University of Tasmania
Browse

File(s) under permanent embargo

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

journal contribution
posted on 2023-05-26, 11:28 authored by Hanger, BJ, Yaxley, GM, Berry, AJ, Vadim Kamenetsky
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 ¬¨‚àûC. Major, minor and trace element compositions indicate that both metasomatised and un-metasomatised samples are present over this pressure range. Fe3 +/‚Äöv†v´ 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. ˜ívÆlogfO2[FMQ] varied from 0 to ‚Äöv†v¿ 3.3 over the sampled pressure interval, with the un-metasomatised samples falling within the global trend of decreasing ˜ívÆlogfO2[FMQ] with increasing depth. Superimposed on this was an oxidation trend, at higher pressures (‚Äöv¢‚Ä¢ 4.5 GPa), with ˜ívÆlogfO2 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 ˜ívÆlogfO2 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.

History

Publication title

Lithos

Volume

212-15

Pagination

443-452

ISSN

244937

Department/School

Institute for Marine and Antarctic Studies (IMAS)

Publication status

  • Published

Repository Status

  • Restricted

Usage metrics

    University Of Tasmania

    Categories

    No categories selected

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC