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Sample records for sr-nd isotope study

  1. A combined O, Sr, Nd, and Pb isotopic and trace element study of crustal contamination in central Andean lavas, I. Local geochemical variations

    NASA Astrophysics Data System (ADS)

    James, David E.

    1982-01-01

    Systematic variations in O, Sr, Nd, and Pb isotopic ratios and in Sr, Nd, Pb, and Rb trace element abundances in central Andean andesitic lavas are analyzed in terms of combined crustal assimilation and fractional crystallization. The results of integrated isotopic model calculations show that observed local isotopic and trace element variations within the Arequipa and Barroso volcanic groups of southern Peru are best fit by a simple model involving shallow or intermediate depth crustal assimilation of Charcani gneiss (or an equivalent rock) accompanied by dominantly plagioclase fractional crystallization. A consequence of this result is that the Rb sbnd Sr pseudoisochrons reported for the Arequipa and Barroso volcanics are wholly artifacts of the combined processes of assimilation and plagioclase fractionation, as are all of the Pb isotopic variations measured in the same lavas, already interpreted by Tilton and Barreiro [14] to be the result of crustal contamination. Isotopic and trace element compositions of the primary magmas for the Arequipa and Barroso volcanic series are obtained by correcting for assimilation and fractional crystallization. The starting magmas are characterized over the entire range of permissible primary compositions by high 87Sr/ 86Sr ratios, low 143Nd/ 144Nd ratios, and high Sr concentrations relative to "normal" island arc andesites. These results appear to require prior contamination of the magmas, but not involving plagioclase fractionation. The uncertainty in Pb and O isotope ratios computed for possible primary magmatic compositions is sufficiently large, however, that it is not possible to preclude a subcrustal origin for at least some regional variation in Sr and Nd isotopic ratios.

  2. 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

  3. Sr, Nd, and Pb isotopic character of Tertiary basalts from southwest Poland

    NASA Astrophysics Data System (ADS)

    Blusztajn, Jerzy; Hart, Stanley R.

    1989-10-01

    Tertiary basaltic volcanics from southwest Poland which form the eastern part of the Central European Volcanic Province (CEVP) have been studied for Sr, Nd, and Pb isotopic compositions. 87Sr/86Sr ratios range from 0.70317 to 0.70369, 143Nd/144Nd ratios range from 0.51285 to 0.51302 and Pb isotopic compositions range from 19.42 to 19.94 for 206Pb/204Pb. These data indicate the influence of three end-member mantle components DMM, HIMU and EM. An analysis of all isotopic results from the CEVP leads to the conclusion that basalts from SW Poland have the most depleted character. We propose a model whereby the depleted source mantle for the CEVP interacted with enriched components (EM). The western part of the CEVP was enriched on a larger scale than the eastern part, probably due to the influence of the Rhine Graben rift.

  4. Pb, Sr, Nd and Hf isotopic evidence of multiple sources for Oahu, Hawaii basalts

    NASA Technical Reports Server (NTRS)

    Stille, P.; Unruh, D. M.; Tatsumoto, M.

    1983-01-01

    Pb, Sr, Nd and Hf isotopic compositions of Oahu volcanics indicate that the three principal volcanic series on Oahu Koolau, Honolulu and Waianae - were derived from isotopically distinct sources. Honolulu and Waianae basalts plot on the Nd-Pb-Sr 'mantle plane' whereas Koolau data plot distinctly below the plane.

  5. A petrologic, geochemical and Sr-Nd isotopic study on contact metamorphism and degassing of Devonian evaporites in the Norilsk aureoles, Siberia

    NASA Astrophysics Data System (ADS)

    Pang, Kwan-Nang; Arndt, Nicholas; Svensen, Henrik; Planke, Sverre; Polozov, Alexander; Polteau, Stephane; Iizuka, Yoshiyuki; Chung, Sun-Lin

    2013-04-01

    Devonian evaporites and associated sedimentary rocks in the Norilsk region were contact metamorphosed during emplacement of mafic sills that form part of the end-Permian (~252 Ma) Siberian Traps. We present mineralogical, geochemical and Sr-Nd isotopic data on sedimentary rocks unaffected by metamorphism, and meta-sedimentary rocks from selected contact aureoles at Norilsk, to examine the mechanisms responsible for magma-evaporite interaction and its relation to the end-Permian environmental crisis. The sedimentary rocks include massive anhydrite, rock salt, dolostone, calcareous siltstones and shale, and the meta-sedimentary rocks comprise calcareous hornfels, siliceous hornfels and minor meta-anhydrite and meta-sandstone. Contact metamorphism took place at low pressure and at maximum temperatures corresponding to the phlogopite-diopside stability field. Calcareous hornfels have high CaO, MgO, CΟ2, SΟ3, low SiO2 and initial Sr isotopic ratios of 0.7079-0.7092, features indicative of calcareous siltstone protoliths. Siliceous hornfels, in contrast, have high SiO2, Al2O3, Na2O, low in other major element oxides and initial Sr isotopic ratios of 0.7083-0.7152, consistent with pelitic or shaley protoliths. Loss of CO2 in a subset of calcareous hornfels can be explained by decarbonation reactions during metamorphism, but release of SO2 from evaporites cannot be accounted for by a similar mechanism. Occurrences of wollastonite and a variety of hydrous minerals in the calcareous hornfels are consistent with equilibration with hydrous fluid, which was capable of leaching large quantities of anhydrite in the presence of dissolved NaCl. In this way, substantial sediment-derived sulfur could have been mobilized, incorporated into the magmatic system and released to the atmosphere. The release of CO2 and SO2 from Siberian evaporites added to the variety of toxic gases generated during metamorphism of organic matter, coal and rock salt, contributing to the end

  6. 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.

  7. Sr-Nd-Pb isotope variability across and along the Ecuadorian volcanic arc

    NASA Astrophysics Data System (ADS)

    Ancellin, Marie-Anne; Samaniego, Pablo; Vlastélic, Ivan; Nauret, François; Gannoun, Mouhcine; Hidalgo, Silvana

    2016-04-01

    Determining the contribution of different potential sources in arc magma genesis is of paramount importance for discriminating the role of deep-seated processes at work in the slab and mantle wedge, as well as the process occurring during the magma ascent through the arc crust. The Ecuadorian volcanic arc (2°S - 1°N) results from the subduction of the oceanic Nazca plate below the continental south-American plate. This volcanic province, developed in front of the subducting Carnegie ridge, is characterized by at least 50-60 volcanic centres of Pleistocene-Holocene age, which are distributed along the Western and Eastern Cordilleras and in the back-arc region. Previous studies on this province focused on two main issues: (1) the role of the deep-seated process occurring at the level of the subducting slab and the mantle wedge ([1], [2]), and (2) the role of crustal process ([3]). In this work, we use existing and new (57 samples from 36 volcanoes of the whole Ecuadorian arc) major-trace element and Sr-Nd-Pb isotope data to resolve precisely magma compositional changes occurring across and along the volcanic arc and to precise the role of the heterogeneous crust underlying this arc segment. In the 207Pb/204Pb vs. 206Pb/204Pb diagram, most of Western Cordillera volcanic centres and Back arc volcanoes display a flat trend characterized by a large variation in 206Pb/204Pb (18.5 - 19.15), with little variation in 207Pb/204Pb (15.54-15.62). Along this trend, back arc volcanoes tend towards unradiogenic compositions with Reventador as end-member whereas western cordilleras volcanoes generally show more radiogenic compositions (Pilavo, Imbabura). In contrast, the Eastern cordillera volcanoes display more radiogenic 207Pb/204Pb (15.60 - 15.70) or 208Pb/204Pb (38.7 - 39) at a given 206Pb/204Pb compared to the Western cordillera with similar variation in 206Pb/204Pb (18.85 - 19.05). Extreme compositions are observed at Tungurahua and Antisana volcanoes. Several volcanoes of

  8. 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.

  9. 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.

    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

  10. 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.

  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. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Sr-Nd-Pb isotope systematics of the Banda Arc, Indonesia: Combined subduction and assimilation of continental material

    NASA Astrophysics Data System (ADS)

    Vroon, P. Z.; van Bergen, M. J.; White, W. M.; Varekamp, J. C.

    1993-12-01

    We present Sr, Nd, and Pb isotope results and SiO2, Rb, Sr, Sm, Nd, U, Th, and Pb data for six active volcanoes and one extinct volcanic island distributed over the whole length of the Banda Arc. Rock types range from low-K tholeiitic in the NE to high-K calc-alkaline in the SW. The volcanoes in the NE have 'normal' arc signatures, whereas those in the SW have extreme values. Serua, situated in the central part, is the most anomalous volcano with regard to its Sr and Nd isotopic composition but not with regard to Pb isotopes. The inactive island of Romang in the SW overlaps the Serua trends. The volcanoes display variable within-suite ranges in Sr-87/Sr-86 and Nd-143/Nd-144. Large ranges (e.g., at Nila) are consistent with assimilation (10-20%) of carbonate-bearing sediments from the arc crust. Despite the evidence for assimilation, it cannot explain all of the Sr-Nd isotopic trends found, and Banda Arc magmas must have already obtained a 'continental' signature at depth before they reached the arc crust. Within-suit trends of Pb isotopes are virtually absent. We found an extreme range in the volcanics along the arc which coincide with a similar trend in sediments in front of the arc and consider this as strong evidence for the contribution of subducted continent-derived material to magma sources.

  18. 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

  19. 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

  20. Pb, Sr, Nd, and Hf isotopic constraints on the origin of Hawaiian basalts and evidence for a unique mantle source

    NASA Technical Reports Server (NTRS)

    Stille, P.; Unruh, D. M.; Tatsumoto, M.

    1986-01-01

    The isotopic Pb, Sr, Nd, and Hf compositions of rocks from nine Hawaiian volcanos are determined using the analytical procedures described by Tatsumoto and Unruh (1976) and Patchett and Tatsumoto (1980). The results are presented in graphs, tables, and maps and characterized in detail. The mantle plume, the oceanic lithosphere, and the depleted mantle are identified as distinct sources of the Hawaiian basalts, with different mechanisms responsible for the formation of shield-building tholeiites, late-stage alkalic rocks, and posterosional basalts. The uniqueness of the Hawaiian basalts and the possibility that the Koolau end member represents an undepleted 'primitive' mantle reservoir are considered.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Ca-Mg-Sr-Nd Isotopes in Granitic Rocks of the Lhasa Terrane, Southern Tibet

    NASA Astrophysics Data System (ADS)

    Peterson, B. T.; Simon, J. I.; Depaolo, D. J.; Christensen, J. N.; Harrison, T. M.

    2010-12-01

    Magnesium (Mg) and Calcium (Ca) isotopes are fractionated by aqueous precipitation and incongruent silicate weathering, resulting in sedimentary reservoirs with characteristic isotopic compositions. Limestones and dolomites are isotopically light in both elements, whereas shales/pelites can have heavy Mg and light Ca. The isotopic character of these reservoirs may persist through anatexis (Shen, et al., PNAS 106(49), 2009). Mg and Ca isotopes could therefore be used to gain new insights into the sources of granitic magmas and hence the mechanisms by which the continental crust forms and evolves. Radiogenic 40Ca gives additional information about the K/Ca ratios of magma sources, and Sr and Nd isotopes provide complementary age and lithology information. To evaluate the potential of Ca and Mg isotopes for studying granite petrogenesis we made measurements on a suite of granitic intrusive rocks of Jurassic to Miocene age in southern Tibet that exhibit large variations in Nd (ɛNd = +5 to -12) and Sr isotopes (87Sr/86Sr = 0.704 to 0.722). Our samples represent a transect northward from the Indus-Yalu Suture (IS), west of Lhasa. Rocks close to the IS have mantle-like Nd and Sr isotopic compositions, whereas those farther to the north have low ɛNd and higher 87Sr/86Sr, and include Mesozoic, Paleogene and Neogene peraluminous (2-mica) granites (DePaolo, et al., Goldschmidt, 2008; Kapp, et al., JGR 110, 2005; Hou et al., EPSL 220, 2004). Radiogenic 40Ca is detectable in peraluminous (2-mica) granites and correlates with high 87Sr/86Sr, but does not correlate with Nd isotopes, indicating that 2-mica granite magmas come from both low-K and high-K sources. Stable isotopes of both Ca and Mg show substantial variation. Relative to bulk silicate Earth (BSE, which we define as δ=0 for discussion) δ44Ca values vary from 0 to -0.7, and δ26Mg varies from -0.3 to +0.6. Thus to first order Ca is light and Mg is heavy relative to BSE. For samples with mantle-like Nd and Sr, δ44Ca

  8. 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.

  9. Source and evolution of the "perfect Asian dust storm" in early April 2001: Implications of the Sr-Nd isotope ratios

    NASA Astrophysics Data System (ADS)

    Nakano, Takanori; Nishikawa, Masataka; Mori, Ikuko; Shin, Kicheol; Hosono, Takahiro; Yokoo, Yoriko

    The "perfect Asian dust storm," so-called from the huge, clear picture obtained of it by earth-orbiting satellites, occurred over a vast area of northern China and Mongolia and moved eastward across the northern Pacific in early April 2001. We determined the Sr-Nd isotopic ratios of acid-resistant minerals and the Sr isotopic ratios of weak-acid-soluble minerals in the dust from this storm deposited at nine sites from northern China to Japan and compared these data with those ratios of surface arid soils in northern China. The isotopic compositions of the dust minerals resembled those from soils of the Badain Juran, Tengger, and Ulan Buh deserts and the area to their north, which on meteorological grounds are considered to be the emission area of the dust plume, but they varied regionally, reflecting the heterogeneity of the source soils. Our results and those of other meteorological and modeling studies suggest that this variation was caused by mixing with local soils uplifted into the lower part of the dust plume, but further downwind the dust was less mixed with local soils and was derived mainly from the upper dust plume. Mineral isotope, mineralogical, and elemental data on Asian dusts and soils in northern China and Mongolia provide invaluable information on physical and chemical processes of dust storms and on dust source areas.

  10. 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

  11. 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

  12. Low-degree melting of a metasomatized lithospheric mantle for the origin of Cenozoic Yulong monzogranite-porphyry, east Tibet: Geochemical and Sr Nd Pb Hf isotopic constraints

    NASA Astrophysics Data System (ADS)

    Jiang, Yao-Hui; Jiang, Shao-Yong; Ling, Hong-Fei; Dai, Bao-Zhang

    2006-01-01

    SHRIMP zircon U-Pb dating, mineral chemical, element geochemical and Sr-Nd-Pb-Hf isotopic data have been determined for the Yulong monzogranite-porphyry in the eastern Tibet, China. The Yulong porphyry was emplaced into Triassic strata at about 39 Ma. The rocks are weakly peraluminous and show shoshonitic affinity, i.e., alkalis-rich, high K 2O contents with high K 2O / Na 2O ratios, enrichment in LREE and LILE. They also show some affinities with the adakite, e.g., high SiO 2 and Al 2O 3, and low MgO contents, depleted in Y and Yb, and enrichment in Sr with high Sr / Y and La / Yb ratios, and no Eu anomalies. The Yulong porphyry has radiogenic 87Sr / 86Sr (0.7063-0.7070) and unradiogenic 143Nd / 144Nd ( ɛNd = - 2.0 to - 3.0) ratios. The Pb isotopic compositions of feldspar phenocrysts separated from the Yulong porphyry show a narrow range of 206Pb / 204Pb ratios (18.71-18.82) and unusually radiogenic 207Pb / 204Pb (15.65-15.67) and 208Pb / 204Pb (38.87-39.00) ratios. In situ Hf isotopic composition of zircons that have been SHRIMP U-Pb dated is characterized by clearly positive initial ɛHf values, ranging from + 3.1 to + 5.9, most between + 4 and + 5. Phenocryst clinopyroxene geothermometry of the Yulong porphyry indicates that the primary magmas had anomalously high temperature (> 1200 °C). The source depth for the Yulong porphyry is at least 100 km inferred by the metasomatic volatile phase (phlogopite-carbonate) relations. Detailed geochemical and Sr-Nd-Pb-Hf isotopic compositions not only rule out fractional crystallization or assimilation-fractional crystallization processes, but also deny the possibility of partial melting of subducted oceanic crust or basaltic lower crust. Instead, low degree (1-5%) partial melting of a metasomatized lithosphere (phlogopite-garnet clinopyroxenite) is compatible with the data. This example gives a case study that granite can be derived directly by partial melting of an enriched lithospheric mantle, which is important to

  13. 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.

  14. Petrology and Sr-Nd-Pb isotope geochemistry of Late Cretaceous continental rift ignimbrites, Kap Washington peninsula, North Greenland

    NASA Astrophysics Data System (ADS)

    Thorarinsson, Sigurjon B.; Holm, Paul M.; Duprat, Helene I.; Tegner, Christian

    2012-03-01

    The Late Cretaceous-Palaeocene (71-61 Ma) Kap Washington Group (KWG) volcanic sequence is exposed at the north coast of Greenland. The sequence is bimodal and was erupted in a continental rift setting during the opening of the Arctic Ocean. The succession exposed on the Kap Washington peninsula, which forms the bulk of the KWG sequence (> 5 km thick), has been sampled along four traverses with a combined stratigraphic thickness of ca. 1500 m. The sampled sequence is dominated by silicic ignimbrites (69-79 wt.% SiO2) showing geochemical features typical of ferroan, A-type granitoids. The ignimbrites range from sparsely phyric, mildly peraluminous compositions [ASI = Al2O3/(CaO + Na2O + K2O) = 1.05-1.20] to feldspar + quartz ± sodic amphibole ± Fe-Ti oxide phyric peralkaline compositions [PI = (Na2O + K2O)/Al2O3 = 1.00-1.40]. The peraluminous ignimbrites appear to overlie the peralkaline ignimbrites, although stratigraphy is complicated by faulting. Fiamme imbrication indicates that both types were erupted from a vent area located north of the Kap Washington peninsula. The peralkaline ignimbrites have Sr-Nd-Pb isotopic compositions which overlap with the compositions of KWG basalts, indicating a dominantly basaltic source. The more peralkaline compositions were generated by up to ca. 50% fractional crystallisation of alkali feldspar-quartz-dominated assemblages from mildly peralkaline parental magmas, themselves probably derived by fractionation of trachytic magmas. The peraluminous ignimbrites have slightly negative ɛNd(i) and more radiogenic 207Pb/204Pbi and 208Pb/204Pbi. Modelling indicates that they are not cogenetic with the peralkaline ignimbrites and they are inferred to have originated by partial melting of hybridised mafic crust. Petrographic evidence suggests that magma mixing was an important process and variations in Nd-Pb isotopes and trace element ratios indicate mixing between peralkaline and peraluminous magma batches.

  15. 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

  16. Sr, Nd, Pb and Hf isotopic constraints on mantle sources and crustal contaminants in the Payenia volcanic province, Argentina

    NASA Astrophysics Data System (ADS)

    Søager, Nina; Holm, Paul Martin; Thirlwall, Matthew F.

    2015-01-01

    The presented Sr, Nd, Hf and double-spike Pb-isotopic analyses of Quaternary basalts from the Payenia volcanic province in southern Mendoza, Argentina, confirm the presence of two distinct mantle types feeding the Payenia volcanism. The southern Payenia mantle source feeding the intraplate-type Río Colorado and Payún Matrú volcanism is isotopically distinct from the northern Payenia and arc mantle source with less radiogenic Pb and lower 87Sr/86Sr and 176Hf/177Hf for a given 143Nd/144Nd than the northern Payenia and arc rocks. The basalts from the northern Payenia province (Nevado volcanic field) and the retroarc zone have isotopic compositions overlapping the Andean southern volcanic zone (SVZ) arc rocks and they are probably derived from the same metasomatized South Atlantic N-MORB-like mantle source. A high field strength element melting model suggests addition of ~ 1-2% upper continental crustal material to the mantle source of the Nevado basalts and the transitional SVZ arc and retroarc rocks and similar degrees of melting throughout this arc segment. A gradual depletion of the pre-metasomatic mantle source going from the backarc over the retroarc to the arc is indicated. The depletion is suggested to be caused by step-wise melt extraction due to repeated injections of subduction zone fluids and melts. The lower crustal contamination trends found in the trace element variations of basalt groups from all parts of the Payenia province are also recognized in isotopic space and the dominant isotope assimilation trends indicate lower crustal contaminants with more unradiogenic Pb, lower 143Nd/144Nd and 176Hf/177Hf and higher or similar 87Sr/86Sr as the mantle melts. These characteristics are similar to those found in lower crustal xenoliths from the northern Proterozoic Cuyania terrane, and the Payenia basalts may have been contaminated by this type of crust during passage through the lithosphere or by more recently underplated or intruded material.

  17. 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.

  18. 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.

  19. 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.

  20. Sr, Nd, Pb and Hf Isotopic Compositions of Late Cenozoic Alkali Basalts in South Korea: Evidence for Mixing Between the Two Dominant Asthenospheric Mantle Domains beneath East Asia

    NASA Astrophysics Data System (ADS)

    Choi, S.; Mukasa, S. B.; Kwon, S.; Andronikov, A. V.

    2004-12-01

    We determined the Sr, Nd, Pb and Hf isotopic compositions of late Cenozoic basaltic rocks from six lava-field provinces in South Korea, including Baengnyeong Island, Jogokni, Ganseong area, Jeju Island, Ulleung Island and Dog Island, in order to understand the nature of the mantle source. The basalts have OIB-like trace element abundance patterns, and also contain mantle-derived xenoliths. Available isotope data of late Cenozoic basalts from East Asia, along with ours, show that the mantle source has a DMM-EM1 array for northeast China and a DMM-EM2 array for Southeast Asia. We note that the basalts falling on an array between DMM and an intermediate end member between EM1 and EM2, are located between the two large-scale isotopic provinces, i.e., around the eastern part of South Korea. The most intriguing observation on the isotopic correlation diagrams is spatial variation from predominantly EM2 signatures in the basaltic lavas toward increasingly important addition of EM1, starting from Jeju Island to Ulleung and Dog Islands to Ganseong area, and to Baengnyeong Island. This is without any corresponding changes in the basement and the lithospheric mantle beneath the region. These observations suggest that the asthenospheric mantle source is dominant for the Cenozoic intraplate volcanism in East Asia, which is characterized by two distinct, large-scale domains. Previous studies on East Asian Cenozoic volcanic rocks have invoked origins by either plume activity or decompressional melting in a rift environment. On the basis of our new trace element and isotopic compositions which have OIB-like characteristics, we prefer a plume origin for these lavas. However, because tomographic images do not show distinct thermal anomaly that would be interpreted as a plume, we suggest that the magmatism might be the product of small, difficult to image multiple plumes that tapped the shallow part of the asthenosphere (probably the transition zone in the upper mantle).

  1. Metasomatized lithospheric mantle beneath Turkana depression in southern Ethiopia (the East Africa Rift): geochemical and Sr-Nd-Pb isotopic characteristics

    NASA Astrophysics Data System (ADS)

    Meshesha, Daniel; Shinjo, Ryuichi; Matsumura, Risa; Chekol, Takele

    2011-11-01

    Mantle xenoliths entrained in Quaternary alkaline basalts from the Turkana Depression in southern Ethiopia (the East Africa Rift) were studied for their geochemical and Sr-Nd-Pb isotopic compositions to constrain the evolution of the lithosphere. The investigated mantle xenoliths are spinel lherzolites in composition with a protogranular texture. They can be classified into two types: anhydrous and hydrous spinel lherzolites; the latter group characterized by the occurrences of pargasite and phlogopite. The compositions of whole-rock basaltic component (CaO = 3.8-5.6 wt%, Al2O3 = 2.5-4.1 wt%, and MgO = 34.7-38.1 wt%), spinel (Cr# = 0.062-0.117, Al2O3 = 59.0-64.4 wt%) and clinopyroxene (Mg# = 88.4-91.7, Al2O3 = 5.2-6.7 wt%) indicate that the lherzolites are fertile and have not experienced significant partial melting. Both types are characterized by depleted 87Sr/86Sr (0.70180-0.70295) and high 143Nd/144Nd (0.51299-0.51348) with wide ranges of 206Pb/204Pb (17.86-19.68) isotopic compositions. The variations of geochemical and isotopic compositions can be explained by silicate metasomatism induced by different degree of magma infiltrations from ascending mantle plume. The thermobarometric estimations suggest that the spinel lherzolites were derived from depths of 50-70 km (15.6-22.2 kb) and entrained in the alkaline magma at 847-1,052°C. Most of the spinel lherzolites from this study record an elevated geotherm (60-90 mW/m2) that is related to the presence of rising mantle plume in an active tectonic setting. Sm-Nd isotopic systematic gives a mean TDM model age of 0.95 Ga, interpreted as the minimum depletion age of the subcontinental lithosphere beneath the region.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Rare earth elements and Sr-Nd-Pb isotopic analyses of the Arima hot spring waters, Southwest Japan: Implications for origin of the Arima-type brine

    NASA Astrophysics Data System (ADS)

    Nakamura, H.; Fujita, Y.; Nakai, S.; Yokoyama, T.; Iwamori, H.

    2014-12-01

    Rare earth elements (REEs) and Sr-Nd-Pb isotopic compsotions of the Arima hot spring waters, a specific type of deep-seated brine (up to 6 wt.% NaCl) in the non-volcanic fore-arc region of southwest Japan, have been analyzed in order to discuss their source materials and origins. We have first examined the matrix effect associated with variable salinity (0 to 5 wt.% NaCl), and found that above 1 wt.% NaCl, the intensity of REE in ICP-MS measurement is drastically reduced due to the matrix effect. Accordingly, we have diluted the sample waters to contain ~0.6 wt.% NaCl, and then analyzed them by the standard addition method. The result shows that the abundance is appreciably high compared to near-surface waters, and exhibits almost a flat DMM-normalized pattern, which can be explained by mixing of a slab-derived fluid at relatively low temparature (400 to 500 ºC) and a near-surface water. The Sr-Nd-Pb isotopic compositions of the brine are consistent with the above interpretation on REEs, in that the deep brine is isotopically similar to a slab-derived fluid of the subducted Philippine Sea slab. These evidences suggest that the slab-derived fluid is upwelling even in the non-volcanic region possibly through a fault zone along the tectonic line.

  7. 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

  8. 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.

  9. 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.

  10. 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

    2016-06-01

    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.

  11. Two isotopically distinct fluid components involved in the Mariana arc: Evidence from Nb/B ratios and B, Sr, Nd, and Pb isotope systematics

    NASA Astrophysics Data System (ADS)

    Ishikawa, Tsuyoshi; Tera, Fouad

    1999-01-01

    Nb/B ratios and δ11B values of Mariana lavas reveal the involvement of two isotopically distinct slab-derived fluids in the magma genesis. The evidence of one type of fluid is observed in lavas of the islands of Anatahan, Alamagan, Agrigan, and Uracas, in which simple mixing between fluid with very homogeneous δ11B values (+5.40‰ ± 0.05‰) and the mantle wedge controls the magma compositions. In lavas of the islands of Guguan, Asuncion, and Pagan, however, the fluids that mixed with the mantle wedge are significantly heterogeneous in δ11B (+5.4‰ to +7.6‰) even within a single island. The compositional difference between these two types of fluid can result from different ratios of sediment to altered oceanic crust (AOC) in the slabs, and this hypothesis is consistent with the Sr, Nd, and Pb isotope data. We propose that the variable isotope compositions of the latter fluid may be derived from local changes in sediment/AOC ratios of the slab that are caused by subduction of the Magellan seamounts beneath the Mariana arc.

  12. Geochemical and Sr-Nd-Hf-O-C isotopic constraints on the origin of the Neoproterozoic Qieganbulake ultramafic-carbonatite complex from the Tarim Block, Northwest China

    NASA Astrophysics Data System (ADS)

    Ye, Hai-Min; Li, Xian-Hua; Lan, Zhong-Wu

    2013-12-01

    The Qieganbulake ultramafic-carbonatite complex located within the northeastern margin of the Tarim Block of Northwest China hosts the world's second largest vermiculite deposit. Field observations, radiometric dating results and Sr-Nd-Hf isotopes reveal that the parental magmas of the carbonatite and ultramafic rocks are cogenetic and formed synchronously at ~ 810 Ma. They are characterized by unusually enriched Sr-Nd-Hf isotopic compositions (ISr = 0.70570-0.70762, εNd(t) = - 7.7 to - 12.5, and εHf(t) = - 6.7 to - 12.9), indicating that the parent magmas were derived mainly from a subcontinental mantle source that had been metasomatised by subduction processes. Higher δ13C (- 3.65 to - 4.11‰) values compared to primary magmatic carbonate (- 8 to - 4‰) argue for incorporation of recycled inorganic carbon derived from subducted oceanic crusts. The carbonatites and clinopyroxenties define two distinct differentiation trends, which suggest that liquid immiscibility rather than crystal fractionation controlled the petrogenetic process. Pyroxenities have clearly higher apatite ISr and δ18O values than coexisting carbonatites, indicating involvement of crustal components during their emplacement. The Qieganbulake complex is closely associated in time and space with the mid-Neoproterozoic Rodinia breakup event triggered by mantle plume activities in the Tarim Block. Therefore, the mantle plume likely induced partial malting of, and likely mixed with, the metasomatized subcontinental lithospheric mantle, to form the Qieganbulake ultramafic-carbonatite complex.

  13. 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

  14. 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

  15. 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

  16. 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

  17. U-Pb zircon dating, geochemical and Sr-Nd-Hf isotopic compositions of Early Indosinian intrusive rocks in West Qinling, central China: petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Luo, Biji; Zhang, Hongfei; Lü, Xinbiao

    2012-10-01

    The Qinling-Dabie-Sulu orogenic belt is the junction between the North and South China blocks, which resulted from the final amalgamation of China continents during the Indosinian. Indosinian granitoids are widespread in the Qinling orogen, and their geneses can thus constrain the evolution of China continent. We carried out a combined U-Pb zircon dating and geochemical study for the Shuangpengxi granodiorite pluton and the Xiekeng diorite-granodiorite pluton in the middle part of the West Qinling orogen. U-Pb zircon dating shows that the magma crystallization ages of 242 ± 3 Ma for the Shuangpengxi pluton and ~244-242 Ma for the Xiekeng pluton. Geochemical and Sr-Nd-Hf isotopic compositions reveal that the magma of the Shuangpengxi granodiorite was derived from partial melting of crustal materials. The Xiekeng diorites can be divided into high-Al diorite and high-Mg diorite. Both of them resulted from partial melting of enriched lithospheric mantle, but their mantle source had been modified by previous slab-derived melt. The high-Al diorite was formed by fractional crystallization of olivine, pyroxene and/or preferential accumulation of plagioclase, and the high-Mg diorite was formed by fractional crystallization of olivine and/or preferential accumulation of pyroxene. The Xiekeng granodioritic porphyry was formed by mixing of crust-derived and mantle-derived melts. We propose that the Early Indosinian magmatism resulted from break-off of subducted oceanic slab after collision. The slab break-off model can well explain the linear distribution of the Early Indosinian plutons and rapid crustal uplift during the Middle Triassic in the West Qinling.

  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. 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

  20. 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.

