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Sample records for subduction-related metamorphism ile

  1. Subduction-related metamorphism beneath ophiolites (Oman) and during early stages of continental collision (Himalaya)

    NASA Astrophysics Data System (ADS)

    Searle, Mike; Waters, David; Cowan, Robert; Cherry, Alan; Cooper, Charles

    2014-05-01

    Subduction-related metamorphism occurs beneath ophiolites (Oman), beneath island arcs (Kohistan) and during the early stages of continental collision (Kaghan, Tso Morari; Himalaya). Ophiolite obduction necessarily involves subduction of first oceanic, then continental crust to mantle depths beneath the ophiolite. In Oman an inverted pressure and temperature profile is exposed beneath the Semail ophiolite from garnet+clinopyroxene-bearing granulite to hornblende+plagioclase amphibolite down through epidote amphibolite and a variety of greenschist facies meta-sediments, dominantly cherts, marbles and quartzites. Thermobarometry on Grt+Cpx-bearing amphibolites immediately beneath the contact with mantle sequence harzburgites shows that the upper sole rocks formed at PT conditions of 770-900°C and 11-13 kbar, equivalent to depths of 30-40 km in oceanic lithosphere. Heat for metamorphism can only have been derived from the overlying mantle peridotites. Pressures are higher than can be accounted for by the thickness of the preserved ophiolite (15-20 km). Timing of peak metamorphism was synchronous with formation of the ophiolite gabbroic - trondhjemite crustal sequence and eruption of the pillow lavas (Cenomanian; 96-95 Ma). During the later stages of obduction the continental margin was dragged down to depths of nearly 100 km and basaltic sills within calc-schists were converted to eclogites (20-25 kbar; 500-560oC; 79.1 Ma), then exhumed back up the same subduction channel. Apparent 'extensional' fabrics throughout the HP units are related to upward flow of deeply buried rocks in a wholly compressional environment. Eclogites in a similar structural position occur along the Himalaya in the northernmost exposures of Indian plate rocks. These eclogites formed either during the latest stage of ophiolite obduction or the earliest stage of continental collision.

  2. Ge and Ga behaviour during subduction-related metamorphism of basic rocks

    NASA Astrophysics Data System (ADS)

    El Korh, Afifé; Luais, Béatrice; Boiron, Marie-Christine; Deloule, Etienne

    2014-05-01

    Ge and Ga are can be used as fluid tracers in hydrothermal systems, as their solubility in fluid is temperature dependant [1,2]. Physico-chemical conditions of hydrothermal processes would result either in Ge enrichment [3], or Ge depletion of the basaltic crust in presence of hydrothermal sulphides [4]. Variations in Ge and Ga concentrations were investigated in a series of HP¬-LT metabasites (peak P-T conditions: 1.7-2.3 GPa and 550-600°C) from the Ile de Groix (France), to examine their behaviour during the fluid-rock interactions and associated metamorphism related to subduction. The studied metabasites represent former MOR-type basalts, which underwent a pre-HP low-temperature hydrothermal alteration [5]. Whole rock Ga and Ge concentrations were analysed by SN-ICP-MS (± 8%; 1σ). The Ga abundances in eclogites and blueschists (21.0-21.6 ppm) are similar to the values measured in tholeiitic basalts (18-22 ppm; [6]), while they decrease slightly in the greenschist facies metabasites (16.9-20.5 ppm). The Ge abundances measured in the metabasites (1.2-2.1 ppm) are generally higher than those of tholeiitic basalts (1.4-1.5 ppm; [6]), suggesting Ge enrichment during the low-T hydrothermal alteration. Similarly to Ga, the decrease of the Ge abundances in greenschists (1.2-1.9 ppm) compared to blueschists and eclogites (1.6-2.0 ppm) indicate that a fraction of Ge and Ga left the metabasites during the fluid-rock interactions related to the retrograde metamorphism. Ga and Ge abundances in minerals were obtained using LA-ICP-MS (± 8-15%; 1σ). Garnet and epidote are major phases in the metabasites. They are the main hosts for Ge (3.3-8.2 ppm in Grt; 2.4-12 ppm in Ep) and Ga (2.6-8.6 ppm in Grt; 33-112 ppm in Ep). Glaucophane and omphacite also contain significant amounts of Ga (3-15 ppm). The different generations of garnet and epidote formed during the prograde and retrograde metamorphic stages [5] can be distinguished using the Ge/Si and Ga/Al ratios. Ge/Si in

  3. Subduction-related prograde metamorphism of the ultramafic members of the Central-Sudetic Ophiolite (SW Poland)

    NASA Astrophysics Data System (ADS)

    Wojtulek, Piotr; Puziewicz, Jacek; Ntaflos, Theodoros

    2016-04-01

    ~680-780°C. The BBM serpentinites have mineral assemblage (antigorite-olivine-diopside-tremolite) typical for ~420-490°C and the ŚM rocks containing antigorite-olivine-diopside were altered at ~380-460°C (cf. phase diagram based on Berman et al., 1986). Similar mineral succession indicative for prograde metamorphism of serpentinites is typical for alteration in subduction zone setting and occurs in serpentinites from the Lanzo Massif in Alps (Debret et al., 2013) and in the mantle wedge serpentinites from Guatemala (Kodolanyi et al., 2012). This abstract was prepared as a part of the project of the National Science Centre of Poland ("Evolution of serpentinic members of the Lower Silesia ophiolites", DEC-2012/07/N/ST10/03934). References Berman, R. G., Engi, M., Greenwood, H. J., Brown, T. H., 1986. Derivation of internally-consistent thermodynamic data by the technique of mathematical programming: a review with application to the system MgO-SiO2-H2O. Journal of Petrology 27, 1331-1364. Debret, B., Nicollet, C., Schwartz, S., Andreani, M., Godard, M., 2013. Three steps of serpentinization in an eclogitized oceanic serpentinization front (Lanzo Massif - Western Alps). Journal of Metamorphic Geology 31, 65 - 186. Kodolányi, J., Pettke, T., Spandler, C., Kamber, B.S. and Gméling, K., 2012. Geochemistry of ocean floor and forearc serpentinites: Constraints on the ultramafic input to subduction zones. Journal of Petrology 53, 235-270.

  4. The Cambrian initiation of intra-oceanic subduction in the southern Paleo-Asian Ocean: Further evidence from the Barleik subduction-related metamorphic complex in the West Junggar region, NW China

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Han, Bao-Fu; Xu, Zhao; Ren, Rong; Zhang, Jin-Rui; Zhou, Jing; Su, Li; Li, Qiu-Li

    2016-06-01

    In this study, we present new evidence from the Barleik subduction-related metamorphic complex in the southern West Junggar region, northwestern China, for the Cambrian initiation of intra-oceanic subduction in the southern Paleo-Asian Ocean. The Barleik metamorphic complex is mainly composed of blueschist and amphibolite blocks within an ophiolitic mélange and their protoliths are calc-alkaline andesite and alkali and tholeiitic basalts. The calc-alkaline andesite has a zircon U-Pb age of 502 ± 2 Ma, obtained from magmatic cores of zircon grains, and shares geochemical features similar to the 515-485 Ma intra-oceanic arc magmatic rocks in the West Junggar region. By contrast, the alkali and tholeiitic basalts have trace element features similar to ocean island and enriched mid-ocean ridge basalts, respectively. Rutile and sodic-calcic amphibole from the amphibolite have a U-Pb age of 502 ± 25 Ma and a 40Ar/39Ar age of ∼504 Ma, respectively, which are in good agreement within errors with a 40Ar/39Ar age of 492 ± 4 Ma for phengite from the blueschist. These metamorphic ages of ∼500 Ma are interpreted to represent the timing of Pacific-type subduction-related metamorphism and are also compatible with ages of the oldest supra-subduction zone ophiolites (531-512 Ma) and intra-oceanic arc plutons (515-485 Ma) in the southern West Junggar region. Being one of the oldest subduction-related metamorphic complexes (509-490 Ma) in the southern Central Asian Orogenic Belt, the Barleik metamorphic complex, together with the oldest arc plutons, definitely indicate the initial intra-oceanic subduction in the southern Paleo-Asian Ocean at least in the Early Cambrian.

  5. Metamorphic evolution and thermobaric structure of the subduction-related Bacariza high-pressure granulite formation (Cabo Ortegal Complex, NW Spain)

    NASA Astrophysics Data System (ADS)

    Puelles, P.; Ábalos, B.; Gil Ibarguchi, J. I.

    2005-09-01

    The high-pressure Bacariza granulite formation comprises various lithostratigraphic units of granulite orthogneisses, ultramafic, Mg-rich mafic, intermediate and common mafic granulites, as well as of more exotic intercalations. Mineral assemblages in equilibrium in ultramafic- to intermediate rocks contain garnet, clinopyroxene and plagioclase, with different amounts of zoisite/clinozoisite, kyanite, quartz, scapolite, rutile and ilmenite depending on the granulite lithotype, whereas granulite orthogneisses contain garnet, phengite, biotite, K-feldspar, antiperthitic plagioclase, quartz and rutile as primary phases. Thermobarometry of these rocks supports the existence of a high-pressure metamorphism for which near-peak P- T conditions have been estimated at ca. 790 °C and 1.6 GPa. The preserved fabrics and structures enable us to relate the metamorphism to coeval polyphasic deformational processes. Dynamic retrogression began under still high-pressure granulite facies conditions (1.4 GPa and ca. 740 °C) and is postdated by symplectitization (1.3 GPa and ca. 715 °C). Subsequent retrogression under medium pressure amphibolite facies conditions at similar temperature was either widespread and static or localized and dynamic as a result of intense deformation partitioning during uplift. Loading/heating and subsequent decompression/cooling are related to a single cycle in a subduction conduit setting. This study suggests that high-pressure granulite metamorphism might not be as uncommon in the high-pressure metamorphic series as previously thought. Moreover, it might constitute a diagnostic feature of convergent lithospheric settings, whether or not associated with eclogite facies metamorphism in adjacent units.

  6. Structural heterogeneity in mountain belts: rift- vs. subduction-related control.

    NASA Astrophysics Data System (ADS)

    Vitale Brovarone, A.; Malavieille, J.; Beltrando, M.; Beyssac, O.; Molli, G.; Herwartz, D.; Rubatto, D.; Monié, P.; Groppo, C.; Compagnoni, R.; Hermann, J.; Martin, L.; Lagabrielle, Y.; Meresse, F.

    2012-04-01

    In subduction zones, the so-called subduction channel is believed to represent the locus where the primary exhumation of deeply subducted material occurs. It is also considered as a major zone of deformation and tectonic shuffling [1, 2]. The resulting intense deformation that is commonly observed in exhumed subduction terranes is generally considered as the cause for the lithological heterogeneity (e.g. association of continental basement rocks and meta-ophiolites) encountered in highly metamorphosed units [3]. In Alpine Corsica (Western Mediteranean), metamorphism and deformation vary from very low-grade up to lawsonite-eclogite facies conditions. Compared to similar domains of Western Alps [4], deformation in Corsica is often localized, allowing a detailed characterization of primary rift-related vs. subduction-related structures to be done through a wide spectrum of metamorphic conditions [4]. Based on extensive stratigraphic, structural, petrologic (including RSCM and pseudosection) and geochronological (U-Pb zircon; Lu-Hf garnet and lawsonite; Ar-Ar phengite) data, the main tectono-metamorphic units and their evolution from rifting to the final stages of orogenesis have been established. They show a high lithological heterogeneity that is essentially related to primary stratigraphic/tectonic processes occurring prior to subduction during continental break-up and subsequent oceanic extensional tectonics. Otherwise, each unit shows a remarkable metamorphic homogeneity over large areas. These features indicate that large volumes of subducted lithosphere behave as single and coherent tectonostratigraphic units during subduction/exhumation. As a consequence, the number of significant tectono-metamorphic boundaries is limited to the main contacts separating these large volumes of former lithosphere. Our study highlights on the major control exerted by inherited extensional structures during subduction and mountain building in opposition to the formation subduction-related

  7. Minutes to Millennia: Diffusion Methods in Subduction-Related Volcanism

    NASA Astrophysics Data System (ADS)

    Morgan, D. J.; Allan, A.; Wilson, C. J. N.; Charlier, B. L.; Davidson, J.

    2014-12-01

    Diffusion methods have several advantages as relative geochronometers in volcano-related magmatic processes: diffusion stops on eruption, locking in short timescale information; methods are relatively easy to implement; and suitable material is generally abundant. Such methods also pose significant, accompanying challenges: the need for accurate melt palaeothermometry, uncertainties in diffusion parameters, and sometimes even a cryptic connection between mineral zonation and timescale. As all timescales are relative to an event, timing is not absolute, and care must be taken in interpretation. Yet for all the difficulties, diffusion tools are seeing more widespread usage. This has come about because of the potential of diffusion methods to interrogate certain pre-eruptive processes operating over timescales of relevance to human timescales and responses, having direct bearing on hazard mitigation procedures. In studying subduction zone systems we have a wide range of minerals to choose from but will, in subduction-related, andesitic-to-rhyolitic systems, usually be operating away from the relatively well-constrained system of olivine, and instead be dealing with mineral phases that offer different challenges, such as plagioclase, quartz, sanidine, amphibole, orthopyroxene, Fe-Ti oxides and mica. Timescales here span a wide range across different mineral-element combinations, from minutes for Li in plagioclase and quartz to days by Fe-Ti oxides, years by orthopyroxene Fe-Mg and decades to millennia with plagioclase, sanidine and quartz. This contribution will focus on the interpretation of diffusion signals in minerals found in subduction-related volcanic systems. To understand what any modelled timescale means, the process which formed the relevant zonation pattern is absolutely key, yet often elusive. Variations in P, T, X conditions really drive the crystallisation process yet certain zonation patterns are non-unique. This ambiguity necessitates painstaking

  8. Shape Metamorphism Using p-Laplacian Equation

    SciTech Connect

    Cong, Ge; Esser, Mehmet; Parvin, Bahram; Bebis, George

    2004-05-19

    We present a new approach for shape metamorphism, which is a process of gradually changing a source shape (known) through intermediate shapes (unknown) into a target shape (known). The problem, when represented with implicit scalar function, is under-constrained, and regularization is needed. Using the p-Laplacian equation (PLE), we generalize a series of regularization terms based on the gradient of the implicit function, and we show that the present methods lack additional constraints for a more stable solution. The novelty of our approach is in the deployment of a new regularization term when p --> infinity which leads to the infinite Laplacian equation (ILE). We show that ILE minimizes the supremum of the gradient and prove that it is optimal for metamorphism since intermediate solutions are equally distributed along their normal direction. Applications of the proposed algorithm for 2D and 3D objects are demonstrated.

  9. Th isotope and U-series studies of subduction-related volcanic rocks

    SciTech Connect

    Gill, J.B.; Williams, R.W. )

    1990-05-01

    The activities of 6-7 radionuclides measured by alpha spectrometry are reported for 35 samples of recent volcanic rocks from 24 volcanoes in 9 arcs. These include continental margins (Cascades, Alaska, Costa Rica), island arcs (the Sunda, Banda, and Sangihe arcs of Indonesia, Marianas, Japan, Aleutians, Antilles, Tonga), and a backarc basin (Lau Basin). Enrichment of {sup 238}U over {sup 230}Th is more common and greater in these subduction-related volcanics than in those from other tectonic environments. {sup 230}Th/{sup 232}Th ratios also extend to higher values, both in absolute numbers and relative to other isotope ratios. Enrichment of {sup 210}Po and {sup 226}Ra over {sup 230}Th is widespread and is more common and greater in island arcs than continental margins. The level of Po or Ra enrichment is similar to that in ocean island and ridge basalts and deceases with differentiation. The differences in Th-U systematics between subduction-related and other volcanic rocks are attributed to variations in the process of melt extraction, changes in bulk partition coefficients within the mantle wedge, or preferential addition of U from subducted lithosphere. Ra enrichments are attributed to partial melting processes which are similar to those at ocean ridges. Smaller excesses at continental margins are attributed either to slower ascent or to differences in the process of melt formation beneath continents.

  10. The Role of Chaotic Dynamics in the Cooling of Magmatic Systems in Subduction Related Environment

    NASA Astrophysics Data System (ADS)

    Petrelli, M.; El Omari, K.; Le Guer, Y.; Perugini, D.

    2015-12-01

    Understanding the dynamics occurring during the thermo-chemical evolution of igneous bodies is of crucial importance in both petrology and volcanology. This is particularly true in subduction related systems where large amount of magmas start, and sometime end, their differentiation histories at mid and lower crust levels. These magmas play a fundamental role in the evolution of both plutonic and volcanic systems but several key questions are still open about their thermal and chemical evolution: 1) what are the dynamics governing the development of these magmatic systems, 2) what are the timescales of cooling, crystallization and chemical differentiation; 4) how these systems contribute to the evolution of shallower magmatic systems? Recent works shed light on the mechanisms acting during the growing of new magmatic bodies and it is now accepted that large crustal igneous bodies result from the accretion and/or amalgamation of smaller ones. What is lacking now is how fluid dynamics of magma bodies can influence the evolution of these igneous systems. In this contribution we focus on the thermo-chemical evolution of a subduction related magmatic system at pressure conditions corresponding to mid-crustal levels (0.7 GPa, 20-25 km). In order to develop a robust model and address the Non-Newtonian behavior of crystal bearing magmas, we link the numerical formulation of the problem to experimental results and rheological modeling. We define quantitatively the thermo-chemical evolution of the system and address the timing required to reach the maximum packing fraction. We will shows that the development of chaotic dynamics significantly speed up the crystallization process decreasing the time needed to reach the maximum packing fraction. Our results have important implications for both the rheological history of the magmatic body and the refilling of shallower magmatic systems.

  11. H 2O in basalt and basaltic andesite glass inclusions from four subduction-related volcanoes

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.; Layne, G. D.

    1993-06-01

    Total dissolved H 2O and major element abundances were measured in basalt and basaltic andesite glass inclusions in olivine phenocrysts from Quaternary eruptions of four subduction-related volcanoes to test the hypothesis that low-MgO high-alumina basalts contain high H 2O at depth [1] and to reveal any petrogenetically significant correlations between arc basalt compositions and H 2O contents. Total dissolved H 2O (combined molecular H 2O and OH groups) measured by ion microprobe in mafic glass inclusions from the 1974 eruption of Fuego, Guatemala, reaches 6.2 wt.%. Dissolved H 2O contents decrease in more evolved Fuego glasses. Correlations of H 2O with MgO, Na 2O, K 2O, S and Cl indicate that aqueous fluid exsolution during magma ascent forced crystallization and differentiation of residual liquids. Low-K 2O magnesian high-alumina basalt glass inclusions from the 3 ka eruption of Black Crater (Medicine Lake volcano, California) have low H 2O contents, near 0.2 wt.%, which are consistent with the MORB-like character of these and other primitive lavas of the Medicine Lake region. Basalt and basaltic andesite glass inclusions from Copco Cone and Goosenest volcano on the Cascade volcanic front north of Mt. Shasta have H 2O contents of up to 3.3 wt.%. The range of H 2O contents in Cascade mafic magmas is too large to have resulted solely from enrichment by crystallization and indicates the participation of an H 2O-rich component in magma generation or crustal-level modification. Whereas fluid-absent melting of amphibole-bearing peridotite can account for the H 2O in most mafic arc liquids, the very high H 2O/alkali ratios of the 1974 Fuego eruptives suggest that an aqueous fluid was involved in the generation of Fuego basalts.

  12. Subduction Related Crustal and Mantle Deformations and Their Implications for Plate Dynamics

    NASA Astrophysics Data System (ADS)

    Okeler, Ahmet

    Ocean-continent convergence and subsequent continental collision are responsible for continental growth, mountain building, and severe tectonic events including volcanic eruptions and earthquake activity. They are also key driving forces behind the extensive thermal and compositional heterogeneities at crustal and mantle depths. Active subduction along the Calabrian Arc in southern Italy and the Hellenic Arc are examples of such collisional tectonics. The first part of this thesis examines the subduction related deformations within the crust beneath the southern Apennines. By modeling regional surface wave recordings of the largest temporary deployment in the southern Apennines, a lower-crustal/upper-mantle low-velocity volume extending down to 50 km beneath the mountain chain is identified. The magnitude (˜ 0.4 km/s slower) and anisotropic nature (˜ 10%) of the anomaly suggest the presence of hot and partially molten emplacement that may extend into the upper-crust towards Mt. Vulture, a once active volcano. Since the Apulian basement units are deformed during the compressional and consequent extensional events, our observations favor the "thick-skin" tectonic growth model for the region. In the deeper mantle, active processes are thermodynamically imprinted on the depth and strength of the phase transitions. This thesis examines more than 15000 SS precursors and provides the present-day reflectivity structure and topography associated with these phase transitions. Through case studies I present ample evidence for both slab penetration into the lower mantle (beneath the Hellenic Arc, Kurile Island and South America) and slab stagnation at the bottom of the Mantle Transition Zone (beneath the Tyrrhenian Sea and eastern China). Key findings include (1) thermal anomalies (˜ 200 K) at the base of the MTZ, which represent the deep source for Cenozoic European Rift Zone, Mount Etna and Mount Cameroon volcanism, (2) significant depressions (by 20-40 km) at the bottom

  13. Boron and Lithium Isotope Determinations in Minerals from Subduction-Related Rocks by LA-MC-ICPMS

    NASA Astrophysics Data System (ADS)

    Martin, C.; Harlow, G. E.; Ponzevera, E.; Marschall, H.

    2014-12-01

    Lithium (Li) and boron (B) are incompatible light elements that preferentially partition into the fluid phase, whether melt or aqueous liquid, and thus are useful for tracking fluid-related processes in rocks. Currently, most of the Li isotopic data available on subduction-related rocks are whole-rock analysis; and the few B isotopic analyses on subduction material have been carried out on whole-rock or in-situ in accessory phase (tourmaline). The new method presented here couples an ESI New Wave UP-193-FX ArF* (193 nm) excimer laser ablation microscope with a Neptune Plus (Thermo Scientific) MC-ICP-MS. In situ B and Li isotopic analyses were carried out on mica and pyroxenes from jadeitites and albite mica-rocks from a subduction-related mélange. These results have been compared with SIMS analyses for B on the same mineral samples and with MC-ICP-MS analyses for Li on whole-rock or a mineral separate from the same sample. The results show that for B concentrations above 15 μg/g, the data obtained by LA-MC-ICPMS and by SIMS are similar within error, for both mica and pyroxene. The significant improvement of LA-MC-ICPMS compared to SIMS is the duration of measurements: one analysis takes 3 minutes by LA-MC-ICPMS, and 32 minutes by SIMS. Such a method therefore permits multiplying the number of isotopic analyses, providing a better interpretation of the studied samples, with a lateral resolution and an error on each measurement similar to those obtained with SIMS. The results show that for Li concentrations above 10μg/g, the data obtained by LA-MC-ICPMS and by MC-ICP-MS are also similar within error, for both mica and pyroxene. The significant improvement of LA-MC-ICPMS compared to MC-ICP-MS is better spatial resolution. Indeed, many of the mineral phases encountered in subduction-related rocks display a strong chemical zoning, and the analyses carried out by wet chemistry and MC-ICP-MS average the isotopic values of the different zones. This newly developed

  14. Metamorphism in mesosiderites

    NASA Technical Reports Server (NTRS)

    Delaney, J. S.; Prinz, M.; Harlow, G. E.; Nehru, C. E.

    1982-01-01

    Previous studies of mesosiderites have identified a metamorphic overprint in these meteorites. However, the effects and implications of this overprint have not yet been explored in detail. The present study documents several important textural and chemical features of the mesosiderites. The components of mesosiderites are examined, taking into account orthopyroxenites, olivine in clasts, mesosiderite mafic clasts, and metal. The characteristics of the silicate matrix of the mesosiderites is explored, and textural and chemical evidence of metamorphism is discussed, giving attention to coronas on olivine clasts, overgrowths on Mg-pyroxene clasts, rims on iron rich pyroxene grains, poikiloblasts of plagioclase, and resorption of clasts. Aspects of redox formation of merrillite are considered along with the causes and the implications of metamorphism. It is found that metamorphism has radically changed the texture of the silicate fraction of the mesosiderites.

  15. Color Me Metamorphic.

    ERIC Educational Resources Information Center

    Birdd, Donald L.

    1990-01-01

    Described are five activities using crayons to demonstrate the rock cycle including weathering, erosion and sedimentation, and sedimentary, metamorphic, and igneous rock formation. Discussed are materials, procedures, and probable results. (CW)

  16. Plate tectonics: Metamorphic myth

    NASA Astrophysics Data System (ADS)

    Korenaga, Jun

    2016-01-01

    Clear evidence for subduction-induced metamorphism, and thus the operation of plate tectonics on the ancient Earth has been lacking. Theoretical calculations indicate that we may have been looking for something that cannot exist.

  17. Petrology of metamorphic rocks

    SciTech Connect

    Suk, M.

    1983-01-01

    ''Petrology of Metamorphic Rocks'' reviews Central European opinions about the origin and formation of metamorphic rocks and their genetic systems, confronting the works of such distinguished European scientists as Rosenbusch, Becke, Niggli, Sander, Eskola, Barth and others with present-day knowledge and the results of Soviet and American investigations. The initial chapters discuss the processes that give rise to metamorphic rocks, and the main differences between regional metamorphism and other types of alterations, the emphasis being laid on the material characteristic of the processes of metamorphism, metasomatism and ultrametamorphism. Further chapters give a brief characterization of research methods, together with a detailed genetic classification based on the division of primary rocks into igneous rocks, sediments and ore materials. The effects of metamorphic alterations and those of the properties of the primary rocks are analyzed on the basis of examples taken chiefly from the Bohemian Massif, the West Carpathians, other parts of the European Variscides, from the crystalline Scandinavian Shelf in Norway and Finland, and from the Alps. Typical examples are documented by a number of charts, photographs and petrographical - particularly petrochemical - data.

  18. Late Neoproterozoic metamorphic assemblages along the Pan-African Hamisana Shear Zone, southeastern Egypt: Metamorphism, geochemistry and petrogenesis

    NASA Astrophysics Data System (ADS)

    Ali-Bik, Mohamed W.; Sadek, Mohamed F.; Ghabrial, Doris Sadek

    2014-11-01

    investigations, the island arc assemblages are grouped into: (a) meta-igneous rocks (hornblende-biotite gneiss, biotite gneiss and amphibolites) and (b) metasedimentary rocks (psammopelitic gneiss, hornblende-schist and calc-silicates). Geochemical inspection revealed the non-consanguineous nature of these rock units. They represent subduction-related, theoleiitic and calc-alkaline magmatic rocks and their concomitant sedimentary derivations as well as minor continental shelf calcareous sediments. In terms of maturity, the geochemical signatures of these subduction-related rocks point to an immature volcanic arc origin.

  19. Metamorphic facies map of Alaska

    SciTech Connect

    Dusel-Bacon, C.; O-Rourke, E.F.; Reading, K.E.; Fitch, M.R.; Klute, M.A.

    1985-04-01

    A metamorphic-facies of Alaska has been compiled, following the facies-determination scheme of the Working Group for the Cartography of the Metamorphic Belts of the World. Regionally metamorphosed rocks are divided into facies series where P/T gradients are known and into facies groups where only T is known. Metamorphic rock units also are defined by known or bracketed age(s) of metamorphism. Five regional maps have been prepared at a scale of 1:1,000,000; these maps will provide the basis for a final colored version of the map at a scale of 1:2,500,000. The maps are being prepared by the US Geological Survey in cooperation with the Alaska Division of Geological and Geophysical Surveys. Precambrian metamorphism has been documented on the Seward Peninsula, in the Baird Mountains and the northeastern Kuskokwim Mountains, and in southwestern Alaska. Pre-Ordovician metamorphism affected the rocks in central Alaska and on southern Prince of Wales Island. Mid-Paleozoic metamorphism probably affected the rocks in east-central Alaska. Most of the metamorphic belts in Alaska developed during Mesozoic or early Tertiary time in conjuction with accretion of many terranes. Examples are Jurassic metamorphism in east-central Alaska, Early Cretaceous metamorphism in the southern Brooks Range and along the rim of the Yukon-Kovyukuk basin, and late Cretaceous to early Tertiary metamorphism in the central Alaska Range. Regional thermal metamorphism was associated with multiple episodes of Cretaceous plutonism in southeastern Alaska and with early Tertiary plutonism in the Chugach Mountains. Where possible, metamorphism is related to tectonism. Meeting participants are encouraged to comment on the present version of the metamorphic facies map.

  20. Spatial and temporal relations of the ophiolites and the metamorphic soles along the Tauride belt, Turkey

    NASA Astrophysics Data System (ADS)

    Parlak, Osman; Simsek, Emrah; Ezgi Ozturk, Selena; Simsek, Gokce; Simsek, Tugce; Robertson, Alastair; von Quadt, Albrecht; Köpke, Jürgen; Karaoglan, Fatih

    2016-04-01

    ) techniques. The available geochronological data from the magmatic and metamorphic rocks appear to overlap in time. This suggests that oceanic subduction-related melts were generated coevally with the onset of intra-oceanic subduction in a Late Cretaceous Neotethyan oceanic basin. This work was financially supported by the Scientific and Technical Research Council of Turkey (TUBITAK) with project number 113Y412.

  1. Metamorphic belts of Anatolia

    NASA Astrophysics Data System (ADS)

    Oberhänsli, Roland; Prouteau, Amaury; Candan, Osman; Bousquet, Romain

    2015-04-01

    Investigating metamorphic rocks from high-pressure/low-temperature (HP/LT) belts that formed during the closure of several oceanic branches, building up the present Anatolia continental micro-plate gives insight to the palaeogeography of the Neotethys Ocean in Anatolia. Two coherent HP/LT metamorphic belts, the Tavşanlı Zone (distal Gondwana margin) and the Ören-Afyon-Bolkardağ Zone (proximal Gondwana margin), parallel their non-metamorphosed equivalent (the Tauride Carbonate Platform) from the Aegean coast in NW Anatolia to southern Central Anatolia. P-T conditions and timing of metamorphism in the Ören-Afyon-Bolkardağ Zone (>70?-65 Ma; 0.8-1.2 GPa/330-420°C) contrast those published for the overlying Tavşanlı Zone (88-78 Ma; 2.4 GPa/500 °C). These belts trace the southern Neotethys suture connecting the Vardar suture in the Hellenides to the Inner Tauride suture along the southern border of the Kirşehir Complex in Central Anatolia. Eastwards, these belts are capped by the Oligo-Miocene Sivas Basin. Another HP/LT metamorphic belt, in the Alanya and Bitlis regions, outlines the southern flank of the Tauride Carbonate Platform. In the Alanya Nappes, south of the Taurides, eclogites and blueschists yielded metamorphic ages around 82-80 Ma (zircon U-Pb and phengite Ar-Ar data). The Alanya-Bitlis HP belt testifies an additional suture not comparable to the northerly Tavşanlı and Ören-Afyon belts, thus implying an additional oceanic branch of the Neotethys. The most likely eastern lateral continuation of this HP belt is the Bitlis Massif, in SE Turkey. There, eclogites (1.9-2.4 GPa/480-540°C) occur within calc-arenitic meta-sediments and in gneisses of the metamorphic (Barrovian-type) basement. Zircon U-Pb ages revealed 84.4-82.4 Ma for peak metamorphism. Carpholite-bearing HP/LT metasediments representing the stratigraphic cover of the Bitlis Massif underwent 0.8-1.2 GPa/340-400°C at 79-74 Ma (Ar-Ar on white mica). These conditions compares to the Tav

  2. Modelling Metamorphism by Abstract Interpretation

    NASA Astrophysics Data System (ADS)

    Dalla Preda, Mila; Giacobazzi, Roberto; Debray, Saumya; Coogan, Kevin; Townsend, Gregg M.

    Metamorphic malware apply semantics-preserving transformations to their own code in order to foil detection systems based on signature matching. In this paper we consider the problem of automatically extract metamorphic signatures from these malware. We introduce a semantics for self-modifying code, later called phase semantics, and prove its correctness by showing that it is an abstract interpretation of the standard trace semantics. Phase semantics precisely models the metamorphic code behavior by providing a set of traces of programs which correspond to the possible evolutions of the metamorphic code during execution. We show that metamorphic signatures can be automatically extracted by abstract interpretation of the phase semantics, and that regular metamorphism can be modelled as finite state automata abstraction of the phase semantics.

  3. Permo-Carboniferous granitoids with Jurassic high temperature metamorphism in Central Pontides, Northern Turkey

    NASA Astrophysics Data System (ADS)

    Gücer, Mehmet Ali; Arslan, Mehmet; Sherlock, Sarah; Heaman, Larry M.

    2016-04-01

    In the northern part of the Central Pontides (N Turkey) there are different metamorphic rocks exposed, notably the Devrekani metamorphic rocks. Here, upper amphibolite-lower granulite facies metamorphic rocks contain predominantly paragneiss, orthogneiss and metacarbonate, and to a lesser extent, amphibolite and quartzite, with cross-cutting aplite, pegmatite and granite veins. This is the first report of these rocks and includes new data on the petrochemistry, geochronology and metamorphic evolution of the Devrekani orthogneisses from the Central Pontides. The orthogneisses show five different mineral parageneses with the characteristic mineral assemblage quartz + K-feldspar + plagioclase + biotite ± hornblende ± opaque (± ilmenite and ± magnetite), and accessory minerals (zircon, sphene and apatite). These metamorphic rocks exhibit generally granoblastic, lepidogranoblastic and nematolepidogranoblastic with locally migmatitic and relic micrographic textures. They have well-developed centimeter-spaced gneissic banding and display gneissose structure with symmetric, asymmetric and irregular folds. The petrographic features, mineralogical assemblages and weak migmatization reflect high temperature conditions. Thermometric calculations in the orthogneisses indicate metamorphic temperatures reached 744 ± 33 °C. Field relations, petrography and petrochemistry suggest that the orthogneisses have predominantly granodioritic and some granitic protoliths, that show features of I-type, medium to high-potassic calc-alkaline volcanic arc granitoids. The orthogneisses have high contents of LILEs and low contents of HFSEs with negative Nb and Ti anomalies, which are typical of subduction-related magmas. The orthogneisses also show significant LREE enrichment relative to HREE with negative Eu anomalies (EuN/Eu* = 0.33-1.07) with LaN/LuN = 6.98-20.47 values. Based on U-Pb zircon dating data, the protoliths are related to Permo-Carboniferous (316-252 Ma) magmatism. It is

  4. Fluid-driven metamorphism

    NASA Astrophysics Data System (ADS)

    Jamtveit, B.; Ulven, O. I.; Malthe-Sorenssen, A.

    2014-12-01

    Metamorphic processes in the Earth crust are almost invariably associated with fluid migration. Many lines of evidence suggest that fluid migration is intimately coupled both to the metamorphic reactions, and to associated deformation processes. Petrologic arguments suggest that all granulite facies and most amphibolite facies rocks are essentially dry (no free fluid phase) at normal geothermal gradients outside periods of heating-produced fluid generation. In addition, except at high pressure - low temperature condition, fluid-consuming reactions leads to an increase in solid volume and a potential clogging of any initial pore space. Hence, fluid migration in medium and high-grade metamorphic rocks is in general associated with some porosity producing process. Porosity generation may occur by either chemical or mechanical processes. In systems with high fluid fluxes, porosity may be produced by dissolution and transport of mass out of the system. Such fluxes can normally only be sustained over short length scales and limited time scales. In systems where the infiltrating fluid is far from equilibrium with the rock matrix, mechanical porosity generation can arise from local stresses generated by the volume change of volatilization reactions. Furthermore, it has become increasingly clear that crustal rocks may be under significant tectonic stress, even far from plate tectonic boundaries. In situations where the rocks are close to critically stressed, any stress perturbations caused by reaction driven changes in solid volume or fluid pressure gradients may lead to dilatant deformation and porosity production on a scale much larger than the characteristic length scales of the reacting rock units. Field observations, experimental studies and modeling results will be presented that focus on reaction driven porosity generation in systems subject to variable initial differential stresses.

  5. Metamorphic Testing for Cybersecurity

    PubMed Central

    Chen, Tsong Yueh; Kuo, Fei-Ching; Ma, Wenjuan; Susilo, Willy; Towey, Dave; Voas, Jeffrey

    2016-01-01

    Testing is a major approach for the detection of software defects, including vulnerabilities in security features. This article introduces metamorphic testing (MT), a relatively new testing method, and discusses how the new perspective of MT can help to conduct negative testing as well as to alleviate the oracle problem in the testing of security-related functionality and behavior. As demonstrated by the effectiveness of MT in detecting previously unknown bugs in real-world critical applications such as compilers and code obfuscators, we conclude that software testing of security-related features should be conducted from diverse perspectives in order to achieve greater cybersecurity. PMID:27559196

  6. Variable sediment flux in generation of Permian subduction-related mafic intrusions from the Yanbian region, NE China

    NASA Astrophysics Data System (ADS)

    Guo, Feng; Li, Hongxia; Fan, Weiming; Li, Jingyan; Zhao, Liang; Huang, Miwei

    2016-09-01

    This paper presents petrology, mineralogy, zircon U-Pb ages, and whole-rock major, trace element and Sr-Nd-Hf isotopic compositions of four Permian (273-253 Ma) subduction-related mafic intrusions (including the Qinggoushan and Qianshan gabbros, and the Wangqing and Shuguang diorites) from the Yanbian region, NE China, with aims to understand the role of subducted sediment flux in generation of arc mafic cumulates. These intrusions have mineral assemblages crystallized in water-saturated parental magmas and show variable degrees of crystal accumulation as observed in mafic cumulates in subduction zones. Mass-balance consideration indicates that their parental magmas were calc-alkaline with arc-type trace element features (enrichments in large ion lithophile elements (LILE) and light rare earth elements (LREE) and depletions in Nb-Ta). They also have Sr-Nd-Hf isotopic compositions, i.e., 87Sr/86Sr(i) = 0.7029-0.7047, εNd(t) = + 0.9 ~ + 6.8, εHf(t) = + 5.6 ~ + 14.6, similar to modern arc basalts. The parental magmas were likely derived from a mantle wedge variably metasomatized by sediment melt and fluid from the subducting paleo-Asian Oceanic slab. Combined trace elemental and isotopic modeling results suggest that the parental magma of Qinggoushan gabbro was formed through 5-20% melting of the mantle wedge with 1% and 1.5% additions of sediment fluid and sediment melt, respectively; 5-10% melting of the mantle wedge through inputs of 1% sediment fluid and 2% sediment melt produced the Qianshan gabbro; 10-20% melting of the mantle wedge with additions of 1% sediment fluid and 3% sediment melt formed the Wangqing diorite; whereas 5-20% melting of the mantle wedge through an input of 1.5% sediment melt produced the Shuguang diorite. The Hf-Nd isotopic array of the Yanbian Permian mafic intrusions reflected the existence of an Indian Ocean-type mantle, which was isotopically distinct from the Pacific-type mantle during early Paleozoic in the Central Asian Orogenic

  7. Tracing partial melting and subduction-related metasomatism in the Kamchatkan mantle wedge using noble gas compositions

    NASA Astrophysics Data System (ADS)

    Hopp, Jens; Ionov, Dmitri A.

    2011-02-01

    We determined noble gas composition of minerals separated from mantle-derived xenoliths hosted by andesites in the active Avacha volcano, Kamchatka peninsula, Russia in order to better constrain the provenance and nature of fluids involved in partial melting and metasomatism in the mantle wedge. The lithospheric mantle beneath Avacha mainly consists of spinel harzburgites produced by high degrees of melt extraction. Data on coarse olivine separated from seven harzburgite xenoliths constrain fluid regime during flux melting in arc settings. Pyroxenes from two websterite veins cross-cutting the harzburgites characterize post-melting metasomatism by subduction-related melts or fluids. 3He/4He-ratios of 5.2 ± 0.6 to 8.1 ± 0.3 RA obtained on both olivines and pyroxenes overlap the highest values reported for volcanic rocks from Kamchatka and fall into the typical range of continental lithospheric mantle worldwide. This rules out significant contributions of slab-derived radiogenic 4He*. The highest 40Ar/36Ar ratios are 400; Ne and Xe isotope ratios are indistinguishable from those in the air. We consider the slab as the initial source of a major portion of these ‘atmospheric’ gases. Element composition of noble gases in olivine differs markedly from that in vein pyroxene indicating that the composition of the fluid phase involved in partial melting was distinct from that during metasomatism. In particular, the harzburgites and veins define distinct linear trends on plots of 3He/36Ar vs. 40Ar/36Ar and of 132Xe/36Ar vs. 40Ar/36Ar. Estimates of ‘mantle’ 132Xe/36Ar values by extrapolating 40Ar/36Ar to 40 000 yield unrealistically high values of 0.5-0.8 (olivine) and 4-5 (vein pyroxene) ruling out a simple two-component mixing of mantle and atmospheric noble gases. Rather a two-stage mixing process applies: (1) Changes in relative proportions of slab-derived element-fractionated atmospheric gases and ‘mantle’ produce two hybrid mixtures dominated by atmospheric

  8. Sexual assault in Ile-Ife, Nigeria

    PubMed Central

    Badejoko, Olusegun Olalekan; Anyabolu, Henry Chineme; Badejoko, Bolaji Olusola; Ijarotimi, Adebimpe Omotade; Kuti, Oluwafemi; Adejuyigbe, Ebunoluwa Aderonke

    2014-01-01

    Background: Sexual assault (SA) is a shattering malevolence against women. This study determined the burden, periodicity, presentation and management of SA in Ile-Ife, Nigeria. Materials and Methods: Retrospective analysis of the hospital records of 76 SA survivors managed over a 5-year period (2007-2011) in Obafemi Awolowo University Teaching Hospitals complex (OAUTHC), Ile-Ife. Results: Sexual assault accounted for 0.69% of all female and 5.2% of all gynaecological emergencies in OAUTHC, Ile-Ife. The survivors’ ages ranged from 4 to 50 years (mean = 17.7 ± 8.8years) and adolescents made up for 48%. The peak prevalence of SA was in February and December and among adults and under-16-year-old survivors, respectively. Daytime and weekday SA were significantly more common among the under-16-year-old survivors (P = 0.008). Majority of the survivors (62%) knew their assailant(s). Neighbours were the commonest perpetrators identified (28.2%) and the assailants’ house was the commonest location (39.4%). Weapons were involved in 29.6% of cases and various injuries were identified in 28.2% of the survivors. Hospital presentation was within 24 hours in majority (76.1%) of the survivors, but rape kit examinations were not performed as the kits were not available. Although appropriate medical management was routinely commenced, only 12.7% of survivors returned for follow-up. Conclusions: Seasonal and diurnal patterns exist in the prevalence of SA in Ile-Ife and most survivors that reported in the hospital presented early. Rape kit examinations were, however, not executed, due to non-availability. Personnel training, protocol development, provision of rape kits and free treatment of SA survivors are, therefore, recommended. Public enlightenment on preventive strategies based on the observed periodicity and age patterns is also suggested. PMID:25013260

  9. Structural and metamorphic evolution of serpentinites and rodingites recycled in the Alpine subduction wedge

    NASA Astrophysics Data System (ADS)

    Zanoni, D.; Rebay, G.; Spalla, M. I.

    2015-12-01

    Hydration-dehydration of mantle rocks affects the viscosity of the mantle wedge and plays a prominent role in subduction zone tectonics, facilitating marble cake-type instead of large-slice dynamics. An accurate structural and petrologic investigation of serpentinites from orogenic belts, supported by their long-lived structural memory, can help to recognize pressure-sensitive mineral assemblages for deciphering their P-prograde and -retrograde tectonic trajectories. The European Alps preserve large volumes of the hydrated upper part of the oceanic lithosphere that represents the main water carrier into the Alpine subduction zone. Therefore, it is important to understand what happens during subduction when these rocks reach P-T conditions proximal to those that trigger the break-down of serpentine, formed during oceanic metamorphism, to produce olivine and clinopyroxene. Rodingites associated with serpentinites are usually derived from metasomatic ocean floor processes but rodingitization can also happen in subduction environments. Multiscale structural and petrologic analyses of serpentinites and enclosed rodingites have been combined to define the HP mineral assemblages in the Zermatt-Saas ophiolites. They record 3 syn-metamorphic stages of ductile deformation during the Alpine cycle, following the ocean floor history that is testified by structural and metamorphic relics in both rock types. D1 and D2 developed under HP to UHP conditions and D3 under lower P conditions. Syn-D2 assemblages in serpentinites and rodingites indicate conditions of 2.5 ± 0.3 GPa and 600 ± 20°C. This interdisciplinary approach shows that the dominant structural and metamorphic imprint of the Zermatt-Saas eclogitized serpentinites and rodingites developed during the Alpine subduction and that subduction-related serpentinite de-hydration occurred exclusively at Pmax conditions, during D2 deformation. In contrast, in the favourable rodingite bulk composition (Ca-rich), hydrated minerals

  10. Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

    USGS Publications Warehouse

    Dusel-Bacon, C.; Lanphere, M.A.; Sharp, W.D.; Layer, P.W.; Hansen, V.L.

    2002-01-01

    We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon-Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215-212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ???188-186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ???135-115 Ma, and muscovite and biotite ???110-108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

  11. Structure and metamorphism of the Franciscan Complex, Mt. Hamilton area, Northern California

    USGS Publications Warehouse

    Blake, M.C., Jr.; Wentworth, C.M.

    1999-01-01

    Truncation of metamorphic isograds and fold axes within coherent terranes of Franciscan metagraywacke by intervening zones of melange indicate that the melange is tectonic and formed after the subduction-related metamorphism and folding. These relations are expressed in two terranes of blueschist-facies rocks of the Franciscan Complex in the Mt. Hamilton area, northern California-the Jurassic Yolla Bolly terrane and the structurally underlying Cretaceous Burnt Hills terrane. Local preservation in both terranes of basal radiolarian chert and oceanic basalt beneath continent-derived metagraywacke and argillite demonstrates thrust repetition within the coherent terranes, although these relations are scarce near Mt. Hamilton. The metagraywackes range from albite-pumpellyite blueschists to those containing well-crystallized jadeitic pyroxene, and a jadeite-in isograd can be defined in parts of the area. Primary bedding defines locally coherent structural orientations and folds within the metagraywacke units. These units are crosscut by thin zones of tectonic melange containing blocks of high-grade blueschist, serpentinite, and other exotic rocks, and a broader, but otherwise identical melange zone marks the discordant boundary between the two terranes.

  12. Alpine Corsica Metamorphic Core Complex

    NASA Astrophysics Data System (ADS)

    Fournier, Marc; Jolivet, Laurent; Goffé, Bruno; Dubois, Roland

    1991-12-01

    Alpine Corsica is an example where superficial nonmetamorphic allochtonous units rest upon a highly strained metamorphic complex. Early ductile deformation under high pressure-low temperature (HP-LT) conditions is due to the westward thrusting of oceanic material onto a continental basement as shown by previous studies. New thermobarometric estimates yield minimal peak HP-LT metamorphism conditions of 11 kbar at 400°C. The early deformation is overprinted by a ductile deformation with an eastward sense of shear postdating or contemporaneous with mineral recrystallizations in the greenschist facies conditions. Early compressive thrust contacts are reworked as east dipping ductile normal faults and the less competent units display only eastward shear criteria. The upper units are affected by an extensional brittle deformation, and east dipping brittle normal faults bound to the west the early to middle Miocene Saint-Florent half-graben. The greenschist metamorphic event lasted until 33 Ma, which is contemporaneous with the beginning of the extension in the Liguro-Provençal basin. We interpret the second deformation stage as the result of a ductile extension following the overthickening of the crust due to the westward thrusting. Extension reduces the thickness of the crust so that upper units free from early P-T conditions are brought into close contact with a HP-LT metamorphic core complex. The geometry of the late extension is controlled by that of the early compressive thrust.

  13. Further evidence of 777 Ma subduction-related continental arc magmatism in Eastern Dom Feliciano Belt, southern Brazil: The Chácara das Pedras Orthogneiss

    NASA Astrophysics Data System (ADS)

    Koester, E.; Porcher, C. C.; Pimentel, M. M.; Fernandes, L. A. D.; Vignol-Lelarge, M. L.; Oliveira, L. D.; Ramos, R. C.

    2016-07-01

    In this study new SHRIMP U-Pb zircon data for the Chácara das Pedras Gneiss in Porto Alegre, southern Brazil are presented. They represent a small exposure of the crust which was intruded by a large volume of orogenic to anorogenic granitoids at ca. 618-562 m.y. in the Eastern Domain of the Dom Feliciano Belt. The Chácara das Pedras tonalitic orthogneiss has geochemical similarities with subduction-related magmatic rocks of continental arcs. They present high Sr initial ratios (∼0.712), negative ɛNd(t = 777) values (∼-6), TDM varying from 1.8 to 2.0 Ga. The igneous protoliths of these orthogneisses were previously considered to be Paleoproterozoic based on an upper intercept age of discordant zircon analyses. In the present study these orthogneisses were re-sampled and re-analyzed in an attempt to obtain more concordant analytical data. The U-Pb zircon analyses were carried out using the SHRIMP IIe at the Laboratório de Geocronologia de Alta Resolução of the Universidade de São Paulo. The U-Pb concordia age obtained for igneous textural domains of the zircon grains is 777 ± 4 Ma. A few analyses on zircon overgrowths give poorly defined late Cryogenian ages of ca. 650 Ma. Older ages, mostly discordant, were obtained in a few zircon cores, showing an upper intercept age of ca. 1.9 Ga. One sample of the Três Figueiras Granodiorite, which crosscut the orthogneiss in the same outcrop, was also investigated. The zircons of this granodiorite are, however, mostly metamitic, preventing the determination of a reliable age. Some concordant analyses from a few grains define ages ranging in the interval between ca. 603 and 1022 Ma. The youngest (ca. 603 Ma) may represent a maximum age for the granodiorite crystallization. Older ages, with discordance <10%, are of 745, 777, 836 and 1022 Ma. The 777 ± 4 Ma age obtained for the Chácara das Pedras orthogneiss is the first Early Cryogenian magmatic age determined for granitoids in the Porto Alegre region, although

  14. Pyroxenite and peridotite xenoliths from Hexigten, Inner Mongolia: Insights into the Paleo-Asian Ocean subduction-related melt/fluid-peridotite interaction

    NASA Astrophysics Data System (ADS)

    Zou, Dongya; Liu, Yongsheng; Hu, Zhaochu; Gao, Shan; Zong, Keqing; Xu, Rong; Deng, Lixu; He, Detao; Gao, Changgui

    2014-09-01

    The in situ major, trace-element and Sr-isotopic compositions of the peridotite and pyroxenite xenoliths from the Hexigten region in the Xing-Meng orogenic belt (XMOB) were examined to evaluate the influences and contributions of the Paleo-Asian Oceanic slab subduction on the lithospheric mantle transformation. Pyroxenes in the Type 1 pyroxenite exhibit low and variable Mg# (67-85) and relatively high 87Sr/86Sr ratios (0.7036-0.7053), indicating that they were formed by assimilation and fractional crystallization processes during a basaltic underplating event. The peridotite and Type 2 pyroxenite xenoliths sampled the lithospheric mantle and recorded subduction-related metasomatism. The mineral chemistries of the Type 1 peridotite suggest that the lithospheric mantle beneath this area suffered 1-15% melt extraction. Clinopyroxene (Cpx) in some Type 1 peridotites are characterized by high (La/Yb)N coupled with marked depletions in high field strength elements (HFSE) (Nb, Ta, Zr, Hf and Ti) and negative correlations between the low Ti/Eu (Nb/La) and 87Sr/86Sr ratios (0.7037-0.7055), suggesting metasomatism by subduction-related CO2-rich fluids. Olivine (Ol) and orthopyroxene (Opx) in the Type 2 peridotite are characterized by a relatively low Mg# but high Ni contents. In addition to the normal incompatible element-depleted Opx, Opx with enrichments in Rb, Ba, Th, U, Nb, Ta and LREE were observed, as well. The Mg# of incompatible element-depleted Opx exhibits weak zonations (i.e., decreasing from the cores to the rims). Cpx and Opx of the Type 2 pyroxenite exhibit similarly high Mg# and Ni contents. Rb, Ba, Th, U, Nb, Ta and LREE contents and 87Sr/86Sr ratios of the Cpx increase from the cores to the rims. Moreover, Opx in the Type 2 peridotite and Cpx in the Type 2 pyroxenite exhibit increased Nb/Ta ratios and Ni contents relative to those in the Type 1 peridotites. These observations collectively suggest a rutile-bearing eclogite-derived silicic melt

  15. Diesel power for Iles de la Madeline

    SciTech Connect

    1996-10-01

    On Iles de la Madeleine, a group of wind-swept islands in the Gulf of St. Lawrence, Quebec, Canada, the economy is built on the summer tourist trade, followed by salt mining and the fishing industry. Like elsewhere, a stable power supply is vital to economic growth. But in winter, when the temperatures tumble, the provision of a constant and reliable power supply becomes, quite literally, a matter of life and death. With this in mind the local utility, Hydro Quebec, decided to build a diesel power station that, despite its sophistication, was a much less expensive option than laying underwater cable to link the islands to the mainland. This article describes the design, specifications and expected operating costs of the installation.

  16. Oxidation during metamorphism of the ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Labotka, Theodore C.

    1993-01-01

    It is suggested that some current concepts about the conditions of metamorphism in ordinary chondrites may be flawed. These meteorites display small systematic variations in the oxidation state of Fe. Evidence is presented that oxidation of Fe is linked to metamorphic grade in types 4-6 ordinary chondrites. This conclusion is at variance with a commonly accepted model for chondrite metamorphism that assumes Fe reduction by graphite.

  17. Metamorphic geology: Why should we care?

    NASA Astrophysics Data System (ADS)

    Tajcmanova, Lucie; Moulas, Evangelos; Vrijmoed, Johannes

    2016-04-01

    Estimation of pressure-temperature (P-T) from petrographic observations in metamorphic rocks has become a common practice in petrology studies during the last 50 years. This data then often serves as a key input in geodynamic reconstructions and thus directly influences our understanding of lithospheric processes. Such an approach might have led the metamorphic geology field to a certain level of quiescence. Obtaining high-quality analytical data from metamorphic rocks has become a standard part of geology studies. The numerical tools for geodynamic reconstructions have evolved to a great extend as well. Furthermore, the increasing demand on using the Earth's interior for sustainable energy or nuclear waste disposal requires a better understanding of the physical processes involved in fluid-rock interaction. However, nowadays, metamorphic data have apparently lost their importance in the "bigger picture" of the Earth sciences. Interestingly, the suppression of the metamorphic geology discipline limits the potential for understanding the aforementioned physical processes that could have been exploited. In fact, those phenomena must be considered in the development of new generations of fully coupled numerical codes that involve reacting materials with changing porosity while obeying conservation of mass, momentum and energy. In our contribution, we would like to discuss the current role of metamorphic geology. We will bring food for thoughts and specifically touch upon the following questions: How can we revitalize metamorphic geology? How can we increase the importance of it? How can metamorphic geology contribute to societal issues?

  18. In situ rutile petrochronology: texture-related T, Paleoproterozoic inheritance and a Pan-African overprint in the oldest subduction-related eclogites, Usagaran Orogen, Tanzania

    NASA Astrophysics Data System (ADS)

    Moeller, A.; Kraus, K.; Herms, P.; Appel, P.; Raase, P.

    2014-12-01

    Rutile U-Pb thermochronology is applied successfully by both TIMS and beam methods to date cooling events in mafic and metapelitic rocks, as well as in detrital studies. The Zr-in-rutile thermometer is very robust to thermal diffusion, and generally requires complete recrystallization to change recorded crystallization temperatures. Evidence for diffusion of HFSE elements in rutile is sparse; whereas U-Pb chronology generally records diffusion controlled cooling from the last event. This study follows conventional thermobarometry and U-Pb TIMS results on monazite, sphene and rutile of Möller et al. (1995) establishing a 2 Ga eclogite facies event from MORB-like metabasic, and metapelitic rocks in the Usagaran Orogen of Tanzania, interpreted to be the oldest outcrops of subduction-related eclogites. Rutile from both rock types were discordant near a ca. 500 Ma lower intercept, confirming a thermal overprint postulated on the basis of K-Ar and Rb-Sr mica ages by e.g. Wendt et al. (1972). The age of the eclogite-facies event was confirmed by U-Pb zircon dating of a 1991±2 Ma crosscutting pegmatite (Collins et al., 1999). We present in situ LA-ICP-MS rutile petrochronology on five metabasic and metapelitic eclogite facies samples with variable retrograde amphibolite-facies recrystallization. Thermometry confirms conventional Fe-Mg results, including higher peak temperatures in metabasites. Traverses on rutile inclusions in large garnet prophyroblasts in metapelites show increasing temperatures from cores outwards and a slight decrease towards outermost rims, with peak T coinciding with highest Mg# and highest grossular content, hence consistent with preservation of prograde zoning in the garnets and a brief eclogite facies event. Large rutiles (800μm) in recrystallized samples record temperature zoning profiles. U-Pb results show inheritance of near concordant 2 Ga domains, but dominantly confirm the ca. 490 Ma amphibolite facies overprint. The study is an excellent

  19. Paleo-Asian oceanic subduction-related modification of the lithospheric mantle under the North China Craton: Evidence from peridotite xenoliths in the Datong basalts

    NASA Astrophysics Data System (ADS)

    Wang, Chengyuan; Liu, Yongsheng; Min, Ning; Zong, Keqing; Hu, Zhaochu; Gao, Shan

    2016-09-01

    geophysical research, it is speculated that the carbonatitic melt was derived from the carbonated pelite carried by the southward subducted PAOP under the NCC. The PAOP subduction-related carbonatitic melt-peridotite reaction could have contributed to the transformation of the lithospheric mantle beneath the northern margin of the NCC.

  20. Subduction-related High- to Ultrahigh-Potassic Rocks of the Ankara-Erzincan Suture Belt of Turkey: a geochemical and isotopic approach to source and petrogenesis

    NASA Astrophysics Data System (ADS)

    Genc, S. Can; Gulmez, Fatma; Karacik, Zekiye; Tuysuz, Okan; Prelevic, Dejan; Roden, Michael F.; Hames, Willis E.; Zeki Billor, M.

    2014-05-01

    A Late Cretaceous Volcano-sedimantary Succession (LCVS) trends parallel to Neo-Tethyan Suture in North Central Anatolia. Volcanic members of the LCVS consist mainy of coeval leucite phonolite/tephrites, trachytes, lamprophyres and andesitic rocks. Obtained Ar-Ar ages reveal that the volcanic activity occurred between 73.6±0.18 and 76.78±0.19 Ma, contemporaneous with the subduction of the Neo-Tethyan ocean beneath the Pontides. The volcanic rocks of LCVS are classified as alkaline, High- to ultrahigh-K, and silica-saturated and silica-unsaturated, geochemically. Rare calc-alkaline andesitic lavas are also occur within the volcanic sucession. Except the calc-alkaline samples, magmatic members of LCVS have similar major and trace element concentrations similar to the plagioleucitites or ultrapotassic rocks of the active orogenic zones (i.e. the Roman Province ultrapotassic series, Peccerillo, 2005). The multi element patterns on N-MORB- and Chondrite-normalized spider diagrams are characterized by significant LILE and LREE enrichments relative to HFSE and HREE, and display apparent Nb and Ta depletions, implying the subduction-related magmas. 87Sr/86Sr(i) (0.704493-0.706090) and 143Nd/144Nd(i) (0.512523-0.512680) isotope ratios are close to the mantle array, and are also in between the Aeolian Islands CA-Potassic rocks (Peccerillo, 2005), BSE and the circum-Mediterranean anorogenic Cenozoic igneous province (CiMACI, Lustrino&Wilson, 2007). Variable Mg# (33-60) evidences that these rocks are the products of evolved melts. The lead isotope values display a trend between EMI and DM, suggesting that the crustal involvement is more effective process during the generation of some lamprophyres relative to the other ultrapotassic rocks of LCVS. The results of clinopyroxene thermobarometry calculations reveal significant differences in depth of crystallization for the rock suites. Some trace element abundances and inter elemental ratios together with their co-variations show

  1. Shock metamorphism of carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Scott, Edward R. D.; Keil, Klaus; Stoeffler, Dieter

    1992-01-01

    Shock effects were studied in 69 carbonaceous chondrites, including CM2, CO3, CV3, ungrouped C2-C4, and CK4-6 chondrites, using optical microscopy of thin sections. It is shown that the classification scheme of Stoeffler et al. (1991) for the progressive stages of shock metamorphism in ordinary chondrites is also applicable to carbonaceous chondrites. On the basis of shock effects in olivine, the 69 carbonaceous chondrites could be assigned to four shock stage, S1 to S4. The CM2 and CO3 groups were found to be the least shocked chondrite groups, whereas the CK4-6 and CV3 were the most strongly shocked groups.

  2. Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa.

    PubMed

    Moyen, Jean-François; Stevens, Gary; Kisters, Alexander

    2006-08-01

    Although plate tectonics is the central geological process of the modern Earth, its form and existence during the Archaean era (4.0-2.5 Gyr ago) are disputed. The existence of subduction during this time is particularly controversial because characteristic subduction-related mineral assemblages, typically documenting apparent geothermal gradients of 15 degrees C km(-1) or less, have not yet been recorded from in situ Archaean rocks (the lowest recorded apparent geothermal gradients are greater than 25 degrees C km(-1)). Despite this absence from the rock record, low Archaean geothermal gradients are suggested by eclogitic nodules in kimberlites and circumstantial evidence for subduction processes, including possible accretion-related structures, has been reported in Archaean terrains. The lack of spatially and temporally well-constrained high-pressure, low-temperature metamorphism continues, however, to cast doubt on the relevance of subduction-driven tectonics during the first 1.5 Gyr of the Earth's history. Here we report garnet-albite-bearing mineral assemblages that record pressures of 1.2-1.5 GPa at temperatures of 600-650 degrees C from supracrustal amphibolites from the mid-Archaean Barberton granitoid-greenstone terrain. These conditions point to apparent geothermal gradients of 12-15 degrees C-similar to those found in recent subduction zones-that coincided with the main phase of terrane accretion in the structurally overlying Barberton greenstone belt. These high-pressure, low-temperature conditions represent metamorphic evidence for cold and strong lithosphere, as well as subduction-driven tectonic processes, during the evolution of the early Earth. PMID:16885983

  3. Thermal metamorphism. [of chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Sears, Derek W. G.; Dodd, Robert T.

    1988-01-01

    Most chondrites have experienced thermal metamorphism, resulting in changes in texture, mineralogy and possibly chemical composition. The physical conditions for metamorphism range from approximately 400 to 1000 C at low lithostatic pressure. Metamorphism may have resulted from decay of short-lived radionuclides, electromagnetic induction or accretion of hot materials. Several thermal models for chondrite parent bodies have been proposed. The least metamorphosed type-3 chondrites probably carry the most information about the early solar system, but even these have been affected to some degree by thermal processing.

  4. The Longwood Igneous Complex, Southland, New Zealand: A Permo-Jurassic, intra-oceanic, subduction-related, I-type batholithic complex

    NASA Astrophysics Data System (ADS)

    Price, Richard; Spandler, Carl; Arculus, Richard; Reay, Anthony

    2011-09-01

    The Longwood Igneous Complex (LIC) is located in Southland, New Zealand on the eastern side of the Carboniferous to Cretaceous, I-type, Median Batholith. Intrusives of the Complex range in age from Permian to Jurassic and show trace element characteristics typical of subduction-related magmas. Gabbro, gabbroic diorite and basaltic dyke rocks show trace and minor element patterns and isotopic compositions indicating that they represent magmas generated in an intra-oceanic subduction system. Radiometric ages decrease across the LIC from 254 Ma in the east to 142 Ma in the west and mineral chemistry and mineral phase relationships indicate emplacement at depths between 15 and 25 km. Thus the petrology and geochemistry of the LIC provides the basis for evaluating the composition of lower-middle crust assembled above a long lived intra-oceanic subduction system and we estimate this to be andesitic and similar to bulk continental crust. Rocks of the LIC range in composition from troctolite and gabbro through diorite to trondhjemite and granite. All of the ultramafic rocks and most of the gabbros have petrographic and geochemical features consistent with a cumulate origin and mineral chemistry shows similarities with arc cumulate sequences from elsewhere. Few of the plutonic rocks making up the LIC have direct analogues among modern intra-oceanic volcanic rocks. The latter are the end products and the former the leftovers from magmatic processes that included fractional crystallisation, crustal assimilation and magma mixing and mingling. Longwood intrusions do not represent magma chambers. They formed as crystal cumulates and mushes left over from the processes that generated magmas erupted at the contemporary volcanic arc. A correlation between decreasing age of emplacement and Sr and Nd isotopic compositions and inheritance in zircons dated by ion probe are indications of crustal recycling. The generation of felsic rocks in the Longwood intra-oceanic arc involved

  5. Development of inverted metamorphic isograds in the western metamorphic belt, Juneau, Alaska

    USGS Publications Warehouse

    Himmelberg, G.R.; Brew, D.A.; Ford, A.B.

    1991-01-01

    An inverted metamorphic gradient is preserved in the western metamorphic belt near Juneau, Alaska. Detailed mapping of pelitic single-mineral isograds, systematic changes in mineral assemblages, and silicate geothermometry indicate that thermal peak metamorphic conditions increase structurally upward over a distance of about 8 km. Silicate geobarometry suggests that the thermal peak metamorphism occurred under pressures of 9-11 kbar. Our preferred interpretation of the cause of the inverted gradient is that it formed during compression of a thickened wedge of relatively wet and cool rocks in response to heat flow associated with the formation and emplacement of tonalite sill magma. -from Authors

  6. Shock metamorphism of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Stoeffler, Dieter; Keil, Klaus; Scott, Edward R. D.

    1991-01-01

    This study proposes a revised petrographic classification of progressive stages of shock metamorphism of 26 ordinary chondrites. Six stages of shock (S1 to S6) are defined on the basis of shock effects in olivine and plagioclase as recognized by thin section microscopy, and the characteristic shock effects of each shock stage are described. It is concluded that shock effects and the sequence of progressively increasing degrees of shock metamorphosis are very similar in H, L, and LL groups. Differences in the frequency distribution of shock stages are relatively minor. It is suggested that the collisional histories of the H, L, and LL parent bodies were similar. Petrologic type-3 chondrites are deficient in stages S4 and S6 and, with increasing petrologic type, the frequency of stages S4 to S6 increases. It is suggested that the more porous and volatile-rich Type-3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type. Stage S3 is the most abundant in nearly all petrologic types.

  7. Fluid-absent metamorphism in the Adirondacks

    NASA Astrophysics Data System (ADS)

    Valley, J. W.

    Results on late Proterozoic metamorphism of granulite in the Adirondacks are presented. There more than 20,000 sq km of rock are at granulite facies. Low water fugacites are implied by orthopyroxene bearing assemblages and by stability of k'spar-plag-quartz assemblages. After mentioning the popular concept of infiltration of carbon dioxide into Precambrian rocks and attendent generation of granulite facies assemblages, several features of Adirondack rocks pertinent to carbon dioxide and water during their metamorphism are summarized: wollastonite occurs in the western lowlands; contact metamorphism by anorthosite preceeding granulite metamorphism is indicated by oxygen isotopes. Oxygen fugacity lies below that of the QFM buffer; total P sub water + P sub carbon dioxide determined from monticellite bearing assemblages are much less than P sub total (7 to 7.6 kb). These and other features indicate close spatial association of high- and low-P sub carbon dioxide assemblages and that a vapor phase was not present during metamorphism. Thus Adirondack rocks were not infiltrated by carbon dioxide vapor. Their metamorphism, at 625 to 775 C, occurred either when the protoliths were relatively dry or after dessication occurred by removal of a partial melt phase.

  8. Fluid-absent metamorphism in the Adirondacks

    NASA Technical Reports Server (NTRS)

    Valley, J. W.

    1986-01-01

    Results on late Proterozoic metamorphism of granulite in the Adirondacks are presented. There more than 20,000 sq km of rock are at granulite facies. Low water fugacites are implied by orthopyroxene bearing assemblages and by stability of k'spar-plag-quartz assemblages. After mentioning the popular concept of infiltration of carbon dioxide into Precambrian rocks and attendent generation of granulite facies assemblages, several features of Adirondack rocks pertinent to carbon dioxide and water during their metamorphism are summarized: wollastonite occurs in the western lowlands; contact metamorphism by anorthosite preceeding granulite metamorphism is indicated by oxygen isotopes. Oxygen fugacity lies below that of the QFM buffer; total P sub water + P sub carbon dioxide determined from monticellite bearing assemblages are much less than P sub total (7 to 7.6 kb). These and other features indicate close spatial association of high- and low-P sub carbon dioxide assemblages and that a vapor phase was not present during metamorphism. Thus Adirondack rocks were not infiltrated by carbon dioxide vapor. Their metamorphism, at 625 to 775 C, occurred either when the protoliths were relatively dry or after dessication occurred by removal of a partial melt phase.

  9. Grampian high-pressure-granulite-facies metamorphism of the Slishwood Division, NW Ireland and its enigmatic eclogite-facies precursor

    NASA Astrophysics Data System (ADS)

    Daly, J. S.; Flowerdew, M. J.; Whitehouse, M. J.

    2012-04-01

    opening of the Iapetus ocean. This rifting event produced a suite of metagabbroic intrusives at c. 596 ± 6 Ma. Burial of the microcontinent to depths of at least 45 km (ref. 2) resulted in eclogite facies metamorphism. Partial decompression to high pressure granulite conditions (c. 33 km depth) occurred during or before subduction-related magmatism that produced the tonalites. Docking of the Slishwood microcontinent took place during the Grampian collision. Potentially the entire metamorphic history took place with a few million years close to 470 Ma.

  10. Low-grade, M1 metamorphism of the western metamorphic belt near Juneau, Alaska

    SciTech Connect

    Himmelberg, G.R. . Dept. of Geology); Brew, D.A.; Ford, A.B. )

    1993-04-01

    The western metamorphic belt is part of the Coast plutonic-metamorphic complex of western Canada and southeastern Alaska that developed as a result of tectonic overlap and/or compressional thickening of crustal rocks during collision of the Alexander terrane and Gravina assemblage on the west against the Yukon Prong and Stikine terranes to the east. Sub-greenschist to lower greenschist facies metabasalts exposed along the west end of the western metamorphic belt near Juneau, Alaska record the earliest metamorphic event (M1). These low-grade rocks are gradational with younger, higher-grade assemblages that define an inverted metamorphic gradient (metamorphic event M5). The most common metamorphic mineral assemblages are chlorite-epidote-actinolite with or without pumpellyite and stilpnomelane. There is no systematic distribution of metamorphic mineral assemblages in the study area, and all assemblages are in the pumpellyite-actinolite facies near the transition to the lower greenschist facies. Different low-variance assemblages can be attributed to minor differences in pressure, temperature, or X[sub CO[sub 2

  11. The effect of yeast weight and temperature on ethanol production from sorghum and iles-iles flour

    NASA Astrophysics Data System (ADS)

    Kusmiyati, Shitophyta, Lukhi Mulia

    2015-12-01

    An increased of human need that spend a lot of energy, especially fuel resulting in excessive energy consumption. Therefore, the existence of alternative energy that renewable and environmentally friendly, such as bioethanol is required. In this study the use of sorghum and iles-iles as raw materials for bioethanol production were investigated. The variables studied were the saccharification time, weight of dry yeast Saccharomyces cerevisiae added in the starter culture (2.5, 5, 10, 15, 20 g) and fermentation temperature (30, 35, 40, 45, 50°C). Bioethanol production consisted of the enzymatic hydrolysis (liquefaction and saccharification), and fermentation. For liquefaction, 1.6% v/w α-amylase enzyme, 1 hour, T = 95-100° C, pH 6 were used. For saccharification, 3.2% v/w b-amylase enzyme, time 4,8,24,48 hours, T = 60°C, pH 5 were used. For fermentation, Saccharomyces cerevisiae yeast were used with conditions of time for 120 hours, pH 4.5. The effect of dry yeast weight and fermentation temperature indicated that 15 g yeast weight and temperature 30° C were found to be the best condition which resulted the highest ethanol concentration of 85.20 g/L and 79.94 g/L for sorghum and iles-iles flour, respectively.

  12. Trace element partitioning in rock forming minerals of co-genetic, subduction-related alkaline and tholeiitic mafic rocks in the Ural Mountains, Russia

    NASA Astrophysics Data System (ADS)

    Krause, J.; Brügmann, G. E.; Pushkarev, E. V.

    2009-04-01

    The partitioning of trace elements between rock forming minerals in igneous rocks is largely controlled by physical and chemical parameters e.g. temperature, pressure and chemical composition of the minerals and the coexisting melt. In the present study partition coefficients for REE between hornblende, orthopyroxene, feldspars, apatite and clinopyroxene in a suite of co-genetic alkaline and tholeiitic mafic rocks from the Ural Mountains (Russia) were calculated. The results give insights to the influence of the chemical composition of the parental melt on the partitioning behaviour of the REE. Nepheline-bearing, alkaline melanogabbros (tilaites) are assumed to represent the most fractionated products of the melt that formed the ultramafic cumulates in zoned mafic-ultramafic complexes in the Ural Mountains. Co-genetic with the latter is a suite of olivine gabbros, gabbronorites and hornblende gabbros formed from a tholeiitic parental melt. Negative anomalies for the HFSE along with low Nb and Ta contents and a positive Sr anomaly indicate a subduction related origin of all parental melts. The nepheline gabbros consist predominantly of coarse-grained clinopyroxene phenocrysts in a matrix of fine grained clinopyroxene, olivine, plagioclase, K-feldspar and nepheline with accessory apatite. The tholeiitic gabbros have equigranular to porphyric textures with phenocrysts of olivine, pyroxene and hornblende in a plagioclase rich matrix with olivine hornblende, pyroxene and accessory apatite. Element concentrations of adjacent matrix grains and rims of phenochrysts were measured with LA-ICPMS. The distribution of REE between hornblende and clinopyroxene in the tholeiitic rocks is similar for most of the elements (DHbl•Cpx(La-Tm) = 2.7-2.8, decreasing to 2.6 and 2.4 for Yb and Lu, respectively). These values are about two times higher than published data (e.g. Ionov et al. 1997). Partition coefficients for orthopyroxene/clinopyroxene systematically decrease from the HREE

  13. The Mythology of Metamorphic Fluid Expulsion

    NASA Astrophysics Data System (ADS)

    Connolly, James

    2010-05-01

    Regional metamorphism occurs in an ambiguous rheological regime between the brittle upper crust and ductile sub-lithospheric mantle. This ambiguous position has allowed two schools of thought to develop concerning the nature of metamorphic fluid flow. The classical school holds that metamorphic rocks are inviscid and that any fluid generated by devolatilization is squeezed out of rocks as rapidly as it is produced. According to this school permeability is a dynamic property and fluid flow is upward. In contrast the modern school, selectively uses concepts from upper crustal hydrology that presume implicitly, if not explicitly, that rocks are rigid or, at most, brittle. For the modern school, the details of crustal permeability determine fluid flow and as these details are poorly known almost anything is possible. Reality, to the extent that is reflected by field studies, offers some support to both schools. In particular, evidence of significant lateral and chanellized fluid flow are consistent with flow in rigid media, while evidence for short (104 - 105 y) grain-scale fluid rock interaction during much longer metamorphic events, suggests that reaction-generated grain-scale permeability is sealed rapidly by compaction; a phenomenon that is also essential to prevent extensive retrograde metamorphism. These observations provide a compelling argument for recognizing in conceptual models for metamorphic fluid flow that rocks are neither inviscid nor rigid, but have finite strength. The surprising result of this strength is that the steady state solutions for fluid flow in porous compacting media require that fluid expulsion is channeled into waves of fluid-filled porosity. The waves develop on a characteristic length scale known as the viscous compaction length, δ, that is also the length scale for lateral fluid flow. In this context, porosity refers to any hydraulically connected void space present on spatial scales

  14. Is the Arabian Nubian Shield with Westward Subduction Polarity? Clues from Prograding Metamorphism in Mantle Peridotites, Eastern Desert of Egypt.

    NASA Astrophysics Data System (ADS)

    Gamal El Dien, H. M.; Abu El-Ela, A. S.; Hamdy, M.; Hassan, A.

    2014-12-01

    Neoproterozoic arc mantle beneath the Arabian Nubian Shield (ANS) in the Eastern Desert (ED) of Egypt exhumed due to intra-oceanic upthrusting are represented mainly by exposed ophiolitic peridotites serpentinized to different degree. Metamorphism is related to the Pan-African collision and the subduction of oceanic lithosphere. However, polarity of the Pan-African intra-oceanic subduction is still questionable. We here trace the variation of the degree of serpentinization and regional metamorphism of six serpentinite masses, widely distributed in the ED (from the east to the west: W (Wadi). Alam, W. Igla, W. Mubarak, G. El-Maiyit, W. Um El Saneyat and W. Atalla). This is based on their mineralogy, textures and mineral chemistry. Much difference in the degree of serpentinization is obvious among these rocks. They are mainly partly serpentinized containing primary olivine and orthopyroxene at W. Alam and W. Igla, while they are completely serpentinized in the other localities. With the increased degree of metamorphism, textures were transformed from the pseudomorphic to the non-pseudomorphic. The most common retrograde assemblage is composed of lizardite _ chrysotile_ brucite_ magnetite. The serpentine prograde textures can be viewed as a continuum from retrograde lizardite pseudomorphic textures, to very fine-grained transitional texture of lizardite and chrysotile, to chrysotile antigorite interlocking texture and finally to antigorite interpenetrating texture. These textures appear to represent successive stages in a recrystallization event. In late subduction-related metamorphism and early collisional emplacement stage, mylonitic-antigorite serpentinites formed and antigorite became the major phase in G. El-Maiyit, Um El-Saneyat andW. Atalla. Compositional zoning in spinel grains in all serpentinites reflect variation in the degree of alteration. The biggest variation of spinel compositions are among serpentinites from Um El-Saneyat and W. Atalla. The alteration

  15. The Mesozoic Caosiyao giant porphyry Mo deposit in Inner Mongolia, North China and Paleo-Pacific subduction-related magmatism in the northern North China Craton

    NASA Astrophysics Data System (ADS)

    Wu, Huaying; Zhang, Lianchang; Pirajno, Franco; Shu, Qihai; Zhang, Min; Zhu, Mingtian; Xiang, Peng

    2016-09-01

    The Caosiyao giant porphyry Mo deposit is located in the Wulanchabu area of Inner Mongolia, within the northern North China Craton (NCC). It contains more than 2385 Mt of ore with an average grade of 0.075% Mo. In the Caosiyao mining district, Mo mineralization occurs mainly in a Mesozoic granite porphyry as disseminations and stockworks, with some Mo distributed in Archean metamorphic rocks and diabase as stockworks and veins. The host granite porphyry is composed of two different phases that can be distinguished based on mineral assemblages and textures: one phase contains large and abundant phenocrysts (coarse-grained), while the other phase is characterized by fewer and smaller phenocrysts (medium-grained). Zircon U-Pb-Hf analyses of the former phase yielded a concordant 206Pb/238U age of 149.8 ± 2.4 Ma with a 206Pb/238U weighted mean age of 149.9 ± 2.4 Ma and εHf(t) values ranging from -12.2 to 18.3, while the latter phase gave a concordant 206Pb/238U age of 149.0 ± 2.2 Ma with a 206Pb/238U weighted mean age of 149.0 ± 2.1 Ma and εHf(t) values ranging from -13.1 to 17.7. Five samples of disseminated molybdenite have a 187Re-187Os isochron age of 149.5 ± 5.3 Ma with a weighted average age of 149.0 ± 1.8 Ma, whereas six veinlet-type molybdenite samples have a well-constrained 187Re-187Os isochron age of 146.9 ± 3.1 Ma and a weighted average age of 146.5 ± 0.8 Ma. Thus, it is suggested that the Mo mineralization of the Caosiyao deposit occurred during the Late Jurassic (ca. 147-149 Ma), almost coeval with the emplacement of the host granite porphyry (ca. 149-150 Ma). The host granite porphyry is characterized by high silica (SiO2 = 71.52-74.10 wt%), relatively high levels of oxidation (Fe2O3/FeO = 0.32-0.94 wt%) and high alkali element concentrations (Na2O + K2O = 8.21-8.76 wt%). The host granite porphyry also shows enrichments in U and K, and depletion in Ba, Sr, P, Eu, and Ti, suggesting strong fractional crystallization of plagioclase, biotite, and

  16. Platy Hematite and Metamorphism on Mars

    NASA Technical Reports Server (NTRS)

    Lane, M. D.; Morris, R. V.; Hartmann, W. K.; Christensen, P. R.; Mertzman, S. A.

    2002-01-01

    Emissivity spectra of Sinus Meridiani, Mars suggest that the hematite consists of platy particles that occur as consolidated, schistose lenses or loose, platy particles. This platy hematite may have originated as a result of burial metamorphism. Additional information is contained in the original extended abstract.

  17. Chemical demineralization of different metamorphic grade coals

    SciTech Connect

    Yusupov, T.S.; Shumskaya, L.G.; Burdukov, A.P.

    2009-07-15

    The paper analyzes a process of deep mineralization of various metamorphic grade coals pre-ground in different destructive units, namely, in centrifugal-planetary mill and disintegrator. Coal dispergation in higher energy intensive mills greatly enhances inorganic component extraction to acidic solutions. This is explained by distortion of crystal structure and amorphization of minerals under various kinds and different intensity mechanical actions.

  18. Metamorphic conditions in the Ashe Metamorphic Suite, North Carolina Blue Ridge

    SciTech Connect

    McSween, H.Y. Jr. ); Abbott, R.N.; Raymond, L.A. )

    1989-12-01

    Taconian metamorphism of mafic rocks in the Ashe Metamorphic Suite can be characterized by reference to an isograd corresponding to the reaction bio + epi = hbl + gar, which separates rocks into two zones of low-variance assemblages. Temperatures and pressures estimated from mineral exchange geothermometers and a barometer suggest that this reaction occurred at approximately 600-650C and 7.5 kbar. Phase equilibria between biotite and hornblende, as well as the sharpness of the mapped isograd, indicate that the reaction is discontinuous. Inferred differences in metamorphic grade between Ashe amphibolites and mafic dikes in the underlying basement suggest that these units are in faulted contact. Isograd patterns in pelitic rocks suggest an elongated domal uplift that developed after metamorphism and thrusting, the core of which is exposed in the adjacent Grandfather Mountain window.

  19. Paleoproterozoic high-pressure metamorphism in the northern North China Craton and implications for the Nuna supercontinent.

    PubMed

    Wan, Bo; Windley, Brian F; Xiao, Wenjiao; Feng, Jianyun; Zhang, Ji'en

    2015-01-01

    The connection between the North China Craton (NCC) and contiguous cratons is important for the configuration of the Nuna supercontinent. Here we document a new Paleoproterozoic high-pressure (HP) complex dominated by garnet websterite on the northern margin of the NCC. The peak metamorphism of the garnet websterite was after ∼1.90 Ga when it was subducted to eclogite facies at ∼2.4 GPa, then exhumed back to granulite facies at ∼0.9 GPa before ∼1.82 Ga. The rock associations with their structural relationships and geochemical affinities are comparable to those of supra-subduction zone ophiolites, and supported by subduction-related signatures of gabbros and basalts. We propose that a ∼1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northern margin of the NCC. Presence of the coeval Sharyzhalgai complex with comparable HP garnet websterites in the southern Siberian active margin favours juxtaposition against the NCC in the Paleoproterozoic. PMID:26388458

  20. Orogenesis, high-T thermal events, and gold vein formation within metamorphic rocks of the Alaskan Cordillera

    USGS Publications Warehouse

    Goldfarb, R.J.; Snee, L.W.; Pickthorn, W.J.

