractionation is negligible compared to the observed variations. Kinetic <span class="hlt">isotope</span> fractionation during precipitation can be ruled out as well because no <span class="hlt">isotopic</span> zonation is seen within indurated concretions and Fe <span class="hlt">isotope</span> evidence supports the occurrence of dissolution-reprecipitation reactions consistent with equilibrium growth conditions. The Fe <span class="hlt">isotopic</span> compositions of the concretions are best explained by evolution of the fluid composition through precipitation and/or adsorption of <span class="hlt">isotopically</span> heavy Fe during fluid flow through the sandstone. This scenario is supported by a regional trend in the <span class="hlt">isotopic</span> composition of Fe, showing that this element was transported in fluids over several</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PalOc..25.2211M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PalOc..25.2211M"><span id="translatedtitle">Combined carbonate carbon <span class="hlt">isotopic</span> and cellular ultrastructural <span class="hlt">studies</span> of individual benthic foraminifera: Method description</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, Jonathan B.; Bernhard, Joan M.; Curtis, Jason; Rathburn, Anthony E.</p> <p>2010-06-01</p> <p>Carbon <span class="hlt">isotopes</span> of foraminiferal tests provide a widely used proxy for past oceanographic environmental conditions. This proxy can be calibrated using live specimens, which are reliably identified with observations of cell ultrastructure. Observations of ultrastructures can also be used for <span class="hlt">studies</span> of biological characteristics such as diet and presence of symbionts. Combining biological and <span class="hlt">isotopic</span> <span class="hlt">studies</span> on individual foraminifera could provide novel information, but standard <span class="hlt">isotopic</span> methods destroy ultrastructures by desiccating specimens and observations of ultrastructure require removal of carbonate tests, preventing <span class="hlt">isotope</span> measurements. The approach described here preserves cellular ultrastructure during <span class="hlt">isotopic</span> analyses by keeping the foraminifera in an aqueous buffer (Phosphate Buffered Saline (PBS)). The technique was developed and standardized with 36 aliquots of NBS-19 standard of similar weight to foraminiferal tests (5 to 123 μg). Standard errors ranged from ± 0.06 to ± 0.85‰ and were caused by CO2 contaminants dissolved in the PBS. The technique was used to measure δ13C values of 96 foraminifera, 10 of which do not precipitate carbonate tests. Calcareous foraminiferal tests had corrected carbon <span class="hlt">isotope</span> ratios of -8.5 to +3.2‰. This new technique allows comparisons of <span class="hlt">isotopic</span> compositions of tests made by foraminifera known to be alive at the time of collection with their biological characteristics such as prey composition and presence or absence of putative symbionts. The approach may be applied to additional biomineralizing organisms such as planktonic foraminifera, pteropods, corals, and coccolithophores to elucidate certain biological controls on their paleoceanographic proxy signatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120001962','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120001962"><span id="translatedtitle">Coordinated Oxygen <span class="hlt">Isotopic</span> and Petrologic <span class="hlt">Studies</span> of CAIS Record Varying Composition of Protosolar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simon, Justin I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.</p> <p>2012-01-01</p> <p>Ca-, Al-rich inclusions (CAIs) record the O-<span class="hlt">isotope</span> composition of Solar nebular gas from which they grew [1]. High spatial resolution O-<span class="hlt">isotope</span> measurements afforded by ion microprobe analysis across the rims and margin of CAIs reveal systematic variations in (Delta)O-17 and suggest formation from a diversity of nebular environments [2-4]. This heterogeneity has been explained by <span class="hlt">isotopic</span> mixing between the O-16-rich Solar reservoir [6] and a second O-16-poor reservoir (probably nebular gas) with a "planetary-like" <span class="hlt">isotopic</span> composition [e.g., 1, 6-7], but the mechanism and location(s) where these events occur within the protoplanetary disk remain uncertain. The orientation of large and systematic variations in (Delta)O-17 reported by [3] for a compact Type A CAI from the Efremovka reduced CV3 chondrite differs dramatically from reports by [4] of a similar CAI, A37 from the Allende oxidized CV3 chondrite. Both <span class="hlt">studies</span> conclude that CAIs were exposed to distinct, nebular O-<span class="hlt">isotope</span> reservoirs, implying the transfer of CAIs among different settings within the protoplanetary disk [4]. To test this hypothesis further and the extent of intra-CAI O-<span class="hlt">isotopic</span> variation, a pristine compact Type A CAI, Ef-1 from Efremovka, and a Type B2 CAI, TS4 from Allende were <span class="hlt">studied</span>. Our new results are equally intriguing because, collectively, O-<span class="hlt">isotopic</span> zoning patterns in the CAIs indicate a progressive and cyclic record. The results imply that CAIs were commonly exposed to multiple environments of distinct gas during their formation. Numerical models help constrain conditions and duration of these events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvC..92c4309G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvC..92c4309G"><span id="translatedtitle">Nuclear shape coexistence in Po <span class="hlt">isotopes</span>: An interacting boson model <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>García-Ramos, J. E.; Heyde, K.</p> <p>2015-09-01</p> <p>Background: The lead region, Po, Pb, Hg, and Pt, shows up the presence of coexisting structures having different deformation and corresponding to different particle-hole configurations in the shell-model language. Purpose: We intend to <span class="hlt">study</span> the importance of configuration mixing in the understanding of the nuclear structure of even-even Po <span class="hlt">isotopes</span>, where the shape coexistence phenomena are not clear enough. Method: We <span class="hlt">study</span> in detail a long chain of polonium <span class="hlt">isotopes</span>, Po-208190, using the interacting boson model with configuration mixing (IBM-CM). We fix the parameters of the Hamiltonians through a least-squares fit to the known energies and absolute B (E 2 ) transition rates of states up to 3 MeV. Results: We obtained the IBM-CM Hamiltonians and we calculate excitation energies, B (E 2 ) 's, electric quadrupole moments, nuclear radii and <span class="hlt">isotopic</span> shifts, quadrupole shape invariants, wave functions, and deformations. Conclusions: We obtain a good agreement with the experimental data for all the <span class="hlt">studied</span> observables and we conclude that shape coexistence phenomenon is hidden in Po <span class="hlt">isotopes</span>, very much as in the case of the Pt <span class="hlt">isotopes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.137....1S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.137....1S"><span id="translatedtitle">Small-scale <span class="hlt">studies</span> of roasted ore waste reveal extreme ranges of stable mercury <span class="hlt">isotope</span> signatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, Robin S.; Wiederhold, Jan G.; Jew, Adam D.; Brown, Gordon E.; Bourdon, Bernard; Kretzschmar, Ruben</p> <p>2014-07-01</p> <p>Active and closed Hg mines are significant sources of Hg contamination to the environment, mainly due to large volumes of mine waste material disposed of on-site. The application of Hg <span class="hlt">isotopes</span> as source tracer from such contaminated sites requires knowledge of the Hg <span class="hlt">isotope</span> signatures of different materials potentially released to the environment. Previous work has shown that calcine, the waste residue of the on-site ore roasting process, can exhibit distinct Hg <span class="hlt">isotope</span> signatures compared with the primary ore. Here, we report results from a detailed small-scale <span class="hlt">study</span> of Hg <span class="hlt">isotope</span> variations in calcine collected from the closed New Idria Hg mine, San Benito County, CA, USA. The calcine samples exhibited different internal layering features which were investigated using optical microscopy, micro X-ray fluorescence, micro X-ray absorption spectroscopy (μ-XAS), and stable Hg <span class="hlt">isotope</span> analysis. Significant Fe, S, and Hg concentration gradients were found across the different internal layers. <span class="hlt">Isotopic</span> analyses revealed an extreme variation with pronounced <span class="hlt">isotopic</span> gradients across the internal layered features. Overall, δ202Hg (±0.10‰, 2 SD) describing mass-dependent fractionation (MDF) ranged from -5.96 to 14.49‰, which is by far the largest range of δ202Hg values reported for any environmental sample. In addition, Δ199Hg (±0.06‰, 2 SD) describing mass-independent fractionation (MIF) ranged from -0.17 to 0.21‰. The μ-XAS analyses suggested that cinnabar and metacinnabar are the dominant Hg-bearing phases in the calcine. Our results demonstrate that the incomplete roasting of HgS ores in Hg mines can cause extreme mass-dependent Hg <span class="hlt">isotope</span> fractionations at the scale of individual calcine pieces with enrichments in both light and heavy Hg <span class="hlt">isotopes</span> relative to the primary ore signatures. This finding has important implications for the application of Hg <span class="hlt">isotopes</span> as potential source tracers for Hg released to the environment from closed Hg mines and</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4048731','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4048731"><span id="translatedtitle">Stable <span class="hlt">isotope</span>-labeling <span class="hlt">studies</span> in metabolomics: new insights into structure and dynamics of metabolic networks</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chokkathukalam, Achuthanunni; Kim, Dong-Hyun; Barrett, Michael P; Breitling, Rainer; Creek, Darren J</p> <p>2014-01-01</p> <p>The rapid emergence of metabolomics has enabled system-wide measurements of metabolites in various organisms. However, advances in the mechanistic understanding of metabolic networks remain limited, as most metabolomics <span class="hlt">studies</span> cannot routinely provide accurate metabolite identification, absolute quantification and flux measurement. Stable <span class="hlt">isotope</span> labeling offers opportunities to overcome these limitations. Here we describe some current approaches to stable <span class="hlt">isotope</span>-labeled metabolomics and provide examples of the significant impact that these <span class="hlt">studies</span> have had on our understanding of cellular metabolism. Furthermore, we discuss recently developed software solutions for the analysis of stable <span class="hlt">isotope</span>-labeled metabolomics data and propose the bioinformatics solutions that will pave the way for the broader application and optimal interpretation of system-scale labeling <span class="hlt">studies</span> in metabolomics. PMID:24568354</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5262894','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5262894"><span id="translatedtitle"><span class="hlt">Isotopic</span> and geochemical <span class="hlt">studies</span> of fluid-rock interactions and the chemical evolution of the oceans</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Derry, L.A.