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  • 1
    Electronic Resource
    Electronic Resource
    Measurement of grain growth in the recrystallization of rapidly frozen solutions of antifreeze glycoproteins (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 1495-1504 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quantitative estimate of the activation energy for grain growth has been obtained by analyzing ice recrystallization experiments from water and from solutions with small amounts (〈 1.0 μg/mL) of antifreeze glycoprotein (AFGP). Rates of grain growth are measured as changes of grain diameter in time, with the supercooled holding temperature aVid glycoprotein concentration as parameters. Arrhenius plots of these rates vs (1/T) yielded slopes proportional to the activation energies for the particular species. The values of activation energy are almost independent of solution concentration or the species of AFGP. Averaged activation energy value for the AFGP-4 species is Qg = (6.61 ± 1.02) × 105 J/mole. The “less active” AFGP-8 yielded an average Qg = (5.71 ± 2.39) × 105 J/mole, quite similar to the AFGP-4 species. The activation energy for recrystallization in a pure ice-water system was estimated from two temperature points, T = -5.4 and -7.5°C. The best value is 2.39 × 105 J/mole, nearly twice that obtained by M. N. Martino and N. E. Zaritsky [(1989) Cryobiology, Vol. 26, p. 138] in a recrystallization experiment using salt solution, but much smaller than the values derived from the AFGP solutions. Results further show that activation entropy is at least a factor of 2 larger for the AFGP species than that of pure ice-water system under the same growth conditions. These results suggest significant roles, both energetically and entropically, for AFGP molecules in their ability to inhibit grain growth of ice. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360341107
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  • 2
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    Subduction zone polarity in the Oman Mountains: implications for ophiolite emplacement (2003)
    In:  Geological Society Special Publication 218: 467-480.
    Details
    Publication Date: 2003-01-01
    Description: Two end-member models have been proposed to account for the structure and metamorphism of rocks beneath the Semail ophiolite in the Oman mountains. Model A involves a single, continuous NE-directed subduction away from the continental margin during the late Cretaceous. The ophiolite and underlying thrust sheets of distal to proximal oceanic sediments were emplaced a minimum of 250 km SW onto the continental margin. Subduction of Triassic-Jurassic oceanic basalts to c. 10 kbar (c. 39 km depth) led to the accretion of amphibolite-facies rocks to the base of the ophiolite. Thrusting propagated towards the continental margin and ended with subduction of the thinned continental crust to c. 20 kbar (c. 78 km depth), choking the subduction zone. Buoyancy forces caused the rapid exhumation of eclogites, blueschists and carpholite-grade HP rocks along the NE margin of the continental plate. During the later phase of foreland-propagating thin-skinned thrusting in the SW, NE-facing backfolding and backthrusting occurred in the hinterland, with the final exhumation of the HP rocks. Model B follows recent suggestions that a nascent SW-dipping subduction zone, dipping beneath the continental margin, existed between 130 and 95 Ma, prior to formation and emplacement of the ophiolite. A major NE-facing fold-nappe structure in the pre-Permian basement rocks of Saih Hatat is interpreted as reflecting subduction beneath the margin. Two high-pressure metamorphic events have been suggested, the first predating ophiolite emplacement, the second caused by ophiolite loading. This model is untenable, being based on a misinterpretation of the NE-facing structures in northern Saih Hatat, and on some dubious older 40Ar/39Ar cooling ages from the eclogite-facies rocks of As Sifah. We conclude that all structures in northern Oman and all the reliable geochronology point to a single emplacement-obduction event lasting from Cenomanian-Turonian time (c. 95 Ma) when amphibolites were accreted along the metamorphic sole of the ophiolite, to Campanian time, when the continental margin was subducted to the NE producing blueschists and eclogites, to the final thin-skinned emplacement of all thrust sheets, which ended before the Late Maastrichtian, at c. 68 Ma.
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  • 3
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    Weathering Processes in Relation to Leachate Properties of Alkaline Fly Ash (1984)
    Wiley
    Details
    Publication Date: 1984-10-01
    Print ISSN: 0047-2425
    Electronic ISSN: 1537-2537
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 4
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    Lithological, rheological, and fluid infiltration control on 40Ar/39Ar ages in polydeformed rocks from the West Cycladic detachment system, Greece (2015)
    Geological Society of America (GSA)
    Details
    Publication Date: 2015-04-01
    Description: In situ ultraviolet (UV) laser-ablation 40 Ar/ 39 Ar dating, microstructural analysis, and stable O, H, and C isotope analyses were performed on white mica–bearing calcite– and quartz–mica schists of the West Cycladic detachment system footwall in order to resolve outstanding uncertainties about the timing of deformation and the role of rock rheology on 40 Ar/ 39 Ar dating systematics. In both quartz-rich and calcite-rich samples, deformed and chemically zoned white micas form two chemical populations: (1) a high component of Al-celadonite in undeformed portions of grains (high-pressure remnants), and (2) enrichment in muscovite in deformed portions (low-pressure neocrystallization). Micas in the quartz-rich rocks record higher internal strain, illustrated by elongated, sheared grains and boudinaged mica-fish structures. In this lithology, quartz formed a load-bearing framework that transferred strain to the muscovite packets and facilitated the formation of mica-fish structures. Recrystallization was promoted by coeval fluid infiltration, supported by stable isotope analyses and indented boundaries on bulging quartz grains. In rocks containing calcite-muscovite aggregates, the calcite formed an interconnected weak layer, with strain being accommodated by dislocation creep. In these rocks, micas were only partially neocrystallized. Prismatic white micas, largely unaffected by boudinage or kinking, yielded 40 Ar/ 39 Ar ages that are up to 10 m.y. older than deformed (kinked or sheared) portions of the same grains. Overall, the ages attest to strong lithological control on deformation- and fluid-controlled white mica neocrystallization. The oldest, undeformed grain ages in the calcite-rich rocks are consistent with the timing of Eocene metamorphism, with the deformed grain ages interpreted as representing the transition to lower-pressure conditions during nascent extension. Completely neocrystallized grains in the quartz-rich rocks are interpreted as defining the minimum age of Miocene ductile extension along the detachment system. The new data show the power of combining in situ laser-ablation 40 Ar/ 39 Ar dating, microstructural analysis, mineral chemistry, and stable isotope data for unraveling the timing and time scales of complex deformation histories.