    1993-01-01

    Mesothermal, gold-bearing quartz veins are widespread within allochthonous terranes of Alaska that are composed dominantly of greenschist-facies metasedimentary rocks. The most productive lode deposits are concentrated in south-central and southeastern Alaska; small and generally nonproductive gold-bearing veins occur upstream from major placer deposits in interior and northern Alaska. Ore-forming fluids in all areas are consistent with derivation from metamorphic devolatilisation reactions, and a close temporal relationship exists between high-T tectonic deformation, igneous activity, and gold mineralization. Ore fluids were of consistently low salinity, CO2-rich, and had ??18O values of 7 ???-12??? and ??D values between -15??? and -35???. Upper-crustal temperatures within the metamorphosed terranes reached at least 450-500??C before onset of significant gold-forming hydrothermal activity. In southern Alaska, gold deposits formed during latter stages of Tertiary, subduction-related, collisional orogenesis and were often temporally coeval with calc-alkaline magmatism. -from Authors

  1. Paleoproterozoic high-pressure metamorphism in the northern North China Craton and implications for the Nuna supercontinent

    PubMed Central

    Wan, Bo; Windley, Brian F.; Xiao, Wenjiao; Feng, Jianyun; Zhang, Ji'en

    2015-01-01

    The connection between the North China Craton (NCC) and contiguous cratons is important for the configuration of the Nuna supercontinent. Here we document a new Paleoproterozoic high-pressure (HP) complex dominated by garnet websterite on the northern margin of the NCC. The peak metamorphism of the garnet websterite was after ∼1.90 Ga when it was subducted to eclogite facies at ∼2.4 GPa, then exhumed back to granulite facies at ∼0.9 GPa before ∼1.82 Ga. The rock associations with their structural relationships and geochemical affinities are comparable to those of supra-subduction zone ophiolites, and supported by subduction-related signatures of gabbros and basalts. We propose that a ∼1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northern margin of the NCC. Presence of the coeval Sharyzhalgai complex with comparable HP garnet websterites in the southern Siberian active margin favours juxtaposition against the NCC in the Paleoproterozoic. PMID:26388458

  2. Paleoproterozoic high-pressure metamorphism in the northern North China Craton and implications for the Nuna supercontinent

    NASA Astrophysics Data System (ADS)

    Wan, Bo; Windley, Brian F.; Xiao, Wenjiao; Feng, Jianyun; Zhang, Ji'en

    2015-09-01

    The connection between the North China Craton (NCC) and contiguous cratons is important for the configuration of the Nuna supercontinent. Here we document a new Paleoproterozoic high-pressure (HP) complex dominated by garnet websterite on the northern margin of the NCC. The peak metamorphism of the garnet websterite was after ~1.90 Ga when it was subducted to eclogite facies at ~2.4 GPa, then exhumed back to granulite facies at ~0.9 GPa before ~1.82 Ga. The rock associations with their structural relationships and geochemical affinities are comparable to those of supra-subduction zone ophiolites, and supported by subduction-related signatures of gabbros and basalts. We propose that a ~1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northern margin of the NCC. Presence of the coeval Sharyzhalgai complex with comparable HP garnet websterites in the southern Siberian active margin favours juxtaposition against the NCC in the Paleoproterozoic.

  3. Transthyretin Ile 122 and cardiac amyloidosis in African-Americans. 2 case reports.

    PubMed Central

    Jacobson, D R; Ittmann, M; Buxbaum, J N; Wieczorek, R; Gorevic, P D

    1997-01-01

    Two cases of cardiac amyloidosis resulting from deposition of the Ile 122 variant of transthyretin in African-Americans are presented. These cases illustrate several typical features of this disorder, including electrocardiographic abnormalities and digoxin toxicity. Transthyretin Ile 122 is a common amyloidogenic variant in African-Americans (present as a heterozygous variant in 4% of this population); therefore, the diagnosis of transthyretin Ile 122 cardiac amyloidosis should be considered in African-Americans with unexplained restrictive cardiomyopathy or arrhythmias. Images PMID:9068139

  4. The Beimarang mélange (southern Tibet) brings additional constraints in assessing the origin, metamorphic evolution and obduction processes of the Yarlung Zangbo ophiolite

    NASA Astrophysics Data System (ADS)

    Huot, François; Hébert, Réjean; Varfalvy, Véronika; Beaudoin, Georges; Wang, Chengshan; Liu, Zhifei; Cotten, Jo; Dostal, Jaroslav

    2002-12-01

    The Beimarang massif is one of many ophiolitic remnants which crop out discontinuously along the Yarlung Zangbo suture zone in southern Tibet. The southern contact of these remnants is marked by a highly sheared serpentinite mélange made up of blocks of serpentinites, diabases, gabbros and composite blocks of serpentinites and mafic injections. The Beimarang mélange has been investigated in order to bring additional constraints on the origin, metamorphic evolution and obduction processes of the Yarlung Zangbo ophiolite. Petrography and geochemical data suggest that the ultramafic components are similar to moderately depleted upper mantle peridotites. They may represent the already cooled and serpentinized Tethyan upper mantle which was trapped in a mantle wedge at the onset of a north-dipping Early Cretaceous intra-oceanic subduction zone located south of the Gangdese arc. These peridotites were then intruded by back-arc-like mafic magmas whose moderately depleted mantle source was affected by a subduction component. Ultramafic and mafic secondary mineral assemblages suggest that early low-( P/ T) metamorphic intra-oceanic conditions reached the amphibolite facies (>550 °C) before being retrograded down to the pumpellyite-prehnite facies (<280 °C). The Beimarang mélange, interpreted as an obduction mélange formed near a spreading ridge, was subjected to metamorphic conditions in the pumpellyite-prehnite facies which favored re-serpentinization of the peridotites and partial rodingitization of the mafic rocks. Unlike subduction-related mélanges and their associated lithological units found in the Ladakh area, we found no evidence of high-( P/ T) conditions in lithologies from the Beimarang mélange.

  5. Carbonic metamorphism, granulites and crustal growth

    NASA Technical Reports Server (NTRS)

    Newton, R. C.; Smith, J. V.; Windley, B. F.

    1980-01-01

    Stabilization of early crust against melting by high radioactivity and against resorption into the mantle by fast convective overturn requires that water and heat producers were flushed upwards within 50 Myr of accretion. Creation of a refractory base of granulite by metamorphism associated with CO2 vapour explains CO2-rich fluid inclusions in ancient high-grade rocks, minor-element depletions and local phenomena of arrested development of charnockite in Precambrian terrains. The hot-spot and plate-tectonic models of Precambrian crustal evolution lead to different schemes for CO2 delivery to continental roots. New tectonic concepts may be needed to explain carbonic metamorphism and other features of early crustal evolution.

  6. Heat transfer by fluids in granulite metamorphism

    NASA Technical Reports Server (NTRS)

    Morgan, Paul; Ashwal, Lewis D.

    1988-01-01

    The thermal role of fluids in granulite metamorphism was presented. It was shown that for granulites to be formed in the middle crust, heat must be advected by either magma or by volatile fluids, such as water or CO2. Models of channelized fluid flow indicate that there is little thermal difference between channelized and pervasive fluid flow, for the same total fluid flux, unless the channel spacing is of the same order or greater than the thickness of the layer through which the fluids flow. The volumes of volatile fluids required are very large and are only likely to be found associated with dehydration of a subducting slab, if volatile fluids are the sole heat source for granulite metamorphism.

  7. Slavery, smallpox, and revolution: 1792 in Ile de France (Mauritius).

    PubMed

    Vaughan, M

    2000-12-01

    In 1792 a slave-ship arrived on the french Indian Ocean island of Ile de France (Mauritius) from South India, bringing with it smallpox. As the epidemic spread, a heated debate ensued over the practice of inoculation. The island was in the throes of revolutionary politics and the community of French colonists were acutely aware of their new rights as 'citizens'. In the course of the smallpox epidemic, many of the political tenisons of the period came to focus on the question of inoculation, and were played out on the bodies of slaves. Whilst some citizens asserted their right, as property owners, to inoculate their slaves, others, equally vehemently, objected to the practice and asserted their right to protect their slaves from infection. Eighteenth-century colonial medicine was largely geared to keeping the bodies of slaves and workers productive and useful, but formal medicine never had a monopoly. Slaves on Ile de France brought with them a rich array of medical beliefs and practices from Africa, India, and Madagascar. We have little direct historical evidence for these, but we do know that many slaves came from areas in which forces of smallpox inoculation were known and practised. PMID:14535269

  8. Prograde Metamorphism recorded in Antarctic Granulite

    NASA Astrophysics Data System (ADS)

    Marschall, H.; Pauly, J.; Chatterjee, N.; Monteleone, B.; Meyer, H. P.

    2015-12-01

    High-grade metamorphic rocks provide an archive of tectonic processes and record conditions in the deep roots of orogenic belts. Granulites typically preserve chemical and mineralogical evidence of the peak temperature to which crustal rocks may be subjected, and they commonly preserve a multitude of textural and chemical features that allow a rather detailed reconstruction of their cooling and exhumation. More rarely, however, is it possible to reconstruct parts of the prograde path, which would allow a reconstruction of the loading and heating of the rocks. Access to the prograde P-T path and the rates and durations involved in granulite formation would provide important constraints on the convergence part of orogenic processes. Here we investigated a sample of felsic granulite from the H.U. Sverdrupfjella, which is part of the high-grade Maud Belt (East Antarctica). Peak-metamorphic conditions of approximately 925 °C and 1.45 GPa persisted for a maximum of circa 14 million years and were attained shortly after 570 Ma. In addition to the short-lived temperature peak, zircon preserved evidence for protracted granulite facies conditions with temperatures above 800 °C persisting for approximately 40 million years. Constraints on prograde metamorphism are recorded by garnet that preserved pre-peak metamorphic growth zones, by Ti zonation in zircon and by rutile inclusions in garnet. Zr-in-rutile thermometry using rutile included in different generations of garnet is used to reconstruct the prograde P-T path documenting burial followed by heating to ultra-high temperatures at peak pressures. Complementary, Ti zonation in prograde cores of zircon grains document and date heating, whereas younger zircon rims show again lower Ti-in-zircon temperatures and date the retrograde stages of metamorphism. The highest T is recorded in rutile, but not in zircon, consistent with the dissolution rather than growth of zircon at ultra-high temperatures. The clockwise loading

  9. Telemagmatic metamorphism superimposed on regional metamorphism: Evidence from coals in central China

    SciTech Connect

    Tang, Y. . Dept. of Geological Sciences)

    1993-02-01

    Coal (Lower Permian No. 1) in north-central Henan province, central China, exhibits a zoned rank distribution. The rank varies between high-volatile bituminous and anthracite. Highest rank coal occurs in a northwest-southeast trending zone that cuts across the center of the study area. Coal rank decreases from this central zone towards both the northeast and southwest. Core data indicate that the anthracite is currently overlain by over 4,600 m of sedimentary cover, which represents more or less continuous sedimentation during the Permian and Triassic. In the lower rank area to the southwest, erosion has removed all but approximately 1,000 m of strata. The rank distribution in this area has been attributed to regional metamorphism by previous workers as the higher coal rank coincides with the thicker strata. However, this study reveals that anthracite in the area has a much higher vitrinite reflectance, between 3--6% (Ro max, in oil), with some locations exhibiting reflectances greater than 6%. Petrographically, the anthracite is characterized by well developed pores (5--10 [mu]m in diameter) and mosaic structure. It is suggested that the higher heat flow is due to the presence of deep-seated plutons. It is proposed that coal metamorphism in this area involved three stages: (1) Pre-orogenic (early Permian-late Triassic). Regional metamorphism produced coals of subbituminous to high-volatile bituminous rank; (2) Orogenic (early Jurassic-late Cretaceous). Telemagmatic metamorphism resulted in zones of higher rank coal (medium volatile through anthracite rank); (3) Post-orogenic (Tertiary-Quaternary). Shallow burial depth due to the tectonic uplift followed by erosion had a negligible effect on coal rank. It is suggested, therefore, that coalification in this area is the result of regional metamorphism overprinted by telemagmatic metamorphism.

  10. Making MetPetDB a tool for reconnaissance studies of metamorphism and metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Hallett, B. W.; Spear, F. S.; Horkley, L. K.; Adali, S.; Fox, P. A.

    2012-12-01

    Recent data mining efforts have significantly increased the coverage and quantity of published data that form the foundation of MetPetDB: the Database for Metamorphic Petrology. Mineral assemblage, metamorphic grade, geochemical mineral and whole rock analyses, and image data from over 600 published papers have been compiled and uploaded, with focus on a number of particularly well-studied metamorphic belts of regional extent. As a result of data mining efforts in the past several years, MetPetDB now contains data for over 9,000 samples, over 10,000 mineral and whole rock (major or trace element) analyses, and over 20,000 images including maps, thin section scans, photomicrographs, SE and BSE images, and X-ray maps. These data are available for searching and download, exportable in spreadsheets and/or as placemark layers in a Google Earth .kml file. Each Google Earth placemark contains a link to the full data available through MetPetDB's web interface. The improved spatial coverage provides a starting point for a geoscientist to rapidly gather sample and geochemical data for a growing inventory of distinct metamorphic belts. Regional searches can be performed by choosing a user-defined bounding box, or any of a number of bounding polygons that delineate distinct metamorphic belts, such as the Greenland Caledonides, or the Bohemian Massif. MetPetDB is a tool for researchers to share, compile, and organize sample information, both published and unpublished, enabling production of a dynamic GIS to aid in planning field work, producing geologic maps, or making inventory of geochemical data for metamorphic rocks. In addition to regional queries, published metamorphic rock samples with non-spatial commonalities may be queried and compiled using MetPetDB. For example, a petrologist with an interest in the equilibrium exchange of yttrium between garnet and monazite at mid-crustal conditions could easily find garnet with a certain range of yttrium content in amphibolite

  11. Using quantitative phase petrology to understand metamorphism

    NASA Astrophysics Data System (ADS)

    White, Richard

    2015-04-01

    Quantitative phase petrology has become one of the mainstay methods for interpreting metamorphic rocks and processes. Its increased utility has been driven by improvements to end-member thermodynamics, activity-composition relationships and computer programs to undertake calculations. Such improvements now allow us to undertake calculations in increasingly complex chemical systems that more closely reflect those of rocks. Recent progress in activity-composition (a-x) relationships is aimed at developing suites of a-x relationships in large chemical systems that are calibrated together, which will allow a more direct application of the method to metamorphic rocks. In addition, considerable progress has been made in how quantitative phase diagrams can be used to understand features, including chemical potential diagrams for reaction textures, methods for fractionating bulk compositions and methods for modelling open system processes. One feature of calculated phase diagrams is that they present us with a great amount of information, such as mineral assemblages, mineral proportions, phase compositions, volume or density etc. An important aspect to using this information is to understand the potential uncertainties associated with these, which are significant. These uncertainties require that calculated phase diagrams be used with caution to interpret observed features in rocks. Features such as mineral zoning and reaction textures should still be interpreted in a semi-quantitative way, even if based on a fully quantitative diagram. Exercises such as the interpretation of reaction overstepping based on relating phase diagrams to observed mineral core compositions are likely to give spurious results given the infelicities in existing a-x models. Despite these limitations, quantitative phase petrology remains the most useful approach to interpreting the metamorphic history of rocks in that it provides a theoretical framework in which to interpret observed features rather

  12. Prograde and retrograde metamorphic processes in high-pressure subduction zone serpentinites from East Thessaly, Greece

    NASA Astrophysics Data System (ADS)

    Koutsovitis, Petros

    2016-04-01

    highly comparable with the P-T estimates from the East Thessaly metabasic rocks (˜350 ° C; P≈10-11 kbars)[5], suggesting that the entire metaophiolitic formation underwent blueschist facies metamorphism, comparable with high-pressure metaophiolitic formations appearing in Evia, Attica and the Cyclades. The East Thessaly serpentinites exhibit significantly high PM-normalized Pb, U enrichments and rather high Cs, La, As and Sb concentrations, which are comparable with subduction-related serpentinites, formed after mantle wedge peridotite hydration, and that have interacted with sedimentary derived fluids [2,6,7,8]. These serpentinites were also partly affected by de-serpentinization retrograde metamorphism (estimated at P<8 kbar and T<350 ° C) which is noticed by the following: secondary crosscuting antigorite veins occasionally with chlorite, coronas of chlorite along Cr-magnetite crystals, appearance of secondary calcite veins and talc. In the Kalochori-Chasanbali area, intense carbonization processes formed ophicalcite breccias enveloped by imbricated serpentinites[9], whereas talc-rich serpentinites appear in the region of Sklithro. Retrograde metamorphism may have occurred during exhumation, possibly within a serpentinite channel[8]. In addition, their retrograde history can also be indirectly identified through the study of their rodingite intrusions and more specifically through the formation of late-stage vesuvianite-rich dykes at low-moderate temperature conditions (T=250-300 oC) and subsequent derodingitization processes, forming metarodingites. The latter include abundant high-Mg replacive chlorite formed by continuous serpentinization which provided Mg2+ to the infiltrating fluids, causing the partial breakdown of Ca-bearing minerals. References. [1] Pe-Piper & Piper 2002: Borntraeger, Stuttgart, 1-645; [2] Lafay et al 2013: Chem Geol 343, 38-54; [3] Schwartz et al 2013: Lithos 178, 197-210; [4] Guillot, et al 2015: Tectonophysics 646, 1-19; [5] Perraki et

  13. Ostwald ripening of clays and metamorphic minerals

    USGS Publications Warehouse

    Eberl, D.D.; Srodon, J.; Kralik, M.; Taylor, B.E.; Peterman, Z.E.

    1990-01-01

    Analyses of particle size distributions indicate that clay minerals and other diagenetic and metamorphic minerals commonly undergo recrystallization by Ostwald ripening. The shapes of their particle size distributions can yield the rate law for this process. One consequence of Ostwald ripening is that a record of the recrystallization process is preserved in the various particle sizes. Therefore, one can determine the detailed geologic history of clays and other recrystallized minerals by separating, from a single sample, the various particle sizes for independent chemical, structural, and isotopic analyses.

  14. Metamorphic and stratigraphic constraints on the evolution of the Santa Catalina Mountains metamorphic core complex, Arizona

    SciTech Connect

    Palais, D.G.; Peacock, S.M. )

    1990-01-10

    Contact metamorphic mineral assemblages in the Santa Catalina Mountains metamorphic core complex constrain the emplacement depth of the metaluminous Late Cretaceous Leatherwood quartz diorite to between 7.5 and 14 km (2-3.8 kbar). The peraluminous Eocene Wilderness granite is constrained to have been emplaced at depths of less than 14 km. Stratigraphic and tectonic considerations are consistent with emplacement of both the Leatherwood quartz diorite and Wilderness granite at upper crustal levels. Published igneous thermobarometry (Anderson et al., 1988), although in approximate agreement with the metamorphic and tectonostratigraphic estimates for the depth of emplacement of the Wilderness granite, suggests that the Leatherwood quartz diorite was emplaced at depths of {approximately} 21 km (5.6 kbar) or greater. The discrepancy between the different emplacement estimates may reflect ambiguities associated with interpretations of the results from each technique. Igneous barometric assemblages may reflect conditions experienced during a period of crystallization during ascent of the magma through the crust (i.e., ponding of the magma). Alternatively, emplacement of the voluminous Wilderness granite and associated plutons may have entirely overprinted earlier Leatherwood-related contact metamorphism. The proposed upper crustal emplacement of the Leatherwood quartz diorite is consistent with the observation that Laramide-age crustal thickening in southeast Arizona probably did not exceed 8 km.

  15. Polycrystalline Diamonds from the Erzgebirge Ultrahigh-Pressure Metamorphic Terrane, Germany

    NASA Astrophysics Data System (ADS)

    Dobrzhinetskaya, L.; Wirth, R.; Green, H. W.

    2010-12-01

    other combinations of the mentioned elements. The dislocations array are also recognized withing polycrystals of the Erzgebirge diamond suggesting an internal stress occurred within the limited area of diamond nucleation and growth as inclusion within the refractory zircon crystal. Naturally occurring polycrystalline diamonds are rare and unusual. One of their populations, black diamonds, carbonado, are found only within placer deposits of Brazil and Central Africa. Models of their formation are extremely varied: from extraterrestrial to subduction related metamorphism or extreme nuclear radiation, or precipitation from carbonic fluid in the mantle, impact metamorphism of organic carbon and many others. The character of distribution of nanoscale fluid inclusions at the boundaries between individual crystals of the polycrystalline diamonds from Erzgebirge UHPM terrane is very similar to those described in carbonado diamonds (Kagi & Fukura, 2008). Further comparative studies of these features in diamonds from UHPM terranes and carbonado diamonds might cast light on the understanding diversity of mechanisms responsible for the polycrystalline diamonds formation.

  16. Metamorphism of the Chugach Metamorphic Complex, (Alaska). New pressure estimates question the ridge subduction context.

    NASA Astrophysics Data System (ADS)

    Bruand, Emilie; Gasser, Deta; Kurt, Stuewe; Beyssac, Olivier

    2010-05-01

    The Chugach Metamorphic Complex (CMC, Alaska) is a 200 km long and 10-50 km wide complex and is part of an active accretionary prism. According to the sparse existing literature, the complex is believed to be a low-pressure high-temperature terrain (400-650°C and ~3kb) with a migmatitic inner core (~5-10 km) and schist rims surrounded by phyllite (Sisson et al., 1988). Such low pressure conditions are not common in a subduction zone setting and the formation of the complex is thus attributed to the subduction of a ridge during the Eocene (~ 50 my). This contribution presents detailed petrological work from the region to show that the metamorphism occurred at much higher pressures than previously believed. We focus on the petrology of calcareous metapelites from 4 different N-S transects across the complex from west to east (each being 10 to 30 km wide). Several PT thermobarometric tools are used including average PT determination using THERMOCALC, garnet-biotite thermometry and RSCM (graphite) thermometers using Raman spectroscopy. In addition to these methods, several thermodynamic pseudosections were calculated. Our calculations show that the metamorphic conditions vary between 550°C and 3-4 kbar in the north of the complex to >700°C and 7-9 kbar in the south. In the central part of the complex these conditions appear to be attributable to a single metamorphic event that occurred around 50 my. However, in some locations near major granitic intrusions that penetrate the regions two events are observed: 1) a first one characterised by temperatures around 550°C followed by 2) a hotter contact metamorphism (>640°C). Earlier studies have interpreted the supposed low-pressure conditions of the CMC (considered to be no more than 3 kbar) to be connected to a ridge subduction geodynamic context. Within our interpretation, the hypothesis of a ridge subduction context is not needed and indeed appears questionable. In fact, a simple subduction context following by a

  17. Timing and heat sources for the Barrovian metamorphism, Scotland

    NASA Astrophysics Data System (ADS)

    Viete, Daniel R.; Oliver, Grahame J. H.; Fraser, Geoff L.; Forster, Marnie A.; Lister, Gordon S.

    2013-09-01

    New SHRIMP U/Pb zircon ages of 472.2 ± 5.8 Ma and 471.2 ± 5.9 Ma are presented for the age of peak metamorphism of Barrovian migmatites. 40Ar/39Ar ages for white mica from the Barrovian metamorphic series are presented, and are recalculated using recently-proposed revisions to the 40K decay constants to allow more precise and accurate comparison with U/Pb ages. The 40Ar/39Ar ages are found to vary systematically with increasing metamorphic grade, between c. 465 Ma for the biotite zone and c. 461 Ma for the sillimanite zone. There is no evidence for any significant metamorphic heating during the first 15 Myr of the Grampian Orogeny (before c. 473 Ma) or the final 4 Myr (after c. 465 Ma). The Barrovian metamorphism occurred over a period of ~ 8 Myr within the ~ 27-Myr Grampian Orogeny. The Barrovian metamorphism records punctuated heating, was temporally and spatially associated with large-scale bimodal magmatism, and developed within crust that was not overthickened. The temporally distinct nature of the Barrovian metamorphic episode within the Grampian Orogeny, and its heating pattern and tectonic context, are not consistent with significant heat contribution from thermal equilibration of overthickened crust. Rather, the Barrovian metamorphism records a transient phase of crustal thermal disequilibrium during the Grampian Orogeny. Temporal and spatial association with Grampian bimodal magmatism is consistent with production of the Barrovian metamorphic series within the middle crust as the result of advection of heat from the lower crust and/or mantle. The Barrovian metamorphic series - the classic example of ‘orogenic regional metamorphism’ - did not form in response to crustal thickening and thermal relaxation, but appears to record large-scale contact metamorphism.

  18. Synthesis, structural characterization and biological activity of two diastereomeric JA-Ile macrolactones.

    PubMed

    Jimenez-Aleman, Guillermo H; Machado, Ricardo A R; Görls, Helmar; Baldwin, Ian T; Boland, Wilhelm

    2015-06-01

    Jasmonates are phytohormones involved in a wide range of plant processes, including growth, development, senescence, and defense. Jasmonoyl-L-isoleucine (JA-Ile, 2), an amino acid conjugate of jasmonic acid (JA, 1), has been identified as a bioactive endogenous jasmonate. However, JA-Ile (2) analogues trigger different responses in the plant. ω-Hydroxylation of the pentenyl side chain leads to the inactive 12-OH-JA-Ile (3) acting as a “stop” signal. On the other hand, a lactone derivative of 12-OH-JA (5) (jasmine ketolactone, JKL) occurs in nature, although with no known biological function. Inspired by the chemical structure of JKL (6) and in order to further explore the potential biological activities of 12-modified JA-Ile derivatives, we synthesized two macrolactones (JA-Ile-lactones (4a) and (4b)) derived from 12-OH-JA-Ile (3). The biological activity of (4a) and (4b) was tested for their ability to elicit nicotine production, a well-known jasmonate dependent secondary metabolite. Both macrolactones showed strong biological activity, inducing nicotine accumulation to a similar extent as methyl jasmonate does in Nicotiana attenuata leaves. Surprisingly, the highest nicotine contents were found in plants treated with the JA-Ile-lactone (4b), which has (3S,7S) configuration at the cyclopentanone not known from natural jasmonates. Macrolactone (4a) is a valuable standard to explore for its occurrence in nature. PMID:25806705

  19. Metamorphism of eucrite meteorites studied quantitatively using induced thermoluminescence

    NASA Technical Reports Server (NTRS)

    Batchelor, J. David; Sears, Derek W. G.

    1991-01-01

    Induced thermoluminescence studies provide a new and quantitative means of determining relative metamorphic intensities for eucrite meteorites, the simplest and most ancient products of basaltic volcanism. Using this technique, it is shown that the eucrites constitute a continuous metamorphic series and not, as commonly assumed, two groups of metamorphosed and nonmetamorphosed meteorites. It is suggested that the method may have applications to other basalts.

  20. A Simulated Research Problem for Undergraduate Metamorphic Petrology.

    ERIC Educational Resources Information Center

    Amenta, Roddy V.

    1984-01-01

    Presents a laboratory problem in metamorphic petrology designed to simulate a research experience. The problem deals with data on scales ranging from a geologic map to hand specimens to thin sections. Student analysis includes identifying metamorphic index minerals, locating their isograds on the map, and determining the folding sequence. (BC)

  1. Pb and Zn release from crustal sediments during metamorphism

    NASA Astrophysics Data System (ADS)

    Hammerli, Johannes; Spandler, Carl; Oliver, Nick; Sossi, Paolo; Dipple, Greg

    2015-04-01

    Our understanding of the genesis of Pb-Zn ore systems is currently limited by a lack of knowledge about from where these metals are sourced. While it is generally agreed that the temperature and salinity of fluids play a crucial role in mobilizing metals, the importance of the composition of the source lithologies is poorly constrained. Furthermore, fluid-rock processes that lead to element mobility are yet to be fully understood, especially in metamorphic environments. To address these gaps in our knowledge we examine metal distribution and mobility in rocks from a prograde metamorphic sequence of the Mt Lofty Ranges, South Australia, where temperatures range from ~300 to 700˚C at ~3.5 to 5 kbar. This regional metamorphic belt underwent regional up-temperature fluid flow, which allowed for favourable conditions for enhanced element mobility. By studying the distribution and concentration of Pb and Zn on both bulk-rock and mineral scales, in combination with bulk rock Zn-isotope data, we can monitor the behaviour of these elements during pressure and temperature changes. Our results show that in staurolite-absent siliciclastic metasedimentary rocks, biotite contains >80% of the bulk rock Zn, as well as a considerable proportion of the total Pb, irrespective of the metamorphic grade. Pervasive fluid flow during metamorphism through these metasedimentary rocks led to a continuous depletion of Pb and Zn on a mineral and bulk-rock scale, resulting in a mobilization of ~80% of the bulk-rock Zn and ~50% of the bulk-rock Pb, mainly through reactions involving biotite. We calculated that a minimum of 2.7Mt of Pb and 27Mt of Zn was mobilized/lost in the high-grade metamorphic zone (200 km2). Halogen contents of apatite and biotite and bulk-rock Zn isotope data provide evidence that Cl-rich metamorphic fluids were important for metal transport. Hence, fluid flow accompanying metamorphism of typical sedimentary rocks can mobilize base metals to the degree required to form

  2. Fluid flow and chemical reaction kinetics in metamorphic systems

    SciTech Connect

    Lasaga, A.C.; Rye, D.M. )

    1993-05-01

    The treatment and effects of chemical reaction kinetics during metamorphism are developed along with the incorporation of fluid flow, diffusion, and thermal evolution. The interplay of fluid flow and surface reaction rates, the distinction between steady state and equilibrium, and the possible overstepping of metamorphic reactions are discussed using a simple analytic model. This model serves as an introduction to the second part of the paper, which develops a reaction model that solves the coupled temperature-fluid flow-chemical composition differential equations relevant to metamorphic processes. Consideration of stable isotopic evidence requires that such a kinetic model be considered for the chemical evolution of a metamorphic aureole. A general numerical scheme is discussed to handle the solution of the model. The results of this kinetic model allow us to reach several important conclusions regarding the factors controlling the chemical evolution of mineral assemblages during a metamorphic event. 41 refs., 19 figs., 5 tabs.

  3. Isothermal densification and metamorphism of new snow

    NASA Astrophysics Data System (ADS)

    Schleef, S.; Loewe, H.; Schneebeli, M.

    2012-12-01

    The interplay between overburden stress and surface energy induced growth and coarsening is relevant for the densification of snow and porous ice at all densities. The densification of new snow is amenable to high precision experiments on short time scales. To this end we investigate the coupling of densification and metamorphism of new snow via time-lapse tomography experiments in the laboratory. We compare the evolution of density, strain, and specific surface area to previous long-time metamorphism experiments of snow and creep of polycrystalline ice. Experimental conditions are tailored to the requirements of time-lapse tomography and the measurements are conducted under nearly isothermal conditions at -20°C with a duration of two days. Images were taken with temporal resolution of a few hours which reveal precise details of the microstructure evolution due to sintering and compaction. We used different crystal shapes of natural new snow and snow samples obtained by sieving crystals grown in a snowmaker in the laboratory. To simulate the effect of overburden stress due to an overlying snowpack additional weights were applied to the sample. As expected we find an influence of the densification rate on initial density and overburden stress. We calculated strain rates and identified a transient creep behavior with a similar power law for all crystal types which substantially differs from the Andrade creep of polycrystalline ice. As a main result we found that the evolution of the specific surface area is independent of the density and follows a unique decay form for all measurements of each crystal type. The accuracy of the measurements allows to obtain a decay exponent for the SSA which is the same as previously obtained from the long-time regime during isothermal metamorphism after several months. Our preliminary results for all available types of new snow suggest a correlation between the initial density and SSA. We also find snow samples which coincide in

  4. Post-metamorphic brecciation in type 3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Mccoy, T. J.; Keil, K.

    1993-01-01

    Type 3.1-3.9 ordinary chondrites can be divided into two kinds: those in which the compositions of chondrule silicates are entirely consistent with metamorphism of type 3.0 material, and those in which the computational heterogeneity appears to be too extreme for in situ metamorphism. We present petrologic data for three LL3 chondrites of the second kind--Ngawi, ALH A77278 (both type 3.6), and Hamlet (type 3.9)--and compare these data with results for the first kind of LL3-4 chondrites. Given that chondrules form in the nebula and that metamorphic equilibration occurs in asteroids, our new data imply that Ngawi, A77278, Hamlet, and many other type 3 ordinary chondrites are post-metamorphic breccias containing materials with diverse metamorphic histories; they are not metamorphic rocks or special kinds of 'primitive breccias.' We infer also that metamorphism to type 3.1-3.9 levels produces very friable material that is easily remixed into breccias and lithified by mild shock. Thus, petrologic types and subtypes of chondrites indicate the mean metamorphic history of the ingredients, not the thermal history of the rock. The metamorphic history of individual type 1 or 2 porphyritic chondrules in type 3 breccias is best derived from olivine and pyroxene analyses and the data of McCoy et al. for unbrecciated chondrites. The new chondrule classification schemes of Sears, DeHart et al., appears to provide less information about the original state and metamorphic history of individual porphyritic chondrules and should not replace existing classification schemes.

  5. Post-metamorphic brecciation in type 3 ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Scott, E. R. D.; McCoy, T. J.; Keil, K.

    1993-03-01

    Type 3.1-3.9 ordinary chondrites can be divided into two kinds: those in which the compositions of chondrule silicates are entirely consistent with metamorphism of type 3.0 material, and those in which the computational heterogeneity appears to be too extreme for in situ metamorphism. We present petrologic data for three LL3 chondrites of the second kind--Ngawi, ALH A77278 (both type 3.6), and Hamlet (type 3.9)--and compare these data with results for the first kind of LL3-4 chondrites. Given that chondrules form in the nebula and that metamorphic equilibration occurs in asteroids, our new data imply that Ngawi, A77278, Hamlet, and many other type 3 ordinary chondrites are post-metamorphic breccias containing materials with diverse metamorphic histories; they are not metamorphic rocks or special kinds of 'primitive breccias.' We infer also that metamorphism to type 3.1-3.9 levels produces very friable material that is easily remixed into breccias and lithified by mild shock. Thus, petrologic types and subtypes of chondrites indicate the mean metamorphic history of the ingredients, not the thermal history of the rock. The metamorphic history of individual type 1 or 2 porphyritic chondrules in type 3 breccias is best derived from olivine and pyroxene analyses and the data of McCoy et al. for unbrecciated chondrites. The new chondrule classification schemes of Sears, DeHart et al., appears to provide less information about the original state and metamorphic history of individual porphyritic chondrules and should not replace existing classification schemes.

  6. Metamorphic zoning and geodynamic evolution of an inverted crustal section (Karakorum margin, N Pakistan), evidence for two metamorphic events

    NASA Astrophysics Data System (ADS)

    Rolland, Y.; Carrio-Schaffhauser, E.; Sheppard, S. M. F.; Pêcher, A.; Esclauze, L.

    2006-04-01

    The Karakorum Range comprises a crustal section of marbles and metapelites providing an opportunity to study the extent of high-temperature metamorphic reequilibration in an active orogen. Metamorphism culminated during the Mio-Pliocene, at 6 7 Ma. Peak metamorphic conditions increased from south to north, i.e. from (1) the Upper Anchizone grade (lawsonite, chlorite smectite) to (2) lower granulite migmatite grade (HT˜800°C) conditions along strike of a 30-km section perpendicular to the structural fabric of the rocks. The metamorphic section can be separated into two domains: 1. A domain with low to transitional metamorphic conditions, with respect to the HT zone, where initial bedding is preserved. These moderate PT conditions prevailed during the main tectonic stacking event (50 37 Ma), prior to the Mio-Pliocene event. In this domain, metamorphism is governed by fluid-assisted grain-scale diffusion, as suggested by the progressive coarsening of minerals with increasing metamorphic grade and the preservation of sedimentary δ13C signatures in carbonates. A low thermal gradient (17°C/km) is derived from P-T estimates of the prograde metamorphic sequences.

  7. Redistribution of volatiles during lunar metamorphism

    NASA Technical Reports Server (NTRS)

    Cirlin, E. H.; Housley, R. M.

    1980-01-01

    Thermal release profiles of Pb, Zn, and Cd in sample 66095 (highly shocked breccia with melt rock matrix) showed that these volatiles were mostly present on the surface of the grains. Zn in rusty grains from 66095 was also mostly surface Zn, probably from sphalerite in grain boundaries and cracks. Simulation experiments of volatile transfer showed that Fe, FeCl2, iron phosphide, and troilite (FeS) can be produced and transported during subsolidus reactions. These results suggest that volatiles, rust, schreibersite, and possible siderophiles which are observed in lunar highland samples might have been redistributed during disequilibrium thermal metamorphism in hot ejecta blankets, and were not necessarily introduced by volcanic activity or meteoritic addition.

  8. Shock metamorphism of lunar and terrestrial basalts

    NASA Technical Reports Server (NTRS)

    Schaal, R. B.; Hoerz, F.

    1977-01-01

    Lonar Crater (India) basalt and lunar basalt 75035 were shock loaded under controlled laboratory conditions up to 1000 kbar, generally in a CO/CO2 (1:1) environment evacuated to 10 to the minus seventh power torr. The Kieffer et al. (1976) classification scheme of progressive shock metamorphism is found to apply to lunar basalts. The major shock features of the five classes that span the range 0 to 1000 kbar are described. Only three out of 152 basalt specimens show shock effects in their natural state as severe as Class 2 features. The scarcity of shocked basalt hand samples in contrast to the abundance of shock-produced agglutinates and homogeneous glass spheres in the lunar regolith indicates the dominant role of micrometeorite impact in the evolution of the lunar regolith. The overall glass content in asteroidal and Mercurian regoliths is considered.

  9. Shock metamorphic effects in lunar microcraters

    NASA Technical Reports Server (NTRS)

    Schaal, R. B.; Hoerz, F.; Gibbons, R. V.

    1976-01-01

    Detailed petrographic descriptions and results of electron microprobe analyses are presented for impact glasses as well as shocked and unshocked minerals associated with individual lunar microcraters (diameters of 0.4 to 4.4 mm). Rocks of four typical lunar lithologies are studied: anorthosite, anorthositic norite, ophitic basalt, and polymict breccia. Textures, mineralogies, and chemical compositions are examined along a radial traverse through each microcrater; i.e., across the impact glasses lining the crater wall, the shock-metamorphosed zone immediately underlying the glass liner, and the unshocked host rock. The microcraters are discussed in a sequence of increasing mineralogical complexity of the host rock (from anorthosite to polymict breccia) in order to distinguish shock effects among mineral types. The shock metamorphic features observed are found to be comparable to those reported in shocked basalt from Lonar Crater, India, and are categorized into five shock-intensity classes with pressures experimentally calibrated.

  10. Early planetary metamorphism in chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Hanan, B. B.; Tilton, G. R.

    1985-07-01

    The record of early events in the solar system is presently sought, together with information on the isotopic composition of primordial lead, in the lead isotope relations of whole rock and separated phases of Mezo-Madaras (L3) and Sharps (H3) chondrites; the respective ages of 4.48 and 4.47 billion years are not significantly changed when Canyon Diablo troilite lead is included in the data sets, suggesting that the initial Pb isotopic composition in both meteorites was the same as that in the troilite. The 4.48 billion year age, which is younger than the well established 4.54-4.56 billion years of the Allende chondrite and Angra dos Reis achondrite, appears to date an early metamorphic event rather than the formation of the chondrites.

  11. Metamorphic Perspectives of Subduction Zone Volatiles Cycling

    NASA Astrophysics Data System (ADS)

    Bebout, G. E.

    2008-12-01

    Field study of HP/UHP metamorphic rocks provides "ground-truthing" for experimental and theoretical petrologic studies estimating extents of deep volatiles subduction, and provides information regarding devolatilization and deep subduction-zone fluid flow that can be used to reconcile estimates of subduction inputs and arc volcanic outputs for volatiles such as H2O, N, and C. Considerable attention has been paid to H2O subduction in various bulk compositions, and, based on calculated phase assemblages, it is thought that a large fraction of the initially structurally bound H2O is subducted to, and beyond, subarc regions in most modern subduction zones (Hacker, 2008, G-cubed). Field studies of HP/UHP mafic and sedimentary rocks demonstrate the impressive retention of volatiles (and fluid-mobile elements) to depths approaching those beneath arcs. At the slab-mantle interface, high-variance lithologies containing hydrous phases such as mica, amphibole, talc, and chlorite could further stabilize H2O to great depth. Trench hydration in sub-crustal parts of oceanic lithosphere could profoundly increase subduction inputs of particularly H2O, and massive flux of H2O-rich fluids from these regions into the slab-mantle interface could lead to extensive metasomatism. Consideration of sedimentary N concentrations and δ15N at ODP Site 1039 (Li and Bebout, 2005, JGR), together with estimates of the N concentration of subducting altered oceanic crust (AOC), indicates that ~42% of the N subducting beneath Nicaragua is returned in the corresponding volcanic arc (Elkins et al., 2006, GCA). Study of N in HP/UHP sedimentary and basaltic rocks indicates that much of the N initially subducted in these lithologies would be retained to depths approaching 100 km and thus available for addition to arcs. The more altered upper part of subducting oceanic crust most likely to contribute to arcs has sediment-like δ15NAir (0 to +10 per mil; Li et al., 2007, GCA), and study of HP/UHP eclogites

  12. Conodont color and textural alteration: an index to regional metamorphism, contact metamorphism, and hydrothermal alteration.

    USGS Publications Warehouse

    Rejebian, V.A.; Harris, A.G.; Huebner, J.S.

    1987-01-01

    Experimental and field data are used to extend the utility of conodonts as semi-quantitative thermal indices into the regimes of regional and contact metamorphism, as well as hydrothermal alteration. These experiments approximate the type of Colour Alteration Indices mixture characteristically found in conodonts recovered from hydrothermally altered rocks. These data indicate that CAI values of 6 to 8 cannot be used to assess precise temperatures of hydrothermally altered rocks but may serve as useful indicators of potential mineralization. - from Authors

  13. Craniocervical necrotizing fasciitis in Ile-Ife, Nigeria.

    PubMed

    Ndukwe, K C; Fatusi, O A; Ugboko, V I

    2002-02-01

    Sixteen cases of necrotizing fasciitis were seen at the Obafemi Awolowo University Teaching Hospital, Ile-Ife, Nigeria from 1990 to 2000. Primary craniocervical involvement was recorded in seven patients (five men and two women). The clinical records of five patients were sufficiently detailed to allow us to report their age, aetiology, predisposing illness, clinical features, complications, management regimen and outcome. The patients were aged 30-75 years and in four of them odontogenic infections were the cause of the condition. Hypertension, diabetes mellitus and obesity were the underlying systemic diseases in three cases and the body/angle region of the mandible was the predominant site of the infection on the face. All five cases had involvement of the neck. Mediastinal extension was recorded in three cases. Two patients had complications: one had septicaemia and renal failure and the other developed bone necrosis. Pre-existing ill health, old age, late surgical intervention, and mediastinal and thoracic extension of infection were responsible for the only death. Treatment involved frequent and multiple surgical debridement, aggressive antimicrobial treatment and control of systemic disease. Early recognition, prompt surgical intervention, and aggressive antimicrobial treatment are essential to minimize morbidity and mortality. Rapid progression of infection, financial constraints, delayed referrals from rural clinics and distance to the tertiary hospital caused problems. PMID:11883974

  14. Garnet as a reactant during and recorder of mid-crustal metamorphism: Sawtooth Metamorphic Complex, Idaho

    NASA Astrophysics Data System (ADS)

    Dutrow, B. L.; Henry, D.; Fukai, I.; Metz, K.

    2013-12-01

    The Sawtooth Metamorphic Complex (SMC), in central Idaho, is a newly recognized high-grade metamorphic terrain that provides constraints on crustal evolution of a key area in North America. The SMC lies near the southwestern margin of Laurentia, in an area that is largely obscured by the voluminous Idaho Batholith. Originally mapped as undifferentiated Precambrian metamorphic rocks, recent work demonstrates that a range of rock types from aluminous gneisses to calc-silicates record middle-lower crustal conditions. Field mapping, high-resolution sampling, mineral chemical, whole-rock and trace-element characterization define the nature of metamorphism. Multi-equilibria thermobarometry of aluminous gneisses yield the highest pressure (P)-temperature (T) conditions of lower-granulite facies near 765-795 °C and 7 kbar. Peraluminous gneisses passed above the muscovite stability field to produce sillimanite (sil) + Ksp + H2O. Occasionally, fine-grained biotite + sil are included in the cordierite (crd) suggesting the reaction: phlogopite + sil = Mg-crd + garnet + H2O. These dehydration reactions likely enhanced localized melting and migmatite formation. A post peak hydration event produced muscovite and andalusite that cross cuts dominant foliation and indicates a clockwise P-T path. In these rocks, garnet serves as an important phase to react with and to preserve the peak and post-peak phases and conditions. Calc-silicate gneisses record at least two metamorphic (M1, M2) and two deformational (D1, D2) events. M1 reaches upper-amphibolite to lower-granulite facies at temperatures near 800oC at 6 kbar. D1 ductile deformation post-dates peak metamorphism and produces deformation lamellae in clinopyroxene. M2 is characterized by amphibole (magnesiohornblende and tremolite) growth overprinting and retrogressing peak assemblages at Ts from 620-740oC at an assumed P of 6.5 kbar based on the application of the hornblende-plagioclase thermometer. These temperatures are

  15. The role of Ile87 of CYP158A2 in oxidative coupling reaction

    SciTech Connect

    Zhao, Bin; Bellamine, Aouatef; Lei, Li; Waterman, Michael R.

    2012-05-15

    Both CYP158A1 and CYP158A2 are able to catalyze an oxidative C-C coupling reaction producing biflaviolin or triflaviolin in Streptomyces coelicolor A3(2). The substrate-bound crystal structures of CYP158A2 and CYP158A1 reveal that the side chain of Ile87 in CYP158A2 points to the active site contacting the distal flaviolin molecule, however, the bulkier side chain of Lys90 in CYP158A1 (corresponding to Ile87 in CYP158A2) is toward the distal surface of the protein. These results suggest that these residues could be important in determining product regiospecificity. In order to explore the role of the two residues in catalysis, the reciprocal mutants, Ile87Lys and Lys90Ile, of CYP158A2 and CYP158A1, respectively, were generated and characterized. The mutant Ile87Lys enzyme forms two isomers of biflaviolin instead of three isomers of biflaviolin in wild-type CYP158A2. CYP158A1 containing the substitution of lysine with isoleucine has the same catalytic activity compared with the wild-type CYP158A1. The crystal structure of Ile87Lys showed that the BC loop in the mutant is in a very different orientation compared with the BC loop in both CYP158A1/A2 structures. These results shed light on the mechanism of the oxidative coupling reaction catalyzed by cytochrome P450.

  16. A previously undescribed jasmonate compound in flowering Arabidopsis thaliana - The identification of cis-(+)-OPDA-Ile.

    PubMed

    Floková, Kristýna; Feussner, Kirstin; Herrfurth, Cornelia; Miersch, Otto; Mik, Václav; Tarkowská, Danuše; Strnad, Miroslav; Feussner, Ivo; Wasternack, Claus; Novák, Ondřej

    2016-02-01

    Jasmonates (JAs) are plant hormones that integrate external stress stimuli with physiological responses. (+)-7-iso-JA-L-Ile is the natural JA ligand of COI1, a component of a known JA receptor. The upstream JA biosynthetic precursor cis-(+)-12-oxo-phytodienoic acid (cis-(+)-OPDA) has been reported to act independently of COI1 as an essential signal in several stress-induced and developmental processes. Wound-induced increases in the endogenous levels of JA/JA-Ile are accompanied by two to tenfold increases in the concentration of OPDA, but its means of perception and metabolism are unknown. To screen for putative OPDA metabolites, vegetative tissues of flowering Arabidopsis thaliana were extracted with 25% aqueous methanol (v/v), purified by single-step reversed-phase polymer-based solid-phase extraction, and analyzed by high throughput mass spectrometry. This enabled the detection and quantitation of a low abundant OPDA analog of the biologically active (+)-7-iso-JA-L-Ile in plant tissue samples. Levels of the newly identified compound and the related phytohormones JA, JA-Ile and cis-(+)-OPDA were monitored in wounded leaves of flowering Arabidopsis lines (Col-0 and Ws) and compared to the levels observed in Arabidopsis mutants deficient in the biosynthesis of JA (dde2-2, opr3) and JA-Ile (jar1). The observed cis-(+)-OPDA-Ile levels varied widely, raising questions concerning its role in Arabidopsis stress responses. PMID:26675361

  17. The Role of Ile87 of CYP158A2 in Oxidative Coupling Reaction

    PubMed Central

    Zhao, Bin; Bellamine, Aouatef; Lei, Li; Waterman, Michael R.

    2012-01-01

    Both CYP158A1 and CYP158A2 are able to catalyze an oxidative C-C coupling reaction producing biflaviolin or triflaviolin in Streptomyces coelicolor A3(2). The substrate-bound crystal structures of CYP158A2 and CYP158A1 reveal that the side chain of Ile87 in CYP158A2 points to the active site contacting the distal flaviolin molecule, however, the bulkier side chain of Lys90 in CYP158A1 (corresponding to Ile87 in CYP158A2) is toward the distal surface of the protein. These results suggest that these residues could be important in determining product regiospecificity. In order to explore the role of the two residues in catalysis, the reciprocal mutants, Ile87Lys and Lys90Ile, of CYP158A2 and CYP158A1, respectively, were generated and characterized. The mutant Ile87Lys enzyme forms two isomers of biflaviolin instead of three isomers of biflaviolin in wild-type CYP158A2. CYP158A1 containing the substitution of lysine with isoleucine has the same catalytic activity compared with the wild-type CYP158A1. The crystal structure of Ile87Lys showed that the BC loop in the mutant is in a very different orientation compared with the BC loop in both CYP158A1/A2 structures. These results shed light on the mechanism of the oxidative coupling reaction catalyzed by cytochrome P450. PMID:22203090

  18. Thrust involvement of metamorphic rocks, southwestern Brooks Range, Alaska

    SciTech Connect

    Till, A.B.; Schmidt, J.M.; Nelson, S.W. )

    1988-10-01

    Most models for the tectonic history of the western Brooks Range treat Proterozoic and lower Paleozoic metamorphic rocks exposed in the southern part of the range as passive structural basement vertically uplifted late in the Mesozoic orogenic episode. Mapping in the metamorphic rocks shows that they can de divided into two structurally and metamorphically distinct belts, both of which were folded and thrust during the orogeny. Recognition of these belts and the nature of the contact separating them is critical to construction of accurate tectonic models of the Brooks Range fold and thrust belt.

  19. Early Proterozoic ultrahigh pressure metamorphism: evidence from microdiamonds.

    PubMed

    Cartigny, Pierre; Chinn, Ingrid; Viljoen, K S; Robinson, Derek

    2004-05-01

    Microdiamonds from the Akluilâk minette dykes (Nunavut, Canada) are similar to diamonds formed in subducted metamorphic rocks. High concentrations of unaggregated nitrogen and positive delta(15)N suggest that the microdiamonds formed within rocks subducted to ultrahigh pressures before being sampled by the minette magma 1.8 billion years ago. This ultrahigh pressure metamorphism in North America, probably related to the Trans-Hudson orogen (about 2 billion years ago), extends the occurrence of ultrahigh pressure metamorphism from 0.6 billion years to before 1.8 billion years ago and suggests that Phanerozoic-type subductions were active by the Early Proterozoic. PMID:15131301

  20. Metamorphic probing of subduction dynamics and rheology

    NASA Astrophysics Data System (ADS)

    Agard, Philippe

    2015-04-01

    Understanding subduction dynamics and rheology, and particularly the role of fluids and deformation, strongly relies on integrated tectonic, petrological and geochemical studies able to retrieve from our most direct and reliable natural probes (i.e., preserved metamorphic assemblages) their pressure-temperature-time (P-T-t) evolution. I first provide two examples of such integrated studies that allow tracking rock trajectories and exhumation dynamics in subduction zones -- thanks to the considerable progress made over the last ten years on estimating P-T-t conditions. The Oman example shows how EPMA mapping and the detailed study of local, low-temperature equilibria help constrain the behaviour and dynamics of upper crustal units during continental subduction, demonstrating the importance of slicing, accretion at depths of ~30 km and short-lived tectonic expulsion. In the Western Alps, the extensive coverage of field exposures by means of the Raman Spectrometry of carbonaceous matter and by dedicated pseudosection modelling allows to identify the existence of tens of km long, fairly continuous slices of downgoing slab exhumed from similar eclogitic depths (~80 km), and to assess the role of the overall fluid content in enabling their exhumation/preservation. I then illustrate how metamorphic rocks can provide ideal probes (though still partly to be improved) to address key, large-scale tectonic processes and not 'simply' histories, and do stress the importance of adequate field-based data acquisition. Three examples (and present-day limitations) are reviewed here: (1) The regional-scale exhumation of blueschists from the downdip end of the seismogenic zone across thousands of kilometers along the Neotethys (at ~1-1.5 GPa, 350°C) is a major geodynamic event providing insights into changes in interplate mechanical coupling and subduction dynamics. (2) Eclogite breccias recently reported in the Monviso area (W. Alps) allow constraining short-term processes involving

  1. Metamorphic and geochemical evolution of an amphibolite layer in the Chugach Metamorphic Complex (Alaska)

    NASA Astrophysics Data System (ADS)

    Bruand, E.; Gasser, D.; Stuewe, K.

    2010-12-01

    The Chugach Metamorphic Complex (CMC) is an Eocene high temperature- low to medium pressure complex located in an accretionary prism (Southern Alaska). This complex is more than 300 km long, made up of metasediments associated with an amphibolite layer (~ 10m to several km width) in its southern part. Based on the study of some part of this amphibolite layer, Lull and Plafker (1990) suggested that its geometry was due to the subduction of an intraplate island arc parallel to the Alaskan margin. However following their data, the assumption was highly hypothetic. West of our study area (>150km), another “metabasalt layer” composed by pillow basalts, gabbros and sheeted dikes is described in a southern accreted terrane (Prince William terrane). Some workers suggested a possible link between the origin of these ophiolites and the metabasalt layer extended from Valdez to south of Yakutat (our study area). They argued that these metabasalts or at least the western part (Valdez location) could reflect melt emplaced into the accretionary prism and generated upward to an asthenospheric window link with the subduction of a ridge. Thus the presence of this amphibolite layer in southern Alaska is matter of debate. Therefore, in this contribution, we detailed a petrologic and geochemical study of the amphibolite layer to reconstruct the metamorphic history of this strip using thermobarometry and pseudosection modelling (THERMOCALC). Petrological observations reveal a metamorphic peak assemblage composed by hb-pl±qtz-ilm/hem/mag and PT estimates about 650-750°C and 6-8 kb. Retrograde feature are symbolised by epidote, actinolite, chlorite, albite and sphene and seem to crystallise at temperature below 450°C. The amphibolite show REE and trace elements patterns characteristic for an altered metabasalt (U and Ba positive anomalies) as well as local contaminations by sediments (Pb and Sr positive anomalies). Pressure-temperature results are compared to a recent study on the

  2. Acadian metamorphism associated with the Lexington batholith, Bingham, Maine

    USGS Publications Warehouse

    Dickerson, R.P.; Holdaway, M.J.

    1989-01-01

    The Lexington batholith in western Maine intruded upper crustal rocks in three pulses, now exposed as the north, central, and south lobes. A study of the metamorphosed pelitic rocks surrounding the batholith has shown that this terrane was subjected to three metamorphic subevents of the major event, M2 over a short time interval at about 400 Ma. Following M1, a low-grade event, cordierite, andalusite, and sillimanite + K-feldspar were produced by the contact metamorphic subevent (M2n) associated with the north lobe. Then a metamorphic subevent of more regional extent (M2) produced garnet, staurolite, and andalusite in the southern half of the study area. Isograd patterns suggest that this subevent was largely concentric with, and broadly related to, the central and south lobes of the batholith. Staurolite, andalusite, and sillimanite were produced by slightly later contact metamorphic subevent (M2s) produced by the central and south lobes. -from Authors

  3. Mineral-water reactions in metamorphism and volcanism

    USGS Publications Warehouse

    Barnes, I.

    1985-01-01

    Low-temperature (120??C and less) metamorphism of graywacke, granite and andesite yields zeolites and precursor gels by reaction with fresh water but low-greenschist facies by reaction with salt (sea)water. ?? 1985.

  4. Inverted Metamorphic Multijunction (IMM) Cell Processing Instructions

    SciTech Connect

    Duda, A.; Ward, S.; Young, M.

    2012-02-01

    This technical report details the processing schedule used to fabricate Inverted Metamorphic Multijunction (IMM) concentrator solar cells at The National Renewable Energy Laboratory (NREL). These devices are used as experimental test structures to support the research at NREL that is focused on increasing the efficiency of photovoltaic power conversion. They are not intended to be devices suitable for deployment in working concentrator systems primarily because of heat sinking issues. The process schedule was developed to be compatible with small sample sizes and to afford relatively rapid turn-around times, in support of research efforts. The report describes the use of electro deposition of gold for both the back and front contacts. Electro-deposition is used because of its rapid turn around time and because it is a benign metallization technique that is seldom responsible for damage to the semiconductors. The layer transfer technique is detailed including the use of a commercially available adhesive and the etching away of the parent gallium arsenide substrate. Photolithography is used to define front contact grids as well as the mesa area of the cell. Finally, the selective wet chemical etchant system is introduced and its use to reveal the back contact is described.

  5. Thermal history of a metamorphic core complex

    NASA Technical Reports Server (NTRS)

    Dokka, R. K.; Mahaffie, M. J.; Snoke, A. W.

    1985-01-01

    Fission track (FT) thermochronology studies of lower plate rocks of the Ruby Mountains-East Humbolt Range metamorphic core complex provide important constraints on the timing an nature of major middle Tertiary extension of northeast Nevada. Rocks analyzed include several varieties of mylonitic orthogneiss as well as amphibolitic orthognesses from the non-mylonitic infrastructural core. Oligocene-age porphyritic biotite granodiorite of the Harrison Pass pluton was also studied. The minerals dated include apatite, zircon, and sphene and were obtained from the same rocks that have been previously studied. FT ages are concordant and range in age from 26.4 Ma to 23.8 Ma, with all showing overlap at 1 sigma between 25.4 to 23.4 Ma. Concordancy of all FT ages from all structural levels indicates that the lower plate cooled rapidly from temperatures above approx. 285 C (assumed sphene closure temperature (2)) to below approx. 150 C (assumed apatite closure temperature) near the beginning of the Miocene. This suggests that the lower plate cooled at a rate of at least approx. 36 deg C/Ma during this event. Rapid cooling of the region is considered to reflect large-scale tectonic denudation (intracrustal thinning), the vertical complement to intense crustal extension. FT data firmly establish the upper limit on the timing of mylonitization during detachment faulting and also coincide with the age of extensive landscape disruption.

  6. Iles Eparses (SW Indian Ocean) as reference ecosystems for environmental research

    NASA Astrophysics Data System (ADS)

    Quétel, C.; Marinesque, S.; Ringler, D.; Fillinger, L.; Changeux, T.; Marteau, C.; Troussellier, M.

    2016-04-01

    TAAF ensures since 2007 the management of 5 small tropical islands lying in the southwestern Indian Ocean: the Iles Eparses. These islands share an exceptional natural heritage including many marine and terrestrial endemic species. At a regional scale the Iles Eparses are some of the most pristine ecosystems, largely preserved from anthropogenic impacts due to their geographical isolation and a historically very limited human occupation. In this context, TAAF wished that Iles Eparses become unique natural laboratories for earth scientists and environmental process observation - like climate change impacts - but also sustainable biodiversity sanctuaries for which the scientific community should provide baseline ecological data to inform on appropriate conservation tools. An inter-agency research consortium emerged in 2009 to meet this commitment for the Iles Eparses. This program was intended to set a science framework in accordance with France' objectives for Research and Conservation. It enabled between 2009 and 2014 the implementation of 18 cross-disciplinary research projects ranging from geology to ecology and represented by the variety of the proposed articles in this special issue. Altogether research projects have dramatically increased knowledge on the Iles Eparses' ecosystems and have provided the first overview of their diversity, their functions and their dynamics and its determinants. In particular applied research efforts have supplied a significant amount of ecological evidence that is now available to develop optimal conservation strategy to ensure the Iles Eparses' long-term biodiversity value. These findings point out that the continuation of research activity in the Iles Eparses should be considered a priority.

  7. Archean metamorphic sequence and surfaces, Kangerdlugssuaq Fjord, East Greenland

    NASA Technical Reports Server (NTRS)

    Kays, M. A.

    1986-01-01

    The characteristics of Archean metamorphic surfaces and fabrics of a mapped sequence of rocks older than about 3000 Ma provide information basic to an understanding of the structural evolution and metamorphic history in Kangerdlugssuaq Fjord, east Greenland. This information and the additional results of petrologic and geochemical studies have culminated in an extended chronology of Archean plutonic, metamorphic, and tectonic events. The basis for the chronology is considered, especially the nature of the metamorphic fabrics and surfaces in the Archean sequence. The surfaces, which are planar mineral parageneses, may prove to be mappable outside Kangerdlugssuaq Fjord, and if so, will be helpful in extending the events that they represent to other Archean sequences in east Greenland. The surfaces will become especially important reference planes if the absolute ages of their metamorphic assemblages can be determined in at least one location where strain was low subsequent to their recrystallization. Once an isochron is obtained, the dynamothermal age of the regionally identifiable metamorphic surface is determined everywhere it can be mapped.

  8. Earthquakes, fluid pressures and rapid subduction zone metamorphism

    NASA Astrophysics Data System (ADS)

    Viete, D. R.

    2013-12-01

    High-pressure/low-temperature (HP/LT) metamorphism is commonly incomplete, meaning that large tracts of rock can remain metastable at blueschist- and eclogite-facies conditions for timescales up to millions of years [1]. When HP/LT metamorphism does take place, it can occur over extremely short durations (<<1 Myr) [1-2]. HP/LT metamorphism must be associated with processes that allow large volumes of rock to remain unaffected over long periods of time, but then suddenly undergo localized metamorphism. Existing models for HP/LT metamorphism have focussed on the role of fluids in providing heat for metamorphism [2] or catalyzing metamorphic reactions [1]. Earthquakes in subduction zone settings can occur to depths of 100s of km. Metamorphic dehydration and the associated development of elevated pore pressures in HP/LT metamorphic rocks has been identified as a cause of earthquake activity at such great depths [3-4]. The process of fracturing/faulting significantly increases rock permeability, causing channelized fluid flow and dissipation of pore pressures [3-4]. Thus, deep subduction zone earthquakes are thought to reflect an evolution in fluid pressure, involving: (1) an initial increase in pore pressure by heating-related dehydration of subduction zone rocks, and (2) rapid relief of pore pressures by faulting and channelized flow. Models for earthquakes at depth in subduction zones have focussed on the in situ effects of dehydration and then sudden escape of fluids from the rock mass following fracturing [3-4]. On the other hand, existing models for rapid and incomplete metamorphism in subduction zones have focussed only on the effects of heating and/or hydration with the arrival of external fluids [1-2]. Significant changes in pressure over very short timescales should result in rapid mineral growth and/or disequilibrium texture development in response to overstepping of mineral reaction boundaries. The repeated process of dehydration-pore pressure development

  9. Ultrahigh Pressure Metamorphism (UHPM): Quo Vadimus?

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2007-12-01

    UHPM is the petrologic record (min. P-T equivalent to Coe stability) of transport of continental lithosphere to asthenospheric depth, and return to crustal depth and incorporation into continents. The record of UHPM is scale- independent, but the issue of unit size (boudin/slice/terrane) and whether UHPM is recorded are important. Although the requirement for external hydration may limit equilibration in protoliths, cofacial compatible, indicative and diagnostic assemblages and lack of confidence in thermobarometry obfuscate the record of UHPM. Polymetamorphism and/or overprinting by multiple UHPM events may be possible through successive Wilson cycles and may be cryptic to add complexity. Our ability to image and study inclusion assemblages in zircons has been a major breakthrough, but are diamonds anybody's best friend? Is the max. depth from which continental crust may be retrieved equivalent to P = 10GPa or >10GPa? Will evidence remain to infer such depth? Commonly we tie dates to P-T, which yields rates that constrain mechanisms; advances in numerical modeling will enable progress in testing models of exhumation. UHPM is registered in the rock record since the Cryogenian-Ediacaran; it is inferred to record deep subduction. UHP rocks decorate sutures in Phanerozoic subduction-to-collision orogens. During the Mesoarchean-Tonian, subduction-to-collision orogenesis was marked by eclogite - high-pressure granulite metamorphism (E-HPGM). The implied change in geodynamics was a legacy of Rodinia, and related to the birth of the Pacific during the formation of Gondwana. Hoffman-type supercontinent breakup (turns inside out by subduction of complementary superocean) was the process by which segments of Rodinia were reassembled to form Gondwana by suturing of Braziliano - Pan-African belts, leaving orphaned Laurasian segments to combine with each other and Gondwana to form Pangea. In contrast, Wilson cycles (continental lithosphere rearranged by formation- destruction

  10. Multi-stage metamorphism in the South Armenian Block during the Late Jurassic to Early Cretaceous: Tectonics over south-dipping subduction of Northern branch of Neotethys

    NASA Astrophysics Data System (ADS)

    Hässig, M.; Rolland, Y.; Sahakyan, L.; Sosson, M.; Galoyan, G.; Avagyan, A.; Bosch, D.; Müller, C.

    2015-04-01

    The geologic evolution of the South Armenian Block (SAB) in the Mesozoic is reconstructed from a structural, metamorphic, and geochronologic study including U-Pb and 40Ar/39Ar dating. The South Armenian Block Crystalline Basement (SABCB) outcrops solely in a narrow tectonic window, NW of Yerevan. The study of this zone provides key and unprecedented information concerning closing of the Northern Neotethys oceanic domain north of the Taurides-Anatolides platform from the Middle Jurassic to the Early Cretaceous. The basement comprises of presumed Proterozoic orthogneiss overlain by metamorphosed pelites as well as intrusions of granodiorite and leucogranite during the Late Jurassic and Early Cretaceous. Structural, geochronological and petrological observations show a multiphased evolution of the northern margin of the SAB during the Late Jurassic and Early Cretaceous. A south-dipping subduction under the East Anatolian Platform-South Armenian Block (EAP-SAB) is proposed in order to suit recent findings pertaining emplacement of relatively hot subduction related granodiorite as well as the metamorphic evolution of the crystalline basement in the Lesser Caucasus area. The metamorphism is interpreted as evidencing: (1) M1 Barrovian MP-MT conditions (staurolite-kyanite) at c. 157-160 Ma and intrusion of dioritic magmas at c. 150-156 Ma, (2) near-adiabatic decompression is featured by partial melting and production of leucogranites at c. 153 Ma, followed by M2 HT-LP conditions (andalusite-K-feldspar). A phase of shearing and recrystallization is ascribed to doming at c. 130-150 Ma and cooling at 400 °C by c. 123 Ma (M3). Structural observations show (1) top to the north shearing during M1 and (2) radial extension during M2. The extensional event ends by emplacement of a thick detrital series along radial S, E and W-dipping normal faults. Further, the crystalline basement is unconformably covered by Upper Cretaceous-Paleocene series dated by nannofossils, evolving from

  11. Magmatic and metamorphic belts and plutonic-metamorphic complexes of southeastern Alaska

    SciTech Connect

    Brew, D.A.; Himmelberg, G.R.; Ford, A.B.; Loney, R.A. . Branch of Alaskan Geology Univ. of Missouri, Columbia, MO . Dept. of Geology)

    1993-04-01

    The Cordilleran orogen in southeastern Alaska includes 24 distinct magmatic belts, ranging in age from Cambrian to Holocene, that are defined by map relations, lithology, age, and chemical composition. The youngest magmatic features are Quaternary-age pre- and post-glacial volcanic rocks that occur in three major fields in the region, as well as in isolated locations. Cenozoic magmatic features consist of four major and three minor belts. The major Tkope-Portland Peninsula belt of Oligocene age includes both volcanic and plutonic rocks. The major calcalkalic Coast Mountains belt of early and middle Eocene age is the single largest magmatic feature of the region. Early Tertiary and latest Cretaceous magmatism is represented by the major calcalkalic great tonalite sill belt, a remarkable long and narrow feature along the west side of the Coast Mountains. Cretaceous and Jurassic intrusive rocks occur in five major belts and two minor belts in the region and Paleozoic intrusive rocks occur in four major and two minor belts. The three major plutonic-metamorphic complexes (PMC), from east to west, are: the Coast PMC in the Coast Mountains; the Glacier Bay-Chichag of plutonic complex (Chugach MC) in the northern outer islands. The Coast PMC records dynamothermal and regional contact metamorphic events related to regional plutonism within several juxtaposed terranes; its lengthy and complicated history is related to the Late Cretaceous collision of the Alexander and Wrangellia terranes and the Gravina overlap assemblage to the west against the Yukon prong and Stikine terrane to the east. The relatively simple Glacier Bay PC history is recorded as the roots of a Late Jurassic through late Early Cretaceous island arc that probably developed during the early stages of the above tectonic event. The complicated Chugach MC history developed during and after the Late Cretaceous collision of the Chugach terrane with the Wrangellia and Alexander terranes.

  12. How to Combine Objectives and Methods of Evaluation in Iterative ILE Design: Lessons Learned from Designing Ambre-Add

    ERIC Educational Resources Information Center

    Nogry, S.; Jean-Daubias, S.; Guin, N.

    2012-01-01

    This article deals with evaluating an interactive learning environment (ILE) during the iterative-design process. Various aspects of the system must be assessed and a number of evaluation methods are available. In designing the ILE Ambre-add, several techniques were combined to test and refine the system. In particular, we point out the merits of…

  13. Ubiquitous brecciation after metamorphism in equilibrated ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Lusby, D.; Keil, K.

    1985-01-01

    Ten objects with aberrant Fe/(Fe + Mg) ratios have been found in apparently unbrecciated types 4-6 H and L chondrites. Since the Fe/(Fe + Mg) ratios of these objects are incompatible with the metamorphic history of the host chondrites, it is concluded that a high proportion of ordinary chondrites are breccias that were lithified after peak metamorphism. This is consistent with the results of Scott (1984), who concluded that most type three ordinary chondrites are breccias of materials with diverse thermal histories, even though they do not show prominent brecciation. It is found that the classification scheme of Van Schmus and Wood (1967) does not identify chondrites with similar thermal histories; the petrologic type of a chondrite is only a measure of the average thermal history of its ingredients. Chondrite and achondrite breccias are also compared in order to understand how brecciation of chondrites after metamorphism is so well camouflaged.

  14. Submarine hydrothermal metamorphism of the Del Puerto ophiolite, California.

    USGS Publications Warehouse

    Evarts, R.C.; Schiffman, P.

    1983-01-01

    Metamorphic zonation overprinted on the volcanic member and overlying volcanogenic sediments of the ophiolite complex increases downward in grade and is characterized by the sequential appearance with depth of zeolites, ferric pumpellyite and pistacitic epidote. Metamorphic assemblages of the plutonic member of the complex are characterized by the presence of calcic amphibole. The overprinting represents the effects of hydrothermal metamorphism resulting from the massive interaction between hot igneous rocks and convecting sea-water in a submarine environment. A thermal gradient of 100oC/km is postulated to account for the zonal recrystallization effects in the volcanic member. The diversity and sporadic distribution of mineral assemblages in the amphibole zone are considered due to the limited availability of H2O in the deeper part of the complex. Details of the zonation and representative microprobe analyses are tabulated.-M.S.

  15. Cathodoluminescence of diamond as an indicator of its metamorphic history

    NASA Astrophysics Data System (ADS)

    Kopylova, Maya; Bruce, Loryn; Longo, Micaela; Ryder, John; Dobrzhinetskaya, Larissa

    2010-05-01

    Diamond displays a supreme resistance to chemical and mechanical weathering, ensuring its survival through complex and prolonged crustal processes, including metamorphism and exhumation. For these reasons, volcanic sources and secondary and tertiary collectors for detrital placer diamonds, like Ural or Bingara diamonds, may be difficult to determine. If metamorphic processes leave their marks on diamond, they can be used to reconstruct crustal geologic processes and ages of primary diamondiferous volcanics. Four diamond suites extracted from metamorphic rocks have been characterized using optical CL, infrared and CL spectroscopy, and photoluminescence at the liquid nitrogen temperature. The studied diamonds are from the ~2.7 Ga sedimentary conglomerate and lamprophyric breccia metamorphosed in the greenschist facies (Wawa, Northern Ontario, Canada) during the 2.67 Ga Kenoran orogeny, and from the ultra-high pressure (UHP) terranes of Kokchetav (Kazakhstan) and Erzgebirge (Germany) exhumated in the Paleozoic. Wawa diamonds (Type IaAB and Type II) displayed green, yellow, orange, and red CL colours controlled by the CL emittance at 520, 576 nm, and between 586 and 664 nm. The UHP terranes diamonds show much weaker CL; few luminescent stones display CL peaks at 395, 498, 528 nm and a broad band at 580-668 nm. In contrast, most common diamonds found in unmetamorphosed rocks, i.e. octahedrally grown Type IaAB stones, luminescence blue emitting light at ~415-440 nm and 480-490 nm. There is a noticeable difference between cathodoluminescence of these diamonds and diamonds in metamorphic rocks. The studied diamonds that experienced metamorphism show a shift of CL emission to longer wavelengths (above 520 nm) and to green, yellow and red CL colours. Photoluminescence has the high resolution necessary to assign luminescence to specific optical centers of diamond. Diamonds in metamorphic rocks contain H3 (pairs of substitutional nitrogen atoms separated by a vacancy) and NVo

  16. [Spectrum research on metamorphic and deformation of tectonically deformed coals].

    PubMed

    Li, Xiao-Shi; Ju, Yi-Wen; Hou, Quan-Lin; Lin, Hong

    2011-08-01

    The structural and compositive evolution of tectonically deformed coals (TDCs) and their influencing factors were investigated and analyzed in detail through Fourier transform infrared spectroscopy (FTIR) and laser Raman spectra analysis. The TDC samples (0.7% < Ro,max <3.1%) were collected from Huaibei coalfield with different deformation mechanisms and intensity. The FTIR of TDCs shows that the metamorphism and the deformation affect the degradation and polycondensation process of macromolecular structure to different degree. The Raman spectra analysis indicates that secondary structure defects can be produced mainly by structural deformation, also the metamorphism influences the secondary structure defects and aromatic structure. Through comprehensive analysis, it was discussed that the ductile deformation could change to strain energy through the increase and accumulation of dislocation in molecular structure units of TDC, and it could make an obvious influence on degradation and polycondensation. While the brittle deformation could change to frictional heat energy and promote the metamorphism and degradation of TDC structure, but has less effect on polycondensation. Furthermore, degradation is the main reason for affecting the structural evolution of coal in lower metamorphic stage, and polycondensation is the most important controlling factor in higher metamorphic stage. Under metamorphism and deformation, the small molecules which break and fall off from the macromolecular tructure of TDC are preferentially replenished and embedded into the secondary structure defects or the residual aromatic rings were formed into aromatic structure by polycondensation. This process improved the stability of coal structure. It is easier for ductile deformation of coal to induce the secondary structure defects than brittle deformation. PMID:22007412

  17. Discrimination of metamorphic diamond populations by Raman spectroscopy (Kokchetav, Kazakhstan).

    PubMed

    Korsakov, Andrey V; Vandenabeele, Peter; Theunissen, Karel

    2005-08-01

    Metamorphic diamond is a powerful but frequently debated indicator for ultrahigh-pressure metamorphic (UHPM) conditions. Because of their small size, their optical identification needs confirmation. Characteristics of chemically extracted microdiamonds from Kokchetav, identified by different analytical methods, are used here for unambiguous in situ identification by Raman microspectroscopy. Differences appear in the diamond spectra and the Raman analytical method is explored as a helpful tool in the discrimination between diamond populations from four different UHPM lithologies of Kokchetav. Not considering the graphite-coated diamond, out of the reach of the laser wavelength used here, the comparison of these Kokchetav Raman spectra may provide additional information in other UHPM studies. PMID:16029860

  18. The onset of metamorphism in ordinary and carbonaceous chondrites

    USGS Publications Warehouse

    Grossman, J.N.; Brearley, A.J.

    2005-01-01

    Ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by X-ray mapping techniques. A variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cathodoluminescence (CL) methods. The distribution of Cr in FeO-rich olivine systematically changes as metamorphism increases between type 3.0 and type 3.2. Igneous zoning patterns are replaced by complex ones and Cr-rich coatings develop on all grains. Cr distributions in olivine are controlled by the exsolution of a Cr-rich phase, probably chromite. Cr in olivine may have been partly present as tetrahedrally coordinated Cr3+. Separation of chromite is nearly complete by petrologic type 3.2. The abundance of chondrules showing an inhomogeneous distribution of alkalis in mesostasis also increases with petrologic type. TEM shows this to be the result of crystallization of albite. Residual glass compositions systematically change during metamorphism, becoming increasingly rich in K. Glass in type I chondrules also gains alkalis during metamorphism. Both types of chondrules were open to an exchange of alkalis with opaque matrix and other chondrules. The matrix in the least metamorphosed chondrites is rich in S and Na. The S is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains. Progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules. Alkalis initially leave the matrix and enter chondrules during early metamorphism. Feldspar subsequently nucleates in the matrix and Na re-enters from chondrules. These metamorphic trends can be used to refine classification schemes for chondrites. Cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to

  19. Chlorine isotope behavior during prograde metamorphism of sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Selverstone, Jane; Sharp, Zachary D.

    2015-05-01

    Chlorine stable isotope compositions of two sedimentary sequences and their metamorphic equivalents were measured in order to study fractionation effects during prograde metamorphism and devolatilization. Protoliths (n = 25) were collected from a 50 m section of Triassic fluvial and playa-lake strata and Jurassic (Liassic) marine black shales in a well-characterized quarry. Low greenschist to middle amphibolite facies equivalents (n > 80) were collected from the Glarus Alps, Urseren Zone, and Lucomagno region. Bulk δ37Cl values are constant within individual sedimentary layers, but vary from -2.0 to + 2.4 ‰ in Triassic rocks and from -3.0 to 0‰ in the black shales. Dolomitic and gypsiferous samples have positive δ37Cl values, but marls and shales are isotopically negative. Bulk Cl contents show only small declines during the earliest stages of metamorphism. Metamorphic equivalents of the Triassic and Liassic protoliths record the same overall ranges in δ37Cl as their protoliths. Samples with highly correlated bulk compositions but different metamorphic grade show no statistically significant difference in δ37Cl. These data lead to the following conclusions: (1) Terrestrial and marine sedimentary rocks display large primary heterogeneities in chlorine isotope composition. As a result, an unambiguous "sedimentary signature" does not exist in the chlorine stable isotope system. (2) No isotopic fractionation is discernable during metamorphic devolatilization, even at low temperatures. Alpine-style metamorphism thus has little to no effect on bulk chlorine isotopic compositions, despite significant devolatilization. (3) Cl is largely retained in the rocks during devolatilization, contrary to the normally assumed hydrophilic behavior of chlorine. Continuous release of mixed-volatile C-O-H fluids likely affected Cl partitioning between fluid and minerals and allowed chlorine to remain in the rocks. (4) There is no evidence for fluid communication across (meta

  20. Metamorphism of the Oddanchatram anorthosite, Tamil Nadu, South India

    NASA Technical Reports Server (NTRS)

    Wiebe, R. A.; Janardhan, A. S.

    1988-01-01

    The Oddanchatram anorthosite is located in the Madurai District of Tamil Nadu, near the town of Palni. It is emplaced into a granulite facies terrain commonly presumed to have undergone its last regional metamorphism in the late Archean about 2600 m.y. The surrounding country rock consists of basic granulites, charnockites and metasedimentary rocks including quartzites, pelites and calc-silicates. The anorthosite is clearly intrusive into the country rock and contains many large inclusions of previously deformed basic granulite and quartzite within 100 meters of its contact. Both this intrusion and the nearby Kaduvar anorthosite show evidence of having been affected by later metamorphism and deformation.

  1. MetPetDB: New Directions for Metamorphic Studies

    NASA Astrophysics Data System (ADS)

    Spear, F. S.; Adali, S.; Szymanski, B. K.; Hallett, B. K.; Waters, A. J.; Linder, Z. J.; Fyffe, M. E.; Goldfarb, D.; Barlett, K.

    2008-12-01

    It is estimated that less than 1% of the data collected on metamorphic rocks is published, and MetPetDB (database for metamorphic geochemistry) is being developed and populated to preserve these data and to foster new and innovative directions for scientific research and education. The data model is based on a sample of metamorphic rock and includes information about location, rock type, mineral assemblage, fabric, plus images of all types and mineral composition data. Mineral analyses are linked to locations on appropriate images so the spatial integrity of the data is preserved. Tools will be available for mineral recalculation, plotting, and thermobarometric applications. Derivative data such as peak P-T conditions, metamorphic P-T path, and cooling rate will also be stored. The database will be searchable based on any number of data fields, permitting rapid location of samples that can be used to test hypotheses and discover new relationships. For example: A student is designing a thesis project and MetPetDB will be a first resource to determine the types of rocks present in a region, the work that has been done on them, and links to the published findings. The Fe/Mg zoning in migmatitic garnets has been used to infer cooling rates. What is the range of cooling rates recorded by migmatitic garnets, and is there a correlation between peak metamorphic temperature and cooling rate? Is it possible that melting triggers rapid thrusting that causes the rapid cooling? A search on: rock type = migmatite plus Fe and Mg X-ray maps of garnet would reveal all samples that could be used in this study. A new geobarometer based on a specific mineral assemblage is proposed that permits pressures to be estimated to within 50 MPa. A search of the database for all samples with this assemblage plus analyses of the necessary minerals would provide a set of samples to which this new barometer can be applied. Recalculating pressures and temperatures for an entire region using new

  2. Links between fluid circulation, temperature, and metamorphism in subducting slabs

    USGS Publications Warehouse

    Spinelli, G.A.; Wang, K.

    2009-01-01

    The location and timing of metamorphic reactions in subducting lithosph??re are influenced by thermal effects of fluid circulation in the ocean crust aquifer. Fluid circulation in subducting crust extracts heat from the Nankai subduction zone, causing the crust to pass through cooler metamorphic faci??s than if no fluid circulation occurs. This fluid circulation shifts the basalt-to-eclogite transition and the associated slab dehydration 14 km deeper (35 km farther landward) than would be predicted with no fluid flow. For most subduction zones, hydrothermal cooling of the subducting slab will delay eclogitization relative to estimates made without considering fluid circulation. Copyright 2009 by the American Geophysical Union.