</p> <p>1989-01-01</p> <p>The <span class="hlt">isotopic</span> compositions of Sr and Nd, and the abundances of rare earth elements (REE) are used to <span class="hlt">study</span> various types of fluid-rock interactions in the Earth's crust. The <span class="hlt">isotopic</span> compositions of Sr and Nd and REE patterns in marine chemical sediments of Precambrian age are used to estimate the relative importance of continental weathering versus submarine hydrothermal activity in determining the chemical mass balance of the Precambrian oceans. Major and trace element abundances and Sr and Nd <span class="hlt">isotopes</span> are used to quantify the degree of interaction of a carbonatite fluid-magmatic system with felsic crust, and to constrain the <span class="hlt">isotopic</span> characteristics of the mantle source region. The <span class="hlt">isotopic</span> composition of Sr is reported from a well characterized sequence of Upper Proterozoic carbonates from Svalbard and east Greenland. A simple model of carbonate recycling and <span class="hlt">isotopic</span> mass balance calculations illustrate that sedimentary recycling can have a strong influence on Sr in the oceans. REE patterns from Precambrian banded iron formations (BIFs) are very similar to modern metalliferous sediments, and imply that the overall REE pattern of Precambrian seawater was similar to today. The mantle-like {var epsilon}{sub Nd} values and positive Eu anomalies imply that the source of the REE in the BIFs was submarine hydrothermal activity. The implications of a large hydrothermal flux of reduced Fe on the redox controls of the Precambrian atmosphere are explored, and a testable hypothesis is developed. The mass balance of Eu in the oceans is affected by preferential scavenging at hydrothermal sites. Data from the Cherry Hill, CA mineralizing system imply a complex plumbing system and a long residence time for the water. <span class="hlt">Isotopic</span> data from the Fen alkaline complex, Norway, define mixing trends between mantle derived magmas or magmatic fluids and old crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1052712','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1052712"><span id="translatedtitle">Strontium <span class="hlt">Isotope</span> <span class="hlt">Study</span> of Coal Untilization By-products Interacting with Environmental Waters</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Spivak-Birndorf, Lev J; Stewart, Brian W; Capo, Rosemary C; Chapman, Elizabeth C; Schroeder, Karl T; Brubaker, Tonya M</p> <p>2011-09-01</p> <p>Sequential leaching experiments on coal utilization by-products (CUB) were coupled with chemical and strontium (Sr) <span class="hlt">isotopic</span> analyses to better understand the influence of coal type and combustion processes on CUB properties and the release of elements during interaction with environmental waters during disposal. Class C fly ash tended to release the highest quantity of minor and trace elements—including alkaline earth elements, sodium, chromium, copper, manganese, lead, titanium, and zinc—during sequential extraction, with bottom ash yielding the lowest. Strontium <span class="hlt">isotope</span> ratios ({sup 87}Sr/{sup 86}Sr) in bulk-CUB samples (total dissolution of CUB) are generally higher in class F ash than in class C ash. Bulk-CUB ratios appear to be controlled by the geologic source of the mineral matter in the feed coal, and by Sr added during desulfurization treatments. Leachates of the CUB generally have Sr <span class="hlt">isotope</span> ratios that are different than the bulk value, demonstrating that Sr was not <span class="hlt">isotopically</span> homogenized during combustion. Variations in the Sr <span class="hlt">isotopic</span> composition of CUB leachates were correlated with mobility of several major and trace elements; the data suggest that arsenic and lead are held in phases that contain the more radiogenic (high-{sup 87}Sr/{sup 86}Sr) component. A changing Sr <span class="hlt">isotope</span> ratio of CUB-interacting waters in a disposal environment could forecast the release of certain strongly bound elements of environmental concern. This <span class="hlt">study</span> lays the groundwork for the application of Sr <span class="hlt">isotopes</span> as an environmental tracer for CUB–water interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.B14B..01E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.B14B..01E"><span id="translatedtitle"><span class="hlt">Isotope</span> geochemistry and the <span class="hlt">study</span> of habitability and life on other planets (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eiler, J.</p> <p>2010-12-01</p> <p>The question of life on other planets might be solved by a remarkable discovery — a martian coquina, or perhaps a tentacle print on a distant landscape. But, until this happens, evidence for life and, more generally, habitability will use indirect geochemical arguments such as <span class="hlt">isotope</span> thermometers and biomarkers (molecular, <span class="hlt">isotopic</span>, and elemental fingerprints of biology)., Understanding this evidence will also demand a quantitative planetary history based on <span class="hlt">isotopic</span> dating. Laboratory <span class="hlt">study</span> of samples derived from Mars or other solar-system bodies will be a focus of geochemical investigations aimed at such assessments. Examples of how this will be done can be found in <span class="hlt">studies</span> of the Precambrian geologic record and Martian meteorites. Debates regarding environmental conditions and biogenicity of minerals and organic matter are common in the <span class="hlt">study</span> of such materials. These controversies derive from simple but refractory problems with the geochemical principles we employ: Indicators of metabolism can be mimicked by abiologic reactions; paleo-environmental proxies generally require an understanding of related geochemical cycles (e.g., the <span class="hlt">isotopic</span> budget of water); and, though many organic molecules are unambiguous biomarkers, diagenesis can transform them into compounds that resemble products of abiogenic organic synthesis. If planetary sample return is to produce definitive geochemical constraints on habitability and biology, we will require either luck or a new class of geochemical tools that explicitly address these problems. The spatial distribution of rare <span class="hlt">isotopes</span> within molecular structures, including ‘clumping’ and position-specific <span class="hlt">isotope</span> effects, offer new geochemical tools that could provide such solutions. For example, even a simple molecule like acetic acid (C2H4O2) has more than 200 distinct <span class="hlt">isotopic</span> configurations when spatial distribution of <span class="hlt">isotopes</span> is considered, and the proportions of these could reflect formation temperature, the nature of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C13A0800H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C13A0800H"><span id="translatedtitle">Elemental concentrations and inorganic <span class="hlt">isotopic</span> ratios in surface snow along the route to Dome Fuji, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirabayashi, M.; Nakazawa, F.; Azuma, K. G.; Motoyama, H.</p> <p>2015-12-01</p> <p>Snow ice sample in Antarctica contains particulate matter. Particulates originate from continent, volcano, sea, space, and organism. The particulate matter of continental origin contains many elements from minerals and rocks. The <span class="hlt">isotopic</span> ratio of an element reflects the origin and the history of the particle. Since the <span class="hlt">isotopic</span> ratio of inorganic species depends on the source, the information about the source contribution of particulate matter can be estimated by analyzing the <span class="hlt">isotopic</span> ratios of inorganic species. In this research, concentrations of inorganic species and <span class="hlt">isotopic</span> ratios of inorganic species (Ca, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>) in snow collected on the route form coastal area to Dome Fuji station in Antarctica were analyzed. The snow samples were collected along ca. 1000 km traverse route from Mikaeridai (S16; 69°01'S, 40°03'E, 590 m) to Dome Fuji station (77°19'S, 39°42'E, 3810 m) by the Japan Antarctica research expedition. Those samples were collected in the 2007/2008 and 2009/2010 austral summer. The samples were transported to Japan without thawing. The quantitative analyses of inorganic species were measured using ICP quadrupole type mass spectrometer. The <span class="hlt">isotopic</span> ratios of isolated inorganic species were measured using ICP magnetic field type mass spectrometer. Further results and discussion about the behavior and origin of sulfur species in snow will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5802923','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5802923"><span id="translatedtitle">Stable <span class="hlt">isotope</span> <span class="hlt">studies</span> of nicotine kinetics and bioavailability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Benowitz, N.L.; Jacob, P. 3d.; Denaro, C.; Jenkins, R. )</p> <p>1991-03-01</p> <p>The stable <span class="hlt">isotope</span>-labeled compound 3',3'-dideuteronicotine was used to investigate the disposition kinetics of nicotine in smokers, the systemic absorption of nicotine from cigarette smoke, and the bioavailability of nicotine ingested as oral capsules. Blood levels of labeled nicotine could be measured for 9 hours after a 30-minute intravenous infusion. Analysis of disposition kinetics in 10 healthy men revealed a multiexponential decline after the end of an infusion, with an elimination half-life averaging 203 minutes. This half-life was longer than that previously reported, indicating the presence of a shallow elimination phase. Plasma clearance averaged 14.6 ml/min/kg. The average intake of nicotine per cigarette was 2.29 mg. A cigarette smoke-monitoring system that directly measured particulate matter in smoke was evaluated in these subjects. Total particulate matter, number of puffs on the cigarette, total puff volume, and time of puffing correlated with the intake of nicotine from smoking. The oral bioavailability of nicotine averaged 44%. This bioavailability is higher than expected based on the systemic clearance of nicotine and suggests that there may be significant extrahepatic metabolism of nicotine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6822495','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6822495"><span id="translatedtitle"><span class="hlt">Isotope</span> tracer <span class="hlt">studies</span> of diffusion in silicates and of geological transport processes using actinide elements</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wasserburg, G.J.</p> <p>1992-01-01</p> <p>The following are reported: high abundance sensitivity mass spectrometer for U-Th <span class="hlt">studies</span>; [sup 238]U-[sup 230]Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th <span class="hlt">studies</span>; resonance ionization mass spectrometry of Os and Ti <span class="hlt">isotopes</span>; and self-diffusion of Mg.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6823030','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6823030"><span id="translatedtitle"><span class="hlt">Isotope</span> effect <span class="hlt">studies</span> of the pyruvate-dependent histidine decarboxylase from Lactobacillus 30a</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Abell, L.M.; O'Leary, M.H.</p> <p>1988-08-09</p> <p>The decarboxylation of histidine by the pyruvate-dependent histidine decarboxylase of Lactobacillus 30 a shows a carbon <span class="hlt">isotope</span> effect k/sup 12//k/sup 13/ = 1.0334 +/- 0.0005 and a nitrogen <span class="hlt">isotope</span> effect k/sup 14//k/sup 15/ = 0.9799 +/- 0.0006 at pH 4.8, 37/sup 0/C. The carbon <span class="hlt">isotope</span> effect is slightly increased by deuteriation of the substrate and slightly decreased in D/sub 2/O. The observed nitrogen <span class="hlt">isotope</span> effect indicates that the imine nitrogen in the substrate-Schiff base intermediate complex is ordinarily protonated, and the pH dependence of the carbon <span class="hlt">isotope</span> effect indicates that both protonated and unprotonated forms of this intermediate are capable of undergoing decarboxylation. As with the pyridoxal 5'-phosphate dependent enzyme, Schiff base formation and decarboxylation are jointly rate-limiting, with the intermediate histidine-pyruvate Schiff base showing a decarboxylation/Schiff base hydrolysis ratio of 0.5-1.0 at pH 4.8. The decarboxylation transition state is more reactant-like for the pyruvate-dependent enzyme than for the pyridoxal 5'-phosphate dependent enzyme. These <span class="hlt">studies</span> find no particular energetic or catalytic advantage to the use of pyridoxal 5'-phosphate over covalently bound pyruvate in catalysis of the decarboxylation of histidine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/932477','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/932477"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of Contaminant Transport at the Hanford Site,WA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Christensen, J.N.; Conrad, M.E.; DePaolo, D.J.; Dresel, P.E.