  1. 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

  2. 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

  3. 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

  4. Interaction between ultrapotassic magmas and carbonate rocks: Evidence from geochemical and isotopic (Sr, Nd, O) compositions of granular lithic clasts from the Alban Hills Volcano, Central Italy

    NASA Astrophysics Data System (ADS)

    Peccerillo, Angelo; Federico, Marcella; Barbieri, Mario; Brilli, Mauro; Wu, Tsai-Wan

    2010-05-01

    Magma-carbonate rock interaction is investigated through a geochemical and Sr-Nd-O isotope study of granular lithic clasts ( ejecta) from the Alban Hills ultrapotassic volcano, Central Italy. Some samples (Group-1) basically represent intrusive equivalents of Alban Hills magmas. A few samples (Group-2) are ultramafic, have high MgO (˜30 to 40 wt%) and δ 18O‰, and originated by accumulation of mafic phases that crystallised from ultrapotassic melts during assimilation of dolomitic rocks. Group-3 ejecta consist of dominant K-feldspar, and show major element compositions similar to phonolites, which, however, are absent among the Alban Hills volcanics. Finally, another group (Group-4) contains corroded K-feldspars, surrounded by a microgranular to porphyritic matrix, made of igneous minerals (K-feldspar, foids, clinopyroxene, phlogopite) plus wollastonite, garnet, and some cuspidine. Group-4 ejecta are depleted in SiO 2 and enriched in CaO with respect to Group-3. The analysed ejecta have similar 143Nd/ 144Nd (0.51204-0.51217) as the Alban Hills lavas, whereas 87Sr/ 86Sr (0.70900-0.71067) is similar to lower. Whole rocks δ 18O‰ ranges from +7.0 to +13.2, reaching maximum values in ultramafic samples. A positive correlation with CaO is observed in single rock groups. Large Ion Lithophile Element (LILE) abundances and REE fractionation are generally high, and extreme values of Th, U and LREE are found in some Group-3 and Group-4 rocks. Mineralogical, petrological and geochemical data reveal extensive interaction between magma and carbonate wall rocks, involving both dolostones and limestones. These processes had dramatic effects on magma compositions, especially on phonolites, which were transformed to foidites. Evidence of such a process is found in Group-4 samples, in which K-feldspar is observed to react with a matrix that represents strongly undersaturated melts formed by interaction between silicate magma and carbonates. Trace element data also testify to a

  5. Lithospheric origin for Neogene-Quaternary Middle Atlas lavas (Morocco): Clues from trace elements and Sr-Nd-Pb-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Bosch, Delphine; Maury, René C.; El Azzouzi, M'hammed; Bollinger, Claire; Bellon, Hervé; Verdoux, Patrick

    2014-09-01

    This study presents new geochemical data on 26 mafic lavas from the Middle Atlas and Central Morocco volcanic provinces, including Miocene nephelinites and Pliocene-Quaternary (3.9-0.6 Ma) nephelinites, basanites, alkali and subalkaline basalts. Most of them represent near-primary magmas, although some alkali basalts were derived from the minor fractionation of olivine and diopside phenocrysts. These evolved samples and the subalkaline basalt display higher 207Pb/204Pb and Zr/Nb ratios and lower εNd consistent with their contamination by lower crustal granulites during an open fractionation process. The progressive enrichment in incompatible elements observed from alkali basalts to nephelinites suggests their derivation from decreasing partial melting degrees of an enriched mantle source located at the garnet-spinel transition zone. The strong negative spikes observed for K in multielement patterns indicate that this source contained a residual pargasitic amphibole. We propose that partial melting occurred at around 2 GPa, i.e. near the lithosphere-asthenosphere boundary beneath the Middle Atlas (60-80 km). The trace element and isotopic Sr-Nd-Pb-Hf signature of the uncontaminated lavas displays a geochemical flavour intermediate between those of high μ (HIMU), “C”, and enriched mantle components. It is very similar to that of abundant metasomatic amphibole- and clinopyroxene-rich lithospheric peridotites and pyroxenites carried by Middle Atlas lavas, which likely represent an analog of the source of these lavas. It is therefore not necessary to postulate the contribution of a “fresh” asthenospheric mantle to their genesis. We propose that they resulted from the partial melting of the base of a veined lithospheric mantle metasomatised during the late Cretaceous by alkaline melts from the Central Atlantic plume, the ancestor of the Canary plume. Melting was probably triggered by the flux of a hot mantle within a regional SW-NE sub-lithospheric channel, in

  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. Trindade and Martı´n Vaz Islands, South Atlantic: Isotopic (Sr, Nd, Pb) and trace element constraints on plume related magmatism

    NASA Astrophysics Data System (ADS)

    Siebel, W.; Becchio, R.; Volker, F.; Hansen, M. A. F.; Viramonte, J.; Trumbull, R. B.; Haase, G.; Zimmer, M.

    2000-05-01

    Highly alkaline silica undersaturated lavas erupted at Trindade Island over its 5 Ma geologic history and comprise primitive nephelinites-basanites and more evolved nepheline-bearing phonolitic rocks. Nephelinites-basanites and phonolitic rocks are thought to be genetically related via crystal fractionation, as indicated by the very limited range in Sr, Nd and Pb isotope ratios, systematically increasing contents of incompatible trace elements from primitive to evolved rock types, and similar variation in chemical composition of the major phenocryst phases (clinopyroxene, amphibole, feldspar) in all rock types. Tb/Yb ratios of the primitive lavas are high (2.6-4.1) and silica contents are low (39.8-42.9 wt.% SiO 2), indicating that the melts were generated at deep mantle depths (˜150 km), within the garnet lherzolite stability field. Non-radiogenic 87Sr/ 86Sr (0.70377-0.70421) and radiogenic 143Nd/ 144Nd (0.512752-0.512837) values show that the Trindade and Martı´n Vaz rocks are derived from moderately depleted sources relative to bulk-earth. The lavas have moderate radiogenic 206Pb/ 204Pb ratios of 19.00-19.33, 207Pb/ 204Pb of 15.56-15.60, and 208Pb/ 204Pb of 38.89-39.34; they plot close to the Northern Hemisphere Reference Lines (NHRL). The narrow range of Sr, Nd, and Pb isotopic compositions in the Trindade and Martı´n Vaz lavas suggests either that the source region was homogeneous (similar to the common mantle components FOZO and "C"), or that melts from a heterogeneous three-component mantle source, involving HIMU, enriched mantle EM I, and depleted N-type MORB, were well mixed before eruption. Late Cretaceous to Present volcanism ranging from interior Brazil towards Trindade is thought to record the passage of the South American plate over the Trindade mantle plume (e.g., O'Connor and Duncan, 1990). Comparison with published data from other mafic rocks along the suggested plume track shows that Trindade isotopic compositions match those of transitional

  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. Atmospheric pollution in an urban environment by tree bark biomonitoring - part II: Sr, Nd and Pb isotopic tracing.

    PubMed

    Guéguen, Florence; Stille, Peter; Lahd Geagea, Majdi; Perrone, Thierry; Chabaux, François

    2012-02-01

    The harmful effect of manmade particles on natural processes and human health is documented by a large number of studies showing a positive correlation between particulate matter (PM) concentration and health effects. Diminution of this health risk necessitates among others the precise knowledge of the particle sources, their physical and chemical properties and their dissemination in the environment. Pb isotope ratios have been successfully used during the past decades as tracers of anthropogenic Pb disseminated in the biosphere. Here we show that tree bark biomonitoring with lead (Pb), strontium (Sr) and neodymium (Nd) isotope ratios as tracers allow a thorough analysis of the impacts of industrial and other anthropogenic emissions on the urban environment. This is the first comprehensive multi-isotope tracer study of atmospheric pollution in an urban environment allowing to identify and to integrate the different plume paths of emissions in a digital map system. This innovative approach might become an important tool for environmental management and policy-making processes dealing especially with risks and surveillance of air quality in the urban environment. PMID:22154157

  11. 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.

  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. 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

  15. Geochemistry, Sr-Nd isotope composition, and tectonic setting of Holocene Pelado, Guespalapa and Chichinautzin scoria cones, south of Mexico City

    NASA Astrophysics Data System (ADS)

    Siebe, Claus; Rodríguez-Lara, Virgilio; Schaaf, Peter; Abrams, Michael

    2004-02-01

    Holocene Pelado, Guespalapa and Chichinautzin monogenetic scoria cones and associated lava flows located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were mapped and sampled for mineralogical and chemical analyses. With the exception of Parı´cutin volcano in western Mexico, few scoria cones in the Trans-Mexican Volcanic Belt have ever been sampled in greater detail. Chemical analyses of rocks indicate that mafic products (e.g. Guespalapa and Chichinautzin) from individual volcanoes in the Sierra del Chichinautzin are characterized by substantial chemical variability, whereas high-silica andesite volcanoes (e.g. Pelado) are very uniform in composition. These findings have important bearings for regional tephrochronology. As a whole, rock compositions form a continuous coherent calc-alkaline suite, explicable by polybaric fractional crystallization±assimilation associated with successive stagnation at different depths along the ascent path. Trace element and Sr-Nd isotope analyses point toward a <1-km-scale heterogeneous (enriched/depleted) mantle wedge underneath the SCVF. The recently proposed plume-origin for these rocks is not in accord with our data. Instead, magma origin is discussed in relation to the tectonically complex subduction process of the oceanic Cocos Plate underneath the continental North American Plate.

  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. 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.

  18. U-Pb geochronology and Sr/Nd isotope compositions of groundmass perovskite from the newly discovered Jurassic Chidliak kimberlite field, Baffin Island, Canada

    NASA Astrophysics Data System (ADS)

    Heaman, Larry M.; Pell, Jennifer; Grütter, Herman S.; Creaser, Robert A.

    2015-04-01

    We report the U-Pb age and Sr/Nd isotope composition for perovskite isolated from forty six kimberlite samples located in the newly discovered Chidliak field on Baffin Island, Canada. The minimum duration of kimberlite magmatism in this field was 17.9 m.y. from 157.0 to 139.1 Ma and represents a new Jurassic kimberlite field in NE Canada. The most prolific period of kimberlite magmatism occurred between 152 and 142 Ma (80% of dated kimberlites). Kimberlitic perovskite from these intrusions display a range in 87Sr/86Sr (0.7043 to 0.7030) and εNdT values (+3.9 to -0.4), overlapping the isotopic field previously defined for southern African Group I kimberlites. The ages and isotopic compositions obtained for Chidliak magmatism are identical to a number of Jurassic kimberlite fields in eastern North America and SW Greenland. Some of this Jurassic kimberlite magmatism has a link to one or more mantle plume hotspot tracks but the Chidliak kimberlites have an origin in the deep subcontinental lithospheric mantle and are part of a Jurassic magmatic province that erupted along both margins of Davis Strait; linked to upwelling asthenosphere, continental rifting, and Mesozoic-Cenozoic development of oceanic crust in the Labrador Sea basin. In contrast, the location of other eastern North American Jurassic kimberlites when plotted on a Jurassic continental reconstruction aligns closely to the northernmost projection of contours 2-4 of the African large low shearwave velocity province, consistent with a link to mantle plumes derived from the African mantle plume generating zone.

  19. Elemental and Sr Nd Pb isotopic geochemistry of Late Paleozoic volcanic rocks beneath the Junggar basin, NW China: Implications for the formation and evolution of the basin basement

    NASA Astrophysics Data System (ADS)

    Zheng, Jianping; Sun, Min; Zhao, Guochun; Robinson, Paul T.; Wang, Fangzheng

    2007-03-01

    The basement beneath the Junggar basin has been interpreted either as a micro-continent of Precambrian age or as a fragment of Paleozoic oceanic crust. Elemental and Sr-Nd-Pb isotopic compositions and zircon Pb-Pb ages of volcanic rocks from drill cores through the paleo-weathered crust show that the basement is composed mainly of late Paleozoic volcanic rock with minor shale and tuff. The volcanic rocks are mostly subalkaline with some minor low-K rocks in the western Kexia area. Some alkaline lavas occur in the central Luliang uplift and northeastern Wulungu depression. The lavas range in composition from basalts to rhyolites and fractional crystallization played an important role in magma evolution. Except for a few samples from Kexia, the basalts have low La/Nb (<1.4), typical for oceanic crust derived from asthenospheric melts. Zircon Pb-Pb ages indicate that the Kexia andesite, with a volcanic arc affinity, formed in the early Carboniferous (345 Ma), whereas the Luliang rhyolite and the Wucaiwan dacite, with syn-collisional to within-plate affinities, formed in the early Devonian (395 and 405 Ma, respectively). Positive ɛNd( t) values (up to +7.4) and low initial 87Sr/ 86Sr isotopic ratios of the intermediate-silicic rocks suggest that the entire Junggar terrain may be underlain by oceanic crust, an interpretation consistent with the juvenile isotopic signatures of many granitoid plutons in other parts of the Central Asia Orogenic Belt. Variation in zircon ages for the silicic rocks, different Ba, P, Ti, Nb or Th anomalies in the mafic rocks, and variable Nb/Y and La/Nb ratios across the basin, suggest that the basement is compositionally heterogeneous. The heterogeneity is believed to reflect amalgamation of different oceanic blocks representing either different evolution stages within a single terrane or possibly derivation from different terranes.

  20. Elemental and Sr-Nd-Hf isotopic constraints on the origin of Late Jurassic adakitic granodiorite in central Fujian province, southeast China

    NASA Astrophysics Data System (ADS)

    Wang, Guo-Chang; Jiang, Yao-Hui; Liu, Zheng; Ni, Chun-Yu; Qing, Long; Zhang, Qiao

    2015-08-01

    This paper presents the first detailed SHRIMP or LA-ICP-MS zircon U-Pb dating, major and trace element geochemical and Sr-Nd-Hf isotopic data of an adakitic pluton (Tangquan pluton) and an I-type granitic pluton (Xiadao pluton) in central Fujian. SHRIMP and LA-ICP-MS zircon U-Pb dating indicates that the Tangquan and Xiadao plutons were emplaced in the Late Jurassic (~160 Ma) and Early Cretaceous (~143 Ma), respectively. The Tangquan pluton is mainly composed of high-K calc-alkaline granodiorite. The rocks show adakitic affinities, characterized by high Sr and low Y and Yb contents, with high Sr/Y ratios, and by high Mg#. They have initial 87Sr/86Sr of 0.7084-0.7087, ɛNd (T) of -8.8 to -9.0 and ɛHf (T) (in-situ zircon) of -11.2. Detailed elemental and isotopic data suggest that the Tangquan adakitic granodiorite was formed by partial melting of Paleoproterozoic metamorphic basement at a depth of ~40 km ( P ~12.5 kbar) plus additional input from coeval basaltic magma. The Xiadao pluton consists of monzogranite, syenogranite and alkali-feldspar granite. These granites are high-K calc-alkaline and belong to I-type. They have relatively low Sr and high Y and Yb contents and show similar Mg# to pure crustal melts. The Xiadao granites have slightly higher initial 87Sr/86Sr (0.7095-0.7102) and lower ɛNd (T) (-9.0 to -9.4) and ɛHf (T) (-14.4; in-situ zircon) than the Tangquan granitoids. Detailed elemental and isotopic data suggest that the Xiadao I-type granites were formed by partial melting of Paleoproterozoic metamorphic basement at a depth of ~30 km ( P ~10 kbar).

  1. Shoshonite and sub-alkaline magmas from an ultrapotassic volcano: Sr-Nd-Pb isotope data on the Roccamonfina volcanic rocks, Roman Magmatic Province, Southern Italy

    NASA Astrophysics Data System (ADS)

    Conticelli, Sandro; Marchionni, Sara; Rosa, Davide; Giordano, Guido; Boari, Elena; Avanzinelli, Riccardo

    2009-01-01

    The Roccamonfina volcano is characterised by two stages of volcanic activity that are separated by volcano-tectonic caldera collapses. Ultrapotassic leucite-bearing rocks are confined to the pre-caldera stage and display geochemical characteristics similar to those of other volcanoes in the Roman Province. After the major sector collapse of the volcano, occurred at ca. 400 ka, shoshonitic rocks erupted from cinder cones and domes both within the caldera and on the external flanks of the pre-caldera Roccamonfina volcano. On the basis of new trace element and Sr-Nd-Pb isotope data, we show that the Roccamonfina shoshonitic rocks are distinct from shoshonites of the Northern Roman Province, but are very similar to those of the Neapolitan volcanoes. The last phases of volcanic activity erupted sub-alkaline magmas as enclaves in trachytic domes, and as lavas within the Monte Santa Croce dome. Ultrapotassic rocks of the pre-caldera composite volcano are plagioclase-bearing leucitites characterised by high levels of incompatible trace elements with an orogenic signature having troughs at Ba, Ta, Nb, and Ti, and peaks at Cs, K, Th, U, and Pb. Initial values of 87Sr/86Sr range from 0.70926 to 0.70999, 143Nd/144Nd ranges from 0.51213 to 0.51217, while the lead isotope rations vary between 18.788-18.851 for 206Pb/204Pb, 15.685-15.701 for 207Pb/204Pb, and 39.048-39.076 for 208Pb/204Pb. Shoshonites show a similar pattern of trace element depletions and enrichments to the earlier ultrapotassic leucite-bearing rocks but have a larger degree of differentiation and lower concentrations of incompatible trace elements. On the other hand, shoshonitic rocks have Sr, Nd, and Pb isotopes consistently different than pre-caldera ultrapotassic leucite-bearing rocks. 87Sr/86Sr ranges from 0.70665 to 0.70745, 143Nd/144Nd ranges from 0.51234 to 0.51238, 206Pb/204Pb ranges from 18.924 to 19.153, 207Pb/204Pb ranges from 15.661 to 15.694, and 208Pb/204Pb ranges from 39.084 to 39.212. High-K calc

  2. 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.%.

  3. Trace element and Sr-Nd-Pb isotope geochemistry of Rungwe Volcanic Province, Tanzania: Implications for a superplume source for East Africa Rift magmatism

    NASA Astrophysics Data System (ADS)

    Castillo, Paterno; Hilton, David; Halldórsson, Sæmundur

    2014-09-01

    The recently discovered high, plume-like 3He/4He ratios at Rungwe Volcanic Province (RVP) in southern Tanzania, similar to those at the Main Ethiopian Rift in Ethiopia, strongly suggest that magmatism associated with continental rifting along the entire East African Rift System (EARS) has a deep mantle contribution (Hilton et al., 2011). New trace element and Sr-Nd-Pb isotopic data for high 3He/4He lavas and tephras from RVP can be explained by binary mixing relationships involving Early Proterozoic (+/- Archaean) lithospheric mantle, present beneath the southern EARS, and a volatile-rich carbonatitic plume with a limited range of compositions and best represented by recent Nyiragongo lavas from the Virunga Volcanic Province also in the Western Rift. Other lavas from the Western Rift and from the southern Kenya Rift can also be explained through mixing between the same endmember components. In contrast, lavas from the northern Kenya and Main Ethiopian rifts can be explained through variable mixing between the same mantle plume material and the Middle to Late Proterozoic lithospheric mantle, present beneath the northern EARS. Thus, we propose that the bulk of EARS magmatism is sourced from mixing among three endmember sources: Early Proterozoic (+/- Archaean) lithospheric mantle, Middle to Late Proterozoic lithospheric mantle and a volatile-rich carbonatitic plume with a limited range of compositions. We propose further that the African Superplume, a large, seismically anomalous feature originating in the lower mantle beneath southern Africa, influences magmatism throughout eastern Africa with magmatism at RVP and Main Ethiopian Rift representing two different heads of a single mantle plume source. This is consistent with a single mantle plume origin of the coupled He-Ne isotopic signatures of mantle-derived xenoliths and/or lavas from all segments of the EARS (Halldorsson et al., 2014).

  4. 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.

  5. 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

  6. Isotope (Sr, Nd, Pb, O) and trace-element geochemistry of volcanics from the Erta'Ale range (Ethiopia)

    NASA Astrophysics Data System (ADS)

    Barrat, J. A.; Fourcade, S.; Jahn, B. M.; Cheminée, J. L.; Capdevila, R.

    1998-01-01

    The Erta'Ale range is the most important axial volcanic chain of the Afar region. The petrographic diversity of lavas erupted in this area is very important, ranging from magnesian transitional basalts to rhyolites. The variation in isotopic compositions and incompatible element ratios in the basalts (e.g., ɛNd = +4.5 to +7.5, ( {La}/{Yb}) n = 2.5 to 11) demonstrates the heterogeneous character for their mantle sources. Such heterogeneity can be interpreted by the participation of two mantle reservoirs: a depleted MORB and a HIMU OIB-type sources. These reservoirs are indistinguishable from those recently identified in the southern part of the Red Sea region. The isotopic data indicate that the contribution of continental sialic components is not significant in the petrogenesis of the volcanic rocks. Our data further suggest that the crust beneath the Erta'Ale volcanic range is not a thinned (Pan-african?) sialic crust, but could be gabbroic in nature. The acid volcanics have originated mostly through fractional crystallisation of basaltic magmas as revealed from major- and trace-element data and from the relatively homogeneous Sr and Nd isotopic ratios. However, the δ18O variation in the acid lavas suggests an important contribution from a low δ18O component in the petrogenesis of some low δ 18O acid lavas.

  7. Hawaiian double volcanic chain triggered by an episodic involvement of recycled material: Constraints from temporal Sr-Nd-Hf-Pb isotopic trend of the Loa-type volcanoes

    NASA Astrophysics Data System (ADS)

    Tanaka, Ryoji; Makishima, Akio; Nakamura, Eizo

    2008-01-01

    The two parallel loci of recent Hawaiian volcanoes, Kea and Loa, have been regarded as the best targets to interpret the chemical structure of an upwelling mantle plume derived from the lower mantle. Here we show that the Sr-Nd-Hf-Pb isotopic data of the shield-building lavas along the Loa locus form a systematic trend from the main shield stage of Koolau (> 2.9 Ma) to the active Loihi volcanoes. During the growth of the Koolau volcano, the dominant material in the melting region successively changed from the proposed KEA, DMK (depleted Makapuu), to EMK (enriched Makapuu) components. The proportion of EMK, dominated by a recycled mafic component, is typified by some Koolau Makapuu-stage and some Lanai lavas. Subsequently, the EMK component decreased and LOIHI component increased toward the Loihi lavas. The temporal coincidence between the episodically elevated magma production rate and the abrupt appearance of the typical Loa-type lavas that is restricted to the last 3 Myr should be linked to magma genesis. We suggest that the abrupt appearance of Loa-type magmatism should be attributed to the transient incorporation of the relatively dense recycled material and surrounding less degassed lower mantle material that accumulated near the core-mantle boundary into the upwelling plume. This episodic involvement could have been trigged by episodic thermal pulses and buoyancy increases in the plume. The continuous appearance of Kea-type lavas during the long history of Hawaiian-chain magmatism and the larger magma volume of Kea-type lavas relative to that of the Loa-type lavas in the last 3 Myr indicate that the Kea locus is closer to the thermal centre of the Hawaiian plume relative to that of the Loa locus.

  8. Zircon U-Pb age, geochemical, and Sr-Nd-Pb isotopic constraints on the origin of alkaline intrusions in eastern Shandong Province, China

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    Alkaline intrusions in the eastern Shandong Province consist of quartz monzonite and granite. U-Pb zircon ages, geochemical data, and Sr-Nd-Pb isotopic data for these rocks are reported in the present paper. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon analyses yielded consistent ages ranging from 114.3 ± 0.3 to 122.3 ± 0.4 Ma for six samples of the felsic rocks. The felsic rocks are characterised by a wide range of chemical compositions (SiO2 = 55.14-77.63 wt. %, MgO = 0.09-4.64 wt. %, Fe2O3 = 0.56-7.6 wt. %, CaO = 0.40-5.2 wt. %), light rare earth elements (LREEs) and large ion lithophile elements (LILEs) (i.e., Rb, Pb, U) enrichment, as well as significant rare earth elements (HREEs) and heavy field strength (HFSEs) (Nb, Ta, P and Ti) depletion, various and high (87Sr/86Sr) i ranging from 0.7066 to 0.7087, low ɛ Nd (t) values from -14.1 to -17.1, high neodymium model ages (TDM1 = 1.56-2.38Ga, TDM2 = 2.02-2.25Ga), 206Pb/204Pb = 17.12-17.16, 207Pb/204Pb = 15.44-15.51, and 208Pb/204Pb = 37.55-37.72. The results suggested that these rocks were derived from an enriched crustal source. In addition, the alkaline rocks also evolved as the result of the fractionation of potassium feldspar, plagioclase, +/- ilmenite or rutile and apatite. However, the alkaline rocks were not affected by crustal contamination. Moreover, the generation of the alkaline rocks can be attributed to the structural collapse of the Sulu organic belt due to various processes.

  9. 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.

  10. 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

  11. 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.

  12. Geochemical and Sr-Nd Isotopic Compositions of Cenozoic Granitoids in Western Anatolia (Turkey): Spatial and Temporal Evolution of Continental Magmatism and Extension in the Aegean Province

    NASA Astrophysics Data System (ADS)

    Altunkaynak, S.; Genc, C.; Dilek, Y.

    2008-12-01

    Western Anatolia (Turkey) is part of the Aegean extensional province, which is situated in an active collision zone between the African and Eurasian Plates. The Cenozoic magmatism in western Anatolia started after the collision of the Sakarya continent (SC) and Anatolide-Tauride continental blocks (ATP) in the late Paleocene. The collisional front is today marked by the Izmir-Ankara suture zone (IASZ), which includes late Cretaceous Tethyan ophiolites, melanges, and HP/LT blueschist assemblages. Comparison of the isotope geochemistry and the petrogenesis of different plutons on both sides of the IASZ provide important geochronological and geochemical constraints on the nature of the late Cenozoic magmatism associated with crustal extension in the Aegean province. Irrespective of the lithological make-up of the collided blocks, the Oligo-Miocene granitoids that were emplaced into the SB and ATP show similar major and trace element and Sr-Nd isotopic compositions, indicating common melt sources and evolutionary trends. These granitoids are mainly metaluminous, medium to high-K calc-alkaline rocks with their silica contents ranging from 57.0 wt.% to 72.2 wt.%. They display enrichment in LILE and strong negative anomalies in Nb, Ta, P, Ti, and Zr, and they have initial 87Sr/86Sr values of 0.705186 - 0.711437 and 143Nd/ 143Nd values of 0.512615-0.512266. These isotopic signatures and trace element characteristics are considered to reflect the composition of the magmas derived from a metasomatized lithospheric mantle beneath NW Anatolia and from the overlying mafic lower crust. This inferred melt source readily explains the I-type granitoid nature of most Cenozoic plutons in western Anatolia regardless of their temporal and spatial position. The heat and the basaltic material to induce this partial melting were provided by aesthenospheric upwelling caused by partial lithospheric delamination and/or convective thinning. Slab rollback of the Hellenic subduction zone may

  13. U-Pb zircon geochronology, geochemical and Sr-Nd-Hf isotopic compositions of the Early Indosinian Tongren Pluton in West Qinling: Petrogenesis and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Li, Xiaowei; Mo, Xuanxue; Huang, Xiongfei; Dong, Guochen; Yu, Xuehui; Luo, Mingfei; Liu, Yanbin

    2015-01-01

    The West Qinling Orogenic Belt (WQOB), an important part of the Qinling-Dabie-Sulu Orogen (Central Orogen), is essential to understand the prolonged evolution of the northeastern branch of the Paleo-Tethys in East Asia. Zircon LA-ICP-MS U-Pb age and Lu-Hf isotopes, bulk-rock major and trace element, and Sr-Nd isotope data for the granodiorite intrusion from the Tongren area, West Qinling are presented. LA-ICP-MS zircon U-Pb dating analyses from two samples constrain the time of crystallization of the granodiorite to ca. 241 Ma. Combined with newly published age data from other coeval intrusive rocks in West Qinling, it is concluded that an Early Indosinian magmatic event occurred in West Qinling. In-situ zircon Hf isotope data on the two samples dated exhibit εHf(t) values of -0.6 to -5.8 and -0.8 to -3.9, with corresponding TDMC ages of 1312 to 1637 Ma and 1321 to 1516 Ma, respectively. Granodiorites are characterized by relatively high Mg# values (51.4-58.0), intermediate SiO2 (63.75-67.04 wt.%), high Al2O3 (14.24-15.58 wt.%) and total alkalies (6.60-8.00 wt.%) and relatively low A/CNK values (0.93-1.10). Granodiorites have I-type, high-K to shoshonitic, and metaluminous to weakly peraluminous character, showing bulk-rock geochemical features of arc-related granitoids. They are enriched in large-ion lithophile and light rare-earth elements, and depleted in some high-field-strength elements. The rocks show uniformly high (87Sr/86Sr)t (0.707616-0.708237) and low εNd(t) values (-7.9 to -7.5). Estimated crystallization temperatures for the rocks range from 720 ± 48 °C (Ti-in-zircon thermometer) to 759 ± 25 °C (zircon saturation thermometer). The data suggest that magmas were generated by dehydration melting of a mafic lower crustal component with additional input of a mafic component derived from the subcontinental lithospheric mantle. We conclude that the Tongren granodiorite formed in a subduction-related regime in response to slab roll-back of the northward

  14. 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

  15. 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.

  16. Sr-Nd isotope geochemistry and petrogenesis of the Chah-Shaljami granitoids (Lut Block, Eastern Iran)

    NASA Astrophysics Data System (ADS)

    Arjmandzadeh, R.; Karimpour, M. H.; Mazaheri, S. A.; Santos, J. F.; Medina, J. M.; Homam, S. M.