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 5
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    Garnet-monazite rare earth element relationships in sub-solidus metapelites: a case study from Bhutan (2018)
    Geological Society of London
    Details
    Publication Date: 2018
    Description: 〈p〉A key aim of modern metamorphic geochronology is to constrain precise and accurate rates and timescales of tectonic processes. One promising approach in amphibolite and granulite-facies rocks links the geochronological information recorded in zoned accessory phases such as monazite to the pressure–temperature information recorded in zoned major rock-forming minerals such as garnet. Both phases incorporate rare earth elements (REE) as they crystallize and their equilibrium partitioning behaviour potentially provides a useful way of linking time to temperature. We report REE data from sub-solidus amphibolite-facies metapelites from Bhutan, where overlapping ages, inclusion relationships and Gd/Lu ratios suggest that garnet and monazite co-crystallized. The garnet–monazite REE relationships in these samples show a steeper pattern across the heavy (H)REE than previously reported. The difference between our dataset and the previously reported data may be due to a temperature-dependence on the partition coefficients, disequilibrium in either dataset, differences in monazite chemistry or the presence or absence of a third phase that competed for the available REE during growth. We urge caution against using empirically-derived partition coefficients from natural samples as evidence for, or against, equilibrium of REE-bearing phases until monazite–garnet partitioning behaviour is better constrained.〈/p〉 〈p〉〈b〉Supplementary material:〈/b〉 Trace element concentrations and data, detailed analytical information, field photographs, chemical maps and thin section information are available at 〈a href="https://doi.org/10.6084/m9.figshare.c.4044323"〉https://doi.org/10.6084/m9.figshare.c.4044323〈/a〉〈/p〉
    Print ISSN: 0375-6440
    Electronic ISSN: 2041-4927
    Topics: Geosciences
    Published by Geological Society of London
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  • 6
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    Garnet-monazite rare earth element relationships in sub-solidus metapelites: a case study from Bhutan (2018)
    Geological Society (of London)
    Details
    Publication Date: 2018-04-09
    Description: A key aim of modern metamorphic geochronology is to constrain precise and accurate rates and timescales of tectonic processes. One promising approach in amphibolite and granulite-facies rocks links the geochronological information recorded in zoned accessory phases such as monazite to the pressure–temperature information recorded in zoned major rock-forming minerals such as garnet. Both phases incorporate rare earth elements (REE) as they crystallize and their equilibrium partitioning behaviour potentially provides a useful way of linking time to temperature. We report REE data from sub-solidus amphibolite-facies metapelites from Bhutan, where overlapping ages, inclusion relationships and Gd/Lu ratios suggest that garnet and monazite co-crystallized. The garnet–monazite REE relationships in these samples show a steeper pattern across the heavy (H)REE than previously reported. The difference between our dataset and the previously reported data may be due to a temperature-dependence on the partition coefficients, disequilibrium in either dataset, differences in monazite chemistry or the presence or absence of a third phase that competed for the available REE during growth. We urge caution against using empirically-derived partition coefficients from natural samples as evidence for, or against, equilibrium of REE-bearing phases until monazite–garnet partitioning behaviour is better constrained. Supplementary material: Trace element concentrations and data, detailed analytical information, field photographs, chemical maps and thin section information are available at https://doi.org/10.6084/m9.figshare.c.4044323
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
    Published by Geological Society (of London)
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  • 7
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    Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya (2014)
    Geological Society of London
    Details
    Publication Date: 2014-03-08
    Description: Geochemical and geochronological analyses provide quantitative evidence about the origin, development and motion along ductile faults, where kinematic structures have been overprinted. The Main Central Thrust is a key structure in the Himalaya that accommodated substantial amounts of the India–Asia convergence. This structure juxtaposes two isotopically distinct rock packages across a zone of ductile deformation. Structural analysis, whole-rock Nd isotopes, and U–Pb zircon geochronology reveal that the hanging wall is characterized by detrital zircon peaks at c . 800–1000 Ma, 1500–1700 Ma and 2300–2500 Ma and an Nd(0) signature of –18.3 to –12.1, and is intruded by c . 800 Ma and c . 500–600 Ma granites. In contrast, the footwall has a prominent detrital zircon peak at c . 1800–1900 Ma, with older populations spanning 1900–3600 Ma, and an Nd(0) signature of –27.7 to –23.4, intruded by c . 1830 Ma granites. The data reveal a c . 5 km thick zone of tectonic imbrication, where isotopically out-of-sequence packages are interleaved. The rocks became imbricated as the once proximal and distal rocks of the Indian margin were juxtaposed by Cenozoic movement along the Main Central Thrust. Geochronological and isotopic characterization allows for correlation along the Himalayan orogen and could be applied to other cryptic ductile shear zones. Supplementary material: Zircon U–Pb geochronological data, whole-rock Sm–Nd isotopic data, sample locations, photomicrographs of sample thin sections, zircon CL images, and detailed analytical conditions are available at www.geolsoc.org.uk/SUP18704 .