</p> <p>2006-11-01</p> <p>Processes of fluid flow and chemical transport through thevadose zone can be characterized through the <span class="hlt">isotopic</span> systematics ofnatural soils, minerals, pore fluids and groundwater. In thiscontribution, we first review our research using measured isotopicvariations, due both to natural and site related processes, of theelements H, O, N, Sr and U, to <span class="hlt">study</span> the interconnection between vadosezone and groundwater contamination at the Hanford Site in south-centralWashington. We follow this brief review with a presentation of new datapertaining to vadose zone and groundwater contamination in the WMAT-TX-TY vicinity. Uranium (U) <span class="hlt">isotopic</span> data for the C3832 core (WMA TX)indicates the involvement of processed natural U fuel, and links theobserved U contamination to the nearby single shelled tank TX-104. Thedata also precludes contamination from an early 1970 s TX-107 leak. Inthe case of the C4104 core (WMA T), the U <span class="hlt">isotopic</span> data indicates amixture of processed natural and enriched U fuels consistent with themajor leak from T-106 in 1973. Uranium and Strontium <span class="hlt">isotopic</span> data forthe cores also provides direct evidence for chemical interaction betweenhigh-pH waste fluid and sediment. <span class="hlt">Isotopic</span> data for groundwater nitratecontamination in the vicinity of WMA-T strongly suggests high-level tankwaste (most likely from T-106) as the source of very high 99Tcconcentrations recently observed at the NE corner of WMAT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22311290','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22311290"><span id="translatedtitle">Laboratory <span class="hlt">study</span> of nitrate photolysis in Antarctic snow. II. <span class="hlt">Isotopic</span> effects and wavelength dependence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Berhanu, Tesfaye A.; Erbland, Joseph; Savarino, Joël; Meusinger, Carl; Johnson, Matthew S.; Jost, Rémy; Bhattacharya, S. K.</p> <p>2014-06-28</p> <p>Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these <span class="hlt">studies</span> (see also Paper I by Meusinger et al. [“Laboratory <span class="hlt">study</span> of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry,” J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable <span class="hlt">isotopes</span> in nitrate ({sup 15}N, {sup 17}O, and {sup 18}O) provide additional information concerning post-depositional processes. Here, we present results from <span class="hlt">studies</span> of the wavelength-dependent <span class="hlt">isotope</span> effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and <span class="hlt">isotopic</span> composition (δ{sup 15}N, δ{sup 18}O, and Δ{sup 17}O). From these measurements an average photolytic <span class="hlt">isotopic</span> fractionation of {sup 15}ε = (−15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic <span class="hlt">isotopic</span> fractionation of {sup 15}ε = (−47.9 ± 6.8)‰, in good agreement with fractionations determined by previous <span class="hlt">studies</span> for the East Antarctic Plateau which range from −40 to −74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of {sup 14}NO{sub 3}{sup −} and {sup 15}NO{sub 3}{sup −} in snow at a chosen temperature. The nitrogen <span class="hlt">isotopic</span> fractionations obtained by applying</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22684401','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22684401"><span id="translatedtitle">Re-introduction of a novel approach to the use of stable <span class="hlt">isotopes</span> in pharmacokinetic <span class="hlt">studies</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Parr, Alan; Gupta, Manish; Montague, Timothy H; Hoke, Frank</p> <p>2012-09-01</p> <p>The purpose of this investigation is to evaluate the scientific benefits of a novel approach in using stable <span class="hlt">isotopes</span> to reduce the number of subjects needed to perform relative bioavailability and bioequivalence pharmacokinetic <span class="hlt">studies</span> for formulations that are qualitatively and quantitatively the same and quality by design (QbD) pharmacokinetic <span class="hlt">studies</span>. The stable <span class="hlt">isotope</span> approach was investigated using simulations to determine the impact this approach would have on the estimation of variability and, subsequently, the sample size for a bioequivalence <span class="hlt">study</span>. A biostudy was conducted in dogs in a two period crossover to explore the viability of the stable <span class="hlt">isotope</span> approach. For a drug product with within-subject variability (CV(w)) of 50% and assuming a correlation of 0.95 between the enriched and non-enriched pharmacokinetics (PK), simulations showed that the variability can be reduced by 70% and the required sample size can be reduced by 90% while maintaining 90% power to demonstrate bioequivalence. The dog <span class="hlt">study</span> showed a strong correlation (R(2), > 0.99) between the enriched and non-enriched area under the curve and maximum observed concentration, and a significant reduction in the variability (reduction in % coefficient of variation from 79.9% to 6.3%). Utilization of a stable <span class="hlt">isotope</span> approach can markedly improve the efficiency and accuracy of bioavailability and bioequivalence <span class="hlt">studies</span> particularly for highly variable drugs in formulations that are qualitatively and quantitatively the same and for <span class="hlt">studies</span> designed for QbD investigations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005NIMPB.240..726L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005NIMPB.240..726L"><span id="translatedtitle">Potential of Sr <span class="hlt">isotopic</span> analysis in ceramic provenance <span class="hlt">studies</span>: Characterisation of Chinese stonewares</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Bao-Ping; Zhao, Jian-Xin; Greig, Alan; Collerson, Kenneth D.; Zhuo, Zhen-Xi; Feng, Yue-Xin</p> <p>2005-11-01</p> <p>We compare the trace element and Sr <span class="hlt">isotopic</span> compositions of stoneware bodies made in Yaozhou and Jizhou to characterise these Chinese archaeological ceramics and examine the potential of Sr <span class="hlt">isotopes</span> in provenance <span class="hlt">studies</span>. Element concentrations determined by ICP-MS achieve distinct characterisation for Jizhou samples due to their restricted variation, yet had limited success with Yaozhou wares because of their large variability. In contrast, 87Sr/86Sr ratios in Yaozhou samples have a very small variation and are all significantly lower than those of Jizhou samples, which show a large variation and cannot be well characterised with Sr <span class="hlt">isotopes</span>. Geochemical interpretation reveals that 87Sr/86Sr ratios will have greater potential to characterise ceramics made of low Rb/Sr materials such as kaolin clay, yet will show larger variations in ceramics made of high Rb/Sr materials such as porcelain stone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1171645','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1171645"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of O-O Bond Formation During Water Oxidation (SISGR)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Roth, Justine P.</p> <p>2015-03-03</p> <p><span class="hlt">Isotopic</span> <span class="hlt">Studies</span> of O-O Bond Formation During Water Oxidation (SISGR) Research during the project period focused primarily on mechanisms of water oxidation by structurally defined transition metal complexes. Competitive oxygen <span class="hlt">isotope</span> fractionation of water, mediated by oxidized precursors or reduced catalysts together with ceric, Ce(IV), ammonium nitrate in aqueous media, afforded oxygen-18 kinetic <span class="hlt">isotope</span> effects (O-18 KIEs). Measurement, calculation, and interpretation of O-18 KIEs, described in the accompanying report has important ramifications for the production of electricity and solar hydrogen (as fuel). The catalysis division of BES has acknowledged that understanding mechanisms of transition metal catalyzed water oxidation has major ramifications, potentially leading to transformation of the global economy and natural environment in years to come. Yet, because of program restructuring and decreased availability of funds, it was recommended that the Solar Photochemistry sub-division of BES would be a more appropriate parent program for support of continued research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJMPE..2550024S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJMPE..2550024S"><span id="translatedtitle"><span class="hlt">Study</span> of 242-248Cm <span class="hlt">isotopes</span> in the projected shell model framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadiq, Saiqa; Devi, Rani; Khosa, S. K.</p> <p>2016-04-01</p> <p>The projected shell model framework is employed to <span class="hlt">study</span> the band spectra in 242-248Cm <span class="hlt">isotopes</span>. The present calculations reproduce the available experimental data on the yrast bands. Besides this, B(E2) transition probabilities of even-even Cm <span class="hlt">isotopes</span> have also been calculated. The low spin states of yrast band are seen to arise purely from zero-quasi-particle (o-qp) intrinsic states whereas the high spin states have multi-quasi-particle structure. For the odd-neutron (odd-N) <span class="hlt">isotopes</span>, the calculated results qualitatively reproduce the available data on ground and lowest excited state bands for 243,245Cm. However, for 247Cm the negative-parity ground state band is in reasonable agreement with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70013022','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70013022"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">studies</span> of the late Archean plutonic rocks of the Wind River Range, Wyoming.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stuckless, J.S.; Hedge, C.E.; Worl, R.G.; Simmons, K.R.; Nkomo, I.T.; Wenner, D.B.</p> <p>1985-01-01</p> <p>Two late Archaean intrusive events were documented in the Wind River Range by <span class="hlt">isotopic</span> <span class="hlt">studies</span> of the Rb-Sr and U-Th-Pb systems in whole-rock samples and the U-Pb systematics for zircon. An age of approx 2630(20) m.y. for the Louis Lake batholith and apparent ages of 2504(40) to 2575(50) m.y. for the Bear Ears pluton were obtained. Post-magmatic hydrothermal events approximately Tertiary in age, lowered delta 18O values and disturbed parent-daughter relationships in most of the <span class="hlt">isotopic</span> systems investigated. The two intrusive units apparently were derived from different protoliths. Initial <span class="hlt">isotopic</span> ratios and petrochemistry for the Louis Lake batholith are consistent with an early Archaean trondhjemitic to tonalitic source. The protolith for the Bear Ears pluton must have been subjected to high-grade metamorphism that caused loss of Rb and U prior to magma generation. -L.C.H.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.146..164S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.146..164S"><span id="translatedtitle">Kinetic and metabolic <span class="hlt">isotope</span> effects in coral skeletal carbon <span class="hlt">isotopes</span>: A re-evaluation using experimental coral bleaching as a case <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schoepf, Verena; Levas, Stephen J.; Rodrigues, Lisa J.; McBride, Michael O.; Aschaffenburg, Matthew D.; Matsui, Yohei; Warner, Mark E.; Hughes, Adam D.; Grottoli, Andréa G.