    2011-05-01

    Chah-Shaljami porphyritic granitoids belong to the Lut Block volcanic-plutonic belt of central eastern Iran. These intrusive rocks are mostly quartz monzonites, granodiorites and diorites. Geochemical evidence reveals that they are co-genetic and that they have features typical of high-K calc-alkaline to shoshonitic rocks from volcanic arc setting. Primitive mantle-normalized trace element spider diagrams display strong enrichment in LILE, such as Rb, Ba, and Cs, and depletion in some HFSE, e.g. Nb, Ti, Y and HREE. Chondrite-normalized plots show a very marked REE fractionation, with significant LREE enrichment (23 ⩾ La N/Yb N ⩾ 14) and the lack of Eu anomaly. Sr/Y and La/Yb ratios of Chah-shaljami intrusives are respectively 20-67 and 21-34, which reveals that, despite their K-rich composition, these rocks also, have some adakitic affinity. Plots on the Sr/Y-Y and La/Yb-Yb diagrams show that the Chah-Shaljami intrusives may be subdivided into two distinct classes. A Rb-Sr age of 33.5 ± 1 Ma, mainly dependent on the Sr isotopic composition of biotite, was obtained in a quartz monzonite sample. Taking into account that this sample was almost unaffected by hydrothermal and meteoric alteration and that cooling was probably fast, the 33-34 Ma date is interpreted as the intrusion age. With the exception of two samples, initial 87Sr/ 86Sr ratios and C̵Nd values are clustered in the restricted ranges of 0.70470-0.70506 and +1.9-+2.7, which fits into a supra-subduction mantle wedge source for the parental melts and indicates that, in general, crustal contribution for magma diversification was not relevant; however, one sample shows higher 87Sr/ 86Sr and lower C̵Nd, revealing that, occasionally, crustal rock assimilation also contributed to geochemical variation; one other sample, strongly affected by hydrothermal alteration, departs from the main group only by higher 87Sr/ 86Sr, suggesting that its alteration involved crustal fluids. Sr and Nd isotope compositions

  17. 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

  18. Sr, Nd, Hf and Pb isotope systematics of basaltic samples from IODP Site U1349A, Ori Massif of the Shatsky Rise Oceanic Plateau, Northwest Pacific

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Shatsky Rise is located on the northwest Pacific plate, and has an elongated structure from southeast to northwest. It represents a large oceanic plateau (up to 500 km wide) that was formed between 140-150 Ma in an active spreading ridge at relatively high emplacement rates (1.2-4.6 km3/y), similar to those of some flood basalt provinces [1]. Whether the Shatsky Rise formed by the impact of a mantle plume head or by shallow mantle processes at a rapidly extending triple junction is a matter of ongoing debate. Geochemical research will provide vital information on mantle sources and melting conditions contributing to LIP magmatism [1]. The Ori Massif is one of the three elevated massifs within the Shatsky Rise, comprising a volume of 0.7 × 106 km3. It is situated in the middle of the plateau with the largest edifice Tamu Massif to the southeast and the smaller Shirshov Massif to the northwest. Within plume theory Ori Massif formed at an intermediate to early stage of a plume volcanism. In shallow mantle theory it formed from a shallow lithospheric source during oceanic spreading at a triple junction [1]. During IODP Expedition 324 two sites were drilled on Ori Massif, one of which, U1349A, targeted the summit. The Hole U1349A penetrated 250.4m beneath the seafloor, and includes 165.1m of sediments and 85.3m of igneous basement. The uppermost volcanic flows (~55m) are highly vesicular, stongly altered to reddish brown clays and contain abundant pseudomorphs after olivine. These flows are underlain by highly altered volcaniclastic breccia (>40m) [1]. Here we present Sr, Nd, Hf and Pb isotope characterisation of the U1349A basaltic basement samples. Our results on the Ori Massif will be combined with isotope data from the Tamu Massif and Shirshov Massif. Thus, some preliminary conclusions about the source of mantle material that formed the Shatsky Rise oceanic plateau and its variation in space and time can be made. [1] Expedition 324 Scientists (2010) Expedition

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Geochemical and B-Sr-Nd isotopic evidence for mingling and mixing processes in the magmatic system that fed the Astroni volcano (4.1-3.8 ka) within the Campi Flegrei caldera (southern Italy)

    NASA Astrophysics Data System (ADS)

    Tonarini, Sonia; D'Antonio, Massimo; Di Vito, Mauro Antonio; Orsi, Giovanni; Carandente, Antonio

    2009-02-01

    The Astroni volcano was built through seven eruptions that generated pyroclastic deposits and lava domes within the Campi Flegrei caldera (southern Italy) 4.1-3.8 ka BP. Whole-rock geochemical and B-Sr-Nd isotopic investigations were carried out on representative samples of all seven eruptions. The products vary from tephriphonolites to phonolites, and from latites to trachytes. They show textural, mineralogical and isotopic evidence of disequilibrium, including distinct clinopyroxene populations, rounded and/or resorbed plagioclase and alkali-feldspar, and reverse-zoned phenocrysts of all these mineral phases. The Sr, Nd and B isotopic composition of whole rocks is variable and correlated with the degree of chemical evolution, suggesting open-system processes in addition to fractional crystallisation. Moreover, significant Sr-isotopic disequilibrium between the phenocrysts and glass has been documented for one sample. The chemostratigraphy of the products indicates that Astroni eruptions 1 through 5 were fed by magmas of trachytic to phonolitic composition that were less enriched in radiogenic Sr and 11B up-section. This variability has been interpreted as the result of mingling between at least two distinct magmatic end-members, one more evolved and the other less evolved. Another heterogeneous batch of magma, resulting from almost complete mixing between the same two end-members, was drained during eruptions 6 and 7. The more evolved end-member, characterised by 87Sr/ 86Sr ≥ 0.7075, 143Nd/ 144Nd ≤ 0.51247 and δ11B ≥ - 8‰, was very similar to the magma that fed the final phases of the Agnano-Monte Spina eruption, which occurred a few centuries earlier in the Astroni vent area. The less evolved end-member had 87Sr/ 86Sr ≤ 0.70726, 143Nd/ 144Nd ≥ 0.51251 and δ11B ≤ 10‰, and was likely derived by fractional crystallisation of a mantle-derived magma. An abrupt decrease in both the Sr isotope ratio and the Th content, detected at the transition

  4. U-Pb zircon dating, geochemical and Sr-Nd-Hf isotopic compositions of mafic intrusive rocks in the Motuo, SE Tibet constrain on their petrogenesis and tectonic implication

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Mafic intrusive rocks are widely exposed in the Motuo tectono-magmatic belt, southeast Lhasa terrane. LA-ICP-MS U-Pb zircon dating shows that they have magma crystallization ages of 69 and ca. 50 Ma. These mafic intrusive rocks are characterized by variable SiO2 (44.60-57.60 wt.%), high Al2O3 (17.19-20.86 wt.%), and low MgO (1.85-5.38 wt.%) with Mg# of 31-55. Their chemical composition is comparable with low-MgO high-Al basalts to basaltic andesites. They are enriched in LILEs (Rb, Ba, K) and LREE and depleted in HFSEs (Nb, Ta, Zr, Hf, Ti), with weakly evolved Sr-Nd-Hf compositions (whole-rock (87Sr/86Sr)0 = 0.7064 to 0.7086, εNd(t) = - 3.41 to + 1.22, and zircon εHf(t) = - 3.8 to + 6.4). The mafic rocks were derived from partial melting of metasomatized lithospheric mantle. Geochemical and Sr-Nd-Hf isotopic data show that they were insignificantly modified during magma emplacement. We provide a different secular evolution of the lithospheric mantle beneath the eastern part relative to the central part of the southern Lhasa terrane. Sr-Nd isotopic composition of the Motuo Late Cretaceous-Eocene mafic rocks argues that they were derived from partial melting of a relatively homogeneous and depleted lithospheric mantle. We propose that the Late Cretaceous delamination resulted in the replacement of ancient lithospheric mantle by the juvenile homogeneous lithospheric mantle in the eastern Lhasa terrane. The foundered ancient materials may subsequently re-fertilize the lithospheric mantle not only in the eastern Lhasa terrane but also in the surrounding areas.

  5. 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

  6. 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

  7. The petrogenesis of the Mesozoic volcanic rock in Xi-Ujimqin, NE China and the contributions from Ancient micro-continents: constraints from the zircon U-Pb dating and Sr-Nd-Pb isotopic systematics

    NASA Astrophysics Data System (ADS)

    Gao, X.; Xiao, P.; Kang, L.

    2013-12-01

    .Comprehensive geochemical investigations on the Mesozoic volcanic rocks from Xi-Ujimqin areas, the Hinggan Mountain reveal that the mantle sources for these rocks are of attributes of old continent blocks, while the mantle sources for the coeval volcanic rocks from other area show juvenile features. Trace elements and Sr, Nd, and Pb isotopic features imply that the mantle sources for these volcanic fields were inherited from enriched lithospheric mantle beneath old blocks with overprint of subducted juvenile island arc materials. This study provides solid deep geochemical constraints on the existence of Precambrian blocks among the Paleozoic Xingmeng orogen. During the Mesozoic, with the closure of the Mongo-Okhotsk and Mesozoic global event, regional extensional geological setting developed in these regions, which trigged decompressional melting of the lithospheric mantle and caused the voluminous eruption of volcanic rocks.

  8. 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

  9. 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

  10. Magma mixing origin for the post-collisional adakitic monzogranite of the Triassic Yangba pluton, Northwestern margin of the South China block: geochemistry, Sr-Nd isotopic, zircon U-Pb dating and Hf isotopic evidences

    NASA Astrophysics Data System (ADS)

    Qin, Jiang-Feng; Lai, Shao-Cong; Diwu, Chun-Rong; Ju, Yin-Juan; Li, Yong-Fei

    2010-03-01

    Petrogenesis of high Mg# adakitic rocks in intracontinental settings is still a matter of debate. This paper reports major and trace element, whole-rock Sr-Nd isotope, zircon U-Pb and Hf isotope data for a suite of adakitic monzogranite and its mafic microgranular enclaves (MMEs) at Yangba in the northwestern margin of the South China Block. These geochemical data suggest that magma mixing between felsic adakitic magma derived from thickened lower continental crust and mafic magma derived from subcontinental lithospheric mantle (SCLM) may account for the origin of high Mg# adakitic rocks in the intracontinental setting. The host monzogranite and MMEs from the Yangba pluton have zircon U-Pb ages of 207 ± 2 and 208 ± 2 Ma, respectively. The MMEs show igneous textures and contain abundant acicular apatite that suggests quenching process. Their trace element and evolved Sr-Nd isotopic compositions [(87Sr/86Sr)i = 0.707069-0.707138, and ɛNd( t) = -6.5] indicate an origin from SCLM. Some zircon grains from the MMEs have positive ɛHf( t) values of 2.3-8.2 with single-stage Hf model ages of 531-764 Ma. Thus, the MMEs would be derived from partial melts of the Neoproterozoic SCLM that formed during rift magmatism in response to breakup of supercontinent Rodinia, and experience subsequent fractional crystallization and magma mixing process. The host monzogranite exhibits typical geochemical characteristics of adakite, i.e., high La/Yb and Sr/Y ratios, low contents of Y (9.5-14.5 ppm) and Yb, no significant Eu anomalies (Eu/Eu* = 0.81-0.90), suggesting that garnet was stable in their source during partial melting. Its evolved Sr-Nd isotopic compositions [(87Sr/86Sr)i = 0.7041-0.7061, and ɛNd( t) = -3.1 to -4.3] and high contents of K2O (3.22-3.84%) and Th (13.7-19.0 ppm) clearly indicate an origin from the continental crust. In addition, its high Mg# (51-55), Cr and Ni contents may result from mixing with the SCLM-derived mafic magma. Most of the zircon grains from the

  11. 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

  12. 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

  13. 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

  14. 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.

  15. Multiple sources for the origin of Late Jurassic Linglong adakitic granite in the Shandong Peninsula, eastern China: Zircon U-Pb geochronological, geochemical and Sr-Nd-Hf isotopic evidence

    NASA Astrophysics Data System (ADS)

    Ma, Liang; Jiang, Shao-Yong; Dai, Bao-Zhang; Jiang, Yao-Hui; Hou, Ming-Lan; Pu, Wei; Xu, Bin

    2013-03-01

    The Linglong granite is one of the most important Mesozoic plutons in the Shandong Peninsula, eastern China, and its petrogenesis has long been controversial, particularly with regard to the nature of source region and geodynamic setting. Our new precise zircon U-Pb dating results reveal that the Linglong granite was emplaced in the Late Jurassic (157-160 Ma). In addition, abundant inherited zircons are identified in the granite with four groups of age peaked at ~ 208, ~ 750, ~ 1800 and ~ 2450 Ma. Geochemical studies indicate that the Linglong granite is weakly peraluminous I-type granite, and is characterized by high SiO2, Sr and La, but low MgO, Y and Yb contents, strongly fractionated REE pattern and high Sr/Y and La/Yb ratios. It also exhibits high initial 87Sr/86Sr ratios (0.7097 to 0.7125), low ɛNd(t) (- 17.7 to - 20.3) and variable zircon ɛHf(t) (- 22.2 to - 8.7) values. Calculation of the zircon saturation temperature (TZr) reveals that the magma temperatures are 760 ± 20 °C, and the lowest TZr value of 740 °C may be close to initial magma temperature of this inheritance-rich rock. Interpretation of the elemental and isotopic data suggests that the Linglong granite has some affinities with the adakite, and was most likely derived from partial melting of thickened lower crust without any significant contribution of mantle components. The presence of a large number of inherited zircons and variable Sr-Nd-Hf isotopic compositions reveal that the Linglong granite probably has multiple sources consisting of the lower crust of both South China Block and North China Block, as well as the collision-related alkaline rocks and UHP metamorphic rocks. The continental arc-rifting related to the Izanagi plate subduction was the most likely geodynamic force for formation of the Jurassic Linglong adakatic granite in the Shandong Peninsula.

  16. 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

  17. 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

  18. 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).

  19. 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.

  20. 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.

  1. 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.

  2. Zircon U-Pb geochronology and Sr-Nd-Pb-Hf isotopic constraints on the timing and origin of Mesozoic granitoids hosting the Mo deposits in northern Xilamulun district, NE China

    NASA Astrophysics Data System (ADS)

    Shu, Qihai; Lai, Yong; Zhou, Yitao; Xu, Jiajia; Wu, Huaying

    2015-12-01

    Located in the east section of the Central Asian orogen in northeastern China, the Xilamulun district comprises several newly discovered molybdenum deposits, primarily of porphyry type and Mesozoic ages. This district is divided by the Xilamulun fault into the southern and the northern parts. In this paper, we present new zircon U-Pb dating, trace elements and Hf isotope, and/or whole rock Sr-Nd-Pb isotopic results for the host granitoids from three Mo deposits (Yangchang, Haisugou and Shabutai) in northern Xilamulun. Our aim is to constrain the age and petrogenesis of these intrusions and their implications for Mo mineralization. Zircon U-Pb LA-ICP-MS dating shows that the monzogranites from the Shabutai and Yangchang deposits formed at 138.4 ± 1.5 and 137.4 ± 2.1 Ma, respectively, which is identical to the molybdenite Re-Os ages and coeval well with the other Mo deposits in this region, thereby indicating an Early Cretaceous magmatism and Mo mineralization event. Zircon Ce/Nd ratios from the mineralized intrusions are significantly higher than the barren granites, implying that the mineralization-related magmas are characterized by higher oxygen fugacity. These mineralized intrusions share similar zircon in-situ Hf and whole rock Sr-Nd isotopic compositions, with slightly negative to positive εHf(t) ranging from - 0.8 to + 10.0, restricted εNd(t) values from - 3.7 to + 1.6 but a little variable (87Sr/86Sr)i ratios between 0.7021 and 0.7074, indicative of formation from primary magmas generated from a dominantly juvenile lower crust source derived from depleted mantle, despite diverse consequent processes (e.g., magma mixing, fractional crystallization and crustal contamination) during their evolution. The Pb isotopes (whole rock) also show a narrow range of initial compositions, with (206Pb/204Pb)i = 18.03-18.88, (207Pb/204Pb)i = 15.48-15.58 and (208Pb/204Pb)i = 37.72-38.28, in agreement with Sr-Nd-Hf isotopes reflecting the dominance of a mantle component

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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

  10. 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).

  11. 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

  12. 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

    2015-12-01

    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.

  13. 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.

  14. 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

  15. Petrogenesis of Tarom high-potassic granitoids in the Alborz-Azarbaijan belt, Iran: Geochemical, U-Pb zircon and Sr-Nd-Pb isotopic constraints

    NASA Astrophysics Data System (ADS)

    Nabatian, Ghasem; Ghaderi, Majid; Neubauer, Franz; Honarmand, Maryam; Liu, Xiaoming; Dong, Yunpeng; Jiang, Shao-Yong; von Quadt, Albrecht; Bernroider, Manfred

    2014-01-01

    Large-scale Upper Eocene plutons in the Western Alborz-Azarbaijan orogenic belt mostly show calc-alkaline and I-type geochemical features contrasted by the Tarom complex with its high-potassic to shoshonitic affinity. The pluton was emplaced in the Tarom subzone of the orogenic belt and its laser ICP-MS zircon U-Pb age of 41 Ma is interpreted as the age of magma crystallization. The Tarom complex is composed of quartz monzodiorite, quartz-monzonite and monzogranite, the SiO2 contents range from 57 to 70 wt.%, the K2O + Na2O content is high (5.0-8.9 wt.%) and K2O/Na2O ratio ranges from 0.4 to 1.9. All the investigated rocks are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs), and bear a weak Eu anomaly (Eu/Eu* = 0.46 to 1.38) in chondrite-normalized trace element patterns. The samples display some variety in initial Sr and Nd isotopic compositions, marked with low ISr = 0.704-0.705 and ɛNd (40 Ma) = - 4.2 to + 3.4 (- 5.7 for an enclave) values. The Pb isotopic ratios are (206Pb/204Pb) = 18.52-18.86, (207Pb/204Pb) = 15.57-15.72 and (208Pb/204Pb) = 38.47-39.08. Comparison with experimental studies, together with mantle-like isotopic ratios and comparisons of REE patterns, points to an origin of chemically enriched lithospheric mantle source for the Tarom plutonic complex. Partial melting process involving different partial melting degrees affecting heterogeneously metasomatized mantle is a process that seems likely to have occurred in the studied complex as the major differentiation process. The Tarom monzonitic plutons are considered to be post-orogenic intrusions that were emplaced in an environment of lithospheric extension, causing asthenospheric upwelling. Asthenospheric upwelling induced a thermal anomaly which caused partial melting of metasomatized subcontinental lithospheric mantle in the Tarom area.

  16. Sr-Nd-Pb Isotopic Compositions of Volcanic Rocks Associated to the Apan-Tlaloc Fault System, Trans-Mexican Volcanic Belt, Mexico

    NASA Astrophysics Data System (ADS)

    Solis-Pichardo, G.; Martinez-Serrano, R.; Garcia, G.; Correa, J.; Nuñez, Y.; Schaaf, P. E.

    2010-12-01

    The Apan-Tlaloc region is located in the east-central part of the Trans-Mexican Volcanic Belt (TMVB), north of Popocatepetl volcano. It is composed of different volcanic structures: domes, cinder cones, shield volcanoes with major lava flows, and pyroclastic deposits. Geological studies have shown that these structures are probably related to the presence of a NE-SW oriented normal fault system. In this study, the Apan volcanic rocks were grouped into a Basal Volcanic Unit (~13.4 to 12.6 Ma) and an Upper Volcanic Unit (~2.1 to 1.5 Ma). Basal Unit products have compositions ranging from andesites to porphyric dacites and rhyolitic ignimbrites derived from volcanic sources unrelated to the NE-SW faulting. Basalts and basaltic andesites are representative of the Upper Unit. According to age determinations and stratigraphic studies, the magmatism in the Apan region was not continuous through the Miocene to the Pliocene, an approx 10 Ma hiatus is observed between both units. All studied rocks are of a calc-alkaline nature but differ substantially in their SiO2 contents: more than 65 wt.% in the Basal Unit and less than 57 wt.% in the Upper Unit. Trace element patterns are relatively heterogeneous for both units. Basal Unit volcanics show LILE enrichments with respect to HFSE as well as negative anomalies of Nb, Ta, P, and Ti, and positive anomalies of Ba, Rb, and Pb, suggesting a depleted mantle source origin modified by subduction fluids. In contrast, Upper Unit volcanics do not show enrichment of LILE with respect to HFSE and negative Nb and Ta anomalies are absent. Negative P and Ti anomalies and positive Ba and Pb spikes are also observed. These patterns suggest a less depleted mantle source, which was also affected by fluids derived from subduction processes. REE patterns for both units show enrichment of LREE with respect to HREE, confirming a magma origin related to a subducted slab but from a different source. The isotopic results for all products show the

  17. Isotope systematics of Li, Sr, Nd, and volatiles in Indian Ocean MORBs of the Rodrigues Triple Junction: Constraints on the origin of the DUPAL anomaly

    NASA Astrophysics Data System (ADS)

    Nishio, Yoshiro; Nakai, Shun'ichi; Ishii, Teruaki; Sano, Yuji

    2007-02-01

    The DUPAL anomaly, a radiogenic isotope anomaly discovered in the Indian Ocean mantle, has been interpreted as due to a large-scale mantle heterogeneity. To provide new constraints on the DUPAL origin, we analyzed isotope ratios of Li, Sr, and Nd in fresh N-MORB glasses recovered from the Rodrigues Triple Junction in the Indian Ocean, and from the North Atlantic. The Li isotopic compositions of the Indian Ocean DUPAL N-MORBs were comparable to those of the North Atlantic non-DUPAL N-MORBs. The source of the DUPAL signature in Indian Ocean MORBs and the E-MORB-type enriched mantle source have quite different Li isotopic compositions. The 143Nd/ 144Nd values of both sources are significantly lower than those of the North Atlantic N-MORBs. The δ 7Li values of most oceanic island basalts with similar low 143Nd/ 144Nd signatures are also higher than those of the North Atlantic N-MORBs, except for several Koolau lavas. The Li isotope results support the recent proposal that significant amounts of recycled lower continental crust might produce the radiogenic isotope signatures of the Indian Ocean DUPAL source.

  18. 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.

  19. Contrasted crustal sources as defined by whole-rock and Sr-Nd-Pb isotope geochemistry of neoproterozoic early post-collisional granitic magmatism within the Southern Brazilian Shear Belt, Camboriú, Brazil

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    The early phase of post-collisional granitic magmatism in the Camboriú region, south Brazil, is represented by the porphyritic biotite ± hornblende Rio Pequeno Granite (RPG; 630-620 Ma) and the younger (˜610 Ma), equigranular, biotite ± muscovite Serra dos Macacos Granite (SMG). The two granite types share some geochemical characteristics, but the more felsic SMG constitutes a distinctive group not related to RPG by simple fractionation processes, as indicated by its lower FeOt, TiO2, K2O/Na2O and higher Zr Al2O3, Na2O, Ba and Sr when compared to RPG of similar SiO2 range. Sr-Nd-Pb isotopes require different sources. The SMG derives from old crustal sources, possibly related to the Paleoproterozoic protoliths of the Camboriú Complex, as indicated by strongly negative ɛNdt (-23 to -24) and unradiogenic Pb (e.g., 206Pb/204Pb = 16.0-16.3; 207Pb/204Pb = 15.3-15.4) and confirmed by previous LA-MC-ICPMS data showing dominant zircon inheritance of Archean to Paleoproterozoic age. In contrast, the RPG shows less negative ɛNdt (-12 to -15) and a distinctive zircon inheritance pattern with no traces of post-1.6 Ga sources. This is indicative of younger sources whose significance in the regional context is still unclear; some contribution of mantle-derived magmas is indicated by coeval mafic dykes and may account for some of the geochemical and isotopic characteristics of the least differentiated varieties of the RPG. The transcurrent tectonics seems to have played an essential role in the generation of mantle-derived magmas despite their emplacement within a low-strain zone. It may have facilitated their interaction with crustal melts which seem to be to a large extent the products of reworking of Paleoproterozoic orthogneisses from the Camboriú Complex.

  20. 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.

  1. 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.

  2. Geochemical and Sr-Nd isotope evidences of the suprasubduction nature of mesozoic magmatism in the Mongol-Okhotsk Sector of the Pacific Fold Belt

    NASA Astrophysics Data System (ADS)

    Derbeko, I. M.; Chugaev, A. V.; Oleinikova, T. I.; Bortnikov, N. S.

    2016-02-01

    In this article we present geochemical and isotope characteristics of rocks of the Unerikan, Selitkan and Aezop-Yamalin volcano-plutonic zones of the eastern termination of the Mongol-Okhotsk Orogenic Belt. The obtained data demonstrate that the Mesozoic igneous rocks of the Mongol-Okhotsk sector of the Pacific Folded Belt were formed due to the melting of the continental crust in a tectonic setting corresponding to a suprasubduction one.

  3. Geochemical, zircon U-Pb dating and Sr-Nd-Hf isotopic constraints on the age and petrogenesis of an Early Cretaceous volcanic-intrusive complex at Xiangshan, Southeast China

    NASA Astrophysics Data System (ADS)

    Yang, Shui-Yuan; Jiang, Shao-Yong; Jiang, Yao-Hui; Zhao, Kui-Dong; Fan, Hong-Hai

    2011-01-01

    The Late Mesozoic geology of Southeast China is characterized by extensive Jurassic to Cretaceous magmatism consisting predominantly of granites and rhyolites and subordinate mafic rocks, forming a belt of volcanic-intrusive complexes. The Xiangshan volcanic-intrusive complex is located in the NW region of the belt and mainly contains the following lithologies: rhyodacite and rhyodacitic porphyry, porphyritic lava, granite porphyry with mafic microgranular enclaves, quartz monzonitic porphyry, and lamprophyre dyke. Major and trace-element compositions, zircon U-Pb dating, and Sr-Nd-Hf isotopic compositions have been investigated for these rocks. The precise SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the emplacement of various magmatic units at Xiangshan took place within a short time period of less than 2 Myrs. The stratigraphically oldest rhyodacite yielded a zircon U-Pb age of 135 ± 1 Ma and the overlying rhyodacitic porphyry has an age of 135 ± 1 Ma. Three porphyritic lava samples yielded zircon U-Pb ages of 136 ± 1 Ma, 132 ± 1 Ma, and 135 ± 1 Ma, respectively. Two subvolcanic rocks (granite porphyry) yielded zircon U-Pb ages of 137 ± 1 Ma and 137 ± 1 Ma. A quartz monzonitic porphyry dyke, which represented the final stage of magmatism at Xiangshan, also yielded a zircon U-Pb age of 136 ± 1 Ma. All these newly obtained precise U-Pb ages demonstrate that the entire magmatic activity at Xiangshan was rapid and possibly took place at the peak of extensional tectonics in SE China. The geochemical data indicate that all these samples from the volcanic-intrusive complex have an A-type affinity. Sr-Nd-Hf isotopic data suggest that the Xiangshan volcanic-intrusive complex derived mainly from remelting of Paleo-Mesoproterozoic crust without significant additions of mantle-derived magma. However, the quartz monzonitic porphyry, which has zircon Hf model ages older than the whole-rock Nd model ages, and which has ɛNd(T) value higher than the other rocks

  4. 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

  5. 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.

  6. 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

  7. Sr-Nd isotope geochemistry and tectonomagmatic setting of the Dehsalm Cu-Mo porphyry mineralizing intrusives from Lut Block, eastern Iran

    NASA Astrophysics Data System (ADS)

    Arjmandzadeh, R.; Santos, J. F.

    2014-01-01

    The Dehsalm Cu-Mo-bearing porphyritic granitoids belong to the Lut Block volcanic-plutonic belt (central eastern Iran). These rocks range in composition from gabbro-diorite to granite, with dominance of monzonites and quartz monzonites, and have geochemical features of high-K calc-alkaline to shoshonitic volcanic arc suites. Primitive mantle-normalized trace element spider diagrams display strong enrichment in large-ion lithophile elements such as Rb, Ba and Cs and depletions in some high-field strength elements, e.g., Nb, Ti, Y and HREE. Chondrite-normalized plots display significant LREE enrichments, high LaN/YbN and a lack of Eu anomaly. High Sr/Y and La/Yb ratios of Dehsalm intrusives reveal that, despite their K-rich composition, these granitoids show some resemblances with adakitic rocks. A Rb-Sr whole rock-feldspar-biotite age of 33 ± 1 Ma was obtained in a quartz monzonite sample and coincides, within error, with a previous geochronological result in Chah-Shaljami granitoids, further northwest within the Lut Block. (87Sr/86Sr)i and ɛNdi isotopic ratios range from 0.70481 to 0.70508 and from +1.5 to +2.5, respectively, which fits into a supra-subduction mantle wedge source for the parental melts and indicates that crustal contribution for magma diversification was of limited importance. Sr and Nd isotopic compositions together with major and trace element geochemistry point to an origin of the parental magmas by melting of a metasomatized mantle source, with phlogopite breakdown playing a significant role in the geochemical fingerprints of the parental magmas; small amounts of residual garnet in the mantle source also help to explain some trace element patterns. 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.

  8. Petrogenesis of late Paleozoic volcanic rocks from the Daheshen Formation in central Jilin Province, NE China, and its tectonic implications: Constraints from geochronology, geochemistry and Sr-Nd-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Yu, Qian; Ge, Wen-Chun; Yang, Hao; Zhao, Guo-Chun; Zhang, Yan-Long; Su, Li

    2014-04-01

    We present geochronological, geochemical, whole-rock Sr-Nd and zircon Hf-isotopic data for late Paleozoic volcanic rocks from the Daheshen Formation in central Jilin Province, northeastern China, and constrain the petrogenesis of the volcanic rocks and late Paleozoic tectonic evolution of the northern margin of the Northern China Craton, which is regarded as the eastern segment of the Central Asian Orogenic Belt (CAOB). Lithologically, the Daheshen Formation is composed mainly of rhyolite, rhyolitic tuff, dacite and andesite, with minor basalt. The zircons from three rhyolites, two dacites, one rhyolitic tuff and one basalt are euhedral-subhedral, display oscillatory zoning and have high Th/U ratios (0.50-2.28), implying a magmatic origin. LA-ICP-MS zircon U-Pb age data indicate that the volcanic rocks from the Daheshen Formation formed during Late Carboniferous-Early Permian time (302-299 Ma). Geochemically, late Paleozoic volcanic rocks have SiO2 = 52.13-81.77 wt.% and K2O = 0.86-6.88 wt.%, belonging to mid-K to high-K calc-alkaline series. These rocks are characterized by enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depletion in high field strength elements (HFSEs, such as Nb, Ta, and Ti) and heavy rare earth elements (HREEs), with affinities to igneous rocks forming in an active continental margin setting. All volcanic rocks have depleted Nd isotopic compositions (ɛNd(t) = + 2.4 to + 2.5 for the basalts and + 5.8 to + 7.1 for the andesites and dacites, respectively). In situ Hf isotopic results of zircon from the rhyolites show that they have ɛHf(t) = - 1.1 to + 10.6. All these geochemical features indicate that the andesites, dacites, and rhyolites likely originated from the partial melting of Meso-Neoproterozoic accreted lower crust (Hf and Nd model ages (TDM2) of 1384-662 Ma and 1061-800 Ma, respectively). In contrast, the basalts were derived from the partial fusion of a depleted lithospheric mantle that

  9. 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

    2016-03-01

    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).

  10. 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.

  11. Petrology and Sr-Nd-Pb-He isotope geochemistry of postspreading lavas on fossil spreading axes off Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Tian, Liyan; Castillo, Paterno R.; Lonsdale, Peter F.; Hahm, Doshik; Hilton, David R.

    2011-02-01

    Postspreading volcanism has built large seamounts and volcanic ridges along the short axes of a highly segmented part of the East Pacific Rise crest that ceased spreading at the end of the middle Miocene, offshore Baja California Sur, Mexico. Lava samples from Rosa Seamount, the largest volcano, are predominantly alkalic basalts, mugearites, and benmoreites. This lavas series was generated through fractional crystallization and is compositionally similar to the moderately alkalic lava series in many oceanic islands. Samples from volcanic ridges at three adjacent failed spreading axes include mildly alkalic, transitional, and tholeiitic basalts and differentiated trachyandesites and andesite. The subtle but distinct petrologic and isotopic differences among the four sites may be due to differences in the degree of partial melting of a common, heterogeneous source. Postspreading lavas from these four abandoned axes off Baja California Sur together with those from other fossil spreading axes and from seamount volcanoes that grew on the East Pacific Rise flanks define a compositional continuum ranging from normal mid-ocean ridge basalt (NMORB)-like to ocean island basalt (OIB)-like. We propose that the compositional spectrum of these intraplate volcanic lavas is due to different degrees of partial melting of the compositionally heterogeneous suboceanic mantle in the eastern Pacific. A large degree of partial melting of this heterogeneous mantle during vigorous mantle upwelling at an active spreading center produces NMORB melts, whereas a lesser degree of partial melting during weak mantle upwelling following cessation of spreading produces OIB-like melts. The latter melts have a low (<8 RA) 3He/4He signature indicating their formation is different from that of OIBs from major "hot spot" volcanoes in the Pacific with high 3He/4He ratios, such as Hawaii and Galapagos.