  3. Meteoric water in metamorphic core complexes

    NASA Astrophysics Data System (ADS)

    Teyssier, Christian; Mulch, Andreas

    2015-04-01

    The trace of surface water has been found in all detachment shear zones that bound the Cordilleran metamorphic core complexes of North America. DeltaD values of mica fish in detachment mylonites demonstrate that these synkinematic minerals grew in the presence of meteoric water. Typically deltaD values are very negative (-120 to -160 per mil) corresponding to deltaD values of water that are < -100 per mil given the temperature of water-mica isotopic equilibration (300-500C). From British Columbia (Canada) to Nevada (USA) detachment systems bound a series of core complexes: the Thor-Odin, Valhalla, Kettle-Okanogan, Bitterroot -Anaconda, Pioneer, Raft River, Ruby Mountain, and Snake Range. The bounding shear zones range in thickness from ~100 m to ~1 km, and within the shear zones, meteoric water signature is recognized over 10s to 100s of meters beneath the detachment fault. The age of shearing ranges generally from Eocene in the N (~50-45 Ma) to Oligo-Miocene in the S (25-15 Ma). DeltaD water values derived from mica fish in shear zones are consistent with supradetachment basin records of the same age brackets and can be used for paleoaltimetry if coeval isotopic records from near sea level are available. Results show that a wave of topography (typically 4000-5000 m) developed from N to S along the Cordillera belt from Eocene to Miocene, accompanied by the propagation of extensional deformation and volcanic activity. In addition, each detachment system informs a particular extensional detachment process. For example, the thick Thor-Odin detachment shear zone provides sufficient age resolution to indicate the downward propagation of shearing and the progressive incorporation of footwall rocks into the hanging wall. The Kettle detachment provides a clear illustration of the dependence of fluid circulation on dynamic recrystallization processes. The Raft River system consists of a thick Eocene shear zone that was overprinted by Miocene shearing; channels of meteoric

  4. Westward prograding metamorphism in mantle peridotites from the Eastern Desert of Egypt: clues to the subduction polarity of the Arabian Nubian Shield intra-oceanic arc ophiolite

    NASA Astrophysics Data System (ADS)

    Salam Abu El-Ela, Abdel; Hamdy, Mohamed; Abu-Alam, Tamer; Hassan, Adel; Gamal El Dien, Hamed

    2013-04-01

    Neoproterozoic arc mantle beneath the Arabian Nubian Shield (ANS) in the Eastern Desert (ED) of Egypt exhumed due to intra-oceanic upthrusting are represented mainly by exposed ophiolitic peridotites serpentinized to different degree. Metamorphism is related to the Pan-African collision and the subduction of oceanic lithosphere. However, polarity of the Pan-African intra-oceanic subduction is still questionable. We here trace the variation of the degree of serpentinization and regional metamorphism of six serpentinite masses, widely distributed in the ED (from the east to the west: W (Wadi). Alam, W. Igla, W. Mubarak, G. El-Maiyit, W. Um El Saneyat and W. Atalla). This is based on their mineralogy, textures and mineral chemistry. The studied rocks have harzburgite composition and they all formed in oceanic mantle wedge in the fore-arc setting, except those from W. Atalla that formed in MOR-arc transition setting. Much difference in the degree of serpentinization is obvious among these rocks. They are mainly partly serpentinized containing primary olivine and orthopyroxene at W. Alam and W. Igla, while they are completely serpentinized in the other localities. With the increased degree of metamorphism, textures were transformed from the pseudomorphic to the non-pseudomorphic. The most common retrograde assemblage is composed of lizardite ± chrysotile± brucite± magnetite. The serpentine prograde textures can be viewed as a continuum from retrograde lizardite pseudomorphic textures, to very fine-grained transitional texture of lizardite and chrysotile, to chrysotile-antigorite interlocking texture and finally to antigorite interpenetrating texture. These textures appear to represent successive stages in a recrystallization event. In late subduction-related metamorphism and early collisional emplacement stage, mylonitic-antigorite serpentinites formed and antigorite became the major phase in G. El-Maiyit, Um El-Saneyat and W. Atalla. The polygonal units of the

  5. Parental Socio-Economic Status as Correlate of Child Labour in Ile-Ife, Nigeria

    ERIC Educational Resources Information Center

    Elegbeleye, O. S.; Olasupo, M. O.

    2012-01-01

    This study investigated the relationship between parental socio-economic status and child labour practices in Ile-Ife, Nigeria. The study employed survey method to gather data from 200 parents which constituted the study population. Pearson Product Moment Correlation and t-test statistics were used for the data analyses. The outcome of the study…

  6. A prospective evaluation of the transthyretin Ile122 allele frequency in an African-American population.

    PubMed

    Yamashita, Taro; Hamidi Asl, Kamran; Yazaki, Masahide; Benson, Merrill D

    2005-06-01

    Transthyretin Val122Ile is one of greater than 80 mutations in transthyretin (TTR) that are associated with hereditary amyloidosis. Retrospective studies have shown a prevalence of this mutation as high as 3.9% in African-Americans. The present study was undertaken to determine in a prospective fashion the prevalence of the TTR Val122Ile allele in African-Americans in a Midwestern American city. DNA was isolated from cord bloods collected at the time of birth in the County hospital of Indianapolis, Indiana. Samples were identified only as to ethnic origin of the mother. Analysis was performed by PCR amplification of TTR exon 4 followed by SSCP and RFLP. Cord bloods from 1,973 children born at the County hospital were analyzed. Thirty of 1,000 DNA samples from African-American newborns were positive for TTR Val122Ile (3%). Two of 453 DNA samples from Caucasian newborns were positive (0.44%). Zero of 490 DNA samples from newborns of Hispanic mothers and 0 of 30 from newborns with mothers classified as other (including Asian) were positive. This prospective study demonstrates that 3% of newborns of African-American women in an urban population have the TTR Val122Ile mutation which is associated with late-onset cardiomyopathy. The degree of penetrance of this mutation at the clinical level has not yet been determined. PMID:16011990

  7. Management of Primary Dysmenorrhea by School Adolescents in ILE-IFE, Nigeria

    ERIC Educational Resources Information Center

    Ogunfowokan, Adesola A.; Babatunde, Oluwayemisi A.

    2010-01-01

    Dysmenorrhea is a problem that girls and women face and often manage themselves with or without support from health professionals. A cross-sectional, descriptive study was conducted among adolescents with dysmenorrhea (N = 150) in Ile-Ife, Nigeria. The aims of the study were to determine their knowledge of menstruation and primary dysmenorrhea,…

  8. Mesoproterozoic syntectonic garnet within Belt Supergroup metamorphic tectonites: Evidence of Grenville-age metamorphism and deformation along northwest Laurentia

    USGS Publications Warehouse

    Nesheim, T.O.; Vervoort, J.D.; McClelland, W.C.; Gilotti, J.A.; Lang, H.M.

    2012-01-01

    Northern Idaho contains Belt-Purcell Supergroup equivalent metamorphic tectonites that underwent two regional deformational and metamorphic events during the Mesoproterozoic. Garnet-bearing pelitic schists from the Snow Peak area of northern Idaho yield Lu-Hf garnet-whole rock ages of 1085??2. Ma, 1198??79. Ma, 1207??8. Ma, 1255??28. Ma, and 1314??2. Ma. Garnet from one sample, collected from the Clarkia area, was micro-drilled to obtain separate core and rim material that produced ages of 1347??10. Ma and 1102??47. Ma. The core versus rim ages from the micro-drilled sample along with the textural and spatial evidence of the other Lu-Hf garnet ages indicate two metamorphic garnet growth events at ~. 1330. Ma (M1) and ~. 1080. Ma (M2) with the intermediate ages representing mixed ages. Some garnet likely nucleated and grew M1 garnet cores that were later overgrown by younger M2 garnet rims. Most garnet throughout the Clarkia and Snow Peak areas are syntectonic with a regional penetrative deformational fabric, preserved as a strong preferred orientation of metamorphic matrix minerals (e.g., muscovite and biotite). The syntectonic garnets are interpreted to represent one regional, coeval metamorphic and deformation event at ~. 1080. Ma, which overlaps in time with the Grenville Orogeny. The older ~. 1330. Ma ages may represent an extension of the East Kootenay Orogeny described in western Canada. These deformational and metamorphic events indicate that western Laurentia (North America) was tectonically active in the Mesoproterozoic and during the assembly of the supercontinent Rodinia. ?? 2011 Elsevier B.V.

  9. Mesoproterozoic syntectonic garnet within Belt Supergroup metamorphic tectonites: Evidence of Grenville-age metamorphism and deformation along northwest Laurentia

    NASA Astrophysics Data System (ADS)

    Nesheim, Timothy O.; Vervoort, Jeffrey D.; McClelland, William C.; Gilotti, Jane A.; Lang, Helen M.

    2012-03-01

    Northern Idaho contains Belt-Purcell Supergroup equivalent metamorphic tectonites that underwent two regional deformational and metamorphic events during the Mesoproterozoic. Garnet-bearing pelitic schists from the Snow Peak area of northern Idaho yield Lu-Hf garnet-whole rock ages of 1085 ± 2 Ma, 1198 ± 79 Ma, 1207 ± 8 Ma, 1255 ± 28 Ma, and 1314 ± 2 Ma. Garnet from one sample, collected from the Clarkia area, was micro-drilled to obtain separate core and rim material that produced ages of 1347 ± 10 Ma and 1102 ± 47 Ma. The core versus rim ages from the micro-drilled sample along with the textural and spatial evidence of the other Lu-Hf garnet ages indicate two metamorphic garnet growth events at ~ 1330 Ma (M1) and ~ 1080 Ma (M2) with the intermediate ages representing mixed ages. Some garnet likely nucleated and grew M1 garnet cores that were later overgrown by younger M2 garnet rims. Most garnet throughout the Clarkia and Snow Peak areas are syntectonic with a regional penetrative deformational fabric, preserved as a strong preferred orientation of metamorphic matrix minerals (e.g., muscovite and biotite). The syntectonic garnets are interpreted to represent one regional, coeval metamorphic and deformation event at ~ 1080 Ma, which overlaps in time with the Grenville Orogeny. The older ~ 1330 Ma ages may represent an extension of the East Kootenay Orogeny described in western Canada. These deformational and metamorphic events indicate that western Laurentia (North America) was tectonically active in the Mesoproterozoic and during the assembly of the supercontinent Rodinia.

  10. From intra-oceanic subduction to arc accretion and arc-continent collision: Insights from the structural evolution of the Río San Juan metamorphic complex, northern Hispaniola

    NASA Astrophysics Data System (ADS)

    Escuder-Viruete, Javier; Valverde-Vaquero, Pablo; Rojas-Agramonte, Yamirka; Jabites, Janet; Pérez-Estaún, Andrés

    2013-01-01

    The Río San Juan metamorphic complex exposes a segment of a high-pressure subduction-accretionary complex built during Caribbean island arc-North America continental margin convergence. It is composed of accreted arc- and oceanic-derived metaigneous rocks, serpentinized peridotites and minor metasediments forming a structural pile. Combined detailed mapping, structural and metamorphic analysis, and geochronology show that the deformation can be divided into five main events (D1-D5). An early subduction-related D1 deformation and M1 metamorphism produced greenschist (mafic rocks of the Gaspar Hernández peridotite-tectonite), blueschist and eclogite (metamafic blocks in the Jagua Clara mélange), high-P epidote-amphibolite and eclogite (Cuaba unit), and lower blueschist and greenschist-facies conditions (Morrito unit). This was followed by M2 decompression and cooling in the blueschist, greenschist and low-P amphibolite-facies conditions. The shape of the retrograde P-T path, the age of the exhumation-related D2 structures, and the tectonic significance of D2 deformation are different in each structural unit. Published U-Pb and 40Ar/39Ar plateau ages and T-t/P-t estimations reveal diachronic Turonian-Coniacian to Maastrichtian retrograde M2 metamorphism in the different structural units of the complex, during a consistent D2 top-to-the-NE/ENE tectonic transport. Regionally, a similar top-to-the-ENE tectonic transport also took place in the metasedimentary nappes of the Samaná complex during the Eocene to earliest Miocene. This kinematic compatibility indicates a general northeastward progradation of deformation in the northern Caribbean convergent margin, as the successive tectonic incorporation of arc, oceanic and continental-derived terrains to the developing Caribbean subduction-accretionary complex took place. D3-D5 deformations are discontinuous and much less penetrative, recording the evolution from ductile to brittle conditions of deformation in the complex

  11. Nature and origin of fluids in granulite facies metamorphism

    NASA Technical Reports Server (NTRS)

    Newton, R. C.

    1988-01-01

    The various models for the nature and origin of fluids in granulite facies metamorphism were summarized. Field and petrologic evidence exists for both fluid-absent and fluid-present deep crustal metamorphism. The South Indian granulite province is often cited as a fluid-rich example. The fluids must have been low in H2O and thus high in CO2. Deep crustal and subcrustal sources of CO2 are as yet unproven possibilities. There is much recent discussion of the possible ways in which deep crustal melts and fluids could have interacted in granulite metamorphism. Possible explanations for the characteristically low activity of H2O associated with granulite terranes were discussed. Granulites of the Adirondacks, New York, show evidence for vapor-absent conditions, and thus appear different from those of South India, for which CO2 streaming was proposed. Several features, such as the presence of high-density CO2 fluid inclusions, that may be misleading as evidence for CO2-saturated conditions during metamorphism, were discussed.

  12. Metamorphism, alteration, and timing of mineralization at Hemlo, Ontario

    SciTech Connect

    Ferreira, M.C.; Fyfe, W.S.

    1985-01-01

    Relative age discrimination between metamorphic and mineralizing processes related to Archean gold deposits is often equivocal. The mineralogy and/or stability range of hydrothermal alteration assemblages in and around the deposits are, in most cases, similar to the low grade metamorphic assemblages characteristic of their host sequences. At Hemlo, the distinction is made easier by the relatively high metamorphic rank recorded in the host rocks. From a regional perspective, the mineralization at Hemlo sits in a highly deformed zone flanked by intermediate to mafic volcanic rocks in the footwall, and clastic to volcaniclastic (sensu lato) rocks in the hanging wall. Amphibolite facies assemblages in both hanging wall and footwall are progressively altered, via hydrolysis and hydration, to greenschist facies assemblages. The extent and intensity of alteration increase towards the mineralization. Accordingly, alteration and mineralization at Hemlo postdate peak metamorphic conditions. Whereas structurally enhanced permeability may have played an important role in facilitating access to mineralizing solutions, gold deposition was probably controlled by host rock composition and reactivity. Gold precipitation may have been triggered by an increase in hydrogen ion activity of mineralizing solutions related to white mica replacement of aluminosilicates.

  13. Nature and origin of fluids in granulite facies metamorphism

    NASA Astrophysics Data System (ADS)

    Newton, R. C.

    The various models for the nature and origin of fluids in granulite facies metamorphism were summarized. Field and petrologic evidence exists for both fluid-absent and fluid-present deep crustal metamorphism. The South Indian granulite province is often cited as a fluid-rich example. The fluids must have been low in H2O and thus high in CO2. Deep crustal and subcrustal sources of CO2 are as yet unproven possibilities. There is much recent discussion of the possible ways in which deep crustal melts and fluids could have interacted in granulite metamorphism. Possible explanations for the characteristically low activity of H2O associated with granulite terranes were discussed. Granulites of the Adirondacks, New York, show evidence for vapor-absent conditions, and thus appear different from those of South India, for which CO2 streaming was proposed. Several features, such as the presence of high-density CO2 fluid inclusions, that may be misleading as evidence for CO2-saturated conditions during metamorphism, were discussed.

  14. Organic nitrogen chemistry during low-grade metamorphism

    USGS Publications Warehouse

    Boudou, J.-P.; Schimmelmann, A.; Ader, M.; Mastalerz, Maria; Sebilo, M.; Gengembre, L.

    2008-01-01

    Most of the organic nitrogen (Norg) on Earth is disseminated in crustal sediments and rocks in the form of fossil nitrogen-containing organic matter. The chemical speciation of fossil Norg within the overall molecular structure of organic matter changes with time and heating during burial. Progressive thermal evolution of organic matter involves phases of enhanced elimination of Norg and ultimately produces graphite containing only traces of nitrogen. Long-term chemical and thermal instability makes the chemical speciation of Norg a valuable tracer to constrain the history of sub-surface metamorphism and to shed light on the subsurface biogeochemical nitrogen cycle and its participating organic and inorganic nitrogen pools. This study documents the evolutionary path of Norg speciation, transformation and elimination before and during metamorphism and advocates the use of X-ray photoelectron spectroscopy (XPS) to monitor changes in Norg speciation as a diagnostic tool for organic metamorphism. Our multidisciplinary evidence from XPS, stable isotopes, traditional quantitative coal analyses, and other analytical approaches shows that at the metamorphic onset Norg is dominantly present as pyrrolic and pyridinic nitrogen. The relative abundance of nitrogen substituting for carbon in condensed, partially aromatic systems (where N is covalently bonded to three C atoms) increases exponentially with increasing metamorphic grade, at the expense of pyridinic and pyrrolic nitrogen. At the same time, much Norg is eliminated without significant nitrogen isotope fractionation. The apparent absence of Rayleigh-type nitrogen isotopic fractionation suggests that direct thermal loss of nitrogen from an organic matrix does not serve as a major pathway for Norg elimination. Instead, we propose that hot H, O-containing fluids or some of their components gradually penetrate into the carbonaceous matrix and eliminate Norg along a progressing reaction front, without causing nitrogen

  15. Oman metamorphic sole formation reveals early subduction dynamics

    NASA Astrophysics Data System (ADS)

    Soret, Mathieu; Agard, Philippe; Dubacq, Benoît; Plunder, Alexis; Ildefonse, Benoît; Yamato, Philippe; Prigent, Cécile

    2016-04-01

    Metamorphic soles correspond to m to ~500m thick tectonic slices welded beneath most of the large-scale ophiolites. They typically show a steep inverted metamorphic structure where the pressure and temperature conditions of crystallization increase upward (from 500±100°C at 0.5±0.2 GPa to 800±100°C at 1.0±0.2 GPa), with isograds subparallel to the contact with the overlying ophiolitic peridotite. The proportion of mafic rocks in metamorphic soles also increases from the bottom (meta-sediments rich) to the top (approaching the ophiolite peridotites). These soles are interpreted as the result of heat transfer from the incipient mantle wedge toward the nascent slab (associated with large-scale fluid transfer and possible shear heating) during the first My of intra-oceanic subduction (as indicated by radiometric ages). Metamorphic soles provide therefore major constraints on early subduction dynamics (i.e., thermal structure, fluid migration and rheology along the nascent slab interface). We present a detailed structural and petrological study of the metamorphic sole from 4 major cross-sections along the Oman ophiolite. We show precise pressure-temperature estimates obtained by pseudosection modelling and EBSD measurements performed on both the garnet-bearing and garnet-free high-grade sole. Results allow quantification of the micro-scale deformation and highlight differences in pressure-temperature-deformation conditions between the 4 different locations, showing that the inverted metamorphic gradient through the sole is not continuous in all locations. Based on these new constraints, we suggest a new tectonic-petrological model for the formation of metamorphic soles below ophiolites. This model involves the stacking of several homogeneous slivers of oceanic crust leading to the present-day structure of the sole. In this view, these thrusts are the result of rheological contrasts between the sole and the peridotite as the plate interface progressively cools down

  16. Microstructures and flow mechanisms in regional metamorphic rocks of Japan

    NASA Astrophysics Data System (ADS)

    Toriumi, Mitsuhiro; Teruya, Jun; Masui, Megumi; Kuwahara, Hidesato

    1986-09-01

    A number of microstructural features indicate a difference in the dominant deformation mechanism between the higher temperature Ryoke and the lower temperature Sambagawa and Shimanto metamorphic belts of Japan. The microstructures of metacherts containing deformed radiolaria are divided into two types: in both the Sambagawa and Shimanto belts the quartz grains are tabular while in the Ryoke belt they are equiaxed. TEM studies of these metacherts revealed that the tabular grains contain abundant subboundaries consisting of large numbers of network dislocations and bowe-out dislocations, while the equiaxed grains contain no subboundaries and have low densities of dislocations which are not bowed-out. There is a corresponding difference in the textures (lattice preferred orientation of quartz): the Ryoke metacherts display randomly distributed c-axes of quartz, while the Sambagawa and Shimanto metacherts show conspicuous crossed girdle patterns with some asymmetry. There is a third difference between these regions: in the metacherts of the Ryoke metamorphic belt, the strain magnitudes determined from deformed radiolaria increase with increasing volume fraction of mica in the same metamorphic P and T conditions, while in the Sambagawa and the Shimanto metamorphic cherts the strain magnitudes decrease with increasing the mica fraction. These microstructures, textures, and rheological behaviours of quartz-mica rocks suggest a change of deformation mechanism between the lower temperature Sambagawa and Shimanto, and the higher temperature Ryoke metamorphic belts. Since random fabrics of c-axes of quartz are inconsistent with lattice rotation due to dislocation glide, the Ryoke metacherts may have deformed by pressure-solution.

  17. Heat sources for tertiary metamorphism and anatexis in the Annapurna-Manaslu region, central Nepal

    NASA Technical Reports Server (NTRS)

    England, Philip; Le Fort, Patrick; Molnar, Peter; Pecher, Arnaud

    1992-01-01

    The metamorphic evolution of the rocks near the Main Central Thrust in the Annapurna-Manaslu region of central Nepal is examined. In this region, all three types of metamorphic features can be observed: regional metamorphism, anatectic granitoids, and inverted metamorphic isograds. In this work, each phase of metamorphism is treated separately to estimate the heat sources required for each process. This approach makes it possible to identify the important parameters for each process, to draw preliminary conclusions about the heat sources required for each of these phases, and to determine which parameters need to be measured more precisely in order to constrain these heat sources.

  18. Metamorphic facies map of Southeastern Alaska; distribution, facies, and ages of regionally metamorphosed rocks

    USGS Publications Warehouse

    Dusel-Bacon, Cynthia; Brew, D.A.; Douglass, S.L.

    1996-01-01

    Nearly all of the bedrock in Southeastern Alaska has been metamorphosed, much of it under medium-grade conditions during metamorphic episodes that were associated with widespread plutonism. The oldest metamorphisms affected probable arc rocks near southern Prince of Wales Island and occurred during early and middle Paleozoic orogenies. The predominant period of metamorphism and associated plutonism occurred during Early Cretaceous to early Tertiary time and resulted in the development of the Coast plutonic-metamorphic complex that extends along the inboard half of Southeastern Alaska. Middle Tertiary regional thermal metamorphism affected a large part of Baranof Island.

  19. Metamorphic manipulating mechanism design for MCCB using index reduced iteration

    NASA Astrophysics Data System (ADS)

    Xu, Jinghua; Zhang, Shuyou; Zhao, Zhen; Lin, Xiaoxia

    2013-03-01

    The present research on moulded case circuit breaker(MCCB) focuses on the enhancement of current-limiting interrupting performance during short circuit, overload, under voltage and phase failure, involving electrics, magnetic, mechanics, thermal, material, friction, arc extinguishing, impact vibration, skin effect, etc. The rigid-flexible coupling of the parts and components of the metamorphic manipulating mechanism in multi-fields leads to the non-rigid, high frequency, high damping, singularity of the Euler-Lagrange equations which represents the multi-body dynamics. The small step iteration which is used for obtaining the instantaneous and short time critical interrupting performance of metamorphic mechanism appears inaccuracy. It is difficult to realize top-down design by existing CAD systems. Therefore, a metamorphic manipulating mechanism design method for MCCB using index reduced iteration(IRI) is put forward. The metamorphic manipulating mechanism of MCCB is decomposed into three mechanisms: main switch connector mechanism, electromagnet-drawbar-jump buckle mechanism, and bimetallic strip-drawbar mechanism, which is respectively described by electro-dynamic force, electromagnet force, and bimetallic strip force. The dummy part(virtual rigid) without moment of inertia and mass is employed as intermediate to join the flexible body and rigid body. The model of rigid-flexible coupling metamorphic mechanism multi-body dynamics is built. The differential algebraic equations(DAEs) of the multibody dynamics model are converted to pure ordinary differential equations(ODEs) by coordinate partition. Order reduced integration with multi-step and variable step-size is preceded based on IRI. The non-linear algebraic equations are solved in each integration step by Newton-Rapson iteration. There is no ill-condition and singularity of Jacobian matrix when step size reduces to zero. The independent prototype design system using ACIS R13, HOOPS V11.0 and Visual C++.NET 2003

  20. CARBONACEOUS MATTER PRECURSORS AND METAMORPHIC CONDITIONS IN THERMALLY PROCESSED CHONDRITES

    NASA Astrophysics Data System (ADS)

    Quirico, E.; Montagnac, G.; Rouzaud, J.; Bonal, L.; Bourot-Denise, M.; Duber, S.; Reynard, B.

    2009-12-01

    Unravelling the origin of carbonaceous matter in pristine chondrites requires the understanding of the effect of post-accretion processes. In chondrites of petrologic type 3, thermal metamorphism modified to various extents the composition and structure of carbonaceous matter. Interestingly, this process controls the degree of structural order of carbonaceous matter, and clues on the thermal history of the parent body may be recovered from the physico-chemical study of carbonaceous matter. Following this framework, geothermometers based on Raman spectrometry of carbonaceous matter and covering a wide range of temperatures (100-650 °C) have been developed over recent years, both on terrestrial rocks and chondrites. While Raman data have been largely interpreted in terms of temperature, they are also the fingerprint of certain metamorphic conditions, especially in the low temperature range relevant to poorly ordered carbonaceous matter. This study investigates the Raman spectra of two series of chondritic carbonaceous matter and coal samples formed from different precursors and under different metamorphic conditions. The Raman spectra of Polyaromatic Carbonaceous Matter (PCM) from 42 chondrites and 27 coal samples, measured with visible (514 nm) and ultra-violet (244 nm) excitation wavelengths, are analyzed. The Raman spectra of low rank coals and chondrites of petrologic types 1 and 2, which contain the more disordered PCM, reflect the distinct carbon structures of their precursors. The 514 nm Raman spectra of high rank coals and chondrites of petrologic type 3 exhibit continuous and systematic spectral differences reflecting different carbon structures present during the metamorphism event. They result from differences in the chemical structures of the precursors concerning for instance the reticulation of polyaromatic units or an abundance of ether functional groups, or possibly from a lack of carbonization processes to efficiently expel oxygen heteroatoms, due

  1. Metamorphic density controls on early-stage subduction dynamics

    NASA Astrophysics Data System (ADS)

    Duesterhoeft, Erik; Oberhänsli, Roland; Bousquet, Romain

    2013-04-01

    Subduction is primarily driven by the densification of the downgoing oceanic slab, due to dynamic P-T-fields in subduction zones. It is crucial to unravel slab densification induced by metamorphic reactions to understand the influence on plate dynamics. By analyzing the density and metamorphic structure of subduction zones, we may gain knowledge about the driving, metamorphic processes in a subduction zone like the eclogitization (i.e., the transformation of a MORB to an eclogite), the breakdown of hydrous minerals and the release of fluid or the generation of partial melts. We have therefore developed a 2D subduction zone model down to 250 km that is based on thermodynamic equilibrium assemblage computations. Our model computes the "metamorphic density" of rocks as a function of pressure, temperature and chemical composition using the Theriak-Domino software package at different time stages. We have used this model to investigate how the hydration, dehydration, partial melting and fractionation processes of rocks all influence the metamorphic density and greatly depend on the temperature field within subduction systems. These processes are commonly neglected by other approaches (e.g., gravitational or thermomechanical in nature) reproducing the density distribution within this tectonic setting. The process of eclogitization is assumed as being important to subduction dynamics, based on the very high density (3.6 g/cm3) of eclogitic rocks. The eclogitization in a MORB-type crust is possible only if the rock reaches the garnet phase stability field. This process is primarily temperature driven. Our model demonstrates that the initiation of eclogitization of the slab is not the only significant process that makes the descending slab denser and is responsible for the slab pull force. Indeed, our results show that the densification of the downgoing lithospheric mantle (due to an increase of pressure) starts in the early subduction stage and makes a significant

  2. Metamorphism and partial melting of ordinary chondrites: Calculated phase equilibria

    NASA Astrophysics Data System (ADS)

    Johnson, T. E.; Benedix, G. K.; Bland, P. A.

    2016-01-01

    Constraining the metamorphic pressures (P) and temperatures (T) recorded by meteorites is key to understanding the size and thermal history of their asteroid parent bodies. New thermodynamic models calibrated to very low P for minerals and melt in terrestrial mantle peridotite permit quantitative investigation of high-T metamorphism in ordinary chondrites using phase equilibria modelling. Isochemical P-T phase diagrams based on the average composition of H, L and LL chondrite falls and contoured for the composition and abundance of olivine, ortho- and clinopyroxene, plagioclase and chromite provide a good match with values measured in so-called equilibrated (petrologic type 4-6) samples. Some compositional variables, in particular Al in orthopyroxene and Na in clinopyroxene, exhibit a strong pressure dependence when considered over a range of several kilobars, providing a means of recognising meteorites derived from the cores of asteroids with radii of several hundred kilometres, if such bodies existed at that time. At the low pressures (<1 kbar) that typify thermal metamorphism, several compositional variables are good thermometers. Although those based on Fe-Mg exchange are likely to have been reset during slow cooling, those based on coupled substitution, in particular Ca and Al in orthopyroxene and Na in clinopyroxene, are less susceptible to retrograde diffusion and are potentially more faithful recorders of peak conditions. The intersection of isopleths of these variables may allow pressures to be quantified, even at low P, permitting constraints on the minimum size of parent asteroid bodies. The phase diagrams predict the onset of partial melting at 1050-1100 °C by incongruent reactions consuming plagioclase, clinopyroxene and orthopyroxene, whose compositions change abruptly as melting proceeds. These predictions match natural observations well and support the view that type 7 chondrites represent a suprasolidus continuation of the established petrologic

  3. Metamorphic materials: bulk electromagnetic transitions realized in electronically reconfigurable composite media.

    PubMed

    Kyriazidou, Chryssoula A; Contopanagos, Harry F; Alexopoulos, Nicolaos G

    2006-11-01

    We present what we believe is a new class of composite electromagnetic materials characterized by the concept of metamorphism, which we define in general terms. Metamorphic materials exhibit bulk electromagnetic transitions among states characterized by distinct ranges of values of their reflection coefficient. Each such state has unique physical properties induced by the corresponding values of the reflection coefficient. We present a variety of physical realizations of the concept of metamorphic materials in microwave frequencies, showing with specific metallodielectric designs how transitions among metamorphic states can be obtained at the same frequency, for fixed material geometries, by electronic reconfigurability. We further show how a given material exhibiting certain metamorphic states at a given frequency can transform into a different combination of metamorphic states at different frequencies; i.e., metamorphic materials have a useful dispersive degree of freedom. PMID:17047724

  4. Hereditary cardiac amyloidosis associated with the transthyretin Ile122 mutation in a white man

    PubMed Central

    Gillmore, J; Booth, D; Pepys, M; Hawkins, P

    1999-01-01

    An 83 year old white man with atrial fibrillation was admitted to hospital after a cerebral infarct. Echocardiography was characteristic of cardiac amyloid deposition and subsequent tests confirmed amyloidosis of transthyretin (TTR) type, in association with the Ile122 mutation of the TTR gene; this has only been reported previously in African Americans in whom it occurs with an allele frequency of 2%. Haplotype analysis did not suggest a different founder than for the African Ile122 mutation. Cardiac amyloidosis should be considered among elderly patients presenting with cardiac failure and/or arrhythmia, particularly if they are resistant to conventional treatment; if confirmed, it should be followed by precise characterisation of amyloid fibril type. The prevalence of autosomal dominant cardiac TTR amyloidosis in elderly white people is unknown but early diagnosis and supportive treatment may prevent complications among affected family members.


Keywords: amyloid; amyloidosis; transthyretin; hereditary amyloidosis; stroke PMID:10455100

  5. Transthyretin Val122Ile, accumulated Abeta, and inclusion-body myositis aspects in cultured muscle.

    PubMed

    Askanas, Valerie; Engel, W King; McFerrin, Janis; Vattemi, Gaetano

    2003-07-22

    Cultured muscle fibers (CMF) from a patient with inclusion-body myositis (IBM) and cardiac amyloidosis associated with the transthyretin (TTR) Val122Ile mutation contained aspects of the IBM phenotype: vacuolation, congophilic inclusions, and clusters of immunocolocalizing amyloid beta-peptide (Abeta) and TTR accumulations. These abnormalities are never present in normal human CMF. These perturbations were greatly increased after Abeta precursor protein gene transfer. The TTR mutation may be a genetic predisposition factor for the patient's IBM. PMID:12874414

  6. A mantle- and a lower crust-derived bimodal suite in the Yusufeli (Artvin) area, NE Turkey: trace element and REE evidence for subduction-related rift origin of Early Jurassic Demirkent intrusive complex

    NASA Astrophysics Data System (ADS)

    Dokuz, Abdurrahman; Tanyolu, Erkan; Genç, Salim

    2006-06-01

    The Yusufeli area, in the Eastern Black Sea Region of Turkey, contains a crystalline complex that intruded into the Carboniferous metamorphic basement and is composed of two intrusive bodies: a gabbro-diorite and a tonalite-trondhjemite. The mafic body (45 57 wt% SiO2) displays a broad lithological spectrum ranging from plagioclase-cumulate to quartz diorite. Primitive varieties of the body have Mg-number, MgO and Cr contents that are close to those expected for partial melts from mantle peridotite. Data are consistent with the magma generation in an underlying mantle wedge that was depleted in Zr, Nb and Ti, and enriched in large ion lithophile elements (K, Rb, Ba, Th). However, high Al2O3, CaO and generally low Ni (<65 ppm) contents are not in agreement with the unfractionated mantle-derived primitive magmas and require some Al2O3- and CaO-poor mafic phases, in particular, olivine and orthopyroxene. Absence of orthopyroxene in crystallization sequence, uralitization, and a common appearance of clinopyroxene surrounded by hornblende imply an anhydrous phase fractionated from highly hydrous (5 6%) parent. Geochemical modelling suggests derivation by 15 20% melting of a depleted-lherzolitic mantle. The tonalite-trondhjemite body (58 76 wt% SiO2) ranges in composition from quartz diorite to granodiorite with a low-K calc-alkaline trend. Although LILE- and LREE- enriched characteristics of the primitive samples imply a metasomatic sub-arc mantle for their source region, low MgO, Ni and Cr concentrations rule out direct derivation from the mantle wedge. Also, lack of negative Eu anomalies suggests an unfractionated magma and precludes a differentiation from the diorites of mafic body, which show negative Eu anomalies. Their Na enrichments relative to Ca and K are similar to those of Archean tonalites, trondhjemites and granodiorites and Cenozoic adakites. However, they exhibit important geochemical differences from them, including low-Al (<15 wt%) contents

  7. Search for primitive Methanopyrus based on genetic distance between Val- and Ile-tRNA synthetases.

    PubMed

    Yu, Zhiliang; Takai, Ken; Slesarev, Alexei; Xue, Hong; Wong, J Tze-Fei

    2009-10-01

    Since evidence indicates that the Last Universal Common Ancestor (LUCA) was phylogenetically closest to Methanopyrus kandleri among living organisms with elucidated genomes, this study has been directed to a search for the most primitive Methanopyrus lineage. For this purpose, the divergence of valyl-tRNA synthetase (ValRS) and isoleucyl-tRNA synthetase (IleRS) was employed as a measure of primitivity. Comparison of Methanopyrus kandleri and the Methanopyrus isolates GC34 and GC37 from the Pacific Ocean and KOL6, TAG1, TAG11, and SNP6 from the Atlantic Ocean established that the Pacific lineages are more primitive than the Atlantic lineages. Both the groups, however, are younger than environmental genomes from the Kairei Field of Central Indian Ridge in the Indian Ocean. These results showed that different Methanopyrus isolates differ significantly with respect to ValRS-IleRS divergence. On this basis, genomes giving rise to the ValRS and IleRS gene fragments from the Central Indian Ridge represent the most primitive Methanopyrus, phylogenetically the oldest living lineage closest to LUCA. PMID:19841848

  8. Modeling and experimental assessment of a buried Leu-Ile mutation in dengue envelope domain III.

    PubMed

    Kulkarni, Manjiri R; Numoto, Nobutaka; Ito, Nobutoshi; Kuroda, Yutaka

    2016-02-26

    Envelope protein domain III (ED3) of the dengue virus is important for both antibody binding and host cell interaction. Here, we focused on how a L387I mutation in the protein core could take place in DEN4 ED3, but cannot be accommodated in DEN3 ED3 without destabilizing its structure. To this end, we modeled a DEN4_L387I structure using the Penultimate Rotamer Library and taking the DEN4 ED3 main-chain as a fixed template. We found that three out of seven Ile(387) conformers fit in DEN4 ED3 without introducing the severe atomic clashes that are observed when DEN3 serotype's ED3 is used as a template. A more extensive search using 273 side-chain rotamers of the residues surrounding Ile(387) confirmed this prediction. In order to assess the prediction, we determined the crystal structure of DEN4_L387I at 2 Å resolution. Ile(387) indeed adopted one of the three predicted rotamers. Altogether, this study demonstrates that the effects of single mutations are to a large extent successfully predicted by systematically modeling the side-chain structures of the mutated as well as those of its surrounding residues using fixed main-chain structures and assessing inter-atomic steric clashes. More accurate and reliable predictions require considering sub-angstrom main-chain deformation, which remains a challenging task. PMID:26826384

  9. Crust-derived potassic fluid in metamorphic microdiamond

    NASA Astrophysics Data System (ADS)

    Hwang, Shyh-Lung; Shen, Pouyan; Chu, Hao-Tsu; Yui, Tzen-Fu; Liou, Juhn G.; Sobolev, Nikolay V.; Shatsky, Vladislav S.

    2005-03-01

    A highly potassic COH fluid, with dissolved phosphate, chloride and sulfate/sulfide, was identified as nanometer-size inclusions in metamorphic microdiamonds of Kokchetav dolomite marble and garnet-quartz-pyroxene rock using an analytical electron microscope (AEM) coupled with an energy-dispersive X-ray (EDX) spectrometer. This provides a direct piece of evidence for the formation of metamorphic microdiamonds from such a fluid. Although this crust-derived potassic fluid and the associated solid precipitates are in some respects similar to the fluid inclusions in fibrous/cloudy mantle diamonds, distinct chemical differences exist. This potassic COH fluid, in addition, has the potential to trigger high to ultrahigh-K magmatic and K metasomatic processes in mantle.

  10. Repeated shock and thermal metamorphism of the Abernathy meteorite

    NASA Technical Reports Server (NTRS)

    Lambert, P.; Lewis, C.; Moore, C. B.

    1984-01-01

    Based on the example of Abernathy (L6 chondrite), it is shown how petrographic investigation can be used to unravel the nature, chronology and conditions of superposed metamorphic events in chondrites. Features considered include the texture of the rock, optical characteristics of olivine, pyroxene and plagioclase, refractive index of plagioclase, metallographical characteristics and microhardness of Fe-Ni alloys. It is deduced that Abernathy has been involved in at least six metamorphic events since the formation of the chondrite. Four distinct shock events and two separate reheating events have been identified. The chronology of these events is established. The conditions for the last four events are reasonably well constrained. These include severe reheating (T greater than 1200 C); severe shock causing complete melting of plagioclase and local melting of the rock (P between 90 and 110 GPa, T between 1250 and 1350 C); mild shock (P between 10 and 25 GPa, T less than 500 C); and reheating below 800 C.

  11. Replacement textures in CAI and implications regarding planetary metamorphism

    NASA Technical Reports Server (NTRS)

    Meeker, G. P.; Wasserburg, G. J.; Armstrong, J. T.

    1983-01-01

    Formation by a secondary metamorphic event, rather than primary crystallization from a melt or a sequential nebular condensation, is indicated by textural and chemical features of five coarse grained, Ca- and Al-rich inclusions (CAI) from the Allende meteorite which contain embayed pyroxene surrounded by melilite. It is suggested that the most probable environment for a metamorphic process (requiring the addition of Ca derived from calcite or from the introduction of a fluid phase) is that of a small planetary body, rather than the solar nebula. These results are compatible with O isotopic heterogeneities within CAI, and offer a mechanism for the production of lower temperature alteration phases, together with the rim phases found in these inclusions.

  12. Thermal history of chondrites - Hot accretion vs. metamorphic reheating

    NASA Technical Reports Server (NTRS)

    Haack, Henning; Taylor, G. J.; Scott, E. R. D.; Keil, Klaus

    1992-01-01

    The thermal evolution of chondrules is investigated for the stages including primary heating through accretion to parent-body processing to determine whether the chondrules could be hot during accretion. Theoretical attention is given to whether chondrites of different petrologic types could have originated by means of hot accretion or metamorphic reheating. Data are presented from cooling-rate experiments and from calculations of heat retention required for the hot-accretion scenario. The accretion of chondrules hotter than 800 C is shown to be inconsistent with constraints on chondrule thermal evolution, in particular the slow cooling environment of chondrules vs the apparent cooling of chondrites in cold environments. It is argued that petrologic chondrites are formed by cold accretion and subsequently by metamorphic heating.

  13. UHP metamorphism in Greece: Petrologic data from the Rhodope Mountains

    NASA Astrophysics Data System (ADS)

    Baziotis, I. P.; Mposkos, E.; Krohe, A.; Wawrzenitz, N. H.; Liu, Y.; Taylor, L. A.

    2012-12-01

    Metamorphic rocks contain invaluable information for understanding the orogenic mechanisms of a tectonic regime. It is now well recorded and recognized that subduction of oceanic lithosphere and collision of continental blocks can result in sinking of subducted rocks to deeper levels than normal (>100 km). Further, the discovery of coesite and diamond in apparently regionally metamorphosed rocks provoked issues, for returning these rocks to the surface relatively fast, thereby preserving the UHP conditions. These UHPM terrains have been identified in more than twenty provinces worldwide. In Greece, UHPM rocks occur in the Rhodope area, one of the major tectono-metamorphic units located in NE Greece. This region consists of different metamorphic complexes involved in the Alpine collisional history between the Eurasian and African plates (e.g., Krohe & Mposkos, 2002-Geol Soc London Spec Pub, 204, 151). In Rhodope, a Jurassic UHP metamorphism is confirmed in the uppermost Kimi and the underlying Sidironero complexes (Mposkos & Kostopoulos, 2001- EPSL, 192, 497; Perraki et al., 2004-5th ISEMG, T2-35, 2006- EPSL, 241, 672; Liati, 2005- Con Min Pet, 150, 608; Bauer et al., 2007- Lithos, 99, 207). UHP metamorphism is evidenced by the presence of octahedral microdiamond inclusions (3 to 10 μm) in protective garnets, within the metapelitic gneisses. Microdiamonds probably formed from a supercritical fluid under extreme P-T conditions. The latter is strengthened by the presence of composite inclusions consisting of CO2, calcite, and microdiamonds. Other UHP indicators include: 1) quartz rods and rutile needle exsolutions in metapelitic garnet, suggesting a former titaniferous super-silicic (majoritic) garnet formed at P >4GPa; 2) oriented quartz lamellae in eclogitic clinopyroxene having been exsolved from a former super-silicic UHP precursor; and 3) coesite pseudomorphs in garnet, where radial cracks around multi-crystalline-quartz aggregates are indicative of the former

  14. Mobility of gold during metamorphism of the Dalradian in Scotland

    NASA Astrophysics Data System (ADS)

    Pitcairn, I. K.; Skelton, A. D. L.; Wohlgemuth-Ueberwasser, C. C.

    2015-09-01

    Mobility of Au and related metals during metamorphism has been suggested to be the source of metals enriched in orogenic Au deposits. This study investigates the mobility of Au, As, and Sb during metamorphism of the Dalradian metasedimentary rocks of Scotland. The metamorphic processes in the Dalradian of Scotland are extremely well studied, and the terrane is an ideal area to investigate mobility of these metals. Our results show that of the 25 major and trace elements analysed, only Au, As, Sb, S and volatile contents as shown by loss on ignition (LOI) values show systematic variation with the metamorphic grade of the samples. Average Au concentrations decrease from 1.1 ± 0.55 ppb and 0.72 ± 0.34 ppb in chlorite and biotite zone rocks down to 0.4 ± 0.22 ppb and 0.34 ± 0.13 ppb in kyanite and sillimanite zone rocks. Average As concentrations decrease from 4.8 ppm (range 0.5 to 17.8 ppm) and 1.96 ± 1.9 ppm in chlorite and biotite zone rocks down to 0.24 ± 0.15 ppm and 0.2 ± 0.12 ppm in kyanite and sillimanite zone rocks. Average Sb concentrations decrease from 0.18 ± 0.15 ppm and 0.11 ± 0.10 ppm in chlorite and biotite zone rocks down to 0.04 ± 0.02 ppm in both kyanite and sillimanite zone rocks. Sulphur and LOI concentrations also show significant decreases. Mass balance calculations indicate that compared to chlorite and biotite zone samples, sillimanite zone samples have an average mass loss of 62 ± 14%, 94 ± 4% and 74 ± 14% for Au, As, and Sb respectively. Every 1 km3 of chlorite-biotite zone mixed psammitic-pelitic protolith rock that is metamorphosed to sillimanite zone conditions would release 1.5 t Au, 8613 t As, 270 t Sb, and 1.02 Mt S. The mobility of these elements is strongly controlled by the paragenesis of sulphide minerals. Pyrite, sphalerite, galena and cobaltite (as well as gersdorffite) decrease in abundance with increasing metamorphic grade in the Dalradian metasedimentary rocks. A critical aspect of the sulphide paragenesis is the

  15. Tectono-metamorphic processes beneath an obducted ophiolite: evidence from metamorphic soles and accreted units from western Turkey

    NASA Astrophysics Data System (ADS)

    Plunder, A.; Agard, P.; Chopin, C.; Okay, A. I.; Whitechurch, H.

    2015-12-01

    The convergence between the Anatolide Tauride block and Eurasia during Cretaceous times lead to the closure of a branch of the Neotethyan ocean and to ophiolite obduction. After reconstruction, obducted ophiolite and their sub-ophiolitic units can be found along a 200 kilometre-long north to south transect in western Anatolia. If related to a single event, the dimension of this ophiolite makes it an exceptional object of interest to study obduction and early subduction dynamics. This contribution aim to: (1) (re)-appraise the metamorphic pressure-temperature (PT) conditions and evolution of the sub-ophiolitic units of western Anatolia; (2) reconstruct the Anatolian ophiolite and (3) understand the dynamics of a large-scale and long-lived obduction. Directly below the ophiolite (mostly made of mantle-derived rocks) lies a metamorphic sole. The upper part of is this sole is made of garnet ± clinopyroxene amphibolites. In the northern part the sole is characterised by an important blueschist-facies overprint destabilizing the amphibolite paragenesis whereas it is lacking in the south. PT conditions were refined at 10.5 kbar and 780°C for the south and at 11 kbar and 725°C using pseudosection modelling. Field and petrological observations recognize three principal units in the accretionary complex (from top to bottom, OC1, 2 and 3) with PT conditions ranging from incipient metamorphism to blueschist facies conditions. OC1 represents most of the outcropping unit, is found all along the section and shows pristine oceanic rocks to very low grade metamorphics rocks (lawsonite - pumpelltyite facies). Blueschist facies rocks including Fe-Mg carpholite-bearing layers were found in OC2 and attest high-pressure and low-temperature conditions (~10 kbar - 350°C). OC3 exhibit a clear blueschist facies metamorphism, but higher PT conditions (17 kbar - 450°C). Both OC2 and 3 were only found in the northern area close to the suture zone. Combining these data and recent advances

  16. Snow metamorphism as revealed by scanning electron microscopy.

    PubMed

    Dominé, Florent; Lauzier, Thomas; Cabanes, Axel; Legagneux, Loïc; Kuhs, Werner F; Techmer, Kirsten; Heinrichs, Till

    2003-09-01

    Current theories of snow metamorphism indicate that sublimating snow crystals have rounded shapes, while growing crystals have shapes that depend on growth rates. At slow growth rates, crystals are rounded. At moderate rates, they have flat faces with rounded edges. At fast growth rates, crystals have flat faces with sharp edges, and they have hollow faces at very fast growth rates. The main growth/sublimation mechanism is thought to be by the homogeneous nucleation of new layers at or near crystal edges. It was also suggested that the equilibrium shape of snow crystals would be temperature dependent: rounded above -10.5 degrees C, and faceted below. To test these paradigms, we have performed SEM investigations of snow samples having undergone metamorphism under natural conditions, and of snow samples subjected to isothermal metamorphism at -4 degrees and -15 degrees C in the laboratory. In general, current theories predicting crystal shapes as a function of growth rates, and of whether crystals are growing or sublimating, are verified. However, the transition in equilibrium shapes from rounded to faceted at -10.5 degrees C is not observed in our isothermal experiments that reveal a predominance of rounded shapes after more than a month of metamorphism at -4 and -15 degrees C. Some small crystals with flat faces that also have sharp angles at -15 degrees C, are observed in our isothermal experiments. These faces are newly formed, and contradict current theory. Several hypotheses are proposed to explain their occurrence. One is that they are due to sublimation at emerging dislocations. PMID:12938116

  17. Change in the paramagnetic characteristics of coals during metamorphism

    SciTech Connect

    Bineev, E.A.; Peresun'ko, T.F.

    1983-01-01

    The paper studies the paramagnetic properties of deep-mined coals on samples taken from one seam with a wide spectrum of metamorphism. Changes which take place in the concentration of paramagnetic centres within the various types of coal are related to structural and chemical transformations which occur with progressive coalification. Comparisons of EPR and X-ray structural and elementary analyses produce a picture of those particular paramagnetic centres which are responsible for the wide- and narrow-band EPR signals.

  18. Lunar anorthosite 15415 - Texture, mineralogy, and metamorphic history.

    NASA Technical Reports Server (NTRS)

    James, O. B.

    1972-01-01

    Lunar anorthosite 15415 consists almost entirely of anorthite (homogeneous anorthite 96.6 molecule percent), with accessory diopsidic augite and traces of hypersthene, ilmenite, and a silica mineral. The rock has had a complex metamorphic history. The texture reflects at least two episodes of shearing (followed by intense and partial recrystallization, respectively), one episode of cataclastic deformation, and one or more episodes of shattering and fragmentation.

  19. Lunar anorthosite 15415: texture, mineralogy, and metamorphic history.

    PubMed

    James, O B

    1972-01-28

    Lunar anorthosite 15415 consists almost entirely of anorthite (homogeneous anorthite 96.6 molecule percent), with accessory diopsidic augite and traces of hypersthene, ilmenite, and a silica mineral. The rock has had a complex metamorphic history. The texture reflects at least two episodes of shearing (followed by intense and partial recrystallization, respectively), one episode of cataclastic deformation, and one or more episodes of shattering and fragmentation. PMID:17731367

  20. Himalayan inverted metamorphism constrained by oxygen isotope thermometry

    NASA Astrophysics Data System (ADS)

    Vannay, Jean-Claude; Sharp, Zachary D.; Grasemann, Bernhard

    Inverted metamorphic field gradients are preserved in two amphibolite facies metapelitic sequences forming the crystalline core zone of the Himalayan orogen in the Sutlej valley (NW India). In the High Himalayan Crystalline Sequence (HHCS), metamorphic conditions increase upwards from the staurolite zone at the base, through the kyanite-in and sillimanite-in isograds, finally to reach partial melting conditions at the top. The structurally lower Lesser Himalayan Crystalline Sequence (LHCS) shows a gradual superposition of garnet-in, staurolite-in and kyanite+sillimanite-in isograds. Although phase equilibria constraints imply inverted temperature field gradients in both units, garnet-biotite (GARB) rim thermometry indicates final equilibration at a nearly uniform temperature around T 600°C across these sequences. The P-T path and garnet zoning data show that this apparent lack of thermal field gradient is mainly the consequence of a resetting of the GARB equilibria during cooling. In order to constrain peak temperature conditions, 20 samples along the studied section have been analysed for oxygen isotope thermometry. The isotopic fractionations recorded by quartz-garnet and quartz-aluminosilicate mineral pairs indicate temperatures consistent with phase equilibria and P-T path constraints for metamorphic peak conditions. Together with barometry results, based on net transfer continuous reactions, the oxygen isotope thermometry indicates peak conditions characterized by: (1) a temperature increase from T 570 to 750°C at a nearly constant pressure around P 800MPa, from the base to the top of the HHCS unit; (2) a temperature increase from T 610 to 700°C and a pressure decrease from P 900 to 700MPa, from the base to the top of the LHCS metapelites. Oxygen isotope thermometry thus provides the first quantitative data demonstrating that the Himalayan inverted metamorphism can be associated with a complete inversion of the thermal field gradient across the crystalline

  1. Lunar anorthosite 15415: Texture, mineralogy, and metamorphic history

    USGS Publications Warehouse

    James, O.B.

    1972-01-01

    Lunar anorthosite 15415 consists almost entirely of anorthite (homogeneous anorthite 96.6 molecule percent), with accessory diopsidic augite and traces of hypersthene, ilmenite, and a silica mineral. The rock has had a complex metamorphic history. The texture reflects at least two episodes of shearing (followed by intense and partial recrystallization, respectively), one episode of cataclastic deformation, and one or more episodes of shattering and fragmentation.

  2. Penecontemporaneous metamorphism, fragmentation, and reassembly of ordinary chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Grimm, R. E.

    1985-01-01

    The thermal histories of ordinary chondrites and the canonical internal heating or onion shell models, which predict an inverse relation between the petrologic type of chondrites and the metallographic cooling rate, are reviewed. The thermal and accretional requirements of the 'metamorphosed planetesimal' model proposed by Scott and Rajan (1981) are analyzed, and an alternative model consistent with the metallographic cooling rate constraints is suggested in which ordinary chondrite parent bodies are collisionally fragmented and then rapidly reassembled before metamorphic heat has been dissipated.

  3. GSTP1 Ile105Val polymorphism correlates with progression-free survival in MCRC patients treated with or without irinotecan: a study of the Dutch Colorectal Cancer Group

    PubMed Central

    Kweekel, D M; Koopman, M; Antonini, N F; Van der Straaten, T; Nortier, J W R; Gelderblom, H; Punt, C J A; Guchelaar, H-J

    2008-01-01

    A Valine residue at position 105 of the GSTP1 protein results in decreased enzyme activity. As nuclear GSTP1 activity decreases irinotecan cytotoxicity, Val-allele carriers may benefit more from irinotecan chemotherapy. Our aim was to investigate the association of GSTP1 genotype with treatment outcome of irinotecan. Progression-free survival (PFS) and toxicity were determined in 267 metastatic colorectal cancer (MCRC) patients who were treated with first-line capecitabine (CAP) plus irinotecan (CAPIRI), or CAP single agent in a prospective randomised phase III trial (CAIRO). GSTP1 genotype was determined by Pyrosequencing. Patients receiving CAP showed a PFS of 6.6 (Ile/Ile), 6.0 (Ile/Val) and 6.5 months (Val/Val); compared to 7.0 (Ile/Ile), 8.8 (Ile/Val) and 9.2 months (Val/Val) with CAPIRI. Median PFS was 2.7 months longer in Val-allele carriers treated with CAPIRI compared to CAP (P=0.005). Patients with the Ile/Ile genotype showed similar PFS with CAPIRI and CAP (7.0 compared to 6.6 months, P=0.972). Toxicity did not differ significantly among genotypes. GSTP1 codon 105 polymorphism may be predictive for the response to irinotecan-based chemotherapy in patients with MCRC, with the Val-allele being associated with a better outcome. Ile/Ile genotype patients do not appear to benefit from the addition of irinotecan to CAP. PMID:18797455

  4. Seismicity, metamorphism and rheology of the lower continental crust

    NASA Astrophysics Data System (ADS)

    Austrheim, Håkon

    2014-05-01

    Seismological data document that both normal earthquakes and tremors occur in the lower continental crust. Pseudotachylytes (frictional melts and ultracommunited rocks) have been described from several high grade metamorphic terrains and may be the geological manifestation of this seismicity. The Grenville (c. 930Ma) granulite facies complex (T: 800 °C; P: ≤10kbar) of the Lindås Nappe in the Bergen Arcs, W-Norway underwent a fluid induced partial eclogite (T: 600-650 °C; P: 15-20 kbar) and amphibolite facies metamorphism during the Caledonian (c.400-430 Ma) continent collision. Pseudotachylyte fault and injection veins formed in the dry granulites at or close to the reaction fronts both in the eclogitized (western parts) and the amphibolitized (eastern parts) of the Nappe. They are locally recrystalized with the development of amphibolite and eclogite facies assemblages demonstrating that they formed pre or syn the Caledonian metamorphism. The pseudotachylytes transect lithologies ranging from peridotite to anorthosite and consequently the influence of the seismic energy release on a range of granulite facies minerals including garnet, pyroxenes, olivine, plagioclase, hornblende and scapolite can be observed. The seismic energy released promotes the Caledonian metamorphism and change the petrophysical properties of the lower crust in the following ways: The melting and the ultracommunition of the granulite facies minerals increased the reactive surface area and produce local pathways for fluid. S-rich scapolite, a common mineral in granulities play a key role in this process by releasing S and C to form sulfides and carbonates. Small sulfide grains impregnate the pseudotachylyte veins which may lead to an increased electrical conductivity of the deep crust. The pseudotachylyte veins impose inhomogeneities in the massive rocks through grain size reduction and lead to strain localization with development of amphibolite and eclogite facies shear zones. Formation

  5. Metamorphic InAlAs/InGaAs/InAlAs/GaAs HEMT heterostructures containing strained superlattices and inverse steps in the metamorphic buffer

    NASA Astrophysics Data System (ADS)

    Galiev, G. B.; Vasil'evskii, I. S.; Pushkarev, S. S.; Klimov, Е. А.; Imamov, R. M.; Buffat, P. A.; Dwir, B.; Suvorova, Е. I.

    2013-03-01

    Metamorphic InхAl1-хAs buffer design features influence on electrophysical and structural properties of the heterostructures was investigated. Two types of MHEMT heterostructures In0.70Al0.30As/In0.76Ga0.24As with novel design contained inverse steps or strained superlattices were grown by MBE on GaAs substrates. Electrophysical properties of the heterostructures were characterized by Hall measurements, while the structural features were described with the help of different transmission electron microscopy techniques. The metamorphic HEMT with strained superlattices inserted in the metamorphic buffer had the smoother surface and more defect-free crystal structure, as well as a higher Hall mobility, than metamorphic HEMT with inverse steps within the metamorphic buffer.

  6. The role of boron and fluids in high temperature, shallow level metamorphism of the Chugach Metamorphic Complex, Alaska

    NASA Technical Reports Server (NTRS)

    Sisson, V. B.; Leeman, W. P.

    1988-01-01

    The possible role of boron (B) involvement in granite equilibria and generation of melts during crustal metamorphism has been a focus of speculation in recent literature. Most of the evidence for such involvement derives from experimental data which implies that the addition of B will lower the temperature of the granite solidus. Also the presence of tourmaline has a minor effect on the temperature of the solidus. Further indirect evidence that B may be involved in partial melting processes is the observation that granulites are commonly depleted in B, whereas the B content of low grade metapelites can be high (up to 2000 ppm). Researchers' measurements of the whole-rock B contents of granulites from the Madras region, India are low, ranging from 0.4 to 2.6 ppm. Ahmad and Wilson suggest that B was mobilized in the fluid phase during granulite facies metamorphism of the Broken Hill Complex, Australia. Thus, it appears that during the amphibolite to granulite transition, B is systematically lost from metasediments. The B that is released will probably partition into the vapor phase and/or melt phase. Preliminary measurements imply that the boron content of rocks in the Chugach Metamorphic Complex is not sufficient to influence the processes of partial melting at low pressures.

  7. First evidence of the Ellesmerian metamorphism on Svalbard

    NASA Astrophysics Data System (ADS)

    Kośmińska, Karolina; Majka, Jarosław; Manecki, Maciej; Schneider, David A.

    2016-04-01

    The Ellesmerian fold-and-thrust belt is exposed in the High Arctic from Ellesmere Island in the east, through North Greenland, to Svalbard in the west (e.g. Piepjohn et al., 2015). It developed during Late Devonian - Early Carboniferous, and overprinted older (mainly Caledonian) structures. It is thought that this fold-and-thrust belt was formed due to collision of the Pearya Terrane and Svalbard with the Franklinian Basin of Laurentia. Traditionally, the Ellesmerian fold-and-thrust belt comprises a passive continental margin affected by foreland deformation processes, but the exact larger scale tectonic context of this belt is disputable. It is partly because the Eocene Eurekan deformation superimposed significantly the Ellesmerian structures, thus making the reconstruction of the pre-Eurekan history very difficult. Here we present for the first time evidence for Ellesmerian metamorphism within the crystalline basement of Svalbard. These rocks are exposed in the Pinkie unit on Prins Karls Forland (W-Svalbard), which exhibits tectonic contacts with the overlying sequences. The Pinkie unit is mainly composed of strongly deformed lithologies such as laminated quartzites, siliciclastic rocks and garnet-bearing mica schists. Detrital zircon dating yielded ages as young as Neoproterozoic (0.95-1.05 Ga), thus the Pinkie unit is considered to be Neoproterozoic (Kośmińska et al., 2015a). The M1 assemblages and D1 structures are affected by D2 mylonitization (cf. Faehnrich et al., 2016, this meeting). Petrological characterization and Th-U-total Pb chemical monazite dating have been performed on the Pinkie metapelites. These rocks exhibit an apparent inverted Barrovian metamorphic sequence, within which three metamorphic zones have been distinguished: garnet+staurolite+muscovite+biotite, garnet+staurolite+kyanite+muscovite+biotite, garnet+kyanite+muscovite+biotite. The P-T estimates using the QuiG barometry coupled with thermodynamic modelling revealed that the

  8. From intra-oceanic subduction to arc accretion and oblique arc-continent collision: Insights from the P-T-D-t path of the southern Río San Juan metamorphic complex, northern Dominican Republic

    NASA Astrophysics Data System (ADS)

    Escuder-Viruete, J.; Valverde-Vaquero, P.; Rojas-Agramonte, Y.; Gabites, J.; Pérez-Estaún, A.

    2012-04-01

    +zoisite-bearing felsic melts exhibit a positive Ce anomaly relative to chondrite, an overall flat HREE pattern, and no significant negative Eu anomaly, which provide evidence for zircon growth under eclogite facies conditions. Structural and sedimentary data confirm the existence of a regional, Late Oligocene to Miocene contractional event in the complex (D3), as well as two additional late brittle deformations (D4 and D5). The compilation of this pressure-temperature-deformation-time path supports that an early subduction-related D1 deformation and high-P M1 metamorphism, was followed by a D2 extensional shearing deformation and M2 retrograde decompression, at exhumation rates of 3-4 km/Ma. The dominant tectonic mechanism responsible for exhumation of high-P rocks in the Cuaba Unit was therefore the D2 extensional tectonics, which caused tectonic juxtaposition and local metamorphic pressure gaps within the structural pile. This P-T-D-t evolution indicates that the Cuaba Unit experienced initial subduction, subsequent underplating below the forearc wedge of an island-arc, and final exhumation in the accretionary prism. At the regional scale, the Cuaba unit could be a fragment of the proto-Pacific arc that collided and was accreted bellow the E-facing, intra-oceanic, Caribbean island-arc, prior to final oblique collision with the paleo-continental margin of North America.

  9. Syn-extensional plutonism and peak metamorphism in the albion-raft river-grouse creek metamorphic core complex

    USGS Publications Warehouse

    Strickland, A.; Miller, E.L.; Wooden, J.L.; Kozdon, R.; Valley, J.W.

    2011-01-01

    The Cassia plutonic complex (CPC) is a group of variably deformed, Oligocene granitic plutons exposed in the lower plate of the Albion-Raft River- Grouse Creek (ARG) metamorphic core complex of Idaho and Utah. The plutons range from granodiorite to garnet-bearing, leucogranite, and during intrusion, sillimanite- grade peak metamorphism and ductile attenuation occurred in the country rocks and normal-sense, amphibolite-grade deformation took place along the Middle Mountain shear zone. U-Pb zircon geochronology from three variably deformed plutons exposed in the lower plate of the ARG metamorphic core complex revealed that each zircon is comprised of inherited cores (dominantly late Archean) and Oligocene igneous overgrowths. Within each pluton, a spread of concordant ages from the Oligocene zircon overgrowths is interpreted as zircon recycling within a long-lived magmatic system. The plutons of the CPC have very low negative whole rock ??Nd values of -26 to -35, and initial Sr values of 0.714 to 0.718, consistent with an ancient, crustal source. Oxygen isotope ratios of the Oligocene zircon overgrowths from the CPC have an average ??18O value of 5.40 ?? 0.63 permil (2SD, n = 65) with a slight trend towards higher ??18O values through time. The ??18O values of the inherited cores of the zircons are more variable at 5.93 ?? 1.51 permil (2SD, n = 29). Therefore, we interpret the plutons of the CPC as derived, at least in part, from melting Archean crust based on the isotope geochemistry. In situ partial melting of the exposed Archean basement that was intruded by the Oligocene plutons of the CPC is excluded as the source for the CPC based on field relationships, age and geochemistry. Correlations between Ti and Hf concentrations in zircons from the CPC suggest that the magmatic system may have become hotter (higher Ti concentration in zircon) and less evolved (lower Hf in zircon concentration) through time. Therefore, the CPC represents prolonged or episodic magmatism

  10. Quantitative determination of metamorphic reaction history : mass balance relations between groundmass and mineral inclusion assemblages in metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Whitney, Donna L.; Lang, Helen M.; Ghent, Edward D.

    1995-07-01

    Qualitative and quantitative information about metamorphic reaction history and PT paths may be obtained from mineral inclusions in garnet by comparing the mineralogy, distribution, and compositions of paragenetically-related inclusions with minerals in the groundmass assemblage. Using the algebraic technique of singular value decomposition (SVD), we document mass balance relations between inclusion and groundmass assemblages in metapelitic rocks from two metamorphic terranes that experienced different peak metamorphic conditions, and whose transition from inclusion to groundmass assemblage records different PT path segments relative to peak conditions. We calculate mass balances relating an inclusion assemblage consisting in part of armored relics of chloritoid to groundmass mineral assemblages in a kyanite-staurolite mica schist from the Solitude Range, British Columbia, and an inclusion assemblage of kyanite, staurolite, and rutile to groundmass minerals in a sillimanite-cordierite gneiss from the Skagit Gneiss, North Cascade Range, Washington. Mass balances for each rock are consistent with reaction histories inferred from petrographic observations. In the Solitude Range schist, the results of mass balance calculations are consistent with the growth of staurolite and garnet at the expense of chloritoid during prograde metamorphism and suggest that chlorite, although not preserved as an inclusion, was involved in initial staurolite growth. In the Skagit sillimanite gneiss, mass balance relations exist between the inclusion suite, which formed during high pressure metamorphism, and the associated groundmass assemblage, which equilibrated at high temperature but much lower pressure. Mass balance does not exist between the groundmass of the Skagit sillimanite gneiss and the groundmass of a nearby kyanite-staurolite schist that has been proposed as a possible lower-grade equivalent of the sillimanite-bearing rocks. These results indicate that, although compositional

  11. Coal metamorphism in the upper portion of the Pennsylvanian Sturgis Formation in Western Kentucky

    SciTech Connect

    Hower, J.C.

    1983-12-01

    Coals from the Pennsylvanian upper Sturgis Formation (Mississippian and Virginian) were sampled from a borehole in Union County, western Kentucky. The coals exhibited two discrete levels of metamorphism. The lower rank coals of high-volatile C bituminous rank were assumed to represent the normal level of metamorphism. A second set of coals of high-volatile A bituminous rank was found to be associated with sphalerite, chlorite, and twinned calcite. The latter mineral assemblages indicate that hydrothermal metamorphism was responsible for the anomalous high rank. Consideration of the sphalerite fluid-inclusion temperatures from nearby ores and coals and the time - temperature aspects of the coal metamorphism suggests that the hydrothermal metamorphic event was in the 150 to 200 C range for a brief time (10/sup 5/-10/sup 5/and yr), as opposed to the longer term (25-50m yr) 60 to 75 C ambient metamorphism.

  12. The prevalence and intensity of gastrointestinal parasites of dogs in Ile-Ife, Nigeria.

    PubMed

    Sowemimo, Oluyomi A

    2009-03-01

    A study of gastrointestinal parasites in 269 faecal samples from dogs (Canis familiaris) collected from Ile-Ife, Nigeria between January and December 2004, revealed seven helminth species: Toxocara canis 33.8%, Ancylostoma sp. 34.6%, Toxascaris leonina 3.3%, Trichuris vulpis 3.7%, Dipylidium caninum 4.1%, Uncinaria stenocephala 0.7% and Taenia sp. 1.1%. The faecal egg intensities, determined as mean eggs per gram of faeces ( +/- SEM) were: T. canis 393.8 +/- 83.4, Ancylostoma sp. 101.5 +/- 32.8, T. leonina 14.3 +/- 7.9, T. vulpis 3.4 +/- 1.5, D. caninum 2.2 +/- 0.8, U. stenocephala 0.2 +/- 0.2. The prevalence of intestinal parasites was significantly higher (P < 0.05) in dogs of age 0-6 months than in older age groups. There was no significance difference in overall prevalence of intestinal helminth parasites between male (58.3%) and female (50.0%) dogs (P>0.05). The prevalence of helminth parasites was significantly higher (P < 0.05) in free-ranging than in kennelled dogs. The prevalence of helminth parasites was also significantly higher (P < 0.05) in African shepherds than in Alsatians and other exotic breeds. Each helminth parasite had similar prevalences and intensities among both genders (P>0.05) except in T. vulpis. The overall prevalence of intestinal parasites may continue to rise due to lack of functional veterinary clinics for dog care in Ile-Ife. Therefore, there is the need to establish a veterinary facility in Ile-Ife. PMID:18838021

  13. Structure of the Val122Ile variant transthyretin - a cardiomyopathic mutant.

    PubMed

    Damas, A M; Ribeiro, S; Lamzin, V S; Palha, J A; Saraiva, M J

    1996-09-01

    The Val122Ile mutant transthyretin (TTR Ile122) is an amyloidogenic protein which has been described as the major protein component of amyloid fibrils isolated from patients with familial amyloidotic cardiomyopathy (FAC), a disease characterized by cardiac failure and amyloid deposits in the heart. The reasons for the deposition of TTR are still unknown and it is conceivable that a conformational alteration, resulting from the mutation, is fundamental for amyloid formation. The three-dimensional structure of TTR Ile122 was determined and refined to a crystallographic R factor of 15.8% at 1.9 A resolution. The r.m.s. deviation from ideality in bond distances is 0.019 A and in angle-bonded distances is 0.027 A. The presence of two crystallographically independent monomers in the asymmetric unit allowed additional means of estimation of atomic coordinate error. The structure of the mutant is essentially identical to that of the wild-type transthyretin (TTR). The largest deviations occur in surface loops and in the region of the substitution. The protein is a tetramer composed of identical subunits; each monomer has two four-stranded beta-sheets which are extended to eight-stranded beta-sheets when two monomers associate through hydrogen bonds forming a dimer, which is the crystallographic asymmetric unit. The replacement of valine for isoleucine introduces very small alterations in relation to the wild-type protein; nevertheless they seem to confirm a tendency for a less stable tetrameric structure. This would support the idea that the tetrameric structure might be disrupted in amyloid fibrils. PMID:15299606

  14. Numerical Simulation of Regional and Contact Metamorphism Using the Macintosh Microcomputer.

    ERIC Educational Resources Information Center

    Peacock, Simon Muir

    1990-01-01

    Described is a set of FORTRAN programs, suitable for teaching and research purposes, that simulate contact and regional metamorphism. Equations, examples, program uses, and availability are discussed. (CW)

  15. Raman-based geobarometry of ultrahigh-pressure metamorphic rocks: applications, problems, and perspectives.

    PubMed

    Korsakov, Andrey V; Zhukov, Vladimir P; Vandenabeele, Peter

    2010-08-01

    Raman-based geobarometry has recently become increasingly popular because it is an elegant way to obtain information on peak metamorphic conditions or the entire pressure-temperature-time (P-T-t) path of metamorphic rocks, especially those formed under ultrahigh-pressure (UHP) conditions. However, several problems need to be solved to get reliable estimates of metamorphic conditions. In this paper we present some examples of difficulties which can arise during the Raman spectroscopy study of solid inclusions from ultrahigh-pressure metamorphic rocks. PMID:20582407

  16. Metamorphism of tectonic terranes in the eastern marginal zone of the Appalachian orogen, New England

    SciTech Connect

    Hepburn, J.C.; Olszewski, W.J.; Guidotti, C.V.

    1985-01-01

    Southeastern New England is subdivided into three major fault bounded tectonic terranes, each with a distinctive metamorphic history. The easternmost, the Avalon Terrane, has generally been metamorphosed no higher than the lower greenschist facies. Evidence for pre-Alleghanian metamorphism includes a Proterozoic Z(.) event, contact metamorphism adjacent to Ord.-Dev. alkaline plutons, and granulite facies crustal xenoliths in Mesozoic dikes. To the west the Nashoba Terrane has been deformed and polymetamorphosed to the sill. and 2nd sill. zones between approximately 415 and 450 m.y., based on ages of associated granitic and migmatitic rocks. 730 m.y. assumed basement gneisses (fish Brook) have likely experienced Late PC metamorphism. In the Merrimack Trough, here including the Massabesic Gneiss, the metamorphic grade ranges from the greenschist facies on the east to the 2nd sillimanite zones on the west toward the Massabesic. The two metamorphic events present here must predate the intrusion of the Exeter Diorite (473 m.y .), indicating one or both may be PC. To the east, the fault bounded Rye Formation has also experienced two pre- 470 m.y. metamorphisms (and -sill.) However, the terrane east of the Turtle Head Fault Zone (THFZ) has many similarities to the Boston Platform including general (Late PC.) lower greenschist metamorphism. Also, the area between the Norumbega FZ and the THFZ has experienced high grade metamorphism of probable Silurian age and thus may be similar to the Nashoba Terrane.

  17. Early Tertiary Anaconda metamorphic core complex, southwestern Montana

    USGS Publications Warehouse

    O'Neill, J. M.; Lonn, J.D.; Lageson, D.R.; Kunk, M.J.

    2004-01-01

    A sinuous zone of gently southeast-dipping low-angle Tertiary normal faults is exposed for 100 km along the eastern margins of the Anaconda and Flint Creek ranges in southwest Montana. Faults in the zone variously place Mesoproterozoic through Paleozoic sedimentary rocks on younger Tertiary granitic rocks or on sedimentary rocks older than the overlying detached rocks. Lower plate rocks are lineated and mylonitic at the main fault and, below the mylonitic front, are cut by mylonitic mesoscopic to microscopic shear zones. The upper plate consists of an imbricate stack of younger-on-older sedimentary rocks that are locally mylonitic at the main, lowermost detachment fault but are characteristically strongly brecciated or broken. Kinematic indicators in the lineated mylonite indicate tectonic transport to the east-southeast. Syntectonic sedimentary breccia and coarse conglomerate derived solely from upper plate rocks were deposited locally on top of hanging-wall rocks in low-lying areas between fault blocks and breccia zones. Muscovite occurs locally as mica fish in mylonitic quartzites at or near the main detachment. The 40Ar/39Ar age spectrum obtained from muscovite in one mylonitic quartzite yielded an age of 47.2 + 0.14 Ma, interpreted to be the age of mylonitization. The fault zone is interpreted as a detachment fault that bounds a metamorphic core complex, here termed the Anaconda metamorphic core complex, similar in age and character to the Bitterroot mylonite that bounds the Bitterroot metamorphic core complex along the Idaho-Montana state line 100 km to the west. The Bitterroot and Anaconda core complexes are likely components of a continuous, tectonically integrated system. Recognition of this core complex expands the region of known early Tertiary brittle-ductile crustal extension eastward into areas of profound Late Cretaceous contractile deformation characterized by complex structural interactions between the overthrust belt and Laramide basement uplifts

  18. Distribution of Water in Nominally Anhydrous Minerals during Metamorphic Reactions

    NASA Astrophysics Data System (ADS)

    Van Lankvelt, A.; Seaman, S. J.; Williams, M. L.

    2014-12-01

    Nominally anhydrous minerals are a reservoir for water in otherwise dry rocks. This water may play a role in facilitating metamorphic reactions and enhancing deformation. In this study, we examined orthopyroxene-bearing granites from the Athabasca Granulite terrane in northern Saskatchewan. These rocks intruded the lower crust (pressures of 1 GPa) at circa 2.6 Ga at temperatures of > 900 ºC and were subsequently metamorphosed at granulite facies conditions (700 ºC and 1 GPa) in the Paleoproterozoic (Williams et al., 2000). One of the primary reactions recorded by these rocks is locally known as the "Mary" reaction and involves the anhydrous reaction: orthopyroxene + Ca-plagioclase = clinopyroxene + garnet + Na-plagioclase. Measurements of water concentrations in both product and reactant assemblages were performed using a Bruker Vertex 70 Fourier transform infrared spectrometer and revealed that there is a slight excess of water in product minerals over reactant minerals. There are two possible explanations for this. The first is that water was derived from an external source, possibly hydrous, likely contemporaneous, mafic dikes. This interpretation is supported by higher concentrations of K, which is essentially absent from the reactant minerals, in the Na-rich rims of plagioclase. However, only modest amounts of external fluids could have been introduced, or amphiboles would have been stabilized at the expense of clinopyroxene (Moore & Carmichael, 1998). An alternative interpretation is that slightly more water-rich minerals reacted more readily, releasing water that was then incorporated into their products, whereas the water-poorer minerals failed to react. Support for this interpretation comes from very low water concentrations in orthopyroxene and plagioclase from an unreacted and undeformed sample. This interpretation suggests that water in anhydrous minerals may catalyze metamorphic reactions, and a lack of water may be critical for preserving metastable

  19. Inventory of echinoderms in the Iles Eparses (Europa, Glorieuses, Juan de Nova), Mozambique Channel, France

    NASA Astrophysics Data System (ADS)

    Conand, C.; Mulochau, T.; Stöhr, S.; Eléaume, M.; Chabanet, P.

    2016-04-01

    The multidisciplinary programme BioReCIE (Biodiversity, Resources and Conservation of coral reefs at Eparses Is.) inventoried multiple marine animal groups in order to provide information on the coral reef health of the Iles Eparses. All five classes of echinoderms were observed by visual census, photographed and later identified. About 100 species are reported, including a few unidentified ones which require further studies. The Holothuroidea and Ophiuroidea are the most diverse. One new species, the asterinid Aquilonastra chantalae O'Loughlin and McKenzie (2013), was discovered in addition to several new records of echinoderms. The illegal fishery targeting holothurians, which are presently highly valuable resources in this zone, is discussed.

  20. Inclusion body myositis, muscle blood vessel and cardiac amyloidosis, and transthyretin Val122Ile allele.

    PubMed

    Askanas, V; Engel, W K; Alvarez, R B; Frangione, B; Ghiso, J; Vidal, R

    2000-04-01

    Typical of sporadic inclusion body myositis muscle biopsies are vacuolated muscle fibers containing intracellular amyloid deposits and accumulations of "Alzheimer-characteristic" proteins. There is no muscle blood vessel or cardiac amyloidosis. We report on a 70-year-old African-American man homozygous for the transthyretin Val122Ile allele who has both sporadic inclusion body myositis and cardiac amyloidosis. His unique pathological features included transthyretin immunoreactivity in prominent muscle blood vessel amyloid and congophilic amyloid deposits within vacuolated muscle fibers. PMID:10762172

  1. Chlorine Behavior in Metasedimentary Rocks during Subduction Zone Metamorphism

    NASA Astrophysics Data System (ADS)

    Barnes, J.; Selverstone, J.; Bebout, G. E.; Penniston-Dorland, S.

    2014-12-01

    Chlorine concentrations and isotopic compositions were measured in two well-characterized metasedimentary suites from the Catalina Schist and the Western Alps to determine Cl behavior during prograde metamorphism. The Catalina Schist is a subduction zone metamorphic complex in California, USA containing lawsonite-albite (LA) to amphibolite grade rocks recording temperatures of 350 to 750°C and depths of 15 to 45 km. Previous work has shown a decrease in N, B, Cs, As, and Sb concentrations from the LA to the epidote-blueschist facies, with relatively little loss at higher metametamorphic grade [1], and limited Li loss across all grades [2]. Metapelitic rocks from the Western Alps (Schistes Lustres and Lago di Cignana) record temperatures of 350 to 550°C and depths up to 90 km. In contrast to Catalina, N, B, Cs, Ba, and Rb concentrations are relatively uniform across grade [3]. In the Catalina Schist, Cl concentration shows a pattern of loss similar to B and N, from ~100-500 ppm Cl in the LA facies to ~100 ppm in the lawsonite-blueschist facies to relatively uniform concentrations of ~10-25 ppm at higher grades. This loss is likely not due to the breakdown of apatite as P2O5 concentrations remain constant across grade. In the Alps, Cl concentrations are overall lower and show moderate loss from ~10 ppm in the lowest grade to <5 ppm in the highest grade. δ37Cl values range from -1 to +1.6‰ and -1.7 to -0.7‰ in Catalina and the Alps, respectively. Both suites show significant isotopic heterogeneities within a single metamorphic grade and no systematic change in δ37Cl value with increasing grade. We interpret these heterogeneities to be inherited from the protolith. Despite large Cl losses, limited Cl isotope fractionation at high temperatures minimizes variations in δ37Cl value with increasing metamorphic grade. [1] Bebout et al, 1999, EPSL, 171, 53-81 [2] Penniston-Dorland et al, 2012, GCA, 77, 530-545 [3] Bebout et al, 2013, Chem Geol, 342, 1-20

  2. Metamorphic grade of organic matter in six unequilibrated ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Quirico, E.; Raynal, P. I.; Bourot-Denise, M.

    2003-05-01

    The thermal metamorphism grade of organic matter (OM) trapped in 6 unequilibrated ordinary chondrites (UOCs) (Semarkona [LL 3.0], Bishunpur [L/LL 3.1], Krymka [LL 3.1], Chainpur [LL 3.4], Inman [L/LL 3.4], and Tieschitz [H/L 3.6]) has been investigated with Raman spectroscopy in the region of the first-order carbon bands. The carbonaceous chondrite Renazzo (CR2) was also investigated and used as a reference object for comparison, owing to the fact that previous studies pointed to the OM in this meteorite as being the most pristine among all chondrites. The results show that the OM thermal metamorphic grade: 1) follows the hierarchy Renazzo << Semarkona << other UOCs; 2) is well correlated to the petrographic type of the studied objects; and 3) is also well correlated with the isotopic enrichment 15N. These results are strikingly consistent with earlier cosmochemical studies, in particular, the scenario proposed by Alexander et al. (1998). Thermal metamorphism in the parent body appears as the main evolution process of OM in UOCs, demonstrating that nebular heating was extremely weak and that OM burial results in the destabilization of an initial isotopic composition with high D and 15N. Furthermore, the clear discrimination between Renazzo, Semarkona, and other UOCs shows: 1) Semarkona is a very peculiar UOC--by far the most pristine; and 2) Raman spectroscopy is a valid and valuable tool for deriving petrographic sub-types (especially the low ones) that should be used in the future to complement current techniques. We compare our results with other current techniques, namely, induced thermo-luminescence and opaques petrography. Other results have been obtained. First, humic coals are not strictly valid standard materials for meteoritic OM but are helpful in the study of evolutionary trends due to thermal metamorphism. Second, terrestrial weathering has a huge effect on OM structure, particularly in Inman, which is a find. Finally, the earlier statement that fine

  3. Proterozoic metamorphism in the Neoarchean Kabul Block, Afghanistan

    NASA Astrophysics Data System (ADS)

    Collett, Stephen; Wali Faryad, Shah

    2015-04-01

    The Kabul Block is an elongate crustal fragment that is situated within a tectonic zone known as the Afghan Central Blocks, which form at the triple junction between the Indian, Eurasian, and Arabian plates. Unique amongst the Afghan Central Blocks, the Kabul Block contains quantifiably Precambrian basement rocks. Recent U/Pb SHRIMP analysis of zircons from the lowermost basement formations (the Sherdarwaza and Khair Khana) indicated the presence of a small Neoarchean component (~2700 Ma), while the majority of zircon cores yielded ages of 2200-2500 Ma. The Sherdarwaza and Khair Khana Formations consist predominantly of migmatites and orthogneisses that reached granulite-facies conditions. Conventional geothermobarometry and phase equilibria modelling on well preserved granulite-facies assemblages indicate that the rocks reached peak conditions in excess of 850°C and up to 7 kbar. U/Pb SHRIMP dating of zircon rims in addition to Th/U dating of monazite inclusions in garnet suggest that this event occurred in the late Paleoproterozoic (1800-1900 Ma). The granulite-facies assemblages are overprinted by a younger amphibolite-facies metamorphism, and are unconformably overlain by amphibolite-facies rocks belonging to younger formations (the Kharog and Welayati) that lack paragenetic evidence for a preceding high-grade metamorphism. The Welayati formation crops-out extensively in the south of Kabul City and consists of a variety of mica-schists and garnet-amphibolites, which contain textural relations suitable for the construction of a pressure-temperature (P-T) path. Inclusion assemblages in porphyroblastic garnet yield P-T conditions of around 525°C and 6 kbar. Chemical zonation in the garnet and phase equilibria modelling indicates that from this point garnet grew during a pressure increase of ~3.5 kbar over a temperature increase of ~125°C. A subsequent period of near isothermal decompression over ~2 kbar is confirmed by the growth of plagioclase, kyanite, and

  4. Shock Metamorphism of the Dhofar 378 Basaltic Shergottite

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; McKay, G.

