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11	Redox - pressure - temperature conditions in the continental upper mantle in relation to C-O-H fluid speciation Goncharov, Aleksey 08 March 2012 (has links) (PDF) The thesis is based on a petrologic and geochemical study of mantle xenoliths from the central Siberian craton and the Baikal-Mongolia region of central Asia. Its goal is to establish the redox regime of the lithospheric mantle in these two domains with distinct tectonic settings and age and relate it to thermal regime and the speciation of C-0-H fluids. Oxygen fugacity is calculated based on Fe2+/Fe3+ ratios in spinel and garnet of mantle peridotites obtained by Mössbauer spectroscopy. The study deals with the following topics: (i) microstructures, chemical and mineralogical composition of the xenoliths; (ii) Fe2+/Fe3+ ratios in minerals by Mössbauer spectroscopy; (iii) equilibration temperatures and pressures using mineral thermo-barometry; (iv) oxygen fugacity from mineral compositions using oxybarometry; (v) proportions of molecular components in C-0-H fluids coexisting with the studied rocks. The three main conclusions of this study are: (1) Oxygen fugacity in the lithospheric mantle in the central Siberian craton decreases from +1 to -4 ΔlogʄO2 (FMQ) at depths from 70 to 220 km and shows significant lateral variations. (2) The lithospheric mantle beneath the Baikal-Mongolia region shows important redox heterogeneities, with a sharp decrease in oxygen fugacity (from +0 to -3 AlogfO2 (FMQ)) during the transition from the spine! to garnet facies peridotites at 50 to 90 km. (3) The speciation of C-O-H fluids changes with depth from essentially H2O-CO2 in the shallow lithospheric mantle to H2O-CH4 at the lithosphere-asthenosphere boundary regardless of the thermal state and the thickness of the lithosphere Mantle Peridotite Redox Oxygen fugacity Xenolith Mössbauer spectrometry Craton Geochemistry
12	Eclogites and eclogites: Oxygen isotope evidence of a shared subduction origin for Franciscan eclogites and Moses Rock eclogite xenoliths Hoover, William F. 03 June 2014 (has links) No description available. Petrology Geochemistry Geology Geological eclogite Franciscan Colorado Plateau Navajo Volcanic Field xenolith Moses Rock oxygen isotope metamorphic petrology garnet zoning diatreme subduction accretionary wedge California Four Corners

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Redox - pressure - temperature conditions in the continental upper mantle in relation to C-O-H fluid speciation

Eclogites and eclogites: Oxygen isotope evidence of a shared subduction origin for Franciscan eclogites and Moses Rock eclogite xenoliths