  12. Geochronology, geochemistry and Sr-Nd-Hf isotopes of mafic dikes in the Huicheng Basin: Constraints on intracontinental extension of the Qinling orogen

    NASA Astrophysics Data System (ADS)

    Li, Wei; Dong, Yunpeng; Guo, Anlin; Liu, Xiaoming; Wang, Yuejun; Liu, Wenhang; Yang, Yuanzhen

    2015-05-01

    The diabase dikes intruded the Lower Cretaceous sandstone in the Huicheng Basin are key to understanding the Mesozoic tectonic evolution of the Qinling orogen. LA-ICP-MS zircon U-Pb dating yields a crystallization age of 107 ± 1 Ma for them. The dikes have low contents of SiO2 (42.46-50.16 wt.%), MgO (3.47-5.59 wt.%) with low Mg# of 49-59, and TiO2 (1.35-1.63 wt.%), high TFe2O3 (8.15-9.36 wt.%), Al2O3 (14.75-17.23 wt.%) and K2O (0.87-3.61 wt.%). Their Ni and Cr contents are in range of 16.8-111 and 45.7-315 ppm, respectively. They are significantly enriched in light rare earth elements and large ion lithophile elements (e.g., Cs, Pb and Ba), and depleted in Rb, K, P, and Ti. The dikes show relatively high whole-rock initial 87Sr/86Sr ratios (0.7071-0.7079) and negative εNd (t) values (-1.5 to -4.8) with single-stage Nd model ages of 941-1186 Ma. In addition, they have low zircon εHf (t) values (-8.6 to +3.5) with single-stage Hf model ages of 674-1117 Ma. Both elemental and isotopic geochemistry suggests that the magma of these dikes has undergone significant crystallization fractionation of olivine and pyroxene but weak crustal contamination during magma evolution. They were derived from partial melting of an enriched lithospheric mantle source. Together with regional geological data, these results suggest that the Qinling orogen experienced an intracontinental extension during the late Early Cretaceous.

  13. 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

  14. Geochemical and Sr-Nd-Hf isotopic constraints on the origin of Late Triassic granitoids from the Qinling orogen, central China: Implications for a continental arc to continent-continent collision

    NASA Astrophysics Data System (ADS)

    Jiang, Yao-Hui; Jin, Guo-Dong; Liao, Shi-Yong; Zhou, Qing; Zhao, Peng

    2010-06-01

    The Qinling-Dabie-Sulu orogen marks the junction between the North and South China Blocks. However, the exact timing of the final coalescence of the North and South China Blocks in the Qinling orogen is poorly constrained. This paper presents new SHRIMP zircon U-Pb chronology, major and trace elements, and Sr-Nd-Hf isotope data for five early Mesozoic granitic plutons across the Qinling orogen. SHRIMP zircon U-Pb dating shows that four plutons were emplaced in the Carnian (227-218 Ma) of Late Triassic with a southward-younging trend and one pluton was emplaced in the Norian (˜ 211 Ma) of Late Triassic. The Carnian plutons consist of high-K calc-alkaline granitoids (quartz monzodiorite, quartz monzonite, granodiorite and monzogranite) and calc-alkaline diorite. These rocks are mainly metaluminous and are characterized by high Sr and low Y and Yb contents, with high Sr/Y and La/Yb ratios, and by high Mg#, higher than pure crustal melts. The Norian pluton is composed of high-K calc-alkaline two-mica granites, which are peraluminous. These granites have low Sr and high Y and Yb contents and show similar Mg# to pure crustal melts. Detailed elemental and isotopic data suggest that the Carnian plutons were emplaced in a continental arc setting coupled with the northward subduction of the Paleo-Tethyan oceanic crust. Partial melting of subducted sediments triggered by dehydration of the underlying igneous oceanic crust, with subsequent melts interacting with the overlying mantle wedge, formed the high-K calc-alkaline granitic magmas. Partial melting of the hybridized peridotitic mantle wedge induced by slab melts generated the calc-alkaline dioritic magma. The Norian pluton was emplaced during continental collision between the South Qinling terrane and South China Block, which marks the final integration of the North and South China Blocks. Partial melting of subducted sediments at a shallow depth (< 30 km) in the collision (overthrust) zone could account for the origin

  15. 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

  16. 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

  17. 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

  18. 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

  19. Petrogenesis and tectonic setting of Triassic granitoids in the Qiangtang terrane, central Tibet: Evidence from U-Pb ages, petrochemistry and Sr-Nd-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Li, Guang-Ming; Li, Jin-Xiang; Zhao, Jun-Xing; Qin, Ke-Zhang; Cao, Ming-Jian; Evans, Noreen J.

    2015-06-01

    Triassic granitoids, including the ∼220 Ma Shuanghu and ∼210 Ma Rongma granitoids studied here, are widely distributed around the Longmu-Shuanghu suture and in the Qiangtang terrane, central Tibet. The majority of these granitoids can be classified as high-K calc-alkaline in nature and yield negative Ba and Sr anomalies on primitive mantle-normalized diagrams. In addition, they are: enriched in light rare earth elements (LREE) ((La/Yb)N = 1.61-21.79); strongly enriched in large ion lithophile elements (LILE: e.g., Cs, Rb, and K), and depleted in high field strength elements (HFSE: e.g., Nb and Ti). Magma mixing played a role in the genesis of the Shuanghu granodiorites, as indicated by the occurrence of dioritic enclaves and the wide range in zircon Hf compositions (εHf(t) = -15.0 to -2.5). The I-type Shuanghu granodiorites and S-type Shuanghu and Rongma granites might have been derived from melting of southern Qiangtang crust given the high initial Sr (0.7131-0.7272), low εNd(t) (-8.9 to -11.1) and zircon εHf(t) values (-15 to -7.2). The granitoids may have formed during melting of southern Qiangtang crust, heated by upwelling asthenosphere mantle, a result of break-off and delamination of the Paleo-Tethys slab in a collisional setting.

  20. 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.

  1. 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.

  2. Early Paleozoic crust-mantle interaction and lithosphere delamination in South China Block: Evidence from geochronology, geochemistry, and Sr-Nd-Hf isotopes of granites

    NASA Astrophysics Data System (ADS)

    Xia, Yan; Xu, Xisheng; Zou, Haibo; Liu, Lei

    2014-01-01

    The early Paleozoic orogen in South China Block is an intracontinental orogen, and synchronous magmatism (440-390 Ma) is mainly acidic with minor intermediate-mafic magmatism. Previous studies suggest that most of the early Paleozoic granites in South China belong to peraluminous S-type genesis while amphibole-bearing I-type granites are subordinate. However, our results indicate that considerable amounts of these early Paleozoic granites have characteristics of both S- and I-type granites. Thus, we propose to divide these granites into two groups: fewer of them are Group A with relatively high ɛHf(t) values (clustering within - 3.0 to + 9.0) and ɛNd(t) values (- 5.2 to + 1.3) as well as higher initial temperatures at 810-850 °C, and most of them are Group B with relatively low ɛHf(t) values (clustering within - 16.0 to - 1.0) and ɛNd(t) values (- 13.2 to - 4.1) as well as relatively low initial temperatures at 700-830 °C. The Xiawan monzogranite and Duntou granodiorite are typical Group A granitoids and yield zircon U-Pb ages of ca. 410 Ma. These two granites are characterized by high SiO2 (between 67.59 and 74.87 wt.%), metaluminous to peraluminous (A/CNK = 0.96-1.48) compositions, and a negative correlation between P2O5 and SiO2. Their biotites belong to magnesium biotites, indicating that they have partial features of either I- or S-type granites. Duntou granodiorites exhibit higher ɛHf(t) values (clustering within + 1 to + 8) and ɛNd(t) values (- 3.0 to + 1.1) while Xiawan monzogranites show relatively low ɛHf(t) values (clustering within - 1 to + 5) and ɛNd(t) values (- 5.0 to - 3.7). Group B granitoids are represented by the Miao'ershan-Yuechengling batholith, which are characterized by high SiO2 (between 64.57 and 77.37 wt.%), metaluminous compositions (A/CNK = 0.90-1.24), and a negative correlation between P2O5 and SiO2. Yuechengling porphyritic amphibole-bearing biotite granites in this batholith contain abundant amphibole, indicating that they

  3. Zircon U-Pb age and Sr-Nd-Hf isotope geochemistry of Permian granodiorite and associated gabbro in the Songliao Block, NE China and implications for growth of juvenile crust

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    Post-orogenic granitic and associated mafic rocks from northeastern (NE) China consist of granodiorite and gabbro intrusions. We report here upon new U-Pb zircon ages, geochemical data and Sr-Nd-Hf isotopic data for these rocks. LA-ICP-MS U-Pb zircon analysis yields an age of 262.8 ± 1.0 Ma for the granitic rocks, and a uniform age of 262.1 ± 0.7 Ma for the gabbro. Most of the granitic and mafic rocks are characterised by low K 2O + Na 2O, and pertain to the subalkaline series in the total alkali-silica diagram. The granodiorite samples show low ( 87Sr/ 86Sr) i ranging from 0.700 to 0.705, positive ɛNd( t) values from +0.3 to +0.8, and large variation in ɛHf( t) values of between - 4.0 and +2.5, indicating that both newly underplated basalt (70-80%) and ancient lower crustal sources (20-30%) contributed to their origin. Furthermore, positive ɛHf( t) values with two-stage model ages ( TDM2) of 1123-1260 Ma, together with Nd model ages (960-1000 Ma), suggest an important episode of crustal growth during the Meso-Neoproterozoic beneath the Songliao Block. In contrast, the investigated gabbro is characterised by relatively high ( 87Sr/ 86Sr) i ratios (0.707-0.708), negative ɛNd( t) (- 5.9 to - 5.3) and ɛHf( t) values (- 5.0 to - 2.3), implying that this was derived from an enriched mantle source. The geochemical data indicate that the granitic magmas underwent separation of clinopyroxene, hornblende, K-feldspar, plagioclase, Ti-bearing phases (e.g., rutile, ilmenite, titanite), apatite and zircon during their evolution. Whereas the gabbro is characterised by low MgO (2.92-3.92 wt.%), Mg# (35-41) and compatible elements content, such as Cr (10-68 ppm), Co (16-31 ppm) and Ni (5.7-33 ppm), features of a more evolved mafic magma. There is no evidence that the granitic and mafic rocks were affected by crustal contamination during emplacement. Our interpretation is that the two coeval intrusive suites were both formed in a post-orogenic extensional setting, related to

  4. 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

  5. Small scale inhomogeneity in the mantle source of the Cape Verde hotspot is probably related to plume complexity: implications from Sr, Nd and high precision Pb isotopes and geochemistry

    NASA Astrophysics Data System (ADS)

    Holm, P. M.; Sørensen, R. V.

    2009-04-01

    The volcanic rocks of one of the major islands of the Cape Verde hotspot have been investigated in order to test mantle plume models. From the centre of the Cape Verde Rise an array of islands trend west, the northern HIMU-type Cape Verde Islands. Of these, São Nicolau (SN) is the easternmost and Santo Antão the westernmost. Sixty samples of primitive (MgO = 9-14 wt%) basanitic composition from SN that represent the four volcanic stages of the 9 - 0.1 Ma evolution of the island have been analysed for Sr, Nd and high precision Pb isotopic composition. Pb ranges to a less radiogenic composition than on SA [1] and has lower 8/4 than the rocks of the southern EM1-type Cape Verde islands. Most SN lavas have a young HIMU character with negative 7/4. The most radiogenic Pb at SN is less thorogenic than Pb at SA. Temporal variation is also evident: An intermediate age group of samples have particularly low La/Nb = 0.4 - 0.5 and the least LREE-enrichment for SN. The youngest group of rocks has the lowest Zr/Nb = 2.5 - 3.0 and the most unradiogenic Sr and radiogenic Nd in the archipelago. At least four of the mantle source components for the SN magmas are different from any found in the SA magmas. High precision Pb data allow identification of parallel trends for northern SN and the southern island Santiago, which therefore must have unrelated source components. For the northern Cape Verde islands source compositions vary from E to W as well as with time. This cannot be explained by stationary enriched lithosphere components. The derivation of melts from a complex plume source is modelled. [1] Holm P.M., Wilson J.R., Christensen B.P., Hansen S.L., Hein K.M., Mortensen A.K., Pedersen R., Plesner S., and Runge M.K. (2006) JPetrol 47, 145-189.

  6. 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

  7. 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

  8. 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

  9. LA-ICP MS zircon dating, whole-rock and Sr-Nd-Pb-O isotope geochemistry of the Camiboğazı pluton, Eastern Pontides, NE Turkey: Implications for lithospheric mantle and lower crustal sources in arc-related I-type magmatism

    NASA Astrophysics Data System (ADS)

    Kaygusuz, Abdullah; Arslan, Mehmet; Siebel, Wolfgang; Sipahi, Ferkan; İlbeyli, Nurdane; Temizel, İrfan

    2014-04-01

    Late Cretaceous I-type plutons are widespread in the Eastern Pontides, NE Turkey. The studied Camiboğazı pluton is a composite pluton consisting of diorite, tonalite, monzodiorite, monzonite, quartz monzonite, granite, and mafic microgranular enclaves (MMEs). Laser ablation ICP-MS U-Pb dating of zircon yielded crystallization ages of 76.21 ± 0.79 Ma, 75.65 ± 0.50 Ma, 75.04 ± 0.83 Ma, and 74.73 ± 0.86 Ma for diorite, monzodiorite, monzonite, and granite, respectively. The rocks of the pluton have I-type, high-K to shoshonitic and metaluminous character, displaying whole-rock geochemical features of arc-related granites. They are enriched in large-ion lithophile and light rare-earth elements, and depleted in high-field-strength elements. Major element variations can be attributed to fractionation of plagioclase, clinopyroxene, hornblende, and Fe-Ti oxides. The rocks show considerable variation in 87Sr/86Sr(i) (0.70498 to 0.70622), ɛNd(i) (- 2.79 to - 0.36), δ18O values (+ 6.3 to + 11.4) and Nd model ages (TDM) (0.81 Ga to 1.26 Ga). Besides, they have (206Pb/204Pb) = 18.44-19.09, (207Pb/204Pb) = 15.64-15.69, and (208Pb/204Pb) = 38.37-38.89. Although isotope signatures of the mafic microgranular enclaves (MMEs) (87Sr/86Sr(i) = 0.70551 to 0.70622; ɛNd(i) = - 2.9 to - 1.23; δ18O = + 8.3 to + 9.7) are largely similar to the host rocks, MMEs are characterized by relatively high Mg-numbers (32-36), low contents of SiO2 (52-56 wt.%) and low ASI (0.7-0.9). Estimated crystallization temperatures for the rocks of the pluton range from 735 ± 58 °C to 844 ± 24 °C and a shallow intrusion depth (< 10 km) is estimated from Al-in-hornblende thermobarometry. Whole-rock geochemical and isotopic data suggest magma generation by dehydration melting of an amphibolite-type lower crustal component with additional input of a subcontinental lithospheric mantle component. Furthermore, Sr-Nd isotope mixing model reveals ~ 30% to 40% lower crustal magma contribution to the mantle

  10. 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

  11. 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

  12. 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

  13. 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

  14. Geochemistry, zircon U-Pb ages and Sr-Nd-Hf isotopes of an Ordovician appinitic pluton in the East Kunlun orogen: New evidence for Proto-Tethyan subduction

    NASA Astrophysics Data System (ADS)

    Xiong, Fuhao; Ma, Changqian; Wu, Liang; Jiang, Hong'an; Liu, Bin

    2015-11-01

    Appinite is commonly derived from a mantle source in subduction zones and thus holds a key to constrain the tectonic evolution of ancient orogens. This study presents chronological, mineralogical and geochemical data for one appinitic pluton from the south Tethyan suture zone in the East Kunlun orogen, Northern Tibetan Plateau. The pluton is predominantly composed of hornblende-rich mafic appinites, with minor amounts of granodiorite. Zircon U-Pb age of the granodiorite (466 Ma) is identical to the mafic appinites (447-450 Ma). The mafic appinites are commonly hornblende diorites, which comprise large amounts of magnesio-hornblende [Mg/(Fe + Mg) = 0.61-0.68] and andesine (An43-54). The hornblende diorites have low contents of SiO2 (48.62-54.95 wt.%), high contents of total FeO (7.90-12.84 wt.%) and MgO (4.32-11.89 wt.%) and moderate values of Mg# [Mg# = molar 100 ∗ Mg/(Mg + Fe); 49-69]. Their geochemistry displays: slight enrichment of light rare earth elements ((La/Yb)N = 1.89-6.84) and flat heavy rare earth elements ((Ga/Yb)N = 1.49-2.22); enrichment in large ion lithophile elements and depletion in high field strength elements; less-enriched isotopic compositions with initial 87Sr/86Sr ratios of 0.70536-0.70617, εNd(t) of 0.79-3.02 and zircon εHf(t) of 8.73-12.82. The associated granodiorites comprise plagioclase (45-50 vol.%, An = 26-39), quartz (15-20 vol.%), K-feldspar (5-10 vol.%), ferrohornblende [2-5 vol.%, (Mg/(Fe + Mg) = 0.45-0.49] and epidote (1-5 vol.%). The epidotes have pistacite components ranging from 23 to 28. The granodiorites exhibit calc-alkaline character, and have rare earth and trace element patterns similar to the hornblende diorites. The geochemical compositions and simulations suggest that the parental magma of the mafic appinites was generated by partial melting of one depleted mantle source which was metasomatised by subducted sediment-derived felsic melts (ca. 20-25%). Fractional crystallization of clinopyroxene, hornblende

  15. 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

  16. 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

  17. Zircon U-Pb dating, trace element and Sr-Nd-Hf isotope geochemistry of Paleozoic granites in the Miao'ershan-Yuechengling batholith, South China: Implication for petrogenesis and tectonic-magmatic evolution

    NASA Astrophysics Data System (ADS)

    Zhao, Kui-Dong; Jiang, Shao-Yong; Sun, Tao; Chen, Wei-Feng; Ling, Hong-Fei; Chen, Pei-Rong

    2013-09-01

    The Miao'ershan-Yuechengling batholith (MYB) is one of the largest granitic batholiths in South China. At least five individual phases have been identified for the Paleozoic granites in the MYB. SHRIMP and LA-ICP-MS zircon U-Pb dating results imply that these granites were emplaced at 435 ± 4 Ma, 427 ± 3 Ma, 417 ± 6 Ma, 404 ± 6 Ma and 382 ± 2 Ma, respectively. The ages gradually decreased from the southeast to the northwest, implying that the MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian. Most granites are metaluminous to weakly peraluminous, and contain low P2O5 contents (<0.15%). These granites show enrichment of Rb, Th, U and depletion of Ba, Sr, Eu, Ti. They show relatively high (87Sr/86Sr)i ratios (>0.715), low ɛNd(t) values (-8.9 to -6.7), and low zircon ɛHf(t) values (-9.5 to -4.0). These geochemical and isotopic characteristics indicate that these granites may have formed from partial melting of Paleoproterozoic basement rocks. Slight geochemical differences between different phases can be interpreted as resulting from partial melting of heterogeneous sources or different proportion mixing of meta-igneous and meta-sedimentary rocks. Zircon Hf isotope model ages vary from 1.77 to 1.93 Ga, with an average value of 1.84 ± 0.07 Ga. These data indicate that crust growth in this region took place mainly during the Paleoproterozoic (ca. 1.84 Ga), and the basement in the MYB should belong to the Cathaysia Block. The formation of the Paleozoic granites in the MYB was suggested to be related to the late orogenic magmatism of the Wuyi-Yunkai orogeny. Thus, the late orogenic magmatism in the northwestern part of the Wuyi-Yunkai orogeny must have lasted until ca. 381 Ma and took place also to the east of the Anhua-Luocheng Fault.

  18. 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.

  19. Zircon U-Pb dating, geochemistry and Sr-Nd-Pb-Hf-O isotopes for the Nan'getan granodiorites and mafic microgranular enclaves in the East Kunlun Orogen: Record of closure of the Paleo-Tethys

    NASA Astrophysics Data System (ADS)

    Xia, Rui; Wang, Changming; Qing, Min; Li, Wenliang; Carranza, Emmanuel John M.; Guo, Xiaodong; Ge, Liangsheng; Zeng, Guanzhong

    2015-10-01

    The East Kunlun Orogen in the Northern Qinghai-Tibet Plateau is an ideal region to investigate the geodynamic processes of magmatism related to the closure of the Paleo-Tethys Ocean. Here, we report petrology, zircon U-Pb geochronology, whole-rock geochemistry and multiple isotope data from granodiorites and the associated dioritic enclaves in a dominant Nan'getan granitoid in the East Kunlun Orogen. Zircon U-Pb ages indicate that the host granodiorites and dioritic enclaves were synchronously emplaced at ~ 243 Ma. The granodiorites are medium- to high-K calc-alkaline, metaluminous (A/CNK = 0.93-0.98), with high Al2O3 content (15.28%-16.10%), Mg# (47-49), very low Sr/Y ratios (127-217), high abundances of incompatible elements (Y = 3.87-8.36 ppm, Nb = 3.04-5.71 ppm, Th = 3.04-5.71 ppm), low (87Sr/86Sr)i (0.7050-0.7079), negative whole-rock εNd(t) (- 8.2 to - 5.8), (206Pb/204Pb) 243Ma of 18.520 to 18.772, (207Pb/204Pb) 243Ma of 15.611 to 15.650, (208Pb/204Pb) 243Ma of 38.227 to 38.528, δ18OSMOW = 6.8‰-9.1‰, εHf(t) of - 1.2 to + 2.4. The dioritic enclaves (SiO2 = 51.08%-56.29%) have Mg# values of 48-51, with negative Eu anomalies (δEu = 0.59-0.79), low (87Sr/86Sr)i (0.7058-0.7080), negative whole-rock εNd(t) (- 8.2 to - 5.8), (206Pb/204Pb) 243Ma of 18.376 to 18.809, (207Pb/204Pb)243Ma of 15.606 to 15.661, (208Pb/204Pb)243Ma of 38.244 to 38.540, δ18OSMOW = 5.6‰-10.0‰, εHf(t) of - 3.5 to + 1.7. These isotopic features of arc-type rocks from the East Kunlun suggest that the parental magmas of the Nan'getan granodiorites and the dioritic enclaves originated from an enriched lithospheric mantle. The Nan'getan granitoids might have recorded the northward subduction of the Paleo-Tethys ocean lithosphere following the initial collision of the Bayan Har-Songpan Ganzi-East Kunlun terrane and the closure of the Paleo-Tethys Ocean at ~ 243 Ma.

  20. 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

  1. Geochemistry, Sr-Nd-Pb isotopes and geochronology of amphibole- and mica-bearing lamprophyres in northwestern Iran: Implications for mantle wedge heterogeneity in a palaeo-subduction zone

    NASA Astrophysics Data System (ADS)

    Aghazadeh, Mehraj; Prelević, Dejan; Badrzadeh, Zahra; Braschi, Eleonora; van den Bogaard, Paul; Conticelli, Sandro

    2015-02-01

    Lamprophyres of different age showing distinctive mineralogy, geochemistry and isotopic ratios are exposed in northwestern Iran. They can be divided into Late Cretaceous sannaite, Late Oligocene-Early Miocene camptonite (amphibole-bearing) and Late Miocene minette (mica-bearing) and spessartite (amphibole-bearing) lamprophyres. Sannaites have high-Ti amphibole along with high-Ti and Al clinopyroxene, and they are characterised by homogeneous enrichment in incompatible trace elements with troughs at Pb. Spessartites have hornblende and low-Al and Ti clinopyroxene, and they are characterised by enriched incompatible trace element pattern with depletions of Nb, Ta, Pb, and Ti with respect to large ion lithophile elements. Minettes have high-Ti and Al brown mica and low-Al and Ti clinopyroxene, and similar to spessartite, are characterised by fractionation of high field strength elements with respect to large ion lithophile elements, with troughs at Nb, Ta, and Ti and a peak at Pb. Minettes show high initial 87Sr/86Sr values up to 0.70760 and low initial 143Nd/144Nd down to 0.512463 with a negative correlation, consistent with the trace element distribution related with an enriched mantle source modified after sediment recycling during subduction and continental collision. Cretaceous sannaites and Early Miocene spessartites show low initial 87Sr/86Sr approaching 0.70447 and high 143Nd/144Nd values up to 0.512667, which are consistent with a depleted within-plate mantle source. Minette and spessartite lamprophyres show high initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values, whereas sannaites have lower, but variable, initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values with respect to those of calc-alkaline lamprophyres. Minettes originated by partial melting of a metasomatised lithospheric mantle following siliciclastic sediment recycling by subduction. In contrast, sannaites were generated from the partial melting of a similar lithospheric mantle that was

  2. 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...

  3. 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.

  4. 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. PMID:25870921

  5. 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.

  6. 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

  7. 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.

  8. Le complexe annulaire d'âge Oligocène de l'Achkal (hoggar Central, Sud Algérie) : témoin de la transition au Cénozoïque entre les magmatismes tholéitique et alcalin. Évidences par les isotopes du Sr, Nd et Pb

    NASA Astrophysics Data System (ADS)

    Maza, Mustapha; Briqueu, Louis; Dautria, Jean-Marie; Bosch, Delphine

    1998-08-01

    The Achkal Oligocene ring complex cross-cuts the Upper Eocene tholeiitic traps located on the top of the Hoggar swell. The plutonic rocks range from tholeiitic gabbros to alkali essexites, monzonites and syenites, whereas the volcanites are restricted to late peralkaline rhyolites. The affinity change linked to the large isotopic heterogeneities (from EM1 to HIMU) suggests that the parental magmas are issued from two distinct mantle sources, first lithospheric then deeper. The Achkal has recorded the magmatic evolution of the Hoggar hot spot, between Eocene and Miocene.

  9. Synthesis and catalytic properties of mixed oxides in the Sr-Nd-Cu-Cr-Al-O system in oxidation of carbon monoxide

    SciTech Connect

    Komarov, V.S.; Varlamov, V.I.

    1986-05-10

    Much attention is being devoted to production of effective mixed oxide catalysts for treatment of exhaust gases. It was of interest in this connection to study the influence of the individual components of the Sr-Nd-Cu-Cr-Al-O system on the phase composition and catalytic properties of samples obtained from it. The test samples were prepared from analytical-grade neodymium oxalate and 1 M aqueous solutions of metal nitrates of the same purity grade. Weighed portions of the neodymium salt and of triammonium citrate were added n the required proportions to an a equimolar mixture of these solutions. The reaction mixture was evaporated on a water bath with periodic stirring until a resinous product was obtained; this was decomposed at its ignition temperature with the aid of an incandescent lamp. The resultant mass was powdered and heated in air at 700 and 900 for 6 h.

  10. 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.

  11. 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

  12. 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

  13. Chemical and isotopic properties and origin of coarse airborne particles collected by passive samplers in industrial, urban, and rural environments

    NASA Astrophysics Data System (ADS)

    Guéguen, Florence; Stille, Peter; Dietze, Volke; Gieré, Reto

    2012-12-01

    Passive air samplers have been installed in industrial, urban, rural and remote forested environments in order to collect coarse airborne particles for subsequent chemical characterization. To identify principal polluting sources, isotopic tracers, such as Sr, Nd and Pb isotopic ratios, have been used. The mass deposition rates (MDRs) of trace metals, determined for each of the studied environments, clearly indicate that industrial and traffic sites are especially affected by air pollution. Elements such as V, Pb, Fe, Cr, Co, Mo, Cd, Ni, As, Sb and Zn are notably enriched in samples from industrial zones, whereas V, Mn, Ba, Sr, Al, U, Th, rare earth elements (REE), Zr, Y, Cs, Rb, Sb, Sn and Cu are principal components of the airborne particles collected close to areas influenced by heavy traffic. The chemical/isotopic baseline composition derived from the airborne particles is the result of mixing of particles from different industrial sources, traffic and fertilizers. The monthly analysis of trace-metal MDRs of the collected airborne particle samples from different stations around the industrial zone allows for the detection of distinct atmospheric dust-deposition events during the year, characterized by high MDRs. "Natural" dusts from regional soil re-suspension, including from more distant regions like the Sahara desert, might overprint the regional atmospheric baseline composition, as suggested by trace metal trajectories in ternary diagrams and by Sr, Nd and Pb isotope data.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. A Pb isotope investigation of the Lovozero Agpaitic Nepheline Syenite, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Zartman, R. E.; Kogarko, L. N.

    2014-01-01

    For the first time Pb isotope composition was established in Lovozero rocks and raremetal ores, which is important for identifying their sources. The world's largest layered intrusion of agpaitic nepheline syenite-the Lovozero alkaline massif—is located near the center of the Kola Peninsula in Russia. This superlarge complex plutonic body hosts the economically important loparite and eudiallyte deposits [1]. These deposits contain immense resources of REE, Nb, Ta, Zr, and constitute a world class mineral district. The Lovozero massif belongs to the Kola ultramafic alkaline and carbonatitic province (KACP) of Devonian age. Previous bulk rock studies have shown that the initial Sr and Nd isotope ratios of Lovozero rocks plot in the depleted mantle quadrant of Sr-Nd diagrams [2]. More recently, Hf isotope data obtained by Kogarko et al. (3) confirm that the Lovozero and Khibina massifs with ɛHf between 6 and 8 are derived predominantly from a depleted mantle source. It was shown that Sr, Nd, and Hf abundances are significantly elevated in the Kola alkaline rocks, and thus their isotopic compositions are relatively insensitive to minor contamination by the overlying crustal rocks. By contrast, Pb in the KACP rocks is a much more sensitive indicator of a crustal component. In this paper we investigate the lead isotopic signature of all resentative types of Lovozero rocks (Table 1) in order to further characterize their mantle sources. The Lovozero massif consists of four intrusive phases. Rocks of phase I (mostly nepheline syenites) comprise about 5% of the total volume, phase II (urtites, foyaite, lujavrites) forms the main portion of the massif comprising 77% in volume, and phase III (eudialyte lujavrites) contributes about 18%. Country rocks are represented by Devonian effusive rocks and Archean gneisses.