    2006-01-01

    Shock metamorphism is one of the most fundamental processes in the history of Martian meteorites, especially shergottites, which affect their mineralogy and chronology. The formation of "maskelynite" from plagioclase and shock melts is such major mineralogical effects. Dhofar 378 is one of the recently found desert shergottites that is mainly composed of plagioclase and pyroxene. This shergottite is important because of its highly shocked nature and unique plagioclase texture, and thus has a great potential for assessing a "shock" age of shergottites. We have been working on a combined study of mineralogy and chronology of the same rock chip of Dhofar 378. This abstract reports its mineralogical part.

  5. Grain metamorphism in polar nitrogen ice on Triton

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Mckay, Christopher P.; Pollack, James B.; Cruikshank, Dale P.

    1989-01-01

    The rate of nitrogen grain growth on putative N2-rich polar caps on Triton is calculated. For most plausible assumptions of independent variables, mean grain sizes in polar N2 are meter-scale. Triton's polar caps should constitute the definitive solar-system test bed for the process of ice grain metamorphism. Interpretation of data already in hand may require long path length through condensed N2, possibly due to grain growth. Upcoming Voyager data may clarify the situation, although possible complications in detecting a glaze of N2 ice exist.

  6. Metamorphism and aqueous alteration in low petrographic type ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Xie, T.; Lipschutz, M. E.; Sears, D. W. G.; Guimon, R. K.; Jie, Lu; Benoit, P. H.; O'D. Alexander, C. M.; Wright, Ian; Pillinger, C.; Morse, A. D.; Hutchison, Robert

    1995-01-01

    In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondruies, chondruies were hand-picked from the Semarkona (petrographic type 3.0), Bishunpur (3. 1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron-microprobe and radiochemical neutron activation and the water and H-isotopic composition determined. The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to approx. 8000% SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work. With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondruies, indicating metamorphism-related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak

  7. Evidence and implications of shock metamorphism in lunar samples.

    PubMed

    Short, N M

    1970-01-30

    Lunar microbreccias and loose regolith materials contain abundant evidence of shock metamorphism related to crater-forming meteorite impacts. Diagnostic shock effects include (i) planar features in a silica phase and feldspars, and lamellae in clinopyroxene, (ii) thetomorphic feldspar glass, (iii) heterogeneous glasses of rock and mineral composition, (iv) distinctive recrystallization textures, and (v) characteristic changes in crystal structure as indicated by x-ray diffraction analysis and measurements of refractive index. The microbreccias are produced from regolith materials (ejected fromz craters) by shock lithification. Some feldsparrich fragments may represent ejecta introduced from nonlocal sources, such as the lunar highlands. PMID:17781541

  8. Teaching Igneous and Metamorphic Petrology Through Guided Inquiry Projects

    NASA Astrophysics Data System (ADS)

    McMillan, N. J.

    2003-12-01

    Undergraduate Petrology at New Mexico State University (GEOL 399) has been taught using three, 5-6 week long projects in place of lectures, lab, and exams for the last six years. Reasons for changing from the traditional format include: 1) to move the focus from identification and memorization to petrologic thinking; 2) the need for undergraduate students to apply basic chemical, structural, and field concepts to igneous and metamorphic rocks; 3) student boredom in the traditional mode by the topic that has captivated my professional life, in spite of my best efforts to offer thrilling lectures, problems, and labs. The course has three guided inquiry projects: volcanic, plutonic, and pelitic dynamothermal. Two of the rock suites are investigated during field trips. Each project provides hand samples and thin sections; the igneous projects also include whole-rock major and trace element data. Students write a scientific paper that classifies and describes the rocks, describes the data (mineralogical and geochemical), and uses data to interpret parameters such as tectonic setting, igneous processes, relationship to phase diagrams, geologic history, metamorphic grade, metamorphic facies, and polymetamorphic history. Students use the text as a major resource for self-learning; mini-lectures on pertinent topics are presented when needed by the majority of students. Project scores include evaluation of small parts of the paper due each Friday and participation in peer review as well as the final report. I have found that petrology is much more fun, although more difficult, to teach using this method. It is challenging to be totally prepared for class because students are working at different speeds on different levels on different aspects of the project. Students enjoy the course, especially the opportunity to engage in scientific investigation and debate. A significant flaw in this course is that students see fewer rocks and have less experience in rock classification

  9. Semantically Enabling Knowledge Representation of Metamorphic Petrology Data

    NASA Astrophysics Data System (ADS)

    West, P.; Fox, P. A.; Spear, F. S.; Adali, S.; Nguyen, C.; Hallett, B. W.; Horkley, L. K.

    2012-12-01

    More and more metamorphic petrology data is being collected around the world, and is now being organized together into different virtual data portals by means of virtual organizations. For example, there is the virtual data portal Petrological Database (PetDB, http://www.petdb.org) of the Ocean Floor that is organizing scientific information about geochemical data of ocean floor igneous and metamorphic rocks; and also The Metamorphic Petrology Database (MetPetDB, http://metpetdb.rpi.edu) that is being created by a global community of metamorphic petrologists in collaboration with software engineers and data managers at Rensselaer Polytechnic Institute. The current focus is to provide the ability for scientists and researchers to register their data and search the databases for information regarding sample collections. What we present here is the next step in evolution of the MetPetDB portal, utilizing semantically enabled features such as discovery, data casting, faceted search, knowledge representation, and linked data as well as organizing information about the community and collaboration within the virtual community itself. We take the information that is currently represented in a relational database and make it available through web services, SPARQL endpoints, semantic and triple-stores where inferencing is enabled. We will be leveraging research that has taken place in virtual observatories, such as the Virtual Solar Terrestrial Observatory (VSTO) and the Biological and Chemical Oceanography Data Management Office (BCO-DMO); vocabulary work done in various communities such as Observations and Measurements (ISO 19156), FOAF (Friend of a Friend), Bibo (Bibliography Ontology), and domain specific ontologies; enabling provenance traces of samples and subsamples using the different provenance ontologies; and providing the much needed linking of data from the various research organizations into a common, collaborative virtual observatory. In addition to better

  10. Metamorphism of basic and pelitic rocks at Sulitjelma, Norway

    NASA Astrophysics Data System (ADS)

    Boyle, Alan P.

    1986-06-01

    The Sulitjelma area of the Scandinavian Caledonides consists of a variety of metasedimantary units with small basic intrusions, and a large ophiolitic complex of predominantly basic composition. All units underwent prograde greenschist facies to amphibolite facies regional metamorphism during the Scandinavian phase of the Caledonian orogeny. The resultant mineral assemblages and relationships are consistent with the presence of a miscibility gap in the actinolite-hornblende series under greenschist facies conditions; a garnet forming reaction in pelites involving the consumption of carbonate in order to produe the observed grossular content; some conflict between low-baric and medium-baric pressure estimates from equilibria involving Ca amphibole bearing assemblages in metabasites.

  11. Nanoscale transient porosity controls large-scale metamorphic fluid flow

    NASA Astrophysics Data System (ADS)

    Plümper, Oliver; Botan, Alexandru; Los, Catharina; Malthe-Sørenssen, Anders; Jamtveit, Bjørn

    2016-04-01

    The reaction of fluids with rocks is fundamental for Earth's dynamics as they facilitate heat/mass transfer and induce volume changes, weaknesses and instabilities in rock masses that localize deformation enabling tectonic responses to plate motion. During these fluid-rock interactions it is the ability of a rock to transmit fluid, its permeability, that controls the rates of metamorphic reactions. However, although some geological environments (e.g., sediments) are open to fluids, the majority of solid rocks (e.g., granites, elcogites, peridotites, etc.) are nearly impermeable. Surprisingly though, even in rocks that are nominally impermeable widespread fluid-rock interactions are observed leading to the question: How can fluids migrate through vast amounts of nominally impermeable rocks? Here we investigate one of the most wide-spread fluid-mediated metamorphic processes in the Earth's crust, the albitization of feldspatic rocks. We show that fluid flow and element mobilization during albitization is controlled by an interaction between grain boundary diffusion and reaction front migration through an interface-coupled dissolution-precipitation process. Using a combination of focused ion beam scanning electron microscopy (FIB-SEM)-assisted nanotomography combined with transmission electron microscopy (TEM) reveals that the porosity is dictated by pore channels with a pore diameter ranging between 10 to 100 nm. Three-dimensional visualization of the feldspar pore network reveals that the pore channels must have been connected during the replacement reaction. Analysis of the pore aspect ratios suggests that a Rayleigh-Taylor-type instability associated to surface energy minimization caused the disconnection of the pore channels. Fluid transport in nanometer-sized objects with at least one characteristic dimension below 100 nm enables the occurrence of physical phenomena that are impossible at bigger length scales. Thus, on the basis of our microstructural

  12. Association between GSTP1 Ile105Val polymorphism and urinary system cancer risk: evidence from 51 studies.

    PubMed

    Zhang, Yixiang; Yuan, Yeqing; Chen, Yufang; Wang, Zhao; Li, Fangfang; Zhao, Qingsong

    2016-01-01

    The GSTP1 gene plays an important role in detoxification of carcinogens. GSTP1 gene polymorphisms may alter the susceptibility of urinary system cancer. Numerous studies have been performed to investigate the association between GSTP1 Ile105Val (rs1695 A>G) polymorphism and urinary system cancer risk. Nevertheless, the results remain controversial and only prostate cancer and bladder cancer are covered. We identified eligible studies from PubMed, Elsevier, and three equivalent Chinese databases including the Chinese National Knowledge Infrastructure, Wanfang, and Weipu. Pooled odds ratios and 95% confidence intervals were used to assess the strength of the association between GSTP1 Ile105Val polymorphism and urinary system cancer risk. In total, 11,762 cases and 15,150 controls from 51 studies were included in the final meta-analysis. The pooled results from all included studies showed a statistically significant association between GSTP1 Ile105Val polymorphism and urinary system cancer. In the subgroup analyses, the GSTP1 Ile105Val polymorphism was found to be significantly associated with prostate cancer risk and also a risk factor for urinary system cancer among Asians. In conclusion, our meta-analysis indicated that GSTP1 Ile105Val polymorphism was associated with urinary system cancer susceptibility, which needs to be validated by more rigorous data from further large-scale population studies with different ethnicities. PMID:27366093

  13. Association between GSTP1 Ile105Val polymorphism and urinary system cancer risk: evidence from 51 studies

    PubMed Central

    Zhang, Yixiang; Yuan, Yeqing; Chen, Yufang; Wang, Zhao; Li, Fangfang; Zhao, Qingsong

    2016-01-01

    The GSTP1 gene plays an important role in detoxification of carcinogens. GSTP1 gene polymorphisms may alter the susceptibility of urinary system cancer. Numerous studies have been performed to investigate the association between GSTP1 Ile105Val (rs1695 A>G) polymorphism and urinary system cancer risk. Nevertheless, the results remain controversial and only prostate cancer and bladder cancer are covered. We identified eligible studies from PubMed, Elsevier, and three equivalent Chinese databases including the Chinese National Knowledge Infrastructure, Wanfang, and Weipu. Pooled odds ratios and 95% confidence intervals were used to assess the strength of the association between GSTP1 Ile105Val polymorphism and urinary system cancer risk. In total, 11,762 cases and 15,150 controls from 51 studies were included in the final meta-analysis. The pooled results from all included studies showed a statistically significant association between GSTP1 Ile105Val polymorphism and urinary system cancer. In the subgroup analyses, the GSTP1 Ile105Val polymorphism was found to be significantly associated with prostate cancer risk and also a risk factor for urinary system cancer among Asians. In conclusion, our meta-analysis indicated that GSTP1 Ile105Val polymorphism was associated with urinary system cancer susceptibility, which needs to be validated by more rigorous data from further large-scale population studies with different ethnicities. PMID:27366093

  14. The ophiolite of the Eohellenic nappe in the island of Skyros, Greece: Geotectonic environment of formation and metamorphic conditions inferred by mineralogical and geochemical data

    NASA Astrophysics Data System (ADS)

    Karkalis, Christos; Magganas, Andreas; Koutsovitis, Petros

    2014-05-01

    , the occurrence of rodingites and ophicalcites clearly point to interaction of the gabbroic rocks and serpentinites with hydrothermal fluids, which most probably took place during the stage of exhumation and tectonic emplacement. Ophicalcites contain serpentine, calcite, magnetite, as well as rare pyroxene and spinel. Rodingites on their behalf include hydroandradite (Alm0.00Adr61.33-67.43Grs28.25-35.18Prp0.10-2.49Sps0.00-0.33Uv0.41-2.75), vesuvianite (MgO=2.78-3.33 wt.%; TiO2=0.02-0.59 wt.%) diopside neoblasts (En48.53-49.89Wo47.56-48.10Fs2.32-3.33; Mg#=93.96-96.28), chlorite and also accessory prehnite. Some small-sized Cr-bearing hydrogarnet crystals (Cr2O3=10.34 wt.%) were most likely formed at the expense of spinel. The types of hydrogarnet and vesuvianite crystals are highly indicative for the involvement of subduction-related fluids during the formation of the rodingites [6]. References: [1] Jacobshagen & Wallbrecher 1984: Geol. Soc., London, Sp. Pub. 17, 591-602, [2] Pe-Piper 1991: Ofioliti, 16, 111 - 120, [3] Kamenetsky Sobolev, Joron & Semet 2001: J Petrol 42, 655-671, [4] Agrawal, Guevara & Verma 2008: Intern. Geol. Rev. 50, 1057-1079, [5] Pearce & Cann 1973: Earth Plan. Sci. Lett. 19, 290-300, [6] Koutsovitis, Magganas, Pomonis & Ntaflos 2013. Lithos 172-173, 139-157.

  15. Effects of magmatic and metamorphic volatiles on the evolution of fluid-rock interactions and fluid pressure during contact metamorphism

    SciTech Connect

    Hanson, R.B. )

    1992-01-01

    Finite difference models of hydrothermal flow around a cooling intrusion that include fluid production from the magma during crystallization and from wall rocks during heating are used to investigate the evolution of fluid pressure and fluid-rock interactions during the contact metamorphism. For a granodiorite intrusion with a width of 9 km and releasing just 1: H[sub 2]O linearly during crystallization, fluid production elevates fluid pressures to lithostatic values above and adjacent to the intrusion when permeabilities are less than 1 [mu]D (10[sup [minus]18] m[sup 2]). Alternatively, hydrofracturing resulting from fluid production would be sufficient to create and maintain a time-averaged permeability of 1 [mu]D for 50,000 years: permeability decreases gradually with time afterward until the magma crystallizes (350,000 years). In detail, the history depends strongly on how fluids are released from the crystallizing magma. The effect is comparable to that obtained for devolatilization of 5% H[sub 2]O by weight over heating of 400 C in adjacent wall rocks. Fluid production dominates other mechanisms for elevating fluid pressures such as thermal expansion of pore fluids or ductile strain. In models with both magmatic and metamorphic fluids, fluid flow is outward from the inner aureole for much of the cooling history at wall-rock permeabilities of [le]100 [mu]D. Extensive up-temperature flow is not predicted. The evolution of flow is such that magmatic fluids can initially dominate fluid-rock interactions in a plume above the intrusion, although the timing of interaction of magmatic and metamorphic waters is sensitive to the detailed devolatilization histories. Initial pore fluids rapidly become insignificant in the overall fluid budget. Surface or external fluids infiltrate only late in the cooling history, as rocks within a few kilometers of the intrusion are cooling.

  16. Late Cretaceous to Paleocene metamorphism and magmatism in the Funeral Mountains metamorphic core complex, Death Valley, California

    USGS Publications Warehouse

    Mattinson, C.G.; Colgan, J.P.; Metcalf, J.R.; Miller, E.L.; Wooden, J.L.

    2007-01-01

    Amphibolite-facies Proterozoic metasedimentary rocks below the low-angle Ceno-zoic Boundary Canyon Detachment record deep crustal processes related to Meso-zoic crustal thickening and subsequent extension. A 91.5 ?? 1.4 Ma Th-Pb SHRIMP-RG (sensitive high-resolution ion microprobe-reverse geometry) monazite age from garnet-kyanite-staurolite schist constrains the age of prograde metamorphism in the lower plate. Between the Boundary Canyon Detachment and the structurally deeper, subparallel Monarch Spring fault, prograde metamorphic fabrics are overprinted by a pervasive greenschist-facies retrogression, high-strain subhorizontal mylonitic foliation, and a prominent WNW-ESE stretching lineation parallel to corrugations on the Boundary Canyon Detachment. Granitic pegmatite dikes are deformed, rotated into parallelism, and boudinaged within the mylonitic foliation. High-U zircons from one muscovite granite dike yield an 85.8 ?? 1.4 Ma age. Below the Monarch Spring fault, retrogression is minor, and amphibolite-facies mineral elongation lineations plunge gently north to northeast. Multiple generations of variably deformed dikes, sills, and leucosomal segregations indicate a more complex history of partial melting and intrusion compared to that above the Monarch Spring fault, but thermobarometry on garnet amphibolites above and below the Monarch Spring fault record similar peak conditions of 620-680 ??C and 7-9 kbar, indicating minor (<3-5 km) structural omission across the Monarch Spring fault. Discordant SHRIMP-RG U-Pb zircon ages and 75-88 Ma Th-Pb monazite ages from leucosomal segregations in paragneisses suggest that partial melting of Proterozoic sedimentary protoliths was a source for the structurally higher 86 Ma pegmatites. Two weakly deformed two-mica leucogranite dikes that cut the high-grademetamorphic fabrics below the Monarch Spring fault yield 62.3 ?? 2.6 and 61.7 ?? 4.7 Ma U-Pb zircon ages, and contain 1.5-1.7 Ga cores. The similarity of metamorphic

  17. Mapping of high pressure metamorphics in the As Sifah region, NE Oman using ASTER data

    NASA Astrophysics Data System (ADS)

    Rajendran, Sankaran; Nasir, Sobhi

    2015-02-01

    The high pressure metamorphic zone of As Sifah area in the Saih Hatat window, NE Oman plays a vital role to study global tectonic setting, metamorphism, transport direction and age of initial ophiolite emplacement. Scientists and researchers are keen in determining the protolith, structural evolution, and timing and metamorphic conditions of the Saih Hatat area. In this study, mapping of the metamorphic zone and discrimination of associated rock formations occurred in the As Sifah region is carried out using visible and near infrared-shortwave infrared (VNIR-SWIR) spectral bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and well known image processing methods such as image decorrelation, Principal Component Analysis (PCA) and Spectral Angel Mapper (SAM). The study delineated the region of metamorphic zone and discriminated the different metamorphic and carbonate rocks of the study area characterized by hydroxyl (OH) and carbonate bearing minerals. The assessment of accuracy for the occurrence and spatial distribution of major lithological units provided the overall accuracy of 96.06% with Kappa Coefficient = 0.95 in the matrix of Maximum Likelihood (ML) and compared with the Spectral Angle Mapper (SAM) and Spectral Information Divergence (SID) algorithms. The occurrence of such minerals are detected and confirmed by SAM supervised classification method. The study also describes the spectral character of metamorphic and carbonates minerals. The metamorphic zone and associated rock types interpreted over the images are verified in the field and checked for their occurrences and spatial distributions. The occurrence of CO3 bearing carbonate minerals and OH bearing metamorphic minerals are confirmed further under microscope, XRD analysis and PIMA spectral measurements in the laboratory studies. The study proved sensor capability of ASTER to discriminate metamorphic rocks from associated formations and detection of different mineral

  18. Permo-Triassic and Paleoproterozoic metamorphism related to continental collision in Yangpyeong, South Korea

    NASA Astrophysics Data System (ADS)

    Oh, Chang Whan; Imayama, Takeshi; Lee, Seung Yeol; Yi, Sang-Bong; Yi, Keewook; Lee, Byung Choon

    2015-02-01

    Gneisses and migmatites exposed in the Yangpyeong area in the northern Gyeonggi Massif provide insight into the Paleoproterozoic and Triassic metamorphic events in South Korea. Garnet-biotite gneiss and sillimanite-garnet-biotite gneiss in the western part of the area reveal Paleoproterozoic metamorphism (1888-1871 Ma) at P-T conditions of 760-820 °C and 8-10 kbar and 710-750 °C and 5-7 kbar, respectively. These rocks were overprinted by low-P/T type metamorphism (590-650 °C, 3-4 kbar) during the Triassic (ca. 237 Ma). In contrast, a cordierite-rich migmatite near the post-collisional Triassic igneous complex in the eastern part of the area was strongly metamorphosed during the Triassic (ca. 235 Ma) at 750-790 °C and 7-8 kbar. The similar Triassic ages in the western and eastern areas suggest that low-P/T type metamorphism occurred as a second stage of regional metamorphism, which is characterized by the production of cordierite with an irregularly shaped garnet. The metamorphic grade of the Triassic metamorphism decreases spatially towards the west from granulite facies to amphibolite facies metamorphic conditions, and the Paleoproterozoic metamorphism is well preserved in the western part with low grade Triassic metamorphism. The new discovery of the Triassic metamorphic event in the Yangpyeong area, in addition to the previously reported Triassic post-collision igneous event, supports the idea that the continental collision belt between the North and South China blocks extends from the Hongseong area into the Odesan area through the Yangpyeong area in South Korea.

  19. Phase-field modeling of dry snow metamorphism.

    PubMed

    Kaempfer, Thomas U; Plapp, Mathis

    2009-03-01

    Snow on the ground is a complex three-dimensional porous medium consisting of an ice matrix formed by sintered snow crystals and a pore space filled with air and water vapor. If a temperature gradient is imposed on the snow, a water vapor gradient in the pore space is induced and the snow microstructure changes due to diffusion, sublimation, and resublimation: the snow metamorphoses. The snow microstructure, in turn, determines macroscopic snow properties such as the thermal conductivity of a snowpack. We develop a phase-field model for snow metamorphism that operates on natural snow microstructures as observed by computed x-ray microtomography. The model takes into account heat and mass diffusion within the ice matrix and pore space, as well as phase changes at the ice-air interfaces. Its construction is inspired by phase-field models for alloy solidification, which allows us to relate the phase-field to a sharp-interface formulation of the problem without performing formal matched asymptotics. To overcome the computational difficulties created by the large difference between diffusional and interface-migration time scales, we introduce a method for accelerating the numerical simulations that formally amounts to reducing the heat- and mass-diffusion coefficients while maintaining the correct interface velocities. The model is validated by simulations for simple one- and two-dimensional test cases. Furthermore, we perform qualitative metamorphism simulations on natural snow structures to demonstrate the potential of the approach. PMID:19391945

  20. Volatile elements in chondrites - Metamorphism or nebular fractionation

    NASA Technical Reports Server (NTRS)

    Takahashi, H.; Gros, J.; Higuchi, H.; Morgan, J. W.; Anders, E.

    1978-01-01

    Three of the most highly metamorphosed meteorites of their respective classes, Shaw (LL7), Karoonda (C5), and Coolidge (C4), were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Comparison with data by Lipschutz and coworkers (1977) on artificially heated primitive meteorites shows that the natural metamorphism of meteorites cannot have taken place in a system open to volatiles. Shaw, metamorphosed at 1300 C for more than 1 million yr, is less depleted in In, Bi, Ag, Te, Zn, and Tl than Krymka heated at 1000 C for 1 week. Karoonda, metamorphosed at 600 C for many millennia, is less depleted in Bi and Tl than Allende heated at 600 C for 1 week. Data on primordial noble gases also show that the volatile-element patterns of ordinary and carbonaceous chondrites were established by nebular condensation and changed little, if at all, during metamorphism. For enstatite chondrites, the evidence is still incomplete but seems to favor a nebular origin of the volatile pattern.

  1. Metamorphism of San Antonio Terrane metapelites, San Gabriel Mountains, California

    SciTech Connect

    Archuleta, L.; Ishimatsu, J.; Schneiderman, J.S. . Geology Dept.)

    1993-04-01

    Pelitic schists and gneisses from the San Antonio terrane in the eastern San Gabriel Mountains consist of garnet, biotite, plagioclase, quartz, sillimanite, cordierite, hercynite [+-] alkali feldspar. Large garnet porphyroblasts contain quartz, plagioclase and sillimanite inclusions. Cordierite occurs as haloes around garnet porphyroblasts and as small subgrains always associated with hercynite and together replacing sillimanite blades. Hercynite additionally appears to have nucleated on the edges of sillimanite blades. Contrary to previous investigations, hercynite appears to be a late mineral phase. Reaction textures described above have been used to calculate a set of net-transfer reactions that can be used (1) to characterize all possible exchanges of matter between minerals in the system and (2) to construct a reaction space for the system. Fourteen thin sections with large garnet porphyroblasts and abundant biotite were used for microprobe analysis. Detailed probe analyses show well-developed zoning in the plagioclase and alkali feldspar whose character varies depending on location in the thin section relative to neighboring minerals. Generally, large plagioclase porphyroblasts display normal zoning and are not as calcium-rich as plagioclase inclusions in the garnet. Garnet porphyroblasts have flat zoning profiles due to high temperatures of metamorphism. Pressures and temperatures of metamorphism have been calculated from these assemblages using garnet-biotite geothermometry and quartz-garnet-aluminosilicate-plagioclase geobarometry.

  2. Blueschist-facies metamorphism related to regional thrust faulting

    USGS Publications Warehouse

    Blake, M.C., Jr.; Irwin, W.P.; Coleman, R.G.

    1969-01-01

    Rocks of the blueschist (glaucophane schist) facies occur throughout the world in narrow tectonic belts associated with ultramafic rocks. In the Coast Range province of California, blueschist rocks are devloped in the eugeosynclinal Franciscan Formation of Late Mesozoic age. The blueschist rocks form a narrow belt for more than 800 km along the eastern margin of this province and commonly are separated from rocks of an overlying thrust plate by serpentinite. Increasing metamorphism upward toward the thrust fault is indicated mineralogically by a transition from pumpellyite to lawsonite and texturally by a transition from metagraywacke to schist. The blueschist metamorphism probably occurred during thrusting in a zone of anomalously high water pressure in the lower plate along the sole of the thrust fault. This tectonic mode of origin for blueschist differs from the generally accepted hypothesis involving extreme depth of burial. Other belts of blueschist-facies rocks, including the Sanbagawa belt of Japan, the marginal synclinal belt of New Zealand, and the blueschist-ultramafic belts of Venezuela, Kamchatka, Ural mountains, and New Caledonia have similar geologic relations and might be explained in the same manner. ?? 1969.

  3. Behavior of high-carbon solids during metamorphism

    SciTech Connect

    Lobzova, R.V.; Ziborova, T.A.

    1988-02-01

    Some viscous and hard bitumens (high-carbon solids) are relicts from former oil pools and consist of almost all classes in the main naphthide genetic group: from malthas and asphalts to kerites and anthraxolites. Details have been given on the occurrence of bitumens and high-viscosity oils, as well as on their compositions. Bitumens soluble in organic solvents (asphalts and asphaltites) occur mainly in oil-pool zones, whereas insoluble or partially soluble bitumens (kerites and anthraxolites) occur in oil-gas pool zones. Hard bitumens vary in composition in accordance with their origins. The authors have applied infrared spectroscopy to high-carbon solids ranging from asphaltite to graphite derived from rocks showing various grades of catagenesis and metamorphism; they examined the least altered bitumens from low-temperature zones, which were represented by asphaltites, as well as the more altered kerites and anthraxolites, and the highly altered shungites and graphites from rocks showing metamorphism ranging from the greenschist to the granulite facies. 14 references.

  4. Microdeformation in Vredefort rocks; evidence for shock metamorphism

    NASA Technical Reports Server (NTRS)

    Reimold, W. U.; Andreoli, M. A. G.; Hart, R. J.

    1988-01-01

    Planar microdeformations in quartz from basement or collar rocks of the Vredefort Dome have been cited for years as the main microtextural evidence for shock metamorphism in this structure. In addition, Schreyer describes feldspar recrystallization in rocks from the center of the Dome as the result of transformation of diaplectic glass, and Lilly reported the sighting of mosaicism in quartz. These textural observations are widely believed to indicate either an impact or an internally produced shock origin for the Vredefort Dome. Two types of (mostly sub) planar microdeformations are displayed in quartz grains from Vredefort rocks: (1) fluid inclusion trails, and (2) straight optical discontinuities that sometimes resemble lamellae. Both types occur as single features or as single or multiple sets in quartz grains. Besides qualitative descriptions of cleavage and recrystallization in feldspar and kinkbands in mica, no further microtextural evidence for shock metamorphism at Vredefort has been reported to date. Some 150 thin sections of Vredefort basement rocks were re-examined for potential shock and other deformation effects in all rock-forming minerals. This included petrographic study of two drill cores from the immediate vicinity of the center of the Dome. Observations recorded throughout the granitic core are given along with conclusions.

  5. Metamorphism of the Murphy belt, Marble Hill, GA

    SciTech Connect

    La Tour, T.E.; Gray, J. . Geology Dept.)

    1993-03-01

    Rocks of the Murphy belt consist of marble and metamorphosed mafic and highly aluminous pelitic rocks. The aluminous rocks contain sillimanite + kyanite + staurolite + garnet (gt) + muscovite + biotite + plagioclase + quartz [+-] tourmaline. Staurolite and kyanite are relict and closely intergrown. Garnet occurs as two generations, gt 1 and gt 2. Gt 1 and the biotite schistosity are coeval. Sillimanite needles and large porphyroblasts of muscovite (0.5--2.0 cm), formed from kyanite-staurolite aggregates coevally with gt 2, and both contain inclusions of relict kyanite and staurolite. Both are younger than the primary biotite schistosity and grew at sillimanite-muscovite grade. Muscovite porphyroblasts are partially recrystallized, leaving mica fish with thin trails of fine-grained muscovite. Kyanite [+-] staurolite are partially to completely recrystallized to spindle shaped aggregates and fine-grained muscovite. Some fine muscovite mantles the earlier phases and defined the new foliation. No sillimanite occurs in the recrystallized muscovite. This extreme grain size reduction occurred during medium-T retrograde metamorphism and converted many rocks into button schists or phyllonites. The above indicate extreme internal deformation following the metamorphic peak, during which primary sedimentary structures were destroyed. Also, competent mafic lithologies were dismembered into pods and discontinuous layers. Lithologic boundaries are no longer sedimentary, but tectonic. The association of aluminous schists and mafic rocks suggests deep-marine deposition, probably along a convergent margin. Conversely, the association is inconsistent with shallow deposition along a stable passive margin. The marble probably represents discontinuous reefs associated with the volcanic arc.

  6. Role of temperature and time on organic metamorphism

    SciTech Connect

    Gretener, P.E.; Curtis, C.D.

    1982-08-01

    Organic metamorphism--kerogen-to-hydrocarbon transformation--is a function of both temperature and exposure time. The effect of temperature is exponential of that of time linear. At very low temperatures (<122/sup 0/F; <50/sup 0/C), the conversion rate is so low that time has no effect, since even long time spans of 300 to 500 Ma cannot compensate for this factor. At high temperatures (>266/sup 0/F; >130GAMMA) the reaction proceeds at such a high rate that time also plays no important role. The effect of time is noticeable in the range of 158 to 212/sup 0/F (70 to 100/sup 0/C), where intermediate conversion rates prevail. Stopping the heating process (termination of burial) freezes the rate-constant of the reaction and allows organic metamorphism to continue at a linear rather than exponential rate. This effect is demonstrated with the help of a simple geologic model. For the first example, a source rock was subjected to continuous linear heating, whereas, for the second, the heating was terminated at a certain temperature level. The model was analyzed by using the oleum scale, a modified Lopatin approach.

  7. Ti diffusion in quartz inclusions: implications for metamorphic time scales

    NASA Astrophysics Data System (ADS)

    Spear, Frank S.; Ashley, Kyle T.; Webb, Laura E.; Thomas, Jay B.

    2012-12-01

    Quartz inclusions in garnet from samples collected from the staurolite zone in central New England are zoned in cathodoluminescence (CL). The CL intensity is interpreted to be a proxy for Ti concentration and the zoning attributed to Ti diffusion into the quartz grains driven by Ti exchange between quartz and enclosing garnet as a function of changing temperature. The CL zoning has been interpreted using a numerical diffusion model to constrain the time scales over which the diffusion has occurred. Temperature-time histories are sensitive to the presumed peak temperature but not to other model parameters. The total time of the metamorphic heating and cooling cycle from around 450 °C to the peak temperature (550-600 °C) back to 450 °C is surprisingly short and encompasses only 0.2-2 million years for peak temperatures of 600-550 °C. The metamorphism was accompanied by large-scale nappe and dome formation, and it is suggested that this occurred as a consequence of in-sequence thrusting resulting in a mid-crustal ductile duplex structure.

  8. Early metamorphic insertion technology for insect flight behavior monitoring.

    PubMed

    Verderber, Alexander; McKnight, Michael; Bozkurt, Alper

    2014-01-01

    Early Metamorphosis Insertion Technology (EMIT) is a novel methodology for integrating microfabricated neuromuscular recording and actuation platforms on insects during their metamorphic development. Here, the implants are fused within the structure and function of the neuromuscular system as a result of metamorphic tissue remaking. The implants emerge with the insect where the development of tissue around the electronics during pupal development results in a bioelectrically and biomechanically enhanced tissue interface. This relatively more reliable and stable interface would be beneficial for many researchers exploring the neural basis of the insect locomotion with alleviated traumatic effects caused during adult stage insertions. In this article, we implant our electrodes into the indirect flight muscles of Manduca sexta. Located in the dorsal-thorax, these main flight powering dorsoventral and dorsolongitudinal muscles actuate the wings and supply the mechanical power for up and down strokes. Relative contraction of these two muscle groups has been under investigation to explore how the yaw maneuver is neurophysiologically coordinated. To characterize the flight dynamics, insects are often tethered with wires and their flight is recorded with digital cameras. We also developed a novel way to tether Manduca sexta on a magnetically levitating frame where the insect is connected to a commercially available wireless neural amplifier. This set up can be used to limit the degree of freedom to yawing "only" while transmitting the related electromyography signals from dorsoventral and dorsolongitudinal muscle groups. PMID:25079130

  9. Testing and Validating Machine Learning Classifiers by Metamorphic Testing☆

    PubMed Central

    Xie, Xiaoyuan; Ho, Joshua W. K.; Murphy, Christian; Kaiser, Gail; Xu, Baowen; Chen, Tsong Yueh

    2011-01-01

    Machine Learning algorithms have provided core functionality to many application domains - such as bioinformatics, computational linguistics, etc. However, it is difficult to detect faults in such applications because often there is no “test oracle” to verify the correctness of the computed outputs. To help address the software quality, in this paper we present a technique for testing the implementations of machine learning classification algorithms which support such applications. Our approach is based on the technique “metamorphic testing”, which has been shown to be effective to alleviate the oracle problem. Also presented include a case study on a real-world machine learning application framework, and a discussion of how programmers implementing machine learning algorithms can avoid the common pitfalls discovered in our study. We also conduct mutation analysis and cross-validation, which reveal that our method has high effectiveness in killing mutants, and that observing expected cross-validation result alone is not sufficiently effective to detect faults in a supervised classification program. The effectiveness of metamorphic testing is further confirmed by the detection of real faults in a popular open-source classification program. PMID:21532969

  10. Misoriented faults in exhumed metamorphic complexes: Rule or exception?

    NASA Astrophysics Data System (ADS)

    Massironi, Matteo; Bistacchi, Andrea; Menegon, Luca

    2011-07-01

    Low angle normal faults and other weak faults are common in the metamorphic core of collisional orogens. They frequently show a phyllosilicate-rich mylonitic foliation that was reactivated under brittle conditions. Experimental and theoretical works indicate that mechanical anisotropies exert a substantial influence on shear failure and frictional sliding, eventually inhibiting the nucleation and propagation of new Andersonian shear fractures and favoring the localization of brittle failure along the pre-existing foliations. Metamorphic phyllosilicate-rich rocks may show a friction coefficient varying from 0.6, at high angles to the foliation, to 0.2-0.4, for shear along the inherited foliation. To test the influence of mechanical anisotropies on the development of non-Andersonian faults, we have applied a modified slip tendency analysis to three misoriented phyllosilicate-rich faults of the European Alps. The analysis accounts for anisotropy in friction coefficients, and has been named "Anisotropic Slip Tendency analysis". Here we show that brittle deformation along misoriented phyllosilicate-rich foliations is more probable than the development of new Andersonian faults. The presence of a well developed network of weak, phyllosilicate-rich faults may influence the overall structural style and mechanical properties of the brittle lithosphere in collisional orogens.

  11. Zoning and recrystallization of phengitic micas: implications for metamorphic equilibration

    NASA Astrophysics Data System (ADS)

    Dempster, T. J.

    1992-02-01

    White micas (phengites) in the metasediments of the Scottish Dalradian display a large range of compositions within single samples. The variations in the composition of these phengites are strongly controlled by their structural age, with early fabrics containing a paragonite-poor, celadonite-rich phengite whereas in later fabrics the micas are generally paragonite-rich and celadonite-poor. Retrograde phengite growth, identified using back scattered electron imaging, occurs as celadonite-rich rims on micas within all existing fabrics and appears to be preferentially developed along existing white mica-plagioclase grain boundaries. The presence of these chemically distinct phengite populations within single samples implies that chemical exchange between the individual micas was inefficient. It is proposed that diffusion-controlled exchange reactions in phengites have relatively high closure temperatures below which major element exchange is effectively impossible. This closed system behaviour of micas questions the ease with which phengites may equilibrate with other phases during prograde greenschist and lower amphibolite facies metamorphism. Many of the chemical variations preserved in phengites from such metamorphic rocks may reflect deformation/recrystallization controlled equilibria.

  12. Early Metamorphic Insertion Technology for Insect Flight Behavior Monitoring

    PubMed Central

    Bozkurt, Alper

    2014-01-01

    Early Metamorphosis Insertion Technology (EMIT) is a novel methodology for integrating microfabricated neuromuscular recording and actuation platforms on insects during their metamorphic development. Here, the implants are fused within the structure and function of the neuromuscular system as a result of metamorphic tissue remaking. The implants emerge with the insect where the development of tissue around the electronics during pupal development results in a bioelectrically and biomechanically enhanced tissue interface. This relatively more reliable and stable interface would be beneficial for many researchers exploring the neural basis of the insect locomotion with alleviated traumatic effects caused during adult stage insertions. In this article, we implant our electrodes into the indirect flight muscles of Manduca sexta. Located in the dorsal-thorax, these main flight powering dorsoventral and dorsolongitudinal muscles actuate the wings and supply the mechanical power for up and down strokes. Relative contraction of these two muscle groups has been under investigation to explore how the yaw maneuver is neurophysiologically coordinated. To characterize the flight dynamics, insects are often tethered with wires and their flight is recorded with digital cameras. We also developed a novel way to tether Manduca sexta on a magnetically levitating frame where the insect is connected to a commercially available wireless neural amplifier. This set up can be used to limit the degree of freedom to yawing “only” while transmitting the related electromyography signals from dorsoventral and dorsolongitudinal muscle groups. PMID:25079130

  13. Metabolism of thyroxine in Rana catesbeiana tadpoles during metamorphic climax

    SciTech Connect

    Galton, V.A.; Munck, K.

    1981-01-01

    Previous studies have indicated that premetamorphic tadpoles do not convert T4 to T3 to a measurable extent (1). The present study was performed to determine whether a T4 5'-monodeiodinating system is acquired at later stages of development. (/sup 125/I)T4 metabolism in vivo was determined in tadpoles at most stages of prometamorphosis and metamorphic climax and, for comparison, in premetamorphic tadpoles. The conversion of (/sup 125/I)T4 to (/sup 125/I)T3, as indicated by the presence of an /sup 125/I-labeled product in serum and liver preparations that cochromatographed with carrier T3, was sometimes observed in tadpoles near the end of prometamorphosis and was always evident in tadpoles that were either undergoing or had completed metamorphic climax. However, during this phase, no correlation could be drawn between the extent of T3 production and morphological development. The formation of T3 from T4 in vivo was significantly decreased in tadpoles pretreated with propylthiouracil. The T45'-monodeiodinating system could be induced in premetamorphic tadpoles by injecting them with either T4 or T3. This finding together with the observation that normal acquisition of this system occurs at the time when endogenous T4 and T3 levels are rising rapidly suggest that its development is under the control of the thyroid hormones.

  14. Effects of thermal metamorphism on compositions of lunar spinels

    NASA Technical Reports Server (NTRS)

    Misra, K. C.; Taylor, L. A.

    1977-01-01

    The reported study represents an attempt to evaluate experimentally the compositional and textural changes that are likely to be observed in the Fe-Ti-Cr spinels of lunar igneous rocks by subsequent thermal metamorphism. The Apollo 12 igneous rock, 12018,43, was chosen for this investigation because an earlier study of another fraction of this rock by El Goresy et al. (1971) has reported an almost continuous trend of spinel compositions between Cr-Ulvoespinel and Ti-chromite. The nature of the compositional changes in the heated spinels (and ilmenites) is found to be such that the changes cannot be explained by intragranular adjustments alone. In the heated sample, pyroxene grains adjacent to the high-Ti spinels show a decrease in FeO, and an increase in MgO and Al2O3 at the interface. This may account for the MgO depletion and a part of the FeO enrichment in the high-Ti spinels. It is believed that the heating experiment demonstrates that thermal metamorphism of lunar basalts is likely to modify the compositions of their preexisting spinels (and ilmenites).

  15. Oxygen isotope record of fluid-rock-SiO 2 interaction during Variscan progressive deformation and quartz veining in the meta-volcanosediments of Belle-Ile (Southern Brittany)

    NASA Astrophysics Data System (ADS)

    Schulz, Bernhard; Audren, Claude; Triboulet, Claude

    2002-08-01

    Belle-Ile in the South Armorican Domain is composed of Palaeozoic volcano-detrital sequences with sericite phyllites and porphyroids. Fine-banded and folded meta-tuffites, microquartzites and graphitic quartzites occur in the basal part at Plage de Bordardoué. Phengite compositions constrain that Variscan metamorphism did not exceed 430 °C/4.5 kbar. Four generations (1-4) of centimeter-thick quartz veins were precipitated during Variscan progressive deformation and recorded changing fluid compositions. Values of 26‰ δ18O SMOW in vein 1 quartz exceed high δ18O SMOW in the host rocks. Decrease of quartz δ18O SMOW from margins to centers can be observed from the syntaxial veins. Younger veins 4 have lower δ18O. Their inclusions indicate lower salinities and traces of CH 4 in the fluid when compared with veins 1. Veins 1 were overprinted by shearing and fissuring. Subgrain rotation recrystallization occurred along briquette structures and subgrain boundaries. The initial isotope values have been preserved. Larger domains with small-grained quartz can be identified by lower values of δ18O. Homogeneous isotopic compositions are found in hinges of folded veins 2 with grain boundary migration recrystallization. The small-scale oxygen isotope variations and the changing fluid compositions point to a locally hosted fluid system with a limited contribution of meteoric water during multiphase deformation and vein formation.

  16. Marine flora of the Iles Eparses (Scattered Islands): A longitudinal transect through the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Mattio, L.; Zubia, M.; Maneveldt, G. W.; Anderson, R. J.; Bolton, J. J.; de Gaillande, C.; De Clerck, O.; Payri, C. E.

    2016-04-01

    The diversity of marine macrophytes of small islands in the South Western Indian Ocean region has been poorly documented and little or no information is available for the Iles Eparses (or Scattered Islands) in the Mozambique Channel. We present the first species checklist for the three largest islands of the Iles Eparses: Europa, Juan de Nova and Glorioso. Overall, with a total of 321 marine macrophyte species recorded (incl. 56% Rhodophyta, 27% Chlorophyta, 15% Phaeophyceae and 2% Magnoliophyta; Europa: 134 spp., Juan de Nova: 157 spp. and Glorioso: 170 spp.) these islands harbour 23.5% of the total species recorded for the Mozambique Channel region. We report 36 new records for the Mozambique Channel including 29 undescribed new and cryptic species. Our results highlight a decrease in species richness southward in the Channel. Because of their longitudinal arrangement between the northern and the southern ends of the Channel and their central position, Europa, Juan de Nova and Glorioso Islands represent data points of particular biogeographical interest and could be critical 'stepping stones' for connectivity in the highly dynamic Mozambique Channel region.

  17. Benthic cyanobacterial diversity of Iles Eparses (Scattered Islands) in the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Zubia, Mayalen; Turquet, Jean; Golubic, Stjepko

    2016-04-01

    The marine benthic cyanobacteria of the Iles Eparses, Mozambique Channel, were surveyed for the first time. A total of 39 species are reported: 29 from Europa, 17 from Glorioso and 23 from Juan de Nova Islands. The higher biodiversity in Europa is explained by greater habitat diversity on this Island with unique ecosystems (mangroves, fossil reefs, pools). Average species richness varied between the geomorphological habitat types with higher diversity in shallow environments (fossil reef pools, mangroves, reef flats), which are characterized by high temperatures and high irradiances. The most common species observed on the three islands were Hydrocoleum coccineum, Hydrocoleum glutinosum, Hydrocoleum lyngbyaceum, Phormidium laysanense, Lyngbya sordida, and Symploca hydnoides; which are also the dominant species observed in the Southwest Indian Ocean region. The most frequent species was Phormidium laysanense with extensive cover observed in the northwest of Juan de Nova Island. Our study provided a comparison between the cyanobacterial flora of Iles Eparses and the recorded surveys in the Southwest Indian Ocean region. The low similarity observed between these species lists could be explained by differences in sampling strategies and efforts, as well as by different taxonomic approaches employed in past regional studies.

  18. Ultrahigh-pressure metamorphism: tracing continental crust into the mantle

    NASA Astrophysics Data System (ADS)

    Chopin, Christian

    2003-07-01

    More and more evidence is being discovered in Phanerozoic collision belts of the burial of crustal rocks to previously unsuspected (and ever increasing) depths, presently on the order of 150-200 km, and of exhumation from such depths. This extends by almost one order of magnitude the depth classically ascribed to the metamorphic cycling of continental crust, and demonstrates its possible subduction. The pieces of evidence for this new, ultrahigh-pressure (UHP) metamorphism exclusively occur in the form of relics of high-pressure minerals that escaped back-transformation during decompression. The main UHP mineral indicators are the high-pressure polymorphs of silica and carbon, coesite and microdiamond, respectively; the latter often demonstrably precipitated from a metamorphic fluid and is completely unrelated to kimberlitic diamond or any shock event. Recent discoveries of pyroxene exsolutions in garnet and of coesite exsolutions in titanite suggest a precursor garnet or titanite containing six-fold coordinated silicon, therefore still higher pressures than implied by diamond stability, on the order of 6 GPa. The UHP rocks raise a formidable geological problem: that of the mechanisms responsible for their burial and, more pressingly, for their exhumation from the relevant depths. The petrological record indicates that large tracts of UHP rocks were buried to conditions of low T/ P ratio, consistent with a subduction-zone context. Decompression occurred in most instances under continuous cooling, implying continuous heat loss to the footwall and hangingwall of the rising body. This rise along the subduction channel - an obvious mechanical discontinuity and weak zone - may be driven by buoyancy up to mid-crustal levels as a result of the lesser density of the acidic crustal rocks (even if completely re-equilibrated at depth) after delamination from the lower crust, in a convergent setting. Chronological studies suggest that the rates involved are typical plate

  19. Dating Subduction Zone Metamorphism with Garnet and Lawsonite Geochronology

    NASA Astrophysics Data System (ADS)

    Mulcahy, S. R.; Vervoort, J. D.

    2013-12-01

    Lawsonite [CaAl2Si2O7(OH)2 H2O] is a critical index mineral for high- to ultrahigh-pressure metamorphism associated with subduction. Lawsonite is an important carrier of water into the mantle, a likely contributor to subduction zone seismicity, and a bearer of trace elements that link metamorphism to arc magmatism. Due to its limited pressure-temperature stability, lawsonite can serve as a powerful petrogenetic indicator of specific metamorphic events. Lu-Hf dating of lawsonite, therefore provides a potentially powerful new tool for constraining subduction zone processes in a pressure-temperature window where few successful geochronometers exist. Broad application of lawsonite Lu-Hf geochronology requires constraining the role of pressure-temperature path, lawsonite forming reactions, and the Lu and Hf systematics within lawsonite and other blueschist facies minerals. We are working to address the role of the metamorphic path on the applicability of lawsonite Lu-Hf geochronology within the Franciscan Complex of California. The Franciscan Complex preserves mafic high-grade exotic blocks in melange that underwent a counterclockwise pressure-temperature path wherein garnet, which strongly partitions heavy rare-earth elements, formed prior to lawsonite. Coherent mafic rocks within the Franciscan Complex, however, underwent a clockwise pressure-temperature path and lawsonite growth occurred prior to garnet. We sampled exotic blocks of garnet-hornblendite, garnet-epidote amphibolite, garnet-epidote blueschist, and lawsonite blueschist from the Berkeley Hills and Tiburon Peninsula of California. We collected four samples from coherent lawsonite blueschist across the lawsonite-pumpellyite-epidote isograds in Ward Creek, near Cazadero California. High-grade blocks give ages similar to existing Franciscan geochronology: multi-stage garnet in hornblendite gives the following ages: 171×1.3 Ma (MSWD 2.8) for the core and 159.4×0.9 Ma (MSWD 2.0) for the corresponding rim; 166

  20. The Dipeptides Ile-Tyr and Ser-Tyr Exert Distinct Effects on Catecholamine Metabolism in the Mouse Brainstem

    PubMed Central

    Moriyasu, Kazuki; Ichinose, Takashi; Nakahata, Akane; Tanaka, Mitsuru; Matsui, Toshiro; Furuya, Shigeki

    2016-01-01

    Catecholamine synthesis and transmission in the brain are influenced by the availability of Tyr in the body. In this study, we compared the effects of oral administration of Tyr-containing dipeptides Ile-Tyr, Ser-Tyr, and Tyr-Pro with Tyr alone on catecholamine metabolism in the mouse brainstem. Among these dipeptides, Ile-Tyr administration led to increases in dopamine, the dopamine metabolites homovanillic acid, and 3,4-dihydroxyphenylacetic acid, compared to administration of Ser-Tyr, Tyr-Pro, or Tyr alone. In comparison, administration of Ser-Tyr induced significantly increasing noradrenaline turnover, while Tyr-Pro administration suppressed dopamine turnover. Therefore, oral administration of Ile-Tyr, Ser-Tyr, and Tyr-Pro differentially affected metabolism of dopamine and noradrenaline. These observations strongly suggest that Tyr-containing dipeptides exert distinct effects on catecholamine metabolism in the brainstem when ingested orally. PMID:26981137

  1. Ozonation of coal vitrinites of different metamorphism degrees in gas and liquid phases

    SciTech Connect

    S.A. Semenova; Y.F. Patrakov

    2007-02-15

    The comparative analysis of the dynamics of accumulation of oxygen-containing groups in coals of different metamorphism degrees under their ozonation in the gas phase and in chloroform has been performed. The coals of the middle stage of metamorphism demonstrate the highest reactivity. The ozonation in chloroform proceeds with a higher intensity.

  2. The "Key" Method of Identifying Igneous and Metamorphic Rocks in Introductory Laboratory.

    ERIC Educational Resources Information Center

    Eves, Robert Leo; Davis, Larry Eugene

    1987-01-01

    Proposes that identification keys provide an orderly strategy for the identification of igneous and metamorphic rocks in an introductory geology course. Explains the format employed in the system and includes the actual key guides for both igneous and metamorphic rocks. (ML)

  3. Displacement calculations across a metamorphic core complex mylonite zone: Pinaleno Mountains, southeastern Arizona

    SciTech Connect

    Naruk, S.J.

    1987-07-01

    Minimum offset of 7 km across the Pinaleno Mountains metamorphic core complex is calculated by integrating the shear strains across the exposed width of the mylonite zone. The calculated displacement equals the offset on the associated detachment fault, estimated from offset marker beds. The method of determining displacement by strain integration may be directly applicable to many other metamorphic core complexes.

  4. A common high-pressure metamorphic evolution of interlayered eclogites and metasediments from the 'ultrahigh-pressure unit' of the Tianshan metamorphic belt in China

    NASA Astrophysics Data System (ADS)

    Li, Ji-Lei; Klemd, Reiner; Gao, Jun; Jiang, Tuo; Song, Yun-Hui

    2015-06-01

    Petrological and mineralogical data of interlayered eclogite, marble and quartz-mica schist from a drill core are used to constrain the metamorphic evolution of metavolcanics and intercalated metasediments in the Tianshan (ultra-)high-pressure/low-temperature [(U)HP/LT] metamorphic belt, NW China. The eclogite mainly consists of varying amounts of garnet, omphacite, quartz and zoisite, the marble of calcite (> 95 vol.%) with minor zoisite and phengite, and the schist of quartz and mica with minor calcite, chlorite, albite and garnet. Using garnet isopleth thermobarometry, pseudosection calculations for the eclogite and quartz-mica schist reveal a common metamorphic evolution under HP condition of both rock types that is also consistent with the temperature estimates for the marble using conventional thermometry. The uniform P-T paths of the interlayered eclogite and quartz-mica schist, as well as compatible temperature data of the marble, document that the whole rock suite constitutes a coherent HP unit during peak metamorphic conditions and exhumation. Thus protoliths of eclogite and associated sediments are believed to have undergone the same metamorphic evolution. In addition, the data gained by the present study of the HP rocks, which were collected in the northern part of the Chinese Tianshan (U)HP/LT belt, do not support the recently proposed tectonic scheme that this metamorphic terrane consists of a northern "coherent UHP unit" and a southern "coherent HP unit".

  5. Calculation of metamorphic two-dimensional quantum energy system: Application to wetting layer states in InAs/InGaAs metamorphic quantum dot nanostructures

    SciTech Connect

    Seravalli, L.; Trevisi, G.; Frigeri, P.

    2013-11-14

    In this work, we calculate the two-dimensional quantum energy system of the In(Ga)As wetting layer that arises in InAs/InGaAs/GaAs metamorphic quantum dot structures. Model calculations were carried on the basis of realistic material parameters taking in consideration their dependence on the strain relaxation of the metamorphic buffer; results of the calculations were validated against available literature data. Model results confirmed previous hypothesis on the extrinsic nature of the disappearance of wetting layer emission in metamorphic structures with high In composition. We also show how, by adjusting InGaAs metamorphic buffer parameters, it could be possible: (i) to spatially separate carriers confined in quantum dots from wetting layer carriers, (ii) to create an hybrid 0D-2D system, by tuning quantum dot and wetting layer levels. These results are interesting not only for the engineering of quantum dot structures but also for other applications of metamorphic structures, as the two design parameters of the metamorphic InGaAs buffer (thickness and composition) provide additional degrees of freedom to control properties of interest.

  6. Mineralogical controls on metamorphic fluid flow in metabasaltic sills from Islay, Scotland

    NASA Astrophysics Data System (ADS)

    Kleine, Barbara I.; Pitcairn, Iain K.; Skelton, Alasdair D. L.

    2016-04-01

    In this study we show that mineralogy was the primary control of metamorphic fluid flow in the well-studied metabasaltic sills in the SW Scottish Highlands. Here, basaltic sills have been partially carbonated by H2O-CO2 fluids at greenschist facies conditions. This has led to mineral zonation with carbonate-poor sill interiors separated from carbonate-rich sill margins by reaction fronts. Although deformation set the stage for metamorphic fluid flow in the SW Scottish Highlands by causing the preferred alignment of mineral grains, metamorphic fluid flow was not coupled with active deformation but occurred later utilizing the pre-existing mineral alignment as a means of accessing the sill interiors. The sills which were studied were partially carbonated with well-preserved reaction fronts. They were selected because (atypically for the SW Scottish Highlands) they are mineralogically heterogeneous making them ideal for a study of mineralogical controls of metamorphic fluid flow. Their mineralogical heterogeneity reflects chemical heterogeneity arising from magmatic flow differentiation and spilitization, which occurred before greenschist facies metamorphism. Magmatic flow differentiation resulted in parts of the sill containing large crystals with no preferred alignment. Large (up to 3 cm) plagioclase phenocrysts were concentrated in the sill interior whereas large (up to 1 cm) amphibole (after pyroxene) grains formed cumulate layers close to the sill margins. These large randomly oriented crystals were replaced by an interface-coupled dissolution-precipitation mechanism. Replacement is constant volume and with hydration and carbonation affecting the cores of these minerals while the rims are remained intact and unaltered. This finding points to intra-granular metamorphic fluid flow. In contrast inter-granular metamorphic fluid flow was facilitated by mineral alignment on different scales. Pre-metamorphic spilitization, produced layers of epidote called segregations

  7. Geochemical, geochronological characterization and tectonic setting of the metamorphic rocks from the Biga Peninsula, NW Turkey

    NASA Astrophysics Data System (ADS)

    Şengün, F.; Tunç, Ä.°. O.; Yiǧitbaş, E.

    2012-04-01

    The Biga Peninsula in the northwest Turkey is one of the world's important natural laboratories to study geochronology due to having complex geology. The Biga Peninsula has different metamorphic basements including Kazdağ Massif, Çamlıca metamorphics, Kemer metamorphics and Karadağ Massif under cover of the Cenozoic volcano-sedimentary association. The Çamlıca metamorphic assemblage are one of the most critical regions for understanding of the geology of northwestern Turkey. The Çamlıca metamorphic association located on the westernmost part of Turkey is mainly composed of the Andıktası formation, the Dedetepe formation and the Salihler formation, from bottom to top. Metasedimentary rocks of the Çamlıca metamorphics have high SiO2 and medium Al2O3 and TiO2 values. The protolith of these metasediments is arkose-subarkose and greywacke. However, whole-rock geochemistry for the HP eclogite/blueschist within the Çamlıca metamorphics suggests that their protolith was basalt with high TiO2 and K2O-Na2O content and Nb/Y ratios. REE pattern and trace element contents of the HP eclogite/blueschist similar to typical MORB based on tectonic discrimination diagrams. The metavolcanic rocks occurring on the lowest part of the Çamlıca metamorphicassociation has andesitic composition with calc-alkaline character. All metavolcanic rocks in this unit cluster within the volcanic arc field. Zircon grains from metavolcanic rocks and HP eclogite/blueschists were dated by LA-ICPMS. Zircon ages of two metavolcanic samples yielded 328.6 ± 3.5 Ma and 343.2 ± 2.6 Ma, respectively. These ages are interpreted as the time of protolith crystallization of metavolcanic rocks. Moreover, zircon ages from HP eclogite/blueschist yielded 338 ± 1.8 Ma (Early Carboniferous) which is interpreted as the age of protolith crystallization of HP eclogite/blueschist. Geochemical and isotopic data indicate that Early Carboniferous Variscan ages within the Sakarya Zone may form the eastern

  8. Distribution and characteristics of metamorphic belts in the south- eastern Alaska part of the North American Cordillera

    USGS Publications Warehouse

    Brew, D.A.; Himmelberg, G.R.; Loney, R.A.; Ford, A.B.

    1992-01-01

    The Cordilleran orogen in south-eastern Alaska includes 14 distinct metamorphic belts that make up three major metamorphic complexes, from east to west: the Coast plutonic-metamorphic complex; the Glacier Bay-Chichagof plutonic-metamorphic complex; and the Chugach plutonic-metamorphic complex. Each of these complexes is related to a major subduction event. The metamorphic history of the Coast complex is lengthy and is related to the Late Cretaceous collision of the Alexander and Wrangellia terranes and the Gravina overlap assemblage to the west against the Stikine terrane to the east. The metamorphic history of the Glacier Bay-Chichagof complex is relatively simple and is related to the roots of a Late Jurassic to late Early Cretaceous island arc. The metamorphic history of the Chugach is complicated and developed during and after the Late Cretaceous collision of the Chugach terrane with the Wrangellia and Alexander terranes. -from Authors

  9. Possible genetic link between I-type granite and orogenic gold deposits in Egypt (metamorphic-magmatic interaction?)

    NASA Astrophysics Data System (ADS)

    Abd El Monsef, Mohamed

    2015-04-01

    The orogenic gold deposits are a distinctive type of deposits that revealed unique temporal and spatial association with an orogeny. Where, the system of gold veins and related ore minerals was confined to hydrothermal solutions formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens, with the respect to ongoing deep-crustal, subduction-related thermal processes. In Egypt, most of vein-type and dyke-type gold mineralization are restricted to granitic rocks or at least near of granitic intrusion that seems to have had an important influence on gold mineralization. Shear zone-related, mesothermal gold deposits of Fatira and Gidami mines in the northern Eastern Desert of Egypt are found within granitic bodies or at the contact between granites and metavolcanic rocks. The hosting-granitic rocks in Fatira and Gidami areas are mainly of granodioritic composition (I-Type granite) which is related to calc-alkaline magmatic series. However, Fatira granitoids were developed within island arc tectonic settings related to mature island arc system (Late-orogenic stage), at relatively low temperature (around 660° C) and medium pressure between (5 - 10 Kbar). On the other hand, Gidami granitoids were developed during the collision stage in continental arc regime related to active continental margin (Syn-orogeny), which were crystallized at relatively high temperature (700-720° C) and low pressure (around 0.1 Kbar). The ore mineralogy includes pyrite, chalcopyrite, sphalerite, covellite, ilmenite, goethite ± pyrrhotite ± pentlandite ± galena ± molybdenite. Native gold is detected only in Gidami mineralization as small inclusions within pyrite and goethite or as tiny grains scattered within quartz vein (in close proximity to the sulfides). In Fatira deposits, it is detected only by microprobe analysis within the crystal lattice of pyrite and jarosite. Fluid inclusions study for the mineralized

  10. Reaction-driven fracturing during replacement processes and metamorphism

    NASA Astrophysics Data System (ADS)

    Jamtveit, B.; Austrheim, H.; Raufaste, C.; Royne, A.; Malthe-Sorenssen, A.

    2008-12-01

    Hydration reactions involving igneous or high-grade metamorphic rocks often cause a significant increase in local volume at the site of reaction. Because such volatilization reactions are triggered by infiltration of external fluids and occur relatively far from thermodynamic equilibrium, they are often fast enough to produce sufficient stress perturbations to drive local fracturing. Microstructural studies show numerous examples of such small scale reaction-driven fracturing both within the reacting mineral grains and in the surrounding rock matrix. Small scale fractures often link up to form fracture networks that promotes further fluid infiltration, more reaction, more stress build up, more fracturing etc. etc. We believe that such self-accelerating coupling between reactions, fracturing, and fluid migration provides a first-order control on the rate of hydration of the Earth's crust both during metamorphism and during lower-temperature processes such as weathering. We present experimental studies that constrain under what conditions replacement reactions may cause fracturing near the reacting interface, both in synthetic and natural materials. Examples of natural reaction- driven fracturing at a wide range of scales will be presented with focus on serpentinization. Finally, a simple mechanical model will be presented to illustrate the most pertinent features of the hierarchical fragmentation process that arise from reaction-driven fracturing and demonstrate how this process may cause an overall acceleration of the hydration process. Relevant references Iyer, K., Jamtveit, B., Mathiesen, J., Malthe- Sørenssen, A., and Feder, J., 2007. Reaction-assisted hierarchical fracturing during serpentinization. Earth and Planetary Science Letters, 267, 503-516. Jamtveit, B, Austrheim, H., and Malthe-Sørensen, A., 2000. Accelerated hydration of the Earth's deep crust induced by stress perturbations. Nature, 408, 75-79 Jamtveit, B., Malthe-Sørenssen, A., and Kostenko, O

  11. Zircon and monazite response to prograde metamorphism in the Reynolds Range, central Australia

    NASA Astrophysics Data System (ADS)

    Rubatto, Daniela; Williams, Ian S.; Buick, Ian S.

    2001-01-01

    We report an extensive field-based study of zircon and monazite in the metamorphic sequence of the Reynolds Range (central Australia), where greenschist- to granulite-facies metamorphism is recorded over a continuous crustal section. Detailed cathodoluminescence and back-scattered electron imaging, supported by SHRIMP U-Pb dating, has revealed the different behaviours of zircon and monazite during metamorphism. Monazite first recorded regional metamorphic ages (1576 ± 5 Ma), at amphibolite-facies grade, at ˜600 °C. Abundant monazite yielding similar ages (1557 ± 2 to 1585 ± 3 Ma) is found at granulite-facies conditions in both partial melt segregations and restites. New zircon growth occurred between 1562 ± 4 and 1587 ± 4 Ma, but, in contrast to monazite, is only recorded in granulite-facies rocks where melt was present (≥700 °C). New zircon appears to form at the expense of pre-existing detrital and inherited cores, which are partly resorbed. The amount of metamorphic growth in both accessory minerals increases with temperature and metamorphic grade. However, new zircon growth is influenced by rock composition and driven by partial melting, factors that appear to have little effect on the formation of metamorphic monazite. The growth of these accessory phases in response to metamorphism extends over the 30 Ma period of melt crystallisation (1557-1587 Ma) in a stable high geothermal regime. Rare earth element patterns of zircon overgrowths in leucosome and restite indicate that, during the protracted metamorphism, melt-restite equilibrium was reached. Even in the extreme conditions of long-lasting high temperature (750-800 °C) metamorphism, Pb inheritance is widely preserved in the detrital zircon cores. A trace of inheritance is found in monazite, indicating that the closure temperature of the U-Pb system in relatively large monazite crystals can exceed 750-800 °C.

  12. Explosive volcanism, shock metamorphism and the K-T boundary

    NASA Technical Reports Server (NTRS)

    Desilva, S. L.; Sharpton, V. L.

    1988-01-01

    The issue of whether shocked quartz can be produced by explosive volcanic events is important in understanding the origin of the K-T boundary constituents. Proponents of a volcanic origin for the shocked quartz at the K-T boundary cite the suggestion of Rice, that peak overpressures of 1000 kbars can be generated during explosive volcanic eruptions, and may have occurred during the May, 1980 eruption of Mt. St. Helens. Attention was previously drawn to the fact that peak overpressures during explosive eruptions are limited by the strength of the rock confining the magma chamber to less than 8 kbars even under ideal conditions. The proposed volcanic mechanisms for generating pressures sufficient to shock quartz are further examined. Theoretical arguments, field evidence and petrographic data are presented showing that explosive volcanic eruptions cannot generate shock metamorphic features of the kind seen in minerals at the K-T boundary.

  13. Interaction of low-grade metamorphic coals with methanol

    SciTech Connect

    S.I. Zherebtsov

    2007-06-15

    How conditions of alkylation of low-grade metamorphic coals with methanol in the presence of benzenesulfonic acid influence the yield of extractable matter was experimentally studied and relevant regression equations were obtained. It was shown that catalytic methylation considerably increases the yield of the extractable matter, as well as reducing the thermal stability of modified samples and alters the elemental composition of the samples and their extracts. A possible mechanism of coal methylation is discussed on the basis of regression models and experimental results. The interaction of the coal matter with the alkylating agent presumably involves the formation of the carbocation and its reaction with the coal organic matter. Both depolymerization reactions and the addition reactions of a portion of extractable compounds, the alkylating agent, and the catalyst with the high-molecular mass coal matrix take place.

  14. Metamorphism and gold mineralization in the Blue Ridge, Southernmost Appalachians

    USGS Publications Warehouse

    Stowell, H.H.; Lesher, C.M.; Green, N.L.; Sha, P.; Guthrie, G.M.; Sinha, A.K.

    1996-01-01

    Lode gold mineralization in the Blue Ridge of the southernmost Appalachians is hosted by metavolcanic rocks (e.g., Anna Howe mine, AL; Royal Vindicator mine, GA), metaplutonic rocks (e.g., Hog Mountain mine, AL), and metasedimentary rocks (e.g., Lowe, Tallapoosa, and Jones Vein mines, AL). Most gold occurs in synkinematic quartz ?? plagioclase ?? pyrite ?? pyrrhotite ?? chlorite veins localized along polydeformational faults that juxtapose rocks with significantly different peak metamorphic mineral assemblages. Mineralogy, chemistry, and O and H isotope studies suggest that the three types of host rocks have undergone differing amounts and types of alteration during mineralization. Limited wall-rock alteration in metavolcanic- and metasediment-hosted deposits, and relatively extensive wall-rock alteration in granitoid-hosted deposits, suggests that most deposits formed from fluids that were close to equilibrium with metavolcanic and metasedimentary rocks. Stable isotope compositions of the fluids calculated from vein minerals and vein selvages are consistent with a predominantly metasedimentary fluid source, but vary from deposit to deposit (-22 to -47??? ??D, 4-5??? ??18O, and 5-7??? ??34S at Anna Howe and Royal Vindicator; -48 to -50??? ??D, 9-13??? ??18O, and ca. 19??? ??34S at Lowe and Jones Vein; and -22 to -23??? ??D, 8-11??? ??18O, 9-10??? ??34S, and -6 ??13C at Hog Mountain). Silicate mineral thermobarometry of vein, vein selvage, and wall-rock mineral assemblages indicate that mineralization and regional metamorphism occured at greenschist to amphibolite facies (480?? ?? 75??C at Anna Howe, 535?? ?? 50??C at 6.4 ?? 1 kbars at Lowe, 530?? ?? 50??C at 6.9 ?? 1 kbars at Tallapoosa, and 460?? ?? 50??C at 5.5 ?? 1 kbars at Hog Mountain). Oxygen isotope fractionation between vein minerals and selvage minerals consistently records equilibration temperatures that are similar to or slightly lower than those estimated from silicate thermometry. Auriferous veins

  15. Age of granites of Wrangel Island metamorphic complex

    NASA Astrophysics Data System (ADS)

    Luchitskaya, Marina; Sergeev, Sergey; Sokolov, Sergey; Tuchkova, Marianna

    2014-05-01

    Within huge arctic shelf of Eastern-Siberian and Chukchi seas the metamorphic basement (Wrangel complex, Berri Formation) is exposed only on the Wrangel Island. There are different points of views on the age of metamorphic rocks of Wrangel complex (Berri Formation): (1) Neoproterozoic (Kameneva, 1970; Ageev, 1979; Kos'ko et al., 1993, 2003), (2) Devonian (Til'man et al., 1964, 1970; Ganelin, 1989). Metamorphic basement is represented by stratified complex, composed of dislocated metavolcanic, metavolcaniclastic and metasedimentary rocks (schists, metasandstones, metaconglomerated) with single lenses and layers of carbonate rocks (Wrangel Island…, 2003). Among basement rocks in the central part of Wrangel Island there are felsic intrusive bodies. They form small tabular bodies from tens centimeters to 70-80 meters in thickness, rarely dikes and small stocks (up to 20 x 30 m) and are composed of granite-porphyres, rarely muscovite porphyr-like granites and granosyenites (Wrangel Island…, 2003). The age of intrusions allow to determine the age of basement formation. Earlier the age of intrusions was determined by different methods and correlated to the boundary between Neoproterozoic and Paleozoic: K-Ar 570-603 Ma, Pb-Pb 590±50 Ma (S.M. Pavlov, Institute of Precambrian Geology and Geochronology, USSR Academy of Sciences), Rb-Sr 475±31 Ma (I.M.Vasil'eva, Institute of Precambrian Geology and Geochronology, USSR Academy of Sciences), U-Pb 609, 633, 677 Ma (Geological Survey of Canada) (Wrangel Island…, 2003; Kos'ko et al., 1993; Cecile et al., 1991). In the lower part of metamorphic rocks of Wrangel complex there are conformable tabular bodies of gneissosed and foliated granitoides. The latter are meramorphosed and transformed in biotite-muscovite-feldspar-quartz-sericite and muscovite-feldspar-quartz-sericite gneisses and schists, where relics of primary minerals (quartz, plagioclase, potassium feldspar, rarely biotite and muscovite) and equigranular granitic

  16. Metamorphic reactions in mesosiderites - Origin of abundant phosphate and silica

    NASA Technical Reports Server (NTRS)

    Harlow, G. E.; Delaney, J. S.; Prinz, M.; Nehru, C. E.

    1982-01-01

    In light of a study of the Emery mesosiderite, it is determined that the high modal abundances of merrillite and tridymite in most mesosiderites are attributable to redox reactions between silicates and P-bearing Fe-Ni metal within a limited T-fO2 range at low pressure. The recalculated amounts of dissolved P and S in the metallic portion of Emery reduce the metal liquidus temperature to less than 1350 C, and the solidus to less than 800 C, so that the mixing of liquid metal with cold silicates would have resulted in silicate metamorphism rather than melting. This redox reaction and redistribution of components between metal and silicates illuminates the complexities of mesosiderite processing, with a view to the recalculation of their original components.

  17. Anatexis of garnet amphibolites from a subduction zone metamorphic terrane

    SciTech Connect

    Sorensen, S.S.; Barton, M.D.; Ernst, W.G.

    1985-01-01

    Concomitant rehydration, metasomatism and amphibolitization of eclogite blocks from a mafic/ultramafic complex of the Catalina Schist terrane, southern California, at estimated metamorphic P approx. 8-12 kb, T approx. 600/sup 0/-700/sup 0/C was apparently accompanied by partial melting of some blocks. Mobilizates of An approx./sub 10-20/ plagioclase (PL) +/- zoisite (ZO) + quartz (QZ) + celadonitic (Si approx. 3.3 p.f.u.) white mica (WM) +/- tourmaline range from stringers and dikelets (approx. 1 cm-0.5 m) in migmatitic amphibolite blocks to dikes approx. 30 m x 3 m which intrude the surrounding, locally enstatite + chlorite +/- talc +/- aluminous actinolite +/- anthophyllite-bearing ultramafic matrix. The uniform phase proportions and the coarse-grained (PL to approx. 20 cm) pegmatitic, graphic, and myrmekitic textures displayed by the dikes and dikelets suggest that they crystallized from silicate melts. WM and ZO appear to be magmatic phases. Fe-rich GT is migmatitic portions of blocks exhibits higher Mg/(Mg + Ca) p.f.u. than GT in restitic portions of blocks; rims are richer in Mg than cores. Field relations, microprobe mineral chemistry, and bulk compositions suggest the pegmatites are low fractions of amphibolite-derived partial melt. Abundant fluid inclusions occur in GT, QZ, PL and clinopyroxene. T/sub h/ for primary H/sub 2/O-rich, low salinity L + V inclusions in GT and QZ from a migmatite range from 136-169/sup 0/C; estimates of T limits for entrapment are 530-640/sup 0/C at 8 kb, 650-780/sup 0/C at 10 kb. H/sub 2/O-rich fluids evidently enabled metasomatism, amphibolitization, and anatexis of (originally) eclogitic rocks at the P-T conditions reflected by the metamorphic mineral assemblages.

  18. Origin of metamorphic core complexes and detachment faults

    NASA Astrophysics Data System (ADS)

    Wu, G.; Lavier, L. L.

    2013-12-01

    Origin of metamorphic core complexes and detachment faults Guangliang Wu1,2, Luc L. Lavier1,2 1 Institute for Geophysics, University of Texas at Austin, TX 78758, USA 2 Department of Geological Sciences, University of Texas at Austin, TX 78712, USA Metamorphic core complexes (MCCs) and detachment faults are widely observed in collapsing orogens, such as Western US Cordillera, the Aegean and Papua New Guinea. A theory for the origin of MCCs has to provide: i) a viable mechanism to bring deeper crustal material to the surface, ii) a scenario that allows slip on low-angle detachment faults, and iii) a viable mechanism to form a flat Moho at a certain stage of evolution. However, previous models ignored at least one of these three requirements. Using thermo-mechanical models constrained by geological and geophysical observation, we simulated MCCs and detachment faults in the context of collapsing orogens with preexisting shear zones and middle crust of variable strength. We found that MCCs and detachment faults are natural products of gravity driven middle crustal extrusion and exhumation and strong crustal decoupling along the preexisting shear zones in a favorable state of stress in collapsing orogens. Based on previous geological and geophysical observations and our numerical simulations, we categorized MCCs into four types: i) massifs, such as Menderes massif and SW Rhodope massif, ii) single large asymmetric MCC (classic MCC), such as Whipple mountains and Snake Range Mountains, Western US Cordillera and Crete and Cyclades, the Aegean, iii) multiple less evolved MCCs, such as Black Mountains turtlebacks, and iv) subsurface ';MCC', such as interpreted at the Adriatic coast. We also recognized two types of detachment faults: one being listric fault transitioning to a convex upward shear zone at greater depth and the other a shallow exhumed upward convex shear zone. Our new models successfully predict many MCCs and detachment faults known to date.

  19. Contact Metamorphic Halocarbon Production in the Siberian Traps

    NASA Astrophysics Data System (ADS)

    Fristad, K. E.; Schmidbauer, N.; Svensen, H.; Polozov, A. G.; Planke, S.

    2012-12-01

    The Siberian Trap flood basalts erupted into and through the Siberian craton around 252 million years ago and emplaced sill intrusions up to hundreds of meters thick into hydrocarbon-bearing evaporite deposits of the Tunguska Basin in Eastern Siberia. Large volumes of carbon gases are hypothesized to have been produced in the aureoles around these intrusions leading to build-up and catastrophic release of toxic greenhouse gases to the end-Permian atmosphere. The crustal volatiles released through this process are believed to have contributed to environmental crisis and the end-Permian mass extinction. We have conducted a series of laboratory pyrolysis experiments on hydrocarbon-bearing Tunguska Basin evaporite samples in order to assess the composition and quantity of volatile compounds generated during contact metamorphic heating of this rock. The experiments were conducted on natural samples from a drill core at approximately 850 meters depth at Nepa in Siberia and span approximately 140 meters of evaporitic country rock around a 40 meter thick sill intrusion. The mineralogy of the samples is predominantly halite and anhydrite and the samples span the range of thermal conditions experienced in the aureole after the sill emplacement event. Using a mill/heating cell coupled to a Medusa gas chromatograph mass spectrometer, we measured the volatile content of the fluid inclusions as well as the volatiles produced by heating of the samples. Sample heating produced a spectrum of carbon-, fluorine-, and chlorine-bearing gases in concentrations orders of magnitude higher than that found in the fluid inclusions and in the modern atmosphere. Our experimental results illustrate the significance of contact metamorphism for toxic gas production, including halocarbons, in the Tunguska Basin sediments at the end-Permian.

  20. Detrital zircon geochronology of the Tananao Metamorphic Complex, Taiwan

    NASA Astrophysics Data System (ADS)

    Huang, Y. C.; Chen, W. S.; Feng, H. T.; Liu, C. H.; Chung, S. L.; Lee, Y. H.

    2014-12-01

    The oldest rock of the Tananao Metamorphic Complex exposed at the Backbone Range which consists of marble, schist, and gneiss. According to the stratigraphy and structural analysis, the Complex in the ascending order can be divided into Chiuchu Marble, Paiyang Schist with Kuyuan Schist, and Pilu Formation. Based on Sr isotope dating, it is speculated that the formation age of Chiuchu Marble is closed to 250±20 Ma. Using the zircon U-Pb dating, the magnetic age of gneiss (I-type granite) yields 105- 86 Ma. The stratigraphic age of schist is difficult to define because of fossils are poorly-preserved. In our study, we use the detrital zircon U-Pb dating, by LA-ICPMS, to yield the maximum depositional age of the schist formation. We analyze fifteen samples in this study. The depositional age of the Kuyuan and Paiyang Schists would be not older than late Cretaceous, and the depositional age of the Pilu Formation may have formed in late Cretaceous and younger than Kuyuan and Paiyang Schists. Results from the above mentioned, we are interpreted as the tectonic setting of the Tananao Metamorpic Complex. The region was located on a passive continental margin that formed carbonate platform deposits during the late Permian period. The clastic sediments were unconformably deposited on Chiuchu Marble during the early Cretaceous. Then the paleo-Pacific plate subducted to the Cathaysia Block forming the granite at about 105-86 Ma. Afterwards, the clastic sediments were deeply buried caused by continuing subduction formed as schist rock. The metamorphic event is known as the Nanao orogeny.

  1. Metamorphism of Triassic sediments from the Dunbarton Basin, South Carolina

    SciTech Connect

    Snipes, D.S.; Warner, R.D. . Earth Sciences Dept.); Price, V. Jr. ); Thayer, P. . Geology Dept.)

    1993-03-01

    Modal analyses and microprobe studies were performed on eight core samples obtained from the US Geological Survey Well A1 324. The well is situated in the southern part of the buried Triassic Dunbarton Basin, about 1 km south of the US Department of Energy's Westinghouse Savannah River Company Site. The samples came from an interval of 407.0--413.4 m beneath the land surface. At the well site, Triassic red beds are overlain by Late Cretaceous and Tertiary sediments which have an aggregate thickness of 408 m. The sample from a depth of 407 m is a weathered, poorly sorted, clayey sandstone from the basal portion of the Late Cretaceous Cape Fear Formation. This specimen is not metamorphosed; whereas, the Triassic specimens taken from an interval of 411.6--413.4 m exhibit evidence of thermal metamorphism as well as hydrothermal alteration. In hand specimen, three of the samples (412.8--413.4 m) resemble hornfelses. These samples exhibit decussate texture. Results of modal analyses of the two deepest specimens follow: plagioclase (43-52%), quartz (9-23%), chlorite (22-29%), epidote (1-6%), hematite (3-4%), and magnetite (2-3%). Relict detrital quartz grains, especially the finer ones, are mostly angular-to-subangular and the grain boundaries show little evidence of rounding. The authors feel that hydrothermal alteration was the principal metamorphic process. This belief is supported by the fact that most of the plagioclase has undergone extensive sericitization. In addition, the presence of abundant chlorite together with a minor amount of epidote supports this interpretation. The alteration halo extends upward for 1.8 m. This interpretation is based on the observation that two Triassic arkose sandstone specimens (411.6 m, 412.2 m) contain clouded, slightly sericitized K-feldspar and plagioclase grains in a matrix of red-colored smectite.

  2. Ile-Phe Dipeptide Self-Assembly: Clues to Amyloid Formation

    PubMed Central

    de Groot, Natalia Sánchez; Parella, Teodor; Aviles, Francesc X.; Vendrell, Josep; Ventura, Salvador

    2007-01-01

    Peptidic self-assembled nanostructures are said to have a wide range of applications in nanotechnology, yet the mechanistic details of hierarchical self-assembly are still poorly understood. The Phe-Phe recognition motif of the Alzheimer's Aβ peptide is the smallest peptide able to assemble into higher-order structures. Here, we show that the Ile-Phe dipeptide analog is also able to self-associate in aqueous solution as a transparent, thermoreversible gel formed by a network of fibrillar nanostructures that exhibit strong birefringence upon Congo red binding. Besides, a second dipeptide Val-Phe, differing only in a methyl group from the former, is unable to self-assemble. The detailed analysis of the differential polymeric behavior of these closely related molecules provides insight into the forces triggering the first steps in self-assembly processes such as amyloid formation. PMID:17172307

  3. Ile-phe dipeptide self-assembly: clues to amyloid formation.

    PubMed

    de Groot, Natalia Sánchez; Parella, Teodor; Aviles, Francesc X; Vendrell, Josep; Ventura, Salvador

    2007-03-01

    Peptidic self-assembled nanostructures are said to have a wide range of applications in nanotechnology, yet the mechanistic details of hierarchical self-assembly are still poorly understood. The Phe-Phe recognition motif of the Alzheimer's Abeta peptide is the smallest peptide able to assemble into higher-order structures. Here, we show that the Ile-Phe dipeptide analog is also able to self-associate in aqueous solution as a transparent, thermoreversible gel formed by a network of fibrillar nanostructures that exhibit strong birefringence upon Congo red binding. Besides, a second dipeptide Val-Phe, differing only in a methyl group from the former, is unable to self-assemble. The detailed analysis of the differential polymeric behavior of these closely related molecules provides insight into the forces triggering the first steps in self-assembly processes such as amyloid formation. PMID:17172307

  4. Anthropometric Indices Associated with Variation in Cardiovascular Parameters among Primary School Pupils in Ile-Ife

    PubMed Central

    Abiodun, Adedeji G.; Egwu, Michael O.; Adedoyin, Rufus A.