</p> <p>2014-12-01</p> <p>Coral skeletal δ13C can be a paleo-climate proxy for light levels (i.e., cloud cover and seasonality) and for photosynthesis to respiration (P/R) ratios. The usefulness of coral δ13C as a proxy depends on metabolic <span class="hlt">isotope</span> effects (related to changes in photosynthesis) being the dominant influence on skeletal δ13C. However, it is also influenced by kinetic <span class="hlt">isotope</span> effects (related to calcification rate) which can overpower metabolic <span class="hlt">isotope</span> effects and thus compromise the use of coral skeletal δ13C as a proxy. Heikoop et al. (2000) proposed a simple data correction to remove kinetic <span class="hlt">isotope</span> effects from coral skeletal δ13C, as well as an equation to calculate P/R ratios from coral <span class="hlt">isotopes</span>. However, despite having been used by other researchers, the data correction has never been directly tested, and <span class="hlt">isotope</span>-based P/R ratios have never been compared to P/R ratios measured using respirometry. Experimental coral bleaching represents a unique environmental scenario to test this because bleaching produces large physiological responses that influence both metabolic and kinetic <span class="hlt">isotope</span> effects in corals. Here, we tested the δ13C correction and the P/R calculation using three Pacific and three Caribbean coral species from controlled temperature-induced bleaching experiments where both the stable <span class="hlt">isotopes</span> and the physiological variables that cause <span class="hlt">isotopic</span> fractionation (i.e., photosynthesis, respiration, and calcification) were simultaneously measured. We show for the first time that the data correction proposed by Heikoop et al. (2000) does not effectively remove kinetic effects in the coral species <span class="hlt">studied</span> here, and did not improve the metabolic signal of bleached and non-bleached corals. In addition, <span class="hlt">isotope</span>-based P/R ratios were in poor agreement with measured P/R ratios, even when the data correction was applied. This suggests that additional factors influence δ13C and δ18O, which are not accounted for by the data correction. We therefore recommend that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870011105','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870011105"><span id="translatedtitle">Rare <span class="hlt">isotope</span> <span class="hlt">studies</span> involving catalytic oxidation of CO over platinum-tin oxide</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Upchurch, Billy T.; Wood, George M., Jr.; Hess, Robert V.; Hoyt, Ronald F.</p> <p>1987-01-01</p> <p>Results of <span class="hlt">studies</span> utilizing normal and rare oxygen <span class="hlt">isotopes</span> in the catalytic oxidation of carbon monoxide over a platinum-tin oxide catalyst substrate are presented. Chemisorption of labeled carbon monoxide on the catalyst followed by thermal desorption yielded a carbon dioxide product with an oxygen-18 composition consistent with the formation of a carbonate-like intermediate in the chemisorption process. The efficacy of a method developed for the oxygen-18 labeling of the platinum-tin oxide catalyst surface for use in closed cycle pulsed care <span class="hlt">isotope</span> carbon dioxide lasers is demonstrated for the equivalent of 10 to the 6th power pulses at 10 pulses per second.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22307878','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22307878"><span id="translatedtitle"><span class="hlt">Study</span> of asymmetric fission yield behavior from neutron-deficient Hg <span class="hlt">isotope</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Perkasa, Y. S.; Waris, A. Kurniadi, R. Su'ud, Z.</p> <p>2014-09-30</p> <p>A <span class="hlt">study</span> of asymmetric fission yield behavior from a neutron-deficient Hg <span class="hlt">isotope</span> has been conducted. The fission yield calculation of the neutron-deficient Hg <span class="hlt">isotope</span> using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21255453','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21255453"><span id="translatedtitle"><span class="hlt">Study</span> of shape transitions in N{approx}90 <span class="hlt">isotopes</span> with beyond mean field calculations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rodriguez, Tomas R.; Egido, J. L.</p> <p>2009-01-28</p> <p>We <span class="hlt">study</span> the spherical to prolate-deformed shape transition in {sup 144-158}Sm and {sup 146-160}Gd <span class="hlt">isotopes</span> with modern calculations beyond the mean field with the Gogny D1S force. We compare the results with the shape-phase transition predicted by the collective Hamiltonian model and with the experimental data. Our calculations do not support the existence of a first order phase transition in these <span class="hlt">isotopic</span> chains in the viewpoint of the Bohr Hamiltonian neither the interpretation of the nuclei N = 90 as critical points.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040088750&hterms=kr&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dkr','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040088750&hterms=kr&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dkr"><span id="translatedtitle">An experimental <span class="hlt">study</span> of the <span class="hlt">isotopic</span> enrichment in Ar, Kr, and Xe when trapped in water ice</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Notesco, G.; Laufer, D.; Bar-Nun, A.; Owen, T.</p> <p>1999-01-01</p> <p>The <span class="hlt">isotopic</span> enrichment of argon, krypton, and xenon, when trapped in water ice, was <span class="hlt">studied</span> experimentally. The <span class="hlt">isotopes</span> were found to be enriched according to their (m1/m2)1/2 ratio. These enrichment factors could be useful for comparison among the uncertain cosmic or solar <span class="hlt">isotopic</span> ratios, the hopeful in situ cometary ratio, and those in Earth's atmosphere, in the context of cometary delivery of volatiles to Earth.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3483624','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3483624"><span id="translatedtitle">The diet-body offset in human nitrogen <span class="hlt">isotopic</span> values: A controlled dietary <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>O'Connell, TC; Kneale, CJ; Tasevska, N; Kuhnle, GGC</p> <p>2012-01-01</p> <p>Abstract The "trophic level enrichment" between diet and body results in an overall increase in nitrogen <span class="hlt">isotopic</span> values as the food chain is ascended. Quantifying the diet–body Δ15N spacing has proved difficult, particularly for humans. The value is usually assumed to be +3–5‰ in the archaeological literature. We report here the first (to our knowledge) data from humans on <span class="hlt">isotopically</span> known diets, comparing dietary intake and a body tissue sample, that of red blood cells. Samples were taken from 11 subjects on controlled diets for a 30-day period, where the controlled diets were designed to match each individual's habitual diet, thus reducing problems with short-term changes in diet causing <span class="hlt">isotopic</span> changes in the body pool. The Δ15Ndiet-RBC was measured as +3.5‰. Using measured offsets from other <span class="hlt">studies</span>, we estimate the human Δ15Ndiet-keratin as +5.0–5.3‰, which is in good agreement with values derived from the two other <span class="hlt">studies</span> using individual diet records. We also estimate a value for Δ15Ndiet-collagen of ≍6‰, again in combination with measured offsets from other <span class="hlt">studies</span>. This value is larger than usually assumed in palaeodietary <span class="hlt">studies</span>, which suggests that the proportion of animal protein in prehistoric human diet may have often been overestimated in <span class="hlt">isotopic</span> <span class="hlt">studies</span> of palaeodiet. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc. PMID:23042579</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......518S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......518S"><span id="translatedtitle">A Mass Spectrometry <span class="hlt">Study</span> of <span class="hlt">Isotope</span> Separation in the Laser Plume</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suen, Timothy Wu</p> <p></p> <p>Accurate quantification of <span class="hlt">isotope</span> ratios is critical for both preventing the development of illicit weapons programs in nuclear safeguards and identifying the source of smuggled material in nuclear forensics. While <span class="hlt">isotope</span> analysis has traditionally been performed by mass spectrometry, the need for in situ measurements has prompted the development of optical techniques, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation molecular <span class="hlt">isotopic</span> spectrometry (LAMIS). These optical measurements rely on laser ablation for direct solid sampling, but several past <span class="hlt">studies</span> have suggested that the distribution of <span class="hlt">isotopes</span> in the ablation plume is not uniform. This <span class="hlt">study</span> seeks to characterize <span class="hlt">isotope</span> separation in the laser plume through the use of orthogonal-acceleration time-of-flight mass spectrometry. A silver foil was ablated with a Nd:YAG at 355 nm at an energy of 50 muJ with a spot size of 71 mum, for a fluence of 1.3 J/cm2 and an irradiance of 250 MW/cm2. Flat-plate repellers were used to sample the plume, and a temporal profile of the ions was obtained by varying the time delay on the high-voltage pulse. A spatial profile along the axis of the plume was generated by changing the position of the sample, which yielded snapshots of the <span class="hlt">isotopic</span> composition with time. In addition, the reflectron time-of-flight system was used as an energy filter in conjunction with the repellers to sample slices of the laser plasma orthogonal to the plume axis. Mass spectrometry of the plume revealed a fast ion distribution and a slow ion distribution. Measurements taken across the entire plume showed the fast 109Ag ions slightly ahead in both space and time, causing the 107Ag fraction to drop to 0.34 at 3 mus, 4 mm from the sample surface. Although measurements centered on the near side of the plume did not show <span class="hlt">isotope</span> separation, the slow ions on the far side of the plume included much more 109Ag than 107Ag. In addition to examining the <span class="hlt">isotope</span> content of the ablation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6753337','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6753337"><span id="translatedtitle">Laser-microprobe <span class="hlt">studies</span> of rare gas <span class="hlt">isotopes</span> in meteorites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kirschbaum, C.L.