  19. 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/cgi-bin/nph-data_query?bibcode=2015GeCoA.167..286B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015GeCoA.167..286B&link_type=ABSTRACT"><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> </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/cgi-bin/nph-data_query?bibcode=2016GeCoA.189..236C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeCoA.189..236C&link_type=ABSTRACT"><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/2013Litho.162..301Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Litho.162..301Z"><span id="translatedtitle">Geochemical and <span class="hlt">isotopic</span> constraints on the petrogenesis of the Puesto La Peña undersaturated potassic complex, Mendoza province, Argentina: 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>Zappettini, Eduardo O.; Villar, Luisa M.; Hernández, Laura B.; Santos, João O.</p> <p>2013-03-01</p> <p>Major and trace element and radiogenic and stable <span class="hlt">isotope</span> data are reported for the Miocene Puesto La Peña undersaturated potassic complex, located in the Argentine Precordillera. The complex is composed of a pyroxenite core surrounded by a malignite-borolanite association, followed by radial and ring dikes composed of alkaline lamprophyres, tephrite to phonolite and intermediate varieties, porphyritic microledmorite, benmoreite, alkaline trachyte and a swarm of ultrabasic ouachitite dikes. Late trachytic to phonolitic volcanic necks and associated dikes crop out surrounding the malignitic-borolanitic massif. Major and trace element data are consistent with their derivation by partial melting from an enriched, probably lithospheric, metasomatized heterogeneous mantle involving spinel- and garnet-facies mantle sources. The trace element and <span class="hlt">isotope</span> data indicate that all rock types are derived from a common parental magma and are thus cogenetic. <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb variations in the different <span class="hlt">studied</span> lithologies are restricted, except for the evidence of Sr decoupling in the ouachitite samples. Their <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> compositions follow the "mantle array" defined by oceanic basalts, within the OIB field, consistent with an intraplate depleted source. The genesis of the ouachitite is interpreted to be related to mixing between asthenospheric magma and melts from the lower lithosphere consisting of K-rich metasomatic layers. The Dupal like Pb <span class="hlt">isotopes</span> signature suggests a mantle modification by introduction of continental crust material in the upper mantle; this is consistent with the <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> data from the late silica-undersaturated felsic dikes and volcanic necks. Multistage mantle extraction would have occurred by the end of Neoproterozoic to lower Paleozoic times as indicated by the <span class="hlt">isotopic</span> data. Partial melting was initiated by mantle upwelling decompression during lithosphere extension. Back-arc extensional conditions during the latest Early Miocene (19 Ma</p> </li> <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://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/cgi-bin/nph-data_query?bibcode=2015AGUFMDI31A2558G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFMDI31A2558G&link_type=ABSTRACT"><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://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://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://adsabs.harvard.edu/abs/2002LPI....33.1789S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002LPI....33.1789S"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">Study</span> of Silicon Carbide in Semarkona</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, J. B.; Huss, G. R.</p> <p>2002-03-01</p> <p>We have measured Si and C <span class="hlt">isotopes</span> for individual SiC grains from Semarkona. Our results are compared with those of previous <span class="hlt">studies</span> on SiC from Murchison and Orgueil. Metamorphism and grain-size distribution can affect these comparisons.</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://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://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://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=74955&keyword=dept+AND+state&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=74029618&CFTOKEN=24887313','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=74955&keyword=dept+AND+state&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=74029618&CFTOKEN=24887313"><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://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/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://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/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://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://www.ncbi.nlm.nih.gov/pubmed/27046667','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27046667"><span id="translatedtitle"><span class="hlt">Isotope</span> Labeling <span class="hlt">Study</span> of Retinal Chromophore Fragmentation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Musbat, Lihi; Nihamkin, Maria; Ytzhak, Shany; Hirshfeld, Amiram; Friedman, Noga; Dilger, Jonathan M; Sheves, Mordechai; Toker, Yoni</p> <p>2016-04-28</p> <p>Previous <span class="hlt">studies</span> have shown that the gas-phase fragmentation of the retinal chromophore after S0-S1 photoexcitation results in a prominent fragment of mass 248 which cannot be explained by the cleavage of any single bond along the polyene chain. It was therefore theorized that the fragmentation mechanism involves a series of isomerizations and cyclization processes, and two mechanisms for these processes were suggested. Here we used <span class="hlt">isotope</span> labeling MS-MS to provide conclusive support for the fragmentation mechanism suggested by Coughlan et al. (J. Phys. Chem. Lett. 2014, 5, 3195). PMID:27046667</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://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> </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://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> <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://www.osti.gov/scitech/biblio/7027139','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7027139"><span id="translatedtitle"><span class="hlt">Studies</span> of enzyme mechanism using <span class="hlt">isotopic</span> probes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen, C.</p> <p>1987-01-01</p> <p>The <span class="hlt">isotope</span> partitioning <span class="hlt">studies</span> of the Ascaris suum NAD-malic enzyme reaction were examined with five transitory complexes including E:NAD, E:NAD:Mg, E:malate, E:Mg:malate, and E:NAD:malate. Three productive complexes, E:NAD, E:NAD:Mg, and E:Mg:malate, were obtained, suggesting a steady-state random mechanism. Data for trapping with E:/sup 14/C-NAD indicate a rapid equilibrium addition of Mg/sup 2 +/ prior to the addition of malate. Trapping with /sup 14/C-malate could only be obtained from the E:Mg/sup 2 +/:/sup 14/C-malate complex, while no trapping from E:/sup 14/C-malate was obtained under feasible experimental conditions. The equations for the <span class="hlt">isotope</span> partitioning <span class="hlt">studies</span> varying two substrates in the chase solution in an ordered terreactant reaction were derived, allowing a determination of the relative rates of substrate dissociation to the catalytic reaction for each of the productive transitory complexes. NAD and malate are released from the central complex at an identical rate, equal to the catalytic rate. The release of NAD from E:NAD and E:NAD:Mg complexes is 2- to 4-fold and 5- to 9-fold V/sub max//E/sub t/, respectively. The release of malate from the E:Mg:malate complex is 0.1- to 0.3-fold of V/sub max//E/sub t/. The individual rate constants for association and dissociation of the substrates, NAD and malate have been estimated.</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/cgi-bin/nph-data_query?bibcode=2016GeCoA.183...94S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeCoA.183...94S&link_type=ABSTRACT"><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/2011AGUFM.T44D..04H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T44D..04H"><span id="translatedtitle">Tracing the sublithospheric sources of continental flood basalts: multi-elemental <span class="hlt">isotopic</span> <span class="hlt">studies</span> on the recently found ferropicrites and meimechites from the Karoo large igneous province</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heinonen, J. S.; Carlson, R. W.; Luttinen, A. V.</p> <p>2011-12-01</p> <p>There is a substantial debate on the mantle sources and ultimate origins of continental flood basalts (CFBs), e.g., whether they are related to deep-seated thermal upwellings (i.e. mantle plumes) or not. The Karoo CFB province that was emplaced on the juxtaposed land masses of Africa and Antarctica during the early stages of the breakup of the Gondwana supercontinent ~180 Ma ago has played a central role in this debate. Although most of the structural analyses, geochemical affinities, and temporal relationships of Karoo-related rocks point to a strong control of lithosphere on the magmatism, paleostress estimates for some of the Karoo dikes and high mantle potential temperatures estimated for the sources of recently found highly magnesian rocks from Antarctica are compatible with the plume theory. Volcanic rocks that do not show evidence of lithospheric influence in their geochemistry are extremely rare in the African part of the Karoo province. Here we present high-precision <span class="hlt">isotopic</span> (<span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Pb, and Os) whole-rock data on some primitive dike rocks (ferropicrites and meimechites) associated with its Antarctic extension. The <span class="hlt">isotopic</span> data together with trace element data show that the parental melts of the <span class="hlt">studied</span> rocks sampled two distinctive geochemical reservoirs in the deep sub-Gondwanan mantle. The <span class="hlt">isotopic</span> signatures of the relatively depleted types show evidence of extensive melt extraction in the past and are indistinguishable from those of mid-ocean ridge basalts (MORBs) of the SW Indian Ridge, the modern successor of the Jurassic Africa-Antarctica rift. On the other hand, the relatively enriched type <span class="hlt">isotopically</span> resembles modern oceanic island basalts (OIBs) and may sample pyroxenitic sources either formed by melt infiltration in the upper mantle or by reaction of peridotite with recycled oceanic crustal components. Recent Ar-Ar datings of the depleted types indicate that they are related to the main phase of Karoo magmatism ~180 Ma ago. Moreover</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910065440&hterms=identification+genetic+material&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Didentification%2Bgenetic%2Bmaterial','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910065440&hterms=identification+genetic+material&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Didentification%2Bgenetic%2Bmaterial"><span id="translatedtitle">Oxygen <span class="hlt">isotope</span> <span class="hlt">studies</span> of ordinary chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clayton, Robert N.; Mayeda, Toshiko K.; Olsen, Edward J.; Goswami, J. N.</p> <p>1991-01-01</p> <p>Several stages in the evolution of ordinary chondritic meteorites are recorded in the oxygen <span class="hlt">isotopic</span> composition of the meteorites and their separable components (chondrules, fragments, clasts, and matrix). The whole-rock <span class="hlt">isotopic</span> compositions reflect the iron-group of the meteorite (H, L, or LL). <span class="hlt">Isotopic</span> uniformity of H3 to H6 and L3 to L6 are consistent with closed-system metamorphism within each parent body. LL3 chondrites differ slightly from LL4 to LL6, implying a small degree of open-system aqueous alteration and carbon reduction. On the scale of individual chondrules, the meteorites are <span class="hlt">isotopically</span> heterogeneous, allowing recognition of the solar-nebular processes of chondrule formation. Chondrules for all classes of ordinary chondrites are derived from a common population, which was separate from the population of chondrules in carbonaceous or enstatite chondrites. Chondrules define an <span class="hlt">isotopic</span> mixing line dominated by exchange between (O - 16)-rich and (O - 16)-poor reservoirs. The oxygen <span class="hlt">isotopic</span> compositions of chondrites serve as 'fingerprints' for identification of genetic association with other meteorite types (achondrites and iron) and for recognition of source materials in meteoritic breccias.</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://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/2011GeCoA..75.2696N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GeCoA..75.2696N"><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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ni, Yunyan; Ma, Qisheng; Ellis, Geoffrey S.; Dai, Jinxing; Katz, Barry; Zhang, Shuichang; Tang, Yongchun</p> <p>2011-05-01</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 280.2 cal/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 δD values in ethane from several basins in the world are in close agreement with similar predictions based on the δ 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 δD 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 δD values in ethane might be more suitable for modeling than comparable values in methane and propane.</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/2014EGUGA..1610984S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610984S"><span id="translatedtitle">Age (U-Pb zircon) and <span class="hlt">isotope</span>-geochemical characteristics of bedrocks from New Siberian islands and its tectonic implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sergeev, Sergey; Petrov, Oleg; Belyatsky, Boris; Sobolev, Nikolay; Shokalsky, Sergey; Shevchenko, Sergey; Krymsky, Robert; Petrov, Evgeny</p> <p>2014-05-01</p> <p>New Siberian archipelago (Anjou, De Long, Lyakhov's islands) is a crucial impact into the interpretation of the geological structures and ages of the basement of the East Siberian shelf rises along with the problem of the ancient Arctida continent existence [Zonenshain et al., 1990; Sokolov et al., 2002], the dating of igneous events in the Eastern Arctic, and estimation of possibility and the extent of mafic melts of High Arctic Igneous Provinces (including HALIP) crustal contamination. More than 80 samples of gabbro-dolerites, picrodolerites, basalts, volcanic tuffs, terrigenous clastic rocks and granitoids collected during 2011-2013 International high-latitude expeditions to the Henriette, Jeannette, Bennett, Zhokhov, Kotel'ny, Bel'kov and B.Lyakhov islands have been <span class="hlt">studied</span>. Sr and Nd mineral isochronous, U-Pb zircon (SIMS) ages and <span class="hlt">isotope</span>-geochemical signatures (<span class="hlt">Sr-Nd</span>-Pb-Os) of magmatic melts sources were performed. Precambrian (Late Proterozoic) crystalline basement has been clearly identified for the New Siberian islands: granitoids, 550-600 My old, gabbro and dolerites (600-650 Ma). All of them contain inherited Paleoproterozoic and Archean zircons, while older (2.8-3.0 Ga) zircons are found in the rocks from the northern (De Long) islands, and in the rocks of the southern islands (Anjou and Lyakhov's) the most ancient zircons are of 1.7 Gy old. Moreover, in the De Long islands rocks Caledonian (460-490 Ma) reworking of Precambrian rocks is definitely fixed. Thus the rise of New Siberian archipelago most probably is a fragment of an ancient Arctida continent. Dating of the mafic rocks and granitoids revealed also three Phanerozoic magmatic events: (1) 230-253 Ma - basic magmatism associated with the activities of the Siberian plume (developed on the southern islands - Kotel'ny and B.Lyakhov), (2) 165-185 Ma - ophiolite complex of B.Lyakhov and gabbro-dolerite intrusions of Kotel'ny island, and (3) 111-122 Ma - collisional granitoid magmatism within the</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://adsabs.harvard.edu/abs/1986E%26PSL..78..189E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986E%26PSL..78..189E"><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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Exley, R. A.; Mattey, D. P.; Clague, D. A.; Pillinger, C. T.</p> <p>1986-06-01</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. δ 13C = -26.3‰ ) released < 600°C, ascribed to surficial contamination, and (2) <span class="hlt">isotopically</span> heavy carbon released > 600°C, regarded as indigenous. The high-temperature component in MORB samples varied from 52 to 169 ppm C, average δ 13C = -6.6‰ , consistent with previous <span class="hlt">studies</span> (overall MORD average δ 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 δ 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 δ 13C values significantly (avg. -5.8‰). Loihi tholeiites have higher δ 13C (avg. -5.6‰) than the alkali basalts (avg. -7.1‰). Carbon abundances correlate well with He concentration data. Comparison of the δ 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 δ 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 δ 13C of Loihi tholeiites suggests that the undegassed "plume" component manifested by high 3He/ 4He values might have δ 13C about 1‰ higher than the MORB average.</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> <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> </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://adsabs.harvard.edu/abs/2011NIMPA.652..116B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011NIMPA.652..116B"><span id="translatedtitle">An <span class="hlt">isotope</span> identification injection <span class="hlt">study</span> with GammaTracker</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Batdorf, Michael T.; Erikson, Luke E.; Seifert, Carolyn E.; Myjak, Mitchell J.; Kirihara, Leslie J.</p> <p>2011-10-01</p> <p>GammaTracker is a portable handheld radioisotope identifier using position sensitive CdZnTe detectors. High confidence <span class="hlt">isotope</span> identification is possible on GammaTracker owing to the system's relatively high energy resolution and count rate sensitivity. A <span class="hlt">study</span> was undertaken to evaluate the <span class="hlt">isotope</span> identification performance of a prototype unit. Background and source spectra for various nuclides were measured and then randomly sampled to simulate various integration times and source intensities. The resulting spectral data sets were then run through the <span class="hlt">isotope</span> identification algorithm to determine the probability of detection and the false alarm rate for each nuclide. The process was repeated for various <span class="hlt">isotope</span> identification input parameters until an optimized set was achieved. This paper presents results from the injection <span class="hlt">study</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/3149535','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/3149535"><span id="translatedtitle">Rapid sample throughput for biomedical stable <span class="hlt">isotope</span> tracer <span class="hlt">studies</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Preston, T; McMillan, D C</p> <p>1988-10-01</p> <p>Typical 13C or 15N tracer <span class="hlt">studies</span> generate large numbers of samples. Instrumentation capable of rapid automated analysis is therefore of importance as a practical alternative to conventional <span class="hlt">isotope</span> methodology. Although biomedical sample nature is diverse, experimenters often require analysis of substrates and products of particular biochemical pathways. Clearly, reaction products can contain considerably less <span class="hlt">isotope</span> tracer than precursors. Analytical techniques thus need to accommodate samples of widely varying nature, size and <span class="hlt">isotope</span> enrichment. In the clinical field, where stable <span class="hlt">isotopes</span> are increasingly used to <span class="hlt">study</span> protein, carbohydrate and fat metabolism, analysis of the <span class="hlt">isotope</span> ratio of a substrate infused into the plasma and a product of its metabolism is often required. Conventional analytical approaches demand access to two mass spectrometers: <span class="hlt">isotope</span> ratio mass spectrometry (IRMS) for <span class="hlt">isotope</span> analysis of the relatively large concentrations of low-enrichment metabolic product, and gas chromatography/mass spectrometry (GC/MS) for analysis of the infused substrate often present at high enrichment but low concentration offers a practical alternative to the conventional approaches that is rapid and automatic. In addition to providing a considerably less complex and costly alternative to conventional instrumentation, a single CF-IRMS instrument can also analyse small quantities of low-enrichment metabolites with superior performance than either of the alternative approaches. CF-IRMS is illustrated using results from constant-infusion <span class="hlt">studies</span> in human protein and fat metabolism which require measurement of the <span class="hlt">isotope</span> enrichment in submicromolar quantities of plasma substrates together with analysis of larger quantities of their oxidation products, urinary nitrogen and breath CO2. PMID:3149535</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003TrGeo...5..319K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003TrGeo...5..319K&link_type=ABSTRACT"><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/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://adsabs.harvard.edu/abs/2015JAESc.111..192B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAESc.111..192B"><span id="translatedtitle">U-Pb zircon geochronology, <span class="hlt">Sr-Nd</span> geochemistry, petrogenesis and tectonic setting of Mahoor granitoid rocks (Lut Block, Eastern Iran)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beydokhti, Roohollah Miri; Karimpour, Mohammad Hassan; Mazaheri, Seyed Ahmad; Santos, José Francisco; Klötzli, Urs</p> <p>2015-11-01</p> <p>The Mahoor Cu-Zn-bearing porphyritic granitoid rocks belong to the Lut Block volcanic-plutonic belt (central Eastern Iran). These granitoid rocks occur mainly as dykes and stocks that intrude into Eocene volcanics and pyroclastic rocks. Petrographically, all the <span class="hlt">studied</span> intrusives display porphyritic textures with mm-sized phenocrysts, most commonly of plagioclase and hornblende, embedded in a fine-grained groundmass with variable amounts of plagioclase, hornblende, clinopyroxene, quartz and opaque minerals. Hydrothermal alteration affected these granitoid rocks, as revealed by the common occurrence of sericite, chlorite, titanite, epidote and calcite. Chemical classification criteria show that the intrusives may be named as gabbrodiorites, diorites, monzodiorites and tonalites. Major elements geochemistry reveals that all the <span class="hlt">studied</span> lithologies are typically metaluminous (A/CNK ⩽ 0.9). Magnetic susceptibility (1485 × 10-5 SI) together with mineralogical and geochemical features shows that they belong to magnetite granitoid series (I-type). Trace element patterns normalized to chondrite and primitive mantle are very similar to each other and show enrichments in LREE relative to HREE and in LILE relative to HFSE, as well as negative anomalies of Ta, Nb and Ti. Eu/Eu∗ ratios vary from 0.88 (in the most mafic composition) to 0.65, showing that plagioclase played a role in magma differentiation. LA-MC-ICP-MS U-Pb zircon data from a diorite, yielded similar concordia ages of ca. 31.88 ± 0.2 Ma (Error: 2σ), which corresponds to the Oligocene period. These granitoid rocks have (87Sr/86Sr)i values vary between 0.7055 and 0.7063. In terms of <span class="hlt">isotopic</span> compositions, while εNdi is between -0.6 and -2.5, suggesting that magmas underwent contamination through being exposed to the continental crust. The whole set of geochemical data agree with the emplacement of the <span class="hlt">studied</span> intrusions in a magmatic belt above a subduction zone. Primitive magmas should have formed by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ARMS....8..379C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ARMS....8..379C&link_type=ABSTRACT"><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="http://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('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('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/abs/2015EGUGA..17.2263Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2263Y"><span id="translatedtitle">Groundwater surface water interaction <span class="hlt">study</span> using natural <span class="hlt">isotopes</span> tracer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoon, Yoon Yeol; Kim, Yong Chul; Cho, Soo Young; Lee, Kil Yong</p> <p>2015-04-01</p> <p>Tritium and stable <span class="hlt">isotopes</span> are a component of the water molecule, they are the most conservative tracer for groundwater <span class="hlt">study</span>. And also, radon is natural radioactive nuclide and well dissolved in groundwater. Therefore, these <span class="hlt">isotopes</span> are used natural tracer for the <span class="hlt">study</span> of surface water and groundwater interaction of water curtain greenhouse area. The <span class="hlt">study</span> area used groundwater as a water curtain for warming tool of greenhouse during the winter, and is associated with issues of groundwater shortage while being subject to groundwater-river water interaction. During the winter time, these interactions were <span class="hlt">studied</span> by using Rn-222, stable <span class="hlt">isotopes</span> and H-3. These interaction was monitored in multi depth well and linear direction well of groundwater flow. And dam effect was also compared. Samples were collected monthly from October 2013 to April 2014. Radon and tritium were analyzed using Quantulus low background liquid scintillation counter and stable <span class="hlt">isotopes</span> were analyzed using an IRIS (<span class="hlt">Isotope</span> Ratio Infrared Spectroscopy ; L2120-i, Picarro). During the winter time, radon concentration was varied from 0.07 Bq/L to 8.9 Bq/L and different interaction was showed between dam. Surface water intrusion was severe at February and restored April when greenhouse warming was ended. The stable <span class="hlt">isotope</span> results showed different trend with depth and ranged from -9.16 ‰ to -7.24 ‰ for δ 18O value, while the δD value was ranged from -57.86 ‰ to -50.98 ‰. The groundwater age as dated by H-3 was ranged 0.23 Bq/L - 0.59 Bq/L with an average value of 0.37 Bq/L.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900049316&hterms=natural+zeolites&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dnatural%2Bzeolites','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900049316&hterms=natural+zeolites&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dnatural%2Bzeolites"><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://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Karlsson, Haraldur R.; Clayton, Robert N.</p> <p>1990-01-01</p> <p>The oxygen <span class="hlt">isotope</span> fractionation between analcime and water is <span class="hlt">studied</span> to test the feasibility of using zeolites as low-temperature thermometers. The fractionation of oxygen <span class="hlt">isotopes</span> between natural analcime and water is determined at 300, 350, and 400 C, and at fluid pressures ranging from 1.5 to 5.0 kbar. Also, <span class="hlt">isotope</span> ratios for the analcime framework, the channel water, and bulk water are obtained. The results suggest that the channel water is depleted in O-18 relative to bulk water by a constant value of about 5 percent, nearly independent of temperature. The analcime-water fractionation curve is presented, showing that the exchange has little effect on grain morphology and does not involve recrystallization. The exchange is faster than any other observed for a silicate. The exchange rates suggest that zeolites in active high-temperature geothermal areas are in oxygen <span class="hlt">isotopic</span> equilibrium with ambient fluids. It is concluded that calibrated zeolites may be excellent low-temperature oxygen <span class="hlt">isotope</span> geothermometers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18323089','PUBMED'); return false;" href="http://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="http://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://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://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=34369&keyword=human+AND+memory&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=77065302&CFTOKEN=42849805','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=34369&keyword=human+AND+memory&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=77065302&CFTOKEN=42849805"><span id="translatedtitle"><span class="hlt">ISOTOPIC</span> <span class="hlt">STUDY</span> OF THE INHALATION TOXICOLOGY OF OXIDANTS</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 purpose of these <span class="hlt">studies</span> was to develop novel methods to investigate the biological fate of inhaled ozone and other oxygen-containing pollutants in animal and human tissues using the heavy <span class="hlt">isotope</span> of oxygen, oxygen-18 (18O). Methods were developed which facilitated the conver...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008E%26PSL.276....1B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008E%26PSL.276....1B"><span id="translatedtitle">A multiple-system <span class="hlt">study</span> of the geochemical evolution of the mantle with force-balanced plates and thermochemical effects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandenburg, J. P.; Hauri, Erik H.; van Keken, Peter E.; Ballentine, Chris J.</p> <p>2008-11-01</p> <p>Here, multiple <span class="hlt">isotope</span> systems are tracked simultaneously in models of mantle convection and it is show that this can provide powerful constraints on the role of oceanic crust recycling in the development of <span class="hlt">isotopic</span> end-member compositions. The dynamical models are based on high-resolution cylindrical calculations with force-balanced plates and variable chemical density. The dynamic results span a parameter space of variable realistic excess crustal density compared to experimental estimates and convective vigor measured by plate velocities and surface heat flow. <span class="hlt">Isotope</span> geochemistry is then modeled for the U-Th-Pb, Sm-Nd, Rb-Sr, and Re-Os <span class="hlt">isotope</span> systems. The role of a dense crustal layer in development of a HIMU-<span class="hlt">isotope</span> signature is confirmed. The extraction of continental crust is found to be essential for the formation of all <span class="hlt">isotope</span> compositional end-members, including HIMU. This extraction is implemented as an ad-hoc process secondary to partial melting at mid-ocean ridges and constrained by estimated <span class="hlt">isotopic</span> abundances in the present-day crust. Whereas previous <span class="hlt">studies</span> generated mantle <span class="hlt">isotopic</span> arrays that spanned DMM-HIMU, the additional <span class="hlt">isotope</span> systems in this analysis indicate that enrichment purely from ancient oceanic crust may also generate an EM-I component without invoking the subduction of sediment. In this case, the EM-I signature may be indicative of mantle enriched by oceanic crust produced before 2.25 Byr, while the HIMU signature indicates enrichment by oceanic crust extracted more recently. However, it is found to be difficult to maintain a true DMM <span class="hlt">isotopic</span> end member in <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> space when significantly enriched end-members are present. This may highlight the sensitivity of the Rb-Sr system to mass exchange between the upper and lower mantle.</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://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://adsabs.harvard.edu/abs/2011GGG....12.AC14H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GGG....12.AC14H"><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://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.V43C4903B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.V43C4903B&link_type=ABSTRACT"><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> </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.ars.usda.gov/research/publications/Publications.htm?seq_no_115=202944','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=202944"><span id="translatedtitle">Subcutaneous infusion and capillary "finger stick" sampling of stable <span class="hlt">isotope</span> tracer in metabolic <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Metabolic <span class="hlt">studies</span> utilizing stable <span class="hlt">isotope</span> tracer in humans have typically used intravenous tracer infusions and venous blood sampling. These <span class="hlt">studies</span> explore subcutaneous infusion of <span class="hlt">isotope</span> and "finger stick" capillary blood sampling to measure glucose turnover. Five subjects received simultaneous ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001GeCoA..65..589V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001GeCoA..65..589V"><span id="translatedtitle">Oxygen <span class="hlt">isotope</span> systematics of the Banda Arc: low δ 18O despite involvement of subducted continental material in magma genesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vroon, P. Z.; Lowry, D.; van Bergen, M. J.; Boyce, A. J.; Mattey, D. P.</p> <p>2001-02-01</p> <p>This <span class="hlt">study</span> reports new laser fluorination oxygen <span class="hlt">isotope</span> data for 60 volcanic rocks and 15 sediments distributed over the whole length of the Banda Arc, eastern Indonesia. The melt oxygen <span class="hlt">isotope</span> values (δ 18O melt) were calculated from phenocryst δ 18O data using theoretical and empirical mineral-melt fractionation factors. The δ 18O melt of individual volcanic centers within the arc varies between 5.57 and 6.54‰, except for Serua (δ 18O melt = 6.13-7.48‰) and Ambon (δ 18O melt = 8.12-8.38‰). These δ 18O melt values are up to 2‰ lower than new and previously published oxygen <span class="hlt">isotope</span> data obtained on whole-rock powders by conventional methods. We attribute this discrepancy to post-emplacement low-temperature alteration and/or to a systematic deviation of the bulk analysis. Sediment δ 18O wr (calculated from the δ 18O carbonate and silica fractions, both measured conventionally) range between 12.9 and 24.2‰. The low δ 18O melt values (excluding Serua and Ambon) overlap with the mantle range, and are in agreement with simple two-component source-mixing models that predict 1-5% addition of subducted continental material to a depleted MORB-type source in the sub-arc mantle. This percentage is consistent with previous models based on <span class="hlt">Sr-Nd</span>-Pb-Th-He-Hf <span class="hlt">isotope</span> data. However, correlations between incompatible trace-element ratios and oxygen <span class="hlt">isotope</span> systematics requires involvement of partial melts derived from subducted continental material as the major slab component rather than bulk addition. The contribution of hydrous fluids, from both subducted altered oceanic crust and continental material is probably of minor importance. Magma-mantle wedge interaction models could account for the observed low δ 18O signatures, but predicted effects are difficult to distinguish from models without mantle-wedge interaction. Assimilation of arc-crust material is thought to be important for the high δ 18O melt values of Serua and Ambon. AFC modelling suggests up to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.B52A..01F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.B52A..01F"><span id="translatedtitle">Sulfur and oxygen <span class="hlt">isotope</span> <span class="hlt">studies</span> of sulfate reduction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farquhar, J.; Canfield, D. E.; Bao, H.; Masterson, A.; Johnston, D. T.; Wing, B. A.</p> <p>2007-12-01</p> <p>I will discuss insights into sulfur and oxygen <span class="hlt">isotope</span> fractionations of dissimilatory sulfate reduction and specifically insight provided by experiments with natural populations of sulfate-reducing bacteria from Faellestrand, Denmark. The experiments yielded relatively large magnitude sulfur <span class="hlt">isotope</span> fractionations for dissimilatory sulfate reduction (up to approximately 45 ‰ for 34S/32S), with higher δ18O accompanying higher δ34S, similar to that observed in previous <span class="hlt">studies</span>. The seawater used in the experiments was spiked by addition of 17O-labelled water and the 17O content of residual sulfate was found to depend on the fraction of sulfate reduced in the experiments. The 17O data provides evidence for recycling of sulfur from metabolic intermediates and for an 18O/16O fractionation of ~25-30 ‰ for dissimilatory sulfate reduction, a magnitude that is consistent with <span class="hlt">isotopic</span> exchange between a sulfite species and cell water. The molar ratio of oxygen exchange to sulfate reduction was found to be about 2.5. Using recent models of sulfur <span class="hlt">isotope</span> fractionations we find that our combined sulfur and oxygen <span class="hlt">isotopic</span> data places constraints on the proportion of sulfate recycled to the medium (78-96 %), the proportion of sulfur intermediate sulfite that was recycled by way of APS to sulfate and released back to the external sulfate pool (~70%) and also that a fraction of the sulfur intermediates between sulfite and sulfide were recycled to sulfate. These parameters can be constrained because of the independent information provided by δ18O, δ34S, 17O labels, and Δ33S.