    2011-01-01

    Purpose. This study investigated the anthropometric indices associated with variations in cardiovascular parameters among primary school pupils in Ile-Ife. Method. One thousand and twenty-six pupils (age range 6–14 years, mean age 10.12 years) from ten schools were recruited with parents' informed consent. Anthropometric (Height (Ht), Weight (Wt), Abdominal Circumference (AC)) and cardiovascular (Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Heart Rate (HR)) parameters were measured using standard instruments and procedures. Blood pressure (BP) was measured after ten minutes of quiet sitting. Body Mass Index (BMI), Rate Pressure Product (RPP) and Pulse Pressure (PP) were estimated. Results. Age, Ht, Wt, BMI, and AC correlated significantly (P < .01) with BP and PP. AC and BMI were predictors of BP, HR, RPP, and PP. Conclusion. Significant correlations exist between age, Ht, Wt, BMI, AC, and BP with weight being a more viable predictor of SBP and age a more viable predictor of DBP. PMID:21747972

  5. Switching a newly discovered lactonase into an efficient and thermostable phosphotriesterase by simple double mutations His250Ile/Ile263Trp.

    PubMed

    Luo, Xiao-Jing; Kong, Xu-Dong; Zhao, Jian; Chen, Qi; Zhou, Jiahai; Xu, Jian-He

    2014-10-01

    OPHC2 is a thermostable organophosphate (OP) hydrolase in the β-lactamase superfamily. OPs are highly toxic synthetic chemicals with no natural analogs. How did OPHC2 acquire phosphotriesterase (PTE) activity remained unclear. In this study, an OPHC2 analogue, PoOPH was discovered from Pseudomonas oleovorans exhibiting high lactonase and esterase activities and latent PTE activity. Sequence analysis revealed conserved His250 and Ile263 and site-directed mutagenesis at these crucial residues enhanced PTE activity. The best variant PoOPHM2 carrying H250I/I263W mutations displayed 6,962- and 106-fold improvements in catalytic efficiency for methyl-parathion and ethyl-paraoxon degradation, whereas the original lactonase and esterase activities decreased dramatically. A 1.4 × 10(7) -fold of specificity inversion was achieved by only two residue substitutions. Significantly, thermostability of the variants was not compromised. Crystal structure of PoOPHM2 was determined at 2.25 Å resolution and docking studies suggested that the two residues in the binding pocket determine substrate recognition. Lastly, new organophosphorus hydrolases (OPHs) were discovered using simple double mutations. Among them, PpOPHM2 from Pseudomonas putida emerged as a new promising OPH with very high activity (41.0 U mg(-1) ) toward methyl-parathion. Our results offer a first scrutiny to PTE activity evolution of OPHs in β-lactamase superfamily and provide efficient and robust enzymes for OP detoxification. PMID:24771278

  6. Association between CYP1A1 Ile462Val Polymorphism and Oral Squamous Cell Carcinoma Susceptibility: Evidence from 13 Investigations

    PubMed Central

    Yang, Xiao-Lei; Xie, Shang; Jiang, Yi-Yan; Shi, Chang; Cai, Zhi-Gang; Chen, Su-Xiu

    2015-01-01

    CYP1A1 Ile462Val polymorphism might play a key role in pathogenesis of oral squamous cell carcinoma (OSCC). Many case-control studies have investigated the association between CYP1A1 Ile462Val polymorphism and OSCC susceptibility. However, the conclusions are inconsistent. To aim a convincible conclusion, we carried out a meta-analysis to systematically evaluate the association of CYP1A1 Ile462Val polymorphism with OSCC susceptibility. We searched Pubmed, Web of Science, Ovid and Embase databases for available publications. The odds ratio (OR) with the corresponding 95% confidence interval (95% CI) was carried out to estimate the association. A total of 13 papers including 1468 cases and 2183 controls were included, a significant increased OSCC risk was observed in recessive model (OR=1.64, 95% CI=1.08-2.49), but not other genetic models. Our results suggest that the homozygous variant of CYP1A1 Ile462Val might be a risk factor of OSCC. PMID:25767599

  7. The first Caucasian patient with p.Val122Ile mutated-transthyretin cardiac amyloidosis treated with isolated heart transplantation.

    PubMed

    Ammirati, Enrico; Marziliano, Nicola; Vittori, Claudia; Pedrotti, Patrizia; Bramerio, Manuela A; Motta, Valentina; Orsini, Francesco; Veronese, Silvio; Merlini, Piera A; Martinelli, Luigi; Frigerio, Maria

    2012-06-01

    Effective treatments for mutated transthyretin (TTR)-related cardiac amyloidosis are limited. Heart transplantation or combined liver-heart transplantation are the most successful options, although results rely on underline mechanism and systemic nature of the disease. In this report, we present the first case of a Caucasian patient with the p.Val122Ile mutated TTR-related cardiac amyloidosis treated with heart transplantation due to this gene mutation frequent in Afro-Americans with a prevalent isolated heart involvement. The choice of isolated heart transplantation instead of combined heart and liver transplantations was based on (1) severe and progressive cardiac disease, (2) evidence of a gene mutation generally associated with isolated cardiac disease and (3) absence of relevant extra-cardiac involvement (with the possible exception of mild peripheral neuropathy). In any case, the very short post-transplant observation period of 10 months does not allow any conclusions on the long-term course of the presented strategy. Finally, it is the first European Caucasian family with the p.Val122Ile TTR mutation that has been described. Till now, very few Caucasian cases of p.Val122Ile mutated TTR-related cardiac amyloidosis have been reported. The patient and some members of his family also had mild peripheral neuropathy suggesting a regional phenotypic heterogeneity of European Caucasian TTR p.Val122Ile. PMID:22449240

  8. Chronic Airflow Obstruction in a Black African Population: Results of BOLD Study, Ile-Ife, Nigeria.

    PubMed

    Obaseki, Daniel O; Erhabor, Gregory E; Gnatiuc, Louisa; Adewole, Olufemi O; Buist, Sonia A; Burney, Peter G

    2016-01-01

    Global estimates suggest that Chronic Obstructive Pulmonary Disease (COPD) is emerging as a leading cause of death in developing countries but there are few spirometry-based general population data on its prevalence and risk factors in sub-Saharan Africa. We used the Burden of Obstructive Lung Disease (BOLD) protocol to select a representative sample of adults aged 40 years and above in Ile-Ife, Nigeria. All the participants underwent spirometry and provided information on smoking history, biomass and occupational exposures as well as diagnosed respiratory diseases and symptoms. Chronic Airflow Obstruction (CAO) was defined as the ratio of post-bronchodilator (BD) one second Forced Expiratory Volume (FEV1) to Forced Vital Capacity (FVC) below the lower limit of normal (LLN) of the population distribution for FEV1/FVC. The overall prevalence of obstruction (post-BD FEV1/FVC < LLN) was 7.7% (2.7% above LLN) using Global Lung Function Initiative (GLI) equations. It was associated with few respiratory symptoms; 0.3% reported a previous doctor-diagnosed chronic bronchitis, emphysema or COPD. Independent predictors included a lack of education (OR 2.5, 95% CI: 1.0, 6.4) and a diagnosis of either TB (OR 23.4, 95% CI: 2.0, 278.6) or asthma (OR 35.4, 95%CI: 4.9, 255.8). There was no association with the use of firewood or coal for cooking or heating. The vast majority of this population (89%) are never smokers. We conclude that the prevalence of CAO is low in Ile-Ife, Nigeria and unrelated to biomass exposure. The key independent predictors are poor education, and previous diagnosis of tuberculosis or asthma. PMID:26451840

  9. The role of seabirds of the Iles Eparses as reservoirs and disseminators of parasites and pathogens

    NASA Astrophysics Data System (ADS)

    McCoy, Karen D.; Dietrich, Muriel; Jaeger, Audrey; Wilkinson, David A.; Bastien, Matthieu; Lagadec, Erwan; Boulinier, Thierry; Pascalis, Hervé; Tortosa, Pablo; Le Corre, Matthieu; Dellagi, Koussay; Lebarbenchon, Camille

    2016-04-01

    The role of birds as reservoirs and disseminators of parasites and pathogens has received much attention over the past several years due to their high vagility. Seabirds are particularly interesting hosts in this respect. In addition to incredible long-distance movements during migration, foraging and prospecting, these birds are long-lived, site faithful and breed in dense aggregations in specific colony locations. These different characteristics can favor both the local maintenance and large-scale dissemination of parasites and pathogens. The Iles Eparses provide breeding and feeding grounds for more than 3 million breeding pairs of seabirds including at least 13 species. Breeding colonies on these islands are relatively undisturbed by human activities and represent natural metapopulations in which seabird population dynamics, movement and dispersal can be studied in relation to that of circulating parasites and pathogens. In this review, we summarize previous knowledge and recently-acquired data on the parasites and pathogens found in association with seabirds of the Iles Eparses. These studies have revealed the presence of a rich diversity of infectious agents (viruses, bacteria and parasites) carried by the birds and/or their local ectoparasites (ticks and louse flies). Many of these agents are widespread and found in other ecosystems confirming a role for seabirds in their large scale dissemination and maintenance. The heterogeneous distribution of parasites and infectious agents among islands and seabird species suggests that relatively independent metacommunities of interacting species may exist within the western Indian Ocean. In this context, we discuss how the patterns and determinants of seabird movements may alter parasite and pathogen circulation. We conclude by outlining key aspects for future research given the baseline data now available and current concerns in eco-epidemiology and biodiversity conservation.

  10. Low- to high-grade metamorphic transition in the Southern part of Karnataka Nucleus, India

    NASA Astrophysics Data System (ADS)

    Naqvi, S. M.

    The southern part of Karnataka Nucleus has a strong imprint of 2.6 Ga metamorphism. This has affected the schist belts of Karnataka Nucleus from greenschist to upper amphibolite facies. The higher grades of metamorphism are in the Holenarasipur, Nuggihalli, Krishnarajpet, Hadnur and Melkote schist belts. In the high grade transition zone, around Sargur only keels of schist belts are preserved and occur as highly dismembered, disconnected belts with the top and bottom of the stratigraphic column obliterated due to high grade metamorphism and accompanying migmatization. Absence of high-grade metamorphic minerals in the sediments of the Dharwar schist belts supports the contention that high grade metamorphism post-dated the Dharwar sedimentation and occurred around 2.6 Ga ago. Sargur type metamorphism occurred at upper crustal levels and charnockite type metamorphism occurred in lower crustal levels. The P-T conditions for the mineral assemblage in metapelites of Sargur Group indicate burial depths up to at least 15 km suggesting that they were subducted and later obducted during the development of Early Proterozoic Mobile Belt along the southern border of the Karnataka Nucleus.

  11. Late miocene/pliocene origin of the inverted metamorphism of the Central Himalaya

    SciTech Connect

    Harrison, T.M.; Ryerson, F.J.; LeFort, P.; Yin, A. Lovera, O.M.

    1997-01-01

    The spatial association of intracontinental thrusting and inverted metamorphism, recognized in the Himalaya more than a century ago, has inspired continuing efforts to identify their causal relationship. Perhaps the best known sequence of inverted metamorphism is that found immediately beneath the Himalayan Main Central Thrust (MCT), generally thought to have been active during the Early Miocene. It has been widely assumed that the pattern of inverted metamorphism also developed at that time. Using a new approach, in situ Th-Pb dating of monazite included in garnet, we have discovered that the peak metamorphic recrystallization recorded in the footwall of the MCT fault occurred at ca. 5 Ma. The apparent inverted metamorphism resulted from activation of a broad shear zone beneath the MCT zone which juxtaposed two right-way-up metamorphic sequences. Recognition of this remarkably youthful phase of metamorphism resolves outstanding problems in Himalayan tectonics, such as why the MCT (and not the more recently initiated thrusts) marks the break in slope of the present day mountain range, and transcends others, such as the need for exceptional conditions to explain Himalayan anatexis.

  12. Age and tectonic implications of some low-grade metamorphic rocks from the Yucatan Channel

    USGS Publications Warehouse

    Vedder, J.G.; MacLeod, N.S.; Lanphere, M.A.; Dillon, William P.

    1973-01-01

    Phyllite and marble dredged from the lower part of the continental slope between Cuba and the Yucatan Peninsula seem to support the contention that a pre-early Tertiary metamorphic belt extends from the western Greater Antilles into northern Central America. The minimum K-Ar ages derived from the samples suggest that the metamorphic event was pre-Late Cretaceous, and evaluation of the K-Ar data implies that this metamorphic event is not older than Late Jurassic. Greater antiquity, however, is inferred from structural and stratigraphic relations in British Honduras, where the latest regional metamorphic event was post-Early Permian and pre-Middle Jurassic.  Rifting and extension related to plate motions along the British Honduras Quintana Roo margin through Mesozoic and earliest Cenozoic time presumably would preclude extensive regional metamorphism, permitting only limited development of schistose rocks there during that interval. The timing of metamorphic events in western Cuba is uncertain, but a pre-Middle Jurassic episode possibly is reflected in the phyllite and marble terranes of Isla de Pinos and Sierra de Trinidad. Local incipient metamorphism of Early and Middle Jurassic strata in the Sierra de los Organos may have resulted from severe tectonism that began in Late Cretaceous time and diminished in the Eocene.

  13. Low- to high-grade metamorphic transition in the Southern part of Karnataka Nucleus, India

    NASA Technical Reports Server (NTRS)

    Naqvi, S. M.

    1988-01-01

    The southern part of Karnataka Nucleus has a strong imprint of 2.6 Ga metamorphism. This has affected the schist belts of Karnataka Nucleus from greenschist to upper amphibolite facies. The higher grades of metamorphism are in the Holenarasipur, Nuggihalli, Krishnarajpet, Hadnur and Melkote schist belts. In the high grade transition zone, around Sargur only keels of schist belts are preserved and occur as highly dismembered, disconnected belts with the top and bottom of the stratigraphic column obliterated due to high grade metamorphism and accompanying migmatization. Absence of high-grade metamorphic minerals in the sediments of the Dharwar schist belts supports the contention that high grade metamorphism post-dated the Dharwar sedimentation and occurred around 2.6 Ga ago. Sargur type metamorphism occurred at upper crustal levels and charnockite type metamorphism occurred in lower crustal levels. The P-T conditions for the mineral assemblage in metapelites of Sargur Group indicate burial depths up to at least 15 km suggesting that they were subducted and later obducted during the development of Early Proterozoic Mobile Belt along the southern border of the Karnataka Nucleus.

  14. Rock relationships in the Mogok metamorphic belt, Tatkon to Mandalay, central Myanmar

    NASA Astrophysics Data System (ADS)

    Mitchell, A. H. G.; Htay, Myint Thein; Htun, Kyaw Min; Win, Myint Naing; Oo, Thura; Hlaing, Tin

    2007-03-01

    The Mogok metamorphic belt (MMB), over 1450 km long and up to 40 km wide, consists of regionally metamorphosed rocks including kyanite and sillimanite schists and granites lying along the Western margin of the Shan Plateau in central Myanmar and continuing northwards to the eastern Himalayan syntaxis. Exposures in quarries allow correlation of Palaeozoic meta-sedimentary, early Mesozoic meta-igneous and late Mesozoic intrusive rocks within a 230 km long northerly-trending segment of the MMB, from Tatkon to Kyanigan north of Mandalay, and with the Mogok gemstone district 100 km to the northeast. Relationships among the metamorphic and intrusive rocks, with sparse published radiometric age controls, indicate at least two metamorphic events, one before and one after the intrusion of Late Jurassic to early Cretaceous calc-alkaline rocks. These relationships can be explained by either of two possible tectonic histories. One, constrained by correlation of mid-Permian limestones across Myanmar, requires early Permian and early Jurassic regional metamorphic events, prior to an early Tertiary metamorphism, in the western part of but within a Shan-Thai - western Myanmar block. The second, not compatible with a single laterally continuous Permian limestone, requires pre-Upper Jurassic regional metamorphism and orogenic gold mineralization in the Mergui Group and western Myanmar, early Cretaceous collision of an east-facing Mergui-western Myanmar island arc with the Shan Plateau, and early Tertiary metamorphism in the MMB related to reversal in tectonic polarity following the arc-Plateau collision.

  15. Complement factor H Val62Ile variant and risk of age-related macular degeneration: A meta-analysis

    PubMed Central

    Yuan, Dongqing; Yang, Qin; Liu, Xiaoyi; Yuan, Donglan; Yuan, Songtao; Xie, Ping

    2013-01-01

    Purpose To evaluate the precise association of complement factor H (CFH) Val62Ile polymorphism with age-related macular degeneration (AMD) susceptibility. Methods We performed a meta-analysis using databases including PubMed, EMBASE, and Web of Science to find relevant studies. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using fixed-effect and random-effects models. The inconsistency index (I2) was used to assess heterogeneity. Funnel plots and Egger’s test were used to evaluate publication bias. Sensitivity analysis was also performed. Results Fourteen studies including 4,438 patients with AMD and 6,099 controls based on the search criteria were involved in the meta-analysis. In overall populations, the pooled OR1 for genotype GA+GG versus homozygous genotype AA was 2.28 (95% confidence interval (CI): 1.48–3.52), the OR2 of heterozygous genotype GA versus AA was 1.58 (95% CI: 1.13–2.19), the OR3 of homozygous genotype GG versus AA was 2.90 (95% CI: 1.95–4.30), and the OR4 of allele G versus A was 1.77 (95% CI: 1.43–2.21). In Asian populations, our results provided substantial evidence that the Val62Ile variant was significantly associated with AMD (OR4=1.85, 95% CI: 1.63–2.09). However, in Caucasian populations, no significant association of Val62Ile with AMD was established in all circumstances. Conclusions Our analysis provides substantial evidence that the Val62Ile variant is significantly associated with AMD in Asian populations. However, our results have demonstrated no link between the Val62Ile polymorphism and AMD in Caucasian populations. PMID:23441108

  16. Dynamics and Conformational Studies of TOAC Spin Labeled Analogues of Ctx(Ile21)-Ha Peptide from Hypsiboas albopunctatus

    PubMed Central

    Vicente, Eduardo F.; Basso, Luis Guilherme M.; Cespedes, Graziely F.; Lorenzón, Esteban N.; Castro, Mariana S.; Mendes-Giannini, Maria José S.; Costa-Filho, Antonio José; Cilli, Eduardo M.

    2013-01-01

    Antimicrobial peptides (AMPs) isolated from several organisms have been receiving much attention due to some specific features that allow them to interact with, bind to, and disrupt cell membranes. The aim of this paper was to study the interactions between a membrane mimetic and the cationic AMP Ctx(Ile21)-Ha as well as analogues containing the paramagnetic amino acid 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) incorporated at residue positions n = 0, 2, and 13. Circular dichroism studies showed that the peptides, except for [TOAC13]Ctx(Ile21)-Ha, are unstructured in aqueous solution but acquire different amounts of α-helical secondary structure in the presence of trifluorethanol and lysophosphocholine micelles. Fluorescence experiments indicated that all peptides were able to interact with LPC micelles. In addition, Ctx(Ile21)-Ha and [TOAC13]Ctx(Ile21)-Ha peptides presented similar water accessibility for the Trp residue located near the N-terminal sequence. Electron spin resonance experiments showed two spectral components for [TOAC0]Ctx(Ile21)-Ha, which are most likely due to two membrane-bound peptide conformations. In contrast, TOAC2 and TOAC13 derivatives presented a single spectral component corresponding to a strong immobilization of the probe. Thus, our findings allowed the description of the peptide topology in the membrane mimetic, where the N-terminal region is in dynamic equilibrium between an ordered, membrane-bound conformation and a disordered, mobile conformation; position 2 is most likely situated in the lipid polar head group region, and residue 13 is fully inserted into the hydrophobic core of the membrane. PMID:23585852

  17. Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine

    SciTech Connect

    Grover, T.W. . Dept. of Geology and Geophysics); Lang, H.M. . Dept. of Geology and Geography); Gordon, T.M. . Dept. of Geology and Geophysics)

    1993-03-01

    A prograde sequence of metapelitic rocks occurs in the Casco Bay area, southwestern Maine. Excellent exposure along the coast of Orrs Island, Harpswell Neck, and Small Point have allowed for the delineation of several metamorphic zones which show an increase in metamorphic grade from west to east across the area. These zones are, in order of increasing metamorphic grade, a garnet zone, a staurolite zone, a staurolite + andalusite zone and a sillimanite [plus minus] andalusite [plus minus] staurolite zone. The widespread occurrence of coexisting andalusite + sillimanite in the highest grade portion of the area, along with the presence of andalusite [plus minus] sillimanite veins on Hermit Island suggest peak metamorphism was near the andalusite-sillimanite transition. Staurolite is also found in apparent textural equilibrium in many of the sillimanite-bearing samples. Metamorphic pressures and temperatures were determined using the approach of Gordon. Peak temperatures range from [approx] 440C in garnet zone rocks to [approx] 510C in sillimanite [plus minus] andalusite zone rocks. Metamorphic pressures are [approx] 3-3.5 kbars. These P-T estimates are consistent with those determined using GeO-Calc. In contrast with the static style of metamorphism reported in central and western Maine, metamorphism in the Casco Bay area, located east of the Norumbega Fault, was synchronous with deformation. The same sequence of porphyroblast growth reported for the Orrs Island-Harpswell Neck area is also found in the Small Point area, suggesting the same metamorphic event affected the entire region. However, coarse grained muscovite pseudomorphs after andalusite or staurolite in rocks with stable andalusite and staurolite are found in the Small Point area suggesting these rocks have a polymetamorphic history. Evidence for polymetamorphism is not found elsewhere in the area.

  18. Chromium isotope signature during continental crust subduction recorded in metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Shen, Ji; Liu, Jia; Qin, Liping; Wang, Shui-Jiong; Li, Shuguang; Xia, Jiuxing; Ke, Shan; Yang, Jingsui

    2015-11-01

    The chromium isotope compositions of 27 metamorphic mafic rocks with varying metamorphic degrees from eastern China were systematically measured to investigate the Cr isotope behavior during continental crust subduction. The Cr isotope compositions of all samples studied were Bulk Silicate Earth (BSE) like, with δ53CrNIST979 of greenschists, amphibolites, and eclogites ranging from -0.06‰ to -0.17‰, -0.05‰ to -0.27‰, and -0.01‰ to -0.24‰, respectively. The lack of resolvable isotopic variability among the metamorphic rocks from different metamorphic zones indicated that no systematic Cr isotope fractionation was associated with the degree of metamorphism. However, the Cr isotopic variability among homologous samples may have reflected effects induced by metamorphic dehydration with a change of redox state, rather than protolith heterogeneity (i.e., magma differentiation). In addition, the differences in δ53Cr (Δ53CrCpx-Gt) between coexisting clinopyroxene (Cpx) and garnet (Gt) from two garnet pyroxenites were 0.06‰ and 0.34‰, respectively, indicating that significant inter-mineral Cr isotope disequilibria could occur during metamorphism. To provide a basis for comparison with metamorphic rocks and to provide further constraints on the potential Cr isotope heterogeneity in the mantle and in the protolith of some metamorphic rocks, we analyzed mantle-derived chromites and the associated peridotites from Luobusa, and we obtained the following general order: chromite-free peridotites (-0.21‰ to -0.11‰) < chromite-bearing peridotite (-0.07‰) < chromite (-0.06‰). These findings imply potential mantle heterogeneity as a result of partial melting or fractional crystallization associated with chromite.

  19. Thermal metamorphism of mantle chromites and the stability of noble-metal nanoparticles

    NASA Astrophysics Data System (ADS)

    González-Jiménez, José M.; Reich, Martin; Camprubí, Antoni; Gervilla, Fernando; Griffin, William L.; Colás, Vanessa; O'Reilly, Suzanne Y.; Proenza, Joaquín A.; Pearson, Norman J.; Centeno-García, Elena

    2015-08-01

    The Loma Baya complex in south-western Mexico is a volume of chromitite-bearing oceanic mantle that records a complex metamorphic history, defined by a first stage of hydrous metamorphism overprinted by a short-lived thermal event associated with an Eocene granite intrusion. During the hydrous metamorphism, the primary magmatic chromite-olivine assemblage was replaced by a secondary, porous intergrowth of Fe2+-rich chromite and chlorite. The heat supplied by an Eocene-age granite intrusion reversed the hydration reaction, producing chromite rims with perfectly developed crystal faces. This third-generation chromite is in equilibrium with highly magnesian (neoformed) olivine and defines a chemical trend analogous to the original magmatic one. The preservation of both reactions in the Loma Baya chromitite provides compelling evidence that the hydration of chromite can be reversed by either prograde metamorphism or any heating event, confirming previous thermodynamic predictions. Understanding these complex features is of particular interest due to the fact that changes in temperature and variable degrees of fluid/rock interaction during metamorphism and intrusion have also significantly affected the chromite-hosted IPGE carrier phases. Here, we propose that the metamorphic fluids involved in the hydrous metamorphism have caused the desulphurization of laurite RuS2, releasing minute particles of Ru-Os-Ir alloys <50 nm in diameter. The following short-lived thermal event that promoted dehydration in the chromitite had the opposite effect on nanoparticle stability, producing a significant coarsening of metal nanoparticles to dimensions larger than a micron. Based on such observations, we argue that IPGE nanoparticles can be exsolved and grown (or coarsen) from sulphide matrices during prograde metamorphism or heating and not exclusively upon cooling under magmatic conditions as it has been previously suggested. These results provide new insights on the relevant role of

  20. Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures

    NASA Technical Reports Server (NTRS)

    French, Bevan M.

    1998-01-01

    This handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures emphasizes terrestrial impact structures, field geology, and particularly the recognition and petrographic study of shock-metamorphic effects in terrestrial rocks. Individual chapters include: 1) Landscapes with Craters: Meteorite Impacts, Earth, and the Solar System; 2) Target Earth: Present, Past and Future; 3) Formation of Impact Craters; 4) Shock-Metamorphic Effects in Rocks and Minerals; 5) Shock-Metamorphosed Rocks (Impactities) in Impact Structures; 6) Impact Melts; 7) How to Find Impact Structures; and 8) What Next? Current Problems and Future Investigations.

  1. The discovery and significance of the northeastern Jiangxi Province ophiolite (NEJXO), its metamorphic peridotite and associated high temperature-high pressure metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Guoqing, Zhou

    The NEJXO with a N.E.-S.W. elongation occurs in the mid-Lower Qigong Group, under which lies the Jiuling Group (1401 Ma) and above which lies the Shangshu Group (817 ± 87 Ma), so that the age of NEJXO is defined to be Proterozoic between 1401 Ma and 817 ± 87 Ma. The sediments of the Jiuling Group show evidence of continental derivation, but the Qigong Group and Shangshu Group are characterised by CA volcanic rocks and probably represent a gradually growing island-arc. Thus, we regard the NEJXO as occurring in a back-island-arc basin between the ancient continent and the island-arc. On the whole, the main members of dismembered ophiolite are all present. The metamorphic periodotite present in them, is considered to be especially important, because it may be the sole representative of the older mantle present and it differs from those younger. The high-T metamorphic rocks associated with the NEJXO are various hornstones and melilite marble, whereas the high-P metamorphic rocks are aragonite-jadeite-glaucophane schist and schistose lawsonite marble. From the fact that high-P metamorphism was superimposed on the high-T metamorphic rocks, it may be suggested that early tension (at opening stage) and late compression (at closing stage) occurred during the development of the basin.

  2. Metamorphic Controls on Relative Strength of Mafic and Felsic Rocks

    NASA Astrophysics Data System (ADS)

    Prior, D. J.; Pearce, M. A.; Wheeler, J.

    2010-12-01

    The bulk strength of a rock undergoing creep deformation is determined by the minerals present and their distribution or microstructure. The stable mineral assemblage of a rock is governed by many factors including temperature, pressure, bulk composition, and water activity. Changes in these factors causing a change in stable mineral assemblage can drive chemically driven recrystallisation leading to grain size reduction and changes in rock strength which are more dramatic than those associated with strain driven recrystallisation. Lithologically heterogeneous regions subject to identical P-T-t paths can, therefore, potentially undergo both spatial and temporal heterogeneous strength evolutions. We present data from the Lewisian Complex, NW Scotland, where a suite of mafic dykes have undergone metamorphism and deformation at amphibolite facies (~600°C and 8-9kbar). Field evidence from fold shapes and attenuation of dykes suggests that the mafic dykes are weaker than the felsic country rock. As a result, it has been proposed that the dykes accommodated the bulk of the deformation following their intrusion whist deformation in the country rock was less intense. In the felsic rocks, crystallographic preferred orientation (CPO) in plagioclase is used to infer deformation by dislocation creep on the (112)[1-10], (1-12)[110], (001)[1-10], and (001)[1-10] slip systems. With increasing strain, this CPO becomes weaker. This is interpreted to have resulted from grain-boundary sliding that accompanied diffusion creep following strain driven recrystallisation. In the metamorphosed dykes, plagioclase aggregates have a CPO which cannot be interpreted in terms of known slip-systems. Local maxima could result from parent controlled recrystallisation during chemically induced recrystallisation. Amphibole has a strong CPO consistent with dislocation creep on (100)[001] but there is no evidence of dislocations. Furthermore, studies on rocks deformed at similar conditions suggest

  3. The timing of tertiary metamorphism and deformation in the Albion-Raft River-Grouse Creek metamorphic core complex, Utah and Idaho

    USGS Publications Warehouse

    Strickland, A.; Miller, E.L.; Wooden, J.L.

    2011-01-01

    The Albion-Raft River-Grouse Creek metamorphic core complex of southern Idaho and northern Utah exposes 2.56-Ga orthogneisses and Neoproterozoic metasedimentary rocks that were intruded by 32-25-Ma granitic plutons. Pluton emplacement was contemporaneous with peak metamorphism, ductile thinning of the country rocks, and top-to-thewest, normal-sense shear along the Middle Mountain shear zone. Monazite and zircon from an attenuated stratigraphic section in the Middle Mountain were dated with U-Pb, using a SHRIMP-RG (reverse geometry) ion microprobe. Zircons from the deformed Archean gneiss preserve a crystallization age of 2532 ?? 33 Ma, while monazites range from 32.6 ?? 0.6 to 27.1 ?? 0.6 Ma. In the schist of the Upper Narrows, detrital zircons lack metamorphic overgrowths, and monazites produced discordant U-Pb ages that range from 52.8 ?? 0.6 to 37.5 ?? 0.3 Ma. From the structurally and stratigraphically highest unit sampled, the schist of Stevens Spring, narrow metamorphic rims on detrital zircons yield ages from 140-110 Ma, and monazite grains contained cores that yield an age of 141 ??2 Ma, whereas rims and some whole grains ranged from 35.5 ?? 0.5 to 30.0 ?? 0.4 Ma. A boudinaged pegmatite exposed in Basin Creek is deformed by the Middle Mountains shear zone and yields a monazite age of 27.6 ?? 0.2 Ma. We interpret these data to indicate two periods of monazite and metamorphic zircon growth: a poorly preserved Early Cretaceous period (???140 Ma) that is strongly overprinted by Oligocene metamorphism (???32-27 Ma) related to regional plutonism and extension. ?? 2011 by The University of Chicago.

  4. Thermal histories of CO3 chondrites - Application of olivine diffusion modelling to parent body metamorphism

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.; Rubie, David C.

    1991-01-01

    The petrologic sequence observed in the CO3 chondrite group has been suggested to be the result of thermal metamorphism on a parent body. A model developed to examine the possibility that chondrule and matrix olivines equilibrated in situ, during parent body metamorphism is presented. The model considers Fe-Mg interdiffusion between chondrule and matrix olivines. Zoning profiles comparable to those observed in chondrule olivines from partially equilibrated members of the series are reproduced successfully. Metamorphism of CO3 chondrites on a parent body is therefore a viable model for the observed equilibration. Results indicate that peak metamorphic temperatures experienced by the CO3 chondrites were around 500 C, and that the range of peak temperatures between unequilibrated and equilibrated subtypes was relatively narrow, around 100 C.

  5. Inverted Metamorphic Cell Development: Cooperative Research and Development Final Report, CRADA Number CRD-05-156

    SciTech Connect

    Wanlass, M.

    2012-05-01

    This CRADA targeted technology transfer of the inverted metamorphic multi-junction (IMM) solar cell innovation from NREL to Emcore Photovoltaics. The technology transfer was successfully completed. Additionally, NREL provided materials characterization of solar cell structures produced at Emcore.

  6. Metamorphism of an Efremovka Type B CAI and Comparison with Other Settings of Alteration

    NASA Astrophysics Data System (ADS)

    Fagan, T. J.; Aragane, H.; Enokido, Y.; Brearley, A. J.

    2015-07-01

    Primary minerals in a type B CAI from Efremovka are partially altered to feldspathoids, Fe-spinel and secondary anorthite. The extent of recrystallization is not as great as in typical Allende CAIs, but metamorphism has affected Efremovka CAIs.

  7. Associations analysis of GSTM1, T1 and P1 Ile105Val polymorphisms with carpal tunnel syndrome.

    PubMed

    Eroğlu, Pınar; Erkol İnal, Esra; Sağ, Şebnem Özemri; Görükmez, Özlem; Topak, Ali; Yakut, Tahsin

    2016-05-01

    Oxidative stress was related with carpal tunnel syndrome (CTS). We aimed to clarify the associations between glutathione S-transferase (GST)M1, GSTT1 and GSTP1-Ile105Val polymorphisms and CTS. One hundred-forty patients with CTS and 97 healthy controls were enrolled in this study. Tinel and Phalen signs were noted as positive or negative. Functional and clinical status of patients was evaluated by the Boston Questionnaire. The intensity of hand and/or wrist pain was evaluated on 10 cm visual analog scale (VAS). We applied the polymerase chain reaction (PCR) to determine the polymorphisms of the GSTM1 and GSTT1 and the PCR-restriction fragment length polymorphism method for detecting the GSTP1-Ile105Val polymorphism. The M1 null genotype was significantly higher in patients with CTS compared to healthy controls, and the M1 null genotype seemed to increase the risk of CTS approximately two-fold (P = 0.011; odds ratio (OR) = 1.98; 95 % confidence interval (CI) 1.17-3.36). The M1 null, T1 present combined genotype was significantly higher in patients with CTS compared to healthy controls (P = 0.043); however, it seemed not to increase the risk of CTS (P = 0.14; OR = 0.62; 95 % CI 0.33-1.76). We found significantly higher levels of the VAS, Boston Symptom Severity Scale and Phalen sign in patients with the Ile/Val or the Val/Val genotypes compared to those in patients with the Ile/Ile genotype (P = 0.003, 0.004 and 0.044, respectively). We proposed that genes involved in the protection from oxidative stress may influence the susceptibility, clinical and functional status of CTS. The GSTM1 null genotype may be related with the development of CTS, whereas the Val allele of GSTP1-Ile105Val polymorphism may be associated with worse functional and clinical status in CTS. PMID:25566970

  8. Gating of high-mobility InAs metamorphic heterostructures

    SciTech Connect

    Shabani, J.; McFadden, A. P.; Shojaei, B.; Palmstrøm, C. J.

    2014-12-29

    We investigate the performance of gate-defined devices fabricated on high mobility InAs metamorphic heterostructures. We find that heterostructures capped with In{sub 0.75}Ga{sub 0.25}As often show signs of parallel conduction due to proximity of their surface Fermi level to the conduction band minimum. Here, we introduce a technique that can be used to estimate the density of this surface charge that involves cool-downs from room temperature under gate bias. We have been able to remove the parallel conduction under high positive bias, but achieving full depletion has proven difficult. We find that by using In{sub 0.75}Al{sub 0.25}As as the barrier without an In{sub 0.75}Ga{sub 0.25}As capping, a drastic reduction in parallel conduction can be achieved. Our studies show that this does not change the transport properties of the quantum well significantly. We achieved full depletion in InAlAs capped heterostructures with non-hysteretic gating response suitable for fabrication of gate-defined mesoscopic devices.

  9. The thermodynamics of deformed metamorphic rocks: A review

    NASA Astrophysics Data System (ADS)

    Hobbs, Bruce E.; Ord, Alison; Regenauer-Lieb, Klaus

    2011-05-01

    The deformation of rocks is a disequilibrium and strongly non-linear phenomenon with a number of interacting chemical, thermal and microstructural processes operating simultaneously. We review progress in this area over the past 30 years. Deforming-chemically reacting systems are dissipative systems and hence are characterised by highly ordered structures that develop through cooperative processes once parameters such as critical strains, strain-rates, fluid infiltration rates, damage densities or temperatures are attained. Such criticality is the hallmark of deformed rocks at all length scales and is the basis for a diverse range of structures such as foliations and lineations produced by metamorphic differentiation, rotation recrystallisation, folding, boudinage and micro to regional scale fracture systems. Criticality is identified with classical criticality and not self-organised criticality. The first and second laws of thermodynamics are used to show that such structural diversity arises from reaction-diffusion-deformation equations. Criticality of the system is associated with the stored energy becoming non-convex and structures arise in order to minimise this non-convex energy. These structures are scale invariant and hence are characterised by fractal and minimal surface geometries. Thermodynamics is a powerful discipline to integrate seemingly unrelated processes in structural geology and produce an integrated approach to the subject that crosses all length scales.

  10. Uranium mineralization in response to regional metamorphism at Lilljuthatten, Sweden.

    USGS Publications Warehouse

    Stuckless, J.S.; Troeng, B.

    1984-01-01

    Uranium deposits occur in the Olden granite of approx 1650 m.y. in age. This granite outcrops in the northern and eastern segments of the Precambrian Olden window of the central Swedish Caledonides. The Olden granite is a 'highly evolved' biotite granite, with SiO2 >70%. The granite was rich in U (and other incompatible trace elements) and much of the U was located in labile sites. During the Caledonian orogeny 420 m.y. ago, the granite was metamorphosed to greenschist facies, clastically deformed, hydrothermally altered in turn, and mineralized along fractures with quartz, fluorite, calcite and galena. Pitchblende and coffinite were locally deposited as fracture fillings, in particular association with biotitic alteration, whose relation to hydrothermal alteration is obscure; biotite is concentrated along fractures. The U deposits are partly and 'recently' oxidized. The Pb-U, Pb-Pb, and Sr-Rb isotopic systems of most samples were strongly to completely reset by the Caledonian orogeny. The source and host of the Lilljuthatten uranium ore was a special type of granite. The granite fractured, U was mobilized by metamorphism, and deposited in the fractures, and the deposit was preserved from weathering. Similar U deposits in high U granites, common in the Swedish Caledonides, should occur elsewhere.-G.J.N.

  11. Dynamic treatment of invariant and univariant reactions in metamorphic systems

    SciTech Connect

    Lasaga, A.C.; Luettge, A.; Rye, D.M.; Bolton, E.W.

    2000-03-01

    A simple model is presented that incorporates the essential dynamics of metamorphic processes leading to reactions along univariant curves and up to and beyond the invariant point. The model includes both heat flow by conduction and convection as well as fluid flow in and out of a representative volume. Overall mineral reactions can then take place within this rock volume in response to internal and external factors. The paper derives a simple back-of-the-envelope expression for the steady state reached by the system. The steady state composition of the fluid and the steady state temperature are then compared with the composition and temperature predicted by the assumption of thermodynamic equilibrium. Expressions for the amount of fluid passing through the system based on the kinetic model are compared with previous calculations of the mass of fluid added to the system using the equilibrium assumptions. The approach to this steady state is also analyzed and an analytical solution is obtained for the time evolution up to the steady state. Both the steady state and the time evolution solution are then applied to an understanding of the dynamics involved in obtaining T-X-t paths in nature. The results of the kinetic approach lead to major revisions in many of the previously held concepts used in petrologic fluid flow models. These include the expected reaction pathway, the role of metastable reactions, the calculation of fluid flux, the role of the invariant point, and the interpretation of mineral textures and modal abundances of minerals.

  12. Geophysics: hot fluids or rock in eclogite metamorphism?

    PubMed

    Bjørnerud, M G; Austrheim, H

    2006-03-16

    The mechanisms by which mafic rocks become converted to denser eclogite in the lower crust and mantle are fundamental to our understanding of subduction, mountain building and the long-term geochemical evolution of Earth. Based on larger-than-expected gradients in argon isotopes, Camacho et al. propose a new explanation--co-seismic injection of hot (700 degrees C) aqueous fluids into much colder (400 degrees C) crust--for the localized nature of eclogite metamorphism during Caledonian crustal thickening, as recorded in the rocks of Holsnøy in the Bergen arcs, western Norway. We have studied these unusual rocks, which were thoroughly dehydrated under granulite facies conditions during a Neoproterozoic event (about 945 million years (945 Myr) ago); we also concluded that fracture-hosted fluids were essential as catalysts and components in the conversion to eclogite about 425 Myr ago. However, we are sceptical of the assertion by Camacho et al. that eclogite temperatures were reached only in the vicinity of fluid-filled fractures. Determining whether these rocks were strong enough to fracture at depths of 50 km because they were cold or because they were very dry is crucial to understanding the mechanics of the lower crust in mountain belts, including, for example, the causes of seismicity in the Indian plate beneath the modern Himalayas. PMID:16541027

  13. Metamorphism in oceanic layer 3, Gorringe Bank, eastern Atlantic

    NASA Astrophysics Data System (ADS)

    Mevel, Catherine

    1988-12-01

    Gorringe Bank is an anomalously high structure of the eastern part of the north Atlantic, which was known to be composed of mantle-derived peridotites (layer 4) and gabbros (layer 3). During the submersible cruise CYAGOR II in 1981, the contact between layer 4 and layer 3 was observed on Mount Gettysburg and interpreted as tectonic. The overlying series of gabbro was extensively sampled on both mounts composing the bank, Gettysburg and Ormonde. Coarse-grained to pegmatoid clinopyroxene gabbros predominate and are associated with differentiated rocks (ferrogabbros and diorites). Cumulate gabbros are missing. The gabbroic section sampled is therefore interpreted as the upper part of the plutonic section. Most samples were strongly recrystallized during two distinct events. Metamorphism occurred close to the ridge axis, from interaction of a seawater-derived fluid with still hot gabbros. High temperature shear zones favoured fluid circulation, but the water/rock ratio — estimated from the sodium input — was very small in undeformed rocks (<1). The low W/R ratio explains the strong evolution of the fluid phase and therefore some particular compositions of secondary minerals. Low temperature alteration occurred when the gabbros were tectonically emplaced close to the sea bottom.

  14. A rift-related origin for regional medium-pressure, high-temperature metamorphism

    NASA Astrophysics Data System (ADS)

    Tucker, Naomi M.; Hand, Martin; Payne, Justin L.

    2015-07-01

    Crustal-scale exhumation during the Alice Springs Orogeny (c. 450-320 Ma) in central Australia has exposed a region of medium-pressure, high-temperature metasedimentary and metabasic rocks that comprise the Harts Range Group (HRG). Similarities in the detrital zircon age spectra between the HRG and surrounding unmetamorphosed, intraplate late Neoproterozoic-Cambrian basin sequences suggest that the HRG is a highly metamorphosed equivalent of these successions. Calculated phase equilibria modelling and thermobarometry constrain peak metamorphic conditions to ˜ 880 °C and 10.5 kbar, and ˜ 680 °C and 5.5-8.0 kbar, in the structurally lowest and highest parts of the HRG, respectively. Metamorphic conditions also indicate that burial occurred along a near-linear moderately-high apparent thermal gradient, recorded by the prograde development of andalusite-bearing mineral assemblages at shallower structural levels. Prograde and peak metamorphism was associated with voluminous intrusive and extrusive mafic magmatism, the development of a coarse layer-parallel fabric and north-directed normal shear-sense kinematics. Collectively, these point to an extensional regime. Furthermore, burial and metamorphism at c. 480-460 Ma was concurrent with a shallow epicontinental marine environment and ongoing sedimentation in central Australia. Accordingly, the deep burial, metamorphism and deformation of the HRG to mid-lower crustal depths (˜ 20- 35 km) must be justified in the context of the broader intraplate basin evolution at this time. It is difficult to reconcile medium-pressure, high-temperature metamorphism of the HRG with deep burial by tectonic overthickening which is commonly assumed to be the case. In contrast, metamorphism of the HRG seems more compatible with burial within a deep rift-style basin driven by high heat flow and mafic magmatism, suggesting that regional medium-pressure metamorphic terranes are not necessarily reflective of compressional thickening of the

  15. Tectono-metamorphic history of southern New Hampshire and southeastern Vermont

    SciTech Connect

    Chamberlain, C.P.; Lyons, J.B.; Thompson, J.B. Jr.; Rosenfeld, J.L.; Downie, E.

    1985-01-01

    A major boundary between two Acadian metamorphic terranes is marked by a band of low-grade rocks in the Connecticut River valley coinciding with the Monroe Line (ML) and separating higher-grade rocks in two distinct lithostratigraphic terranes. To the west, Cambro-Devonian rocks in the Vermont sequence overlie Grenvillian basement, whereas to the east a different Cambro-Dev. sequence rests upon Hadrynian basement. These terranes were assembled no later than the early Devonian. The eastern terrane, consisting of the Bronson Hill Anticlinorium(BHA) and Merrimack Synclinorium (MS), is bounded on the east by the older Massabesic Gneiss (650-480 my) and Ord (.) Merrimack Group. This southeastern terrane was in contact with the MS by the early Devonian because there is no break in metamorphism across the terrane boundary. Metamorphism in the western terrane (Vermont) is synkinematic and peaks in the Staur-Ky zone. The earliest metamorphism is believed to be Taconian and represents the thermal decay of relict blueschist metamorphism observed to the northwest and the accretion of an island-arc. The earliest metamorphism in the eastern terrane (BHA-MS) is Acadian and is associated with nappe formation and synkinematic plutons. Continued Acadian crustal shortening in the MS resulted in a pressure increase (from 3.8 to 7 kb), with rocks reaching peak metamorphism in the Sil-Mus up to Kspar-Cord zones. The authors suggest that this high-grade metamorphism was the result of a high transient heat flux initiated by crustal stretching in the MS during the Silurian and early Devonian when 8 km of clastics were deposited in a rapidly subsiding trough.

  16. Age and metamorphism of some massive sulflde deposits in Virginia, North Carolina and Tennessee

    USGS Publications Warehouse

    Kinkel, A.R., Jr.; Thomas, H.H.; Marvin, R.F.; Walthall, F.G.

    1965-01-01

    Isotopic ages of vein and wall-rock samples have been determined on five massive sulflde deposits of the southern Appalachians. Vein mineral ages of about 1100 m.y. indicate that some ore bodies formed at least as early as the Grenville metamorphism, and probably soon after the formation of the enclosing gneiss and schist. Present textures of the ore were formed during subsequent metamorphic periods at about 450 m.y. and 300 to 330 m.y. ago. ?? 1965.

  17. Quantitative estimates of metamorphic equilibria: Tallassee synform, Dadeville belt, Alabama's Inner Piedmont

    SciTech Connect

    Drummond, M.S.; Neilson, M.J. . Dept. of Geology)

    1993-03-01

    The Tallassee synform is the major structural feature in the western part of the Dadeville belt. This megascopic F2 structure folds amphibolite (Ropes Creek Amphibolite) and metasedimentary units (Agricola Schist, AS), as well as tonalitic (Camp Hill Gneiss, CHG), granitic (Chattasofka Creek Gneiss, CCG), and mafic-ultramafic plutons (Doss Mt. and Slaughters suites). Acadian-age prograde regional metamorphism preceded the F2 folding event, producing the pervasive S1 foliation and metamorphic recrystallization. Prograde mineralogy in the metapelites and metagraywackes of the AS includes garnet, biotite, muscovite, plagioclase, kyanite, sillimanite, and epidote. The intrusive rocks, both felsic and mafic-ultramafic, are occasionally garnetiferous and provide suitable mineral assemblages for P-T evaluation. The AS yields a range of T-P from 512--635C and 5.1--5.5 kb. Muscovite from the AS exhibits an increase in Ti content from 0.07 to 0.15 Ti/22 O formula unit with progressively increasing T's from 512 to 635C. This observation is consistent with other studies that show increasing Ti content with increasing grade. A CHG sample records an average metamorphic T-P of 604C and 5.79 kb. Hornblende-garnet pairs from a Doss Mt. amphibolite sample provides an average metamorphic T of 607C. These data are consistent with regional Barrovian-type middle to upper amphibolite facies metamorphism for the Tallassee synform. Peak metamorphism is represented by kyanite-sillimanite zone conditions and localized migmatization of the AS. The lithotectonic belts bounding the Dadeville belt to the NW and SE are the eastern Blue Ridge and Opelika belts. Studies have shown that these belts have also experienced Acadian-age amphibolite facies metamorphism with comparable P-T estimates to those presented here. These data suggest that the eastern Blue Ridge and Inner Piedmont of AL experienced the same pervasive dynamothermal Barrovian-type metamorphic episode during Acadian orogenesis.

  18. Potential contributions of metamorphic petrology studies in an ultra-deep drillhole in the southern Appalachians

    SciTech Connect

    Speer, J.A.

    1985-01-01

    The proposed, ultra-deep hole in the southeast U.S. will penetrate allochthonous, medium- to high-grade metamorphic rocks of the Inner Piedmont and Blue Ridge thrust sheets. It is anticipated that the hole will then encounter autochthonous low-grade, metasedimentary cover rocks before bottoming out in crystalline Precambrian basement rocks. Metamorphic petrology in the recent past has concentrated on unraveling the physical and chemical history (P, T, X/sub fluid/, etc.) of metamorphic rocks. The techniques that have been developed are ideally suited to the study of relatively limited samples from drill core. Detailed studies of the allochthonous and autochthonous rocks from the drillhole, combined with comparable studies of the surface rocks, by metamorphic petrologists experimented with these approaches, would give a 3-dimensional picture of the PTX evolution in the region of the ultra-deep hole, and thus an idea of the geometrical, chemical, and physical changes the rocks experienced. This would place constraints on conditions of the rocks before and after thrusting and thus any tectonic models of thrusting in the southern Appalachians. With limited sampling this could be a problem, with more complete sampling it will be an advantage. The metamorphic petrology of the rocks will provide basic support for the other studies of the drill core and drillhole, most notably geochronology and stable isotopes. It should not be forgotten that in addition to the historical metamorphism, the expected, present-day conditions in the drillhole are those of burial metamorphism. The hole will present an excellent opportunity to study such active metamorphic conditions.

  19. The northern coast plutonic-metamorphic complex, southeastern Alaska and northwestern British Columbia

    NASA Astrophysics Data System (ADS)

    Brew, D. A.; Ford, A. B.

    The northern Coast plutonic-metamorphic complex is but one segment of an 8,000-km-long batholithic complex that extends the length of the North American Cordillera from Baja, California to the Aleutian Islands. Different segments of the Cordilleran batholithic complex have significantly different features. This report documents the main characteristics and inferred evolutionary history of the northern Coast plutonic-metamorphic complex that should facilitate comparisons between segments.

  20. Vein Controlled Index Mineral Crystal Size Distribution in Barrow's Metamorphic Zones, Glen Esk, Scotland

    NASA Astrophysics Data System (ADS)

    Lewerentz, A.; Skelton, A.; Linde, J. K.; Nilsson, J.; Möller, C.; Crill, P. M.; Spicuzza, M. J.

    2015-12-01

    The concept of index mineral based metamorphic zones was first introduced by George Barrow a little more than 100 years ago, and the Barrovian metamorphic zones are still today used as framework by metamorphic petrologists. Today the importance of metamorphic fluids for driving metamorphic reactions is widely recognised. Even so, a general view is that Barrovian metamorphism is solely controlled by pressure, temperature, and protolith composition. This study aims to establish if and how fluids control index mineral formation and distribution during Barrovian metamorphism. To do so, we use samples from Barrow's own type locality in Glen Esk, Southeast Scottish Highlands, and study possible relationships between veining and index mineral distribution. In addition to petrographic and textural observations and analyses, we also use whole rock chemistry, mineral chemistry, and oxygen isotope analyses. At low grade, in the chlorite zone and most of the biotite zone, no correlation between veining and index mineral distribution is seen. At higher grade, the index mineral abundance is shown to decrease away from veins in the garnet and staurolite zones. Pseudosection analysis show larger garnet stability fields in vein-adjacent rock. In addition, quartz abundance and oxygen isotope ratios of quartz coincidentally decrease, which we interpret as evidence for fluid-rock interaction. The kyanite zone shows a fairly homogenous kyanite distribution, but also indications of extensive fluid-rock interaction, such as high vein density and oxygen isotope ratios in equilibrium with the fluid. Based on our observations and the geochemical datasets, we conclude that fluid played a major role in the stabilisation and distribution of the Barrovian index minerals in Glen Esk, and that the fluid control was larger at higher metamorphic grades.

  1. Koolen metamorphic complex, NE Russia: Implications for the tectonic evolution of the Bering Strait region

    NASA Astrophysics Data System (ADS)

    Akinin, Vyacheslav V.; Gelman, Mikhail L.; Sedov, Boris M.; Amato, Jeffrey M.; Millwer, Elizabeth L.; Toro, Jaime; Calvert, Andrew T.; Fantini, Riccardo M.; Wright, James E.; Natal'in, Boris A.

    Structural culminations of midcrustal metamorphic rocks are found on both sides of the Bering Strait in Alaska and Russia and occur within a magmatic belt of Cretaceous age. Geologic mapping in the Koolen Lake-Lavrentia Bay region of the Chukchi Peninsula, Russia, outlines the basic relations between deformation, metamorphism, and magmatism in one of these structural culminations, the Koolen metamorphic complex. Here, a 10-15 km-thick, southwest dipping structural succession of gneisses and high-grade metamorphic rocks is exposed. The succession consists of a lower sequence of granitic gneisses and an upper sequence of biotite-rich gneisses, quartzofeldspathic gneisses, lesser amphibolite and marble, and gneisses and schists with an increasing abundance of intercalated marble and calc-silicate units toward the top. All rocks are strongly foliated and exhibit north-south trending stretching lineations. Deformation occurred during sillimanite-grade metamorphism concurrent with partial melting of the crust. Metamorphic conditions varied from 7 to 3 kbar and from 700°C-500°C. Three fractions of monazite from a deformed pegmatite yielded ages of 104 Ma. Igneous monazite from undeformed biotite granite yielded a U-Pb age of 94 Ma, indicating peak metamorphism and deformation is Cretaceous. Relations in the Koolen complex are similar to those in the Kigluaik gneiss dome, Seward Peninsula, Alaska, where upper amphibolite to granulite facies metamorphism and deformation occurred between ~105 and 90 Ma. Our findings,together with regional relations, suggest that wholesale crustal extension or extensional collapse of the crust affected this region, perhaps during Pacific-ward migration of subduction. The results do not support large amounts of east-west shortening between North America and Russia predicted by poles of rotation related to opening of the North Atlantic in the Late Cretaceous and Tertiary.

  2. Structural and functional characterization of mutants of recombinant single-chain urokinase-type plasminogen activator obtained by site-specific mutagenesis of Lys158, Ile159 and Ile160.

    PubMed

    Lijnen, H R; Nelles, L; Van Hoef, B; Demarsin, E; Collen, D

    1988-11-15

    Single-chain urokinase-type plasminogen activator (scu-PA) is converted to urokinase by hydrolysis of the Lys158-Ile159 peptide bond. Site-directed mutagenesis of Lys158 to Gly or Glu yields plasmin-resistant mutants with a 10-20-fold reduced catalytic efficiency for the activation of plasminogen [Nelles et al. (1987) J. Biol. Chem. 262, 5682-5689]. In the present study, we have further evaluated the enzymatic properties of derivatives of recombinant scu-PA (rscu-PA), produced by site-directed mutagenesis of Lys158, Ile159 or Ile160, in order to obtain additional information on the structure/function relations underlying the enzymatic properties of the single- and two-chain u-PA moieties. [Arg158]rscu-PA (rscu-PA with Lys158 substituted with Arg) appeared to be indistinguishable from wild-type rscu-PA with respect to plasminogen-activating potential (catalytic efficiency k2/Km = 0.21 mM-1 s-1 versus 0.64 mM-1 s-1), conversion to active two-chain urokinase by plasmin (k2/Km = 0.13 microM-1 s-1 versus 0.28 microM-1 s-1), as well as its specific activity (48,000 IU/mg as compared to 60,000 IU/mg) and its fibrinolytic potential in a plasma medium (50% lysis in 2 h with 2.8 micrograms/ml versus 2.1 micrograms/ml). [Pro159]rscu-PA (Ile159 substituted with Pro) and [Gly159]rscu-PA (Ile159 converted to Gly) are virtually inactive towards plasminogen (k2/Km less than 0.004 mM-1 s-1). They are however converted to inactive two-chain derivatives by plasmin following cleavage of the Arg156-Phe157 peptide bond in [Pro159]rscu-PA and of the Lys158-Gly159 peptide bond in [Gly159]rscu-PA. [Gly158,Lys160]rscu-PA (with Lys158 converted to Gly and Ile160 to Lys) has a low catalytic efficiency towards plasminogen both as a single-chain form (k2/Km = 0.012 mM-1 s-1) and as the two-chain derivative (k2/Km = 0.13 mM-1 s-1) generated by cleavage of both the Arg156-Phe157 and/or the Lys160-Gly161 peptide bonds by plasmin. These findings suggest that the enzymatic properties of rscu-PA are

  3. 3D geometrical modelling of post-foliation deformations in metamorphic terrains (Syros, Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Philippon, Mélody; Le Carlier de Veslud, Christian; Gueydan, Frédéric; Brun, Jean-Pierre; Caumon, Guillaume

    2015-09-01

    Superposed to ductile syn-metamorphic deformations, post-foliation deformations affect metamorphic units during their exhumation. Understanding the role of such deformations in the structuration of metamorphic units is key for understanding the tectonic evolution of convergence zones. We characterize post-foliations deformations using 3D modelling which is a first-order tool to describe complex geological structures, but a challenging task where based only on surface data. We propose a modelling procedure that combines fast draft models (interpolation of orientation data), with more complex ones where the structural context is better understood (implicit modelling), allowing us to build a 3D geometrical model of Syros Island blueschists (Cyclades), based on field data. With our approach, the 3D model is able to capture the complex present-day geometry of the island, mainly controlled by the superposition of three types of post-metamorphic deformations affecting the original metamorphic pile: i) a top-to-South ramp-flat extensional system that dominates the overall island structure, ii) large-scale folding of the metamorphic units associated with ramp-flat extensional system, and iii) steeply-dipping normal faults trending dominantly NNW-SSE and EW. The 3D surfaces produced by this method match outcrop data, are geologically consistent, and provide reasonable estimates of geological structures in poorly constrained areas.

  4. Distinguishing among major controls on the apparent thermal and barometric structure of metamorphic belts

    SciTech Connect

    Day, H.W.

    1985-01-01

    The apparent thermal and barometric structures of metamorphosed terrains are expressed in the map patterns of isograds and bathograds. Geographic variation in the apparent P,T of peak metamorphism may be the result of: (1) differences in the amount of tectonic thickening (2) variation in the thermal properties of the lithosphere or (3) differential uplift across the mountain belt. Oversimplified tectonic models of a burial and uplift event, combined with simple physical models for the conductive transfer of heat, have normally been used. The results suggest that the relative roles of the three large scale controls on metamorphism may be distinguished. In mountain belts having variable tectonic thickening, apparent isotherms and isobars of peak metamorphism are parallel. Geographic variation in either thermal properties or uplift history, by contrast, leads to patterns of intersecting apparent isobars and isotherms (e.g.. the New England Appalachians). In terrains that experienced rapid and differential uplift, the most rapidly uplifted portions show the shortest cooling times, the least discordance between apparent mineral ages, and the lowest pressures at peak metamorphism and no necessary correlation between metamorphic grade and cooling time (e.g.. the Alps). In contrast, in terrains with large variations in either thermal parameters or tectonic thickening, long cooling times are directly associated with the highest metamorphic temperatures and the least discordance between apparent mineral ages (e.g.. the Scottish Highlands).

  5. Cretaceous crustal structure and metamorphism in the hinterland of the Sevier thrust belt, western US Cordillera

    SciTech Connect

    Miller, E.L.; Gans, P.B. )

    1989-01-01

    Combined structural and geochronologic studies to the west of the Sevier belt at lat 39{degree}-40{degree}N indicate that peak metamorphism of the upper 15 km of crust occurred during the Late Cretaceous (70-90 Ma), overlapping in time with the intrusion of muscovite-bearing granites and pegmatites. Metamorphism was accompanied by penetrative deformation (top-to-the-east layer-parallel shear); both were localized at the currently exposed structural levels, resulting in impressive vertical and lateral strain gradients and T{sub max} gradients of > 50 C/km. Inception of thrust faulting in the Sevier belt may have predated peak metamorphism and intrusion of granites in the hinterland by 10-15 m.y., but it continued during and ended simultaneously with the end of metamorphism at about 70 Ma. The rise of muscovite-bearing granites and hot fluids, generated by metamorphism and crustal anatexis at greater depth, provides and explanation for the observed localized metamorphism and deformation at relatively high structural levels.

  6. Archean gold mineralization and metamorphism: timing constraints from precise U-Pb dating

    SciTech Connect

    Colvine, A.C.; Corfu, F.; Davis, D.W.; Stott, G.M.

    1985-01-01

    Gold mineralization is tightly constrained to an event closely following establishment of peak metamorphic condition, in all areas of the Superior Province of Canada where precise dating has been applied to defined field relationships. In the Abitibi and Wabigoon Subprovinces of the Southern Superior Domain, peak metamorphism caused by major batholith emplacement is consistently >2685 Ma and affects Archean supracrustal units of all ages (mainly >2700 Ma). Gold is commonly hosted by felsic stocks, dated at a specific age in the Abitibi Belt (2688-2684 Ma), and is therefore close to or younger than peak metamorphism. Dateable units crosscutting mineralization are extremely rare, but at Shebandowan and Mine Centre dated field relationships bracket the maximum and minimum age of mineralization between 2689 - 2684 and 2692 - 2686 Ma, respectively. While the metamorphic event in the Northern Superior Domain is approximately 20 my older, relative timing of gold mineralization is identical. At Red Lake, gold is hosted by units ranging in age from 2990-2718 Ma, all metamorphosed at >2704 Ma. Peak metamorphic minerals are retrograded by alteration during gold localization and mineralization is cut by a 2704 Ma dyke. These data show that gold mineralization was the product of a tectonic event during the latest Archean which involved major plutonism, deformation and metamorphism.

  7. Metamorphic hydrology at 13 km depth and 400/sup 0/-550/sup 0/C

    SciTech Connect

    Ferry, J.M.

    1985-01-01

    The pattern of metamorphic fluid flow through six large outcrops of regionally metamorphosed impure carbonate rock from a single stratigraphic unit in south-central Maine was determined by quantitative measurement of the progress of the prograde devolatilization reactions. With reference to adjacent pelitic schists, the outcrops are located in the chlorite, biotite, garnet, staurolite-andalusite, and sillimanite zones. Two components of flow were detected: a pervasive component and a channelized component. In the chlorite, biotite, and garnet zones fluid flow was highly channelized along bedding with enhanced flow occurring within the more impure carbonate layers that acted as metamorphic aquifers. A smaller amount of pervasive background flow also occurred within the intervening more impure carbonate layers that acted as metamorphic aquifers. A smaller amount of pervasive background flow also occurred within the intervening more pure carbonate layers that acted as metamorphic aquitards. Fluid-rock ratios differ between aquifers and aquitards by a factor greater than 50 over distances of 1 mm or less at grades lower than the staurolite-andalusite zone. Two generalization can be made about the affect of metamorphic grade on patterns of fluid flow: with increasing grade (1) flow becomes less channelized and more pervasive and (b) the average time-integrated fluid flux for a whole outcrop increases. Patterns of metamorphic fluid flow may be rationalized in terms of a model for reaction-enhanced permeability.

  8. Deformation and metamorphism of Hamadat complex: Shear zones reshaping the lithosphere

    NASA Astrophysics Data System (ADS)

    Hassan, Mahmoud; Abu-Alam, Tamer; Stüwe, Kurt

    2015-04-01

    In the active tectonic regions, shear zones play an important role to re-configure the structure of the lithosphere. One of the largest pre-Mesozoic shear zones on the Earth is the Najd Fault System of the Arabian-Nubian Shield. Literature data record exhumation of medium-pressure metamorphic complexes due to the activity of the Najd Fault System during the Pan-African Orogeny where the shear zone surrounds the boundaries of metamorphic complexes. The Hamadat complex of Northwestern part of Saudi Arabia shows an exception where the metamorphic rocks appear to occur within the shear zone itself instead of being surrounded by branches of it. The Hamadat complex records peak metamorphic conditions of 505 - 700 °C at two ranges of pressure 8 - 11 and 12.5 - 16.5 kbar. These pressures are higher than those of most other metamorphic complexes associated and exhumed by the Najd Fault system. The higher pressure conditions of the Hamadat complex relatively to other complexes in the shield can be interpreted in two different ways. The documented pressure can be due to lithostatic pressure or shear stress (i.e. in part non-lithostatic). Assuming the lithostatic condition, these pressure ranges indicate that the Hamadat complex consists rocks from two different crustal level (i.e. 28 - 38 km and 43 - 58 km) which shows the importance of the shear zone to reshape the lithosphere by bring rocks from different crustal level into one metamorphic complex.

  9. Effects of Metamorphism on the Valence and Coordination of Titanium in Ordinary Chondrites

    SciTech Connect

    Simon, S.B.; Sutton, S.R.; Grossman, L.

    2012-04-02

    Despite years of study, the conditions under which ordinary chondrites were metamorphosed from grade 3 to grade 6 are not well defined. Wide ranges of peak temperature are inferred for each grade. The long-popular 'onion shell' model, in which higher metamorphic grade is attributed to greater depths of origin, implies a corresponding decrease in cooling rate with increasing grade, and there is disagreement as to whether or not this is observed. Redox conditions during chondrite metamorphism are also not well understood. Some workers have reported evidence for reduction, presumably by carbon, with increase in grade from 3-4, followed by oxidation during metamorphism to higher grades, but other work indicates little variation in fO{sub 2} as a function of metamorphic grade. During our investigation of the valence of Ti in planetary materials, we found high proportions of Ti{sup 3+} in olivine and pyroxene in chondrules in Semarkona (LL3.0) and low proportions in New Concord (L6) olivine, suggesting that Ti was oxidized during ordinary chondrite metamorphism. We have undertaken a study of L and LL chondrites of grades 3-6 to see how Ti valence and coordination vary with grade and to see if the variations can be used to constrain conditions of chondrite metamorphism.

  10. Contrasting Metamorphic Record of Heat Production Anomalies in the Penokean Orogen of Northern Michigan.

    PubMed

    Attoh

    2000-05-01

    It is proposed that the contrasting metamorphic mineral assemblages of the isolated amphibolite facies metamorphic highs in the Penokean orogen of northern Michigan may be caused by different heat production rates in the Archean basement. This hypothesis is based on concentrations of K, U, and Th in the Archean basement gneisses and Paleoproterozoic metasediments that indicate significant contribution of radiogenic heating during Penokean metamorphism. Heat production was anomalously high ( approximately 10.6 µWm-3) where andalusite-bearing mineral assemblages indicate that high temperatures were attained at shallow crustal levels ( approximately 550 degrees -600 degrees C at approximately 3 kbar). In contrast, where exposed metamorphic rocks indicate peak temperatures of 600 degrees -650 degrees C at 6-7 kbar, heat production in the Archean basement was lower ( approximately 3.7 µWm-3). The effect of heat production rates on the metamorphic pressure-temperature paths was tested with numerical thermal models. The calculations show (1) that if the heat production rate, where andalusite-bearing assemblages formed, was significantly <6.0 µWm-3, the estimated pressure at peak temperatures (PTmax) would be much higher and lie in the sillimanite or kyanite stability fields; and (2) differences between PTmax estimates for the metamorphic highs based on thermobarometry can be reproduced if thermal history involved significant crustal thickening as well as moderate unroofing rates. PMID:10769161

  11. Age, temperature and pressure of metamorphism in the Tasriwine Ophiolite Complex, Sirwa, Morocco

    NASA Astrophysics Data System (ADS)

    Samson, S. D.; Inglis, J.; Hefferan, K. P.; Admou, H.; Saquaque, A.

    2013-12-01

    Sm-Nd garnet-whole rock geochronology and phase equilbria modeling have been used to determine the age and conditions of regional metamorphism within the Tasriwine ophiolite complex,Sirwa, Morocco. Pressure and temperature estimates obtained using a NaCaKFMASHT phase diagram (pseudosection) and garnet core and rim compositions predict that garnet growth began at ~0.72GPa and ~615°C and ended at ~0.8GPa and ~640°C. A bulk garnet Sm-Nd age of 645.6 × 1.6 Ma, calculated from a four point isochron that combines whole rock, garnet full dissolution and two successively more aggressive partial dissolutions, provides a precise date for garnet formation and regional metamorphism. The age is nearly 20 million years younger than a previous age estimate of regional metamorphism of 663 × 14 Ma based upon a SHRIMP U-Pb date from rims on zircon from the Irri migmatite. The new data provide further constraints on the age and nature of regional metamorphism in the Anti-Atlas mountains and emphasizes that garnet growth during regional metamorphism may not necessarily coincide with magmatism/anatexis which predominate the signature witnessed by previous U-Pb studies. The ability to couple PT estimates for garnet formation with high precision Sm- Nd geochronology highlights the utility of garnet studies for uncovering the detailed metamorphic history of the Anti-Atlas mountain belt.

  12. Very low-grade metamorphic rocks in some representative districts in Tibet

    NASA Astrophysics Data System (ADS)

    Bi, X.; Mo, X.

    2011-12-01

    *Response author: Bi,Xianmei,bixm10@sina.com Very low grade metamorphic rocks are widely distributed in Tibet, providing an insight into deformation and metamorphism during the evolution of the Tibetan Plateau. Eighty five Samples of clay mineral-bearing rocks has been collected from various strata including D, P1, T1, T2, T3, J1, J3, K1, K2 and N strata in the Qiangtang terrane, the Gangdese, the Yarlung Zangbo suture and the Tethyan Himalaya. Analyses and refining of clay minerals in samples have been conducted in the Laboratory of X-ray Diffraction, Institute of Petroleum Exploration. Index of illite crystallinity (Ic) along with average thickness of crystal layers of illite, reflectivity of vitrinite and of clay mineral association have been employed as indicators of degree of very low-grade metamorphism. The scheme of classification[1,2] of very-low grade metamorphism based on clay mineral indexes ( mainly index of illite crystallinity) has been used in the present work, that is, low metamorphism (Ic<0.25), higher very-low grade metamorphism (Ic = 0.25-0.30), lower very-low grade metamorphism (Ic = 0.30-0.42) and diagenesis (Ic>0.42). The analytical results show interesting information. In the Qiangtang terrane, clay minerals in the Jurassic strata have indexes of illite crystalinity (Ic) 0.47-0.70, indicating higher diagenesis and in favor of petroleum-generation. However, index of illite crystalinity (Ic) for the Devonian is 0.23, indicating low metamorphism. Indexes of illite crystalinity (Ic) for the J-K strata in middle Gangdese are mostly 0.37-0.25 (very-low grade metamorphism) and a few 0.78-0.48 (diagenesis). Indexes of illite crystalinity (Ic) for the C-P strata in eastern Gangdese are mostly 0.25-0.42 (very-low grade metamorphism) and a few 0.20-0.25 (low metamorphism). The Mesozoic and Cenozoic magmatism and related mineralization are very strong in the Gangdese, which may affect in some extent on indexes of illite crystalinity. In Tethyan Himalaya

  13. Tectono-metamorphic evolution and magmatic processes in the thermo-metamorphic aureole of the Monte Capanne pluton (Elba Island, Northern Tyrrhenian Sea, Italy).

    NASA Astrophysics Data System (ADS)

    Morelli, M.; Pandeli, E.; Principi, G.

    2003-04-01

    Introduction In this work we present new structural and petrographic data collected in the thermo-metamorphic aureole of Monte Capanne (western Elba Island) and its metamorphic evolution. In the western Elba Island the Monte Capanne monzogranitic body (ca. 7 Ma) and its thermo-metamorphic aureole crop out. At least two different tectonic units can be distinguished: the Punta Le Tombe Unit, weak re-crystallized, and the Punta Nera Unit. In the latter one the re-crystallization is strong and a pre-intrusion tectono-metamorphic framework is evident (Morelli et al., 2002). The latter is mainly constituted by thermo-metamorphosed meta-ophiolites and meta-sedimentary successions previously correlated by Barberi et al. (1969) with the un-metamorphic ones (Complex IV and V of Trevisan, 1950) cropping out in the central-eastern Elba. According to Perrin (1975) and Reutter &Spohn (1982) a pre-intrusion tectono-metamorphic framework was recognized into such rocks. As suggested by Daniel &Jolivet (1995) complex relationships between metamorphic evolution and magmatic events are also recognizable. Geological Data The Punta Nera Unit crops out all around the Monte Capanne magmatic body and the primary contact with the underlying granitoid is somewhere preserved. This unit, strongly re-crystallized and locally crosscut by aplitic and porphyritic dikes, is represented by (Coli &Pandeli, 1997; Morelli, 2000) tectonized meta-serpentinites, meta-gabbros with rodingitic dikes, rare meta-basalts and meta-ophicalcites, meta-cherts, marbles, cherty meta-limestones, phyllites and meta-limestones with rare meta-arenites intercalations. A "pre-magmatic" tectono-metamorphic framework of this unit is well evident only in its meta-sedimentary portion. The meta-sediments are deformed by syn-metamorphic isoclinal folds caractherized by N-S trending axes, west dipping axial planes and easternward vergence. A later folding and flattening event clearly post-dated the above said folds and associated

  14. Frequency and genetic background of the position 122 (Val----Ile) variant transthyretin gene in the black population.

    PubMed Central

    Jacobson, D R; Reveille, J D; Buxbaum, J N

    1991-01-01

    Transthyretin (TTR) (122 Val----Ile), caused by a point mutation which destroys a MaeIII restriction site, is associated with cardiac amyloidosis in black individuals. To estimate the frequency of the MaeIII(-) gene in the black population without overt cardiac disease, DNA from 177 black individuals without amyloidosis was amplified by the PCR around TTR codon 122 and was digested with MaeIII. The MaeIII(-) gene frequency was 4/354 (1.1%; 95% confidence interval 0.32%2.7%), suggesting that the variant is relatively common in blacks. HLA genotype testing did not suggest that the TTR (122 Val----Ile) heterozygotes were of a closely related genetic background. Images Figure 2 PMID:2063870

  15. Contribution of the hydrophobic effect to protein stability: analysis based on simulations of the Ile-96----Ala mutation in barnase.

    PubMed Central

    Prevost, M; Wodak, S J; Tidor, B; Karplus, M

    1991-01-01

    Molecular dynamics simulations have been used to compute the difference in the unfolding free energy between wild-type barnase and the mutant in which Ile-96 is replaced by alanine. The simulations yield results (-3.42 and -5.21 kcal/mol) that compare favorably with experimental values (-3.3 and -4.0 kcal/mol). The major contributions to the free energy difference arise from bonding terms involving degrees of freedom of the mutated side chain and from nonbonded interactions of that side chain with its environment in the folded protein. By comparison with simulations of an extended peptide in the absence of solvent, used as a reference state, hydration effects are shown to play a minor role in the overall free energy balance for the Ile----Ala transformation. The implications of these results for our understanding of the hydrophobic effect and its contribution to protein stability are discussed. Images PMID:1961758

  16. The 14th Ile residue is essential for Leptin function in regulating energy homeostasis in rat

    PubMed Central

    Xu, Shuyang; Zhu, Xianmin; Li, Hong; Hu, Youtian; Zhou, Jinping; He, Di; Feng, Yun; Lu, Lina; Du, Guizhen; Hu, Youjin; Liu, Tiancheng; Wang, Zhen; Ding, Guohui; Chen, Jiayu; Gao, Shaorong; Wu, Fang; Xue, Zhigang; Li, Yixue; Fan, Guoping

    2016-01-01

    LEPTIN (LEP) is a circulating hormone released primarily from white adipocytes and is crucial for regulating satiety and energy homeostasis in humans and animals. Using the CRISPR technology, we created a set of Lep mutant rats that carry either null mutations or a deletion of the 14th Ile (LEP∆I14) in the mature LEP protein. We examined the potential off-target sites (OTS) by whole-genome high-throughput sequencing and/or Sanger-sequencing analysis and found no OTS in mutant rats. Mature LEP∆I14 is incessantly produced and released to blood at a much elevated level due to the feedback loop. Structure modeling of binding conformation between mutant LEP∆I14 and LEPTIN receptor (LEPR) suggests that the conformation of LEP∆I14 impairs its binding with LEPR, consistent with its inability to activate STAT3-binding element in the luciferase reporter assay. Phenotypic study demonstrated that Lep∆I14 rats recapitulate phenotypes of Lep-null mutant rats including obesity, hyperinsulinemia, hepatic steatosis, nephropathy, and infertility. Compared to the existing ob/ob mouse models, this Lep∆I14/∆I14 rat strain provides a robust tool for further dissecting the roles of LEP in the diabetes related kidney disease and reproduction problem, beyond its well established function in regulating energy homeostasis. PMID:27378381

  17. Correlates of Self-Report of Rape Among Male School Adolescents in Ile-Ife, Nigeria.

    PubMed

    Ogunfowokan, Adesola A; Olagunju, Oluwayemisi E; Olajubu, Aanuoluwapo O; Faremi, Funmilola A; Oloyede, Ajoke S; Sharps, Phyllis W

    2016-02-01

    This study examined male adolescents' self-report of rape of adolescent girls and the socio-demographic variables that correlated with self-report of rape. Descriptive-correlational design was used and the study was conducted in five public senior secondary schools in Ile-Ife, Nigeria. Three hundred and thirty-eight male adolescents participated in the study. A structured questionnaire was used to collect data. Findings from the study revealed the mean age of the adolescent males to be 16 years, with the majority (73%) of them in the middle adolescent stage. Six percent of the adolescent males reported they had raped an adolescent girl in the past. Among the boys who reported rape, 55% reported they had raped their sexual partners, and 55% reported they had perpetrated gang rape. Smoking (p = .0001), alcohol consumption (p = .001), and birth order (p = .006) predicted self-report of rape. The coefficient of birth order showed that odds of self-report of rape by first-born male increases by 6 times compared with other children. Study findings also provided evidence that adolescent males are moving from lone rape to gang rape in intimate partner relationships. Male adolescents are important group to target in rape prevention programs. PMID:25381280

  18. Child-rearing practices among nursing mothers in Ile-Ife, Nigeria.

    PubMed

    Odebiyi, A I

    1985-01-01

    This study attempts to highlight the relationship between the educational status of mothers in Ile-Ife and their child-rearing practices. It was observed that the educated mothers in good jobs spent less time at home with the children than the illiterates who have their children with them at the farms and in the market places. Thus, a higher proportion of the educated mothers admitted to using more bottle feeding than breast feeding, and forced hand-feeding which was practised by all the illiterate women interviewed. Only one educated woman still practices female circumcision. Of interest in the study is the fact that the children of the different categories of women are exposed to different types of health hazards; while the children of the educated suffer neglect and are deprived of the advantages of breast feeding, the children of the illiterate suffer from undue exposure to unhygienic conditions in the farms and market places and from the implications of forced hand-feeding and female circumcision. PMID:4075501

  19. The Lac Des Iles Palladium Deposit, Ontario, Canada. Part II. Halogen variations in apatite

    NASA Astrophysics Data System (ADS)

    Schisa, Paul; Boudreau, Alan; Djon, Lionnel; Tchalikian, Arnaud; Corkery, John

    2015-03-01

    Analysis of apatite from the Mine Block Intrusion (MBI) of the Lac des Iles Igneous Complex shows two pronounced trends in the halogens. Apatite from relatively fresh norite and melanorites from the Pd-sulfide zone contain up to 57 mol% chlorapatite endmember with significant hydroxyapatite component. In contrast, in altered rock (amphibolite and greenschist assemblages) the chlorapatite component is typically less than 10 mol% with wide variation in the F- and OH-endmember components. The latter trend is attributed to Cl loss to degassing and alteration, whereas the former is attributed to Cl enrichment in the ore-bearing rocks. It is suggested that the relatively H2O-rich and intermediate Cl content of the early igneous fluids degassed from the deeper levels of the MBI can explain the high Pd/Pt and Pd/Ir ratios of the deposit. A model is presented in which disseminated Pd-rich sulfides are initially introduced by a high-temperature magmatic fluid that also influenced crystallization to produce the gross modal variations of the igneous host rock. This high-temperature mineralization event was subsequently modified by the influx of late igneous and country fluids at amphibolite to greenschist conditions.

  20. Halogen Variations in Apatite of the Lac Des Iles Palladium Deposit, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Boudreau, A. E.

    2014-12-01

    Analysis of apatite from the Mine Block Intrusion (MBI) of the Lac des Iles Igneous Complex show two pronounced trends in the halogens. Apatite from relatively fresh norite and melanorites from the Pd-sulfide zone contain up to 57 mole % chlorapatite endmember with significant hydroxyapatite component. In contrast, in altered rock (amphibolite and greenschist assemblages) and in the more evolved barren rocks the chlorapatite component is typically less than 10 mole % with wide variation in the F- and OH-endmember components. The latter trend is attributed to Cl loss to degassing and alteration whereas the former is attributed to Cl-enrichment in the ore-bearing rocks. It is suggested that the relatively H2O-rich and intermediate Cl content of the early igneous fluids degassed from the deeper levels of the MBI can explain the high Pd/Pt and Pd/Ir ratios of the deposit. A model is presented in which disseminated Pd-rich sulfide are initially introduced by a high temperature magmatic fluid that also influenced crystallization to produce the gross modal variations of the igneous host rock. This high temperature mineralization event was subsequently modified by the influx of late igneous and country fluids at amphibolite to greenschist conditions.

  1. Plankton communities in the five Iles Eparses (Western Indian Ocean) considered to be pristine ecosystems

    NASA Astrophysics Data System (ADS)

    Bouvy, M.; Got, P.; Domaizon, I.; Pagano, M.; Leboulanger, C.; Bouvier, C.; Carré, C.; Roques, C.; Dupuy, C.

    2016-04-01

    Coral reef environments are generally recognized as being the most threatened of marine ecosystems. However, it is extremely difficult to distinguish the effects of climate change from other forcing factors, mainly because it is difficult to study ecosystems that are isolated from human pressure. The five Iles Eparses (Scattered Islands) are located in the Western Indian Ocean (WIO) and can be considered to be "pristine" ecosystems not subject to anthropogenic pressure. This study characterized their plankton assemblages for the first time, by determining the abundances of microbial (virus, bacteria, heterotrophic protists and phytoplankton) and metazooplankton communities in various lagoon and ocean sites around each island. The Europa lagoon has extensive, productive mangrove forests, which have the highest nutrient concentrations (nitrogen forms, dissolved organic carbon) and whose microbial communities present a peculiar structure and functioning. By means of bioassay experiments, we observed that bacterial production and growth rates are higher in Europa than those reported for the other islands. Tromelin, which lies outside the Mozambique Channel, had the lowest biological productivity, nutrient concentrations, and bacterial growth rates. Multivariate analysis indicated that distinct microbial assemblages occur in association to varying nutrient concentrations. Molecular fingerprinting showed clear discrimination of the structure of the archaea, bacteria and eukaryotes community between the sites. Our results suggest that the geographical distance can influence the diversity of dominant microbial taxa in the WIO.