    Print ISSN: 0016-7649
    Topics: Geosciences
    Published by Geological Society of London
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  • 8
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    Acidification adjacent to an elemental sulfur stockpile: II. Trace element redistribution (1992)
    Canadian Science Publishing
    Details
    Publication Date: 1992-05-01
    Description: Total concentrations of Ag, As, B, Ba, Co, Cr, Cs, Ga, Hf, Hg, Mn, Mo, Ni, Rb, Sb, Sc, Se, Sr, Ta, Th, U, V, W, Zn, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Yb, and Lu, were determined by instrumental neutron activation analysis (INAA) for samples of elemental sulfur and samples of soil material from selected depths adjacent to a large elemental sulfur stockpile. The objective was to determine the total content of trace elements and examine their redistribution within surficial till material influenced by extreme acidity resulting from the oxidation of elemental sulfur. The elemental sulfur did not contain detectable (by INAA) quantities of other elements to contribute to soil contamination. Elements mobilized within the acidified section were derived solely from the parent till. An Fe-rich indurated layer that formed at the interface of the acidified and calcareous layers acted as a scavenger for As, Co, and Ga. Formation of aqueous sulfate complexes probably inhibited attenuation of Mn, Sc, Th, U, Zn and rare earth elements. Barium and Hf were enriched in the acidified material while B, Rb, Cs, Sb, Sr, Ta, and V displayed no evidence of redistribution. Mercury displayed the unique behavior of volatilization to the atmosphere from the soil surface.Key words: anthropogenic acidification, trace elements, weathering
    Print ISSN: 0008-4271
    Electronic ISSN: 1918-1841
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 9
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    Acidification adjacent to an elemental sulfur stockpile: I. Mineral weathering (1992)
    Canadian Science Publishing
    Details
    Publication Date: 1992-05-01
    Description: Soil pH values below 3.0 are measured in soil material located adjacent to stockpiles of elemental sulfur on sour gas plant sites. The objective of this study was to examine the influence of extreme acidity on the changes and redistribution of major chemical and mineralogical components in soil along the side of a 25-year-old elemental sulfur block. Soil samples, obtained from pits located 2 m from the side of the sulfur block, were analyzed for total content of Al, Fe, Ca, Mg, Na, K, and Ti. Sand and clay separates were analyzed by X-ray diffraction, and physical and chemical methods to identify and quantify mineral phases. Carbonate, Fe-containing primary minerals, chlorite, smectite, and plagioclase feldspars were either partially or completely dissolved in soil having pH values of about 2.1. Clay-sized mica and kaolinite were apparently not affected by the acidity. Calcium carbonate and Ca-feldspars dissolved in the presence of H2SO4 to form gypsum. Iron dissolved from minerals in the acidified surface layer was deposited primarily as oxyhydroxides at the interface of acidic and calcareous materials to form an indurated layer about 10–15 cm thick. Jarosite precipitated within the acidic material just above the indurated layer. Key words: Elemental sulfur, anthropogenic acidification, mineral weathering, acid soils
    Print ISSN: 0008-4271
    Electronic ISSN: 1918-1841
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 10
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    SIMPLE MICROWAVE DIGESTION TECHNIQUE FOR ELEMENTAL ANALYSIS OF MINERAL SOIL SAMPLES (1990)
    Canadian Science Publishing
    Details
    Publication Date: 1990-11-01
    Description: A new, rapid, and inexpensive method is described for digestion and dissolution of mineral soil and clay samples for determination of total elemental abundance. Standard soil samples were dissolved using HF and HNO3 in 60 mL Teflon bombs. Dissolution was complete after 7 min using a household microwave oven operating at 350 W. Addition of H3BO3 stabilized the digests against loss of silicon. Precise and accurate results were obtained for digests analyzed by inductively coupled plasma atomic emission spectrometry for total content of Si, Al, Fe, Mg, Ca, Na, K, and Mn. Key words: Elemental composition, standard soils, soil analysis
    Print ISSN: 0008-4271
    Electronic ISSN: 1918-1841
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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