Oxygen fugacity of upper mantle beneath Dharwar craton, India
Abstract
Oxygen fugacity (fO2) of the Earth's upper mantle has an important influence on chemical differentiation, mantle metasomatism and speciation of fluids in the upper mantle. The oxygen fugacities of natural spinel/garnet peridotites in upper mantle show a trend towards more reducing conditions with increasing depth [1]. We studied the subcratonic lithosperic mantle xenoliths (7 peridotitic and 3 eclogitic) from the kimberlites of Dharwar craton over a pressure range from 2.4 to 6.6 GPa and a temperature range of 841 to 1430 oC. Here, we report the oxidation state of the upper mantle (70-200 km) beneath the Dharwar craton using Mössbauer spectroscopy and by charge-balance using electron probe microanalysis data.
Major, minor, and trace element compositions of garnet and clinopyroxene show metasomatically enriched materials in the suite over the studied pressure range. Fe3+ content in spinel/garnet is found to vary between 0.02 and 0.13 and has a Fe3+/ΣFe ratio from 0.02 to 0.32. Oxygen fugacity (ΔlogfO2[FMQ]) of xenoliths samples from Dharwar region varies from -2.5 to -6.9 over the sampled pressure interval and show decreasing trend of ΔlogfO2[FMQ] with increasing depth which is in agreement with previous studies [2,3]. [1] Frost and McCammon, Annu. Rev. Earth Planet. Sci. (2008)36389-420. [2] Woodland and Koch EPSL (2003) 214 295-310. [3] Yaxley et al Lithos(2012) 140-141 142-151.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V11D0056P
- Keywords:
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- 1030 Geochemical cycles;
- GEOCHEMISTRYDE: 1042 Mineral and crystal chemistry;
- GEOCHEMISTRYDE: 3612 Reactions and phase equilibria;
- MINERALOGY AND PETROLOGYDE: 3651 Thermobarometry;
- MINERALOGY AND PETROLOGY