  2. The 14th Ile residue is essential for Leptin function in regulating energy homeostasis in rat.

    PubMed

    Xu, Shuyang; Zhu, Xianmin; Li, Hong; Hu, Youtian; Zhou, Jinping; He, Di; Feng, Yun; Lu, Lina; Du, Guizhen; Hu, Youjin; Liu, Tiancheng; Wang, Zhen; Ding, Guohui; Chen, Jiayu; Gao, Shaorong; Wu, Fang; Xue, Zhigang; Li, Yixue; Fan, Guoping

    2016-01-01

    LEPTIN (LEP) is a circulating hormone released primarily from white adipocytes and is crucial for regulating satiety and energy homeostasis in humans and animals. Using the CRISPR technology, we created a set of Lep mutant rats that carry either null mutations or a deletion of the 14(th) Ile (LEP(∆I14)) in the mature LEP protein. We examined the potential off-target sites (OTS) by whole-genome high-throughput sequencing and/or Sanger-sequencing analysis and found no OTS in mutant rats. Mature LEP(∆I14) is incessantly produced and released to blood at a much elevated level due to the feedback loop. Structure modeling of binding conformation between mutant LEP(∆I14) and LEPTIN receptor (LEPR) suggests that the conformation of LEP(∆I14) impairs its binding with LEPR, consistent with its inability to activate STAT3-binding element in the luciferase reporter assay. Phenotypic study demonstrated that Lep(∆I14) rats recapitulate phenotypes of Lep-null mutant rats including obesity, hyperinsulinemia, hepatic steatosis, nephropathy, and infertility. Compared to the existing ob/ob mouse models, this Lep(∆I14/∆I14) rat strain provides a robust tool for further dissecting the roles of LEP in the diabetes related kidney disease and reproduction problem, beyond its well established function in regulating energy homeostasis. PMID:27378381

  3. Novel EDA p.Ile260Ser mutation linked to non-syndromic hypodontia.

    PubMed

    Yang, Y; Luo, L; Xu, J; Zhu, P; Xue, W; Wang, J; Li, W; Wang, M; Cheng, K; Liu, S; Tang, Z; Ring, B Z; Su, L

    2013-06-01

    Hypodontia, a tooth developmental disease, can affect chewing and pronunciation. Mutations in the ectodysplasin-A (EDA) gene can lead to both X-linked hypohidrotic ectodermal dysplasia (XLHED) and non-syndromic hypodontia (NSH). However, the mechanism by which these 2 related but different disorders are caused by the distinct mutations in EDA is unknown. In this study, we identified a novel missense mutation (c.779 T>G) in a Chinese family with NSH via a direct sequencing approach. This mutation results in an Ile260Ser substitution in the tumor necrosis factor (TNF) homology domain. Homology modeling suggests that this alteration may induce a conformational change in the hydrophobic center of the TNF homology domain. Furthermore, by exploring systematic 3D conformation analysis and calculation of residue relative solvent accessibility (RSA) for all the reported mutated amino acid sites on EDA's TNF homology domain, we found that the site mutations at the interior may be linked to XLHED, while those at the surface are more likely to be associated with NSH. These findings may aid in the discovery of unidentified functionally significant mutation sites in the EDA gene and provide a new way to clarify the mechanisms by which the XLHED and NSH phenotypes arise from mutations in the same gene. PMID:23625373

  4. Investigation of Ionospheric response to Geomagnetic Storms over a Low Latitude Station, Ile-Ife, Nigeria

    NASA Astrophysics Data System (ADS)

    Jimoh, Oluwaseyi E.; Yesufu, Thomas K.; Ariyibi, Emmanuel A.

    2016-05-01

    Due to several complexities associated with the equatorial ionosphere, and the significant role which the total electron content (TEC) variability plays in GPS signal transmission, there is the need to monitor irregularities in TEC during storm events. The GPS SCINDA receiver data at Ile-Ife, Nigeria, was analysed with a view to characterizing the ionospheric response to geomagnetic storms on 9 March and 1 October 2012. Presently, positive storm effects, peaks in TEC which were associated with prompt penetration of electric fields and changes in neutral gas composition were observed for the storms. The maximum percentage deviation in TEC of about 120 and 45% were observed for 9 March and 1 October 2012, respectively. An obvious negative percentage TEC deviation subsequent to sudden storm commencement (SSC) was observed and besides a geomagnetic storm does not necessarily suggest a high scintillation intensity (S4) index. The present results show that magnetic storm events at low latitude regions may have an adverse effect on navigation and communication systems.

  5. Identification of the PS1 Thr147Ile Variant in a Family with Very Early Onset Dementia and Expressive Aphasia

    PubMed Central

    Denvir, James; Neitch, Shirley; Fan, Jun; Niles, Richard M.; Boskovic, Goran; Schreurs, Bernard G.; Primerano, Donald A.; Alkon, Daniel L.

    2015-01-01

    Abstract Background: Early onset dementias have variable clinical presentations and are often difficult to diagnose. We established a family pedigree that demonstrated consistent recurrence of very early onset dementia in successive generations. Objective and Method: In order to refine the diagnosis in this family, we sequenced the exomes of two affected family members and relied on discrete filtering to identify disease genes and the corresponding causal variants. Results: Among the 720 nonsynonymous single nucleotide polymorphisms (SNPs) shared by two affected members, we found a C to T transition that gives rise to a Thr147Ile missense substitution in the presenilin 1 (PS1) protein. The presence of this same mutation in a French early-onset Alzheimer’s disease family, other affected members of the family, and the predicted high pathogenicity of the substitution strongly suggest that it is the causal variant. In addition to exceptionally young age of onset, we also observed significant limb spasticity and early loss of speech, concurrent with progression of dementia in affected family members. These findings extend the clinical presentation associated with the Thr147Ile variant. Lastly, one member with the Thr147Ile variant was treated with the PKC epsilon activator, bryostatin, in a compassionate use trial after successful FDA review. Initial improvements with this treatment were unexpectedly clear, including return of some speech, increased attentional focus, ability to swallow, and some apparent decrease in limb spasticity. Conclusions: Our findings confirm the role of the PS1 Thr147Ile substitution in Alzheimer’s disease and expand the clinical phenotype to include expressive aphasia and very early onset of dementia. PMID:25812849

  6. Thr130Ile polymorphism of HNF4A gene is associated with gestational diabetes mellitus in Mexican population.

    PubMed

    Monroy, Virginia Sánchez; Díaz, César Antonio González; Trenado, Lucila Maritza Lozano; Peralta, José Manuel Campos; Soto, Salvador Martín Polo

    2014-03-01

    Hepatocyte nuclear factor 4α (HNF4A) is a transcription factor that regulates the expression of genes in the liver, pancreas, kidney, intestine, and other tissues. Previous studies in the Mexican population have shown a high frequency of the Thr130Ile polymorphism and have suggested its important role in the pathogenesis of early-onset type 2 diabetes. The aim of the present study was to determine whether this variant also contributes to gestational diabetes mellitus (GDM) in a Mexican population. We studied 213 unrelated postpartum women and their neonates, who were divided into 2 groups: control and GDM. The control group was formed by 108 healthy postpartum women and their neonates, and the GDM group was formed by 105 postpartum women diagnosed with GDM and their neonates. All subjects were genotyped for the Thr130Ile polymorphism in HNF4A by Taqman allelic discrimination assays and sequencing. Our results showed a higher frequency of the minor allele of the Thr130Ile polymorphism in the GDM group compared with the control group (P = 0.0452; odds ratio, 2.59; 95% confidence interval, 1.02-6.59). With respect to offspring, the frequency of the polymorphism was higher in the offspring of the GDM group than in the offspring of the control group; however, no significant differences between the groups were observed (P = 0.2551; odds ratio, 1.90; 95% confidence interval, 0.99-3.64). The findings suggest that the Thr130Ile polymorphism is associated with GDM in the studied Mexican population. PMID:24448600

  7. Multimodal approach to explore the pathogenicity of BARD1, ARG 658 CYS, and ILE 738 VAL mutants.

    PubMed

    Choudhary, Rajan Kumar; Vikrant; Siddiqui, Quadir M; Thapa, Pankaj S; Raikundalia, Sweta; Gadewal, Nikhil; Kumar, Nachimuthu Senthil; Hosur, M V; Varma, Ashok K

    2016-07-01

    BARD1-BRCA1 complex plays an important role in DNA damage repair, apoptosis, chromatin remodeling, and other important processes required for cell survival. BRCA1 and BARD1 heterodimer possess E3 ligase activity and is involved in genome maintenance, by functioning in surveillance for DNA damage, thereby regulating multiple pathways including tumor suppression. BRCT domains are evolutionary conserved domains present in different proteins such as BRCA1, BARD1, XRCC, and MDC1 regulating damage response and cell-cycle control through protein-protein interactions. Nonetheless, the role of BARD1BRCT in the recruitment of DNA repair mechanism and structural integrity with BRCA1 complex is still implicit. To explicate the role of BARD1BRCT in the DNA repair mechanism, in silico, in vitro, and biophysical approach were applied to characterize BARD1 BRCT wild-type and Arg658Cys and Ile738Val mutants. However, no drastic secondary and tertiary structural changes in the mutant proteins were observed. Thermal and chemical denaturation studies revealed that mutants Arg658Cys and Ile738Val have a decrease in Tm and ∆G than the wild type. In silico studies of BARD1 BRCT (568-777) and mutant protein indicate loss in structural compactness on the Ile738Val mutant. Comparative studies of wild-type and mutants will thus be helpful in understanding the basic role of BARD1BRCT in DNA damage repair. PMID:26307947

  8. Intestinal transport of the lactokinin Ala-Leu-Pro-Met-His-Ile-Arg through a Caco-2 Bbe monolayer.

    PubMed

    Vermeirssen, V; Deplancke, B; Tappenden, K A; Van Camp, J; Gaskins, H R; Verstraete, W

    2002-03-01

    ACE inhibitory peptides are biologically active peptides that play a role in blood pressure regulation. When derived from food proteins during food processing or gastrointestinal digestion, these peptides could function as efficient agents in treating and preventing hypertension. However, in order to exert an antihypertensive effect by inhibition of the ACE enzyme, they have to reach the bloodstream intact. The aim of this research was to assess if the known ACE inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg, derived from a tryptic digest of beta-lactoglobulin, could be absorbed through a Caco-2 Bbe cell monolayer in an Ussing chamber and reach the serosal side undegraded. Samples of the mucosal compartment showed high ACE inhibitory activity. No or only little ACE inhibitory activity was detected in the serosal compartment. However, when the serosal sample was concentrated three-fold, a substantial ACE inhibitory activity was registered. Concomitantly, HPLC and MS clearly showed the presence of Ala-Leu-Pro-Met-His-Ile-Arg in the mucosal compartment, whereas in the serosal compartment only MS was able to detect the heptapeptide. In conclusion. under the observed experimental conditions, the ACE inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg was transported intact through the Caco-2 Bbe monolayer, but in concentrations too low to exert an ACE inhibitory activity. PMID:11931586

  9. Insulin signaling regulates neurite growth during metamorphic neuronal remodeling

    PubMed Central

    Gu, Tingting; Zhao, Tao; Hewes, Randall S.

    2014-01-01

    Summary Although the growth capacity of mature neurons is often limited, some neurons can shift through largely unknown mechanisms from stable maintenance growth to dynamic, organizational growth (e.g. to repair injury, or during development transitions). During insect metamorphosis, many terminally differentiated larval neurons undergo extensive remodeling, involving elimination of larval neurites and outgrowth and elaboration of adult-specific projections. Here, we show in the fruit fly, Drosophila melanogaster (Meigen), that a metamorphosis-specific increase in insulin signaling promotes neuronal growth and axon branching after prolonged stability during the larval stages. FOXO, a negative effector in the insulin signaling pathway, blocked metamorphic growth of peptidergic neurons that secrete the neuropeptides CCAP and bursicon. RNA interference and CCAP/bursicon cell-targeted expression of dominant-negative constructs for other components of the insulin signaling pathway (InR, Pi3K92E, Akt1, S6K) also partially suppressed the growth of the CCAP/bursicon neuron somata and neurite arbor. In contrast, expression of wild-type or constitutively active forms of InR, Pi3K92E, Akt1, Rheb, and TOR, as well as RNA interference for negative regulators of insulin signaling (PTEN, FOXO), stimulated overgrowth. Interestingly, InR displayed little effect on larval CCAP/bursicon neuron growth, in contrast to its strong effects during metamorphosis. Manipulations of insulin signaling in many other peptidergic neurons revealed generalized growth stimulation during metamorphosis, but not during larval development. These findings reveal a fundamental shift in growth control mechanisms when mature, differentiated neurons enter a new phase of organizational growth. Moreover, they highlight strong evolutionarily conservation of insulin signaling in neuronal growth regulation. PMID:24357229

  10. The metamorphic evolution of the Kathmandu Nappe area

    NASA Astrophysics Data System (ADS)

    Zhuk, Yuliya

    2016-04-01

    The Kathmandu Nappe area in central Nepal was initially discovered in the beginning of the 70s and mapped some years later. While the first investigation showed that the Kathmandu Nappe belonged to the less metamorphosed sedimentary and volcanic formations, later findings proved the Kathmandu Nappe to have a distinct lithology and stratigraphy with a separate metamorphic evolution. The aim of this project is to further investigate the geologic evolution of the area. The proposed method for investigation is to perform a detailed geological mapping of the area, collect rock samples based on the mapped information and analyse the samples using optical microscope analysis and zircon crystal morphology analysis. The Kathmandu Nappe forms a huge N100° synclinorium, divided into the lower Bhimpedi group, the Phulchauki group and the Cambrian-Ordovician granites. Detailed geological maps will be generated by focusing on the contact between the metasediment and Palung-, Ipa-, and Agragranite bodies. There are two expected findings. For one, the granite is expected to be younger than the metasediment, suggesting them to be caused by two different tectonic events. This would mean that the granite shows a clear intrusive relation with many pre-existing faults, and, therefore, that it was little affected by faulting. To prove or discard this, a detailed geological mapping will be used. For two, the granite is expected to have a crustal origin. This would mean that the magma generation probably occurred through anatexis of continental crust. To prove or discard this, the origin of the granite bodies will be identified and compared using optical microscope analysis and zircon crystal morphology.

  11. Fluid infiltration of the Tudor Gabbro during regional metamorphism

    SciTech Connect

    Dunn, S.R.; Valley, J.W.

    1985-01-01

    The Tudor Gabbro (TG), an ovate body (4 x 9 km) 40 km SE of Bancroft. Ontario, was metamorphosed to upper greenschist facies along with surrounding sediments and volcanics. Allen (1976) delineated concentric isograds around the gabbro, including +sphene, +tremolite (to 1.5 km), +tremolite + clinozoisite, +diopside (approx. 120 m), and +garnet (approx. 80 m). Metamorphic conditions are inferred to be 490+/-50/sup 0/C, 5 kb with no thermal gradient. Allen suggested that H/sub 2/O infiltration of the marble and calc-schist accounts for the isograds. The gabbro mineralogy of titanaugite, andesine to labradorite, and minor hornblende is extensively recrystallized to albite and/or oligoclase + actinolite + epidote + ilmenite + calcite (up to 4 wt%) +/- biotite +/- chlorite +/- sphene +/- scapolite. Isotopic analyses of calcite from 39 TG samples show delta/sup 18/O = 9.4 to 16.6 and delta/sup 13/C = -1.9 to 3.4. Bulk silicate delta/sup 18/O of TG range from 7.1 to 10.2. Calcites in metasediment have delta/sup 18/O = 18.1 to 25.3 and delta/sup 13/C = 1.3 to 5.6. Two whole rock silicate analyses of a skarn developed locally at the contact show intermediate delta/sup 18/O of 16.2 and 17.3. The stability of Czo component in epidote requires H/sub 2/O-rich fluids. The delta/sup 13/C of TG calcites average +0.7 nearly identical to the average of 178 carbonates from Grenville marbles (+1.0), showing that metasediment-derived CO/sub 2/ pervasively infiltrated the TG. The infiltration of H/sub 2/O into both the TG and the metasediment suggests that H/sub 2/O-rich fluids migrated upward along the contact.

  12. The Chicxulub crater - impact metamorphism of sulfate and carbonate lithologies

    NASA Astrophysics Data System (ADS)

    Deutsch, A.; Langenhorst, F.; Hornemann, U.; Ivanov, B. A.

    2003-04-01

    It is discussed whether in the aftermath of the Chicxulub event, impact-released CO_2 and SO_x have changed the Earth's climate, acting also as lethal thread for life. Undoubtedly, vaporization of carbonates and sulfates, which are major target lithologies at the Chicxulub impact site, occurred in the footprint of the projectile. What happened to these lithologies outside this very restricted zone was so far unconstrained. Petrologic observations on PEMEX and UNAM as well as on the CSDP cores allow to set up a general classification for shock-related pro-grade effects on sulfate and carbonate sedimentary rocks. Shock effects in lithic breccias are restricted to brecciation and formation of twins in calcite. Suevites mostly lack melted carbonate clasts; annealing effects in anhydrite fragments are absent. The underlying melt breccias contain anhydrite fragments still displaying a sedimentary texture, and limestone clasts, whose texture reflect crystallization from melt. Impact melt breccias from deeper levels frequently contain partially resorbed anhydrite clasts and a melt matrix with the Ca-rich mineral assemblage quartz + plagioclase + clinopyroxene; this mineral assemblage provides evidence for partial dissociation of CaSO_4. Large clasts of anhydrite consist of equant crystals with 120^o triple junctions, a feature indicative for re-crystallization in the solid state. Tagamites (impact melt rocks) are virtually free of clasts from sedimentary lithologies. These rocks have an extremely high formation temperature, which caused total dissociation of CaSO_4 and CaCO_3. Finally, up to 100 μm wide veins of anhydrite + calcite + quartz cut the matrix of all lithologies except the tagamites. They probably represent "degassing vents". The given scheme is in qualitative accordance with data of shock recovery and annealing experiments as well as with modeling results. In addition, it substantiates that annealing plays a fundamental role in the impact metamorphism of

  13. The association of the CYP1A1 Ile462Val polymorphism with head and neck cancer risk: evidence based on a cumulative meta-analysis

    PubMed Central

    Wang, Yadong; Yang, Haiyan; Duan, Guangcai; Wang, Haiyu

    2016-01-01

    Objective The aim of this study was to address the association between the Ile462Val polymorphism in the gene encoding cytochrome P450 1A1 (CYP1A1) and the risk of head and neck cancer (HNC). Materials and methods The Medline/PubMed, EMBASE, and Web of Science databases were searched. The strength of the association was evaluated by calculating the odds ratio (OR) with a 95% confidence interval (CI). Results Overall, we observed an increased risk of HNC in patients with the Ile/Val+Val/Val genotype compared to those with the Ile/Ile genotype among the 6,367 cases and 6,395 controls evaluated in the 34 eligible studies, with a pooled OR of 1.284 (95% CI: 1.119–1.473). In addition, we observed an increased risk of HNC in patients with the Ile/Val+Val/Val genotype compared to those with the Ile/Ile genotype in the subgroup analyses (OR =1.362, 95% CI: 1.102–1.685 for laryngeal cancer; OR =1.519, 95% CI: 1.253–1.843 for pharyngeal cancer; OR =1.371, 95% CI: 1.111–1.693 for Asians; and OR =1.329, 95% CI: 1.138–1.551 for patients in studies using hospital-based controls). Conclusion This cumulative meta-analysis suggests that the CYP1A1 Ile462Val polymorphism might contribute to the risk of HNC, particularly for pharyngeal cancer and laryngeal cancer. PMID:27274286

  14. First pressure- and temperature estimates of the metamorphic sole of the Pinarbasi ophiolite, central Turkey

    NASA Astrophysics Data System (ADS)

    Peters, Kalijn; van Hinsbergen, Douwe; van Roermund, Herman; Brouwer, Fraukje; Drury, Martyn

    2014-05-01

    Ophiolites are interpreted as remnants of oceanic lithosphere. Many have a so-called supra-subduction zone (SSZ) geochemical signature, suggestive of formation at a spreading ridge overlying a subduction zone. Supra-subduction zone ophiolites frequently have a several-hundred-meter thick sequence of metamorphic rocks below their mantle section: the metamorphic sole. These dominantly mafic and generally heavily sheared metamorphic rocks have been shown to preserve an inverted metamorphic gradient with the highest pressures and temperatures at the top of the sole, decreasing downwards. Pressure estimates from rocks found at the top of metamorphic soles may be as much as 10-15 kbar with temperature estimates up to 875°C. The metamorphic grade varies from greenschist near the base, up to granulite facies at the top, with the bulk comprising of amphibolite facies rocks. At some locations a blueschist overprint of the amphibolite facies mineral assemblages has been described. The relative high pressures preserved in the metamorphic sole cannot simply result from overburden pressure of the currently overlying ophiolite, which is a long-standing problem. This raises the question of what process(es) can explain pressures up to 10-15 kbar in the top of metamorphic soles, in relation to the approximately synchronous formation of the SSZ oceanic lithosphere above the sole. One of the places to study the formation of SSZ ophiolites and their metamorphic soles is the Neotethyan Suture zone. Remnants of Neotethyan lithosphere are preserved as ophiolites that are discontinuously exposed from the Mediterranean region through the Himalaya to SE Asia. Supra-subduction zone ophiolites are particularly widespread in Turkey. The Pinarbaşi ophiolite is located in the SE of Central Anatolia, and overlies the Tauride fold-and-thrust belt that formed since the Late Cretaceous. It comprises mantle tectonites consisting of serpentinized harzburgite and dunite with remnants of gabbro to the

  15. Evolution of the angrite parent body: Implications of metamorphic coronas in NWA 3164

    NASA Astrophysics Data System (ADS)

    Baghdadi, Bashar; Godard, Gaston; Jambon, Albert

    2013-10-01

    Northwest Africa 3164 is a coarse-grained angrite that shows reaction coronas, a unique character among achondrites. Olivine (Fo57; 1.2 wt% CaO), fassaitic clinopyroxene, anorthite, and spinel account for 46-47, 28-29, 8-13, and 4-8 vol%, respectively; kamacite is an accessory phase. The spinel grains in contact with clinopyroxene are bounded by discontinuous 20 μm thick coronas of anorthite and olivine, indicating the reaction Cpx + Spl → Ol + An (R1). In addition, irregular coronas of clinopyroxene and spinel developed around the primary anorthite in contact with primary olivine, during the reaction Ol + An → Cpx + Spl (R2). R2 also generated clinopyroxene and spinel films between the secondary olivine and anorthite coronas produced during R1, implying that R1 preceded R2. Both are metamorphic reactions that developed in the solid state. Finally, the coronas are cross cut by μm-thick veinlets due to a late shock. A mass-balance study shows that R2 is almost the reverse of R1. The P-T metamorphic evolution of the rock, modeled by calculating a P-T isochemical diagram, indicates an equilibrium T of 940 ± 120 °C at P < 0.9 GPa for the initial assemblage, followed by an increase of T up to approximately 1000-1200 °C during reaction R1 and a subsequent cooling during R2. Several causes are envisaged to account for this metamorphic evolution. Contact metamorphism due to a hot magmatic intrusion in the angrite parent body is favored, as similar metamorphic coronas are well known in metamorphic terrestrial rocks. In addition to differentiation and magmatism, there is now evidence for metamorphism in the angrite parent body, which would have been a large asteroid or a planetary-sized body.

  16. Pressure-temperature evolution of Neoproterozoic metamorphism in the Welayati Formation (Kabul Block), Afghanistan

    NASA Astrophysics Data System (ADS)

    Collett, Stephen; Faryad, Shah Wali

    2015-11-01

    The Welayati Formation, consisting of alternating layers of mica-schist and quartzite with lenses of amphibolite, unconformably overlies the Neoarchean Sherdarwaza Formation of the Kabul Block that underwent Paleoproterozoic granulite-facies and Neoproterozoic amphibolite-facies metamorphic events. To analyze metamorphic history of the Welayati Formation and its relations to the underlying Sherdarwaza Formation, petrographic study and pressure-temperature (P-T) pseudosection modeling were applied to staurolite- and kyanite-bearing mica-schists, which crop out to the south of Kabul City. Prograde metamorphism, identified by inclusion trails and chemical zonation in garnet from the micaschists indicates that the rocks underwent burial from around 6.2 kbar at 525 °C to maximum pressure conditions of around 9.5 kbar at temperatures of around 650 °C. Decompression from peak pressures under isothermal or moderate heating conditions are indicated by formation of biotite and plagioclase porphyroblasts which cross-cut and overgrow the dominant foliation. The lack of sillimanite and/or andalusite suggests that cooling and further decompression occurred in the kyanite stability field. The results of this study indicate a single amphibolite-facies metamorphism that based on P-T conditions and age dating correlates well with the Neoproterozoic metamorphism in the underlying Sherdarwaza Formation. The rocks lack any paragenetic evidence for a preceding granulite-facies overprint or subsequent Paleozoic metamorphism. Owing to the position of the Kabul Block, within the India-Eurasia collision zone, partial replacement of the amphibolite-facies minerals in the micaschist could, in addition to retrogression of the Neoproterozoic metamorphism, relate to deformation associated with the Alpine orogeny.

  17. 40Ar/39Ar thermochronology of mesoproterozoic metamorphism in the Colorado Front Range

    USGS Publications Warehouse

    Shaw, C.A.; Snee, L.W.; Selverstone, J.; Reed, J.C., Jr.

    1999-01-01

    A low-pressure metamorphic episode in the Colorado Front Range has been identified by the presence of staurolite, andalusite, cordierite, and garnet porphyroblasts overprinting earlier assemblages. The overprinting assemblages and reaction textures are most consistent with porphyroblast growth on a prograde metamorphic path with peak temperatures exceeding ~525??C. Twenty-eight 40Ar/39Ar dates on hornblende, muscovite, biotite, and microcline were used to infer the age and thermal conditions of metamorphism. Muscovite and biotite 40Ar/39Ar ages fall mainly in the interval 1400-1340 Ma, consistent with cooling through the closure temperature interval of micas (~400??-300??C) after about 1400 Ma. In contrast, hornblende apparent ages (T(c)~500??-550??C) between 1600 and 1390 Ma reflect variable retention of radiogenic argon. Forward modeling of argon diffusion shows that the distribution of hornblende and mica ages is consistent with the partial resetting of argon systematics ca. 1400 Ma by a thermal pulse reaching maximum temperatures around 550??C and decaying within <20 m.yr. These temperatures match the conditions inferred from the overprinting assemblage; thus, muscovite and biotite ages are interpreted to date the cooling phase of this metamorphic event. This late metamorphism is broadly coeval with the intrusion of ca. 1400-Ma granitic plutons in the study area and throughout the southwestern United States. However, thermal effects are observed far from pluton margins, suggesting pervasive, regional crustal heating rather than restricted contact metamorphism. Our results suggest that ca. 1400-Ma metamorphism and plutonism are manifestations of a regional thermal episode that both partially melted the lower crust and pervasively metamorphosed middle crustal rocks.

  18. The eastern limit of Acadian high grade metamorphism in northern New England: Implications for the location of the Acadian Suture''

    SciTech Connect

    West, D.P. Jr. . Dept. of Geological Sciences)

    1993-03-01

    Identifying the eastern limit of Acadian high grade metamorphism in New England is complicated by the presence of pre-Devonian high grade relics, locally intense Late Paleozoic thermal overprints, and post-metamorphic faults. New [sup 40]Ar/[sup 39]Ar mineral ages from along the eastern margin of high grade metamorphism in Maine and New Hampshire help delineate the eastern limit of Devonian amphibolite facies metamorphism thereby placing constraints on the location of the Acadian suture. In New Hampshire, Acadian high grade metamorphism extends southeast at least as far as the Campbell Hill fault and perhaps as far as the Flint Hill fault. New [sup 40]Ar/[sup 39]Ar hornblende ages and previously published U-Pb monazite ages from the Massabesic Gneiss Complex are Permian indicating high grade Alleghanian metamorphism. New [sup 40]Ar/[sup 39]Ar hornblende ages from the Rye Formation, although complicated by excess argon, are considerably older, indicating an earlier Pre-Silurian amphibolite facies metamorphism affected these rocks. North of Portland, [sup 40]Ar/[sup 39]Ar hornblende ages east of the Norumbega Fault Zone from high grade rocks of the Casco Bay Group have ages that range from Middle Devonian to Early Carboniferous, consistent with diachronous cooling following Acadian metamorphism. Further northeast, in upper amphibolite facies rocks of the Passagassawakeag Gneiss, new [sup 40]Ar/[sup 39]Ar hornblende ages range from 385--395 Ma suggesting that these rocks were also affected by high grade Acadian metamorphism.

  19. 40Ar/39Ar and K-Ar data bearing on the metamorphic and tectonic history of western New England.

    USGS Publications Warehouse

    Sutter, J.F.; Ratcliffe, N.M.; Mukasa, S.B.

    1985-01-01

    40Ar/39Ar ages of coexisting biotite and hornblende from Proterozoic Y gneisses of the Berkshire and Green Mt massifs, as well as 40Ar/39Ar and K/Ar mineral and whole-rock ages from Palaeozoic metamorphic rocks, suggest that the thermal peaks for the dominant metamorphic recrystallization in western New England occurred 465 + or - 5 m.y. (Taconian). 40Ar/39Ar age data from a poorly-defined terrain along the eastern strip of the area suggests that the area has been retrograded during a metamorphism that peaked at least 376 + or - 5 m.y. (Acadian). Available age and petrological data from western New England indicate the presence of at least three separate metamorphic-structure domains of Taconic age: 1) a small area of relict high-P and low-T metamorphism, 2) a broad area of normal Barrovian metamorphism from chlorite to garnet grade characterized by a gentle metamorphic gradient and, 3) a rather narrow belt of steep-gradient, Barrovian series metamorphic rocks. Areas of maximum metamorphic intensity within the last domain coincide with areas of maximum crustal thickening in the later stage of Taconic orogeny. -L.di H

  20. Development of III-Sb metamorphic DBR membranes on InP for vertical cavity laser applications

    NASA Astrophysics Data System (ADS)

    Addamane, S. J.; Mansoori, A.; Renteria, E. J.; Dawson, N.; Shima, D. M.; Rotter, T. J.; Hains, C. P.; Dawson, L. R.; Balakrishnan, G.

    2016-04-01

    Sb-based metamorphic DBR membranes are developed for InP-based vertical cavity laser applications. The reflectivity of the metamorphic DBR membrane is compared to the reflectivity of a lattice-matched DBR to characterize the optical quality of the DBR membrane. The metamorphic interface between InP and the III-antimonides is found to degrade the reflectivity of the DBR. Therefore, the growth temperature for the metamorphic DBR is optimized in order to obtain highly reflective (>99.8%) III-Sb thin-film membranes.

  1. Monitoring austral and cyclonic swells in the "Iles Eparses" (Mozambique channel) from microseismic noise

    NASA Astrophysics Data System (ADS)

    Barruol, Guilhem; Davy, Céline; Fontaine, Fabrice R.; Schlindwein, V.; Sigloch, K.

    2016-04-01

    We deployed five broadband three-components seismic stations in the Iles Eparses in the south-west Indian Ocean and on Mayotte Island, between April 2011 and January 2014. These small and remote oceanic islands suffer the effects of strong ocean swells that affect their coastal environments but most islands are not instrumented by wave gauges to characterize the swells. However, wave action on the coast causes high levels of ground vibrations in the solid earth, so-called microseismic noise. We use this link between the solid earth and ocean wave activity to quantify the swells locally. Spectral analyses of the continuous seismic data show clear peaks in the 0.05-0.10 Hz frequency band (periods between 10 and 20 s), corresponding to the ocean wave periods of the local swells. We analyze an example of austral swell occurring in August 2013 and a cyclonic event (Felleng) that developed in January 2013, and quantify the ground motion at each station induced by these events. In both cases, we find a linear polarization in the horizontal plane with microseismic amplitude directly correlated to the swell height (as predicted by the global swell model WaveWatchIII), and a direction of polarization close to the predicted swell propagation direction. Although this analysis has not been performed in real time, it demonstrates that terrestrial seismic stations can be efficiently used as wave gauges, and are particularly well suited for quantifying extreme swell events. This approach may therefore provide useful and cheaper alternatives to wave buoys for monitoring swells and the related environmental processes such as beach erosion or coral reef damages.

  2. A novel homozygous LMNA mutation (p.Met540Ile) causes mandibuloacral dysplasia type A.

    PubMed

    Yassaee, Vahid Reza; Khojaste, Arash; Hashemi-Gorji, Feyzollah; Ravesh, Zeinab; Toosi, Parviz

    2016-02-10

    Mandibuloacral dysplasia with type A lipodystrophy (MADA) is a rare genetic disorder inherited in an autosomal recessive fashion characterized by hypoplasia of the mandible and clavicles, acroosteolysis and lipodystrophy due to mutations in the LMNA or ZMPSTE24 genes. In the current study, we have investigated a consanguineous family clinically diagnosed with mandibuloacral dysplasia type A having an affected child for the LMNA gene alteration(s). Mother is now 15weeks pregnant, seeking advice on the health of her fetus. Peripheral blood was obtained from all family members after informed consent was achieved. Genomic DNA was isolated. The sequence of the LMNA gene, including all exons and intron boundaries was analyzed by PCR and Sanger sequencing. Chorionic villus was collected from the placenta to reveal the condition of the fetus. Molecular analysis ascertained a homozygous mutation c.1620G>A (p.M540I) in the proband and heterozygous alteration in the family. Genomic DNA isolated from the CVS was amplified using specific primers for identified deleterious mutation and analyzed by Sanger sequencing. Two pathogenic mutations c.1620G>A and c.1698C>T were identified in the fetus. Genetic counseling as well as justified rapid and sensitive genetic testing can provide reassurance for the families to prevent the high burden of genetic disorders. We have also applied several online tools including PolyPhen2, MUpro, SIFT, PoPMuSiC, Project HOPE and Mutation Taster to predict the impact of p.Met540Ile substitution as a hotspot region within LMNA. All tools showed reduction in the stability of the protein structure. We conclude that p.M540I mutation may causes disease in the homozygous state. PMID:26602028

  3. Coral reef monitoring in the Iles Eparses, Mozambique Channel (2011-2013)

    NASA Astrophysics Data System (ADS)

    Chabanet, P.; Bigot, L.; Nicet, J.-B.; Durville, P.; Massé, L.; Mulochau, T.; Russo, C.; Tessier, E.; Obura, D.

    2016-04-01

    Monitoring of coral reefs has become a major tool for understanding how they are changing, and for managing them in a context of increasing degradation of coastal ecosystems. The Global Coral Reef Monitoring Network (GCRMN) has near-global coverage, but there are few remote sites free of direct human impact that can serve as reference sites. This study provides baseline data for the French Iles Eparses in the Mozambique Channel, Western Indian Ocean (WIO), whose coral reefs are little known owing to their limited accessibility, and have been free from fishing pressure for over 20 years. Surveys of coral reef health and fish community structure were undertaken at four of the islands (Europa, Bassas da India, Juan de Nova and Glorieuses) in 2011-2013. Monitoring was conducted using standardized GCRMN methods for benthos and fish communities, at the highest taxonomic level. Benthic cover showed a latitudinal gradient, with higher coral cover and conversely lower algae cover (60% and 14% respectively) in the south of the Mozambique Channel. This could be due to the geomorphology of the islands, the latitudinal temperature gradient, and/or the history of chronic stress and bleaching events during the last decades. Fish also showed a latitudinal gradient with higher diversity in the north, in a center of diversity for the western Indian Ocean already recognized for corals. An exceptional biomass fish was recorded (approximately 3500 kg/ha excluding sharks, compared to a maximum of 1400 kg/ha elsewhere in the WIO). The presence of large predators and sharks in all the islands as well as the absence of fleshy benthic algae were indicators of the good health of the reef systems. Nevertheless, these islands are beginning to experience illegal fishing, particularly in the north of the Mozambique Channel, demonstrating their vulnerability to exploitation and the need to protect them as reference sites for coral reef studies, including of climate change impacts, for the region

  4. Early experience with laparoscopic surgery in children in Ile-Ife, Nigeria

    PubMed Central

    Talabi, Ademola Olusegun; Adisa, Adewale Oluseye; Adefehinti, Olufemi; Sowande, Oludayo Adedapo; Etonyeaku, Amarachukwu Chiduziem; Adejuyigbe, Olusanya

    2015-01-01

    Background: Laparoscopy is not yet routinely employed in many Paediatric Surgical Units in Nigeria despite the advantages it offers. This study describes the preliminary experience with laparoscopic procedures in a single centre. Patients and Methods: A retrospective analysis of all children who had laparoscopic surgery between January 2009 and December 2013 at the Paediatric Surgical Unit of Obafemi Awolowo University Teaching Hospitals Complex Ile-Ife was carried out. Their sociodemographic, preoperative and intraoperative data along with postoperative records were subjected to descriptive analysis. Results: Eleven (44%) diagnostic and 14 (56%) therapeutic procedures were performed on 25 children whose age ranged from 5 months to 15 years (Median: 84 months, Mean: 103 ± 64.1 months), including eight (32%) females and 17 (68%) males. Indications included acute appendicitis in 12 (48%), intra-abdominal masses in six (24%), three (12%) disorders of sexual differentiation, two (8%) ventriculoperitoneal shunt malfunctions and impalpable undescended testes in two (8%) children. The procedures lasted 15-90 minutes (Mean = 54 (±21.6) minutes). Conversion rate was 17% for two patients who had ruptured retrocaecal appendices. No intra operative complications were recorded while three (12%) patients had superficial port site infections post-operatively. All diagnostic (11) and two therapeutic procedures were done as day case surgery. The mean duration of hospital stay was 3.1 (±3.3) days for those who had appendectomies. Conclusion: Laparoscopic surgery in children is safe and feasible in our hospital. We advocate increased use of laparoscopy in paediatric surgical practice in Nigeria and similar developing settings. PMID:25659546

  5. Pre-Cenozoic metamorphism and deformation of Lesser Himalayan rocks in central Nepal

    NASA Astrophysics Data System (ADS)

    Martin, A. J.; Copeland, P.

    2009-12-01

    Many previous studies have found pre-Cenozoic Lesser Himalayan muscovite 40Ar/39Ar dates, often accompanied by poorly-defined age plateaus produced during step heating. In the Annapurna Range of central Nepal, we find that muscovite from two of seven studied Lesser Himalayan rocks yields pre-Cenozoic dates. Muscovite from a Lesser Himalayan sample from the Marsyangdi river valley has a poorly defined plateau at c. 90 Ma and a total gas age of c. 97 Ma and muscovite from a Lesser Himalayan sample from the Modi Khola valley also has a poorly defined plateau, in this sample at c. 95 Ma, and a total gas age of c. 241 Ma. There are at least two possible interpretations of the tectonic significance of these dates. One option is that cooling or muscovite growth below the closure temperature occurred at c. 95 Ma (or perhaps at c. 240 Ma). Problems with this explanation include the very wide range of pre-Cenozoic dates found in different samples from multiple studies and the absence of other evidence for mid-Cretaceous tectonism and metamorphism. Our preferred interpretation is that our pre-Cenozoic dates and corresponding poor plateaus from step-heating result from muscovite growth and cooling at some time prior to 95 Ma followed by partial Ar loss during Cenozoic Himalayan metamorphism to a peak temperature below the closure temperature for Ar in muscovite of about 350 °C. The Lesser Himalayan sample from the Modi Khola valley bears garnet and reached peak metamorphic conditions of 9±2 kbar at 560±70 °C. Because the peak temperature during Cenozoic metamorphism did not exceed about 350 °C, garnet growth and metamorphism to the peak recorded conditions must have occurred prior to the Cenozoic Himalayan orogeny. Spiraling Y and Cr zoning in these garnets and deflected external foliation rule out pre- and post-tectonic garnet growth, respectively, revealing that deformation and foliation formation accompanied the pre-Cenozoic metamorphism of these Lesser Himalayan rocks

  6. Magmatism and metamorphism linked to the accretion of continental blocks south of the Hindu Kush, Afghanistan

    NASA Astrophysics Data System (ADS)

    Faryad, Shah Wali; Collett, Stephen; Petterson, Mike; Sergeev, Sergey A.

    2013-08-01

    Metamorphic basement rocks in the southern part of the Western Hindu Kush at contact with the Kabul and Helmand crustal blocks were investigated to elucidate pressure-temperature variation and relative time relations among different metamorphic rocks. The rocks are represented by Proterozoic amphibolite facies para-/orthogneisses and migmatites with low-grade Paleozoic volcano-sedimentary sequences. Major- and trace-element geochemistry from two orthogneiss bodies and geochronological data, including new SHRIMP analyses on zircon from one of these bodies shows that they are derived from granitic rocks that related to two different magmatic arcs of Triassic and Cretaceous ages. The Triassic granites are common in the Western Hindu Kush where they intrude basement units; the Cretaceous granitic belt crosses the Afghan Central blocks south of the Hindu Kush Mountains. Three different metamorphic events have been distinguished in the southern part of Western Hindu Kush. Based on an unconformity between basement units and Carboniferous cover sequences, the first two amphibolite and greenschist facies metamorphic events are Proterozoic and Pre-Carboniferous in age respectively. The third metamorphism was recognized in Triassic and Cretaceous granitic rocks near to contact with the Kabul Block. It is of Eocene age and reached medium pressure amphibolite facies conditions. This event is genetically linked to the collision of India and Eurasia which produced a series of trans-Afghan Central block magmatic arcs and crustal scale deformation.

  7. Hydrocarbon occurrences in igneous and metamorphic rocks: Plays of the 1990s

    SciTech Connect

    Harrelson, D.W.

    1989-09-01

    A review of available geologic literature has indicated numerous references detailing the occurrences of hydrocarbon in igneous and metamorphic rocks. Notable among these references is a paper by Chung-Hsiang P'an and a group of papers edited by Sidney Powers. Collectively, these papers conclude a biogenic source for hydrocarbons, most of which occur in (1) weathered igneous and metamorphic reservoir rocks that are higher than the source rocks (e.g., Amarillo field) or (2) igneous and metamorphic rocks that exert structural or stratigraphic control on the reservoir or source rocks (e.g., Jackson dome and the Wiggins anticline-Hancock ridge). It should be noted that a new twist on the abiogenic origin of some inert hydrocarbon gases (i.e., helium and nitrogen) proposes a degassing of igneous and metamorphic rocks from sources in the underlying mantle. Recent european super-deep tests (e.g., the Siljan Ring and the Kola SG-3 testholes) have attempted, with mixed results, to verify this theory. Drilling for these deep igneous and metamorphic prospects today is considered at or below economic basement or worse - a rank wildcat. However, these plays should become increasingly commercial in the 1990s as deeper drilling technology progresses, the current oil glut is eliminated, and more exotic deep gas prospects become accepted.

  8. Metamorphic fluid flow - a question of scale, crustal depth and bulk rock composition

    SciTech Connect

    Tracy, R.J.; Rye, D.M.

    1985-01-01

    Recent studies have indicated that certain metamorphic rocks interacted with significant volumes of aqueous fluid during their time-integrated mineral reaction history. Rather than demonstrating that pervasive fluid flow is general in metamorphic rocks, these documented cases instead suggest the likelihood of pronounced to extreme channelization of through-going in fluids in deep-seated metamorphic terranes (P>3 kbar). In rocks more shallowly buried, and therefore under low lithostatic stress, pervasive flow along grain boundaries and open microfractures probably occurred, as at Skye and the Skaergaard Complex. In higher pressure metamorphic environments, documented cases of high fluid/rock ratio make a strong case for flow channelized in veins or in impure marble aquifers where pore space and permeability were created by decarbonation reactions driven by infiltration of aqueous fluid. The source of this fluid may commonly be traced to a nearby wet granitic intrusion or quartz vein. As long as the pressurized source of aqueous fluid continued, outward flow was possible as fluid held open the intergranular pore space which was created only at the infiltration/reaction front where a reduction in solid volume accompanied reaction. Cessation or interruption of fluid flow would allow the pore space to close due to porous-rock strength being exceeded by lithostatic stress. Pervasive flow or aqueous fluid in deepseated metamorphic terranes is therefore probably limited to carbonate-bearing lithologies adjacent to sources of major volumes of fluid; otherwise, fluid flow is likely to be localized in fractures or veins.

  9. Direct evidence of ancient shock metamorphism at the site of the 1908 Tunguska event

    NASA Astrophysics Data System (ADS)

    Vannucchi, Paola; Morgan, Jason P.; Della Lunga, Damiano; Andronicos, Christopher L.; Morgan, W. Jason

    2015-01-01

    Shock metamorphism is rarely found at the surface of the Earth. The most used structures to identify shock metamorphism are "true Planar Deformation Features" (PDFs) in quartz, now accepted as diagnostic indicators of a meteorite impact. Here we present several lines of evidence for shock metamorphism and PDFs developed in quartz occurring on samples centered on a circular geological structure on Mount Stojkovic (60°54‧06″N; 101°55‧40″E), which lies within southern surface exposures of the Siberian Traps. The shock event appears to have occurred during the eruption of the surface Siberian Traps basalts that cover this region. Curiously, Mount Stojkovic lies within ∼3 km of the tree fall epicenter of the 1908 Tunguska event. Based on current estimates of the Phanerozoic impact distribution, there is at most a 1 in ∼17 000 chance that the 1908 bolide would randomly fall on the site of a previous impact structure capable of creating shocked quartz. Just as improbable would be an airbust event, incapable of creating a small crater, that could have produced shock metamorphism. Our preferred least implausible hypothesis is that the shock-metamorphism here was associated with a terrestrial event, a hyperexplosive volcanic gas eruption called 'Verneshot'.

  10. Regional fluid and metal mobility in the Dalradian metamorphic belt, Southern Grampian Highlands, Scotland

    NASA Astrophysics Data System (ADS)

    Craw, D.

    1990-10-01

    A prominent set of veins was formed during post-metamorphic deformation of the Caledonian Dalradian metamorphic belt. These veins are concentrated in dilational zones in fold hinges, but apophyses follow schistosity and fold axial surface fractures. The veins are most common in the cores of regional structures, especially the Dalradian Downbend and consist of quartz, calcite, chlorite and metallic sulphides and oxides. Metals, including gold, have been concentrated in the veins. The fluid which formed the veins was low salinity (1 5 wt% NaCl and KCl) CO2-bearing (3 16 wt% CO2) water of metamorphic origin. The fluid varies slightly in composition within and between samples, but is essentially uniform in composition over several hundred km2. Vein formation occurred at about 350±50 °C and 200 300 MPa pressure. Further quartz mineralization occurred in some dilational zones at lower temperatures (160 180 °C). This later mineralization was accompanied by CO2 immiscibility. Dilution and oxidation of the metamorphic fluid occurred due to mixing with meteoric water as the rocks passed through the brittle-ductile transition. A similar metamorphic fluid is thought to have been responsible for gold mineralization in the nearby Tyndrum Fault at a later stage in the Dalradian uplift.

  11. Fluid generation in the Boucheville Basin as a consequence of the North Pyrenean metamorphism

    NASA Astrophysics Data System (ADS)

    Boulvais, Philippe

    2016-03-01

    Metamorphic fluids transport heat and matter. In the Boucheville Basin (North Pyrenean Zone), the circulation of metamorphic fluids is attested by abundant synmetamorphic quartz - calcite veins. The Boucheville Basin formed during the Albian extensional regime and was filled by the so-called "Albian flysch". The basin underwent a thermal overprint (the North Pyrenean Metamorphism) related to the exhumation of nearby mantle rocks that advected large amounts of heat to the upper crustal levels. The oxygen and carbon isotope compositions of quartz - calcite veins and their host rocks show strong buffering of the composition of the fluids by the Albian metamorphic host rocks. Some host rocks are depleted in calcite near vein contacts showing that some of the elements implicated in crystal growth in veins were derived from the local host rock. The Albian rocks display a range of oxygen and carbon isotope compositions potentially related to closed-system processes of decarbonation-dehydration. We argue then that the fluids that circulated throughout the Boucheville Basin were generated within the basin itself. Their upward migration led to heat advection in the metamorphic pile, a consequence of which was some homogenization of the recrystallization temperatures in the basin.

  12. Evidence for multiple metamorphic events in the Adirondack Mountains, N. Y

    SciTech Connect

    McLelland, J.; Lochhead, A.; Vyhnal, C.

    1988-05-01

    Field evidence consisting of: (1) rotated, foliated xenoliths, (2) country rock foliation truncated by isoclinally folded igneous intrusions bearing granulite facies assemblages document one, or more, early dynamothermal event(s) of regional scale and high grade. Early metamorphism resulted in pronounced linear and planar fabric throughout the Adirondacks and preceded the emplacement of the anorthosite-mangerite-charnockite-granite-alaskite (AMCA) suite which contains xenoliths of the metamorphosed rocks. Olivine metagabbros, believed to be approximately contemporaneous with the AMCA-suite, also crosscut and contain xenoliths of, strongly foliated metasediments. These intrusive rocks caused contact metamorphism in the metasediments which locally exhibit both anatectite and restite assemblages. Subsequently, this already complex framework underwent three phases of folding, including an early recumbent isoclinical event, and was metamorphosed to granulite facies P,T conditions. The age of the early metamorphism cannot yet be narrowly constrained, but isotopic results suggest that it may be as young as approx. 1200 Ma or older than approx. 1420 Ma. U-Pb zircon ages indicate emplacement of the AMCA-(metagabbro)-suite in the interval 1160-1130 Ma and place the peak of granulite facies metamorphism between 1070-1025 Ma. The anorogenic character of the AMCA-suite, and the occurrence of metadiabase dike swarms within it, are further evidence of the separate nature of the metamorphic events that precede and postdate AMCA emplacement.

  13. MBE-grown metamorphic lasers for applications at telecom wavelengths

    NASA Astrophysics Data System (ADS)

    Ledentsov, N. N.; Shchukin, V. A.; Kettler, T.; Posilovic, K.; Bimberg, D.; Karachinsky, L. Ya.; Gladyshev, A. Yu.; Maximov, M. V.; Novikov, I. I.; Shernyakov, Yu. M.; Zhukov, A. E.; Ustinov, V. M.; Kovsh, A. R.

    2007-04-01

    We have studied growth phenomena and structural and optical properties of metamorphic (MM) quantum dots (QDs) and QD lasers emitting in the 1.4-1.5 μm range. InAs/InGaAs QDs were grown on top of (In,Ga)As buffer layers deposited on GaAs (1 0 0) substrates. The wavelength of the QDs could be adjusted in the 1400-1600 nm spectral range by changing the composition of the (In,Ga)As matrix layer and by the amount of InAs deposited to form QDs. An additional wavelength shift can be achieved by strained-layer (In,Ga,Al)As overgrowth of the QDs. It is found that high-performance degradation-robust operation of the devices can be achieved through minimization of the defect density in the matrix material and within the QD sheets. A defect-reduction technique involving steps of strain-sensitive overgrowth and selective evaporation of the material in the defect-related areas was applied, leading to both elimination of dislocated clusters and blocking of propagating defects. MM QD lasers exhibited emission wavelength in the 1.4-1.5 μm range with a differential quantum efficiency of about ˜50% and pulsed power up to 7 W, limited by catastrophic optical mirror damage. The narrow-stripe lasers operate in a single transverse mode withstanding continuous wave current densities above 20 kA cm -2 without irreversible degradation. A maximum single mode continuous-wave output power of 220 mW limited by thermal roll-over is obtained. No beam filamentation was observed up to the highest pumping levels. Single-mode devices with as-cleaved facets are tested for 60 °C (800 h) and 70 °C (200 h) junction temperature. No noticeable degradation has been observed at 50 mW cw single mode output power, clearly manifesting for the first time degradation-free laser diodes on foreign substrates. The technology opens a way for integration of various III-V materials with silicon or germanium substrates for the next generation of microprocessors, optical interconnects and cascaded solar cells.

  14. Grain-Recycling Zoning of Plagioclase and Metamorphic Fractionation

    NASA Astrophysics Data System (ADS)

    Pearce, M. A.; Wheeler, J.

    2008-12-01

    Quartzo-feldspathic gneisses make up much of the continental crust often having enjoyed a complex thermal history. Determining peak metamorphic conditions using conventional equilibrium thermodynamics is difficult because there are too many degrees of freedom. Zoned minerals are problematic, because of uncertainties in the exact equilibrium assemblage at any particular time, but provide a time-dependent measure of changes in equilibrium conditions. Zoning can arise due to diffusion of atoms into a homogeneous lattice from grain boundarys or through mineral growth under changing pressure, temperature or bulk rock composition. Conventional growth zoning considers a porphyroblast (commonly garnet) growing in an effectively homogeneous matrix with the growth rate controlled by reactions that produce new porphyroblast material. However, simulations of zoning developed by grain growth in a monophase domains of more complex rocks show boundary migration rates control the zoning geometry as shrinking grains are cannibalised by growing grains. This new grain-recycling zoning develops because chemical reactions change the composition of the material that is swept by the grain boundary without changing the mineral. A model of this process has been created using the Gibbs free energy minimisation software Theriak-Domino controlled by our custom written Matlab control program. This program assumes an initially homogeneous composition of equigranular plagioclase then uses the experimentally determined normal growth law for plagioclase to calculate the grain-size increase for a given time-step thus giving the amount of material swept. Assuming this is all available for reaction at the same time, the rest of the plagioclase is removed from the bulk composition, the equilibrium plagioclase composition calculated, and added to the growing grain. This fractionation alters the range of plagioclase compositions available over a given temperature range, changing PT estimates obtained

  15. Controls on Calcite Solubility in Metamorphic and Magmatic Fluids

    NASA Astrophysics Data System (ADS)

    Manning, C. E.; Eguchi, J.; Galvez, M.

    2015-12-01

    Calcite is an important hydrothermal alteration product in a wide range of environments. The role of calcite in hydrothermal alteration depends on its solubility in geologic fluids, especially H2O. At ambient T and P, calcite solubility is low and it exhibits well-known declining, or "reverse", solubility with rising T. However, experimental and theoretical studies show that increasing P yields higher solubility and restricts the region of reverse solubility behavior to higher temperature. At 0.2 GPa the reverse solubility region lies at T>600°C; at 0.5 GPa, >800°C. Thus, whereas calcite possesses relatively low solubility in pure H2O in shallow hydrothermal systems (typically <10 ppm C), it is substantially more soluble at conditions of middle and lower crustal metamorphism and magmatism, reaching concentrations ≥1000 ppm. At the higher P of subduction zones, aragonite solubility in H2O is even greater. Thus, neglecting other solubility controls, calcite precipitation is favored as crustal fluids cool and/or decompress. However, the solubility of calcite in H2O also depends strongly on other solutes, pH, and fO2. Sources of alkalinity decrease calcite solubility. In contrast, sources of acidity such as CO2 and Cl increase solubility. Crustal fluids can be enriched in alkali halides such as NaCl. Calcite solubility increases with increasing salt content at a given P and T. From approximately seawater salinity to salt saturation, the fluid behaves as a dilute molten salt and calcite solubility increases as the square of the salt mole fraction regardless of the alkali (Li, Na, K, Cs) or halogen (F, Cl, Br, I) considered. Similar behavior is seen in mixed salt solutions. At lower salinities, solubility behavior is as expected in dilute electrolyte solutions. The transition from dilute electrolyte to molten salt is fundamental to the properties of crustal fluids. Reduction of carbonate species or CO2 in the fluid to CH4, which is common during serpentinization of

  16. Chemical and physical studies of type 3 chondrites. VIII - Thermoluminescence and metamorphism in the CO chondrites

    NASA Technical Reports Server (NTRS)

    Keck, Bradly D.; Sears, Derek W. G.

    1987-01-01

    A possible relationship between the thermoluminescence (TL) properties of CO chondrites and their metamorphic history was investigated by measuring the TL properties of seven normal CO chondrites and of the Colony and the Allan Hills A77307 (ALHA 77307) CO-related chondrites. With the exception of Colony and ALHA 77307, whose maximum induced TL emission is at approximately 350 C, the CO chondrites were found to exhibit two TL peaks: a 130 C and a 250 C peaks. Among the CO chondrites, the 130 C peak showed a 100-fold range in TL sensitivity and was found to correlate with various metamorphism-related phenomena, such as silicate heterogeneity, metal composition, and McSween's metamorphic subtypes. The peak at 250 did not show these correlations and, with exception of Colony, showed little variation.

  17. Planet Alsioff - A problem set for students of phase equilibria or metamorphic petrology

    NASA Technical Reports Server (NTRS)

    Burt, Donald M.

    1988-01-01

    This paper presents a problem set that contains questions for students of phase equilibria or metamorphic petrology concerning a hypothetical planet Alsioff, for which incomplete data are given. On this panet, the SiF4 is the major volatile and Al, Si, O, and F are the only elements present. Progressive metamorphism on Alsioff mainly involves devolatilization of fluid SiF4. The problem set includes ten questions. Some of these are concerned with possible chemical reactions that should affect water, wollastonite, or Ca-SiO3 exposed to the atmosphere of Alsioff; the mechanism of controls of the O2 and F2 contents of the Alsioffian atmosphere; and the devolatilization reactions involving SiF4 with progressive thermal metamorphism.

  18. Shock metamorphic effects in the Luna 16 soil sample from Mare Fecunditatis.

    NASA Technical Reports Server (NTRS)

    French, B. M.

    1972-01-01

    Diverse lunar soil fragments returned from the Luna 16 mission were examined for evidence in shock metamorphism in order to evaluate the role of meteorite impact in forming the lunar regolith at a new site relatively distant from the Apollo landing sites. It was found that shock metamorphic effects, characteristic of meteorite impact and virtually identical to those observed in Apollo samples, are common in the Luna 16 fragments. Two types of shock effects are present - i.e., a deformation and partial melting features in rock and mineral fragments, and heterogeneous glasses and glassy breccias produced by shock melting. It is concluded that these shock metamorphic effects indicate that regolith formation by meteorite impact has occurred in Mare Fecunditatis and is a general process over the entire moon.

  19. Single or Multiphase Metamorphic History of the Nordfjord Ultrahigh-Pressure Province, Western Norway?

    NASA Astrophysics Data System (ADS)

    Young, D. J.; Kylander-Clark, A. R.; Gehrels, G. E.; Hacker, B. R.

    2010-12-01

    Deciphering the metamorphic evolution of exposed ancient high/ultrahigh-pressure terranes yields important insights into the tectonic processes hidden beneath active continental collision belts. In particular, continuing controversy exists over the age and tectonic significance of multiple, broadly syn-orogenic, eclogite-, granulite- and amphibolite-facies metamorphic episodes that have been identified by numerous workers in both ancient and modern orogens. Do these episodes represent discrete tectonic events, changing boundary conditions, or simply asynchronous equilibrium within a continuous kinematic framework? The Nordfjord area of western Norway was subducted to depths >100 km during the Devonian Scandian orogeny, and exhumed rapidly thereafter. Peak metamorphic grade increases steadily from high-P amphibolite facies south of Nordfjord, to coesite-eclogite facies north and westward. This transition is not disrupted by any significant structural or metamorphic breaks, and thus likely results from in-situ prograde metamorphism. Yet two ages of eclogite-facies metamorphism are known from this region: in southern parts of the transition, TIMS U/Pb dating of multigrain zircon fractions from a fine-grained mafic eclogite (2.3 GPa, 600°C) yield a discord with a lower intercept of 414±4 Ma (MSWD=1.1). Farther north within the UHP zone, however, TIMS dating of two zircon grains from a coarser-grained, higher temperature (˜700°C) eclogite return a concordant weighted mean age of 405±2 Ma (MSWD=0.96). Determining the relative age(s) of metamorphic episodes in the Nordfjord region has relied on dating scattered, rare mafic eclogite. Yet the volumetrically dominant granodioritic and granitic gneiss country rocks, which mostly retain amphibolite-facies assemblages, may offer a more continuous database to elucidate the significance of spatial variations in metamorphic age. Populations of small zircons (<50-80 microns) from seven samples of felsic gneiss were analyzed

  20. Origins and movement of fluids during deformation and metamorphism in the canadian cordillera.

    PubMed

    Nesbitt, B E; Muehlenbachs, K

    1989-08-18

    Stable isotope data from quartz veins in the Canadian Cordillera indicate that crustal fluids were heterogeneous in terms of sources and flow paths during Mesozoic-Cenozoic metamorphism and deformation. In regions of strike-slip and extensional faulting, the fluid regime to depths of at least 15 kilometers was dominated by convected, chemically evolved meteoric water. In contrast, in thrust faulted regions, the fluid regime was dominated by fluids derived from metamorphic devolatilization reactions. Deep convection of meteoric water implies that fluid pressures are hydrostatic in such systems not lithostatic, as had been commonly assumed. The occurrence of significantly lower fluid pressures would necessitate reevaluation of the manner in which metamorphic phase equilibria and stress relations in the crust are modeled. In addition, this study indicates that mesothermal gold deposits in the Canadian Cordillera are a product of the meteoric water convection process. PMID:17791712

  1. Blueschist metamorphism in the Yreka-Fort Jones area, Klamath Mountains, California

    USGS Publications Warehouse

    Hotz, Preston E.

    1973-01-01

    Blueschist is plentiful in the Yreka-Fort Jones area, eastern Klamath Mountains, adjacent to a belt of serpentinite that marks the boundary between two fundamental lithologic units, an eastern belt of early Paleozoic sedimentary and metamorphic rocks, and a western greenstone-chert assemblage of late Paleozoic and Triassic(?) age. The blueschists, which contain lawsonite and glaucophane or crossite, occur with phyllitic quartzite and siliceous phyllite of the Stuart Fork Formation, which is overthrust northwestward on the greenstone-chert terrane. The blueschist facies metamorphism probably was synchronous with Middle and Late Jurassic metamorphism of the Stuart Fork Formation. The blueschist-serpentinite terrane possibly marks the site of collision between the eastern Klamath plate and an oceanic western Paleozoic and Triassic plate.

  2. Permeability of the continental crust: Implications of geothermal data and metamorphic systems

    USGS Publications Warehouse

    Manning, C.E.; Ingebritsen, S.E.

    1999-01-01

    In the upper crust, where hydraulic gradients are typically 10 MPa km-1, the mean permeabilities required to accommodate the estimated metamorphic fluid fluxes decrease from ~10-16 m2 to ~10-18 m2 between 5- and 12-km depth. Below ~12 km, which broadly corresponds to the brittle-plastic transition, mean k is effectively independent of depth at ~10(-18.5??1) m2. Consideration of the permeability values inferred from thermal modeling and metamorphic fluxes suggests a quasi-exponential decay of permeability with depth of log k ~ -3.2 log z - 14, where k is in meters squared and z is in kilometers. At mid to lower crustal depths this curve lies just below the threshold value for significant advection of heat. Such conditions may represent an optimum for metamorphism, allowing the maximum transport of fluid and solute mass that is possible without advective cooling.

  3. Trace element mobilisation in garnet-phengite HP veins along a metabasite-micaschist contact: an example from the Ile de Groix, France

    NASA Astrophysics Data System (ADS)

    El Korh, A.; Schmidt, S. Th.; Vennemann, T.; Ulianov, A.

    2012-04-01

    Whole rock trace element and isotopic compositions of different HP-LT metamorphic rocks of the Ile de Groix, a late Palaeozoic HP terrane, characterize the geochemical processes during subduction and exhumation. Open system fluid-rock interactions during the early stages of subduction (hydrothermal alteration, metasomatism related to sediment-derived fluids) resulted in an increase of δ18O values, as well as K2O, Na2O, MgO, and large ion lithophile element (LILE) content, and a decrease of CaO content of metabasites. During the HP-LT event, fluid-rock interactions were of a closed system nature and most metabasites retained their early-subduction trace element and isotopic compositionsup to lower eclogite-facies P-T conditions. However, rare eclogitic veins are multi-stage veins with a cumulate fluid flow at HP conditions (El Korh et al., 2011). They are phe-grt-ep-rt-ilm-qtz-ab-pg-ap bearing, dominated by garnet and phengite and are hosted in metasomatised eclogite facies metabasites with a grt-agr/jd-barr-gln-rt-ep-qtz-ab-chl-ilm-mt assemblage (peak conditions: ~ 2.0 GPa; 450-550°C) in contact with metapelites. The HREE and HFSE enrichments in garnet and rutile, as well as the LREE enrichment in epidote of the veins, result from a mass transfer from the host metabasite involving an internally-derived fluid during the first stage of vein formation. The fluid was able to mobilise the REE and HFSE on a small scale, but precipitation thereof within the vein minerals. During the second stage of vein formation, the fluid responsible for the formation of phengite, chloritoid, ilmenite and garnet rims contained LILE and REE. Addition of an external fluid is necessary to explain the LILE enrichment. The phengite content in the vein (20-25%) is too high to originate from the host metabasites (only 3-5% phengite), suggesting an input of a pelite-derived fluid from the neighbouring micaschists in addition to the metabasite-derived fluid. The fluid δ18O values of 10

  4. Giants, Dwarfs and the Environment – Metamorphic Trait Plasticity in the Common Frog

    PubMed Central

    Grözinger, Franziska; Thein, Jürgen; Feldhaar, Heike; Rödel, Mark-Oliver

    2014-01-01

    In order to understand adaptation processes and population dynamics, it is central to know how environmental parameters influence performance of organisms within populations, including their phenotypes. The impact of single or few particular parameters in concert was often assessed in laboratory and mesocosm experiments. However, under natural conditions, with many biotic and abiotic factors potentially interacting, outcomes on phenotypic changes may be different. To study the potential environmental impact on realized phenotypic plasticity within a natural population, we assessed metamorphic traits (developmental time, size and body mass) in an amphibian species, the European common frog Rana temporaria, since a) larval amphibians are known to exhibit high levels of phenotypic plasticity of these traits in response to habitat parameters and, b) the traits' features may strongly influence individuals' future performance and fitness. In 2007 we studied these metamorphic traits in 18 ponds spread over an area of 28 km2. A subset of six ponds was reinvestigated in 2009 and 2010. This study revealed locally high variances in metamorphic traits in this presumed generalist species. We detected profound differences between metamorphing froglets (up to factor ten); both between and within ponds, on a very small geographic scale. Parameters such as predation and competition as well as many other pond characteristics, generally expected to have high impact on development, could not be related to the trait differences. We observed high divergence of patterns of mass at metamorphosis between ponds, but no detectable pattern when metamorphic traits were compared between ponds and years. Our results indicate that environment alone, i.e. as experienced by tadpoles sharing the same breeding pond, can only partly explain the variability of metamorphic traits observed. This emphasizes the importance to assess variability of reaction norms on the individual level to explain within

  5. Effect of metamorphism on isolated olivine grains in CO3 chondrites

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.

    1993-01-01

    The presence of a metamorphic sequence in the CO3 chondrite group has been shown previously to result in changes in properties of chondrule silicates. However, the role of isolated olivine grains during metamorphism of these chondrites has not been addressed. Isolated olivine grains in two metamorphosed CO3 chondrites, Lance and Isna, have been investigated in this study in order to assess the compositional properties of isolated olivine grains that may be attributable to metamorphism. Compositional changes in isolated olivines with increasing petrologic subtype are very similar to changes in chondrule olivines in the same chondrites. Olivine compositions from all occurrences (chondrules, isolated grains, and matrix) converge with increasing petrologic subtype. The degree of equilibration of minor elements is qualitatively related to the diffusion rate of each element in olivine, suggesting that diffusion-controlled processes are the most important processes responsible for compositional changes within the metamorphic sequence. The data are consistent with metamorphism taking place in a closed system on the CO3 chondrite parent body. Fe-poor olivine grains in metamorphosed chondrites are characterized by an Fe-rich rim, which is the result of diffusion of Fe into the grains from Fe-rich matrix. In some instances, 'complex', Fe-rich rims have been identified, which appear to have originated as igneous overgrowths and subsequently to have been overprinted by diffusion processes during metamorphism. Processes experienced by CO3 chondrites are more similar to those experienced by the ordinary chondrites than to those encountered by other carbonaceous chondrites, such as the CV3 group.

  6. Timing of Proterozoic deformation, plutonism, and metamorphism in the Los Pinos Mountains, Central New Mexico

    SciTech Connect

    Shastri, L.L. . Dept. of Geology); Bowring, S.A. )

    1992-01-01

    Geochronologic, structural, and metamorphic studies within the Los Pinos Mountains (LPM), central NM provide new insights into the Proterozoic geologic history of this area. The LPM consist of a NE-trending, NW-dipping sequence of complexly deformed amphibolites and felsic schists. These have been intruded by a pervasively deformed granitic pluton. Two predominant deformational fabrics exist in the LPM. S1 is an early northwest-trending foliation, commonly parallel to compositional layering, which is folded about S2. S2 is axial planar foliation to tight to isoclinal folds and is the regional NE-trending fabric. Other fabrics and complex fold interference patterns may be related to localized strain partitioning around granitic bodies. A network of granitic dikes associated with the pluton crosscuts S2 but contains a weak foliation parallel to S2, suggesting synkinematic intrusion of the dikes. Regional metamorphism in the LPM took place at upper greenschist to lower amphibolite facies. Electron microprobe traverses of garnets show compositional variation indicative of growth zoning. No abrupt changes in composition representative of multiple metamorphic events are observed. Garnet-biotite geothermometry yields average rim temperatures of 454 [+-] 50 C. U-Pb geochronology of zircons from amphibolite, granite, and a granite dike indicates essentially the same age for all three units (1.66 Ga). The amphibolite contains abundant zircons which have complex morphologies typical of metamorphic growth; however, an igneous origin cannot yet be precluded. Spheres from the same amphibolite yield a near concordant age of 1.62 Ga. Thus, deformation, plutonism, and possibly the peak of metamorphism, were coeval at ca. 1.66 Ga, with metamorphism cooling through the blocking temperature of sphene at 1.62 Ga. The LPM are similar to other mountain ranges in south-central New Mexico where 1.66 Ga ages have been reported.

  7. Giants, dwarfs and the environment - metamorphic trait plasticity in the common frog.

    PubMed

    Grözinger, Franziska; Thein, Jürgen; Feldhaar, Heike; Rödel, Mark-Oliver

    2014-01-01

    In order to understand adaptation processes and population dynamics, it is central to know how environmental parameters influence performance of organisms within populations, including their phenotypes. The impact of single or few particular parameters in concert was often assessed in laboratory and mesocosm experiments. However, under natural conditions, with many biotic and abiotic factors potentially interacting, outcomes on phenotypic changes may be different. To study the potential environmental impact on realized phenotypic plasticity within a natural population, we assessed metamorphic traits (developmental time, size and body mass) in an amphibian species, the European common frog Rana temporaria, since a) larval amphibians are known to exhibit high levels of phenotypic plasticity of these traits in response to habitat parameters and, b) the traits' features may strongly influence individuals' future performance and fitness. In 2007 we studied these metamorphic traits in 18 ponds spread over an area of 28 km2. A subset of six ponds was reinvestigated in 2009 and 2010. This study revealed locally high variances in metamorphic traits in this presumed generalist species. We detected profound differences between metamorphing froglets (up to factor ten); both between and within ponds, on a very small geographic scale. Parameters such as predation and competition as well as many other pond characteristics, generally expected to have high impact on development, could not be related to the trait differences. We observed high divergence of patterns of mass at metamorphosis between ponds, but no detectable pattern when metamorphic traits were compared between ponds and years. Our results indicate that environment alone, i.e. as experienced by tadpoles sharing the same breeding pond, can only partly explain the variability of metamorphic traits observed. This emphasizes the importance to assess variability of reaction norms on the individual level to explain within

  8. Modelling of the thermal history of metamorphic zoning in the Connemara region (western Ireland)

    NASA Astrophysics Data System (ADS)

    Reverdatto, V. V.; Polyansky, O. P.

    2004-02-01

    The Connemara region of the Irish Caledonides is a classic example of regional-scale metamorphism of low pressure and high temperature. This terrane is considered as part of a fold belt comprising metasedimentary and metavolcanic rocks that are correlated with the Neoproterozoic-Lower Paleozoic Dalradian Supergroup of Scotland. In mid-Ordovician time, the extensive and high-temperature metamorphism was superimposed on the Dalradian rocks resulting in the Connemara zoning. The key feature of the zoning is elevated horizontal thermal gradient of ca. 14 °C/km. Geological data and geochronological evidence point to a causative link between metamorphism and associated magmatic intrusions, and a brief period of development for the metamorphic zoning. Magmatic intrusion into the middle part of continental crust is treated as a most plausible source of heat for metamorphism, and other conjectures as to the origin of the zoning (flow of hot fluid through the permeable rocks, fracture conduit flushed by flowing magma) are believed to be improbable. To examine in sufficient detail the problem of the nature of heat source, a series of appropriate calculations have been performed to reach the best agreement between the observed and simulated spatial distribution of maximum temperatures at different times. The mathematical modelling shows that the temperature-spatial structure of the Connemara zoning is best explained by the model version based on mid-crustal heating above the upper contact of magmatic intrusive body gently curved and tilted at an angle between 20° and 40°, with an initial temperature of the magma appropriate to a basaltic melt. The model estimate of total lifetime of the temperature anomaly in the crust is of the order of 5-6 Ma. In general, this is in rather good agreement with the currently available evidence of geochronological duration of metamorphism and magmatism in Connemara.

  9. Can the Metamorphic Basement of Northwestern Guatemala be Correlated with the Chuacús Complex?

    NASA Astrophysics Data System (ADS)

    Cacao, N.; Martens, U.

    2007-05-01

    The Chuacús complex constitutes a northward concave metamorphic belt that stretches ca. 150 km south of the Cuilco-Chixoy-Polochic (CCP) fault system in central and central-eastern Guatemala. It represents the basement of the southern edge of the Maya block, being well exposed in the sierra de Chuacús and the sierra de Las Minas. It is composed of high-Al metapelites, amphibolites, quartzofeldspathic gneisses, and migmatites. In central Guatemala the Chuacús complex contains ubiquitous epidote-amphibolite mineral associations, and local relics of eclogite reveal a previous high-pressure metamorphic event. North of the CCP, in the Sierra de Los Cuchumatanes area of western Guatemala, metamorphic rocks have been considered the equivalent of the Chuacús complex and hence been given the name Western Chuacús group, These rocks, which were intruded by granitic rocks and later mylonitized, include chloritic schist and gneiss, biotite-garnet schist, migmatites, and amphibolites. No eclogitic relics have been found within metamorphic rocks in northwestern Guatemala. Petrographic analyses of garnet-biotite schist reveal abundant retrogression and the formation of abundant zeolite-bearing veins associated with intrusion. Although metamorphic conditions in the greenschist and amphibolite facies are similar to those in the sierra de Chuacús, the association with deformed intrusive granites is unique for western Guatemala. Hence a correlation with metasediments intruded by the Rabinal granite in the San Gabriel area of Baja Verapaz seems more feasible than a correlation with the Chuacús complex. This idea is supported by reintegration of the Cenozoic left-lateral displacement along the CCP, which would place the metamorphic basement of western Guatemala north of Baja Verapaz, adjacent to metasediments intruded by granites in the San Gabriel-Rabinal area.

  10. Metamorphic sole formation, emplacement and blueschist overprint: early obduction dynamics witnessed by W. Turkey ophiolites

    NASA Astrophysics Data System (ADS)

    Plunder, Alexis; Agard, Philippe; Chopin, Christian; Soret, Mathieu; Okay, Aral; Whitechurch, Hubert

    2016-04-01

    Western Turkey, with a >200 km long-belt of unmetamorphosed ophiolite overlying continental lithosphere is one or even the largest obducted ophiolite on Earth and therefore a key example to study obduction and early subduction dynamics. All Western Turkish ophiolite fragments are considered as part of the same Neotethyan branch resulting of a long-lived continental subduction (or underthrusting). Synchronous (ca. ~ 93 Ma) metamorphic sole formation and preservation at the base of most of the Turkish ophiolite fragments support this single event and place a strong constraint on the age of subduction initiation. Metamorphic soles are indeed generally considered to have formed during the early and hot subduction zone at 25 ± 10 km depths and welded to the overriding oceanic lithosphere. In Western Turkey however (as for most places worldwide) a systematic study of the pressure-temperature conditions with modern thermobarometric tools is generally lacking, and fundamental mechanisms of formation or accretion to the upper plate are poorly (if at all) constrained. We herein reappraise Western Turkish metamorphic soles focusing on the following points and issues: (i) detailed structures of metamorphic sole and other subduction derived units, petrological evolution and refined pressure-temperature conditions; peak pressure-temperature conditions of metamorphic sole were estimated using garnet, clinopyroxene, amphibole and plagioclase as the peak paragenesis at 10.5 ± 2 kbar and 800 ± 50°C based on pseudosections using the Theriak/Domino package (ii) the rather unique (and enigmatic) blueschist facies overprint found in places was investigated in terms of structural position and pressure-temperature conditions. Conditions of overprint were estimated around 12 kbar and 425 °C from the presence of glaucophane, lawsonite, jadeite and garnet overgrowing the amphibolite-facies assemblage. This field-based study provides clues to mechanisms of metamorphic sole underplating

  11. Experimental Study on Fluid Distribution at Ultra-High Metamorphic Conditions

    NASA Astrophysics Data System (ADS)

    Mönicke, K.; Burchard, M.; Duyster, J.; Maresch, W. V.; Röller, K.; Stöckhert, B.

    2001-12-01

    Ultra-high pressure (UHP) metamorphic rocks record deep subduction of continental crust. Insight into their rheological behavior at UHP metamorphic conditions is important for the understanding of the mechanical state and the kinematics within subduction zones. Amazingly, many exhumed UHP metamorphic rocks do not show evidence of significant deformation. Thus, it has been proposed that deformation is localized in low-strength zones controlled by partially wetting interstitial fluids [1]. Experimental results [2] show that at UHP metamorphic conditions only one homogenous fluid phase with variable composition exists, whose density and viscosity should be intermediate between those of conventional aqueous solutions and hydrous melts. Inclusions of such supercritical fluid have been recently described from a natural UHP metamorphic rock [3]. Motivated by these findings, experiments using a piston-cylinder apparatus were performed to study the fluid distribution in various rock types at pressures of 3.5 GPa and temperatures between 900 ° C and 600 ° C. Starting materials were natural UHP metamorphic specimens of (1) S-type granitic biotite-phengite-gneiss and (2) pyrope-quartzite, both from the Dora Maira Massif (Western Alps, Italy) and (3) a diamond-bearing garnet-mica-gneiss with granodioritic bulk composition from the Saxonian Erzgebirge (Germany), all with 2 wt.% water added. The supercritical fluids formed in these experiments can be quenched to form a silicic glass with demixing of an aqueous solution without changing the UHP fluid topology significantly. The shape of the fluid-filled interstices is irregular and complex, resulting in a low volume/interface area ratio and a potential of high stress concentration at the edges of wedge-shaped offshoots. We propose that the distribution of supercritical fluids has a pronounced effect on the strength of cool subducted crust, allowing deformation by grain boundary sliding and dissolution precipitation creep, or

  12. Peak metamorphic temperature and thermal history of the Southern Alps (New Zealand)

    NASA Astrophysics Data System (ADS)

    Beyssac, O.; Cox, S. C.; Vry, J.; Herman, F.

    2016-04-01

    The Southern Alps orogen of New Zealand results from late Cenozoic convergence between the Indo-Australian and Pacific plates and is one of the most active mountain belts in the world. Metamorphic rocks carrying a polymetamorphic legacy, ranging from low-greenschist to high-grade amphibolites, are exhumed in the hanging wall of the Alpine Fault. On a regional scale, the metamorphic grade has previously been described in terms of metamorphic zones and mineral isograds; application of quantitative petrology being severely limited owing to unfavorable quartzofeldspathic lithologies. This study quantifies peak metamorphic temperatures (T) in a 300 × 20 km area, based on samples forming 13 transects along-strike from Haast in the south to Hokitika in the north, using thermometry based on Raman spectroscopy of carbonaceous material (RSCM). Peak metamorphic T decreases across each transect from ≥ 640 °C locally in the direct vicinity of the Alpine Fault to less than 330 °C at the drainage divide 15-20 km southeast of the fault. Thermal field gradients exhibit a degree of similarity from the southernmost to the northernmost transects, are greater in low-grade semischist than high-grade schist, are affected by folding or discontinuous juxtaposition of metamorphic zones, and contain limited information on crustal-scale geothermal gradients. Temperatures derived by RSCM thermometry are slightly (≤ 50 °C) higher than those derived by traditional quantitative petrology using garnet-biotite thermometry and THERMOCALC modeling. The age of RSCM T appears to be mostly pre-Cenozoic over most of the area except in central Southern Alps (Franz Josef-Fox area), where the amphibolite facies schists have T of likely Cenozoic age. The RSCM T data place some constraints on the mode of exhumation along the Alpine Fault and have implications for models of Southern Alps tectonics.

  13. Age and duration of eclogite-facies metamorphism, North Qaidam HP/UHP terrane, Western China

    USGS Publications Warehouse

    Mattinson, C.G.; Wooden, J.L.; Liou, J.G.; Bird, D.K.; Wu, C.L.

    2006-01-01

    Amphibolite-facies para-and orthogneisses near Dulan, at the southeast end of the North Qaidam terrane, enclose minor eclogite and peridotite which record ultra-high pressure (UHP) metamorphism associated with the Early Paleozoic continental collision of the Qilian and Qaidam microplates. Field relations and coesite inclusions in zircons from paragneiss suggest that felsic, mafic, and ultramafic rocks all experienced UHP metamorphism and a common amphibolite-facies retrogression. SHRIMP-RG U-Pb and REE analyses of zircons from four eclogites yield weighted mean ages of 449 to 422 Ma, and REE patterns (flat HREE, no Eu anomaly) and inclusions of garnet, omphacite, and rutile indicate these ages record eclogite-facies metamorphism. The coherent field relations of these samples, and the similar range of individual ages in each sample suggests that the ???25 m.y. age range reflects the duration of eclogite-facies conditions in the studied samples. Analyses from zircon cores in one sample yield scattered 433 to 474 Ma ages, reflecting partial overlap on rims, and constrain the minimum age of eclogite protolith crystallization. Inclusions of Th + REE-rich epidote, and zircon REE patterns are consistent with prograde metamorphic growth. In the Lu??liang Shan, approximately 350 km northwest in the North Qaidam terrane, ages interpreted to record eclogite-facies metamorphism of eclogite and garnet peridotite are as old as 495 Ma and as young as 414 Ma, which suggests that processes responsible for extended high-pressure residence are not restricted to the Dulan region. Evidence of prolonged eclogite-facies metamorphism in HP/UHP localities in the Northeast Greenland eclogite province, the Western Gneiss Region of Norway, and the western Alps suggests that long eclogite-facies residence may be globally significant in continental subduction/collision zones.

  14. Composition of the metal phases in ordinary chondrites - Implications regarding classification and metamorphism

    NASA Astrophysics Data System (ADS)

    Afiattalab, F.; Wasson, J. T.

    1980-03-01

    The paper examines the composition of metal phases and metamorphism in ordinary chondrites. It is shown that below 550 C increasing Co decreases the equilibrium kamacite Ni concentration of an alpha to gamma system, and that the equilibrated L chondrites have kamacite and taenite Co concentrations in the L-group range. Metal-phase studies of petrologic type-3 ordinary chondrites with highly unequilibrated silicates showed a wide range in the degree of matrix kamacite equilibration; in the three most unequilibrated chondrites most taenite is clear, and the high Ni content shows that metamorphic temperatures were lower than 400 C in these meteorites.

  15. Fluid heterogeneity during granulite facies metamorphism in the Adirondacks: stable isotope evidence

    USGS Publications Warehouse

    Valley, J.W.; O'Neil, J.R.