</p> <p>1986-01-01</p> <p>A new rare gas mass spectrometer of high sensitivity coupled to a laser microprobe extraction system (constructed by the author) is described. The laser microprobe is applied to a long standing problem in cosmochemistry - determining the minerals which carry /sup 129/Xe from the decay of the extinct radioactive <span class="hlt">isotope</span> /sup 129/I (this /sup 129/Xe is referred to as /sup 129/Xe/sub r/). The /sup 129/Xe/sub r//sup 127/I ratios and the inferred relative formation times of these minerals are also determined. In the Allende meteorite, sodalite (Na/sub 8/(Al/sub 6/Si/sub 6/O/sub 24/)Cl/sub 2/) has been verified to be the major carrier for /sup 129/Xe/sub r/ in fine-grained inclusions. Although the exact mineral phase responsible has not been identified a carrier other than sodalite is also present in matrix from Allende. The /sup 129/Xe/sub r/ of this carrier is physically correlated with trapped xenon in the matrix and has a chlorine/iodine ratio which is lower than the ratio in the fine-grained inclusions. The /sup 129/Xe/sub r///sup 127/I ratios for sodalite from the fine-grained inclusions, and matrix are similar - between 1.25 and 1.35 x 10/sup -4/. This implies an age for these samples within 2 million years of the Bjurbole meteorite (Bjurbole is commonly used as a standard for meteorite formation intervals). The /sup 129/Xe/sub r///sup 127/I ratio of the sample of the fine-grained inclusion in which sodalite was thermally decomposed by laboratory preheating, is 2.4 x 10/sup -4/ or 16 million years before Bjurbole. The alteration-product-free coarse-grained inclusion on the other hand showed a ratio of 3.15 x 10/sup -5/ or 35 million years after Bjurbole. These relative formation intervals are much longer than expected for nebular processes and hence are either due to parent body processes or heterogeneity of the /sup 129/I//sup 127/I ratio in the early solar system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Litho.202..363W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Litho.202..363W"><span id="translatedtitle">Geochemical and <span class="hlt">isotopic</span> composition of Pan-African metabasalts from southwestern Gondwana: Evidence of Cretaceous South Atlantic opening along a Neoproterozoic back-arc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Will, Thomas M.; Frimmel, Hartwig E.; Gaucher, Claudio; Bossi, Jorge</p> <p>2014-08-01</p> <p>A lithogeochemical and <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotope</span> <span class="hlt">study</span> of former oceanic crustal rocks from the Cuchilla Dionisio Terrane in the southern Dom Feliciano Belt, Uruguay (La Tuna amphibolites) and metabasites in the Chameis Subterrane of the Marmora Terrane in the Gariep Belt, Namibia/South Africa shows that these rocks are compositionally very similar and probably represent the same unit on opposite sides of the modern South Atlantic. The mafic rocks from both terranes are tholeiitic metabasalts and -andesites and have depleted rare earth element patterns, generally low TiO2 (< 1.5 wt.%), very low Th/Nb ratios and lack negative Nb-Ta anomalies, all features that are typical of ‘normal' mid-ocean ridge basalts (N-MORB) and/or back-arc basin basalts (BABB). In addition, both rock suites have extremely depleted Nd <span class="hlt">isotope</span> compositions (εNd630 Ma = 6.7-9.4), superchondritic 147Sm/144Nd ratios, and low 206Pb/204Pb and 207Pb/204Pb initial ratios. The 87Sr/86Sr initial ratios of the La Tuna mafic rocks are low, whereas the Chameis metagabbro samples have higher, possibly alteration-related ratios. The geochemical and <span class="hlt">isotopic</span> signatures are consistent with the formation of both rock suites in the same mature Neoproterozoic back-arc basin (Marmora Basin), supporting conclusions drawn from earlier provenance <span class="hlt">studies</span> of metasedimentary units from these terranes. Other mafic rocks from the Marmora Terrane are interpreted as ocean island basalts that formed in a within-plate setting. A corollary of the conclusion that the mafic rocks in the Cuchilla Dionisio and Marmora Terranes formed in the same back-arc basin is (1) that the main Pan-African suture between the Río de la Plata Craton and the Kalahari Craton lies to the west of the Dom Feliciano Belt in South America, and (2) that the opening of the modern South Atlantic did not occur along that suture but along the axis of the Neoproterozoic Marmora back-arc basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Geomo.259..134C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Geomo.259..134C"><span id="translatedtitle">Implications for post-comminution processes in subglacial suspended sediment using coupled radiogenic strontium and neodymium <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clinger, Anna E.; Aciego, Sarah M.; Stevenson, Emily I.; Arendt, Carli A.; Robbins, Mark J.</p> <p>2016-04-01</p> <p> the subglacial till beneath the AG, our <span class="hlt">study</span> supports the use of <span class="hlt">Sr-Nd</span> as a new proxy in the subglacial environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.6257B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.6257B"><span id="translatedtitle">Evaporation from the shallow Lake Massaciuccoli (Tuscany, Italy) <span class="hlt">studied</span> using stable <span class="hlt">isotopes</span> and evaporation pan data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baneschi, I.; Gonfiantini, R.; Guidi, M.</p> <p>2009-04-01</p> <p>Oxygen and hydrogen <span class="hlt">isotope</span> variations monitored in Lake Massaciuccoli (7 km2, 2 m deep, seasonally variable water level) during summer 2008, were compared with those observed in a Class A evaporation pan (diameter 120.6 cm, depth 25.4 cm) placed on the lake eastern shore. Air temperature, pressure, relative humidity, wind speed and direction, solar radiation, water temperature in the lake and the pan were also measured. The pluviometer indicated that no precipitation occurred during the <span class="hlt">study</span> period. The pan was initially filled with groundwater up to the level of 19.2 cm (219 L), depleted in heavy <span class="hlt">isotopes</span> with respect to tha lake water. Sodium chloride was added up to the concentration of 1 g×L-1, which is assumed do not affect significantly the evaporation rate till the water volume is reduced to less than 10 %. The Cl- concentration was used to provide an estimation of the evaporated water fraction, in addition to the micrometer measuring the water level variations. The pan water was sampled every 2-3 days and Cl- and stable <span class="hlt">isotopes</span> determined. The set of stable <span class="hlt">isotope</span> and evaporation data enabled us to compute the parameters governing the evaporation process and the <span class="hlt">isotopic</span> exchanges with the atmospheric moisture, according to the procedure proposed by Gonfiantini (1986). The values were applied to test three working hypotheses of water balance of Lake Massaciuccoli: (i) surface inflow and outflow of liquid water are negligible and only evaporation is important; (ii) the inflow is negligible and outflow and evaporation are both significant; (iii) the three terms of balance are all important but the losses by evaporation and outflow exceed inflow (as the lake water level was decreasing). Water exchanges with groundwater are considered negligible. The best agreement between lake and pan data was obtained with the second hypothesis, for which the fraction of water removed by evaporation was estimated to be about 40 % ot he total water losses. This residual</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5821306','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5821306"><span id="translatedtitle">Electron transfer within xanthine oxidase: A solvent kinetic <span class="hlt">isotope</span> effect <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hille, R. )</p> <p>1991-09-03</p> <p>Solvent kinetic <span class="hlt">isotope</span> effect <span class="hlt">studies</span> of electron transfer within xanthine oxidase have been performed, using a stopped-flow pH-jump technique to perturb the distribution of reducing equivalents within partially reduced enzyme and follow the kinetics of reequilibration spectrophotometrically. It is found that the rate constant for electron transfer between the flavin and one of the iron-sulfur centers of the enzyme observed when the pH is jumped from 10 to 6 decreases from 173 to 25 s{sup {minus}1} on going from HJ{sub 2}O to D{sub 2}O, giving an observed solvent kinetic <span class="hlt">isotope</span> effect of 6.9. An effect of comparable magnitude is observed for the pH jump in the opposite direction, the rate constant decreasing form 395 to 56 s{sup {minus}1}. The solvent kinetic <span class="hlt">isotope</span> effect on k{sub obs} is found to be directly proportional to the mole fraction of D{sub 2}O in the reaction mix for the pH jump in each direction, consistent with the effect arising from a single exchangeable proton. Calculations of the microscopic rate constants for electron transfer between the flavin and the iron-sulfur center indicate that the intrinsic solvent kinetic <span class="hlt">isotope</span> effect for electron transfer from the neutral flavin semiquinone to the iron-sulfur center designated Fe/S I is substantially greater than for electron transfer in the opposite direction and that the observed solvent kinetic <span class="hlt">isotope</span> effect is a weighted average of the intrinsic <span class="hlt">isotope</span> effects for the forward and reverse microscopic electron-transfer steps. The results emphasize the importance of prototropic equilibria in the kinetic as well as thermodynamic behavior of xanthine oxidase and indicate that protonation/deprotonation of the isoalloxazine ring is concomitant with electron transfer in the xanthine oxidase system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25817456','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25817456"><span id="translatedtitle">Carbon stable-<span class="hlt">isotope</span> tracking in breath for comparative <span class="hlt">studies</span> of fuel use.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Welch, Kenneth C; Péronnet, François; Hatch, Kent A; Voigt, Christian C; McCue, Marshall D</p> <p>2016-02-01</p> <p>Almost half a century ago, researchers demonstrated that the ratio of stable carbon <span class="hlt">isotopes</span> in exhaled breath of rats and humans could reveal the oxidation of labeled substrates in vivo, opening a new chapter in the <span class="hlt">study</span> of fuel use, the fate of ingested substrates, and aerobic metabolism. Until recently, the combined use of respirometry and stable-<span class="hlt">isotope</span> tracer techniques had not been broadly employed to <span class="hlt">study</span> fuel use in other animal groups. In this review, we summarize the history of this approach in human and animal research and define best practices that maximize its utility. We also summarize several case <span class="hlt">studies</span> that use stable-<span class="hlt">isotope</span> measurements of breath to explore the limits of aerobic metabolism and substrate turnover among several species and various physiological states. We highlight the importance of a comparative approach in revealing the profound effects that phylogeny, ecology, and behavior can have in shaping aerobic metabolism and energetics as well as the fundamental biological principles that underlie fuel use and metabolic function across taxa. New analytical equipment and refinement of methodology make the combined use of respirometry and stable-<span class="hlt">isotope</span> tracer techniques simpler to perform, less costly, and more field ready than ever before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1130229','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1130229"><span id="translatedtitle">Automated data extraction from in situ protein stable <span class="hlt">isotope</span> probing <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Slysz, Gordon W.; Steinke, Laurey A.; Ward, David M.; Klatt, Christian G.; Clauss, Therese RW; Purvine, Samuel O.; Payne, Samuel H.; Anderson, Gordon A.; Smith, Richard D.; Lipton, Mary S.