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Relationships between oxygen fugacity and metasomatism in the Kaapvaal subcratonic mantle, represented by garnet peridotite xenoliths in the Wesselton kimberlite, South Africa

Citation

Hanger, BJ and Yaxley, GM and Berry, AJ and Kamenetsky, VS, Relationships between oxygen fugacity and metasomatism in the Kaapvaal subcratonic mantle, represented by garnet peridotite xenoliths in the Wesselton kimberlite, South Africa, Lithos, 212-215 pp. 443-452. ISSN 0024-4937 (2015) [Refereed Article]

Copyright Statement

Copyright 2014 Elsevier B.V.

DOI: doi:10.1016/j.lithos.2014.09.030

Abstract

A suite of 12 peridotite xenoliths from the Wesselton kimberlite was studied and found to sample the subcratonic lithospheric mantle over a pressure range from 3.6 to 4.7 GPa and a temperature range of 880 to 1120 °C. Major, minor and trace element compositions indicate that both metasomatised and un-metasomatised samples are present over this pressure range. Fe3 +/∑ Fe in garnet from four xenoliths was determined using Fe K-edge XANES spectroscopy, enabling the redox state of the sampled subcratonic mantle to be determined for three garnet bearing samples. ΔlogfO2[FMQ] varied from 0 to − 3.3 over the sampled pressure interval, with the un-metasomatised samples falling within the global trend of decreasing ΔlogfO2[FMQ] with increasing depth. Superimposed on this was an oxidation trend, at higher pressures (≥ 4.5 GPa), with ΔlogfO2 increasing by 1.5 to 2 units in the metasomatically enriched samples, indicating a clear link between metasomatism and oxidation. One potential source of this oxidation is a carbonated silicate melt, which will increase in carbonate content as ΔlogfO2 increases. Mantle minerals affected by such a melt have the potential to shift from the field of diamond stability into that of carbonate, threatening the stability of diamond.

Item Details

Item Type:Refereed Article
Keywords:XANES, garnet peridotite xenoliths, Kaapvaal Craton, oxygen fugacity, metasomatism
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Geochemistry not elsewhere classified
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
ID Code:97876
Year Published:2015
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2015-01-20
Last Modified:2016-05-24
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