    1984-01-01

    The preservation of premetamorphic, whole-rock oxygen isotope ratios in Adirondack metasediments shows that neither these rocks nor adjacent anorthosites and gneisses have been penetrated by large amounts of externally derived, hot CO2-H2O fluids during granulite facies metamorphism. This conclusion is supported by calculations of the effect of fluid volatilization and exchange and is also independently supported by petrologic and phase equilibria considerations. The data suggest that these rocks were not an open system during metamorphism; that fluid/rock ratios were in many instances between 0.0 and 0.1; that externally derived fluids, as well as fluids derived by metamorphic volatilization, rose along localized channels and were not pervasive; and thus that no single generalization can be applied to metamorphic fluid conditions in the Adirondacks. Analyses of 3 to 4 coexisting minerals from Adirondack marbles show that isotopic equilibrium was attained at the peak of granulite and upper amphibolite facies metamorphism. Thus the isotopic compositions of metamorphic fluids can be inferred from analyses of carbonates and fluid budgets can be constructed. Carbonates from the granulite facies are on average, isotopically similar to those from lower grade or unmetamorphosed limestones of the same age showing that no large isotopic shifts accompanied high grade metamorphism. Equilibrium calculations indicate that small decreases in ??18O, averaging 1 permil, result from volatilization reactions for Adirondack rock compositions. Additional small differences between amphibolite and granulite facies marbles are due to systematic lithologie differences. The range of Adirondack carbonate ??18O values (12.3 to 27.2) can be explained by the highly variable isotopic compositions of unmetamorphosed limestones in conjunction with minor 18O and 13C depletions caused by metamorphic volatilization suggesting that many (and possibly most) marbles have closely preserved their

  16. Timing and duration of garnet granulite metamorphism in magmatic arc crust, Fiordland, New Zealand

    USGS Publications Warehouse

    Stowell, H.; Tulloch, A.; Zuluaga, C.; Koenig, A.

    2010-01-01

    Pembroke Granulite from Fiordland, New Zealand provides a window into the mid- to lower crust of magmatic arcs. Garnet Sm-Nd and zircon U-Pb ages constrain the timing and duration of high-P partial melting that produced trondhjemitic high Sr/Y magma. Trace element zoning in large, euhedral garnet is compatible with little post growth modification and supports the interpretation that garnet Sm-Nd ages of 126.1??2.0 and 122.6??2.0. Ma date crystal growth. Integration of the garnet ages with U-Pb zircon ages elucidates a history of intrusion(?) and a protracted period of high-temperature metamorphism and partial melting. The oldest zircon ages of 163 to 150. Ma reflect inheritance or intrusion and a cluster of zircon ages ca. 134. Ma date orthopyroxene-bearing mineral assemblages that may be magmatic or metamorphic in origin. Zircon and garnet ages from unmelted gneiss and garnet reaction zones record garnet granulite facies metamorphism at 128 to 126. Ma. Peritectic garnet and additional zircon ages from trondhjemite veins and garnet reaction zones indicate that garnet growth and partial melting lasted until ca. 123. Ma. Two single fraction garnet ages and young zircon ages suggest continued high-temperature re-equilibration until ca. 95. Ma. Phase diagram sections constrain orthopyroxene assemblages to <0.6 GPa @ 650??C, peak garnet granulite facies metamorphic conditions to 680-815??C @ 1.1-1.4. GPa, and a P-T path with a P increase of???0.5. GPa. These sections are compatible with water contents???0.28wt.%, local dehydration during garnet granulite metamorphism, and <0.3. GPa P increases during garnet growth. Results demonstrate the utility of integrated U-Pb zircon and Sm-Nd garnet ages, and phase diagram sections for understanding the nature, duration, and conditions of deep crustal metamorphism and melting. Geochronologic and thermobarometric data for garnet granulite indicate that thickening of arc crust, which caused high-pressure metamorphism in northern

  17. Composition of the metal phases in ordinary chondrites - Implications regarding classification and metamorphism

    NASA Technical Reports Server (NTRS)

    Afiattalab, F.; Wasson, J. T.

    1980-01-01

    The paper examines the composition of metal phases and metamorphism in ordinary chondrites. It is shown that below 550 C increasing Co decreases the equilibrium kamacite Ni concentration of an alpha to gamma system, and that the equilibrated L chondrites have kamacite and taenite Co concentrations in the L-group range. Metal-phase studies of petrologic type-3 ordinary chondrites with highly unequilibrated silicates showed a wide range in the degree of matrix kamacite equilibration; in the three most unequilibrated chondrites most taenite is clear, and the high Ni content shows that metamorphic temperatures were lower than 400 C in these meteorites.

  18. Impact-shocked zircons: Discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

    NASA Technical Reports Server (NTRS)

    Bohor, B. F.; Betterton, W. J.; Krogh, T. E.

    1993-01-01

    Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows scanning electron microscope (SEM) visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the U-Pb isotopic system.

  19. Field measurement of slow metamorphic reaction rates at temperatures of 500 degrees to 600 degrees C

    PubMed

    Baxter; DePaolo

    2000-05-26

    High-temperature metamorphic reaction rates were measured using strontium isotopic ratios of garnet and whole rock from a field site near Simplon Pass, Switzerland. For metamorphic conditions of cooling from 612 degrees +/- 17 degrees C to 505 degrees +/- 15 degrees C at pressures up to 9.1 kilobars, the inferred bulk fluid-rock exchange rate is 1.3(-0.4)(+1.1) x 10(-7) grams of solid reacted per gram of solid per year, several orders of magnitude lower than laboratory-based estimates. The inferred reaction rate suggests that mineral chemistry may lag the evolving conditions in Earth's crust during mountain building. PMID:10827949

  20. Impact-shocked zircons: discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

    USGS Publications Warehouse

    Bohor, B.F.; Betterton, W.J.; Krogh, T.E.

    1993-01-01

    Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows SEM visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the UPb isotopic system. ?? 1993.

  1. Differentiating Detrital and Metamorphic Monazite in Greenschist-Facies Sandstones From the Witwatersrand Supergroup

    NASA Astrophysics Data System (ADS)

    Muhling, J. R.; Rasmussen, B.

    2009-05-01

    Monazite is a robust and reliable geochronometer of low-temperature metamorphic and hydrothermal events. It is a widespread accessory phase in sedimentary rocks metamorphosed at prehnite-pumpellyite to lower greenschist facies grade, and also in a range of hydrothermal ore deposits. Its ability to date multiple fluid-flow events in low-grade metasedimentary belts has been largely neglected, possibly because of a misconception that it is rare in these rocks and possibly because of misidentification of metamorphic monazite grains as detrital. Both detrital and metamorphic monazites are present in sandstone and conglomerate from the Witwatersrand Supergroup but can be distinguished by their occurrence, chemistry and age. Detrital grains were unstable during regional greenschist-facies metamorphism, and show evidence for a number of destructive reactions dependent on bulk rock composition and the original composition of the monazite. In quartz sandstone and conglomerate, detrital grains were present in heavy mineral bands with pyrite, zircon and chromite. The monazite grains have been pseudomorphed by intergrowths of apatite, florencite and Th-silicate, as well as matrix muscovite and chlorite. In some samples, Th-silicate forms only minute specks but in others it forms larger prismatic crystals that comprise up to 2% of some pseudomorphs. These variations may reflect differences in the original compositions of the detrital grains. In other samples detrital monazite cores, dated at 2.8-3.0 Ga, are enclosed within 2.04 Ga metamorphic rims. These composite grains formed by dissolution and reprecipitation of monazite during metamorphism. The cores and rims have distinctly different compositions, and the metamorphic rims show pronounced zoning of REE. In more calcic sandstone monazite occurs in heavy mineral bands with chromite, zircon, rutile, pyrite, apatite, Th-silicate, allanite and baddeleyite. These sandstones are notably rich in Ca-bearing minerals such as epidote

  2. Genetic significance of the trace element content in metamorphic and hydrothermal quartz: a reconnaissance study

    NASA Astrophysics Data System (ADS)

    Monecke, T.; Kempe, U.; Götze, J.

    2002-09-01

    A reconnaissance study on trace elements in metamorphic and hydrothermal quartz was carried out using quartz samples from the tin district Erzgebirge, Germany, the gold mineralization at Ka\\vsperské Hory, Czech Republic, and the gold-quartz vein deposits Muruntau and Myutenbai, Uzbekistan. A new method of sample preparation has been developed to prepare pure quartz samples by combining conventional hand-picking with microscopic and spectroscopic studies as well as acid wash/etch procedures. Preparation of monomineralic samples was followed by sample dissolution and measurement by ICP-MS. The metamorphic quartz has very low concentrations of Li (≤0.4 ppm), Al (≤30 ppm), K (≤35 ppm), Rb (≤50 ppb), Sr (≤0.3 ppm), and Y (≤15 ppb). Moreover, it is characterized by light rare earth element enriched lanthanide distribution patterns lacking Eu anomalies. The low element concentrations in metamorphic quartz are interpreted to result from recrystallization. Metamorphic quartz from alteration halos enveloping tin and gold deposits has distinctly different trace element signatures. These differences are related to the hydrothermal overprint of the pre-existing metamorphic quartz by the mineralizing fluids. Hydrothermally altered metamorphic quartz from tin deposits has elevated concentrations of Li (≥0.9 ppm), Al (≥50 ppm), K (≥45 ppm), Rb (≥250 ppb), and Y (≥40 ppb) whereas altered metamorphic quartz from gold deposits is characterized by elevated concentrations of Sr (≥0.5 ppm). The rare earth element distribution patterns of altered metamorphic quartz show variable enrichments of the heavy rare earth elements and frequently display positive Eu anomalies. Hydrothermal vein quartz from the gold deposits usually has elevated Al (≥50 ppm) and Sr (≥0.6 ppm) contents. The lanthanide distribution patterns exhibit variable enrichments of the heavy rare earth elements and commonly show positive Eu anomalies. The elevated Sr concentrations in the quartz

  3. Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

    USGS Publications Warehouse

    Rye, R.O.; Schuiling, R.D.; Rye, D.M.; Jansen, J.B.H.

    1976-01-01

    At Naxos, Greece, a migmatite dome is surrounded by schists and marbles of decreasing metamorphic grade. Sillimanite, kyanite, biotite, chlorite, and glaucophane zones are recognized at successively greater distances from the migmatite dome. Quartz-muscovite and quartz-biotite oxygen isotope and mineralogie temperatures range from 350 to 700??C. The metamorphic complex can be divided into multiple schist-rich (including migmatites) and marblerich zones. The ??18O values of silicate minerals in migmatite and schist units and quartz segregations in the schist-rich zones decrease with increase in metamorphic grades. The calculated ??18OH2O values of the metamorphic fluids in the schist-rich zones decrease from about 15??? in the lower grades to an average of about 8.5??? in the migmatite. The ??D values of OH-minerals (muscovite, biotite, chlorite, and glaucophane) in the schist-rich zones also decrease with increase in grade. The calculated ??DH2O values for the metamorphic fluid decrease from -5??? in the glaucophane zone to an average of about -70??? in the migmatite. The ??D values of water in fluid inclusions in quartz segregations in the higher grade rocks are consistent with this trend. The??18O values of silicate minerals and quartz segregations in marble-rich zones are usually very large and were controlled by exchange with the adjacent marbles. The ??D values of the OH minerals in some marble-rich zones may reflect the value of water contained in the rocks prior to metamorphism. Detailed data on 20 marble units show systematic variations of ??18O values which depend upon metamorphic grade. Below the 540??C isograd very steep ??18O gradients at the margins and large ??18O values in the interior of the marbles indicate that oxygen isotope exchange with the adjacent schist units was usually limited to the margins of the marbles with more exchange occurring in the stratigraphic bottom than in the top margins. Above the 540??C isograd lower ??18O values occur in

  4. Geospeedometry in the inverted metamorphic gradient of the Nestos Thrust Zone in central Rhodope (Northern Greece)

    NASA Astrophysics Data System (ADS)

    Cioldi, Stefania; Moulas, Evangelos; Burg, Jean-Pierre

    2015-04-01

    Thrust tectonics and inverted metamorphic gradients are major consequences of large and likely fast movements of crustal segments in compressional environments. The purpose of this study is to investigate the tectonic setting and the timescale of inverted metamorphic zonations related to crustal-scale thrusting. The aim is to contribute understanding the link between mechanical and thermal evolution of major thrust zones and to clarify the nature and the origin of orogenic heat. The Rhodope metamorphic complex (Northern Greece) is interpreted as a part of the Alpine-Himalaya orogenic belt and represents a collisional system with an association of both large-scale thrusting and pervasive exhumation tectonics. The Nestos Shear Zone overprints the suture boundary with a NNE-dipping pile of schists displaying inverted isograds. The inverted metamorphic zones start from chlorite-muscovite grade at the bottom and reach kyanite-sillimanite grades with migmatites in the upper structural levels. In order to reconstruct the thermo-tectonic evolution of inverted metamorphic zonation, reliable geochronological data are essential. 40Ar/39Ar geochronology with step-heating technique on white mica from micaschists provided a temporal resolution with the potential to characterize shearing. 40Ar/39Ar dating across the Nestos Shear Zone yields Late Eocene-Early Oligocene (40-30 Ma) cooling (~400-350° C) ages, which correspond to local thermo-deformation episodes linked to late and post-orogenic intrusions. U-Pb Sensitive High Resolution Ion Microprobe (SHRIMP) zircon geochronology on leucosomes from migmatitic orthogneisses were considered to estimate the age of peak metamorphic conditions, contemporaneous with anatexis. U-Pb ages of zircon rims specify regional partial melting during the Early Cretaceous (160-120 Ma). This is in disagreement with previous assertions, which argued that the formation of leucosomes in this region is Late Eocene (42-35 Ma) and implied multiple

  5. Trophic relationships between metazooplankton communities and their plankton food sources in the Iles Eparses (Western Indian Ocean).

    PubMed

    Dupuy, Christine; Pagano, Marc; Got, Patrice; Domaizon, Isabelle; Chappuis, Alexis; Marchessaux, Guillaume; Bouvy, Marc

    2016-05-01

    Coral reef and atoll lagoons are among the most diversified marine ecosystems but also the most affected by the combined effects of climate change and human activities. The Iles Eparses (Scattered Islands) in the Western Indian Ocean have been little affected by human pressure and can be considered to be "pristine" ecosystems. Metazooplankton plays a major role in the functioning and productivity of aquatic ecosystems, and this study was undertaken: (i) to determine the spatial abundance, distribution and species composition of metazooplankton, (ii) to assess the effect of metazooplankton grazing on pico- and nanophytoplankton and (iii) to analyze the trophic positions of metazooplankton by using the stable isotope signatures of a wide variety of taxa and particulate organic matter from the Iles Eparses and Mayotte. Tromelin Island (which is not located in the Mozambique Channel) had the lowest metazooplankton abundance with no cyanobacteria Trichodesmium spp. or mollusks (pteropods) presence, and with δ(15)N signatures of organisms that were higher than for the islands in the Mozambique Channel. Trichodesmium spp. was found in the Mozambique Channel and the plankton food web was probably based preferentially on these cyanobacteria with lower δ(15)N signatures indicating direct or indirect trophic transfer of diazotrophic nitrogen to metazooplankton. Three of the islands were distinct: Europa had the highest proportion of copepods, with oithonids being dominant, which is typical of rich mangrove systems, while Juan de Nova and Mayotte seemed to be the sites most affected by human activity with a high abundance of appendicularians and distinct particulate organic matter ∂(13)C signatures. Grazing experiments showed that food could be a limiting factor for metazooplankton in the Iles Eparses. However, the effect of metazooplankton grazing on phytoplankton appeared to be very low (0.01-2.32% of the total phytoplankton per day). PMID:26970685

  6. Human mitochondrial manganese superoxide dismutase polymorphic variant Ile58Thr reduces activity by destabilizing the tetrameric interface

    SciTech Connect

    Borgstahl, G.E.O.; Hickey, M.J.; Johnson, M.J.

    1996-04-09

    Human manganese superoxide dismutase (MnSOD) is a homotetrameric enzyme which protects mitochondria against oxygen-mediated free radical damage. Within each subunit, both the N-terminal helical hairpin and C-terminal {alpha}/{beta} domains contribute ligands to the catalytic manganese site. Two identical four-helix bundles,symmetrically assembled form the N-terminal helical hairpins, form a novel tetrameric interface that stabilizes the active sites. The 2.5 {angstrom} crystallographic structure of the naturally occurring polymorphic variant Ile58Thr MnSOD reveals that the helical hairpin mutation Thr58 causes two packing defects in each of the two four-helix bundles of the tetrameric interface. Similar mutations, expected to cause packing defects in the Cu,ZnSOD dimer interface, are associated with the degenerative disease amyotrophic lateral sclerosis. Ile58Thr MnSOD is primarily dimeric in solution and is significantly less thermostable than the normal enzyme, with decreases of 15{degrees}C in the main melting temperature and 20{degrees}C in the heat-inactivation temperature. Consequently, this mutant MnSOD is compromised at normal body temperatures: thermal inactivation, predicted from the decrease in thermal stability, occurs with a theoretical half-life of only 3.2h at 37{degrees}C (1.4 h at 41 {degrees}C), compared with 3.1 years for native MnSOD. This prediction is supported by direct measurements: incubation at 41.7{degrees}C for 3 h has no effect on the activity of native MnSOD but completely inactivates mutant MnSOD. Rapid inactivation of Ile58Thr MnSOD at the elevated temperatures associated with fever and inflammation could provide an early advantage by killing infected cells, but also would increase superoxide-mediated oxidative damage and perhaps contribute to late-onset diseases. 63 refs., 7 figs., 2 tabs.

  7. Elastic geobarometry for ultra high pressure metamorphic (UHPM) rocks

    NASA Astrophysics Data System (ADS)

    Mazzucchelli, Mattia Luca; Angel, Ross John; Alvaro, Matteo; Nimis, Paolo; Domeneghetti, Chiara Maria; Nestola, Fabrizio

    2015-04-01

    Conventional thermo-barometric methods can be challenged in UHPM terraines as the temperatures of deep subduction often exceed the closure temperature of geothermobarometers, and they are also afflicted by the effects of further reactions and re-equilibration on exhumation. Since minerals trapped as inclusions within other host minerals develop residual stresses on exhumation as a result of the differences between the thermo-elastic properties of the host and inclusion phases, their elastic behavior provides an alternative method independent of chemistry and chemical equilibria. The determination of possible entrapment pressures from this residual stress requires the knowledge of the equations of state (EoS) and the mutual elastic relaxation of the host and inclusion phases. So far, even the simplest elastic system of a single inclusion embedded in an isotropic host has not been properly addressed for geological systems. However, this is useful for determining the depths of formation of diamonds, and could also provide constraints on the prograde and retrograde stress-temperature paths of metamorphic assemblages. Previous analyses (i.e. Zhang, 1998) have relied on assumptions that are not physically correct (i.e. linear elasticity and invariant elastic properties of the minerals with P and T, or assume that the host material is completely rigid). We will present a solution to the single-inclusion problem that incorporates non-linear elasticity and can be applied to determine the stress distribution in the host and inclusion that arises from any change in P and T. Our solution shows that the previous calculations of residual inclusion pressures are incorrect in the relaxation term, which arises from the difference in stress at the host/inclusion interface. The general form of our solution relies on the concept of the isomeke, a line in P-T space along which the fractional volume changes of the host and inclusion are the same (Angel et al. 2014a). This allows our

  8. Metamorphic conditions and CHIME monazite ages of Late Eocene to Late Oligocene high-temperature Mogok metamorphic rocks in central Myanmar

    NASA Astrophysics Data System (ADS)

    Maw Maw Win; Enami, Masaki; Kato, Takenori

    2016-03-01

    The high temperature (T)/pressure (P) regional Mogok metamorphic belt is situated in central Myanmar, and is mainly composed of pelitic gneisses, amphibolites, marbles, and calc-silicate rocks. The garnet-biotite-plagioclase-sillimanite-quartz assemblage and its partial system suggest equilibrium P/T conditions of 0.6-1.0 GPa/780-850 °C for the peak metamorphic stage, and 0.3-0.5 GPa/600-680 °C for the exhumation and hydration stage. Monazite grains show complex compositional zoning consisting of three segments-I, II, and III. Taking into consideration the monazite zoning and relative misfit curves, the calculated chemical Th-U-total Pb isochron method (CHIME) monazite age data (284 spot analyses) indicated four age components: 49.3 ± 2.6-49.9 ± 7.9, 37.8 ± 1.0-38.1 ± 1.7, 28.0 ± 0.8-28.8 ± 1.6, and 23.7 ± 1.3 Ma (2σ level). The ages of the Late Eocene and Late Oligocene epochs were interpreted as the peak metamorphic stage of upper-amphibolite and/or granulite facies and the postdated hydration stage, respectively.

  9. Scales of mass transfer and differential mobility of major and rare-earth elements in metapelites during collisional metamorphism

    NASA Astrophysics Data System (ADS)

    Likhanov, I. I.; Reverdatto, V. V.

    2015-09-01

    Joint study of multicomponent chemical zonality of rock-forming minerals with actual metamorphic reactions in metapelite of Yenisey Range had been completed. Calculations of chemical equations, analysis of substance balance and peculiarities of changing of mineral composition during collision metamorphism of pelite attest to isochemical character of the processes in most of the system components.

  10. Metamorphic sole formation and early plate interface rheology: Insights from Griggs apparatus experiments

    NASA Astrophysics Data System (ADS)

    Soret, Mathieu; Agard, Philippe; Dubacq, Benoît; Hirth, Greg; Yamato, Philippe; Ildefonse, Benoît; Prigent, Cécile

    2016-04-01

    Metamorphic soles correspond to m to ~500 m thick highly strained metamorphic rock units found beneath mylonitic banded peridotites at the base of large-scale ophiolites, as exemplified in Oman. Metamorphic soles are mainly composed of metabasalts deriving from the downgoing oceanic lithosphere and metamorphosed up to granulite-facies conditions by heat transfer from the mantle wedge. Pressure-temperature peak conditions are usually estimated at 1.0±0.2 GPa and 800±100°C. The absence of HP-LT metamorphism overprint implies that metamorphic soles have been formed and exhumed during subduction infancy. In this view, metamorphic soles were strongly deformed during their accretion to the mantle wedge (corresponding, now, to the base of the ophiolite). Therefore, metamorphic soles and banded peridotites are direct witnesses of the dynamics of early subduction zones, in terms of thermal structure, fluid migration and rheology evolution across the nascent slab interface. Based on fieldwork and EBSD analyses, we present a detailed (micro-) structural study performed on samples coming from the Sumeini window, the better-preserved cross-section of the metamorphic sole of Oman. Large differences are found in the deformation (CPO, grain size, aspect ratio) of clinopyroxene, amphibole and plagioclase, related to mineralogical changes linked with the distance to the peridotite contact (e.g., hardening due to the appearance of garnet and clinopyroxene). To model the incipient slab interface in laboratory, we carried out 5 hydrostatic annealing and simple-shear experiments on Griggs solid-medium apparatus. Deformation experiments were conducted at axial strain rates of 10-6 s-1. Fine-grained amphibolite was synthetized by adding 1 wt.% water to a (Mid-Ocean Ridge) basalt powder as a proxy for the metamorphic sole (amphibole + plagioclase + clinopyroxene ± garnet assemblage). To synthetize garnet, 2 experiments were carried out in hydrostatic conditions and with deformation at

  11. Metamorphic and thermal evolution of large contact aureoles - lessons from the Bushveld Igneous Complex

    NASA Astrophysics Data System (ADS)

    Waters, D.

    2012-04-01

    Large igneous intrusions crystallise, cool, and transfer heat out into their host rocks. The thermal structure of the resulting aureole can be mapped as a series of assemblage zones and isograds, and can in principle be modelled on the assumption that heat transfer is dominantly by conduction. The local peak of contact metamorphism occurs later in time with increasing distance from the igneous contact. The importance of fluids as a metamorphic/metasomatic agent or heat transfer mechanism depends on volatile contents of magma and country rock, and on the geometry of the intrusion. Many of these features are spectacularly illustrated by the aureole beneath the mafic Rustenburg Layered Suite of the Bushveld Complex, which was emplaced at ca. 2060 Ma sub-concordantly into the shale-quartzite succession of the Pretoria Group in the Transvaal Basin. The layered suite reaches a thickness of at least 8 km, and the metamorphic aureole extends 4 km or more downwards into the "floor" of the intrusion. The great extent and relative absence of deformation make this a remarkable natural laboratory for studying the fundamental processes of metamorphism. In quantifying the thermal history, however, a number of second-order factors need to be taken into account. The first relates to the markedly different thermal properties of the major quartzite and shale units, and the second to the importance of endothermic metamorphic reactions in shale units relative to the quartzites. Further insights into metamorphic processes arise from the exquisite detail of poikiloblast growth microstructures preserved in graphite-poor metapelites of the Timeball Hill and Silverton Formations, 2.5 to 3.5 km beneath the igneous contact. These allow a detailed reconstruction of the time sequence of mineral growth and replacement, revealing a marked overlap of the growth intervals of porphyroblastic staurolite, cordierite, biotite, garnet and andalusite at the expense of muscovite, chlorite and chloritoid

  12. The disease-protective complement factor H allotypic variant Ile62 shows increased binding affinity for C3b and enhanced cofactor activity

    PubMed Central

    Tortajada, Agustín; Montes, Tamara; Martinez-Barricarte, Ruben; Morgan, B. Paul; Harris, Claire L.; de Córdoba, Santiago Rodríguez

    2011-01-01

    Summary Mutations and polymorphisms in the gene encoding factor H (CFH) have been associated with atypical haemolytic uraemic syndrome, dense deposit disease and age-related macular degeneration. The disease-predisposing CFH variants show a differential association with pathology that has been very useful to unravel critical events in the pathogenesis of one or other disease. In contrast, the fH-Ile62 polymorphism confers strong protection to all three diseases. Using ELISA-based methods and surface plasmon resonance analyses we show here that the protective fH-Ile62 variant binds more efficiently to C3b than fH-Val62 and competes better with factor B in proconvertase formation. Functional analyses demonstrate an increased cofactor activity for fH-Ile62 in the factor I-mediated cleavage of fluid phase and surface-bound C3b; however, the two fH variants show no differences in decay accelerating activity. From these data we conclude that the protective effect of the fH-Ile62 variant is due to its better capacity to bind C3b, inhibit proconvertase formation and catalyse inactivation of fluid-phase and surface-bound C3b. This demonstration of the functional consequences of the fH-Ile62 polymorphism provides relevant insights into the complement regulatory activities of fH that will be useful in disease prediction and future development of effective therapeutics for disorders caused by complement dysregulation. PMID:19549636

  13. The Frequent Adiponutrin (PNPLA3) Variant p.Ile148Met Is Associated with Early Liver Injury: Analysis of a German Pediatric Cohort.

    PubMed

    Krawczyk, Marcin; Liebe, Roman; Maier, Ina B; Engstler, Anna Janina; Lammert, Frank; Bergheim, Ina

    2015-01-01

    Introduction. The common adiponutrin (PNPLA3) variant p.Ile148Met is associated with liver injury. Here, we investigate the association of this polymorphism with hepatic and metabolic traits in a pediatric cohort. Patients and Methods. The study cohort comprised 142 German children (age 5-9 years, 98 overweight, 19 children with NAFLD). Results. Overweight children presented with increased serum ALT (P = 0.001) and GGT (P < 0.001) activities. ALT activities differed significantly (P = 0.02) between carriers of different PNPLA3 genotypes in the entire study cohort, in normal weight children (P = 0.02) and in children younger than 7 years (P = 0.02). Carriers of the prosteatotic PNPLA3 genotype p.148Met/Met displayed higher ALT activities as compared to children with the frequent genotype p.148Ile/Ile (P = 0.01). The BMI was however a stronger predictor of ALT activities compared to the PNPLA3 genotype (P < 0.001 and P = 0.06, resp.). The variant was associated with increased serum glucose levels (P = 0.01) and HOMA index (P = 0.02) in carriers of the p.148Ile/Met genotype but did not affect other metabolic traits or the presence of NAFLD. Discussion. The frequent PNPLA3 variant p.Ile148Met is associated with serum ALT activities already at a young age. PMID:26346943

  14. The Frequent Adiponutrin (PNPLA3) Variant p.Ile148Met Is Associated with Early Liver Injury: Analysis of a German Pediatric Cohort

    PubMed Central

    Krawczyk, Marcin; Liebe, Roman; Maier, Ina B.; Engstler, Anna Janina; Lammert, Frank; Bergheim, Ina

    2015-01-01

    Introduction. The common adiponutrin (PNPLA3) variant p.Ile148Met is associated with liver injury. Here, we investigate the association of this polymorphism with hepatic and metabolic traits in a pediatric cohort. Patients and Methods. The study cohort comprised 142 German children (age 5–9 years, 98 overweight, 19 children with NAFLD). Results. Overweight children presented with increased serum ALT (P = 0.001) and GGT (P < 0.001) activities. ALT activities differed significantly (P = 0.02) between carriers of different PNPLA3 genotypes in the entire study cohort, in normal weight children (P = 0.02) and in children younger than 7 years (P = 0.02). Carriers of the prosteatotic PNPLA3 genotype p.148Met/Met displayed higher ALT activities as compared to children with the frequent genotype p.148Ile/Ile (P = 0.01). The BMI was however a stronger predictor of ALT activities compared to the PNPLA3 genotype (P < 0.001 and P = 0.06, resp.). The variant was associated with increased serum glucose levels (P = 0.01) and HOMA index (P = 0.02) in carriers of the p.148Ile/Met genotype but did not affect other metabolic traits or the presence of NAFLD. Discussion. The frequent PNPLA3 variant p.Ile148Met is associated with serum ALT activities already at a young age. PMID:26346943

  15. New U-Pb Age and Trace Element Composition of Young Metamorphic Zircon Rims from the UHP Tso Morari Complex, NW Himalaya, Distinguishes Peak from Retrograde Metamorphism

    NASA Astrophysics Data System (ADS)

    Leech, M. L.; Coble, M. A.; Singh, S.; Guillot, S.; Jain, A. K.

    2014-12-01

    The ultrahigh-pressure (UHP) Tso Morari Complex (TMC) sits in the footwall of the Indus-Yarlung suture zone in the NW Himalaya. The timing of metamorphism during subduction and exhumation in the complex is critical to constraining the age of the India-Asia collision. de Sigoyer et al. (2000) and Leech et al. (2005) reported mean U-Pb ages for thin outer rims of sectioned zircon between 55 ± 6 Ma and 53.3 ± 0.7 Ma, respectively, for the age of peak UHP through retrograde metamorphism, and Leech et al. (2005) used these data to calculate the minimum age for the start of continental subduction at 57 ± 1 Ma. Recently published results for the TMC have reignited debate on the age of metamorphism and thus, the timing of India-Asia collision. We used the same TM38 sample analyzed for the results described in Leech et al. (2005) and performed new SIMS U-Pb depth-profiling analyses to target only the outermost ~1.5 micron rims of zircon. Our results yield a mean age of 44.9 ± 0.7 Ma; adjacent spots for REE analyses yielded positive, enriched HREE profiles with negative Eu anomalies and corresponding Ti-in-zircon temperatures of ~550° to 680° C. Sharp boundaries between zircon domains are clearly resolved with CL and BSE imaging of TM38 zircons, and there is a large age difference between rims and protolith core ages; any mixing during depth-profiling through rims is clear. The positive HREE profiles imply the period of zircon growth in the TMC at c. 45 Ma to be retrograde. We suggest that the 47-43 Ma peak ages and flat heavy REE profiles with no Eu anomaly recently reported by Donaldson et al. (2013) on sectioned zircons, and interpreted as the age of UHP metamorphism of the TMC, may actually represent mixing between zircon rims and cores. The Leech et al. (2005) collision age of 57 ± 1 Ma assumed the TMC represents the leading edge of India. However, numerical modeling of Warren et al. (2008) suggests all exhumed material is derived from the central part of the pro

  16. Metamorphic Sole and Accreted Units Along a subduction Interface: form Birth to Steady State (the Case of Western Turkey)

    NASA Astrophysics Data System (ADS)

    Plunder, A.; Agard, P.; Chopin, C.; Soret, M.

    2014-12-01

    In Western Turkey, obducted ophiolite, metamorphic sole and oceanic accretionnary complex units linked with the closure of the Neotethys are found along a 400 kilometre-long section (from north to south). We herein reappraise the metamorphic evolution of the sub-ophiolitic metamorphic units (both the metamorphic sole and the accretionnary units) of Western Turkey (i) to better characterize rock units exhumed along a cooling subduction interface, from birth to steady state (ii) to constrain the formation of metamorphic sole during the initiation of subduction (iii) and to track record of obducted ophiolite. On the basis of field and petrological observation three differents accretionnary units are reccognized with pressure-temperature estimates ranging from incipient metamorphism to blueschist-facies conditions providing information on plate coupling at different depths along the subduction interface. The upper part of the metamorphic sole was form in an amphibolite facies (garnet amphibolite - garnet clinopyroxene amphibolite). Different slices of metamorphic sole with different pressure-temperature conditions might be observed probably showing discrete timing of accretion to the upper plate. Part of the samples are characterized by a late blueschsit developpement. Both the blueschist overprint in the metamorphic sole and the high-pressure in oceanic unit were found only in the northern part of the field investigation. On the basis of the presented data, available radiometric and palaeogeographic data as well as recent themomechanical moddeling a tentative reconstruction of the subduction-zone evolution through time and the emplacement of a large-scale ophiolite is presented. Finally a comparison with ongoing work on the metamorphic sole of the Semail ophiolite of Oman is proposed with special highlights on the retrograde evolution in both settings.

  17. Metamorphic history of a high-grade blueschist exotic block from the Franciscan complex, California.

    USGS Publications Warehouse

    Moore, Diane E.

    1984-01-01

    A tectonic block (approx 6 m in diameter) in the NE Diablo Range shows evidence of three episodes of retrograde blueschist-facies metamorphism + or - deformation under progressively declining P-T conditions. Retrograde metamorphism began with the tectonic incorporation of fragments of the original metamorphic terrain into serpentinite, which provided Mg-bearing fluids for the reactions of both the first and second retrograde events. There is extensive CaCO3 veining which matches that of the associated metasediments. In the third retrograde event, aragonite crystallized, accompanied by lawsonite, chlorite, jadeitic pyroxene and crossite. Such tectonic blocks may have originally formed in a pre-Franciscan subduction zone setting; fragments of blueschist and eclogite from this metamorphic terrain were tectonically incorporated in a serpentinite diapir and developed alteration zones against the enclosing ultramafic rock. When the serpentinite reached the Earth's surface, such blocks were transferred to the Franciscan as detritus and were then re-subducted and metamorphosed along with their associated sedimentary sequences.-R.A.H.

  18. Chemical migration by contact metamorphism between granite and silt/carbonate system

    SciTech Connect

    Laul, J.C.; Papike, J.J.

    1981-01-01

    Comparison of trace element signatures between the metamorphosed and unmetamorphosed samples from granite-silt/carbonate system suggests that some elements do migrate during contact metamorphism. The relative degree of migration varies depending on the element. The evidence of chemical migration in silt and carbonate is convincing on a several-meter scale.

  19. FeO and MgO in plagioclase of lunar anorthosites: Igneous or metamorphic?

    NASA Technical Reports Server (NTRS)

    Phinney, W. C.

    1994-01-01

    The combined evidence from terrestrial anorthosites and experimental laboratory studies strongly implies that lunar anorthosites have been subjected to high-grade metamorphic events that have erased the igneous signatures of FeO and MgO in their plagioclases. Arguments to the contrary have, to this point, been more hopeful than rigorous.

  20. Field Guide to Plutonic and Metamorphic Rocks. Earth Science Curriculum Project Pamphlet Series PS-5.

    ERIC Educational Resources Information Center

    Romey, William D.

    Suggested are methods for the collection of field evidence about processes that form plutonic and metamorphic rock. Description and discussion of these types of rocks are provided. The planning and execution of a successful field trip is discussed. Advanced field projects are also discussed. Included are five appendices, references, and a…

  1. Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska

    SciTech Connect

    Miller, E.L.; Calvert, A.T.; Little, T.A. )

    1992-06-01

    Unusually closely spaced Barrovian series isograds have been described along the flanks of the Kigluaik Mountains, Seward Peninsula, Alaska, where they separate a high-grade gneiss complex intruded by granites of Cretaceous age from surrounding, regionally developed, blueschist to greenschist facies rocks. Structural mapping of the transition zone between the two metamorphic types indicates that their juxtaposition was aided by significant syn- to late-metamorphic solid-state flow that served to attenuate the overlying rock column and thus collapse the field metamorphic gradient. On the basis of field relations, structural data, petrography, and geochronologic data, strain appears to have accompanied the rapid (adiabatic) rise of high-temperature rocks from several tens of kilometers to less than 10 km depth during the Cretaceous, in an event younger than the unrelated to high-P metamorphism. Granite-cored gneiss domes on the Seward Peninsula may have formed during extension of previously thickened continental crust, resulting in the {approximately}35-km-thick crust and near-sea-level elevations of the region today.

  2. Evidence of shock metamorphism in the Mar'inka iron meteorite

    NASA Astrophysics Data System (ADS)

    Semenenko, V. P.; Tertychnaia, B. V.; Kozlov, I. S.

    Data on the structural and mineralogical features of the Mar'inka iron meteorite are presented. Results of electron-microscope studies of the deformation structure and repeated heating of the radbite grains confirm that the meteorite is a fragment of a larger body that underwent shock metamorphism when it hit the earth.

  3. Thermoluminescence constraints on the metamorphic, shock, and brecciation history of basaltic meteorites

    NASA Technical Reports Server (NTRS)

    Batchelor, J. D.; Sears, Derek W. G.

    1991-01-01

    The metamorphic, shock, and brecciation history of 18 eucrites, 13 howardites, 6 diogenites, and 15 mesosiderites is investigated via induced thermoluminescence measurements performed on them. The eucrites show a 15-fold range of TL sensitivities, which correlate with petrographic indicators of metamorphic intensity. The temperature of the dominant TL peak observed for basaltic meteorites, and experiments in which four eucrites with diverse petrographic properties were annealed at various temperatures in the laboratory, suggests that the metamorphic equilibration temperatures for most basaltic meteorites were not more than 800 C. Assuming this temperature was typical of conditions during metamorphism, then burial depths for type-above-5 eucrites were greater than 350 m and less than 50 m for type-2 eucrites. Since TL peak temperatures are related to the degree of disorder in the Al, Si chain in feldspar, the present data provide independent evidence for very slow cooling rates for mesosiderites and for the slower cooling rates for some cumulate eucrites relative to equilibrated noncumulate eucrites.

  4. The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)

    NASA Astrophysics Data System (ADS)

    Ahadnejad, Vahid; Hirt, Ann Marie; Valizadeh, Mohammad-Vali; Bokani, Saeed Jabbari

    2011-04-01

    The ammonium (NH4+) contents of the Malayer area (Western Iran) have been determined by using the colorimetric method on 26 samples from igneous and metamorphic rocks. This is the first analysis of the ammonium contents of Iranian metamorphic and igneous rocks. The average ammonium content of metamorphic rocks decreases from low-grade to high-grade metamorphic rocks (in ppm): slate 580, phyllite 515, andalusite schist 242. In the case of igneous rocks, it decreases from felsic to mafic igneous types (in ppm): granites 39, monzonite 20, diorite 17, gabbro 10. Altered granitic rocks show enrichment in NH4+ (mean 61 ppm). The high concentration of ammonium in Malayer granites may indicate metasedimentary rocks as protoliths rather than meta-igneous rocks. These granitic rocks (S-types) have high K-bearing rock-forming minerals such as biotite, muscovite and K-feldspar which their potassium could substitute with ammonium. In addition, the high ammonium content of metasediments is probably due to inheritance of nitrogen from organic matter in the original sediments. The hydrothermally altered samples of granitic rocks show highly enrichment of ammonium suggesting external sources which intruded additional content by either interaction with metasedimentary country rocks or meteoritic solutions.

  5. A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Anovitz, Lawrence M.; Lynn, Gary W.; Cole, David R.; Rother, Gernot; Allard, Lawrence F.; Hamilton, William A.; Porcar, Lionel; Kim, Man-Ho

    2009-12-01

    In this paper we report the results of a study using small angle and ultra-small angle neutron scattering techniques (SANS and USANS) to examine the evolution of carbonates during contact metamorphism. Data were obtained from samples collected along two transects in the metamorphosed Hueco limestone at the Marble Canyon, Texas, contact aureole. These samples were collected from the igneous contact out to ˜1700 m. Scattering curves obtained from these samples show mass fractal behavior at low scattering vectors, and surface fractal behavior at high scattering vectors. Significant changes are observed in the surface and mass fractal dimensions as well as the correlation lengths (pore and grain sizes), surface area to volume ratio and surface Gibbs Free energy as a function of distance, including regions of the aureole outside the range of classic metamorphic petrology. A change from mass-fractal to non-fractal behavior is observed at larger scales near the outer boundary of the aureole that implies significant reorganization of pore distributions early in the metamorphic history. Surface fractal results suggest significant smoothing of grain boundaries, coupled with changes in pore sizes. A section of the scattering curve with a slope less than -4 appears at low- Q in metamorphosed samples, which is not present in unmetamorphosed samples. A strong spike in the surface area to volume ratio is observed in rocks near the mapped metamorphic limit, which is associated with reaction of small amounts of organic material to graphite. It may also represent an increase in pore volume or permeability, suggesting that a high permeability zone forms at the boundary of the aureole and moves outwards as metamorphism progresses. Neutron scattering data also correlate well with transmission electron microscopic (TEM) observations, which show formation of micro- and nanopores and microfractures during metamorphism. The scattering data are, however, quantifiable for a bulk rock in a

  6. Partial melting, fluid supercriticality and element mobility in ultrahigh-pressure metamorphic rocks during continental collision

    NASA Astrophysics Data System (ADS)

    Zheng, Yong-Fei; Xia, Qiong-Xia; Chen, Ren-Xu; Gao, Xiao-Ying

    2011-08-01

    Partial melting at continental lithosphere depths plays an important role in generating geochemical variations in igneous rocks. In particular, dehydration melting of ultrahigh-pressure (UHP) metamorphic rocks during continental collision provides a petrological link to intracrustal differentiation with respect to the compositional evolution of continental crust. While island arc magmatism represents one end-member of fluid-induced large-scale melting in the mantle wedge during subduction of the oceanic crust, the partial melting of UHP rocks can be viewed as the other end-member of fluid-induced small-scale anatexis during exhumation of the deeply subducted continental crust. This latter type of melting is also triggered by metamorphic dehydration in response to P-T changes during the continental collision. It results in local occurrences of hydrous melts (even supercritical fluids) as felsic veinlets between boundaries of and multiphase solid inclusions in UHP metamorphic minerals as well as local accumulation of veinlet-like felsic leucosomes in foliated UHP metamorphic rocks and metamorphically grown zircons in orogenic peridotites. Thus, very low-degree melts of UHP rocks provide a window into magmatic processes that operated in continental subduction zones. This article presents a review on available results from experimental petrology concerning the possibility of partial melting under conditions of continental subduction-zone metamorphism, and petrological evidence for the occurrence of dehydration-driven in-situ partial melting in natural UHP rocks during the continental collision. Although the deeply subducted continental crust is characterized by a relative lack of aqueous fluids, the partial melting in UHP rocks commonly takes place during decompression exhumation to result in local in-situ occurrences of felsic melts at small scales. This is caused by the local accumulation of aqueous fluids due to the breakdown of hydrous minerals and the exsolution

  7. One-dimensional thermal modelling of Acadian metamorphism in southern Vermont, USA

    USGS Publications Warehouse

    Armstrong, T.R.; Tracy, R.J.

    2000-01-01

    One-dimensional thermal (1DT) modelling of an Acadian (Devonian) tectonothermal regime in southern Vermont, USA, used measured metamorphic pressures and temperatures and estimated metamorphic cooling ages based on published thermobarometric and geochronological studies to constrain thermal and tectonic input parameters. The area modelled lies within the Vermont Sequence of the Acadian orogen and includes: (i) a western domain containing garnet-grade pre-Silurian metasedimentary and metavolcanic rocks from the eastern flank of an Acadian composite dome structure (Rayponda-Sadawga Dome); and (ii) an eastern domain containing similar, but staurolite- or kyanite-grade, rocks from the western flank of a second dome structure (Athens Dome), approximately 10 km farther east. Using reasonable input parameters based on regional geological, petrological and geochronological constraints, the thermal modelling produced plausible P-T paths, and temperature-time (T-t) and pressure-time (P-t) curves. Information extracted from P-T-t modelling includes values of maximum temperature and pressure on the P-T paths, pressure at maximum temperature, predicted Ar closure ages for hornblende, muscovite and K-feldspar, and integrated exhumation and cooling rates for segments of the cooling history. The results from thermal modelling are consistent with independently obtained pressure, temperature and Ar cooling age data on regional metamorphism in southern Vermont. Modelling results provide some important bounding limits on the physical conditions during regional metamorphism, and indicate that the pressure contemporaneous with the attainment of peak temperature was probably as much as 2.5 kbar lower than the actual maximum pressure experienced by rocks along various particle paths. In addition, differences in peak metamorphic grade (garnet-grade versus staurolite-grade or kyanite-grade) and peak temperature for rocks initially loaded to similar crustal depths, differences in calculated

  8. A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering.

    SciTech Connect

    Anovitz, Lawrence {Larry} M; Lynn, Gary W; Cole, David R

    2009-12-01

    In this paper we report the results of a study using small angle and ultra-small angle neutron scattering techniques (SANS and USANS) to examine the evolution of carbonates during contact metamorphism. Data were obtained from samples collected along two transects in the metamorphosed Hueco limestone at the Marble Canyon, Texas, contact aureole. These samples were collected from the igneous contact out to {approx}1700 m. Scattering curves obtained from these samples show mass fractal behavior at low scattering vectors, and surface fractal behavior at high scattering vectors. Significant changes are observed in the surface and mass fractal dimensions as well as the correlation lengths (pore and grain sizes), surface area to volume ratio and surface Gibbs Free energy as a function of distance, including regions of the aureole outside the range of classic metamorphic petrology. A change from mass-fractal to non-fractal behavior is observed at larger scales near the outer boundary of the aureole that implies significant reorganization of pore distributions early in the metamorphic history. Surface fractal results suggest significant smoothing of grain boundaries, coupled with changes in pore sizes. A section of the scattering curve with a slope less than -4 appears at low-Q in metamorphosed samples, which is not present in unmetamorphosed samples. A strong spike in the surface area to volume ratio is observed in rocks near the mapped metamorphic limit, which is associated with reaction of small amounts of organic material to graphite. It may also represent an increase in pore volume or permeability, suggesting that a high permeability zone forms at the boundary of the aureole and moves outwards as metamorphism progresses. Neutron scattering data also correlate well with transmission electron microscopic (TEM) observations, which show formation of micro- and nanopores and microfractures during metamorphism. The scattering data are, however, quantifiable for a bulk rock

  9. Extreme metasomatism during high-P-T contact metamorphism in southeastern NY, and its tectonic implications

    NASA Astrophysics Data System (ADS)

    Dorfler, K. M.; Tracy, R. J.; Caddick, M. J.

    2011-12-01

    An important goal of high-T metamorphic petrology is to link the micrometer-scale details of mineral assemblages and textures to large-scale tectonic processes, by understanding the evolution of metamorphic conditions such as pressure and temperature. Pelitic schists from contact aureoles around mafic-ultramafic plutons in Westchester County, NY record a high-P (ca. 0.8 GPa) high-T (up to 775°C) contact overprint on a Taconic regional metamorphic assemblage (ca. 0.55 GPa). The contact metamorphic assemblage of a sample in the innermost aureole of the Croton Falls pluton, a small (<10 km2) gabbroic pluton, consists of qz+plg+bt+grt+sil+ilm+gr+Zn-rich Al-spl, with neither kfs nor mu, and with abundant bt, plg, sil, and qz inclusions within euhedral garnet crystals. Unusually low Na and K contents imply depletion of alkalic components and silica through anatexis and melt extraction during contact heating. This can be verified by tracing depleted lithologies in the contact aureole into typical metapelites outside the aureole. Theromobarometry on nearby samples lacking a contact overprint yields 620-640°C and 0.5-0.6 GPa. In the aureole sample, WDS X-ray maps show distinct Ca-enriched rims on both grt and matrix plg and significantly higher Mg content in bt inclusions within grt than in matrix bt. GASP and Grt-Bt Mg-Fe equilibria on the garnet host and inclusions interior to the high-Ca rim zone yield P=0.53 GPa and T=625°C. Pairs in the modified rim zone yield 0.8 GPa and 766°C. THERMOCALC average P-T calculations yield similar results for core (0.52 GPa, 648°C) and rim (0.78 GPa, 763°C) equilibria. These multi-phase equilibria suggest a degree of disequilibrium between phases, presumably reflecting partial resetting after metamorphic peak conditions. Garnet porphyroblasts grown during regional metamorphism at 465 Ma were substantially re-equilibrated during the contact event (~ 435 Ma). Pervasive melting at this stage is associated with development of a high

  10. The Alta Stock, Utah: An Exemplar Rock Suite for Learning Metamorphic Concepts

    NASA Astrophysics Data System (ADS)

    Davidson, C.; Haileab, B.

    2003-12-01

    Using rock suites in a discovery-based setting is a terrific way to learn important petrologic processes and concepts such as the role of fluids during metamorphism, phase equilibrium, and metastability to name just a few. A particularly effective rock suite we use in our petrology course is from the contact aureole of the Tertiary Alta stock in Utah. The intrusion of the Alta stock into Paleozoic dolostone containing chert nodules produced a well-defined contact metamorphic aureole that includes talc-, tremolite-, forsterite-, and periclase-in field isograds (Cook and Bowman, 2000). Students work in free-form groups with collaboration between groups to define the mineral assemblages using hand samples and thin sections from throughout the areole and then work out what they think are the important petrologic processes that worked together to form what they see. The main goals of the exercise include: 1) learning to identify mineral assemblages common to metamorphosed siliceous dolostones; 2) learning to infer metamorphic reactions from progressive changes in mineral assemblages; 3) being able to identify balanced metamorphic reactions responsible for isograds mapped in the field; 4) begin to develop an understanding of how bulk composition and fluid composition controls mineral assemblages; and 5) learning how to infer the temperature and fluid composition evolution of the Alta stock aureole based on published T-X(CO2)diagrams. This suite is particularly effective because all the important minerals the students observe in thin section can be defined by the easy to plot and understand CaO-MgO-SiO2 system. This offers the opportunity to introduce (or reinforce) the concept of plotting minerals in composition space, using the phase rule to define the variance of your system, using tie lines to define stable mineral assemblages, and the flipping of tie lines to produce univariant reactions. In addition, the students work out the topology of these reactions in P-T space

  11. Zircon response to high-grade metamorphism as revealed by U-Pb and cathodoluminescence studies

    NASA Astrophysics Data System (ADS)

    Siebel, W.; Shang, C. K.; Thern, E.; Danišík, M.; Rohrmüller, J.

    2012-11-01

    Correct interpretation of zircon ages from high-grade metamorphic terrains poses a major challenge because of the differential response of the U-Pb system to metamorphism, and many aspects like pressure-temperature conditions, metamorphic mineral transformations and textural properties of the zircon crystals have to be explored. A large (c. 450 km2) coherent migmatite complex was recently discovered in the Bohemian Massif, Central European Variscides. Rocks from this complex are characterized by granulite- and amphibolite-facies mineral assemblages and, based on compositional and isotopic trends, are identified as the remnants of a magma body derived from mixing between tonalite and supracrustal rocks. Zircon crystals from the migmatites are exclusively large (200-400 μm) and yield 207Pb/206Pb evaporation ages between 342-328 Ma and single-grain zircon fractions analysed by U-Pb ID-TIMS method plot along the concordia curve between 342 and 325 Ma. High-resolution U-Pb SHRIMP analyses substantiate the existence of a resolvable age variability and yield older 206Pb/238U ages (342-330 Ma, weighted mean age = 333.6 ± 3.1 Ma) for inner zone domains without relict cores and younger 206Pb/238U ages (333-320 Ma, weighted mean age = 326.0 ± 2.8 Ma) for rim domains. Pre-metamorphic cores were identified only in one sample (206Pb/238U ages at 375.0 ± 3.9, 420.3 ± 4.4 and 426.2 ± 4.4 Ma). Most zircon ages bracket the time span between granulite-facies metamorphism in the Bohemian Massif (~345 Ma) and the late-Variscan anatectic overprint (Bavarian phase, ~325 Ma). It is argued that pre-existing zircon was variously affected by these metamorphic events and that primary magmatic growth zones were replaced by secondary textures as a result of diffusion reaction processes and replacement of zircon by dissolution and recrystallization followed by new zircon rim growth. Collectively, the results show that the zircons equilibrated during high-grade metamorphism and record

  12. Metamorphism of CO3 Chondrites: A Carbon and Nitrogen Isotope Study

    NASA Astrophysics Data System (ADS)

    Newton, J.; Arden, J. W.; Pillinger, C. T.

    1992-07-01

    Our previous work involving carbon and nitrogen abundance and isotopic composition of Ornans group chondrites (1) has shown that these measurements have the potential for investigating parent body metamorphism, and we now expand this study. The HF/HCl residues of Colony, Kainsaz, Ornans, Lance and Acfer 094 show unimodal carbon yield profiles. The peak yields are seen to increase as a function of temperature according to known petrologic subtype (2), revealing a concordant increase in the crystallinity of the amorphous carbon with progressive metamorphism. Only the least metamorphosed Colony and Acfer 094 residues display any evidence of presolar silicon carbide. The inference here is that silicon carbide is destroyed during only mild metamorphism. Chromic and perchloric acid residues have revealed that CO3 diamonds are characterized by delta^13C minima of between -34.3o/oo and -40.3o/oo and delta^15N minima of -342+-9.2o/oo, consistent with similar work on other chondrites (3). C/N ratios of diamonds have been used as indicators of relative metamorphic grade (3,4), as nitrogen-rich diamonds are presumed to be lost progressively during metamorphism (5). On this basis, Colony has undergone a much lesser degree of metamorphism than Kainsaz or Lance which are less distinguishable on a C/N plot. An experiment on Ornans which provided only incomplete data suggests that its C/N plateau lies slightly above that of Colony, in agreement with its subtype. The diamond contents of these meteorites are 135 ppm (Colony), 61 ppm (Kainsaz) and 59 ppm (Lance), showing that diamond is present to moderate grades of metamorphism. Carbon data for silicon carbide has been acquired for Colony, Kainsaz and Lance from high temperature experiments on the diamond residues. The amount of SiC in Colony is now established as about 1 ppm of the whole-rock. Neither Kainsaz nor Lance show evidence of silicon carbide, although both show a heavy carbon component combusting around 800 degrees C

  13. The angiotensin converting enzyme inhibitory tripeptides Ile-Pro-Pro and Val-Pro-Pro show increasing permeabilities with increasing physiological relevance of absorption models.

    PubMed

    Foltz, Martin; Cerstiaens, Anja; van Meensel, Ans; Mols, Raf; van der Pijl, Pieter C; Duchateau, Guus S M J E; Augustijns, Patrick

    2008-08-01

    Transepithelial transport of the ACE inhibitory peptides Ile-Pro-Pro and Val-Pro-Pro was studied in different models of absorption. Apparent permeability (P(app)) values for absorptive transport across Caco-2 monolayers were 1.0+/-0.9 x 10(-8) (Ile-Pro-Pro) and 0.5+/-0.1 x 10(-8)cms(-1) (Val-Pro-Pro). Ex vivo transport across jejunal segments in the Ussing chamber was 5-times (Ile-Pro-Pro) to 10-times (Val-Pro-Pro) higher with no significant differences (p>0.05) observed between both peptides. The peptidase inhibitor bestatin increased permeability for the absorptive direction for Ile-Pro-Pro by twofold. Neither a transepithelial pH gradient nor increased apical tripeptide concentration nor longitudinal localization of the intestinal segment influenced P(app) in the ex vivo experiments. Val-Pro-Pro transport across Peyer's patches, however, was 4-times higher (P(app)=21.0+/-9.3 x10(-8)cms(-1)) as compared to duodenum (P(app)=4.8+/-1.4 x 10(-8)cms(-1)). In the in situ perfusion experiments P(app) values varied greatly among different animals ranging from 0.5 to 24.0 x10(-8)cms(-1) (Ile-Pro-Pro) and from 1.0 to 15.6 x 10(-8)cms(-1) (Val-Pro-Pro). In summary, Caco-2 and ex vivo absorption models differ considerably regarding their peptide permeability. The in situ model seems to be less appropriate because of the observed large variability in peptide permeability. The results of this study demonstrate that the ACE inhibitory peptides Ile-Pro-Pro and Val-Pro-Pro are absorbed partially undegraded. PMID:18490081

  14. The Val142Ile transthyretin cardiac amyloidosis: not only an Afro-American pathogenic variant? A single-centre Italian experience.

    PubMed

    Cappelli, Francesco; Frusconi, Sabrina; Bergesio, Franco; Grifoni, Elisa; Fabbri, Alessia; Giuliani, Costanza; Falconi, Serena; Bonifacio, Stefania; Perfetto, Federico

    2016-02-01

    Transthyterin amyloidosis is a life-threatening disorder caused by the deposition of hepatocyte-derived transthyretin (TTR) amyloid in various tissues and organs. The most common worldwide pathogenic variant with almost exclusive cardiac involvement is Val142Ile with an allele frequency of 3.5% in U.S. African-American population, but supposed extremely rare, with only sporadic cases in Caucasian patients. Unexpectedly, in our amyloidosis referral centre, we identified five patients (15.1% of all TTRm diagnosed patients, three families, two singleton) with Val142Ile variant belonging to unrelated families of Caucasian origin. Molecular study was performed in a total of 10 individuals of which three were Italian families (three affected individuals and five unaffected individuals) and two were singleton (one Italian patient and one patient from Argentine with Spanish ancestry). Sequence analysis of TTR gene revealed the presence of the heterozygous Val142Ile in the five affected patients and in five asymptomatic individuals. All probands underwent, at diagnosis, a complete clinical, echocardiographic and biohumoral evaluation. To the best of our knowledge, we describe the larger report of Caucasian patients with Val142Ile cardiomyopathy. All patients at diagnosis showed symptoms of heart failure with increased thickness of left ventricular walls and systo-diastolic left ventricular dysfunction. They also showed increased plasma values of NT-proBNP and troponin I. Our data confirm that Caucasian patients with the Val142Ile pathogenic variant have phenotypic manifestations similar to that of African-American one. Moreover, our data clearly show that Val142Ile pathogenic variant is not only an African-American mutation but could be also an underestimated Caucasian variant. PMID:26428663

  15. Very low-grade metamorphism of Rheno-Hercynian allochthons (Variscides, Germany): facts and tectonic consequences

    NASA Astrophysics Data System (ADS)

    Doublier, Michael Patrick; Potel, Sébastien; Franke, Wolfgang; Roache, Tony

    2012-07-01

    The Hörre Belt in the SE part of the Rhenish Massif has been regarded as autochthonous because of the apparent lack of metamorphic inversion. We have performed a K-white mica study using powder X-ray diffraction derived Kübler Index (KI) and K-white mica b cell dimension, and the spectrally derived wavelength of the 2,200 nm absorption feature ("2200wvl") of supposedly allochthonous units and the underlying par-autochthon. KI reveals a slight, but significant inversion of metamorphic grade, which shows that the Hörre Belt and the Hessische Schieferserie adjacent to the South were emplaced by thrusting after they had acquired peak metamorphism ( M 1) in deeper parts of the orogenic wedge. Only in the westernmost part of the study area, the par-autochthon and the allochthon show the same grade of anchizonal metamorphism. This observation, together with K-white mica b cell dimensions <9.000 Å and 2200wvl <2,204 nm, suggests a second, low-pressure metamorphism M 2 subsequent to the emplacement of the allochthon. This is supported by an anomaly of published conodont alteration index data. Our results expand the original width of the Rheno-Hercynian passive margin to at least 580, more probably to 670 or even 750 km. Palinspastic restoration also reveals that the Givetian to Early Carboniferous volcanic belt of the Lahn/Dill area is not only younger than the Emsian MORB-type lavas of the Rheno-Hercynian ocean, but was also separated, from the latter, by a largely non-volcanic belt of at least c. 220 km width. Apparently, the Givetian to Early Carboniferous volcanic episodes were unrelated to the Rheno-Hercynian drift stage.

  16. Formation of Neoproterozoic metamorphic complex during oblique convergence (Eastern Desert, Egypt)

    NASA Astrophysics Data System (ADS)

    Fritz, H.; Wallbrecher, E.; Khudeir, A. A.; Abu el Ela, F.; Dallmeyer, D. R.

    1996-10-01

    Major portions of the Pan-African Orogen in the Eastern Desert of Egypt were formed by island-arc accretion in the Neoproterozoic. These areas are characterized by their lack of major crustal thickening. Metamorphic core complexes occur parallel to the strike of the Eastern Desert Orogen. These domes exhibit polyphase metamorphism and deformation in contrast to the structurally overlying nappes which include ophiolitic melanges and island-arc volcanic rocks. These nappes show northwest directed, orogen-parallel thrusting in the internal parts and west to southwest directed imbrication in the external parts of the orogen. Structures related to exhumation of the metamorphic core complexes partition into different displacement paths localized within a crustal-scale wrench corridor of the Najd fault system. Northwest trending orogen-parallel, sinistral strike-slip faults define the western and eastern margins of the domes. North and south dipping low-angle normal faults developed along the northern and southern margins of the domes and form extensional bridges between them. {40Ar}/{39Ar} ages obtained from syntectonic muscovites within the shear zones gave Neoproterozoic ages of 595.9±0.5 and 588.2±0.3 Ma. The synchronous activity of strike-slip and normal faults suggests a regional east-west shortening which was accomodated by deep-level basal decollement beneath the metamorphic core complexes and a coeval northwest-southeast, orogen-parallel extension. This extension was accompanied by intramontane molasse sedimentation and emplacement of calc-alkaline plutons. Since the rapid exhumation of gneisses in the core complexes cannot be explained by thickening of the crust, the authors favour a model which calls for enhanced heat flow along the Najd fault system which would have enabled the formation of syn-extensional plutonism and triggered the exhumation of the metamorphic core complexes. Lateral buoyancy forces were concentrated within the Najd wrench corridor and

  17. Geospeedometry and the metamorphic history of the Late Cretaceous Chiwaukum Schist, west central Washington state

    SciTech Connect

    Evans, D.A. . Div. of Geological and Planetary Sciences); Lasaga, A.C.; Ague, J.J.; Brandon, M.T. . Dept. of Geology and Geophysics)

    1993-04-01

    The Chiwaukum Schist on the NE side of the Late Cretaceous Mount Stuart batholith (MSB) shows evidence of a low-P contact metamorphism, followed by a higher-P amphibolite-facies regional metamorphism (Evans and Berti, 1986). Samples were collected from this contact zone in order to quantify the time-temperature history of the schist using the geospeedometry method of Lasaga (1983). Pseudomorphic textures and garnet-aluminosilicate-plagioclase (GASP) geobarometry within some samples show an increase in pressure during crystal growth, consistent with the interpretation of Evans and Berti (1986), that regional metamorphism followed intrusion of the MSB. Geospeedometry exploits the kinetics of diffusion associated with the thermo-barometric exchange reactions in order to determine the retrograde cooling history of a metamorphic rock. This technique was applied using Fe-Mg diffusion between garnet and biotite as defined by that geothermometer. Modeling results indicate that the region was exhumed and cooled from about 22 km and 610 C to about 8 km and 525 C, in a period of about 2.5 Myr. The average exhumation rate is 5.6 km/Myr. These results are consistent with existing isotopic ages, which indicate that the northeast MSB was intruded at about 95 Ma (K/Ar hornblende and U/Pb zircon) and that the Chiwaukum Schist cooled through temperatures of about 350 C at 86 to 83 Ma (K/Ar muscovite). Rapid unroofing appears to follow shortly after the climax of crustal thickening within the Cascade metamorphic core and may be related to erosional and/or tectonic denudation within a mountainous collisional orogen.

  18. Relationships between deformation and metamorphism in the western Inner Piedmont, North Carolina

    SciTech Connect

    Yanagihara, G.M.; Davis, T.L. . Dept. of Geological Sciences)

    1992-01-01

    Geologic mapping conducted in a 700 km[sup 2] area of western NC has revealed the presence of three dominant lithotectonic units of the western Inner Piedmont (IP). These units include in ascending structural order: (1) the Henderson Gneiss (HG), a mylonitic granitic gneiss; (2) the Poor Mountain Formation (PM), which includes biotite gneiss amphibolite, quartzite, and pelitic schist; and (3) the Mill Spring formation (MS) containing biotite gneiss, amphibolite, and pelitic schist intruded by granitoid. Each unit is bordered by a ductile thrust fault, has a fold-nappe style geometry, and was stacked from NW to SE. Metamorphic conditions, as indicated by the presence of sillimanite and muscovite in the pelitic schists of the MS and the PM are upper amphibolite facies. While no pelitic schists occur in the HG, the textural evidence also indicates that metamorphic conditions are upper amphibolite facies. This contrasts with the western Piedmont of SC were metamorphic conditions in the PM and the HG were upper greenschist to lower amphibolite facies. An episode of retrograde metamorphism is indicated by the presence of chlorite in widely scattered parts of the MS and the PM and is not associated with any tectonic fabric. The study area has undergone one major episode of deformation that was contemporaneous with metamorphism and emplacement of thrust sheets. The wide separation arc shown by the analysis is due to a change in transport direction indicated by the change in orientation of lineations and shear-sense indicators from E-W toward the SE to NE-SW toward the NW. This change in the lineations and shear-sense indicators is related to synmetamorphic combined westward thrusting of IP thrust sheets and early or middle Paleozoic dextral motion on the Brevard fault zone.

  19. Chemical and physical studies of type 3 chondrites - VIII: Thermoluminescence and metamorphism in the CO chondrites

    SciTech Connect

    Keck, B.D.; Sears, D.W.G. )

    1987-11-01

    The thermoluminescence properties of nine CO chondrites have been measured. With the exception of Colony and Allan Hills A77307 (ALHA 77307), whose maximum induced TL emission is at approximately 350{degree}C, CO chondrites exhibit two TL peaks, one at 124 {plus minus} 7{degree}C (130{degree}C peak) and one at 252 {plus minus} 7{degree}C (250{degree}C peak). The 130{degree}C peak shows a 100-fold range in TL sensitivity and correlates with various metamorphism-related phenomena, such as silicate heterogeneity, metal composition and McSween's metamorphic subtypes. The peak at 250{degree}C does not show these correlations and, Colony excepted, varies little throughout the class. Mineral separation experiments, and a series of annealing experiments on Isna, suggest that the TL properties for CO chondrites reflect the presence of feldspar in two forms, (1) a form produced during metamorphism, and analogous to the dominant form of feldspar in type 3 ordinary chondrites, and (2) a primary, metamorphism-independent form, perhaps associated with the amoeboid inclusions. If this interpretation is correct, then the CO chondrites have not experienced temperatures above the order/disorder temperature for feldspar (500-600{degree}C) and they cooled more slowly than comparable type 3 ordinary chondrites. Colony and ALHA 77307 have atypical TL properties, including very low TL sensitivity, suggesting that phosphors other than feldspar are important. They have apparently experienced less metamorphism than the others, and may have also been aqueously altered.

  20. The timing of metamorphism in the Odenwald-Spessart basement, Mid-German Crystalline Zone

    NASA Astrophysics Data System (ADS)

    Will, T. M.; Schulz, B.; Schmädicke, E.

    2016-07-01

    New in situ electron microprobe monazite and white mica 40Ar/39Ar step heating ages support the proposition that the Odenwald-Spessart basement, Mid-German Crystalline Zone, consists of at least two distinct crustal terranes that experienced different geological histories prior to their juxtaposition. The monazite ages constrain tectonothermal events at 430 ± 43 Ma, 349 ± 14 Ma, 331 ± 16 Ma and 317 ± 12 Ma/316 ± 4 Ma, and the 40Ar/39Ar analyses provide white mica ages of 322 ± 3 Ma and 324 ± 3 Ma. Granulite-facies metamorphism occurred in the western Odenwald at c. 430 and 349 Ma, and amphibolite-facies metamorphism affected the eastern Odenwald and the central Spessart basements between c. 324 and 316 Ma. We interpret these data to indicate that the Otzberg-Michelbach Fault Zone, which separates the eastern Odenwald-Spessart basement from the Western Odenwald basement, is part of the Rheic Suture, which marks the position of a major Variscan plate boundary separating Gondwana- and Avalonia-derived crustal terranes. The age of the Carboniferous granulite-facies event in the western Odenwald overlaps with the minimum age of eclogite-facies metamorphism in the adjacent eastern Odenwald. The granulite- and eclogite-facies rocks experienced contrasting pressure-temperature paths but occur in close spatial proximity, being separated by the Rheic Suture. As high-pressure and high-temperature metamorphisms are of similar age, we interpret the Odenwald-Spessart basement as a paired metamorphic belt and propose that the adjacent high-pressure and high-temperature rocks were metamorphosed in the same subduction zone system. Juxtaposition of these rocks occurred during the final stages of the Variscan orogeny along the Rheic Suture.

  1. Oxygen isotope constraints on metamorphic fluid flow, Townshend Dam, Vermont, USA

    SciTech Connect

    Kohn, M.J.; Valley, J.W.

    1994-12-01

    Fluid-rock interaction during amphibolite-facies metamorphism has been investigated for rocks exposed in a single 400 m long, lithologically heterogeneous outcrop near Townshend, Vermont, USA. Oxygen isotopic compositions have been measured in profiles across single garnet crystals from thirteen samples, and from hornblende and garnet separates from thirty-three fine-grained samples. This outcrop was previously studied, who measured large oxygen isotope gradients (3{per_thousand}) in garnets from one sample, and inferred large amounts of pervasive fluid flow. All of the garnets that we have analyzed show less isotopic zonation, {le}1{per_thousand}, twelve of them have zonation <0.5{per_thousand}, and the mineral separate data imply both a strong correlation of isotopic composition with rock type and large gradients in peak metamorphic fluid isotopic compositions. Although devolatilization reactions in these rocks must have produced metamorphic fluids, the data preclude cross-foliation time-integrated fluid fluxes greater than 300-600 cm{sup 3}/cm{sup 2} during prograde amphibolite-facies metamorphism. The isotopic trends can all be interpreted in terms of closed-system behavior, channeled fluid flow, or diffusive exchange of oxygen in an interconnected grain-boundary fluid, and within uncertainty cross-strike advective fluxes could have been zero. Any significant flow at this locality was dominantly either layer parallel or channeled out of the system in veins. If all fluid flow occurred in veins, then their spacing must have been less than 300-600 m. The data are inconsistent with massive and pervasive metamorphic fluid flow across strike but do not address layer parallel flow.

  2. Crustal channel flows: 2. Numerical models with implications for metamorphism in the Himalayan-Tibetan orogen

    NASA Astrophysics Data System (ADS)

    Jamieson, Rebecca A.; Beaumont, Christopher; Medvedev, Sergei; Nguyen, Mai H.

    2004-06-01

    Results from a thermal-mechanical model (HT1) that includes midcrustal channel flow are compatible with many features of the Himalayan-Tibetan system. Radioactive self-heating and rheological weakening of thickened model orogenic crust lead to the formation of a hot, low-viscosity midcrustal channel and a broad plateau. Channel material, corresponding to the Greater Himalayan Sequence (GHS), flows outward from beneath the plateau in response to topographically induced differential pressure. At the plateau flank it is exhumed by focused surface denudation and juxtaposed with cooler, newly accreted material corresponding to the Lesser Himalayan Sequence (LHS). The model channel is bounded by coeval thrust and normal sense ductile shear zones, interpreted to represent the Main Central Thrust (MCT) zone and South Tibetan Detachment system, respectively. Inverted metamorphism associated with the model MCT zone results from distributed ductile shear along the MCT and extrusion of the hot channel. A variety of model P-T-t path styles, resembling those observed in the GHS and LHS, are produced for points traveling through contrasting tectonic regimes that coexist in different parts of the model. Predicted times of peak metamorphism, cooling, and erosion of metamorphic facies are generally compatible with observations, although model GHS cooling ages are too young. The times of M1 and M2 metamorphic "events" observed in the GHS correspond to model times of maximum burial and maximum heating, respectively. The results highlight the need to integrate tectonics and metamorphism in continental collision models and demonstrate the importance of lateral transport of both heat and material in large hot orogens.

  3. Combined thermodynamic-geochemical modeling in metamorphic geology: Boron as tracer of fluid-rock interaction

    NASA Astrophysics Data System (ADS)

    Konrad-Schmolke, Matthias; Halama, Ralf

    2014-11-01

    Quantitative geochemical modeling is today applied in a variety of geological environments from the petrogenesis of igneous rocks to radioactive waste disposal. In addition, the development of thermodynamic databases and computer programs to calculate equilibrium phase diagrams has greatly advanced our ability to model geodynamic processes. Combined with experimental data on elemental partitioning and isotopic fractionation, thermodynamic forward modeling unfolds enormous capacities that are far from exhausted. In metamorphic petrology the combination of thermodynamic and trace element forward modeling can be used to study and to quantify processes at spatial scales from μm to km. The thermodynamic forward models utilize Gibbs energy minimization to quantify mineralogical changes along a reaction path of a chemically open fluid/rock system. These results are combined with mass balanced trace element calculations to determine the trace element distribution between rock and melt/fluid during the metamorphic evolution. Thus, effects of mineral reactions, fluid-rock interaction and element transport in metamorphic rocks on the trace element and isotopic composition of minerals, rocks and percolating fluids or melts can be predicted. Here we illustrate the capacities of combined thermodynamic-geochemical modeling based on two examples relevant to mass transfer during metamorphism. The first example focuses on fluid-rock interaction in and around a blueschist-facies shear zone in felsic gneisses, where fluid-induced mineral reactions and their effects on boron (B) concentrations and isotopic compositions in white mica are modeled. In the second example, fluid release from a subducted slab, the associated transport of B as well as variations in B concentrations and isotopic compositions in liberated fluids and residual rocks are modeled. We compare the modeled results of both examples to geochemical data of natural minerals and rocks and demonstrate that the combination

  4. Ultrahigh-temperature metamorphism under isobaric heating: New evidence from the North China Craton

    NASA Astrophysics Data System (ADS)

    Yang, Qiong-Yan; Santosh, M.; Tsunogae, Toshiaki

    2014-12-01

    The Khondalite Belt within Inner Mongolia Suture Zone (IMSZ) in the North China Craton (NCC) preserves evidence for extreme crustal metamorphism under ultra-high temperature (UHT) conditions at ca. 1.92 Ga, associated with the subduction-collision tectonics between the Yinshan and Ordos Blocks. Here we report a new locality in Hongsigou where cordierite- and spinel-bearing granulites record UHT metamorphism. The prograde, peak, and retrograde mineral assemblages in these pelitic granulites have been identified based on petrography and mineral chemistry as: Bt1 + Grt1 + Sil1 + Kfs1 + Pl1 + Ilm + Qtz1, Grt1 + Sil2 + Kfs2 + Pl2 + Spl + Ilm + Qtz2 + Liq, and Crd + Grt2 + Sil3 + Kfs2 + Pl2 + Ilm + Qtz2 respectively. The peak metamorphic conditions of the pelitic granulite were estimated as 930-1050 °C and 6.5-7.5 kbar based on pseudosection analysis in the system NCKFMASHTO, suggesting extreme thermal metamorphism. We report LA-ICPMS zircon U-Pb data from the granulite which show weighted mean 207Pb/206Pb age of 1881 ± 6.6 Ma, marking the timing of UHT metamorphism. Lu-Hf analyses of the zircons show εHf(t) values within a restricted range of -4.2 to 0.3 and together with Hf model ages, a Paleoproterozoic arc magmatic source is inferred for the detrital zircons. The estimated P-T path for the UHT granulite suggests isobaric heating followed by cooling and decompression along a clockwise trajectory, different from the anti-clockwise P-T paths defined in earlier studies for the 1.92 Ga UHT rocks from the IMSZ. The younger age and the isobaric heating trajectory suggest that the Hongsigou UHT rocks are related to heat input from underplated mafic magmas following continental collision.

  5. Duration of inverted metamorphic sequence formation across the Himalayan Main Central Thrust (MCT), Sikkim

    NASA Astrophysics Data System (ADS)

    Cioldi, Stefania; Moulas, Evangelos; Tajcmanová, Lucie; Burg, Jean-Pierre

    2016-04-01

    Collision between the Indian and Eurasian plates since the Eocene (50 Ma) caused the closure of the Neo-Tethys and the underthrusting of India beneath the Tibetan Plateau, generating the 2500 km extended Himalayan belt. The Main Central Thrust (MCT) marks the boundary of the underlying Midland Lower Himalaya metasediments zone (LH) in the south from the overlying high grade metamorphic Higher Himalaya (HH) in the north. Several models considering petrochronology, geothermobarometry and structural geology have been discussed to explain the inverted metamorphic gradient in the LH metasediments without reaching a common agreement. This study investigates the tectonic setting and the timescale of inverted isograds related to crustal-scale thrusting at the MCT in the Sikkim region, northeast India. The aim is to contribute to the understanding of the link between mechanical and thermal evolution of major thrust zones and to clarify the nature and the origin of orogenic heat applying garnet geospeedometry. Garnets provide a sensitive record of metamorphic conditions and are potential chronometer. Their compositional zoning is used as a gauge for rate estimates of element diffusion within the mineral and allows estimating the absolute time of the thermal evolution. Inverse-fitting numerical model considering FRactIonation and Diffusion in GarnEt (FRIDGE) calculates garnet composition profiles by introducing P-T-t paths and bulk-rock composition of a specific sample. P-T conditions were estimated by convectional geothermobarometry supported by phase equilibria modelling and measured garnet chemical compositions. Simulation were compared with measured garnet profiles. Simple step function and FRIDGE preliminary results of Fe-Mg - Ca - Mn garnet fractionation-diffusion modelling indicate very short timescale (between 3 and 6 Ma) for peak metamorphic conditions in the northeast Himalayan collisional system. This duration does not allow thermal re-equilibration. It is an

  6. Upper Cretaceous exhumation of the western Rhodope Metamorphic Province (Chalkidiki Peninsula, northern Greece)

    NASA Astrophysics Data System (ADS)

    Kydonakis, Konstantinos; Gallagher, Kerry; Brun, Jean-Pierre; Jolivet, Marc; Gueydan, Frédéric; Kostopoulos, Dimitrios

    2014-06-01

    The Vertiskos Unit of northern Greece is an elongated basement belt with a complex poly-metamorphic history. It extends from Greece (Chalkidiki peninsula), to the south, up to Serbia, in the north, and arguably represents the westernmost part of the Rhodope Metamorphic Province (northern Greece to southern Bulgaria). The Vertiskos Unit experienced a medium pressure lower amphibolite-facies metamorphic overprint during the Alpine Orogeny. The available medium-temperature geochronology implies that it remained at temperature of approximately 300°C (or slightly higher) during Lower Cretaceous. In order to constrain its post-Lower Cretaceous thermal history, until near-surface exposure, we applied apatite fission track analysis. The central ages obtained range from 68.5 ± 3.8 to 46.6 ± 3.6 Ma (uppermost Cretaceous to Middle Eocene) and mean track lengths between 13 and 13.5 µm. We applied two inverse thermal modeling approaches using either each sample independently (high degree of freedom in the thermal history, better data fit) or all samples together interpreting them as a vertical profile (simpler thermal history, worse data fit). Irrespective of the modeling approach, we conclude that the bulk thermal history of the Vertiskos Unit crosses the high-temperature limit of the apatite partial annealing zone by the uppermost Cretaceous and reaches near-surface conditions as early as lower/middle Eocene. These results contrast with the thermal history of the other domains of the Rhodope Metamorphic Province further east (namely the Southern Rhodope Core Complex and the Northern Rhodope Complex) and establish the Vertiskos basement complex as the oldest exhumed coherent basement fragment of the Rhodope Metamorphic Province and Greece.

  7. Zircon SHRIMP U-Pb dating of metamorphic complexes in the conjunction of the Greater and Lesser Xing'an ranges, NE China: Timing of formation and metamorphism and tectonic implications

    NASA Astrophysics Data System (ADS)

    Miao, Laicheng; Zhang, Fuqin; Zhu, Mingshuai; Liu, Dunyi

    2015-12-01

    Metamorphic complexes, including the Luomahu, Xinkailing and Fengshuigouhe groups, are scattered in the conjunction of the Greater and the Lesser Xing'an ranges, NE China, and have long been interpreted to represent the Precambrian basement of the so-called "Xing'an" and "Songnen" blocks although reliable evidence is lacking. Thin-section examination and mineral assemblage indicate that the protoliths of these metamorphic rocks are mainly meta-sedimentary and meta-volcanic rocks and have experienced greenschist- to amphibolite-facies metamorphism and strong deformation. Zircon SHRIMP U-Pb dating results of the metamorphic complexes and associated pre- or syn-kinematic veins constrained the formation and metamorphic ages of the Luomahuo Group at 175 ± 3 Ma and 159 ± 3 Ma, the Xingkailing Group at 200 ± 2 Ma and 158 ± 3 Ma, and the Fengshuigouhe Group at between 230-310 Ma and 170 ± 3 Ma, respectively. Additionally, all these rocks contain some Late Paleozoic detrital or inherited zircons with ages between 290-390 Ma, but no Precambrian, even if Early Paleozoic, age information was detected from these metamorphic rocks. These new data suggest that the metamorphic complexes were formed during Mesozoic-Late Paleozoic period, rather than in Precambrian as previously inferred, and that all of them underwent metamorphism and deformation during Middle Jurassic between 170-160 Ma. Consequently, these metamorphic complexes are not basement rocks of the so-called Precambrian continental blocks. Instead, there are likely metamorphosed Late Paleozoic-Mesozoic accretionary complexes and/or arc terranes. These results, in combination with published data, illustrate an overall young trend from north to south in the tectonic evolution of the northern Xing'an region. Significantly, the Jurassic (170-160 Ma) metamorphism and deformation event firstly identified by this study from the metamorphic complexes likely recorded the coinstantaneous Mongol-Okhotsk collisional and

  8. Short-Wavelength Infrared (SWIR) spectroscopy of low-grade metamorphic volcanic rocks of the Pilbara Craton

    NASA Astrophysics Data System (ADS)

    Abweny, Mohammad S.; van Ruitenbeek, Frank J. A.; de Smeth, Boudewijn; Woldai, Tsehaie; van der Meer, Freek D.; Cudahy, Thomas; Zegers, Tanja; Blom, Jan-Kees; Thuss, Barbara

    2016-05-01

    This paper shows the results of Short-Wavelength Infrared (SWIR) spectroscopy investigations of volcanic rocks sampled from low-grade metamorphic greenstone belts of the Archean Pilbara Craton in Western Australia. From the reflectance spectra a range of spectrally active minerals were identified, including chlorites, hornblende, actinolite, epidote and white micas. The rock samples were grouped into mineral assemblages based on their spectrally identified minerals and stratigraphic positions. The metamorphic amphibolite and greenschist facies could be identified from the SWIR spectroscopic data as well as three sub zones of the greenschist facies: 1) a zone containing Fe-chlorite; 2) a zone containing intermediate chlorite and epidote; and 3) a zone containing intermediate chlorite, actinolite and hornblende. Spectral parameters were calculated from the reflectance spectra to assess the metamorphic grade and zones. Plots of the depth parameters of the Fe-OH feature near 2250 nm versus the Mg-OH feature near 2390 nm differentiate the metamorphic amphibolite and greenschist facies and a transition zone between the two. The wavelength position parameter of the Mg-OH absorption feature near 2340 nm also serves to discriminate between the various metamorphic sub zones. The identification of the metamorphic grades of the volcanic sequences in greenstone belts with SWIR spectroscopy is useful for regional geological field studies, exploration for metamorphic mineral deposits hosted in the greenstone belts and the interpretation of hyperspectral remote sensing data sets covering similar types of terranes.