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.6152S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.6152S&link_type=ABSTRACT"><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://www.ncbi.nlm.nih.gov/pubmed/22148182','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22148182"><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://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Misra, Superb K; Dybowska, Agnieszka; Berhanu, Deborah; Croteau, Marie Noële; Luoma, Samuel N; Boccaccini, Aldo R; Valsami-Jones, Eugenia</p> <p>2012-01-17</p> <p>This work presents results on synthesis of <span class="hlt">isotopically</span> enriched (99% (65)Cu) copper oxide nanoparticles and its application in ecotoxicological <span class="hlt">studies</span>. (65)CuO 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 μg/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). PMID:22148182</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://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://adsabs.harvard.edu/abs/2012EGUGA..14.6116M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.6116M"><span id="translatedtitle">Fluid inclusion stable <span class="hlt">isotopes</span> and clumped <span class="hlt">isotopes</span> thermometry <span class="hlt">study</span> of Eastern Mediterranean paleoclimate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matthews, A.; Bar-Matthews, M.; Affek, H. P.; Ayalon, A.; Vonhof, H. B.; Zaarur, S.; Burstyn, Y.</p> <p>2012-04-01</p> <p>Fluid inclusion (FI) stable <span class="hlt">isotopes</span> and clumped <span class="hlt">isotopes</span> thermometry provide powerful tools for reconstructing paleoclimates using speleothems. Clumped <span class="hlt">isotopes</span> thermometry is a unique tool for paleotemperature determination using the mass 47 anomaly (Δ47), but its application to speleothems is complicated by the occurrence of a kinetic <span class="hlt">isotope</span> effect (KIE) that accompanies CO2 degassing during carbonate precipitation1. Experimental <span class="hlt">studies</span> involving the surface precipitation of synthetic calcite2 provide a Δ47 thermometer calibration that takes KIE into account and allows its direct application to speleothems. Complementary, the δDw and δ18Ow values of speleothem FI provide an important proxy for cave water-rainfall paleo-hydrological conditions, together with the data required for construction of the meteoric water line (MWL) relationship. Until recently the main <span class="hlt">studied</span> parameter is δDw, and the reliability of FI δ18Ow has been questioned because of the possibility of post-depositional <span class="hlt">isotope</span> exchange with the surrounding calcite. When speleothem calcite δ18Occ is measured, Δ47 temperatures allow δ18Ow to be independently calculated using the calcite-water fractionation relationship. Methods for FI analysis using crushing in a helium stream, TC/EA and continuous flow mass spectrometry (Amsterdam system3) enable both δDw and δ18Ow to be determined, thus allowing measured δ18Ow values to be compared with those calculated from Δ47 temperatures and δ18Occ. We apply these methodologies to paleoclimate <span class="hlt">study</span> in the Eastern Mediterranean (EM) region during the last 150 ky: in the Soreq Cave from the glacial stage 6 to the last interglacial stage 5e and the last glacial maximum (LGM) to the Holocene, and to the Alpine karst system of the Hermon mountain range (MS) cave4 during the last interglacial and brief warm intervals during the last glacial. Soreq Cave Δ47 data show temperature minima at the termination of stage 6 and the LGM, but the LGM</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="http://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=155446&keyword=porto&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=61462522&CFTOKEN=26732161','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=155446&keyword=porto&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=61462522&CFTOKEN=26732161"><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://adsabs.harvard.edu/abs/2014ChPhB..23a3202Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ChPhB..23a3202Z"><span id="translatedtitle">Theoretical <span class="hlt">study</span> on <span class="hlt">isotope</span> separation of an ytterbium atomic beam by laser deflection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Min; Xu, Xin-Ye</p> <p>2014-01-01</p> <p><span class="hlt">Isotope</span> separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one-dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different <span class="hlt">isotopes</span> like 172Yb,173Yb, and 174Yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are <span class="hlt">studied</span>, and the optimal parameters for the <span class="hlt">isotope</span> separation are also investigated. Furthermore, the <span class="hlt">isotope</span> separation efficiency and purity are estimated. Finally a new scheme for the efficient <span class="hlt">isotope</span> separation is proposed. These findings will give a guideline for simply obtaining pure <span class="hlt">isotopes</span> of various elements.</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://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('http://adsabs.harvard.edu/abs/2009EGUGA..1111219L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111219L"><span id="translatedtitle">Water <span class="hlt">isotopes</span> and the Eocene. A tectonic sensitivity <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>Legrande, A. N.; Roberts, C. D.; Tripati, A.; Schmidt, G. A.</p> <p>2009-04-01</p> <p>The early Eocene (54 Million years ago) is one of the warmest periods in the last 65 Million years. Its climate is postulated to have been the result of enhanced greenhouse gas concentration, with CO2 roughly 4 times pre-industrial and methane 7 times pre-industrial concentrations. One interesting feature of this period to emerge recently is the intermittent presence of fossilized Azolla, a type of freshwater fern, in the Arctic Ocean. Synchronous (within dating error) with this appearance were major changes in the restriction of the Arctic Ocean and the other global oceans. We investigate this time period using the Goddard Institute for Space <span class="hlt">Studies</span> ModelE-R, a fully coupled atmosphere-ocean general circulation model that incorporates water <span class="hlt">isotopes</span> throughout the hydrologic cycle, making it an ideal model to test hypotheses of past climate change and to compare to paleoclimate proxy data. We assess the impact of tectonic variability by using minimal and maximal levels of restriction for the Arctic Ocean seaways. We find that the modulation of connectivity of these basins dramatically alters global salinity distribution, leading to large changes in ocean circulation. Greater restriction of the Arctic Basin is associated with fresh and relatively warmer conditions. The same mechanisms responsible for this redistribution of salt also change the global distribution of water <span class="hlt">isotopes</span>, and can alias (water <span class="hlt">isotope</span>) proxy climate signals of warmth.</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/2014DokES.459.1429S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DokES.459.1429S"><span id="translatedtitle">New <span class="hlt">isotopic</span> data for Mid-Atlantic Ridge basalts from the Arkhangelsk-Sierra Leone fracture zone (central Atlantic)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skolotnev, S. G.</p> <p>2014-11-01</p> <p>This <span class="hlt">study</span> presents <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotopic</span> data for basalts collected from the MAR axis between the Arkhangelsk transform fault and 5° N. The <span class="hlt">isotopic</span> data for basalts from the MAR segment between the Arkhangelsk and Vernadsky faults indicate the presence of N-MORB depleted tholeiites, which are similar to some basalts from the MAR segment between the Cape Verde and Marathon faults, at the location of the 14° N geochemical anomaly. Broad positive along-axis gradients in <span class="hlt">isotopic</span> values (and negative for 143Nd/144Nd) are observed from south to north, superimposed by <span class="hlt">isotopic</span> variations in the 9.6° N anomalous basalts. A north-south increase in (La/Sm) n suggests a smaller degree of partial melting. The range of <span class="hlt">isotopic</span> variations in basalts south of the Bogdanov fault is similar to that of basalts recovered at the more southerly 1.7° N anomaly. P-MORB compositions with a large proportion of the HIMU-like component are widely distributed in the vicinity of the 5.4° N rise. The <span class="hlt">isotopic</span> ratios decrease gradually (with increasing 143Nd/144Nd) farther to the north toward the Bogdanov transform fault. A similar trend is observed for (La/Sm) n . Therefore, the basalts recovered to the south and north of Bogdanov fault have different sources of radiogenic <span class="hlt">isotope</span> enrichment: 5.4° N and 9.6° N rises. Basalts recovered to the north of the Vernadsky transform fault have higher 143Nd/144Nd and lower 206Pb/204Pb at similar 87Sr/86Sr ratios. We conclude that the localized manifestations of enriched basalts with <span class="hlt">isotopic</span> characteristics close to the HIMU-like plume-derived component, including the 14° N and 1.7° N geochemical anomalies, may have been formed by microplumes entrained at the base of the upper mantle by asthenospheric mantle flows arranged into a system of cylindrical convective cells, 450-500 km in diameter. Northward of the Bogdanov transform, the upper mantle is contaminated with lower continental crust material, which was entrained during tectonic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.2463K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.2463K&link_type=ABSTRACT"><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.ncbi.nlm.nih.gov/pubmed/1910520','PUBMED'); return false;" href="http://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="http://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. PMID:1910520</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> </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/cgi-bin/nph-data_query?bibcode=2015AGUFMDI31A2567L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFMDI31A2567L&link_type=ABSTRACT"><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/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://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> <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="http://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/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('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://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://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/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://adsabs.harvard.edu/abs/2012JAESc..49..175Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAESc..49..175Z"><span id="translatedtitle">Source, evolution and emplacement of Permian Tarim Basalts: Evidence from U-Pb dating, <span class="hlt">Sr-Nd</span>-Pb-Hf <span class="hlt">isotope</span> systematics and whole rock geochemistry of basalts from the Keping area, Xinjiang Uygur Autonomous region, northwest China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Dayu; Zhou, Taofa; Yuan, Feng; Jowitt, Simon M.; Fan, Yu; Liu, Shuai</p> <p>2012-04-01</p> <p>Permian basalts distribute at least 250,000 km2, and underlie the southwest Tarim Basin in Xinjiang Uygur Autonomous region, northwest China. This vast accumulation of basalt is the main part of the Tarim Large Igneous Province (LIP). The basaltic units in the Lower Permian Kupukuziman and Kaipaizileike Formations in the Keping area, Tarim Basin; were the best exposure of the Permian basalt sequence in the basin. LA-ICP-MS U-Pb dating of zircon from the basal basaltic unit in the section gives an age of 291.9 ± 2.2 Ma (MSWD = 0.30, n = 17); this age, combined with previously published geochronological data, indicates that the basalts in the Tarim Basin were emplaced between 292 Ma and 272 Ma, with about 90% of the basalts being emplaced between 292 and 287 Ma. Basalts from the Keping area have high FeOT (10.8-18.6 wt.%), low Mg#s (0.26-0.60), and exhibit primitive mantle normalized patterns with positive Pb, P and Ti but negative Zr, Y and Ta anomalies. The basalts from both formations have similar 206Pb/204Pb (18.192-18.934), 207Pb/204Pb (15.555-15.598) and 208Pb/204Pb (38.643-38.793) ratios. The basalts also have high ɛSr(t) (45.7-62.1), low ɛNd(t) (-3.6 to -2.2) and low zircon ɛHf(t) (-4.84 to -0.65) values. These characteristics are typical of alkali basalts and suggest that the basalts within the Tarim Basin were derived from an OIB-type mantle source and interacted with enriched mantle (EMI-type) before emplacement. Rare earth element systematics indicate that the parental melts for the basalts were high-degree partial melts derived from garnet lherzolite mantle at the base of the lithosphere. Prior to emplacement, the Tarim Permian Basalts (TPB) underwent fractional crystallization and assimilated crustal material; the basalts were finally emplaced during crustal extension in an intra-plate setting. The wide distribution, deep source and high degree partial melting of the TPB was consistent with a mantle plume origin. The TPB and other coeval igneous rocks in the Tarim Basin constitute a Permian LIP formed by a mantle plume in a similar fashion to the plume-related Emeishan LIP in southwest China.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016IJEaS.tmp...50Q&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016IJEaS.tmp...50Q&link_type=ABSTRACT"><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/cgi-bin/nph-data_query?bibcode=2016JAESc.127..137Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JAESc.127..137Z&link_type=ABSTRACT"><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://adsabs.harvard.edu/abs/2013MinPe.107..739T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MinPe.107..739T"><span id="translatedtitle">Field, geochemistry and <span class="hlt">Sr-Nd</span> <span class="hlt">isotopes</span> of the Pan-African granitoids from the Tifnoute Valley (Sirwa, Anti-Atlas, Morocco): a post-collisional event in a metacratonic setting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toummite, A.; Liegeois, J. P.; Gasquet, D.; Bruguier, O.; Beraaouz, E. H.; Ikenne, M.</p> <p>2013-10-01</p> <p>In the Tifnoute Valley, three plutonic units have been defined: the Askaoun intrusion, the Imourkhssen intrusion and the Ougougane group of small intrusions. They are made of quartz diorite, granodiorite and granite and all contain abundant mafic microgranular enclaves (MME). The Askaoun granodiorite and the Imourkhssen granite have been dated by LA-ICP-MS on zircon at 558 ± 2 Ma and 561 ± 3 Ma, respectively. These granitic intrusions are subcontemporaneous to the widespread volcanic and volcano-detrital rocks from the Ouarzazate Group (580-545 Ma), marking the post-collisional transtensional period in the Anti-Atlas and which evolved towards alkaline and tholeiitic lavas in minor volume at the beginning of the Cambrian anorogenic intraplate extensional period. Geochemically, the Tifnoute Valley granitoids belong to an alkali-calcic series (high-K calc-alkaline) with typical Nb-Ta negative anomalies and no alkaline affinities. Granitoids and enclaves display positive ɛNd-560Ma (+0.8 to +3.5) with young Nd-TDM between 800 and 1200 Ma and relatively low 87Sr/86Sr initial ratios (Sri: 0.7034 and 0.7065). These values indicate a mainly juvenile source corresponding to a Pan-African metasomatized lithospheric mantle partly mixed with an old crustal component from the underlying West African Craton (WAC). Preservation in the Anti-Atlas of pre-Pan-African lithologies (c. 2.03 Ga basement, c. 800 Ma passive margin greenschist-facies sediments, allochthonous 750-700 Ma ophiolitic sequences) indicates that the Anti-Atlas lithosphere has not been thickened and was never an active margin during the Neoproterozoic. After a transpressive period, the late Ediacaran period (580-545 Ma) is marked by movement on near vertical transtensional faults, synchronous with the emplacement of the huge Ouarzazate Group and the Tifnoute Valley granitoids. We propose here a geodynamical model where the Tifnoute Valley granitoids as well as the Ouarzazate Group were generated during the post-collisional metacratonic evolution of the northern boundary of the West African craton. The convergence with the peri-Gondwanan active margin produced brittle fracturing of the cratonic boundary without thickening, allowing rising of magmas. The Tifnoute Valley granitoids display a metasomatized lithospheric mantle source mixed with a minor ancient (2 Ga) continental crust component from the underlying WAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.V51A1467B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.V51A1467B"><span id="translatedtitle">The Heterogeneous Hawaiian Lithosphere: New <span class="hlt">Isotope</span> Data From Kauai and Oahu Peridotites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bizimis, M.; Salters, V. J.; Sen, G.; Keshav, S.; Ducea, M.</p> <p>2005-12-01</p> <p>The Hf-Os <span class="hlt">isotope</span> systematics of peridotites from Oahu suggest that the Hawaiian lithosphere is highly heterogeneous. We found that many Salt Lake Crater (SLC) peridotites vent are fragments of > 500Ma old recycled depleted lithosphere brought to the surface by the Hawaiian plume. In contrast, peridotites from the Pali vent have Hf-Os compositions appropriate for the 90 Ma old Pacific lithosphere. Here we present additional <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span>, major and trace element data from peridotites from the island of Kauai and from Salt Lake Crater and Pali vents on Oahu, in order to further constrain the extent and origin of the heterogeneity observed in the Hawaiian lithosphere. Two Kauai peridotites overlap the Koloa Volcanics post erosional lava compositions in <span class="hlt">Sr-Nd</span> <span class="hlt">isotope</span> space. A third Kauai peridotite has higher 87Sr/86Sr (0.70422) and lower 143Nd/144Nd (0.51291) than any published Kauai lavas and extends towards more radiogenic Sr (for a given Nd) than the Hawaiian lavas in general. This sample has depleted characteristics with high Mg# (0.925) and Cr# (0.311), and low HREE in cpx. It also has the highest La/Yb ratio and largest Ti depletions we have yet determined in Hawaiian peridotites. In contrast, three peridotites from SLC have less radiogenic 87Sr/86Sr (0.70316-0.70334), for a given 143Nd/144Nd (0.51285-0.51278) than all other analyzed peridotites and Hawaiian lavas. One peridotite straddles the proposed LoNd array thought to represent mixing between HIMU and EM-I mantle endmember components. In Hf-Nd space, this sample falls below the Hawaiian lava array having lower 176Hf/177Hf (0.28287) than even the most <span class="hlt">isotopically</span> enriched Koolau lavas. Our new peridotite data show a much greater Sr and Nd <span class="hlt">isotope</span> variability than previously observed, and support our conclusions based on the Hf-Os systematics for a highly heterogeneous lithosphere. The incompatible nature of Sr and Nd in peridotites makes them very susceptible to metasomatic overprint but the observed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V51A2640P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V51A2640P"><span id="translatedtitle">Oxygen <span class="hlt">Isotopes</span> in Intra-Back Arc Basalts from the Andean Southern Volcanic Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parks, B. H.; Wang, Z.; Saal, A. E.; Frey, F. A.; Blusztajn, J.</p> <p>2013-12-01</p> <p>The chemical compositions of volcanic rocks from the Andean Southern Volcanic Zone (SVZ) reflect complex and dynamic interactions among the subducting oceanic lithosphere, the mantle wedge, and the overlying continental crust. Oxygen <span class="hlt">isotope</span> ratios of olivine phenocrysts can be a useful means to identifying their relative contributions to the arc magmatism. In this <span class="hlt">study</span>, we report high-precision oxygen-<span class="hlt">isotope</span> ratios of olivine phenocrysts in a set of intra-back arc basalts from the SVZ. The samples were collected from monogenetic cinder cones east of the volcanic front (35-39 degrees S), and have been geochemically well-characterized with major and trace element contents, and <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotope</span> compositions. Compared to lavas from the volcanic front, these intra-back arc lavas have similar radiogenic <span class="hlt">isotope</span>, and a more alkalic and primitive (higher MgO content) chemical composition. We determined the oxygen-<span class="hlt">isotope</span> ratios using the CO2-laser-fluorination method set up at the Department of Geology and Geophysics, Yale University following the techniques reported in Wang et al (2011). The samples were analyzed with standards of Gore Mountain Garnet (5.77×0.12‰ 1σ; Valley et al., 1995) and Kilbourne Hole Olivine (5.23×0.07‰ 1σ; Sharp, 1990) in order to account for minor changes in the vacuum line during analyses. The obtained δ18OSMOW values of olivine phenocrysts from the intra-back arc basalts vary from 4.98×0.01 to 5.34×0.01‰. This range, surprisingly, is similar to the δ18O values of olivines from mantle peridotites (5.2×0.2‰). Preliminary results indicate significant correlations of 87Sr/86Sr, 143Nd/144Nd and trace element ratios of the basaltic matrix with the δ18O values of olivine phenocrysts, indicating at least three components involved in the formation of the arc volcanism. By comparing the δ18O with the variations of major and trace element contents (e.g., MgO, TiO2 and Ni), and trace element ratios (e.g. Ba/Nb), we evaluate the effects</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('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/cgi-bin/nph-data_query?bibcode=2015BGeo...12.3289K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015BGeo...12.3289K&link_type=ABSTRACT"><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/2060/19880012217','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://adsabs.harvard.edu/abs/2007AGUFM.B52A..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.B52A..04S"><span id="translatedtitle">Culture <span class="hlt">Studies</span> of Nitrogen and Oxygen <span class="hlt">Isotope</span> Effects Associated with Nitrate Assimilation and Denitrification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigman, D. M.; Granger, J.; Lehmann, M. F.; Difiore, P. J.; Tortell, P. D.</p> <p>2007-12-01</p> <p>The <span class="hlt">isotope</span> effects of nitrate-consuming reactions such as nitrate assimilation and denitrification are potential indicators of the physiological state of the organisms carrying out these reactions. Moreover, an understanding of these <span class="hlt">isotope</span> effects is needed to use the stable <span class="hlt">isotopes</span> to investigate the fluxes associated with these reactions in modern and ancient environments. We have used batch cultures to investigate the nitrogen (N) and oxygen (O) <span class="hlt">isotope</span> effects of (1) nitrate assimilation by eukaryotic and prokaryotic algae and by heterotrophic bacteria, and (2) nitrate reduction by denitrifying bacteria. We observe intra- and inter-specific variation in <span class="hlt">isotope</span> effect amplitudes and, in the case of denitrifiers, indications of <span class="hlt">isotope</span> effect decreases during individual nitrate drawdown experiments. However, the measured N and O <span class="hlt">isotope</span> effect ratio is close to 1 for all <span class="hlt">studied</span> organisms, with the exception of an unusual denitrifier (Rhodobacter sphaeroides) that possesses only periplasmic (non-respiratory) nitrate reductase. This observation and other findings are consistent with nitrate reductase being the predominant source of <span class="hlt">isotope</span> fractionation and with most <span class="hlt">isotope</span> effect amplitude variability arising from variable degrees to which nitrate imported into the cell is reduced versus effluxed back into the environment; the more efflux, the more complete the expression of the fractionation imparted by nitrate reduction. If this is the case, then <span class="hlt">isotope</span> effect amplitudes in the field should be related to physiological conditions in the environment, a prediction that, we argue, is supported by recent <span class="hlt">studies</span> of (1) nitrate assimilation in the polar ocean and (2) denitrification in sediment porewaters.</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://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://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=77024027&CFTOKEN=71777072','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=77024027&CFTOKEN=71777072"><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://www.osti.gov/scitech/biblio/20633005','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20633005"><span id="translatedtitle">Systematic AMD+GCM <span class="hlt">Study</span> of Structure of Carbon <span class="hlt">Isotopes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Thiamova, G.; Itagaki, N.; Otsuka, T.; Ikeda, K.</p> <p>2004-02-27</p> <p>The structure of low-lying states of the carbon <span class="hlt">isotopes</span> is investigated using the extended version of the Antisymmetrized Molecular Dynamics (AMD) Multi-Slater Determinant model. We can reproduce reasonably well many experimental data for carbon <span class="hlt">isotopes</span> 12C-22C. A special approach is adopted for 15C to better describe the tail of the wave function.</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://www.osti.gov/scitech/biblio/5598305','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5598305"><span id="translatedtitle">Origin of silicic magma in Iceland revealed by Th <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sigmarsson, O.; Condomines, M. ); Hemond, C. ); Fourcade, S. ); Oskarsson, N. )</p> <p>1991-06-01</p> <p>Th, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and O <span class="hlt">isotopes</span> have been determined in a suite of volcanic rocks from Hekla and in a few samples from Askja and Krafla volcanic centers in Iceland. Although {sup 87}Sr/{sup 86}Sr and {sup 143}Nd/{sup 144}Nd ratios are nearly the same for all compositions at Hekla, the ({sup 230}Th/{sup 232}Th) ratios differ and thus clearly show that the silicic rocks cannot be derived from fractional crystallization of a more primitive magma. Similar results are obtained for the Krafla and Askja volcanic centers, where the {delta}{sup 18}O values are much lower in the silicic magma than in the mafic magma. These data suggest that large volumes of silicic rocks in central volcanoes of the neovolcanic zones in Iceland are produced by partial melting of the underlying crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040089515&hterms=Archaea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DArchaea','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040089515&hterms=Archaea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DArchaea"><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="http://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://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://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://adsabs.harvard.edu/abs/2012AGUFMDI51A2351M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMDI51A2351M"><span id="translatedtitle">Volatiles in melt inclusions and osmium <span class="hlt">isotopes</span> from Hawaiian lavas: investigating the relationship between CO2 and H2O contents with mantle source lithology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marske, J. P.; Hauri, E. H.; Garcia, M. O.; Pietruszka, A. J.</p> <p>2012-12-01</p> <p>Variations in radiogenic <span class="hlt">isotopes</span> (Pb, <span class="hlt">Sr</span>, <span class="hlt">Nd</span>, Hf, He, etc.) and magmatic volatiles (CO2 or H2O) in Hawaiian volcanoes reveal a range of important processes that occur from the source to surface (mantle source heterogeneity, extents of melting, magma transportation, mixing, and storage, and eruption style). Hawaiian lavas are thought to originate from partial melting of a heterogeneous plume source containing a mixture of peridotite and ancient recycled oceanic crust (pyroxenite or eclogite). These lavas display a considerable range in volatile abundances (e.g. <1 to >1000 ppm for Kilauea) that is generally attributed to magmatic degassing or mixing during ascent. However, the source region for Hawaiian volcanoes may also be heterogeneous with respect to volatile concentrations. The effect of shallow degassing makes it difficult to determine if there is a relationship between mantle source composition, lithology, and the volatile budget. We will present Os <span class="hlt">isotopic</span> ratios and volatile contents for over 25 samples from six Hawaiian volcanoes (Koolau, Mauna Kea, Mauna Loa, Hualalai, Kilauea, and Loihi) to determine if pre-eruptive volatiles in shield-stage magmas correlate with the different Hawaiian components (i.e. 'Kea' or 'Loa') and lithologies (i.e. peridotite or pyroxenite) identified by radiogenic <span class="hlt">isotopes</span>. Rapidly-cooled submarine glasses and tephras will be analyzed, as subaerial lavas cool too slowly to prevent diffusive loss of H2O from melt inclusions. Olivine-hosted melt inclusions or groundmass glasses from each eruption will be analyzed for a range of volatiles (CO2, H2O, S, Cl, F). Additionally, olivine separates from each of these samples will be analyzed for Os <span class="hlt">isotopes</span>. This <span class="hlt">study</span> assesses the role of mantle heterogeneity, degree of partial melting, magma transportation, and degassing, in controlling the primary melt volatile concentrations. Although volatile abundances in parental magmas are likely to be modified by variable extents of exsolution</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004LPI....35.1353C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004LPI....35.1353C"><span id="translatedtitle">Coordinated <span class="hlt">Isotopic</span> and TEM <span class="hlt">Studies</span> of Presolar Graphites from Murchison</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Croat, T. K.; Stadermann, F. J.; Zinner, E.; Bernatowicz, T. J.</p> <p>2004-03-01</p> <p>TEM and NanoSIMS investigations of the same presolar Murchison KFC graphites revealed high Zr, Mo, and Ru content in refractory carbides within the graphites. Along with <span class="hlt">isotopically</span> light carbon, these suggest a low-metallicity AGB source.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/726732','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/726732"><span id="translatedtitle">[<span class="hlt">Isotope</span> nephrographic <span class="hlt">studies</span> during hormonal contraception using Depositon].</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Voigt, R; Klinger, G; Stoll, W; Arndt, J</p> <p>1978-01-01</p> <p>By means of <span class="hlt">isotope</span> nephrograms of a total of 29 renally healthy women who had been taken for more than 1 year the drug Deposiston, the renal function is investigated. Checking is done by using the semiquantitative evaluation parameters according to Zum Winkel, Pabst and Hör and to own criteria. Our results show that the highly dosed application of estrogens does not induce significant changes of renal function in the <span class="hlt">isotope</span> nephrogram. PMID:726732</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('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://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://adsabs.harvard.edu/abs/1985JMagR..62..242K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985JMagR..62..242K"><span id="translatedtitle">13 ENDOR <span class="hlt">studies</span> of organic radicals in natural <span class="hlt">isotopic</span> abundance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirste, Burkhard</p> <p></p> <p>13C ENDOR <span class="hlt">studies</span> of phenoxyls, galvinoxyls, triphenylmethyl radicals, nitroxides, and cyclosilane and semiquinone radical anions with natural <span class="hlt">isotopic</span> distribution are reported. The method is described, and it is shown that 13C coupling constants can be measured precisely; in favorable cases even the determination of signs is possible by general TRIPLE resonance. <span class="hlt">Studies</span> of the relaxation behavior of 13C ENDOR signals or measurements of hyperfine shifts in liquid-crystalline solutions yield information about dipolar hyperfine interactions and hence π spin populations which is of aid in assignments to molecular positions. Complete sets of 13C coupling constants have been determined for 2,4,6-tri- tert-butylphenoxyl and Coppinger's radical. For the central carbon atoms of tert-butyl groups, a Q parameter of Qτ-Bu C = -34 MHz is proposed, and for a 29Si atom in trimethylsilyl groups, QTMSSi = +49 MHz. Favorable conditions for natural-abundance 13C ENDOR experiments, e.g., small hyperfine anisotropies and use of deuterated compounds, and limitations of the method are discussed.</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/2015AGUFM.B51A0404S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B51A0404S"><span id="translatedtitle">Use of micrometeorological techniques to <span class="hlt">study</span> the <span class="hlt">isotopic</span> exchange in ecosystems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santos, E.; Wagner-Riddle, C.; Brown, S. E.; Stropes, K.</p> <p>2015-12-01</p> <p>The combination of micrometeorological techniques with high frequency concentration measurements of stable <span class="hlt">isotopes</span> are a powerful tool to <span class="hlt">study</span> the temporal dynamics of <span class="hlt">isotope</span> signatures at the ecosystem level. The objective of this <span class="hlt">study</span> was to <span class="hlt">study</span> the <span class="hlt">isotopic</span> composition of the net CO2 exchange (NEE) above and with corn and tall grass canopies. Profiles of stable <span class="hlt">isotopes</span> of CO2 (12C-CO2, 13C-CO2 and 18O-CO2) were measured using tunable diode laser trace gas analyzers and multiport sampling systems in corn (12C-CO2 and 13C-CO2, only) and tall grass canopies. These measurements were combined with the flux gradient method and Lagrangian dispersion analysis to estimate the <span class="hlt">isotopic</span> signatures of the net CO2 flux. The use of a gradient of a concentration threshold to screen half hourly period improved the estimates of flux signatures by the <span class="hlt">isotope</span> flux ratio approach. The Langrangian dispersion analysis and the <span class="hlt">isotope</span> flux ratio method estimates showed good agreement above the corn canopy, indicating that the former method can be a viable alternative to <span class="hlt">study</span> the <span class="hlt">isotopic</span> exchange within plant canopies. The 13CO2 composition of NEE showed a downward trend near the end of the growing season, which may be related to a reduction of autotrophic respiration in the soil.</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('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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890015080','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890015080"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">study</span> of oxygen diffusion in oxide coatings</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gulino, Daniel A.; Kren, Lawrence A.; Dever, Therese M.</p> <p>1989-01-01</p> <p>Diffusion of oxygen in thin films of silicon dioxide was <span class="hlt">studied</span> using oxygen <span class="hlt">isotopically</span> enriched in oxygen of atomic mass 18 (O-18). This subject is of interest because thin films of dielectrics such as SiO2 are proposed for use as a protective coatings for solar mirrors in low Earth orbit, which is a strongly oxidizing environment. Films of this material were prepared with a direct current magnetron using reactive sputtering techniques. To produce (O-18)- enriched SiO2, a standard 3.5-in.-diameter silicon wafer was reactively sputtered using (O-18)-enriched (95 percent) oxygen as the plasma feed gas. The films were characterized using Rutherford backscattering and Secondary Ion Mass Spectrometer (SIMS) to establish stoichiometry and purity. Subsequently, the films were exposed to an air-derived oxygen plasma in a standard laboratory plasma reactor for durations of up to 10 hr. The concentration ratio of O-16 as a function of depth was determined using SIMS profiling and compared to a baseline, nonplasma exposed sample. A value for the diffusivity of oxygen near the surface of these films was obtained and found to be about 10(-15)sq cm/sec.