</p> <p>2014-01-27</p> <p>Protein stable <span class="hlt">isotope</span> probing (protein-SIP) has strong potential for revealing key metabolizing taxa in complex microbial communities. While most protein-SIP work to date has been performed under controlled laboratory conditions to allow extensive <span class="hlt">isotope</span> labeling of the target organism, a key application will be in situ <span class="hlt">studies</span> of microbial communities under conditions that result in small degrees of partial labeling. One hurdle restricting large scale in situ protein-SIP <span class="hlt">studies</span> is the lack of algorithms and software for automated data processing of the massive data sets resulting from such <span class="hlt">studies</span>. In response, we developed Stable <span class="hlt">Isotope</span> Probing Protein Extraction Resources software (SIPPER) and applied it for large scale extraction and visualization of data from short term (3 h) protein-SIP experiments performed in situ on Yellowstone phototrophic bacterial mats. Several metrics incorporated into the software allow it to support exhaustive analysis of the complex composite <span class="hlt">isotopic</span> envelope observed as a result of low amounts of partial label incorporation. SIPPER also enables the detection of labeled molecular species without the need for any prior identification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1210254B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1210254B"><span id="translatedtitle">Online analysis of chlorine stable <span class="hlt">isotopes</span> in chlorinated ethylenes: an inter-laboratory <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bernstein, Anat; Shouakar-Stash, Orfan; Hunkeler, Daniel; Sakaguchi-Söder, Kaori; Laskov, Christine; Aravena, Ramon; Elsner, Martin</p> <p>2010-05-01</p> <p>In the last decade, compound-specific stable <span class="hlt">isotopes</span> analysis of groundwater pollutants became an important tool to identify different sources of the same pollutant and for tracking natural attenuating processes in the sub-surface. It has been shown that trends in the <span class="hlt">isotopic</span> composition of the target compounds can shed light on in-situ processes that are otherwise difficult to track. Analytical methods of carbon, nitrogen and hydrogen were established and are by now frequently used for a variety of organic pollutants. Yet, the motivation of introducing analytical methods for new <span class="hlt">isotopes</span> is emerging. This motivation is further enhanced, as advantages of using two or more stable <span class="hlt">isotopes</span> for gaining better insight on degradation pathways are well accepted. One important element which demands the development of appropriate analytical methods is chlorine, which is found in various groups of organic pollutants, among them the chlorinated ethylenes. Chlorinated ethylenes are considered as high priority environmental pollutants, and the development of suitable chlorine <span class="hlt">isotope</span> methods for this group of pollutants is highly desired. Ideally, stable <span class="hlt">isotope</span> techniques should have the capability to determine the <span class="hlt">isotopic</span> composition of and individual target compound in a non-pure mixture, without the requirement of a laborious off-line treatment. Indeed, in the last years two different concepts for on-line chlorine <span class="hlt">isotope</span> analysis methods were introduced, by using either a standard quadrapole GC/MS (Sakaguchi-Söder et al., 2007) or by using a GC/IRMS (Shouakar-Stash et al., 2006). We present a comparison of the performances of two concepts, carried out in five different laboratories: Waterloo (GC/IRMS), Neuchâtel (GC/MS), Darmstadt (GC/MS), Tübingen (GC/MS) and Munich (GC/IRMS). This comparison was performed on pure trichloroethylene and dichloroethylene products of different manufactures, as well as trichloroethylene and dichloroethylene samples that were exposed to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.V51B0548I&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.V51B0548I&link_type=ABSTRACT"><span id="translatedtitle">A Combined He and Os <span class="hlt">Isotopic</span> <span class="hlt">Study</span> of the HSDP-2 Core from Mauna Kea, Hawaii</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ireland, T. J.; Walker, R. J.; Depaolo, D. J.; Kurz, M. D.</p> <p>2004-12-01</p> <p>Combined osmium and helium <span class="hlt">isotope</span> systematics of hotspot lavas have the potential to reveal information about the deep Earth. A high 3He/4He ratio may represent an undegassed reservoir, generally associated with the lower mantle. There are two Os <span class="hlt">isotopes</span> that can be <span class="hlt">studied</span> to help to further elucidate the problem. The decay of 187Re to 187Os is the more frequently cited system; however, in terms of lower mantle processes, the decay of 190Pt to 186Os may be extremely useful. Both of these Os <span class="hlt">isotopes</span> are enriched in the core relative to chondritic values. In a previous <span class="hlt">study</span>, Brandon et al. (1999) examined several Hawaiian volcanoes for both He and Os <span class="hlt">isotopes</span>. A correlation was noted between the 3He/4He, 187Os/188Os and 186Os/188Os ratios. In terms of 3He/4He and 187Os/188Os space, the three commonly cited Hawaiian end-members (Kea, Koolau and Loihi members) were clearly defined. A strong positive correlation was also observed for 186Os/188Os versus 3He/4He. These correlations were interpreted as a possible signature of core-mantle interaction. There were some limitations to previous <span class="hlt">studies</span>. Only 2-3 samples from each volcano were <span class="hlt">studied</span>, with these samples generally being subaerially erupted. The He data utilized were often not for the same samples for which the Os data were collected (volcano averages for He were used on some samples). With the introduction of data from the Hawaiian Scientific Drilling Project (HSDP-2), which drilled 2.84 km into the Mauna Kea volcanics (DePaolo et al., 2000), an extensive history of a single volcano can be observed (from the early submarine stages to the later subaerial rocks). In the current <span class="hlt">study</span> a detailed Os <span class="hlt">isotopic</span> analysis of several samples that span a large depth range of the HSDP-2 core, in conjunction with previously collected He <span class="hlt">isotopic</span> data (Kurz et al., 2004), was conducted. The samples define a relatively narrow range of slightly suprachondritic 187Os/188Os ratios (0.12865-0.13056), despite having a large</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.V31C2162O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.V31C2162O"><span id="translatedtitle">Magmatism in the Tsagaandelger, Eastern Mongolian volcanic belt: Petrological, geochemical and <span class="hlt">isotopic</span> constraints on Mesozoic geodynamic setting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oidov, M.; Fujimaki, H.</p> <p>2008-12-01</p> <p>The vast territory of Mongolia lies in the heart of the Central Asian Orogenic Belt, one of largest provinces of the Phanerozoic continental growth on Earth (Jahn et al., 2004). We present new petrographic, geochemical and <span class="hlt">Sr-Nd</span> <span class="hlt">isotopic</span> analyses on Mesozoic igneous rocks emplaced in Central Mongolia. The Mesozoic igneous suites, those exposed in the Tsagaandelger area, pass upwards from alkaline series trachytic rocks and overlain by tuffaceous sediments. Those are intruded by calc alkaline leucocratic granites and covered by Late Mesozoic calc alkaline bimodal volcanic rocks consisting of basalts and rhyolite. Alkaline series volcanic sequences were erupted in Early-Middle Triassic (241 Ma) and characterized by LILE, LREE enrichment and significant Nb-Ta depletion. Rocks have weakly enriched initial 87Sr86Sr ratios of 0.705 to 0.706 and positive ɛNd(t) values (0.7 to 4). The crystallization age of intrusive rocks is 231 Ma. The majority of samples is slightly peraluminous and can be classified as granite, including monzogranite, granodiorite and aplite. Granites are characterized by near- zero ɛNd(t) values (0.7 to 2) and tetrad effect in their REE distribution patterns. Further Cretaceous volcanic sequences have lower contents of LILE and higher contents of HFS and REE, comparing with Triassic volcanic sequences. The Cretaceous volcanic rocks have the initial 87Sr86Sr ratios between 0.705 and 0.719 and near-zero ɛNd(t) values (-0.7 to 1.6). Trace element geochemistry indicates that Mesozoic volcanic rocks from the <span class="hlt">studied</span> area are arc related. The Triassic volcanic and plutonic rocks could be emplaced in active continental margin settings. Post collisional extensional regime could be started with Early Cretaceous volcanism. The mass balance calculation suggests that the all Mesozoic volcanic and plutonic rocks were derived from sources composed of more than 80% juvenile mantle-derived component. Our data confirm the earlier observations of similar <span class="hlt">isotopic</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70012465','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70012465"><span id="translatedtitle">Preliminary <span class="hlt">isotopic</span> <span class="hlt">studies</span> of fluids from the Cerro Prieto geothermal field</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Truesdell, A.H.; Rye, R.O.; Pearson, F.J.; Olson, E.R.; Nehring, N.L.; Whelan, J.F.; Huebner, M.A.; Coplen, T.B.</p> <p>1979-01-01</p> <p>Preliminary <span class="hlt">isotopic</span> <span class="hlt">studies</span> of Cerro Prieto geothermal fluids and earlier <span class="hlt">studies</span> of Mexicali Valley ground waters suggest local recharge of the geothermal system from the area immediately to the west. Oxygen <span class="hlt">isotope</span> exchange of water with reservoir rock minerals at temperatures increasing with depth has produced fluids with oxygen-18 contents increasing with depth, and pressure drawdown in the southeastern part of the field has allowed lower oxygen-18 fluids to invade the production aquifer from above. The contents of tritium and carbon-14 in the fluid suggest only that the age of the fluid is between 50 and 10,000 years. The <span class="hlt">isotopic</span> compositions of carbon and sulfur are consistent with a magmatic origin of these elements but a mixed sedimentary-organic origin appears more likely for carbon and is also possible for sulfur. Investigations of the <span class="hlt">isotopic</span> compositions of geothermal and cold ground waters continue and are being expanded as fluids become available and as separation and analysis methods are improved. ?? 1979.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5537026','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5537026"><span id="translatedtitle">Pb, Sr, and Nd <span class="hlt">isotopes</span> in basalts and sulfides from the Juan de Fuca Ridge</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hegner, E.; Tatsumoto, M.</p> <p>1987-10-10</p> <p>Pb, <span class="hlt">Sr</span>, <span class="hlt">Nd</span> <span class="hlt">isotopes</span> of seven basalt glasses collected by the submersible Alvin from the southern Juan de Fuca Ridge (SJFR) are almost identical (/sup 206/Pb//sup 204/Pbapprox.18.45, /sup 207/Pb//sup 204/Pbapprox.15.47, /sup 208/Pb//sup 204/Pbapprox.37.81, /sup 87/Sr//sup 86/Srapprox.0.70249, /sup 143/Nd//sup 144/Ndapprox.0.51315). Whereas all basalts appear cogenetic, four of the samples have uniform abundances of U, Th, Rb, Nd, Sm, Pb, and Sr, indicating that they are also comagmatic. Two basalt glasses dredged previously at the SJFR have similar <span class="hlt">isotopic</span> compositions but higher concentrations of U, Th, and Pb. The /sup 206/Pb//sup 204/Pb ratios are intermediate between generally less radiogenic ridge basalts from south of the Juan de Fuca Ridge (JFR) and often more radiogenic basalts from the northern JFR and NE Pacific seamounts. Sr and Nd <span class="hlt">isotopic</span> compositions closely resemble data of other ridge basalts from the northernmost East Pacific Rise and are intermediate between <span class="hlt">isotopically</span> more diverse seamount basalts produced nearby.