  9. Decompressional metamorphic P-T paths from kyanite-sillimanite-andalusite bearing rocks in north-central New Mexico

    SciTech Connect

    Daniel, C.G.; Thompson, A.G.; Grambling, J.A. . Dept. of Earth and Planetary Sciences)

    1992-01-01

    Proterozoic rocks in six uplifts in northern and central New mexico display decompressional metamorphic P-T paths, apparently, related to crustal extension at a time near 1,440 Ma. Metamorphic P-T paths from the Picuris, Rincon, Truchas, Rio Mora, Sandia and southern Manzano Mountains are constrained by three independent techniques: (1) Al[sub 2]SiO[sub 5] and other mineral parageneses; (2) the Gibbs method applied to compositional zoning in garnet and plagioclase; and (3) a new technique based upon Fe[sup 3+] and Mn[sup 3+] zoning in andalusite. Aluminum silicate textures suggest that kyanite and subsequent sillimanite (commonly aligned parallel to the regional foliation and lineation) are earlier than andalusite, which overprints foliation. The decompressional P-T paths are interpreted to reflect crustal extension. Contact metamorphic aureoles associated with the Priest pluton in the southern Manzano and the Sandia Granite in the Sandia Mountains place constraints upon the timing of the Ky-Sil-And metamorphism. In the southern Manzano Mountains metamorphic isograds marking the first appearance of staurolite and (closer to the pluton) sillimanite are parallel to the margin of the 1,440 Ma Priest quartz monzonite pluton. Similarly, isograds also surround the NW margin of the 1,420 Ma Sandia pluton. The regional metamorphism appears to have coincided with and to have been enhanced by the emplacement of the plutons. Because plutonism and regional metamorphism appear to have been synchronous, pluton emplacement occurred during decompression.

  10. Removing the effects of metamorphism from the Neoproterozoic carbon isotope record: a case study on Islay, western Scotland

    NASA Astrophysics Data System (ADS)

    Skelton, Alasdair

    2016-04-01

    The Port Askaig Formation on Islay, western Scotland is the first discovered tillite (glacial sediment) of Neoproterozoic age. This formation is sandwiched between carbonate rocks which preserve an extreme negative carbon isotope excursion. This so called "Islay anomaly" has been correlated with other such anomalies worldwide and together with the tillites has been cited as evidence of major (worldwide) glaciation events. During subsequent mountain building, this carbonate-tillite- carbonate sequence has been folded, producing a major en-echelon anticlinal fold system. Folding was accompanied by metamorphism at greenschist facies conditions which was, in turn, accompanied by metamorphic fluid flow. Mapping of the δ18O and δ13C values of these carbonate rocks reveals that metamorphic fluids were channelled through the axial region of the anticlinal fold. The metamorphic fluid was found to have a highly negative δ13C value, which was found to be in equilibrium with metamorphosed graphitic mudstones beneath the carbonate-tillite-carbonate sequence. Devolatilisation of these mudstones is therefore a likely source of this metamorphic fluid. Removal of the effects of metamorphic fluid flow on δ13C values recorded by metamorphosed carbonate rocks on Islay allows us to re-evaluate the isotopic evidence used to reconstruct Neoproterozoic climate. We are able to show that extreme negative δ13C values can partly be attributed to metamorphic fluid flow.

  11. Short-Wavelength Infrared (SWIR) spectroscopy of low-grade metamorphic volcanic rocks of the Pilbara Craton

    NASA Astrophysics Data System (ADS)

    Abweny, Mohammad S.; van Ruitenbeek, Frank J. A.; de Smeth, Boudewijn; Woldai, Tsehaie; van der Meer, Freek D.; Cudahy, Thomas; Zegers, Tanja; Blom, Jan-Kees; Thuss, Barbara

    2016-05-01

    This paper shows the results of Short-Wavelength Infrared (SWIR) spectroscopy investigations of volcanic rocks sampled from low-grade metamorphic greenstone belts of the Archean Pilbara Craton in Western Australia. From the reflectance spectra a range of spectrally active minerals were identified, including chlorites, hornblende, actinolite, epidote and white micas. The rock samples were grouped into mineral assemblages based on their spectrally identified minerals and stratigraphic positions. The metamorphic amphibolite and greenschist facies could be identified from the SWIR spectroscopic data as well as three sub zones of the greenschist facies: 1) a zone containing Fe-chlorite; 2) a zone containing intermediate chlorite and epidote; and 3) a zone containing intermediate chlorite, actinolite and hornblende. Spectral parameters were calculated from the reflectance spectra to assess the metamorphic grade and zones. Plots of the depth parameters of the Fe-OH feature near 2250 nm versus the Mg-OH feature near 2390 nm differentiate the metamorphic amphibolite and greenschist facies and a transition zone between the two. The wavelength position parameter of the Mg-OH absorption feature near 2340 nm also serves to discriminate between the various metamorphic sub zones. The identification of the metamorphic grades of the volcanic sequences in greenstone belts with SWIR spectroscopy is useful for regional geological field studies, exploration for metamorphic mineral deposits hosted in the greenstone belts and the interpretation of hyperspectral remote sensing data sets covering similar types of terranes.

  12. Petrology, geochemistry, and metamorphic evolution of meta-sedimentary rocks in the Diancang Shan-Ailao Shan metamorphic complex, Southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Liu, Fulai; Liu, Pinghua; Shi, Jianrong; Cai, Jia

    2016-07-01

    Meta-sedimentary rocks are widely distributed within the Diancang Shan-Ailao Shan metamorphic complex in the Southeastern Tibetan Plateau. Detailed geochemical analyses show that all of them have similar geochemical features. They are enriched in light rare-earth elements (LREEs) and depleted in heavy rare-earth elements (HREEs), with moderately negative Eu anomalies (Eu/Eu∗ = 0.55-0.75). Major and trace element compositions for the meta-sedimentary rocks suggest that the protoliths were probably claystone, siltstone, and greywacke and deposited in an active continental margin. Garnet porphyroblasts in meta-sedimentary rocks have distinct compositional zonation from core to rim. The zonation of garnet in St-Ky-Grt-Bt-Ms schist indicates an increasing P-T trend during garnet growth. In contrast, garnets from (Sil)-Grt-Bt paragneiss show diffusion zoning, implying a decreasing P-T trend. Based on mineral transformations and P-T estimates using conventional geothermobarometers and pseudosection calculations, four metamorphic stages have been determined, including an early prograde metamorphic stage (M1), a peak amphibolite-granulite facies metamorphic stage (M2), a near-isothermal decompression stage (M3), and a late amphibolites-facies retrograde stage (M4). The relic assemblage of Ms + St ± Ky ± Bt ± Kfs + Qz preserved as inclusions in garnet porphyroblasts of the meta-sedimentary rocks belongs to prograde (M1) stage and records P-T conditions of 560-590 °C and 5.5-6.3 kb. Matrix mineral assemblages of Grt + Bt + Ky/Sil + Pl + Qz and Grt + Bt ± Sil + Pl ± Kfs + Qz formed at peak (M2) stage yield P-T conditions of 720-760 °C and 8.0-9.3 kb. M3 is characterized by decompression reactions, dehydration melting of assemblages that include hydrous minerals (e.g., biotite), and partial melting of felsic minerals. The retrograde assemblages is Grt + Bt + Sil + Pl + Qz formed at 650-760 °C and 5.0-7.3 kb. At the amphibolites-facies retrograde (M4) stage, fine

  13. Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P-T paths and timing of metamorphism of deep-seated garnet-mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

    NASA Astrophysics Data System (ADS)

    Hyppolito, T.; García-Casco, A.; Juliani, C.; Meira, V. T.; Hall, C.

    2014-10-01

    In this study, the Paleozoic albite-epidote-amphibolite occurring as meter-sized intercalations within garnet-mica schist at Punta Sirena beach (Pichilemu region, central Chile) is characterized for the first time. These rocks constitute an unusual exposure of subduction-related rocks within the Paleozoic Coastal Accretionary Complex of central Chile. Whereas high pressure (HP) greenschist and cofacial metasediments are the predominant rocks forming the regional metamorphic basement, the garnet-mica schist and amphibolite yield higher P-T conditions (albite-epidote amphibolite facies) and an older metamorphic age. Combining detailed mineral chemistry and textural information, P-T calculations and Ar-Ar ages, including previously published material from the Paleozoic Accretionary Complex of central Chile, we show that the garnet-mica schist and associated amphibolite (locally retrograded to greenschist) are vestiges of the earliest subducted material now forming exotic bodies within the younger HP units of the paleo-accretionary wedge. These rocks are interpreted as having been formed during the onset of subduction at the southwestern margin of Gondwana. However, we show that the garnet-mica schist formed at a slightly greater depth (ca. 40 km) than the amphibolite (ca. 30 km) along the same hot-subduction gradient developed during the onset of subduction. Both lithotypes reached their peak-P conditions at ca. 335-330 Ma and underwent near-isobaric cooling followed by cooling and decompression (i.e., counterclockwise P-T paths). The forced return flow of the garnet-mica schist from the subduction channel started at ca. 320 Ma and triggered the exhumation of fragments of shallower accreted oceanic crust (amphibolite). Cores of phengite (garnet-mica schist) and amphibole (amphibolite) grains have similar chemical compositions in both the S1 and S2 domains, indicating rotation of these grains during the transposition of the burial-related (prograde peak-T) foliation S1

  14. Coevolution of the Ile1,016 and Cys1,534 Mutations in the Voltage Gated Sodium Channel Gene of Aedes aegypti in Mexico

    PubMed Central

    Vera-Maloof, Farah Z.; Saavedra-Rodriguez, Karla; Elizondo-Quiroga, Armando E.; Lozano-Fuentes, Saul; Black IV, William C.

    2015-01-01

    Background Worldwide the mosquito Aedes aegypti (L.) is the principal urban vector of dengue viruses. Currently 2.5 billion people are at risk for infection and reduction of Ae. aegypti populations is the most effective means to reduce the risk of transmission. Pyrethroids are used extensively for adult mosquito control, especially during dengue outbreaks. Pyrethroids promote activation and prolong the activation of the voltage gated sodium channel protein (VGSC) by interacting with two distinct pyrethroid receptor sites [1], formed by the interfaces of the transmembrane helix subunit 6 (S6) of domains II and III. Mutations of S6 in domains II and III synergize so that double mutants have higher pyrethroid resistance than mutants in either domain alone. Computer models predict an allosteric interaction between mutations in the two domains. In Ae. aegypti, a Ile1,016 mutation in the S6 of domain II was discovered in 2006 and found to be associated with pyrethroid resistance in field populations in Mexico. In 2010 a second mutation, Cys1,534 in the S6 of domain III was discovered and also found to be associated with pyrethroid resistance and correlated with the frequency of Ile1,016. Methodology/Principal Findings A linkage disequilibrium analysis was performed on Ile1,016 and Cys1,534 in Ae. aegypti collected in Mexico from 2000–2012 to test for statistical associations between S6 in domains II and III in natural populations. We estimated the frequency of the four dilocus haplotypes in 1,016 and 1,534: Val1,016/Phe1,534 (susceptible), Val1,016/Cys1,534, Ile1,016/Phe1,534, and Ile1,016/Cys1,534 (resistant). The susceptible Val1,016/Phe1,534 haplotype went from near fixation to extinction and the resistant Ile1,016/Cys1,534 haplotype increased in all collections from a frequency close to zero to frequencies ranging from 0.5–0.9. The Val1,016/Cys1,534 haplotype increased in all collections until 2008 after which it began to decline as Ile1,016/Cys1,534 increased

  15. Contact metamorphism surrounding the Alta stock: Finite element model simulation of heat- and {sup 18}O/{sup 16}O mass-transport during prograde metamorphism

    SciTech Connect

    Cook, S.J.; Bowman, J.R.; Forster, C.B.

    1997-01-01

    Results of calcite-dolomite geothermometry and oxygen isotope studies of marbles in the southern portion of the contact aureole surrounding the Alta stock (Utah) provide evidence for extensive hydrothermal metamorphism in this part of the aureole. Simulation of these two independent data sets with two-dimensional, finite element fluid flow and heat transport models constrains the pattern of fluid flow, minimum permeability, and the permeability structure in this part of the aureole. Model results demonstrate that intrusion of the stock into a homogeneous, isotropic permeability medium yields peak metamorphic temperatures significantly lower than those measured in the marbles and significant {sup 18}O depletions both above and below the Alta-Grizzly thrust system. The latter contradicts the observations in the south aureole that {sup 18}O depletions in the marbles are restricted to marbles below the Alta-Grizzly thrust; dolomitic marbles above the thrust retain original sedimentary values up to the intrusive contact. Models with horizontal permeability barriers above the Alta-Grizzly thrust and extending over the top of the Alta stock are capable of reproducing the observed thermal and {delta}{sup 18}O profiles in the southern aureole. The presence of such horizontal barriers reduces the predominantly vertical fluid flow and heat transfer that would occur in a homogeneous and isotropic permeability medium, forcing fluid flow and heat transfer laterally away from the upper flanks of the stock. Such horizontal flow patterns are necessary to produce significant {sup 18}O depletion above the thrust, and to provide the necessary lateral heat transfer to duplicate the observed temperature profile. Best fit model results to the observed thermal and {delta}{sup 18}O profiles provide several new insights into the dynamics of fluid circulation and hydrogeologic characteristics of the southern Alta aureole during prograde metamorphism.

  16. Metamorphic and tectonic evolution of the Greater Himalayan Crystalline Complex in Nyalam region, south Tibet

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Min; Zhang, Jin-Jiang; Rubatto, Daniela

    2016-04-01

    Recent studies evoke dispute whether the Himalayan metamorphic core - Greater Himalayan Crystalline Complex (GHC) - was exhumed as a lateral crustal flow or a critical taper wedge during the India-Asia collision. This contribution investigated the evolution of the GHC in the Nyalam region, south Tibet, with comprehensive studies on structural kinematics, metamorphic petrology and geochronology. The GHC in the Nyalam region can be divided into the lower and upper GHC. Phase equilibria modelling and conventional thermobarometric results show that peak temperature conditions are lower in the lower GHC (~660-700°C) and higher in the upper GHC (~740-780°C), whereas corresponding pressure conditions at peak-T decrease from ~9-13 kbar to ~4 kbar northward. Monazite, zircon and rutile U-Pb dating results reveal two distinct blocks within the GHC of the Nyalam region. The upper GHC underwent higher degree of partial melting (15-25%, via muscovite dehydration melting) that initiated at ~32 Ma, peaked at ~29 Ma to 25 Ma, possibly ended at ~20 Ma. The lower GHC underwent lower degree of melting (0-10%) that lasted from 19 to 16 Ma, which was produced mainly via H2O-saturated melting. At different times, both the upper and lower blocks underwent initial slow cooling (35 ± 8 and 10 ± 5°C/Myr, respectively) and subsequent rapid cooling (120 ± 40°C/Myr). The established timescale of metamorphism suggests that high-temperature metamorphism within the GHC lasted a long duration (~15 Myr), whereas duration of partial melting lasted for ~3 Myr in the lower GHC and lasted for 7-12 Myr in the upper GHC. The documented diachronous metamorphism and discontinuity of peak P-T conditions implies the presence of the Nyalam Thrust in the study area. This thrust is probably connected to the other thrusts in Nepal and Sikkim Himalaya, which extends over ~800 km and is named the "High Himalayan Thrust". Timing of activity along this thrust is at ~25-16 Ma, which is coeval with active

  17. Regional metamorphism in the Condrey Mountain Quadrangle, north-central Klamath Mountains, California

    USGS Publications Warehouse

    Hotz, Preston Enslow

    1979-01-01

    A subcircular area of about 650 km 2 in northern California and southwestern Oregon is occupied by rocks of the greenschist metamorphic facies called the Condrey Mountain Schist. This greenschist terrane is bordered on the east and west by rocks belonging to the amphibolite metamorphic facies that structurally overlie and are thrust over the Condrey Mountain Schist. The amphibolite facies is succeeded upward by metavolcanic and metasedimentary rocks belonging to the greenschist metamorphic facies. The Condrey Mountain Schist is composed predominantly of quartz-muscovite schist and lesser amounts of actinolite-chlorite schist formed by the metamorphism of graywacke and spilitic volcanic rocks that may have belonged to the Galice Formation of Late Jurassic age. Potassium-argon age determinations of 141?4 m.y. and 155?5 m.y. obtained on these metamorphic rocks seem to be incompatible with the Late Jurassic age usually assigned the Galice. The rocks that border the amphibolite facies are part of an extensive terrane of metavolcanic and metasedimentary rocks belonging to the western Paleozoic and Triassic belt. The metavolcanic rocks include some unmetamorphosed spilite but are mostly of the greenschist metamorphic facies composed of oligoclase (An15-20) and actinolite with subordinate amounts of chlorite and clinozoisiteepidote. The interbedded sedimentary rocks are predominantly argillite and slaty argillite, less commonly siliceous argillite and chert, and a few lenticular beds of marble. On the south, high-angle faults and a tabular granitic pluton separate the greenschist metavolcanic terrane from the amphibolite facies rocks; on the east, nonfoliated amphibolite is succeeded upward, apparently conformably, by metasedimentary rocks belonging to the greenschist metavolcanic terrane. In the southern part of Condrey Mountain quadrangle, an outlier of a thrust plate composed of the Stuart Fork Formation overlies the metavolcanic and metasedimentary rocks. The Stuart

  18. The origin of high δ18O zircons: marbles, megacrysts, and metamorphism

    NASA Astrophysics Data System (ADS)

    Cavosie, Aaron J.; Valley, John W.; Kita, Noriko T.; Spicuzza, Michael J.; Ushikubo, Takayuki; Wilde, Simon A.

    2011-11-01

    The oxygen isotope ratios (δ18O) of most igneous zircons range from 5 to 8‰, with 99% of published values from 1345 rocks below 10‰. Metamorphic zircons from quartzite, metapelite, metabasite, and eclogite record δ18O values from 5 to 17‰, with 99% below 15‰. However, zircons with anomalously high δ18O, up to 23‰, have been reported in detrital suites; source rocks for these unusual zircons have not been identified. We report data for zircons from Sri Lanka and Myanmar that constrain a metamorphic petrogenesis for anomalously high δ18O in zircon. A suite of 28 large detrital zircon megacrysts from Mogok (Myanmar) analyzed by laser fluorination yields δ18O from 9.4 to 25.5‰. The U-Pb standard, CZ3, a large detrital zircon megacryst from Sri Lanka, yields δ18O = 15.4 ± 0.1‰ (2 SE) by ion microprobe. A euhedral unzoned zircon in a thin section of Sri Lanka granulite facies calcite marble yields δ18O = 19.4‰ by ion microprobe and confirms a metamorphic petrogenesis of zircon in marble. Small oxygen isotope fractionations between zircon and most minerals require a high δ18O source for the high δ18O zircons. Predicted equilibrium values of Δ18O(calcite-zircon) = 2-3‰ from 800 to 600°C show that metamorphic zircon crystallizing in a high δ18O marble will have high δ18O. The high δ18O zircons (>15‰) from both Sri Lanka and Mogok overlap the values of primary marine carbonates, and marbles are known detrital gemstone sources in both localities. The high δ18O zircons are thus metamorphic; the 15-25‰ zircon values are consistent with a marble origin in a rock-dominated system (i.e., low fluid(external)/rock); the lower δ18O zircon values (9-15‰) are consistent with an origin in an external fluid-dominated system, such as skarn derived from marble, although many non-metasomatized marbles also fall in this range of δ18O. High δ18O (>15‰) and the absence of zoning can thus be used as a tracer to identify a marble source for high δ18O

  19. The relationship between continental collision process and metamorphic pattern in the Himalayan collision belts

    NASA Astrophysics Data System (ADS)

    Oh, Chang-Whan

    2015-04-01

    Both UHP and HP eclogites are reported from the Kaghan Valley and Tso Morari Massif in the western part of the Himalayan collision belt (Ghazanfar and Chaudhry, 1987; Thakur, 1983). UHP eclogites in the Kaghan record peak metamorphic conditions of 770 °C and 30 kbar (O'Brien et al., 2001) and was retrograded into the epidote-amphibolite or blueschist (580-610 °C, 10-13 kbar; Lombardo and Rolfo, 2000). Sensitive high-resolution ion microprobe dating of zircon reveals that the UHP eclogite formed at ca. 46 Ma (Kaneko et al., 2003; Parrish et al., 2006). The Tso Morari UHP eclogite had formed at 750 °C, > 39 kbar (Mukheerjee et al., 2003; Bundy, 1980) and underwent amphibolite facies retro-grade metamorphism (580 °C, 11 kbar) during uplift (Guillot et al., 2008). Peak metamorphism of the Tso Morari Massif was dated at ca. 53-55 Ma (Leech et al., 2005). Only HP eclogites have been reported from the mid-eastern part of the Himalayan collision belt (Lombardo and Rolfo, 2000; Corrie et al., 2010). The HP eclogite in the mid-eastern part may have formed at ca. > 780 °C and 20 kbar and was overprinted by high-pressure granulite facies metamorphism (780-750°C, 12-10 kbar) at ca. 30 Ma (Groppo et al. 2007; Corrie et al., 2010). HP granulite (890 °C, 17-18 kbar) is reported from the NBS, at the eastern terminus of the Himalayan collision belt; the granulite was subjected to retrograde metamorphism to produce lower-pressure granulite (875-850°C, 10-5 kbar), representing near-isothermal decompression (Liu and Zhong, 1997). The HP granulite metamorphism may have occurred at ca. 22-25 Ma. Along the Himalayan collision belt, peak metamorphism changes eastward from UHP eclogite facies through HP eclogite facies to high-pressure granulite facies, indicating a progressive eastwards decrease in the depth of subduction of continental crust and an eastwards increase in the geothermal gradient. The peak metamorphic ages also decrease from 53-46 Ma in the west to 22-25 Ma in the

  20. The Palu Metamorphic Complex, NW Sulawesi, Indonesia: Origin and evolution of a young metamorphic terrane with links to Gondwana and Sundaland

    NASA Astrophysics Data System (ADS)

    van Leeuwen, Theo; Allen, Charlotte M.; Elburg, Marlina; Massonne, Hans-Joachim; Palin, J. Michael; Hennig, Juliane

    2016-01-01

    The Palu Metamorphic Complex (PMC) is exposed in a late Cenozoic orogenic belt in NW Sulawesi, Indonesia. It is a composite terrane comprising a gneiss unit of Gondwana origin, a schist unit composed of meta-sediments deposited along the SE Sundaland margin in the Late Cretaceous and Early Tertiary, and one or more slivers of amphibolite with oceanic crust characteristics. The gneiss unit forms part of the West Sulawesi block underlying the northern and central sections of the Western Sulawesi Province. The presence of Late Triassic granitoids and recycled Proterozoic zircons in this unit combined with its isotopic signature suggests that the West Sulawesi block has its origin in the New Guinea margin from which it rifted in the late Mesozoic. It docked with Sundaland sometime during the Late Cretaceous. U-Th-Pb dating results for monazite suggest that another continental fragment may have collided with the Sundaland margin in the earliest Miocene. High-pressure (HP) and ultrahigh-pressure (UHP) rocks (granulite, peridotite, eclogite) are found as tectonic slices within the PMC, mostly along the Palu-Koro Fault Zone, a major strike-slip fault that cuts the complex. Mineralogical and textural features suggest that some of these rocks resided at depths of 60-120 km during a part of their histories. Thermochronological data (U-Th-Pb zircon and 40Ar/39Ar) from the metamorphic rocks indicate a latest Miocene to mid-Pliocene metamorphic event, which was accompanied by widespread granitoid magmatism and took place in an extensional tectonic setting. It caused recrystallization of, and new overgrowths on, pre-existing zircon crystals, and produced andalusite-cordierite-sillimanite-staurolite assemblages in pelitic protoliths, indicating HT-LP (Buchan-type) metamorphism. The PMC was exhumed as a core complex at moderate rates (c. 0.7-1.0 mm/yr) accompanied by rapid cooling in the Plio-Pleistocene. Some of the UHP rocks were transported to the surface at significantly higher

  1. Prostate cancer risk from occupational exposure to polycyclic aromatic hydrocarbons interacting with the GSTP1 Ile105Val polymorphism

    PubMed Central

    Rybicki, Benjamin A.; Neslund-Dudas, Christine; Nock, Nora L.; Schultz, Lonni R.; Eklund, Ludmila; Rosbolt, James; Bock, Cathryn H.; Monaghan, Kristin G.

    2006-01-01

    Condensed Abstract Men who carry the GSTP1 Val105 variant who are exposed at high levels to occupational PAH are at increased risk for prostate cancer. This increased risk is more pronounced in men under age 60 or with a family history of prostate cancer. Background Variation in the glutathione S-transferase (GSTP1) gene and occupational polycyclic aromatic hydrocarbons (PAH) exposure are putative prostate cancer risk factors. An Ile/Val polymorphism in codon 105 of GSTP1 affects its enzymatic activity toward PAH detoxification, a possible mechanism in prostate carcinogenesis. Methods To determine whether the GSTP1 Ile105Val polymorphism modifies prostate cancer risk associated with occupational PAH exposure, we studied 637 prostate cancer cases and 244 controls of White and African-American race from the Henry Ford Health System in Detroit, Michigan. Occupational exposure to PAH from wood, petroleum, coal or other sources through respiratory and cutaneous routes was retrospectively assessed by expert review of job histories. The association of occupational PAH exposure and GSTP1 Ile105Val polymorphism with prostate cancer was tested in multiple logistic regression models adjusting for potential confounders. Cases were over sampled compared with controls to evaluate gene-environment interaction with the statistically efficient case-only analytic approach. Results Neither carriage of the GSTP1 Val105 variant allele nor occupational PAH exposure was significantly associated with prostate cancer. However, case-only analyses revealed that carriage of the GSTP1 Val105 variant allele was associated with increasing levels of occupational respiratory PAH exposures from any source and from petroleum (trend test p-value = 0.01 for both). The GSTP1 Val105 allele was observed most frequently in cases in the highest quartile of occupational respiratory PAH exposures from petroleum (OR=1.74; 95% CI = 1.11–2.72) or from any source (OR=1.85; 95% CI = 1.19–2.89). The gene

  2. Ion-microprobe dating of zircon from quartz-graphite veins at the Bristol, New Hampshire, metamorphic hot spot

    SciTech Connect

    Zeitler, P.K. ); Barreiro, B.; Chamberlain, C.P. ); Rumble, D. III )

    1990-07-01

    Detrital zircons entrained in hydrothermal quartz-graphite-rutile veins found near the Bristol, New Hampshire, metamorphic hot spot are overgrown by thin rims. Ion-microprobe analyses of these rims date their growth at 408 {plus minus} 6 Ma. These measurements quantitatively confirm textural evidence that the graphite veins were emplaced during peak metamorphism associated with the Acadian orogeny, and they provide a direct positive test of the hypothesis, based on petrological and stable-isotope evidence, that the hydrothermal systems responsible for the quartz-graphite veins were also responsible for the hot-spot metamorphism.

  3. Structure and thermochronology of the metamorphic core of the Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Toro, Jaime

    1999-11-01

    Detailed field studies were undertaken in two key areas of the Central Belt of the Brooks Range: (1) the north flank of Mt. Igikpak in the Survey Pass Quadrangle and (2) in the Shishakshinovik Pass area in the eastern Ambler River Quadrangle. In both areas structural, stratigraphic, petrologic, 40Ar/39Ar, apatite fission-track and U-Pb data were used to constrain the kinematic and thermal history of metamorphic rocks of those areas. North of the Mt. Igikpak massif a crustal section ˜15 km thick is exposed. There are upper greenschist facies rocks in the deeper portions, and very low grade metamorphic rocks at higher structural levels. Two foliations are found: a higher grade relict S1 fabric and a lower grade S 2 fabric that controls the metamorphic layering. 40Ar/ 39Ar analyses from S1 white mica in the low-grade rocks at the northern end of the transect indicate that peak M1 metamorphism occurred before ˜112 Ma. We ascribe M1 to shortening that occurred during collision of an island arc against the Arctic Alaska margin. S 2 involved the retrogression of earlier assemblages. Kinematic indicators on S2 are top-to-the-north. A rapid cooling event from 500 +/- 50°C to 300 +/- 50°C took place between ˜98 and ˜90 Ma. The driving mechanism for ductile deformation during S2, and for rapid cooling documented by our thermochronologic data, was probably the gravitational collapse of the core of the orogen, over-thickened during the preceding collision. At Shishakshinovik Pass there are Mississippian Lisburne Group strata surrounded by metamorphic rocks typical of the Central Belt of the Brooks Range. All the rocks at Shishakshinovik Pass are intensely deformed, so that one cannot distinguish between an autochthonous and an allochthonous sequence. Furthermore the Mississippian rocks, instead of being attached to the underlying basement, are in the hanging wall of a northwest dipping shear zone. Based on the variations in metamorphic grade and the 40Ar/ 39Ar

  4. Metamorphism and gold mineralization of the Kenticha Katawicha area: Adola belt, southern Ethiopia

    NASA Astrophysics Data System (ADS)

    Tsige, Lulu

    2006-05-01

    I present geological and mineral chemistry results aiming at understanding the relationship between metamorphism and gold mineralization in the N-trending Neoproterozoic Kenticha-Katawicha area in the Adola belt of southern Ethiopia. The Kenticha-Katawicha area comprises low-grade metamorphic rocks including pelitic schists, marble, graphite schists and Fe-Mn quartzites (Kenticha marine metasedimentary rocks) and serpentinites and talc-tremolite-chlorite schists with podiform chromites (Kenticha ophiolite). Lenses of high-grade amphibolite schist are also locally present within the Kenticha-Katawicha area. These rocks are sandwiched between high-grade para- and ortho-gneisses, migmatites, schists and amphibolites. Post-orogenic granites intrude the metamorphic sequences. Mineral assemblages and textural data obtained from the high-grade rocks indicate that the dominant metamorphic condition is of upper amphibolite facies. Garnet-biotite (garnet-core-matrix-biotite) and amphibole-plagioclase geothermometry gave estimates for peak metamorphic temperatures of 630-650 °C and pressure of 7 kbar for the high-grade rocks. On the other hand, the low-grade rocks recrystallized in the greenschist facies conditions. The estimated peak T- P values for the high-grade rocks suggest a burial to ˜25 km depth and a clockwise P- T path is deduced from mineral thermometry and the textural and paragenetic relations. This combined with the geochemistry of the magmatic rocks and clockwise P- T is consistent with a collision setting in which rocks of the calc-alkaline, volcanic-arc, and oceanic fragments are assembled. In the study area, gold occurs in quartz veins and veinlets in lenses of biotite schists within ultramafic rocks that are confined to shear zones. Fluid inclusion studies of gold quartz veins and veinlets indicate a H 2O- and CO 2-rich fluid with low salinity (<5 wt% NaCl equivalent). The gold mineralization in the area is post-peak regional metamorphism and is

  5. UHT granulite-facies metamorphism in Rogaland, S Norway, is polyphase in nature

    NASA Astrophysics Data System (ADS)

    Laurent, Antonin; Duchene, Stéphanie; Bingen, Bernard; Seydoux-Guillaume, Anne-Magali; Bosse, Valérie

    2016-04-01

    Propensity of metamorphic assemblages to remain metastable after melt extraction complicates singularly the petrologist's task to discriminate between a single granulite-facies P-T path and a polyphase one. Using an integrated petrological and in-situ geochronological approach in key rock-samples, we reconstruct the pressure-temperature-time path of Sveconorwegian metamorphism across a 30 km-wide metamorphic gradient ranging from upper amphibolite facies to ultra-high temperature (UHT) granulite-facies in Rogaland, S. Norway. Thermodynamic modelling of phase equilibria in the Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-Ti2O-O2 chemical system (PerpleX code) are carried out with an emphasis on moderately oxidized, spinel-bearing assemblages resulting from either garnet or sapphirine breakdown. Geochronological U-(Th)-Pb data acquired on both monazite (LA-ICP-MS) and zircon (SIMS) are complemented by minor- and trace-elements signatures of both minerals, to monitor REE distribution through time and to evaluate garnet apparition or demise. Coupling field, petrological and geochronological data lead to a polyphase metamorphic history, lasting about 100 My. The onset of regional granulite facies metamorphism at 1035 Ma is associated with the emplacement of large volumes of granitic magmas in the amphibolite to granulite facies transition zone. In the deeper part of the crustal section, localized sapphirine-bearing restitic lithologies testify to UHT temperatures (900‑920 °C). These conditions were reached at ca. 1010 Ma following a tight clockwise P-T path associated with minor exhumation (7 to 5.5 kbar) and subsequent cooling to 700 °C. A distinct thermal episode, initiated at ca. 950 Ma, reached UHT granulite-facies conditions with the intrusion of massif-type anorthosite plutons at ca. 930 Ma producing a 5-km wide aureole. The aureole is delimited by the presence of osumilite in high Fe-Al rocks yielding quantitative estimates of 900-950 °C at a maximum pressure of 5

  6. RuBPCase activase mediates growth-defense tradeoffs: Silencing RCA redirects JA flux from JA-Ile to MeJA to attenuate induced defense responses in Nicotiana attenuata

    PubMed Central

    Mitra, Sirsha; Baldwin, Ian T.

    2014-01-01

    Summary RuBPCase activase (RCA), an abundant photosynthetic protein is strongly down-regulated in response to Manduca sexta’s oral secretion (OS) in Nicotiana attenuata. RCA-silenced plants are impaired not only in photosynthetic capacity and growth, but also in jasmonic acid (JA)-isoleucine (Ile) signaling, and herbivore resistance mediated by JA-Ile dependent defense traits. These responses are consistent with a resource-based growth-defense trade-off. Since JA+Ile-supplementation of OS restored WT levels of JA-Ile, defenses and resistance to M. sexta, but OS supplemented individually with JA- or Ile did not, the JA-Ile deficiency of RCA-silenced plants could not be attributed to lower JA or Ile pools or JAR4/6 conjugating activity. Similar levels of JA-Ile derivatives after OS elicitation indicated unaltered JA-Ile turnover and lower levels of other JA-conjugates ruled out competition from other conjugation reactions. RCA-silenced plants accumulated more methyl jasmonate (MeJA) after OS elicitation, which corresponded with increased jasmonate methyltransferase (JMT) activity. RCA-silencing phenocopies JMT over-expression, wherein elevated JMT activity redirects OS-elicited JA flux towards inactive MeJA, creating a JA sink which depletes JA-Ile and its associated defense responses. Hence RCA plays an additional non-photosynthetic role in attenuating JA-mediated defenses and their associated costs potentially allowing plants to anticipate resource-based constraints on growth before they actually occur. PMID:24491116

  7. Front-end of the ILE Project: A design study for a 100 mJ sub-10 fs laser

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Dimitris N.; Ramirez, Patricia; Pellegrina, Alain; Druon, Frédéric; Georges, Patrick; Chen, Xiaowei; Canova, Lorenzo; Malvache, Arnaud; Jullien, Aurélie; Lopez-Martens, Rodrigo

    2010-04-01

    Within the development of the ILE French project aiming on the building of a 10 PW, 150 J/15 fs laser chain (named APOLLON), a design study for a sub-10-fs, 100 mJ pilot laser operating at 800 nm have been conceived. This system is based on a non-collinear optical parametric chirped-pulse amplification (NOPCPA) of the spectrally broadened and compressed pulses of a Ti:Sapphire laser system providing 1.5-mJ, 25-fs, pumped at 515 nm by a high-energy diode-pumped Yb-doped-based laser chain. The envisioned system, based on a novel combined architecture of picosecond and nanosecond NOPCPA stages, will finally deliver carrier envelope phased (CEP) stabilized 1 ns pulses (compressible to less than 10 fs) at 800 nm with 100 mJ energy and at a repetition rate in the range of 10-100 Hz.

  8. Backbone and stereospecific (13)C methyl Ile (δ1), Leu and Val side-chain chemical shift assignments of Crc.

    PubMed

    Sharma, Rakhi; Sahu, Bhubanananda; Ray, Malay K; Deshmukh, Mandar V

    2015-04-01

    Carbon catabolite repression (CCR) allows bacteria to selectively assimilate a preferred compound among a mixture of several potential carbon sources, thus boosting growth and economizing the cost of adaptability to variable nutrients in the environment. The RNA-binding catabolite repression control (Crc) protein acts as a global post-transcriptional regulator of CCR in Pseudomonas species. Crc triggers repression by inhibiting the expression of genes involved in transport and catabolism of non-preferred substrates, thus indirectly favoring assimilation of preferred one. We report here a nearly complete backbone and stereospecific (13)C methyl side-chain chemical shift assignments of Ile (δ1), Leu and Val of Crc (~ 31 kDa) from Pseudomonas syringae Lz4W. PMID:24496608

  9. Computer simulations of the experiments at RAL, LULI, and PALS carried out under HiPER including those performed at ILE

    NASA Astrophysics Data System (ADS)

    Rhee, Yong-Joo

    2011-06-01

    Comparison of computer simulations applied to the experiments at RAL(UK), LULI(France), PALS(Czech Republic), and ILE(Japan) is given. Temporal evolution of densities, electron temperatures, compression/implosion velocities, are discussed using one dimensional hydrodynamic code (HYADES).

  10. A differentially conserved residue (Ile42) of GH42 β-galactosidase from Geobacillus stearothermophilus BgaB is involved in both catalysis and thermostability.

    PubMed

    Dong, Yi-Ning; Chen, Hai-Qin; Sun, Yan-Hui; Zhang, Hao; Chen, Wei

    2015-04-01

    The glycoside hydrolase family 42 (GH42) of thermophilic microorganisms consists of thermostable β-galactosidases that display significant variations in their temperature optima and stabilities. In this study, we compared the substrate binding modes of 2 GH42 β-galactosidases, BgaB from Geobacillus stearothermophilus and A4-β-Gal from Thermus thermophilus A4. The A4-β-Gal has a catalytic triad (Glu312-Arg32-Glu35) with an extended hydrogen bond network that has not been observed in BgaB. In this study, we performed site-saturation mutagenesis of Ile42 in BgaB (equivalent to Glu312 in A4-β-Gal) to study the effects of different residues on thermostability, catalytic function, and the extended hydrogen bond network. Our experimental results suggest that substitution of Ile42 with polar AA enhanced the thermostability but decreased the catalytic efficiency of BgaB. Polar AA substitution for Ile42 simultaneously affected thermostability, catalytic efficiency, and the hydrogen bond network, suggesting that Ile42 is responsible for functional discrimination between members of the GH42 family. These observations could lead to a novel strategy for investigating the functional evolution of the GH42 β-galactosidases. PMID:25682138

  11. Effect of herbicide resistance endowing Ile-1781-Leu and Asp-2078-Gly ACCase gene mutations on ACCase kinetics and growth traits in Lolium rigidum

    PubMed Central

    Vila-Aiub, Martin M.; Yu, Qin; Han, Heping; Powles, Stephen B.

    2015-01-01

    The rate of herbicide resistance evolution in plants depends on fitness traits endowed by alleles in both the presence and absence (resistance cost) of herbicide selection. The effect of two Lolium rigidum spontaneous homozygous target-site resistance-endowing mutations (Ile-1781-Leu, Asp-2078-Gly) on both ACCase activity and various plant growth traits have been investigated here. Relative growth rate (RGR) and components (net assimilation rate, leaf area ratio), resource allocation to different organs, and growth responses in competition with a wheat crop were assessed. Unlike plants carrying the Ile-1781-Leu resistance mutation, plants homozygous for the Asp-2078-Gly mutation exhibited a significantly lower RGR (30%), which translated into lower allocation of biomass to roots, shoots, and leaves, and poor responses to plant competition. Both the negligible and significant growth reductions associated, respectively, with the Ile-1781-Leu and Asp-2078-Gly resistance mutations correlated with their impact on ACCase activity. Whereas the Ile-1781-Leu mutation showed no pleiotropic effects on ACCase kinetics, the Asp-2078-Gly mutation led to a significant reduction in ACCase activity. The impaired growth traits are discussed in the context of resistance costs and the effects of each resistance allele on ACCase activity. Similar effects of these two particular ACCase mutations on the ACCase activity of Alopecurus myosuroides were also confirmed. PMID:26019257

  12. Geology, petrography, geochemistry, and genesis of sulfide-rich pods in the Lac des Iles palladium deposits, western Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Duran, Charley J.; Barnes, Sarah-Jane; Corkery, John T.

    2016-04-01

    The Lac des Iles Pd deposits are known for their Pd-rich sulfide-poor mineralization. However, previously undocumented sulfide-rich pods also occur within the intrusion that hosts the deposits. Given the complex magmatic and hydrothermal history of the mineralization at Lac des Iles, the sulfide-rich pods could have crystallized from magmatic sulfide liquids or precipitated from hydrothermal fluids. Sulfide-rich pods occur throughout the stratigraphy, in all rock types, and along comagmatic shear zones, and contain net-textured to massive sulfides. They can be divided into four main groups based on the variation in mineral assemblages: (1) pyrrhotite-pentlandite ± pyrite-chalcopyrite-magnetite-ilmenite; (2) chalcopyrite ± pyrrhotite-pentlandite-pyrite-magnetite-ilmenite; (3) pyrite ± pentlandite-chalcopyrite-pyrrhotite-magnetite-ilmenite; and (4) magnetite ± ilmenite-pyrrhotite-pentlandite-pyrite-chalcopyrite. Whole rock metal contents and S isotopic compositions do not change with the amount of pyrite present, except for slight enrichments in As and Bi. The presence of an essentially magmatic sulfide mineral assemblage (pyrrhotite-pentlandite ± chalcopyrite) with pentlandite exsolution flames in pyrrhotite in some pods suggests that the pods crystallized from magmatic sulfide liquids. The very low Cu contents of the pods suggests that they are mainly cumulates of monosulfide solid solution (MSS). We propose a model whereby sulfide liquids were concentrated into dilation zones prior to crystallizing cumulus MSS. Intermediate solid solution crystallized from the fractionated liquids at the edges of some pods leaving residual liquids enriched in Pt, Pd, Au, As, Bi, Sb, and Te. These residual liquids are no longer associated with the pods. During subsequent alteration, pyrite replaced MSS/pyrrhotite, but this did not affect the platinum-group element contents of the pods.

  13. Frequencies of the Arg16Gly, Gln27Glu and Thr164Ile Adrenoceptor β2 Polymorphisms among Omanis

    PubMed Central

    Al-Balushi, Khalid; Zadjali, Fahad; Al-Sinani, Sawsan; Al-Zadjali, Al-Muatasim; Bayoumi, Riad

    2015-01-01

    Objectives: This study aimed to assess the distribution of missense mutations in the adrenoceptor β2 (ADRB2) gene in an Omani cohort. Methods: This study was carried out between May 2014 and March 2015 at the Sultan Qaboos University, Muscat, Oman. Blood samples were taken from 316 unrelated Omani subjects. Genotyping for rs1042713 (c.46A>G, p.Arg16Gly), rs1042714 (c.79C>G, p.Gln27Glu) and rs1800888 (c.491C>T, p.Thr164Ile) polymorphisms was performed by real-time polymerase chain reaction using single nucleotide polymorphism (SNP) genotyping assays. The allelic frequencies of these polymorphisms were estimated on the basis of the observed numbers of specific alleles from the genotype data for male and female subjects. The genotype frequencies for each polymorphism were tested for deviation from the Hardy-Weinberg equilibrium. Results: Gly16 and Glu27 were the most frequent variants found among the cohort (63% and 75%, respectively). The Ile164 variant was not detected in the study population. There was a significant linkage disequilibrium between the rs1042713 and rs1042714 SNPs (r2 = 0.209; P ≤0.001). The most observed haplotypes were Gly16-Gln27 and Arg16-Gln27 (0.37 and 0.38, respectively). The frequency of Gly16-Glu27 was 0.25, comprising all Glu27 carriers. Conclusion: The allelic distribution of variants in this Omani cohort was similar to distributions reported among Caucasian populations. PMID:26629374

  14. Isotopic characterization of Polycyclic Aromatic Hydrocarbons for identification of sources and transfer mechanisms in Ile de France.

    NASA Astrophysics Data System (ADS)

    Fauches, Raphaël; Moreau-Guigon, Elodie; Alliot, Fabrice; Mendez, Mercedes; Chevreuil, Marc

    2015-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants that accumulate in the environment as mainly a result of human processes in anthropic environment. Emission of PAHs in Ile de France region is a major environmental and public health problem. Seventy percent of the Seine Watershed Rivers do not respect the requirement of the 2012 European Water Framework Directive for good chemical status due to PAHs. We study the 16 PAHs selected by the United States Environmental Protection Agency. The measurement of the ratio of stable Carbon (δ13C) and hydrogen (δ2H) isotopes may be used as a means to identify the source of PAHs. Two samplings campaign in the Seine watershed was conducted in summer and in winter during dry periods and one during rainy periods. Water and sediment were sampled from 12 locations along the Orge River (France) and classified in three categories: urban, peri-urban and rural. Extraction and purification methods have been developed and tested. This method consists on a liquid-liquid extraction and sonication extraction. The Aromatic fraction is purified and isolated on silica/alumina column before performing thin purification by using a semi-preparative High Performance Liquid Chromatography (HPLC). HPLC is used for separation of each PAH one by one. Moreover, this fractionation reduces background noise generated in part by unwanted compounds like alkanes and allows the isotopic analysis of PAH. The purity of each fraction was verified by Mass-Spectrometry Gas Chromatography in scan mode. The mean recovery of the method for all PAHs was around 80%. Isotopic analysis for carbon 13 and deuterium by Gas Chromatography-Combustion- Isotope-ratio mass spectrometry are ongoing. Beside the sampling campaign, biodegradation, hydrolysis and photolysis tests were performed. In addition, combustion testing of gasoline and diesel on an experimental device are provided to estimate the isotopic ratio of motorized vehicles in the Ile de France region.

  15. An inverted metamorphic field gradient in the central Brooks Range, Alaska and implications for exhumation of high-pressure/low-temperature metamorphic rocks

    USGS Publications Warehouse

    Patrick, B.; Till, A.B.; Dinklage, W.S.

    1994-01-01

    During exhumation of the Brooks Range internal zone, amphibolite-facies rocks were emplaced atop the blueschist/greenschist facies schist belt. The resultant inverted metamorphic field gradient is mappable as a series of isograds encountered as one traverses up structural section. Amphibolite-facies metamorphism occurred at ??? 110 Ma as determined from 40Ar 39Ar analysis of hornblende. This contrasts with 40Ar 39Ar phengite cooling ages from the uderlying schist belt, which are clearly older (by 17-22 m.y.). Fabrics in both the amphibolite-facies rocks and schist belt are characterized by repeated cycles of N-vergent crenulation and transposition that was likely associated with out-of-sequence ductile thrusting in the internal zone of the Brooks Range orogen. Contractional deformation occurred in an overall environment of foreland-directed tectonic transport, broadly synchronous with exhumation of the internal zone, and shortening within the thin-skinned fold and thrust belt. These data are inconsistent with a recently postulated mid-Cretaceous episode of lithospheric extension in northern Alaska. ?? 1994.

  16. Metamorphism during temperature gradient with undersaturated advective airflow in a snow sample

    NASA Astrophysics Data System (ADS)

    Ebner, Pirmin Philipp; Schneebeli, Martin; Steinfeld, Aldo

    2016-04-01

    Snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow, which alters its microstructure and physical properties. Time-lapse X-ray microtomography is applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions. Cold saturated air at the inlet was blown into the snow samples and warmed up while flowing across the sample with a temperature gradient of around 50 K m-1. Changes of the porous ice structure were observed at mid-height of the snow sample. Sublimation occurred due to the slight undersaturation of the incoming air into the warmer ice matrix. Diffusion of water vapor opposite to the direction of the temperature gradient counteracted the mass transport of advection. Therefore, the total net ice change was negligible leading to a constant porosity profile. However, the strong recrystallization of water molecules in snow may impact its isotopic or chemical content.

  17. The Kokchetav Massif, Kazakhstan: "Type locality" of diamond-bearing UHP metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Schertl, H.-P.; Sobolev, N. V.

    2013-02-01

    After the discovery of metamorphic coesite in crustal rocks from the Western Alps (Italy) and the Western gneiss region (Norway) in the mid 1980s of the last century, metamorphic diamond was observed only a few years later "in situ" in the Kokchetav Massif (Kazakhstan). Findings of such coesite- and diamond-bearing ultrahigh pressure metamorphic (UHP) rocks with protoliths formed or embedded in crustal levels and subsequently experienced PT-conditions within or even higher than the coesite stability field have dramatically changed our geodynamic view of orogenetic processes. These occurrences provide evidence that crustal rocks were subducted into mantle depths and exhumed to the surface. Recent studies even suggest continental subduction to depths exceeding 300 km. These rocks have been extensively studied and many new and important observations have been made. Thus far, more than 350 papers have been published on various aspects of Kokchetav UHP rocks. The Kokchetav Massif of northern Kazakhstan is part of one of the largest suture zones in Central Asia and contains slices of HP and UHP metamorphic rocks. Classical UHP rocks mainly occur in the Kumdy Kol, Barchi Kol and Kulet areas, and include a large variety of lithologies such as calcsilicate rocks, eclogite, gneisses, schists, marbles of various compositions, garnet-pyroxene-quartz rocks, and garnet peridotite. Most of them contain microdiamonds; some of which reach a grain size of 200 μm. Most diamond grains show cuboid shapes but in rare cases, diamonds within clinozoisite gneiss from Barchi Kol occur as octahhedral form. Microdiamonds contain highly potassic fluid inclusions, as well as solid inclusions like carbonates, silicates and metal sulfides, which favour the idea of diamond formation from a C-O-H bearing fluid. Nitrogen isotope data and negative δ13C values of Kokchetav diamonds indicate a metasedimentary origin. PT-estimates of Kokchetav UHP rocks yield peak metamorphic conditions of at least 43

  18. Degree of equilibration of eucritic pyroxenes and thermal metamorphism of the earliest planetary crust

    SciTech Connect

    Takeda, Hiroshi; Graham, A.L. Natural History Museum, London )

    1991-06-01

    The pyroxenes in two new monomict eucrites from Antarctica, Yamato 791186 and Yamato 792510, have been studied and compared with those of other Antarctic and non-Antarctic eucrites. The purpose of this study is to identify compositional and textural relationship shown by these pyroxenes which may be used as indicators of the thermal history of the meteorite. An attempt is made, using petrographic and compositional criteria, to distinguish between the initial cooling history and subsequent thermal events. It is suggested that it is possible to identify stages of thermal 'metamorphism' which may be used to indicate the conditions on the surface and crust of the parent body. A picture of the geological setting of the HED (Howardites, Eucrites, Diogenites) parent body is proposed, for which thermal metamorphism by impact heating is an important process. 22 refs.

  19. Ubiquitous interstellar diamond and SiC in primitive chondrites - Abundances reflect metamorphism

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.

    1990-01-01

    It is shown here that interstellar diamond and SiC were incorporated into all groups of chondrite meteorites. Abundances rapidly go to zero with increasing metamorphic grade, suggesting that metamorphic destruction is responsible for the apparent absence of these grains in most chondrites. In unmetamorphosed chondrites, abundances normalized to matrix content are similar for different classes. Diamond samples from chondrites of different classes have remarkably similar noble-gas constants and isotropic compositions, although constituent diamonds may have come from many sources. SiC seems to be more diverse, partly because grains are large enough to measure individually, but average characteristics seem to be similar from meteorite to meteorite. These observations suggest that various classes of chondritic meteorites sample the same solar system-wide reservoir of interstellar grains.

  20. Heat transport by fluids during late Cretaceous regional metamorphism in the Big Maria Mountains, southeastern California.

    USGS Publications Warehouse

    Hoisch, T.D.

    1987-01-01

    The Big Maria Mountains of SE California preserve evidence of a large-scale fluid flux that accompanied regional metamorphism in late Cretaceous time. Neither magmatism nor radioactive heat sources are adequate to explain the T of metamorphism. Simultaneously crystallizing plutons at different levels within the crust could have contributed to the overall hot fluid flux. A fluid:rock ratio of 17:1 may be calculated given average conditions of 3 kbar, 500oC, an infiltrating fluid of composition XH2O = 1.0, an equilibrium fluid composition of XH2O = 0.97, and 90% wollastonite in the final rock form the reaction quartz + calcite = CO2 + wollastonite. The minimum quantity of fluid of 1.7 rock volume was estimated to pass through the area if the fluid was approximately at granite solidus T at the start. Deep penetrative structures within the crust may have served to channel fluids. -L.C.H.

  1. Anatexis and metamorphism in tectonically thickened continental crust exemplified by the Sevier hinterland, western North America

    NASA Technical Reports Server (NTRS)

    Patino Douce, Alberto E.; Humphreys, Eugene D.; Johnston, A. Dana

    1990-01-01

    This paper presents a thermal and petrologic model of anatexis and metamorphism in regions of crustal thickening exemplified by the Sevier hinterland in western North America, and uses the model to examine the geological and physical processes leading to crustally derived magmatism. The results of numerical experiments show that anatexis was an inevitable end-product of Barrovian metamorphism in the thickened crust of the late Mesozoic Sevier orogenic belt and that the advection of heat across the lithosphere, in the form of mantle-derived mafic magmas, was not required for melting of metasedimentary rocks. It is suggested that, in the Sevier belt, as in other intracontinental orogenic belts, anatexis occurred in the midcrust and not at the base of the crust.

  2. Heat production rate from radioactive elements in igneous and metamorphic rocks in Eastern Desert, Egypt.

    PubMed

    Abbady, Adel G E; El-Arabi, A M; Abbady, A

    2006-01-01

    Radioactive heat-production data of Igneous and Metamorphic outcrops in the Eastern Desert are presented. Samples were analysed using a low level gamma-ray spectrometer (HPGe) in the laboratory. A total of 205 rock samples were investigated, covering all major rock types of the area. The heat-production rate of igneous rocks ranges from 0.11 (basalt) to 9.53 microWm(-3) (granite). In metamorphic rocks it varies from 0.28 (serpentinite ) to 0.91 microWm(-3) (metagabbro). The contribution due to U is about 51%, as that from Th is 31% and 18% from K. The corresponding values in igneous rocks are 76%, 19% and 5%, respectively. The calculated values showed good agreement with global values except in some areas containing granites. PMID:16120480

  3. Metamorphic core complexes: Expression of crustal extension by ductile-brittle shearing of the geologic column

    NASA Technical Reports Server (NTRS)

    Davis, G. H.

    1985-01-01

    Metamorphic core complexes and detachment fault terranes in the American Southwest are products of stretching of continental crust in the Tertiary. The physical and geometric properties of the structures, fault rocks, and contact relationships that developed as a consequence of the extension are especially well displayed in southeastern Arizona. The structures and fault rocks, as a system, reflect a ductile-through-brittle continuum of deformation, with individual structures and faults rocks showing remarkably coordinated strain and displacement patterns. Careful mapping and analysis of the structural system has led to the realization that strain and displacement were partitioned across a host of structures, through a spectrum of scales, in rocks of progressively changing rheology. By integrating observations made in different parts of the extensional system, especially at different inferred depth levels, it has been possible to construct a descriptive/kinematic model of the progressive deformation that achieved continental crustal extension in general, and the development of metamorphic core complexes in particular.

  4. Prehnite in plutonic and metamorphic rocks of the northern Santa Lucia Range, Salinian block, California

    USGS Publications Warehouse

    Ross, Donald C.

    1976-01-01

    Prehnite is abundant as monomineralic veins, as lenses in biotite, and as discrete patches and apparent primary crystals in both plutonic and metamorphic rocks along the west edge of the Salinian block in the northern Santa Lucia Range. The prehnite appears to be concentrated near the Sur fault zone but is very rare in Franciscan rocks west of the fault zone. The prehnite does not appear to have been derived by local alteration of minerals in the country rocks (either plutonic or metamorphic). I suggest that solutions, derived from a "substratum" (possibly Franciscan graywacke) beneath the tectonically thinned west margin of the Salinian block, migrated through the fractured rocks of the Salinian block near the Sur fault zone and that the chemical and physical nature of these rocks favored selective prehnite deposition.

  5. Diamond from the dabie shan metamorphic rocks and its implication for tectonic setting.

    PubMed

    Shutong, X; Wen, S; Yican, L; Laili, J; Shouyuan, J; Okay, A I; Sengör, A M

    1992-04-01

    Diamond occurs in ultrahigh pressure metamorphic rocks from Dabie Shan, Anhui Province, eastern China. Diamond-bearing rocks include eclogite, gamet-pyroxenite, and jadeitite. Diamond occurs in a mineral assemblage with coesite and jadeite. The diamonds and diamondiferous rocks of Dabie Shan are interpreted to be the products of ultrahigh pressure metamorphism in the undérthrust basement of the Yangtze continental plate during the early Mesozoic, at greater than 4.0 gigapascals and 900 degrees C. This interpretation is based on the distribution of rock units, the stability field of diamond, and isotopic data indicating a crustal origin for the rocks. Most diamonds occur as euhedral inclusions in garnets and are 10 to 60 micrometers across, although some are up to 700 micrometers across. PMID:17802596

  6. Fluorian garnets from the host rocks of the Skaergaard intrusion: implications for metamorphic fluid composition

    USGS Publications Warehouse

    Manning, C.E.; Bird, D.K.

    1990-01-01

    Zoned, silica-deficient, calcic garnets containing up to 5 mol% F substitution for O formed during contact metamorphism of basalts by the Skaergaard intrusion in East Greenland. Fluorian calcic garnets occur as a retrograde alteration of prograde wollastonite and clinopyroxene that fills vesicles and vugs in lavas 30-70 m from the intrusion. The F content of garnet is extremely sensitive to minor changes in fluid composition. The calculations show that a decrease in pH or an increase in log aF- of 0.3 at constant pressure and temperature will decrease the F concentration in garnet from 5 to 0 mol%. The results of this study show that fluorian hydrous grandites provide a mineralogical record of the activities of F species in coexisting metamorphic and hydrothermal fluids. -from Authors

  7. Cymrite and celsian in manganese-rich metamorphic rocks from Andros Island/Greece

    NASA Astrophysics Data System (ADS)

    Reinecke, Thomas

    1982-07-01

    Manganese-rich rocks from the island of Andros (Cyclades/Greece) contain cymrite (BaAl2Si2O8·H2O) and celsian. The textural relationships indicate replacement of celsian by cymrite. Several microprobe analyses of cymrites show a solid solution of 0.7 6.1 mole% KAlSi3O8·H2O. The relic celsians have similar K contents. Thus the described rocks from Andros represent the first natural example for the reaction celsian+water= cymrite. The rocks from Andros underwent an Eocene high pressure metamorphism. Lateron, the high pressure parageneses were nearly effaced by a Late Oligocene Barrovian type metamorphism. It is assumed that both cymrite and celsian were formed at conditions near the reaction curve celsianss+water= cymritess during the Barrovian type event.

  8. Relaxation dynamics and residual strain in metamorphic AlSb on GaAs

    SciTech Connect

    Ripalda, J. M.; Rivera, A.; Alen, B.; Gonzalez, Y.; Gonzalez, L.; Briones, F.; Sanchez, A. M.; Taboada, A. G.; Rotter, T. J.; Balakrishnan, G.

    2012-01-02

    We have observed the evolution of the accumulated stress during heteroepitaxial growth of highly lattice mismatched AlSb on GaAs by measuring the deformation of the substrate as a function of time. High resolution transmission electron microscopy images show almost all of the plastic relaxation is accommodated by an array of 90 deg. misfit dislocations at the interface. The in-plane lattice parameter of the resulting metamorphic AlSb is slightly smaller (0.3%) than the bulk value and perfectly matches the lattice parameter of bulk GaSb. It is, therefore, possible to grow nearly stress-free GaSb on GaAs using a metamorphic AlSb buffer layer.

  9. Rates of Metamorphic and Tectonic Processes Derived From Garnet Chemistry and Phase Diagrams

    NASA Astrophysics Data System (ADS)

    Stowell, H. H.

    2005-12-01

    Sm and Nd isotope data for the interior parts of a garnet crystal (core) and the whole rock can be used to calculate the timing of initial growth. Isotope data for the external parts of a garnet crystal (rim) and the rock matrix can be used to calculate the timing of final growth. Similarly, major element chemistry can be used to calculate pressures (P) and temperatures (T) of metamorphism for initial and final garnet growth. Combination of these data allows estimation of garnet growth, heating, and loading rates. Sm-Nd isochrons were constructed for garnet core and whole rock, and for garnet rim and rock matrix (whole rock minus garnet). For core and rim ages that are indistinguishable, uncertainties for a single isochron constrain the duration of garnet growth. P and T were estimated from the intersection of garnet chemical isopleths on P-T phase diagrams for specific rocks (pseudosections), and garnet rim thermobarometry and/or pseudosection peak mineral stability fields. Results from Cretaceous contact and regional metamorphic environments provide preliminary data for comparison. Schist from Garnet Ledge, AK. 20 mm garnet crystals in pelite less than 1 km from a diorite pluton grew during contact metamorphism over ca. 0.5 m.y. during a 70°C increase in T and 0.6 kbar increase in P. Growth, heating, and loading rates are 20 mm/m.y., 140°C/m.y., 1.2 kbar/m.y., respectively. Chiwaukum Schist from near the Mount Stuart batholith, WA. 14 mm garnet crystals in pelite less than 2 km from the Mt. Stuart batholith grew during regional metamorphism over <1.4 m.y. during a 75°C increase in T and 1.2 kbar increase in P. Growth, heating, and loading rates are 5 mm/m.y., 54°C/m.y., 0.9 kbar/m.y., respectively. 5 mm garnet crystals in pelite adjacent to orthogneiss grew during contact metamorphism over <1.8 m.y. while T and P increased to peak conditions of 630°C and 6.8 kbar. Pembroke granulite from Fiordland, New Zealand. 16 mm peritectic garnet crystals in lower

  10. Seismic characterization of an active metamorphic massif, Nanga Parbat, Pakistan Himalaya

    NASA Astrophysics Data System (ADS)

    Meltzer, Anne; Sarker, Golam; Beaudoin, Bruce; Seeber, Leonardo; Armbruster, John

    2001-07-01

    Earthquakes recorded by a dense seismic array at Nanga Parbat, Pakistan, provide new insight into synorogenic metamorphism and mass flow during mountain building. Microseismicity beneath the massif drops off sharply with depth and defines a shallow transition between brittle failure and ductile flow. The base of seismicity bows upward, mapping a thermal boundary with 3 km of structural relief over a lateral distance of 12 km. Anomalously low seismic velocities are observed at the core of the massif and extend to depth through the crust. The main locus of seismicity and low velocities correlates with a region of high topography, rapid exhumation, high geothermal gradients, young metamorphic and igneous ages, and crustal fluid flow. We suggest a genetic link between these phenomena in which hot rocks, rapidly advected from depth, are pervasively modified at relatively shallow levels in the crust.

  11. Zeolite to prehnite-pumpellyite facies metamorphism in the Toa Baja drill hole, Puerto Rico

    SciTech Connect

    Cho, M. )

    1991-03-01

    Secondary mineral assemblages in Eocene volcanic and volcaniclastic rocks of the Toa Baja drill hole progressively change as a function of depth. Four metamorphic zones are delineated with increasing depth: Ca-clinoptilolite{yields}heulandite{yields}laumontite{yields}prehnite-pumpellyite zone. The deepest belongs to the prehnite-pumpellyite facies, whereas the three zones at shallower depths (< 2,350 m) belong to the zeolite facies. Ca-clinoptilolite and heulandite exhibit continuous solid solution with varying Si/Al (2.9-5.2) and Ca/(Ca + Na + K) ratios (0.45-0.89). Pumpellyites are characterized by extensive variation in the Fe/(Fe + Al + Mg) ratio (0.29-0.74) and extreme Fe-enrichment in the laumontite zone. Temperatures estimated from mineral assemblages and facies transitions suggest that the North Coast Basin, Puerto Rico, has been subject to a metamorphic field gradient of {approximately}50 to 70C/km.

  12. Permian basic magmatism, Upper Eocene and Lower Oligocene metamorphism in the Furgg zone (Western Alps)

    NASA Astrophysics Data System (ADS)

    Liati, A.; Gebauer, D.; Froitzheim, N.

    2003-04-01

    The Furgg zone (Western Alps) separates the Monte Rosa nappe from the Bernhard and Zermatt nappes. It consists mainly of a schist-, leucocratic gneiss-, quartzite- and metacarbonate-matrix containing boudins of amphibolitised eclogites. Controversial views exist on the nature, origin and extent of the Furgg zone (cf. Dal Piaz, 2001). We dated by SHRIMP (GSC, Ottawa) magmatic and metamorphic zircon domains of a metabasite in the area of Stockknubel (north of the western part of the Monte Rosa nappe). This metabasite is a strongly retrogressed eclogite occurring in form of a boudin, ca. 1 m long, within leucocratic schists. Based on cathodoluminescence (CL)-imaging, zircons from this rock consist of large oscillatory zoned (magmatic) domains surrounded by metamorphic (recrystallisation) rims, bright in CL, with ghost oscillatory zoning. Bright CL-domains are irregularly dispersed also inside the magmatic domains, due to fluid circulation along fractures during metamorphism(s). Eight spot analyses on the magmatic domains yield a Permian weighted mean age at 269 ± 3 Ma (95% c.l.), corresponding to the crystallisation time of the gabbroic protolith of this metabasite. This age is in agreement with a ca. 272 Ma age reported for the crystallisation of an orthogneiss at Mattmark (farther east in the Furgg zone; Liati et al., 2001), as well as for Monte Rosa granites. The new Permian protolith age of the metabasic rock in Stockknubel, together with a 510 ± 5 Ma age reported for an eclogite boudin from the eastern part of the Furgg zone, is in agreement with the 'mélange hypothesis' for the origin of the Furgg zone (e.g. Froitzheim, 2001). 11 spot analyses on metamorphic domains indicate a strong influence of the Lepontine event at 31.5 ± 1.0 Ma (weighted mean of 8 analyses), accompanied by influx of high amounts of fluids. Of great interest are metamorphic rim analyses at ca. 38-39 Ma, together with a series of data scattering between this and the ca. 31.5 Ma age. The

  13. Metamorphism, argon depletion, heat flow and stress on the Alpine fault

    NASA Technical Reports Server (NTRS)

    Scholz, C. H.; Beavan, J.; Hanks, T. C.

    1978-01-01

    The Alpine fault of New Zealand is a major continental transform fault which was uplifted on its southeast side 4 to 11 km within the last 5 m.y. This uplift has exposed the Haast schists, which were metamorphosed from the adjacent Torlesse graywackes. The Haast schists increase in metamorphic grade from prehnite-pumpellyite facies 9-12 km from the fault through the chlorite and biotite zones of the greenschist facies to the garnet-oligoclase zone amphibolite facies within 4 km of the fault. These metamorphic zone boundaries are subparallel to the fault for 350 km along the strike. The K-Ar and Rb-Sr ages of the schists increase with distance from the fault: from 4 m.y. within 3 km of the fault to approximately 110 m.y. 20 km from the fault. Field relations show that the source of heat that produced the argon depletion aureole was the fault itself.

  14. Meteorite impact, cryptoexplosion, and shock metamorphism - A perspective on the evidence at the K/T boundary

    NASA Technical Reports Server (NTRS)

    Sharpton, V. L.; Grieve, R. A. F.

    1990-01-01

    A perspective on the evidence of a major impact event at the K/T boundary is proposed using field and laboratory studies of terrestrial impact craters. Recent assertions that diagnostic indications of shock metamorphism are also produced in volcanic environments are challenged. A general geological framework of impact structures is developed and the issue of volcanically induced shock metamorphism is examined. Cryptoexplosion is addressed by assessing the geology of two structures: the Slate Islands and Manson, which are often cited by advocates of an internal origin for shock metamorphism as volcanic structures. It is concluded that the link between shock metamorphism and meteorite impact is now established beyond reasonable doubt. The occurrence and worldwide distribution of shocked minerals at the K/T boundary is considered to be the conclusive evidence for a major impact event.

  15. Some features of the change in the carbonyl group content of coal in the process of metamorphism

    SciTech Connect

    Kucherenko, V.A.; Kuznetsova, L.V.; Sapunov, V.A.; Osipov, A.M.

    1983-01-01

    Different forms of carbonyl groups were studied in Donbass coals and it was shown that there is a relationship between the variation in quinoidal and ketonic oxygen and the degree of metamorphism. (17 refs.)

  16. High grade metamorphism in the Bundelkhand massif and its implications on Mesoarchean crustal evolution in central India

    NASA Astrophysics Data System (ADS)

    Singh, S. P.; Dwivedi, S. B.

    2015-02-01

    The Bundelkhand Gneissic Complex (BnGC) in the central part of the Bundelkhand massif preserves a supracrustal unit which includes pelitic (garnet-cordierite-sillimanite gneiss, garnet-sillimanite gneiss, biotite gneiss and garnet-biotite gneiss) and mafic (hornblende-biotite gneiss and garnetiferous amphibolite) rocks. Granulite facies metamorphism of the complex initiated with breaking down of biotite to produce garnet and cordierite in the pelitic gneisses. Geothermobarometric calculations indicate metamorphic conditions of 720°C/6.2 kbar, followed by a retrograde (687°C/4.9 kbar) to very late retrograde stages of metamorphism (579°C/4.4 kbar) which is supported by the formation of late cordierite around garnet. The P-T conditions and textural relations of the garnet-cordierite-bearing gneiss suggest a retrograde cooling path of metamorphism.

  17. Meteorite impact, cryptoexplosion, and shock metamorphism - A perspective on the evidence at the K/T boundary

    NASA Astrophysics Data System (ADS)

    Sharpton, V. L.; Grieve, R. A. F.

    A perspective on the evidence of a major impact event at the K/T boundary is proposed using field and laboratory studies of terrestrial impact craters. Recent assertions that diagnostic indications of shock metamorphism are also produced in volcanic environments are challenged. A general geological framework of impact structures is developed and the issue of volcanically induced shock metamorphism is examined. Cryptoexplosion is addressed by assessing the geology of two structures: the Slate Islands and Manson, which are often cited by advocates of an internal origin for shock metamorphism as volcanic structures. It is concluded that the link between shock metamorphism and meteorite impact is now established beyond reasonable doubt. The occurrence and worldwide distribution of shocked minerals at the K/T boundary is considered to be the conclusive evidence for a major impact event.

  18. Metamorphic and geochemical signatures within calc-silicate gneisses of the Sawtooth Metamorphic Complex, ID: Implications for western North America crustal evolution

    NASA Astrophysics Data System (ADS)

    Fukai, I.; Dutrow, B. L.; Henry, D.; Mueller, P. A.; Foster, D. A.

    2012-12-01

    High resolution sampling and petrologic/geochemical analyses of calc-silicate metamorphic rocks from the Sawtooth Metamorphic Complex (SMC), ID, constrain the evolution of a key area in North America. The SMC lies within the proposed Paleoproterozoic Selway basement terrane on the southwestern margin of Laurentia. Multi-equilibria thermobarometry calculations on SMC aluminous gneisses yield lower-granulite facies peak metamorphic conditions of 765-795 °C and 7 kbar, suggesting the SMC represents a segment of lower-middle crust. Twenty-five calc-silicate samples were collected 1 km east of the aluminous gneisses along a 132 m transect across the regional N-S strike of the SMC. Samples have a mineral assemblage of clinopyroxene + quartz + tremolite + plagioclase + titanite + apatite ± K-feldspar ± clinozoisite ± biotite ± epidote ± graphite ± calcite, and display a range in whole-rock compositions (wt.%) of SiO2 (53.9-80.9), Al2O3 (3.4-12.4), FeO (1.0-5.9), CaO (5.2-21.5), MgO (3.3-9.5), and K2O (0.04-3.8). Samples exhibit decreasing modal amounts of qz, pl, kf, and bt from west to east, along with an increase in cpx, ttn, czo, ep, gr and cal. Major element geochemical trends are consistent with the observed mineralogical variations, revealing higher weight percentages of SiO2 (62-81) and K2O (0.8-3.8) in western samples, and higher TiO2, Al2O3, FeO, MgO CaO, and LOI in the easternmost samples. Eastern samples have lower compositions of Rb and Ba, and higher Sr and Cr relative to western samples that correspond respectively to decreased modal amounts of fsp and bt, and an increase in cal and cpx. Trace elements Ni, Sc, V, Y, Nb, Ce, Nd, Cu, Pb, Th, and La do not show systematic variations. SMC calc-silicates have an average Th/Sc ratio of 0.89, consistent with Post-Archean values (>0.7), and display high concentrations of Zr relative to Th, and Sc, more characteristic of an evolved, recycled, continental sediment source. Application of the hornblende

  19. Evolution of the northern Sierra Nevada metamorphic belt: Petrological, structural, and Ar/Ar constraints

    SciTech Connect

    Hacker, B.R.

    1993-05-01

    The Sierra Nevada metamorphic belt constitutes an important record of the growth of continental crust from essentially oceanic materials. In the northern Sierra, the central part of the belt is made up of volcanoplutonic arcs and sediment-dominated units inferred to be accretionary wedges or closed ocean basins. The latter are broken formation and melange composed of radiolarian chert, lava, and volcanogenic and continental turbidites. Sedimentary detritus in the largest of these units can be plausibly linked to sources farther east in the Sierra, suggesting that deposition occurred near the eastern Sierran arc. Isoclinal folds, steeply dipping foliations, and steeply plunging down-dip lineations are characteristics structures. The westernmost unit is only feebly recrystallized, and deformation was accomplished principally by stress solution and local redeposition in veins. More easterly, inboard units are compositionally similar, but they recrystallized at pumpellyite-actinolite-and blueschist-facies conditions and deformed via solution-transfer and dislocation creep. Phengite silica contents, the degree of quartz veining, and the locations of pseudo-isograds support an eastward increase in metamorphic pressure and temperature. Metamorphic conditions during the growth of pumpellyite and actinolite ranged from {approximately}150-350 {degrees}C and 200-400 MPa, compatible with recrystallization and deformation in subduction zones or the deeper levels of magmatic arcs. Ar/Ar ages of volcanisclastic rocks and crosscutting plutons constrain the age of deformation and metamorphism in the western part of the region to 174-165 Ma. Deformation and recrystallization in more easterly units may have been coeval or begun as early as Triassic time. 58 refs., 14 figs., 4 tabs.

  20. Structural and lithologic relationships in the Raleigh metamorphic belt near Lake Gaston, Virginia and North Carolina

    SciTech Connect

    Sacks, P.E.; Horton, J.W. Jr. )

    1993-03-01

    Preliminary results of mapping along the NC-VA State line eastward from the Buggs Is. granite about 35 km to the Hollister fault zone yield new information about structural and lithologic relationships in the Raleigh metamorphic belt. The layered rocks are predominantly two-mica schist and sillimanite-mica schist interlayered with lesser amounts of muscovite-biotite-quartz-plagioclase paragneiss and hornblende-biotite gneiss. The overall rock assemblage here differs from those along strike near Goochland, VA, and near Raleigh, NC, and is reminiscent of an accretionary complex. Bodies of foliated to massive two-mica granite are abundant and commonly contain garnet. One body, the Wise pluton, contains a N--NW-striking, steeply dipping foliation, but the intrusive contact of the granite with the metamorphic rocks is discordant. The most prominent regional foliation, parallel to transposed compositional layering, is axial planar to relict, reclined, isoclinal outcrop-scale folds. This foliation is folded at both outcrop and map scale by open folds plunging NW and SW. Some foliated, two-mica granite sheets are warped by the open folds; other bodies of similar granite cut across these folds. Sillimanite needles are locally aligned with the hinges of some of the open folds, an indication that sillimanite-muscovite-grade metamorphism was associated with this folding event. The two-mica granites resemble other late Paleozoic granites in the region. If these granites prove to be late Paleozoic (Alleghanian), then the deformation and metamorphism that produced sillimanite along the hingelines also must be Alleghanian. Relatively younger, NW- and SE-plunging crenulations and chevron folds are associated with a crenulation cleavage that dips steeply NE or SW. Sillimanite needles are folded by these crenulations. Crenulation cleavage and related folds may have developed in response to transpression of these rocks between the dextral Lake Gordon and Hollister mylonite zones.

  1. Design and accuracy analysis of a metamorphic CNC flame cutting machine for ship manufacturing

    NASA Astrophysics Data System (ADS)

    Hu, Shenghai; Zhang, Manhui; Zhang, Baoping; Chen, Xi; Yu, Wei

    2016-05-01

    The current research of processing large size fabrication holes on complex spatial curved surface mainly focuses on the CNC flame cutting machines design for ship hull of ship manufacturing. However, the existing machines cannot meet the continuous cutting requirements with variable pass conditions through their fixed configuration, and cannot realize high-precision processing as the accuracy theory is not studied adequately. This paper deals with structure design and accuracy prediction technology of novel machine tools for solving the problem of continuous and high-precision cutting. The needed variable trajectory and variable pose kinematic characteristics of non-contact cutting tool are figured out and a metamorphic CNC flame cutting machine designed through metamorphic principle is presented. To analyze kinematic accuracy of the machine, models of joint clearances, manufacturing tolerances and errors in the input variables and error models considering the combined effects are derived based on screw theory after establishing ideal kinematic models. Numerical simulations, processing experiment and trajectory tracking experiment are conducted relative to an eccentric hole with bevels on cylindrical surface respectively. The results of cutting pass contour and kinematic error interval which the position error is from-0.975 mm to +0.628 mm and orientation error is from-0.01 rad to +0.01 rad indicate that the developed machine can complete cutting process continuously and effectively, and the established kinematic error models are effective although the interval is within a `large' range. It also shows the matching property between metamorphic principle and variable working tasks, and the mapping correlation between original designing parameters and kinematic errors of machines. This research develops a metamorphic CNC flame cutting machine and establishes kinematic error models for accuracy analysis of machine tools.

  2. Hinterland-to-foreland structural evolution of the base of the Himalayan metamorphic core, west Nepal

    NASA Astrophysics Data System (ADS)

    Braden, Z.; Godin, L.; Yakymchuk, C.; Kellett, D.; Cottle, J. M.

    2015-12-01

    The base of the Himalayan metamorphic core is a folded reverse-sense shear zone exposed extensively along its transport direction. In west Nepal, along-transport exposures show a transition in structural style from hinterland to foreland, and sampled quartzite and pelite show variations in thermobarometry, quartz crystallographic preferred orientation (CPO), monazite Th-Pb ages and 40Ar/39Ar thermochronology. In the hinterland region, the shear zone yields a deformation temperature gradient from > 700°C at the top of the shear zone down to 400°C at the base. Metamorphic grade also decreases downwards through the shear zone. Muscovite 40Ar/39Ar ages are ca. 6 Ma. In the transition zone separating hinterland and foreland on the north flank of the Karnali klippe, a comparable structural section yields a deformation temperature gradient that similarly decreases down structural level from ~700 to 500°C. Muscovite 40Ar/39Ar dating yield ca. 14-12 Ma cooling ages. In-situ monazite geochronology indicates prograde metamorphism at ca. 43-34 Ma and melt crystallization at ca. 26-18 Ma. In the foreland, deformation is not strictly brittle; CPO analyses on sheared quartzite on the south flank of the Karnali klippe suggest deformation temperatures decreasing from 500 to 400°C downwards through the shear zone. Muscovite from the foreland yields 40Ar/39Ar ages of ca. 17 Ma. Deformation temperatures decrease marginally from hinterland to foreland and structurally downward within the shear zone, and estimates suggest ductile deformation prevails well into the foreland. Hinterland 40Ar/39Ar muscovite ages in west Nepal are anomalously young, and are possibly related to recent exhumation due to the SE-propagating mid-Miocene Gurla Mandhata-Humla system. Alternatively, they could be linked to the activation of a young duplex in the footwall of the Himalayan metamorphic core due to along-strike variation in geometry of the Main Himalayan thrust ramp.

  3. Metamorphic signature of the Gneiss Canyon Shear Zone, Lower Granite Gorge, Grand Canyon, Arizona

    SciTech Connect

    Robinson, K.; Williams, M.L. . Dept. of Geology and Geography)

    1992-01-01

    The Proterozoic orogen in Arizona consists of structural blocks separated by NE trending shear zones. The Gneiss Canyon Shear Zone (GCSZ) is important because it appears to define in part the boundary between the amphibolite facies Yavapai Province and the granulite facies Mojave Province. An early NW striking foliation is clearly visible in many samples from the Lower Granite Gorge (LGG). In Travertine Canyon, east of the GCSZ, pelitic schists contain And-Sil-Crd-Bi and Gar-Sil-Sta-Bi. Mafic rocks exhibit complex phase relations between cummingtonite, anthophyllite, gedrite, garnet, and cordierite. The coexistence of cordierite-cummingtonite is indicative of low pressure metamorphism. Microprobe analyses of garnets reveal prograde growth zoning profiles. Temperature and pressure estimates of peak metamorphism are 550--600 C and 3 kb. Just east of the GCSZ, pelitic assemblages contain Gar-Bi [+-] Sil [+-] Mus, and garnet zoning profiles are flat in the cores. In Spencer Canyon, west of the GCSZ, samples commonly contain Gar-Bi-Sil-Crd, and in many samples cordierite is being replaced by sillimanite. Thermobarometric calculations yield temperature and pressure estimates of 650 C and 3.5 kb. Mineral assemblages and quantitative thermobarometry suggest higher peak metamorphic temperature west of the GCSZ but relatively constant pressures across the LGG. On the east side of the GCSZ, temperatures increase toward the Shear Zone, probably due to the presence of extensive dikes, pods, and veins of variably deformed granite. Peak mineral assemblages are syntectonic with respect to the NE-striking GCSZ fabric. If a suture exists in the LGG, the GCSZ fabrics apparently reflect post-accretionary tectonism, with accretion occurring prior to the peak of metamorphism.

  4. Modeling magmatic accumulations in the upper crust: Metamorphic implications for the country rock

    NASA Astrophysics Data System (ADS)

    Douglas, Madison M.; Geyer, Adelina; Álvarez-Valero, Antonio M.; Martí, Joan

    2016-06-01

    Field exposures of magma chambers tend to reveal contact metamorphic aureoles in the surrounding crust, which width varies from few centimeters to kilometers. The igneous accumulation not only increases the temperature around it, but also weakens its surrounding country rock beyond the brittle-ductile transition temperature. The formation of a ductile halo around the magmatic reservoir may significantly impact into the stability and growth of the magma chamber, as well as into potential dyke injections and processes of ground deformation. In this paper, we examine how a magmatic accumulation affects the country rock through the combination of petrologic and thermal perspectives. For this, we numerically modeled (i) the conductive cooling of an instantaneously emplaced magma chamber within compositionally representative pelitic and carbonate upper crusts, and (ii) the corresponding changes in the viscosity of the host rock potentially leading to ductile regimes. We consider basaltic to rhyolitic magma chambers at different depths with oblate, prolate and spherical geometries. The resulting temperature field distribution at different time steps is integrated with crustal metamorphic effects through phase diagram modeling. Our results indicate that the geometry of the magma accumulations plays a dominant role in controlling the local metamorphic and thermal effects on the country rocks. They conclude that (i) the combination of relatively simple geothermal models with petrologic datasets can generate first order predictions for the maximum metamorphic grade and geometry of magma chamber aureoles; (ii) the possible changes in the mechanical properties of the country rock are not necessarily linked to the petrological changes in contact aureoles; and (iii) the present rheologic outcomes may be used in further studies of magma chamber stability and integrity, which may favor the understanding of the melt transfer throughout the crust.

  5. Post-metamorphic fluid infiltration into granulites from the Adirondack Mountains, USA

    NASA Technical Reports Server (NTRS)

    Morrison, J.; Valley, John W.

    1988-01-01

    Post-metamorphic effects in the anorthosites of the Adirondacks, New York were described. Calcite-chlorite-sericite assemblages occur as veins, in disseminated form and as clots, and document retrograde fluid infiltration. These features are associated with late-state CO2-rich fluid inclusions. Stable isotope analyses of calcites indicates that the retrograde f