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Litho.227...57Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Litho.227...57Y"><span id="translatedtitle">In situ zircon Hf-O <span class="hlt">isotopic</span> analyses of late Mesozoic magmatic rocks in the Lower Yangtze River Belt, central eastern China: Implications for petrogenesis and geodynamic evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yan, Jun; Liu, Jianmin; Li, Quanzhong; Xing, Guangfu; Liu, Xiaoqiang; Xie, Jiancheng; Chu, Xiaoqiang; Chen, Zhihong</p> <p>2015-06-01</p> <p>A combined <span class="hlt">study</span> of whole-rock major and trace elements, <span class="hlt">Sr-Nd</span> <span class="hlt">isotopes</span>, zircon U-Pb dating, and in situ zircon Hf-O <span class="hlt">isotopes</span> has been carried out for late Mesozoic magmatic rocks in the Lower Yangtze River Belt. The results provide insights into the origin of mantle sources of magma above a subduction zone, and thus into the petrogenesis of high-K calc-alkaline rocks, shoshonites, and A-type granites on continental margins, and the associated tectonic transformation from a continental arc to a back-arc extensional setting. The late Mesozoic magmatism can be subdivided into three stages: high-K calc-alkaline intrusions (148-133 Ma), shoshonitic rocks (133-127 Ma), and A-type granitoids (127-123 Ma). All the rocks have consistent arc-like trace element characteristics with positive anomalies of Rb, Th, U, Pb, and LREE, negative anomalies of Nb, Ta, and Ti, and enriched <span class="hlt">Sr-Nd</span>-Hf <span class="hlt">isotopic</span> signatures. The first-stage intrusions in the Tongling area usually host dark enclaves of diorite, have high Sr/Y ratios, and low Y contents, and contain zircons with relatively low εHf(t) values (- 38.6 to - 6.6) and high δ18O values (5.7‰ to 10.1‰). A few inherited zircons with Neoarchean to Paleoproterozoic ages and highly enriched Hf <span class="hlt">isotopic</span> compositions were detected in both the host intrusive rocks and the enclaves. The second-stage Ningwu volcanics contain zircons with moderate εHf(t) values (- 13.3 to - 3.8) and elevated δ18O values (5.4‰ to 7.6‰). The third-stage intrusions can be divided into A1- and A2-type granitoids, and their zircons have relatively high δ18O values of 6.7‰ to 10.3‰ and high εHf(t) values of 0 to - 7.9. Based on these geochemical data we drew the following conclusions. Before 148 Ma, following metasomatism by slab-derived fluid/melts, partial melting of the lithospheric mantle produced basaltic magma in the context of a subducting paleo-Pacific plate. This basaltic magma mixed with magma derived from the Archean lower crust, and the</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://www.osti.gov/scitech/biblio/6136926','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6136926"><span id="translatedtitle"><span class="hlt">Isotope</span> dilution <span class="hlt">study</span> of exchangeable oxygen in premium coal samples</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Finseth, D.</p> <p>1987-01-01</p> <p>A difficulty with improving the ability to quantitate water in coal is that truly independent methods do not always exist. The true value of any analytical parameter is always easier to determine if totally independent methods exist to determine that parameter. This paper describes the possibility of using a simple <span class="hlt">isotope</span> dilution technique to determine the water content of coal and presents a comparison of these <span class="hlt">isotope</span> dilution measurements with classical results for the set of Argonne coals from the premium coal sample program. <span class="hlt">Isotope</span> dilution is a widely used analytical method and has been applied to the analysis of water in matrices as diverse as chicken fat, living humans, and coal. Virtually all of these applications involved the use of deuterium as the diluted <span class="hlt">isotope</span>. This poses some problems if the sample contains a significant amount of exchangeable organic hydrogen and one is interested in discriminating exchangeable organic hydrogen from water. This is a potential problem in the coal system. To avoid this potential problem /sup 18/O was used as the diluted <span class="hlt">isotope</span> in this work.</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.ncbi.nlm.nih.gov/pubmed/10489363','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10489363"><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://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mandernack; Bazylinski; Shanks; Bullen</p> <p>1999-09-17</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 (Fe(3)O(4)) by two different species of magnetotactic bacteria at temperatures between 4 degrees and 35 degrees 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 Fe(3)O(4) and water that is consistent with that observed for Fe(3)O(4) produced extracellularly by thermophilic Fe(3+)-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 Fe(3)O(4) 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. PMID:10489363</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., III; 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.ncbi.nlm.nih.gov/pubmed/26446900','PUBMED'); return false;" href="http://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="http://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. PMID:26446900</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://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://pubs.er.usgs.gov/publication/70013973','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70013973"><span id="translatedtitle">The <span class="hlt">isotope</span> systematics of a juvenile intraplate volcano: Pb, Nd, and Sr <span class="hlt">isotope</span> ratios of basalts from Loihi Seamount, 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>Staudigel, H.; Zindler, A.; Hart, S.R.; Leslie, T.; Chen, C.-Y.; Clague, D.</p> <p>1984-01-01</p> <p><span class="hlt">Sr</span>, <span class="hlt">Nd</span>, and Pb <span class="hlt">isotope</span> ratios for a representative suite of 15 basanites, alkali basalts, transitional basalts and tholeiites from Loihi Seamount, Hawaii, display unusually large variations for a single volcano, but lie within known ranges for Hawaiian basalts. Nd <span class="hlt">isotope</span> ratios in alkali basalts show the largest relative variation (0.51291-0.51305), and include the nearly constant tholeiite value ( ??? 0.51297). Pb <span class="hlt">isotope</span> ratios show similarly large ranges for tholeiites and alkali basalts and continue Tatsumoto's [31] "Loa" trend towards higher 206Pb 204Pb ratios, resulting in a substantial overlap with the "Kea" trend. 206Pb 204Pb ratios for Loihi and other volcanoes along the Loa and Kea trends [31] are observed to correlate with the age of the underlying lithosphere suggesting lithosphere involvement in the formation of Hawaiian tholeiites. Loihi lavas display no correlation of Nd, Sr, or Pb <span class="hlt">isotope</span> ratios with major element compositions or eruptive age, in contrast with observations of some other Hawaiian volcanoes [38]. <span class="hlt">Isotope</span> data for Loihi, as well as average values for Hawaiian volcanoes, are not adequately explained by previously proposed two-end-member models; new models for the origin and the development of Hawaiian volcanoes must include mixing of at least three geochemically distinct source regions and allow for the involvement of heterogeneous oceanic lithosphere. ?? 1984.</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=organic+carbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dorganic%2Bcarbon','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720039830&hterms=organic+carbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dorganic%2Bcarbon"><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/cgi-bin/nph-data_query?bibcode=2015AGUFM.V23B3124M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.V23B3124M&link_type=ABSTRACT"><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://www.ncbi.nlm.nih.gov/pubmed/25982821','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25982821"><span id="translatedtitle">Stable <span class="hlt">isotope</span> variations in benthic primary producers along the Bosphorus (Turkey): A preliminary <span class="hlt">study</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Calizza, Edoardo; Aktan, Yelda; Costantini, Maria Letizia; Rossi, Loreto</p> <p>2015-08-15</p> <p>The Bosphorus Strait is a dynamic and complex system. Recent evidences showed nitrogen and heavy metal concentrations to follow opposite patterns across the Strait, suggesting a complex spatial organisation of the anthropogenic disturbance in this system. Here, we provide <span class="hlt">isotopic</span> information on the origin and transportation of dissolved nitrogen along the Bosphorus. C and N <span class="hlt">isotopic</span> and elemental analyses were performed on specimens of Ulva lactuca and associated epiphytes sampled in five locations across the Strait. Variations in C and N <span class="hlt">isotopic</span> signatures were observed in U. lactuca, pointing to a decrease in the availability of anthropogenic organic dissolved nitrogen along a north-south direction. Conversely, epiphytes did not show <span class="hlt">isotopic</span> or elemental patterns across the Strait. These results suggest that preliminary stable <span class="hlt">isotope</span> surveys in extended costal systems basing on U. lactuca can represent a valuable tool to focus meaningful targets and hypotheses for pollution <span class="hlt">studies</span> in the Mediterranean region. PMID:25982821</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhPro..21...13A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhPro..21...13A"><span id="translatedtitle"><span class="hlt">Isotopic</span> <span class="hlt">Study</span> ( 18O, 2H) of the Ground Water in the Bekaa's plain (Lebanon)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Awad, S.</p> <p></p> <p>The stable <span class="hlt">isotopes</span> of the water molecule (18O, 2H) give informations about the paleoclimate existing during the water seepage and about the recharge conditions of the groundwater. The effects of the Orography, the Continentality, and the origin of the masses of air have an effect on the <span class="hlt">isotopic</span> abundance of the precipitations (rain + snow) in Lebanon. An evaporation of the recharge water exists in the atmosphere, with a mixing between the deep water and the shallow ones. The sea water has an <span class="hlt">isotopic</span> abundance at 0 ‰ (SMOW: Standard Mean Ocean Water) for δ2H et δ18O, the Mediterranean Sea is at the origin of the rains which fall on the <span class="hlt">studied</span> area, and which do not keep the <span class="hlt">isotopic</span> abundances of the sea because the high mountains that they cross during their movement. This high altitude causes an impoverishment of the water of the rain on heavy <span class="hlt">isotope</span> (18O).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/188618','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/188618"><span id="translatedtitle">High flux <span class="hlt">isotope</span> reactor cold source preconceptual design <span class="hlt">study</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Selby, D.L.; Bucholz, J.A.; Burnette, S.E.</p> <p>1995-12-01</p> <p>In February 1995, the deputy director of Oak Ridge National Laboratory (ORNL) formed a group to examine the need for upgrades to the High Flux <span class="hlt">Isotope</span> Reactor (HFIR) system in light of the cancellation of the Advanced Neutron Source Project. One of the major findings of this <span class="hlt">study</span> was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. The anticipated cold source will consist of a cryogenic LH{sub 2} moderator plug, a cryogenic pump system, a refrigerator that uses helium gas as a refrigerant, a heat exchanger to interface the refrigerant with the hydrogen loop, liquid hydrogen transfer lines, a gas handling system that includes vacuum lines, and an instrumentation and control system to provide constant system status monitoring and to maintain system stability. The scope of this project includes the development, design, safety analysis, procurement/fabrication, testing, and installation of all of the components necessary to produce a working cold source within an existing HFIR beam tube. This project will also include those activities necessary to transport the cold neutron beam to the front face of the present HFIR beam room. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and research and development (R and D), (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the preconceptual phase and establishes the concept feasibility. The information presented includes the project scope, the preliminary design requirements, the preliminary cost and schedule, the preliminary performance data, and an outline of the various plans for completing the project.</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> </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://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/2011AGUFM.V43C2589V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V43C2589V"><span id="translatedtitle">Geochemical and <span class="hlt">Isotopic</span> Evidences of the Magmatic Sources in the Eastern Sector of the Trans-Mexican Volcanic Belt: Xihuingo-Chichicuautla Volcanic Field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valadez, S.; Martinez-serrano, R.; Juarez-Lopez, K.; Solis-Pichardo, G.; Perez-Arvizu, O.</p> <p>2011-12-01</p> <p>The <span class="hlt">study</span> of magmatism in the Trans-Mexican Volcanic Belt (TMVB) has great importance due to several features such as its obliquity with respect to the Middle American Trench and its petrological and geochemical variability, which are not common in most typical volcanic arcs. Although several papers have contributed significantly to the understanding of most important magmatic processes in this province, there are still several questions such as the characterization of magmatic sources. In the present work, we provide new stratigraphic, petrographic, geochemical and <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Pb <span class="hlt">isotopic</span> data as well as some K-Ar age determinations from the Xihuingo-Chichicuautla volcanic field (XCVF), located at the eastern part of the TMVB, with the aim to identify the magmatic sources that produced the main volcanic rocks. The volcanic structures in the XCVF are divided in two main groups according to the petrographic and geochemical compositions: 1) dacitic domes, andesitic lava flows and some dacitic-rhyolitic ignimbrites and 2) scoria cones, shield volcanoes and associated lava flows of basalt to basaltic-andesite composition. Distribution of most volcanic structures is probably controlled by NE-SW fault and fractures system. This fault system was <span class="hlt">studied</span> by other authors who established that volcanic activity started ca. 13.5 Ma ago, followed by a volcanic hiatus of ca. 10 Ma, and the late volcanic activity began ca. 3 to 1 Ma. In this work we dated 2 rock samples by K-Ar method, which yielded ages of 402 and 871 Ka, which correspond to the most recent volcanic activity in this <span class="hlt">study</span> area. The volcanic rocks of the XCVF display compositions from basalts to rhyolites but in general all rocks show trace element patterns typical of magmatic arcs. However, we can identify two main magmatic sources: a depleted magmatic source represented by dacitic-andesitic rocks which present a LILE enrichment with respect to HFSE indicating that a magmatic source was modified by fluids</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://ntrs.nasa.gov/search.jsp?R=19810048177&hterms=Depleted+Uranium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DDepleted%2BUranium','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19810048177&hterms=Depleted+Uranium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DDepleted%2BUranium"><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('http://www.osti.gov/scitech/servlets/purl/5263900','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5263900"><span id="translatedtitle"><span class="hlt">Study</span> of the charge radii of the stable lead <span class="hlt">isotopes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Borchert, G.L.; Schult, O.W.B.; Speth, J.; Hansen, P.G.; Jonson, B.; Ravn, H.; McGrory, J.B.</p> <p>1982-01-01</p> <p><span class="hlt">Isotope</span> shifts have been measured of the K/sub ..cap alpha..l/ x-ray lines emitted after photo ionization of /sup 204/Pb, /sup 206/Pb, /sup 207/Pb and /sup 208/Pb samples. The results are compared with theoretical values for delta < r/sup 2/> calculated with a microscopic model. The x-ray shift data are also compared with optical data and the nuclear parameters lambda derived from electron scattering results.</p> </li> <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/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.ncbi.nlm.nih.gov/pubmed/22218183','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22218183"><span id="translatedtitle">Strontium <span class="hlt">isotope</span> <span class="hlt">study</span> of coal utilization by-products interacting with environmental waters.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Spivak-Birndorf, Lev J; Stewart, Brian W; Capo, Rosemary C; Chapman, Elizabeth C; Schroeder, Karl T; Brubaker, Tonya M</p> <p>2012-01-01</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 ((87)Sr/(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-(87)Sr/(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. PMID:22218183</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=289438','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=289438"><span id="translatedtitle">A hydrogen gas-water equilibration method produces accurate and precise stable hydrogen <span class="hlt">isotope</span> ratio measurements in nutrition <span class="hlt">studies</span></span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Stable hydrogen <span class="hlt">isotope</span> methodology is used in nutrition <span class="hlt">studies</span> to measure growth, breast milk intake, and energy requirement. <span class="hlt">Isotope</span> ratio MS is the best instrumentation to measure the stable hydrogen <span class="hlt">isotope</span> ratios in physiological fluids. Conventional methods to convert physiological fluids to ...</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/2008AIPC.1012..389M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AIPC.1012..389M"><span id="translatedtitle"><span class="hlt">Study</span> of dipole excitations and the single particle structure of neutron rich Ni <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>Mahata, K.; Paschalis, S.; Adrich, P.; Aksouh, F.; Aumann, T.; Babilon, M.; Behr, K.-H.; Benlliure, J.; Berg, T.; Boehmer, M.; Boretzky, K.; Brünle, A.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Pramanik, U. Datta; Deveaux, L.; Elvers, M.; Emling, H.; Fernandez-Dominguez, B.; Gorska, M.; Hüller, W.; Ickert, G.; Johansson, H.; Junghans, A.; Karagiannis, C.; Kern, L.; Kiselev, O.; Klimkiewicz, A.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Lindenberg, K.; Litvinov, Y.; Maierbeck, P.; Müller, S.; Nilsson, T.; Nociforo, C.; Palit, R.; Prokopowicz, W.; Rossi, D.; Simon, H.; Sümmerer, K.; Wagner, A.; Walus, W.; Weick, H.; Winkler, M.</p> <p>2008-05-01</p> <p>An experiment was performed using the FRS-LAND setup at GSI to <span class="hlt">study</span> the dipole strength distributions above neutron separation threshold for neutron-rich Ni <span class="hlt">isotopes</span>. Measurements, using the same experimental setup, were also carried out to extract single particle occupancies via knockout reactions to investigate the structure and magicity of the neutron-rich Ni <span class="hlt">isotopes</span>. The status of the data analysis and preliminary results are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhRvB..88n4306L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhRvB..88n4306L"><span id="translatedtitle">Phonon-<span class="hlt">isotope</span> scattering and thermal conductivity in materials with a large <span class="hlt">isotope</span> effect: A first-principles <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>Lindsay, L.; Broido, D. A.; Reinecke, T. L.</p> <p>2013-10-01</p> <p>The interplay between phonon-<span class="hlt">isotope</span> and phonon-phonon scattering in determining lattice thermal conductivities in semiconductors and insulators is examined using an ab initio Boltzmann transport equation approach. We identify materials with large enhancements to their thermal conductivities with <span class="hlt">isotopic</span> purification, known as the <span class="hlt">isotope</span> effect, and we focus in particular on results for beryllium-VI compounds and cubic germanium carbide. We find that germanium carbide and beryllium selenide have very large room temperature <span class="hlt">isotope</span> effects of 450%, far larger than in any other material. Thus, <span class="hlt">isotopic</span> purification in these materials gives surprisingly high intrinsic room temperature thermal conductivities, over 1500 Wm-1 K-1 for germanium carbide and over 600 Wm-1 K-1 for beryllium selenide, well above those of the best metals. In compound semiconductors, a large mass ratio of the constituent atoms and large <span class="hlt">isotope</span> mixture for the heavier atom gives enhanced <span class="hlt">isotope</span> scattering. A frequency gap between acoustic and optic phonons (also due to a large mass ratio) and bunching of the acoustic phonon branches give weak anharmonic scattering. Combined, weak anharmonic phonon scattering and strong <span class="hlt">isotope</span> scattering give a large <span class="hlt">isotope</span> effect in the materials examined here. The physical insights discussed in this work will help guide the efficient manipulation of thermal transport properties of compound semiconductors through <span class="hlt">isotopic</span> modification.</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('http://www.osti.gov/scitech/biblio/6749554','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6749554"><span id="translatedtitle">Stable <span class="hlt">isotope</span> methodology in the pharmacokinetic <span class="hlt">studies</span> of androgenic steroids in humans</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shinohara, Y.; Baba, S. )</p> <p>1990-04-01</p> <p>The use of stable <span class="hlt">isotopically</span> labeled steroids combined with gas chromatography/mass spectrometry (GC/MS) has found a broad application in pharmacologic <span class="hlt">studies</span>. Initially, stable <span class="hlt">isotopically</span> labeled steroids served as the ideal analytic internal standard for GC/MS analysis; however, their in vivo use has expanded and has proven to be a powerful pharmacokinetic tool. We have successfully used stable <span class="hlt">isotope</span> methodology to <span class="hlt">study</span> the pharmacokinetic/bioavailability of androgens. The primary advantage of the technique is that endogenous and exogenous steroids with the same basic structure can be differentiated by using stable <span class="hlt">isotopically</span> labeled analogs. The method was used to examine the pharmacokinetics of testosterone and testosterone propionate, and to clarify the influence of endogenous testosterone. Another advantage of the <span class="hlt">isotope</span> methods is that steroidal drugs can be administered concomitantly in two formulations (e.g., solution and solid dosage). A single set of blood samples serves to describe the time course of the formulations being compared. This stable <span class="hlt">isotope</span> coadministration technique was used to estimate the relative bioavailability of 17 alpha-methyltestosterone. 35 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4101500','PMC'); return false;" href="http://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('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4859758','PMC'); return false;" href="http://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> <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('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=199494','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=199494"><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://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></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...</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://adsabs.harvard.edu/abs/2003AGUFM.B41A..04R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.B41A..04R"><span id="translatedtitle">Are <span class="hlt">Isotope</span> Models of Tree Ring Cellulose Useful for <span class="hlt">Studies</span> on Ecosystem and Climate Change?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roden, J. S.</p> <p>2003-12-01</p> <p>For many years, the carbon, oxygen and hydrogen stable <span class="hlt">isotopes</span> of tree ring cellulose have been used to infer environmental change at ecosystem and global scales. Most climate change <span class="hlt">studies</span> have been based on empirical correlations with measured or inferred meteorological information. Recently, mechanistic models have been developed to interpret and predict the <span class="hlt">isotopic</span> composition of cellulose. These models help clarify what environmental information might be contained in historic cellulose records. Although it is best to test and parameterize these models under controlled environmental conditions, field-testing is also critical since the tremendous variability of environmental factors in natural habitats could obscure important signals. However, field-testing these models can be problematic due to the large number of parameters that need to be estimated. Two <span class="hlt">studies</span> will be presented that test a model that predicts the stable oxygen <span class="hlt">isotope</span> content of cellulose under field conditions. The model adequately accounted for field observations of riparian zone trees at three sites in Arizona, Oregon and Utah that had contrasting <span class="hlt">isotopic</span> and environmental inputs. Although the cellulose model underestimated the oxygen <span class="hlt">isotopic</span> content of tree ring cellulose in a <span class="hlt">study</span> along a transect of decreasing water status in Oregon, it did predict the greatly reduced range in oxygen <span class="hlt">isotope</span> content over the transect. Both <span class="hlt">studies</span> show that ambient humidity plays an important role in modifying the primary signal of meteoric water <span class="hlt">isotopic</span> content in organic matter. Thus, tree ring records could provide important proxy information regarding changes in ecosystem humidity. However, teasing out humidity information may not be trivial due to the number of other factors involved. The use of dual <span class="hlt">isotope</span> records (carbon and oxygen) allow for better interpretation of environmental information since each <span class="hlt">isotope</span> provides different, though related, information regarding ecosystem water</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/cgi-bin/nph-data_query?bibcode=2010EGUGA..12..675B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..12..675B&link_type=ABSTRACT"><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('http://adsabs.harvard.edu/abs/2009AGUFM.V24A..05C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V24A..05C"><span id="translatedtitle"><span class="hlt">Isotopic</span> streaks suggest a stripy plume under the Marquesas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauvel, C.; Blais, S.; Maury, R.; Lewin, E.</p> <p>2009-12-01</p> <p>The Marquesas Islands in Polynesia have several features that are puzzling for a plume-derived island chain: they lie over a superswell; the age progression along the chain does not correspond to the movement of the Pacific plate above a fixed deep plume; and the alignment of the islands differs from the direction of Pacific plate motion. Here we present new trace element and <span class="hlt">isotopic</span> data on Ua Huka Island and we use them, together with data published on the other Marquesas Islands, to constrain the geographical and temporal changes occurring during construction of the archipelago. Ua Huka volcanics have variable and relatively radiogenic <span class="hlt">isotopic</span> compositions with 87Sr/86Sr ranging from 0.70426 to 0.70609, 143Nd/144Nd from 0.51271 and 0.51290, 176Hf/177Hf from 0.28288 and 0.28304 and 206Pb/204Pb from 18.897 to 19.315. The oldest lavas (≈ 2.5-3 Ma) have higher Sr <span class="hlt">isotopic</span> compositions than the youngest lavas (≈ 0.7-1 Ma). These compositions extend the <span class="hlt">Sr-Nd</span> <span class="hlt">isotopic</span> field defined by published data from the Marquesas archipelago to more radiogenic values. Two parallel <span class="hlt">isotopic</span> bands with different Nd <span class="hlt">isotope</span> ratios at the same Sr <span class="hlt">isotopic</span> composition can be recognized in the <span class="hlt">Sr-Nd</span> diagram. The first group includes all islands located north of a line parallel to the 115° direction of plate movement and passing between Hiva Oa and Tahuata. The second group corresponds to the islands located south of this line. The distinction between the two groups extends to Pb <span class="hlt">isotopic</span> compositions in that the southern group has, at a given Nd or Sr <span class="hlt">isotopic</span> composition, more radiogenic Pb <span class="hlt">isotope</span> ratios than the northern islands. Both groups define a very large range of <span class="hlt">isotopic</span> compositions with 87Sr/86Sr varying from 0.703 to 0.706. The presence of two <span class="hlt">isotopic</span> stripes that follow the direction of Pacific plate motion constrains the origin of Marquesas volcanism. The stripes cannot be attributed to interactions with different lithospheres because the oceanic crust</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6490484','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6490484"><span id="translatedtitle">Hydrogen-<span class="hlt">isotope</span> motion in scandium <span class="hlt">studied</span> by ultrasonic measurements</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Leisure, R.G. ); Schwarz, R.B.; Migliori, A. ); Torgeson, D.R. ); Svare, I. )</p> <p>1993-07-01</p> <p>Resonant ultrasound spectroscopy has been used to investigate ultrasonic attenuation in single crystals of Sc, ScH[sub 0.25], and ScD[sub 0.18] over the temperature range of 10--300 K for frequencies near 1 MHz. Ultrasonic-attenuation peaks were observed in the samples containing H or D with the maximum attenuation occurring near 25 K for ScH[sub 0.25] and near 50 K for ScD[sub 0.18]. The general features of the data suggest that the motion reflected in the ultrasonic attenuation is closely related to the low-temperature motion seen in nulcear-magnetic-resonance spin-lattice-relaxation measurements. The ultrasonic results were fit with a two-level-system (TLS) model involving tunneling between highly asymmetric sites. The relaxation of the TLS was found to consist of two parts: a weakly temperature-dependent part, probably due to coupling to electrons; and a much more strongly temperature-dependent part, attributed to multiple-phonon processes. The strongly temperature-dependent part was almost two orders of magnitude faster in ScH[sub 0.25] than in ScD[sub 0.18], in accordance with the idea that tunneling is involved in the motion. Surprisingly, the weakly temperature-dependent part was found to be about the same for the two <span class="hlt">isotopes</span>. The asymmetries primarily responsible for coupling the TLS to the ultrasound are attributed to interactions between hydrogen ions that lie on adjacent [ital c] axes. The results are consistent with an <span class="hlt">isotope</span>-independent strength for the coupling of the TLS to the ultrasound.</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://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('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('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://www.ncbi.nlm.nih.gov/pubmed/25881211','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25881211"><span id="translatedtitle">Methyl-specific <span class="hlt">isotopic</span> labeling: a molecular tool box for solution NMR <span class="hlt">studies</span> of large proteins.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kerfah, Rime; Plevin, Michael J; Sounier, Remy; Gans, Pierre; Boisbouvier, Jerome</p> <p>2015-06-01</p> <p>Nuclear magnetic resonance (NMR) spectroscopy is a uniquely powerful tool for <span class="hlt">studying</span> the structure, dynamics and interactions of biomolecules at atomic resolution. In the past 15 years, the development of new <span class="hlt">isotopic</span> labeling strategies has opened the possibility of exploiting NMR spectroscopy in the <span class="hlt">study</span> of supra-molecular complexes with molecular weights of up to 1MDa. At the core of these <span class="hlt">isotopic</span> labeling developments is the specific introduction of [(1)H,(13)C]-labeled methyl probes into perdeuterated proteins. Here, we describe the evolution of these approaches and discuss their impact on structural and biological <span class="hlt">studies</span>. The relevant protocols are succinctly reviewed for single and combinatorial <span class="hlt">isotopic</span>-labeling of methyl-containing residues, and examples of applications on challenging biological systems, including high molecular weight and membrane proteins, are presented. PMID:25881211</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4048731','PMC'); return false;" href="http://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://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009AGUFM.V54A..02H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009AGUFM.V54A..02H&link_type=ABSTRACT"><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://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/2010AGUFM.T32B..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T32B..04Z"><span id="translatedtitle">Os-Hf <span class="hlt">isotopes</span> of the ultrapotassic rocks in southern Tibet: Significant crustal input into the mantle source region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Z.; Widom, E.; Meng, Q.; Niu, Y.; Zhu, D.; Mo, X.; Barry, T.</p> <p>2010-12-01</p> <p>The post-collisional mafic ultrapotassic (ultra-K) magmatism in the western Lhasa terrane, southern Tibet, has been well-<span class="hlt">studied</span> in the past decade. The model of low-degree partial melting of an enriched subcontinental lithospheric mantle has been proposed to be responsible for the origin of the ultra-K rocks on the basis of trace element and <span class="hlt">Sr-Nd</span>-Pb-O <span class="hlt">isotope</span> data (Miller et al., 1999, J. Petrology; Ding et al., 2003, J. Petrology; Gao et al., 2009, J. Petrology; Zhao et al., 2009, Lithos). Here, we report both Os and Hf <span class="hlt">isotopic</span> data on the same ultra-K samples discussed in Zhao et al. (2009). The rocks have suprachondritic 187Os/188Os (0.1315-0.4828) and sub-chondritic to MORB-like Re/Os ratios (0.019-15.75). In the 187Os/188Os vs. Re/Os plot, the data show a notable trend towards the Himalayan crustal components. The 176Hf/177Hf ratios of 0.282204 to 0.282554 correspond to ɛHf values of -20.1 to -7.9. In the ɛHf vs. ɛNd plot, these mafic ultra-K rocks show strong crustal signatures, similar to, but more enriched than, the lamproites from Spain and Italia (Prelević et al., 2010, Lithos). They also show a linear trend that coincides with the Hf-Nd <span class="hlt">isotopic</span> array defined by igneous rocks, suggesting significant contributions of some mature continental crustal material in their petrogenesis. The radiogenic Os could be interpreted as resulting from crustal assimilation, but more likely reflects increasing contributions from metasomatic components (Schaefer et al., 2000, Geology). Taking together all the trace element data, Os-Hf-Nd data and petrological data, we suggest that the petrogenesis of the mantle xenolith-bearing ultra-K rocks in southern Tibet involves melting of enriched upper mantle whose enrichments may be genetically associated with metasomatism by a melt component derived from subducted Himalayan continental crustal materials.</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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8732R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8732R"><span id="translatedtitle">Can stable <span class="hlt">isotopes</span> ride out the storms? The role of convection for water <span class="hlt">isotopes</span> in models, records, and paleoaltimetry <span class="hlt">studies</span> in the central Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rohrmann, Alexander; Strecker, Manfred R.; Bookhagen, Bodo; Mulch, Andreas; Sachse, Dirk; Pingel, Heiko; Alonso, Ricardo N.; Schilgen, Taylor F.; Montero, Carolina</p> <p>2015-04-01</p> <p>Globally, changes in stable <span class="hlt">isotope</span> ratios of oxygen and hydrogen (δ18O and δD) in the meteoric water cycle result from distillation and evaporation processes. <span class="hlt">Isotope</span> fractionation occurs when air masses rise in elevation, cool, and reduce their water-vapor holding capacity with decreasing temperature. As such, d18O and dD values from a variety of sedimentary archives are often used to reconstruct changes in continental paleohydrology as well as paleoaltimetry of mountain ranges. Based on 234 stream-water samples, we demonstrate that areas experiencing deep convective storms in the eastern south-central Andes (22 - 28° S) do not show the commonly observed relationship between δ18O and δD with elevation. These convective storms arise from intermontane basins, where diurnal heating forces warm air masses upward, resulting in cloudbursts and raindrop evaporation. Especially at the boundary between the tropical and extra-tropical atmospheric circulation regimes where deep-convective storms are very common (~ 26° to 32° N and S), the impact of such storms may yield non-systematic stable <span class="hlt">isotope</span>-elevation relationships as convection dominates over adiabatic lifting of air masses. Because convective storms can reduce or mask the depletion of heavy <span class="hlt">isotopes</span> in precipitation as a function of elevation, linking modern or past topography to patterns of stable <span class="hlt">isotope</span> proxy records can be compromised in mountainous regions, and atmospheric circulation models attempting to predict stable <span class="hlt">isotope</span> patterns must have sufficiently high spatial resolution to capture the fractionation dynamics of convective cells. Rohrmann, A. et al. Can stable <span class="hlt">isotopes</span> ride out the storms? The role of convection for water <span class="hlt">isotopes</span> in models, records, and paleoaltimetry <span class="hlt">studies</span> in the central Andes. Earth Planet. Sci. Lett. 407, 187-195 (2014).