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27251153','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27251153"><span id="translatedtitle">Neonatal Respiratory Diseases in the Newborn Infant: Novel Insights from Stable <span class="hlt">Isotope</span> Tracer <span class="hlt">Studies</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carnielli, Virgilio P; Giorgetti, Chiara; Simonato, Manuela; Vedovelli, Luca; Cogo, Paola</p> <p>2016-01-01</p> <p>Respiratory distress syndrome is a common problem in preterm infants and the etiology is multifactorial. Lung underdevelopment, lung hypoplasia, abnormal lung water metabolism, inflammation, and pulmonary surfactant deficiency or disfunction play a variable role in the pathogenesis of respiratory distress syndrome. High-quality exogenous surfactant replacement <span class="hlt">studies</span> and <span class="hlt">studies</span> on surfactant metabolism are available; however, the contribution of surfactant deficiency, alteration or dysfunction in selected neonatal lung conditions is not fully understood. In this article, we describe a series of <span class="hlt">studies</span> made by applying stable <span class="hlt">isotope</span> tracers to the <span class="hlt">study</span> of surfactant metabolism and lung water. In a first set of <span class="hlt">studies</span>, which we call 'endogenous <span class="hlt">studies</span>', using stable <span class="hlt">isotope</span>-labelled intravenous surfactant precursors, we showed the feasibility of measuring surfactant synthesis and kinetics in infants using several metabolic precursors including plasma glucose, plasma fatty acids and body water. In a second set of <span class="hlt">studies</span>, named 'exogenous <span class="hlt">studies</span>', using stable <span class="hlt">isotope</span>-labelled phosphatidylcholine tracer given endotracheally, we could estimate surfactant disaturated phosphatidylcholine pool size and half-life. Very recent <span class="hlt">studies</span> are focusing on lung water and on the endogenous biosynthesis of the surfactant-specific proteins. Information obtained from these <span class="hlt">studies</span> in infants will help to better tailor exogenous surfactant treatment in neonatal lung diseases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27251153','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27251153"><span id="translatedtitle">Neonatal Respiratory Diseases in the Newborn Infant: Novel Insights from Stable <span class="hlt">Isotope</span> Tracer <span class="hlt">Studies</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carnielli, Virgilio P; Giorgetti, Chiara; Simonato, Manuela; Vedovelli, Luca; Cogo, Paola</p> <p>2016-01-01</p> <p>Respiratory distress syndrome is a common problem in preterm infants and the etiology is multifactorial. Lung underdevelopment, lung hypoplasia, abnormal lung water metabolism, inflammation, and pulmonary surfactant deficiency or disfunction play a variable role in the pathogenesis of respiratory distress syndrome. High-quality exogenous surfactant replacement <span class="hlt">studies</span> and <span class="hlt">studies</span> on surfactant metabolism are available; however, the contribution of surfactant deficiency, alteration or dysfunction in selected neonatal lung conditions is not fully understood. In this article, we describe a series of <span class="hlt">studies</span> made by applying stable <span class="hlt">isotope</span> tracers to the <span class="hlt">study</span> of surfactant metabolism and lung water. In a first set of <span class="hlt">studies</span>, which we call 'endogenous <span class="hlt">studies</span>', using stable <span class="hlt">isotope</span>-labelled intravenous surfactant precursors, we showed the feasibility of measuring surfactant synthesis and kinetics in infants using several metabolic precursors including plasma glucose, plasma fatty acids and body water. In a second set of <span class="hlt">studies</span>, named 'exogenous <span class="hlt">studies</span>', using stable <span class="hlt">isotope</span>-labelled phosphatidylcholine tracer given endotracheally, we could estimate surfactant disaturated phosphatidylcholine pool size and half-life. Very recent <span class="hlt">studies</span> are focusing on lung water and on the endogenous biosynthesis of the surfactant-specific proteins. Information obtained from these <span class="hlt">studies</span> in infants will help to better tailor exogenous surfactant treatment in neonatal lung diseases. PMID:27251153</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.B22B..05D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.B22B..05D"><span id="translatedtitle">Oxygen and sulfur <span class="hlt">isotope</span> fractionation during methane dependent sulfate reduction in high pressure continuous incubation <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deusner, C.; Brunner, B.; Holler, T.; Widdel, F.; Ferdelman, T. G.</p> <p>2009-12-01</p> <p>The anaerobic oxidation of methane (AOM) coupled to sulfate reduction in marine sediments is an important sink in the global methane budget. However, many aspects of methane dependent sulfate reduction are not fully understood. We developed a novel high pressure biotechnical system to simulate marine conditions with high concentrations of dissolved gases, e.g. at gas seeps and gas hydrate systems. The system allows for batch, fed-batch and continuous gas-phase free incubation. We employ this system to <span class="hlt">study</span> the kinetics and <span class="hlt">isotope</span> fractionation during AOM at varying methane partial pressures up to 10 MPa. We present the results of long-term continuous and fed-batch incubations with highly active naturally enriched biomass from microbial mats from the Black Sea. During these experiments the methane partial pressure was increased stepwise from 0.1 to 10 MPa. The methane dependent sulfate reduction rate increased from 0.1 mmol/l/d to 3.5 mmol/l/d resulting from the increase in methane concentration and microbial growth. Sulfate reduction was negligible in the absence of methane. The sulfur and oxygen <span class="hlt">isotope</span> fractionation during sulfate reduction was strongly influenced by the concentration of dissolved methane. Sulfur <span class="hlt">isotope</span> fractionation was highest at low methane concentrations, and lowest at high methane concentrations. Relative to sulfate reduction rates, oxygen <span class="hlt">isotope</span> exchange between sulfate and water was highest at low methane concentrations, and lowest at high methane concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B34C..06J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B34C..06J"><span id="translatedtitle">Trees growing through impervious surfaces use shallower water sources: a stable <span class="hlt">isotope</span> <span class="hlt">study</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeong, J.; Ryu, Y.; Lee, D.</p> <p>2015-12-01</p> <p>Trees growing through impervious surfaces can give an impact on hydrological cycle in urban areas by increasing ground permeability. Even though depth and distribution of the root can substantially alter the hydrological cycle, only a few <span class="hlt">studies</span> have dealt with rooting depth and water use of trees growing through impervious surfaces. We compared the water sources of trees growing through impervious and pervious surfaces using a non-destructive stable <span class="hlt">isotope</span> approach. We measured oxygen and hydrogen <span class="hlt">isotopic</span> compositions from stem water and other potential water sources before and during the wet season. Oxygen and hydrogen <span class="hlt">isotopic</span> compositions of stem water were measured, indicating that trees growing through the impervious surfaces used <span class="hlt">isotopically</span> enriched water in both periods. An IsoSource model applied in the wet season showed that trees growing through impervious surfaces took most of their water from depths of around 20 cm, while the control trees took the greatest portion from a depth of 100 cm. Our results imply that urban trees growing through impervious surfaces might be vulnerable to drought and show the distinctive effect of urban plants on the redistribution of hydrological components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034201','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034201"><span id="translatedtitle">Geochemical and <span class="hlt">isotopic</span> <span class="hlt">study</span> of soils and waters from an Italian contaminated site: Agro Aversano (Campania)</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bove, M.A.; Ayuso, R.A.; de Vivo, B.; Lima, A.; Albanese, S.</p> <p>2011-01-01</p> <p>Lead <span class="hlt">isotope</span> applications have been widely used in recent years in environmental <span class="hlt">studies</span> conducted on different kinds of sampled media. In the present paper, Pb <span class="hlt">isotope</span> ratios have been used to determine the sources of metal pollution in soils and waters in the Agro Aversano area. During three different sampling phases, a total of 113 surface soils (5-20. cm), 20 samples from 2 soil profiles (0-1. m), 11 stream waters and 4 groundwaters were collected. Major element concentrations in sampled media have been analyzed by the ICP-MS technique. Surface soils (20 samples), all soil profiles and all waters have been also analyzed for Pb <span class="hlt">isotope</span> compositions by thermal ionization (TIMS). The geochemical data were assessed using statistic methods and cartographically elaborated in order to have a clear picture of the level of disturbance of the area. Pb <span class="hlt">isotopic</span> data were <span class="hlt">studied</span> to discriminate between anthropogenic and geologic sources. Our results show that As (5.6-25.6. mg/kg), Cu (9-677. mg/kg), Pb (22-193. mg/kg), Tl (0.53-3.62. mg/kg), V (26-142. mg/kg) and Zn (34-215. mg//kg) contents in analyzed soils, exceed the intervention limits fixed by the Italian Environmental Law for residential areas in some of the sampled sites, while intervention limit for industrial areas is exceeded only for Cu concentrations. Lead <span class="hlt">isotopic</span> data, show that there is a high similarity between the ratios measured in the leached soil samples and those deriving from anthropic activities. This similarity with anthropogenic Pb is also evident in the ratios measured in both groundwater and stream water samples. ?? 2010 Elsevier B.V.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP31B1313M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP31B1313M"><span id="translatedtitle">Chemical extraction of Nd <span class="hlt">isotopes</span> from deep-sea sediments for Cenozoic and Cretaceous paleoceanographic <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, E. E.; Blair, S. W.; Kamenov, G. D.; Scher, H. D.; Bourbon, E.; Basak, C.; Newkirk, D.</p> <p>2009-12-01</p> <p>Nd <span class="hlt">isotopes</span> preserved in deep sea sediments are now a common proxy for reconstructing past ocean circulation patterns. While <span class="hlt">studies</span> on Holocene-Pleistocene time scales frequently use chemical extractions of Nd that target dispersed ferromanganese (Fe-Mn) coatings on the bulk sediment, <span class="hlt">studies</span> on longer, Cenozoic time scales are generally limited to data from fossil fish teeth and Fe-Mn crusts due to concerns about diagenetic alteration of oxides over longer time scales and potential contamination of the extracted Nd. Fish teeth and Fe-Mn crusts are robust archives for Nd <span class="hlt">isotopes</span> over these time scales; however, separation and preparation of the teeth is laborious, and not all deep sea samples contain sufficient teeth for analysis. In addition, Fe-Mn crusts accumulate very slowly, integrate the seawater <span class="hlt">isotopic</span> signal over an extended period of time, and are difficult to date. This <span class="hlt">study</span> evaluates the integrity of Nd <span class="hlt">isotopes</span> that were chemically-extracted from Cenozoic to Cretaceous Ocean Drilling Program sediments by comparing these results to data from contemporaneous fish teeth. Nd was extracted from the > 63μm fraction of deep sea sediments following carbonate removal using a 2 hour leach in 0.02M hydroxylamine hydrochloride (HH) solution. All 94 paired samples of chemically-extracted and fossil fish tooth Nd produced <span class="hlt">isotopic</span> values that agree within error. These samples include material from the Miocene to Eocene from sites in the north (Sites 647 and 982) and south Atlantic (Sites 689, 690 and 1090), as well as Cretaceous black shales from the tropical Atlantic (Sites 1258 and 1260). This detailed comparison illustrates that Nd extracted from bulk deep sea sediments, which is derived at least in part from dispersed Fe-Mn oxide coatings, represents a promising archive for Nd <span class="hlt">isotopes</span> on longer time scales. This archive is widely available through time and space and the extraction procedure is relatively simple and rapid. The observed correlation between</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24662114','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24662114"><span id="translatedtitle">Application of stable <span class="hlt">isotope</span> tracers in the <span class="hlt">study</span> of exercise metabolism in children: a primer.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mahon, Anthony D; Timmons, Brian W</p> <p>2014-02-01</p> <p>Exercise metabolism in children has traditionally been assessed using the respiratory exchange ratio (RER) to determine the contributions of fat and carbohydrate to the exercise energy demands. Although easily measured, RER measurements have limitations. Other methods to assess metabolism such as the obtainment of a muscle biopsy and the use of nuclear magnetic resonance spectroscopy carry ethical and feasibility concerns, respectively, which limit their use in <span class="hlt">studies</span> involving children. Stable <span class="hlt">isotopes</span>, used routinely in <span class="hlt">studies</span> involving adults, can also be applied in <span class="hlt">studies</span> involving children in an ethical and feasible manner. Two common stable <span class="hlt">isotopes</span> used in metabolic <span class="hlt">studies</span> involving children include carbon-13 (¹³C) and nitrogen-15 (¹⁵N). ¹³C-glucose can be used to <span class="hlt">study</span> carbohydrate metabolism and ¹⁵N-glycine can be used to assess protein metabolism. This article reviews the use of ¹³C-glucose and ¹⁵N-glycine to <span class="hlt">study</span> exercise metabolism in children, considers some of the associated ethical aspects, explains the general methodology involved in administering these <span class="hlt">isotopes</span> and the resources required, and describes <span class="hlt">studies</span> involving children utilizing these methods. Finally, suggestions for future research are provided to encourage further use of these techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003TrGeo...4..213J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003TrGeo...4..213J"><span id="translatedtitle">Water Stable <span class="hlt">Isotopes</span>: Atmospheric Composition and Applications in Polar Ice Core <span class="hlt">Studies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jouzel, J.</p> <p>2003-12-01</p> <p> large-scale properties. First, there is no clear relationship between δp and the temperature of the site in tropical and equatorial regions. There, δp is more significantly influenced by precipitation amount. Second (see Figure 2), δD and δ18O are linearly related to each other throughout the world with a slope of ˜8 and a deuterium excess (d=δD-8δ18O) of ˜10‰ (Craig, 1961; Dansgaard, 1964). Although there has been a lot of potential interest in characterizing modifications in precipitation patterns such as those linked with changes in moonsonal activity or in the El Niño Southern Oscillation, the first property has, up to now, only been exploited in a very limited number of <span class="hlt">studies</span>. In contrast, the fact that the deuterium excess of a precipitation is influenced by the conditions prevailing in the oceanic moisture source region (temperature, relative humidity, and, to a lesser degree, wind speed) is now widely used to reconstruct the changes in the temperature of the evaporative source, Tw. (6K)Figure 2. Annual δD in precipitation versus annual δ18O in precipitation (after Jouzel et al., 1987a). A large variety of <span class="hlt">isotope</span> paleodata is available. <span class="hlt">Isotope</span> signatures are measured directly in ice cores, groundwaters, and fluid inclusions in speleothems, and indirectly in precipitated calcite, tree ring cellulose, and other organic materials, particularly those in lake sediments. Polar ice cores are particularly suited for paleoclimate reconstructions. First, δp and Ts are strongly correlated in these regions, as illustrated in Figure 3 for Greenland and Antarctica. Second, they give direct access to the precipitation with little postdepositional change at least when the signal can be averaged over a certain number of years. Third, they provide continuous and potentially very detailed sequences with the longest record covering the last 420 ka (thousands of years) at the Vostok site in Antarctica (and possibly even older periods in the recently drilled EPICA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812383C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812383C"><span id="translatedtitle">Stable <span class="hlt">isotopes</span> and Digital Elevation Models to <span class="hlt">study</span> nutrient inputs in high-Arctic lakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calizza, Edoardo; Rossi, David; Costantini, Maria Letizia; Careddu, Giulio; Rossi, Loreto</p> <p>2016-04-01</p> <p>Ice cover, run-off from the watershed, aquatic and terrestrial primary productivity, guano deposition from birds are key factors controlling nutrient and organic matter inputs in high-Arctic lakes. All these factors are expected to be significantly affected by climate change. Quantifying these controls is a key baseline step to understand what combination of factors subtends the biological productivity in Arctic lakes and will drive their ecological response to environmental change. Basing on Digital Elevation Models, drainage maps, and C and N elemental content and stable <span class="hlt">isotope</span> analysis in sediments, aquatic vegetation and a dominant macroinvertebrate species (Lepidurus arcticus Pallas 1973) belonging to Tvillingvatnet, Storvatnet and Kolhamna, three lakes located in North Spitsbergen (Svalbard), we propose an integrated approach for the analysis of (i) nutrient and organic matter inputs in lakes; (ii) the role of catchment hydro-geomorphology in determining inter-lake differences in the <span class="hlt">isotopic</span> composition of sediments; (iii) effects of diverse nutrient inputs on the <span class="hlt">isotopic</span> niche of Lepidurus arcticus. Given its high run-off and large catchment, organic deposits in Tvillingvatnet where dominated by terrestrial inputs, whereas inputs were mainly of aquatic origin in Storvatnet, a lowland lake with low potential run-off. In Kolhamna, organic deposits seem to be dominated by inputs from birds, which actually colonise the area. <span class="hlt">Isotopic</span> signatures were similar between samples within each lake, representing precise tracers for <span class="hlt">studies</span> on the effect of climate change on biogeochemical cycles in lakes. The <span class="hlt">isotopic</span> niche of L. aricticus reflected differences in sediments between lakes, suggesting a bottom-up effect of hydro-geomorphology characterizing each lake on nutrients assimilated by this species. The presented approach proven to be an effective research pathway for the identification of factors subtending to nutrient and organic matter inputs and transfer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.188...73M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.188...73M"><span id="translatedtitle"><span class="hlt">Study</span> of thermochemical sulfate reduction mechanism using compound specific sulfur <span class="hlt">isotope</span> analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meshoulam, Alexander; Ellis, Geoffrey S.; Said Ahmad, Ward; Deev, Andrei; Sessions, Alex L.; Tang, Yongchun; Adkins, Jess F.; Liu, Jinzhong; Gilhooly, William P.; Aizenshtat, Zeev; Amrani, Alon</p> <p>2016-09-01</p> <p>The sulfur <span class="hlt">isotopic</span> fractionation associated with the formation of organic sulfur compounds (OSCs) during thermochemical sulfate reduction (TSR) was <span class="hlt">studied</span> using gold-tube pyrolysis experiments to simulate TSR. The reactants used included n-hexadecane (n-C16) as a model organic compound with sulfate, sulfite, or elemental sulfur as the sulfur source. At the end of each experiment, the S-<span class="hlt">isotopic</span> composition and concentration of remaining sulfate, H2S, benzothiophene, dibenzothiophene, and 2-phenylthiophene (PT) were measured. The observed S-<span class="hlt">isotopic</span> fractionations between sulfate and BT, DBT, and H2S in experimental simulations of TSR correlate well with a multi-stage model of the overall TSR process. Large kinetic <span class="hlt">isotope</span> fractionations occur during the first, uncatalyzed stage of TSR, 12.4‰ for H2S and as much as 22.2‰ for BT. The fractionations decrease as the H2S concentration increases and the reaction enters the second, catalyzed stage. Once all of the oxidizable hydrocarbons have been consumed, sulfate reduction ceases and equilibrium partitioning then dictates the fractionation between H2S and sulfate (∼17‰). Experiments involving sparingly soluble CaSO4 show that during the second catalytic phase of TSR the rate of sulfate reduction exceeds that of sulfate dissolution. In this case, there is no apparent <span class="hlt">isotopic</span> fractionation between source sulfate and generated H2S, as all of the available sulfate is effectively reduced at all reaction times. When CaSO4 is replaced with fully soluble Na2SO4, sulfate dissolution is no longer rate limiting and significant S-<span class="hlt">isotopic</span> fractionation is observed. This supports the notion that CaSO4 dissolution can lead to the apparent lack of fractionation between H2S and sulfate produced by TSR in nature. The S-<span class="hlt">isotopic</span> composition of individual OSCs record information related to geochemical reactions that cannot be discerned from the δ34S values obtained from bulk phases such as H2S, oil, and sulfate minerals, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16082561','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16082561"><span id="translatedtitle">Controlling for anthropogenically induced atmospheric variation in stable carbon <span class="hlt">isotope</span> <span class="hlt">studies</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Long, Eric S; Sweitzer, Richard A; Diefenbach, Duane R; Ben-David, Merav</p> <p>2005-11-01</p> <p>Increased use of stable <span class="hlt">isotope</span> analysis to examine food-web dynamics, migration, transfer of nutrients, and behavior will likely result in expansion of stable <span class="hlt">isotope</span> <span class="hlt">studies</span> investigating human-induced global changes. Recent elevation of atmospheric CO2 concentration, related primarily to fossil fuel combustion, has reduced atmospheric CO2 delta13C (13C/12C), and this change in <span class="hlt">isotopic</span> baseline has, in turn, reduced plant and animal tissue delta13C of terrestrial and aquatic organisms. Such depletion in CO2 delta13C and its effects on tissue delta13C may introduce bias into delta13C investigations, and if this variation is not controlled, may confound interpretation of results obtained from tissue samples collected over a temporal span. To control for this source of variation, we used a high-precision record of atmospheric CO2 delta13C from ice cores and direct atmospheric measurements to model modern change in CO2 delta13C. From this model, we estimated a correction factor that controls for atmospheric change; this correction reduces bias associated with changes in atmospheric <span class="hlt">isotopic</span> baseline and facilitates comparison of tissue delta13C collected over multiple years. To exemplify the importance of accounting for atmospheric CO2 delta13C depletion, we applied the correction to a dataset of collagen delta13C obtained from mountain lion (Puma concolor) bone samples collected in California between 1893 and 1995. Before correction, in three of four ecoregions collagen delta13C decreased significantly concurrent with depletion of atmospheric CO2 delta13C (n > or = 32, P < or = 0.01). Application of the correction to collagen delta13C data removed trends from regions demonstrating significant declines, and measurement error associated with the correction did not add substantial variation to adjusted estimates. Controlling for long-term atmospheric variation and correcting tissue samples for c