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5564714','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5564714"><span id="translatedtitle">Mechanistic <span class="hlt">studies</span> on the bovine liver mitochondrial dihydroorotate dehydrogenase using kinetic deuterium <span class="hlt">isotope</span> effects</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hines, V.; Johnston, M. )</p> <p>1989-02-07</p> <p>Dihydroorotates deuteriated at both C{sub 5} and C{sub 6} have been prepared and used to probe the mechanism of the bovine liver mitochondrial dihydroorotate dehydrogenase. Primary deuterium <span class="hlt">isotope</span> effects on k{sub cat} are observed with both (6RS)-(5(S)-{sup 2}H)- and (6RS)-(6-{sup 2}H)dihydroorotates ({bold 3} and {bold 6}, respectively); these effects are maximal at low pH. At pH 6.6, {sup D}V = 3.4 for the C{sub 5}-deuteriated dihydroorotate ({bold 3}), and {sup D}V = 2.3 for the C{sub 6}-deuteriated compound ({bold 6}). The <span class="hlt">isotope</span> effects approach unity at pH 8.8. Analysis of the pH dependence of the <span class="hlt">isotope</span> effects on k{sub cat} reveals a shift in the rate-determining step of the enzyme mechanism as a function of pH. Dihydroorotate oxidation appears to require general base catalysis; this step is completely rate-determining at low pH and <span class="hlt">isotopically</span> sensitive. Reduction of the cosubstrate, coenzyme Q{sub 6}, is rate-limiting at high pH and is <span class="hlt">isotopically</span> insensitive; this step appears to require general acid catalysis. The results of double <span class="hlt">isotope</span> substitution <span class="hlt">studies</span> and analysis for substrate <span class="hlt">isotope</span> exchange with solvent point toward a concerted mechanism for oxidation of dihydroorotate. This finding serves to distinguish further the mammalian dehydrogenase from its parasitic cognate, which catalyzes a stepwise oxidation reaction.</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> </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('http://www.ncbi.nlm.nih.gov/pubmed/26358909','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26358909"><span id="translatedtitle">Isotopomer Spectral Analysis: Utilizing Nonlinear Models in <span class="hlt">Isotopic</span> Flux <span class="hlt">Studies</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kelleher, Joanne K; Nickol, Gary B</p> <p>2015-01-01</p> <p>We present the principles underlying the isotopomer spectral analysis (ISA) method for evaluating biosynthesis using stable <span class="hlt">isotopes</span>. ISA addresses a classic conundrum encountered in the use of radioisotopes to estimate biosynthesis rates whereby the information available is insufficient to estimate biosynthesis. ISA overcomes this difficulty capitalizing on the additional information available from the mass isotopomer labeling profile of a polymer. ISA utilizes nonlinear regression to estimate the two unknown parameters of the model. A key parameter estimated by ISA represents the fractional contribution of the tracer to the precursor pool for the biosynthesis, D. By estimating D in cells synthesizing lipids, ISA quantifies the relative importance of two distinct pathways for flux of glutamine to lipid, reductive carboxylation, and glutaminolysis. ISA can also evaluate the competition between different metabolites, such as glucose and acetoacetate, as precursors for lipogenesis and thereby reveal regulatory properties of the biosynthesis pathway. The model is flexible and may be expanded to quantify sterol biosynthesis allowing tracer to enter the pathway at three different positions, acetyl CoA, acetoacetyl CoA, and mevalonate. The nonlinear properties of ISA provide a method of testing for the presence of gradients of precursor enrichment illustrated by in vivo sterol synthesis. A second ISA parameter provides the fraction of the polymer that is newly synthesized over the time course of the experiment. In summary, ISA is a flexible framework for developing models of polymerization biosynthesis providing insight into pools and pathway that are not easily quantified by other techniques. PMID:26358909</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://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://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://adsabs.harvard.edu/abs/2014AGUFM.V31A4722G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V31A4722G"><span id="translatedtitle">Molybdenum <span class="hlt">Isotopic</span> Composition of the Archean Mantle As Inferred from <span class="hlt">Studies</span> of Komatiites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greber, N. D.; Puchtel, I. S.; Nagler, T. F.; Mezger, K.</p> <p>2014-12-01</p> <p>Molybdenum <span class="hlt">isotopic</span> composition has been shown to be a powerful tool in <span class="hlt">studies</span> of planetary processes, e.g. estimating core formation temperatures [1,2]. However, Mo <span class="hlt">isotope</span> compositions of terrestrial reservoirs are not well constrained. In order to better constrain the Mo <span class="hlt">isotopic</span> composition of the early Earth's mantle, komatiites from four locations were analyzed for their Mo concentrations and <span class="hlt">isotopic</span> compositions. Komatiites are particularly appropriate for this type of <span class="hlt">study</span> because they formed by high degrees of partial melting of the mantle leading to a complete base metal sulfide removal from the residual mantle and the production of sulfur-undersaturated melts and thus a quantitative removal of Mo from the source into the melt. All samples, except for two strongly altered specimens specifically chosen to <span class="hlt">study</span> the effects of secondary alteration, are very fresh having preserved most of their primary mineralogy. The Mo concentrations in komatiites range from 10 to 120 ng/g. Fresh komatiites have lighter δ98Mo (NIST SRM 3134 = 0.25‰, [3]) than altered samples. The estimated primary Mo <span class="hlt">isotope</span> compositions of the <span class="hlt">studied</span> komatiite melts range from 0.02 ± 0.16‰ to 0.19 ± 0.14‰ and are therefore indistinguishable within analytical uncertainty (2SD) from published values for chondritic meteorites (0.09 ± 0.04 ‰; 2SD; [2]) and lighter than the proposed average for Earth's continental crust (0.3 to 0.4‰ [4]). All data combined, although overlapping in errors, show a consistent trend of lighter δ98Mo and lower Mo concentrations in more melt-depleted mantle sources, indicating incompatible behaviour of Mo and preferential mobilization of heavy Mo <span class="hlt">isotopes</span> during mantle melting. [1] Hin et al. (2013) EPSL, 379 [2] Burkhardt et al. (2014) EPSL, 391 [3] Nägler, et al. (2014) GGR, 38. [4] Voegelin et al. (2014) Lithos, 190-191.</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://adsabs.harvard.edu/abs/2014JChPh.140x4306B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JChPh.140x4306B"><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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berhanu, Tesfaye A.; Meusinger, Carl; Erbland, Joseph; Jost, Rémy; Bhattacharya, S. K.; Johnson, Matthew S.; Savarino, Joël</p> <p>2014-06-01</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 (15N, 17O, and 18O) 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 (δ15N, δ18O, and Δ17O). From these measurements an average photolytic <span class="hlt">isotopic</span> fractionation of 15ɛ = (-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 15ɛ = (-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 14NO3- and 15NO3- in snow at a chosen temperature. The nitrogen <span class="hlt">isotopic</span> fractionations obtained by applying this model under the experimental temperature as well as considering the shift in width and center well</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24985637','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24985637"><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.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berhanu, Tesfaye A; Meusinger, Carl; Erbland, Joseph; Jost, Rémy; Bhattacharya, S K; Johnson, Matthew S; Savarino, Joël</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 ((15)N, (17)O, and (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(15)N, δ(18)O, and Δ(17)O). From these measurements an average photolytic <span class="hlt">isotopic</span> fractionation of (15)ɛ = (-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 (15)ɛ = (-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 (14)NO3 (-) and (15)NO3 (-) in snow at a chosen temperature. The nitrogen <span class="hlt">isotopic</span> fractionations obtained by applying this model under the experimental temperature as well as considering the</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('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://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://www.osti.gov/scitech/servlets/purl/5588600','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5588600"><span id="translatedtitle">Feasibility <span class="hlt">study</span> of plutonium <span class="hlt">isotopic</span> analysis of resin beads by nondestructive gamma-ray spectroscopy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li, T.K.</p> <p>1985-01-01</p> <p>We have initiated a feasibility <span class="hlt">study</span> on the use of nondestructive low-energy gamma-ray spectroscopy for plutonium <span class="hlt">isotopic</span> analysis on resin beads. Seven resin bead samples were measured, with each sample containing an average of 9 ..mu..g of plutonium; the <span class="hlt">isotopic</span> compositions of the samples varied over a wide range. The gamma-ray spectroscopy results, obtained from 4-h counting-time measurements, were compared with mass spectrometry results. The average ratios of gamma-ray spectroscopy to mass spectrometry were 1.014 +- 0.025 for /sup 238/Pu//sup 239/Pu, 0.996 +- 0.018 for /sup 240/Pu//sup 239/Pu, and 0.980 +- 0.038 for /sup 241/Pu//sup 239/Pu. The rapid, automated, and accurate nondestructive <span class="hlt">isotopic</span> analysis of resin beads may be very useful to process technicians and International Atomic Energy Agency inspectors. 3 refs., 1 fig., 3 tabs.</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://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://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://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeCoA.146..164S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeCoA.146..164S&link_type=ABSTRACT"><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://ntrs.nasa.gov/search.jsp?R=20040088750&hterms=Krypton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DKrypton','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040088750&hterms=Krypton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DKrypton"><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> <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> </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('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=197082','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=197082"><span id="translatedtitle">DETERMINING CARBON <span class="hlt">ISOTOPE</span> SIGNATURES FROM MICROMETEOROLOGICAL MEASUREMENTS: IMPLICATIONS FOR <span class="hlt">STUDYING</span> BIOSPHERE-ATMOSPHERE EXCHANGE PROCESSES</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>In recent years considerable effort has been focused on combining micrometeorological and stable <span class="hlt">isotope</span> techniques to elucidate and <span class="hlt">study</span> biosphere-atmosphere exchange processes. At the ecosystem scale, these methods are increasingly being used to address a number of challenging problems, including...</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.ncbi.nlm.nih.gov/pubmed/19219896','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19219896"><span id="translatedtitle">Bronze Age volcanic event recorded in stalagmites by combined <span class="hlt">isotope</span> and trace element <span class="hlt">studies</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Siklósy, Zoltán; Demény, Attila; Vennemann, Torsten W; Pilet, Sebastien; Kramers, Jan; Leél-Ossy, Szabolcs; Bondár, Mária; Shen, Chuan-Chou; Hegner, Ernst</p> <p>2009-03-01</p> <p>Stable <span class="hlt">isotope</span> analyses of speleothems (carbonate deposits formed in caves) have been widely used to reconstruct paleoenvironmental conditions. Recent improvements in geochemical techniques have enabled us to analyze climate-influenced deposits at high temporal resolution so that hitherto unrecognized environmental conditions may be identified. Stable H, C and O <span class="hlt">isotope</span> analyses on carbonate and inclusion water have been combined with multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) age dating and laser-ablation ICP-MS trace element analyses on a stalagmite from southern Hungary. The <span class="hlt">study</span> reveals significant changes in chemical and <span class="hlt">isotopic</span> compositions of the speleothem between approx. 3800 and 3500 years BP ('Before Present') indicating coupled changes in the temperature and precipitation regime under which the speleothem formed. Stable <span class="hlt">isotopic</span> and trace element correlations within this time period correlate with similar <span class="hlt">studies</span> of stalagmites of comparable age from the Alpine-Mediterranean region. Our <span class="hlt">studies</span> suggest that traces of deposition of volcanic dust, possibly related to the Thera eruption of Santorini (Greece) ca. 1650 BC (approximately 3650 BP), and environmental changes can be detected at a distance of several thousand kilometers. PMID:19219896</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24467184','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24467184"><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.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Slysz, Gordon W; Steinke, Laurey; Ward, David M; Klatt, Christian G; Clauss, Therese R W; Purvine, Samuel O; Payne, Samuel H; Anderson, Gordon A; Smith, Richard D; Lipton, Mary S</p> <p>2014-03-01</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(s), a key application will be in situ <span class="hlt">studies</span> of microbial communities for short periods of time under natural 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 phototrophic bacterial mats isolated from Yellowstone National Park. 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. PMID:24467184</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/2009EGUGA..11.6289G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.6289G"><span id="translatedtitle">Pb <span class="hlt">isotopic</span> <span class="hlt">study</span> on soils from Domizio-Flegreo Littoral area, Napoli, Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grezzi, G.; Ayuso, R. A.; Lima, A.; Albanese, S.; de Vivo, B.</p> <p>2009-04-01</p> <p>The Domizio - Flegreo Littoral area, together with the Agro Aversano area, are part of a Site of National Interest for pollution assessment. This area is located along the north coastal zone of the Campania region (Italy) and has an extension of about 855 Km2. We analyzed soils for heavy metal content in order to <span class="hlt">study</span> and discriminate the impact of natural and anthropogenic sources. We collected 292 soil surface samples (5-15 cm depth) and produced maps showing the distribution of heavy metals in the soils. On the basis of the geographic distribution of heavy metals, 9 soil profiles were also collected for detailed examination (1 meter from surface). From each soil profile, we collected 10 soil samples (1/10 cm) in the urban and suburban areas of the littoral area. Also, we collected 8 groundwater samples likely associated with the soils. Pb <span class="hlt">isotope</span> compositions of these soils and waters help to constrain the impact of anthropogenic and natural components on the soil profiles. Possible anthropogenic end-members include pesticides used in the area. Lead <span class="hlt">isotope</span> compositions of soils known to contain anomalously high values of heavy metals were measured in order to determine the sources of the Pb and, by inference, sources of other metals that are likely to share similar geochemical behaviour in the surface environment (e.g., As). Acid-leach compositions of the soils represent Pb that is adsorbed to mineral surfaces, whereas residue compositions may reflect bedrock. Labile Pb (acid-leach fractions) from the soils shows a range in compositions of 207Pb/206Pb = 0.8275 to 0.8486, and 208Pb/206Pb = 2.0488 to 2.0873. The <span class="hlt">isotope</span> values vary and decrease with depth. The Pb <span class="hlt">isotope</span> ratios obtained on groundwater samples range from about 207Pb/206Pb = 0.8516 to 0.8636, 208Pb/206Pb = 2.0706 to 2.1064. The Pb <span class="hlt">isotope</span> ratios in the soil profiles and groundwater are generally consistent with multiple sources that include anthropogenic Pb. Surface soil samples from Giugliano</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/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://www.ncbi.nlm.nih.gov/pubmed/11077928','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11077928"><span id="translatedtitle"><span class="hlt">Isotope</span> <span class="hlt">studies</span> of hydrogen and oxygen in ground ice-experiences with the equilibration technique.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Meyer, H; Schönicke, L; Wand, U; Hubberten, H W; Friedrichsen, H</p> <p>2000-01-01</p> <p>Equilibration technique suitable for a large amount of samples is described for hydrogen and oxygen <span class="hlt">isotope</span> analyses of ground ice, especially ice wedges, including the sampling strategy and the analytical procedure as well as the calibration of the Finnigan MAT Delta-S mass spectrometer in June, 1999. Since for future analyses of ice wedges, a higher sampling resolution with limited sample volume is required, the limit of the equilibration technique for small water sample sizes of between 0.05 and 5 ml was checked. For water samples smaller than 1 ml, corresponding to a molar ratio [H2O]/[H2] of smaller than 0.994, a balance correction has to be applied. The experimental errors due to partial evaporation during evacuation, the balance calculation of the <span class="hlt">isotope</span> equilibration process, the linearity as well as memory effects of the mass spectrometer for samples with large differences in delta18O and deltaD are tackled in this paper. In the polar regions of Northern Siberia without Late Pleistocene and Holocene glaciation, ground ice is used as an archive for paleoclimate <span class="hlt">studies</span>. First results of stable <span class="hlt">isotope</span> measurements on ice wedges clearly show a shift towards heavier <span class="hlt">isotopes</span> and thus warmer winter temperatures as well as a change in the source of the precipitation between Late Pleistocene and Holocene. These results indicate the high potential of ground ice for paleoclimate <span class="hlt">studies</span>. PMID:11077928</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., Jr.; 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.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="http://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/cgi-bin/nph-data_query?bibcode=2016Geomo.259..134C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Geomo.259..134C&link_type=ABSTRACT"><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/cgi-bin/nph-data_query?bibcode=2014Litho.202..363W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014Litho.202..363W&link_type=ABSTRACT"><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/2014EGUGA..16.1538G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.1538G"><span id="translatedtitle">Carbon allocation in plants and ecosystems - insights from stable <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>Gessler, Arthur</p> <p>2014-05-01</p> <p>Trees are large global stores of carbon (C) that will be impacted by increased carbon dioxide levels and climate change. However, at present we cannot properly predict the carbon balance of forests in future as we lack knowledge on how plant physiological processes, the transfer of carbon within the plant, carbon storage, and remobilization in the plant tissues as well as the release of carbon from the roots to the soil interact with environmental drivers and ecosystem-scale processes. This paper will summarise how stable <span class="hlt">isotope</span> techniques can give new insights in the fate of newly assimilated C in plants and ecosystems on time scales from hours to seasons and it will include <span class="hlt">studies</span> either characterizing temporal and spatial variation in the natural abundance of carbon and oxygen <span class="hlt">isotopes</span> or applying <span class="hlt">isotopically</span> enriched tracers. It comprises the assessment of the mechanisms of C partitioning among specific metabolic pathways, between plant organs and into various ecosystem C pools with different residence times. Moreover stable <span class="hlt">isotopes</span> are highly suitable tools to characterise the role of the phloem, which is the central long-distance conveyer distributing C from source to sinks and thus plays a central role in linking sites and structures of storage, growth and other metabolic activities. A deeper understanding of these processes and their interaction with environmental drivers is critical for predicting how trees and ecosystems will respond to coming global environmental changes, including increased temperature, altered precipitation, and elevated carbon dioxide concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JNuM..469..133M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JNuM..469..133M"><span id="translatedtitle">In situ NRA <span class="hlt">study</span> of hydrogen <span class="hlt">isotope</span> exchange in self-ion damaged tungsten exposed to neutral atoms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Markelj, S.; Založnik, A.; Schwarz-Selinger, T.; Ogorodnikova, O. V.; Vavpetič, P.; Pelicon, P.; Čadež, I.</p> <p>2016-02-01</p> <p><span class="hlt">Isotope</span> exchange was <span class="hlt">studied</span> in-situ by Nuclear Reaction Analysis in the bulk of self-ion damaged tungsten at 600 K. Both variations of <span class="hlt">isotope</span> exchange of H by D and of D by H were measured. The deuterium isothermal desorption was also <span class="hlt">studied</span> and evaluated in order to be able to resolve the self-desorption from the <span class="hlt">isotope</span> exchange at 600 K. The <span class="hlt">isotope</span> exchange was also <span class="hlt">studied</span> on the surface by Elastic Recoil Detection Analysis at 480 K and 380 K. The exchange mechanism was effective both on the surface and in the bulk of damaged tungsten. A simple model was introduced to describe the exchange efficiency on the surface and in the bulk obtaining the exchange cross sections on the surface and in bulk. In both cases an <span class="hlt">isotope</span> effect was observed, where the exchange of H atoms by D atoms was more efficient than for the reverse sequence.</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/2014JAESc..84..188R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAESc..84..188R"><span id="translatedtitle">A common parentage for Deccan Continental Flood Basalt and Central Indian Ocean Ridge Basalt? A geochemical and <span class="hlt">isotopic</span> approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ray, D.; Misra, S.; Widdowson, M.; Langmuir, C. H.</p> <p>2014-04-01</p> <p>A comparison of geochemical and <span class="hlt">Sr-Nd</span>-Pb <span class="hlt">isotopic</span> compositions for Deccan Continental Flood Basalts (CFBs) and Central Indian Ridge (CIR) Basalts is presented: these data permit assessment of possible parental linkages between the two regions, and comparison of their respective magmatic evolutionary trends in relation to rift-related tectonic events during Gondwana break-up. The present <span class="hlt">study</span> reveals that Mid-Ocean Ridge Basalt (MORB) from the northern CIR and basalts of Deccan CFB are geochemically dissimilar because of: (1) the Deccan CFB basalts typically show a greater iron-enrichment as compared to the northern CIR MORB, (2) a multi-element spiderdiagram reveals that the Deccan CFBs reveal a more fractionated slope (Ba/YbN > 1), as compared to relatively flat northern CIR MORB (Ba/YbN < 1), (3) there is greater REE fractionation for Deccan CFB than for the northern CIR MORB (i.e., La/YbN ˜ 2.3 and 1 respectively) and (4) substantial variation of compatible-incompatible trace elements and their ratios among the two basalt groups suggests that partial melting is a dominant process for northern CIR MORB, while fractional crystallization was a more important control to the geochemical variation for Deccan CFB. Further, incompatible trace element ratios (Nb/U and Nb/Pb) and radiogenic <span class="hlt">isotopic</span> data (Sr-Pb-Nd) indicate that the northern CIR MORBs are similar to depleted mantle [and/or normal (N)-MORB], and often lie on a mixing line between depleted mantle and upper continental crust. By contrast, Deccan CFB compositions lie between the lower continental crust and Ocean island basalt. Accordingly, we conclude that the basaltic suites of the northern CIR MORB and Deccan CFB do not share common parentage, and are therefore genetically unrelated to each other. Instead, we infer that the northern CIR MORB were derived from a depleted mantle source contaminated by upper continental crust, probably during the break up of Gondwanaland; the Deccan CFB are more similar to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6597719','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6597719"><span id="translatedtitle">Carbon and nitrogen <span class="hlt">isotope</span> <span class="hlt">studies</span> in an arctic aquatic 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>The Phase II <span class="hlt">studies</span> of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past <span class="hlt">studies</span>. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II <span class="hlt">studies</span>. These findings are also important in the context of global CO[sub 2] increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10137210','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10137210"><span id="translatedtitle">Carbon and nitrogen <span class="hlt">isotope</span> <span class="hlt">studies</span> in an arctic aquatic 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>The Phase II <span class="hlt">studies</span> of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past <span class="hlt">studies</span>. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II <span class="hlt">studies</span>. These findings are also important in the context of global CO{sub 2} increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25027032','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25027032"><span id="translatedtitle">A highly unradiogenic lead <span class="hlt">isotopic</span> signature revealed by volcanic rocks from the East Pacific Rise.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mougel, Berengere; Agranier, Arnaud; Hemond, Christophe; Gente, Pascal</p> <p>2014-01-01</p> <p>Radiogenic <span class="hlt">isotopes</span> in oceanic basalts provide a window into the different geochemical components defining the composition of Earth's mantle. Here we report the discovery of a novel geochemical signature in volcanic glasses sampled at a sub-kilometre scale along the East Pacific Rise between 15°37'N and 15°47'N. The most striking aspect of this signature is its unradiogenic lead ((206)Pb/(204)Pb=17.49, (207)Pb/(204)Pb=15.46 and (208)Pb/(204)Pb=36.83). In conjunction with enriched <span class="hlt">Sr</span>, <span class="hlt">Nd</span> and Hf signatures, Pb <span class="hlt">isotopes</span> depict mixing lines that trend away from any known mantle end-members. We suggest that this unradiogenic lead component sampled by magmatic melts corresponds to a novel upper mantle reservoir that should be considered in the Pb <span class="hlt">isotope</span> budget of the bulk silicate Earth. Major, trace element and <span class="hlt">isotope</span> compositions are suggestive of an ancient and lower continental origin for this unradiogenic lead component, possibly sulphide-bearing pyroxenites that were preserved even after prolonged stirring within the ambient upper mantle. PMID:25027032</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('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('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeCoA.188...73M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016GeCoA.188...73M&link_type=ABSTRACT"><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('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1812383C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1812383C&link_type=ABSTRACT"><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/2006PhDT.......167W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT.......167W"><span id="translatedtitle">An <span class="hlt">isotopic</span> <span class="hlt">study</span> of fiber-water interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walsh, Frances Luella</p> <p></p> <p>A new technique for measuring the water content of fiber is presented. Tritiated water is added to a pulp/water suspension whereupon the tritium partitions between the bulk water and the pulp. Through this technique a fiber:water partition coefficient is developed, Kpw. This thesis will cover the development of the Kpw procedure and three different case <span class="hlt">studies</span>. The first <span class="hlt">study</span> involves comparing Kpw to traditional methods of fiber water content. The procedure provides a value of ten percent for the tightly bound water content of unrefined hardwood or softwood kraft fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of fiber can be obtained. This estimate compares well to independent measurements of surface area. Kpw has also been found to be valuable in furthering the understanding of refining. Based on the <span class="hlt">study</span>, it is proposed that refining occurs in three discrete stages. First, refining removes the primary cell wall and S1 layer while beginning to swell the S2 layer. Next, internal delamination occurs within the S2 layer. Finally, fiber destruction occurs at high refining levels. By using Kpw, the three stages of refining are clearly recognized. Lastly, Kpw is used to <span class="hlt">study</span> the effect of hornification on bleached softwood kraft fiber. The recycling effects at three refining levels were characterized by Kpw and followed closely the findings of the refining <span class="hlt">study</span>. At low and high refining levels, the impact of recycling was minimal according to Kpw results, but at 400 mL csf the impact of recycling was much more pronounced. This could be attributed to the closing of internal delaminations within the fiber.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26617222','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26617222"><span id="translatedtitle"><span class="hlt">Studies</span> on stable <span class="hlt">isotopic</span> composition of daily rainfall from Kozhikode, Kerala, India.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Unnikrishnan Warrier, C; Praveen Babu, M; Sudheesh, M; Deshpande, Rajendrakumar D</p> <p>2016-06-01</p> <p>The stable <span class="hlt">isotopic</span> compositions of all major daily rain fall samples (n = 113) collected from Kozhikode station in Kerala, India, for the year 2010 representing the pre-monsoon, southwest and northeast monsoon seasons are examined. The <span class="hlt">isotopic</span> variations δ(18)O, δ(2)H and d-excess in daily rainfall ranged from δ(18)O: -4.4 to 2 ‰, δ(2)H: -25.3 to 13.8 ‰, and d-excess: -2.4 to 15.3 ‰; δ(18)O: -9.7 to -0.6 ‰, δ(2)H: -61.7 to 5.3 ‰, and d-excess 5.8 to 17.4 ‰; δ(18)O -11.3 to -1.4 ‰, δ(2)H: -75.3 to 0.9 ‰, and d-excess: 8.8 to 21.3 ‰ during the pre-, southwest and northeast monsoon periods, respectively. Thus, daily rainfall events during two monsoon periods had a distinct range of <span class="hlt">isotopic</span> variations. The daily rain events within the two monsoon seasons also exhibited periodic variations. The <span class="hlt">isotopic</span> composition of rain events during pre-monsoon and a few low-intensity events during the southwest monsoon period had imprints of secondary evaporation. This <span class="hlt">study</span> analysing the stable <span class="hlt">isotopic</span> characteristics of individual rain events in southern India, which is influenced by dual monsoon rainfall, will aid in a better understanding of its mechanism. PMID:26617222</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1612419E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1612419E"><span id="translatedtitle">Hydrogeological and <span class="hlt">isotopic</span> <span class="hlt">study</span> of surface water and groundwater in the Eastern Haouz Plain. Western Morocco</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>El Mandour, Abdennabi; Rochdane, Samia; Reddy, Venkat; Himi, Mahjoub; Casas, Albert</p> <p>2014-05-01</p> <p>The Eastern Haouz area, characterized by a semi-arid climate, is part of the Haouz plain. The basin is built over a broad synclinal between the High Atlas and the Jebilets mountains. The compilation of geological, geophysical and hydrogeological data shows that this area is straddling two major basins of western Morocco. Map of the river system and the piezometric map show the same division line of surface water and groundwater. This division line oriented NNW-SSE is evidenced by the rise of the basement constituted by Paleozoic schists that outcrop near Tamelalt. Thus we can distinguish two main directions of groundwater flow feeding two watersheds (Tensift and Oum Rabiaa rivers) and two large reservoirs in the region of Marrakech. As a contribution to solve the water supply problem in the area, a hydrochemical <span class="hlt">study</span> has been conducted, involving 40 groundwater samples for major ions and 20 stable <span class="hlt">isotope</span> analyses. Hydrochemical results show the geological control on water quality. Samples from Paleozoic schists and Triassic sediments are relatively highly mineralisation and unsuitable for drinking as well as for irrigation. Conversely, groundwater from the alluvial plains is relatively less mineralised than other older geological formations; however, many of the samples are also non-potable. Apart of salinity problem, about 25% of the samples have higher nitrate content than the drinking water permissible limit. Stable <span class="hlt">isotope</span> analysis show that groundwater recharge to the phreatic aquifer is controlled by local conditions. The small difference in the <span class="hlt">isotopic</span> content of river water and a group of groundwater samples is interpreted as the evaporation effect during the recharge. On the other hand, the group of samples with relatively depleted stable <span class="hlt">isotopic</span> content shows faster recharge conditions and less water-rock interaction. Finally, another group of samples is relatively enriched in stable <span class="hlt">isotope</span> content and confirm an increase during the recharge</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUSM.V21A..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUSM.V21A..01L"><span id="translatedtitle">An Experimental <span class="hlt">Study</span> of Lithium <span class="hlt">Isotope</span> Partitioning Among Quartz, Muscovite, and Fluid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lynton, S. J.; Walker, R. J.; Candela, P. A.</p> <p>2002-05-01</p> <p>Preliminary results from an experimental <span class="hlt">study</span> suggest that lithium <span class="hlt">isotopes</span> may serve as an indicator of magmatic hydrothermal processes in felsic environments, such as granitic pegmatites and porphyry-type ore deposits. The experiments were carried out with natural (pegmatitic) specimens of quartz and muscovite and with a chloride-bearing aqueous fluid at 400-500° C and 50-100 MPa. Lithium was introduced into the experimental charges through the fluid, which also contains KCl and HCl (K/Li/H = 100/10/1) and is 1M in total chloride. Two other phases (K-feldspar and phlogopite) were included in the charges to permit coupled substitutions by Li + Al and by Li + Mg into Qz and Ms. In contrast with experiments in other <span class="hlt">isotope</span> systems (eg., O), Li partitioning experiments require allowance for coupled substitutions because some crystallographic sites only become available to Li through coupled substitutions and because the chemical potentials of components necessary for coupled substitutions must be fixed to define fully the thermodynamic conditions of Li partitioning. In two of the experiments a 6Li spike was used to prepare the fluid to magnify the shifts in Li <span class="hlt">isotopic</span> compositions among run products. The experiments were conducted for 15-60 days under argon pressure with Pt capsules, which were loaded into Inconel 625 cold seal vessels. The experimental design permits simultaneous determination of <span class="hlt">isotopic</span> fractionation and elemental partitioning by Li among quartz, muscovite and the fluid. Lithium <span class="hlt">isotopic</span> compositions were determined by thermal ionization mass spectrometry with a triple-filament technique, in which samples are evaporated from side filaments as a phosphate and Li ions are measured directly by the peak-jumping method. Replicate analyses and duplicate experiments indicate reproduceability within approximately +/-1-2‰ . Li concentrations were determined by <span class="hlt">isotope</span> dilution. For the 500° C runs, the preliminary results provide some indications</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NuPhA.935...28S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NuPhA.935...28S"><span id="translatedtitle">Theoretical <span class="hlt">studies</span> on the alpha decay of 178-220Pb <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>Santhosh, K. P.; Sukumaran, Indu; Priyanka, B.</p> <p>2015-03-01</p> <p>The α decay half lives for the <span class="hlt">isotopes</span> of Pb (Z = 82) nuclei in the range 178 ≤ A ≤ 220 have been <span class