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Magnetite-sulfide-metal complexes in the Allende meteoriteA model of liquid immiscibility is presented that seemingly accounts for the sulfide-oxide-metal complexes that are present in olivine-rich chondrules in the Allende meteorite. The four major assemblages that are identified are: (1) magnetite + Ni-Fe metal; (2) magnetite + troilite + Ni-Fe metal; (3) magnetite + troilite + pentlandite + Ni-Fe metal; and (4) troilite + or - pentlandite. Specific attention is focused on oxide-metal associations and experimental data confirm earlier suggestions that magnetite results from the oxidation of an initially high-Fe-content metal alloy. Oxidation decreases the modal abundance of the Fe metal and this is accompanied by substantial increases in Ni contents which reach a maximum of approximately 70 wt % Ni. The proposed oxidation mechanism is entirely consistent with condensation of Fe-metal + olivine (Fa5) that subsequently reequilibrated at lower temperatures. Although the sulfide constituents could also have formed by the reaction of Fe-Ni metal + gaseous H2S, sulfide immiscibility under increased conditions of partial O2 pressure is the preferred process.
Document ID
19800039428
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Haggerty, S. E.
(Massachusetts Univ. Amherst, MA, United States)
Mcmahon, B. M.
(Massachusetts, University Amherst, Mass., United States)
Date Acquired
August 10, 2013
Publication Date
January 1, 1979
Subject Category
Lunar And Planetary Exploration
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: Houston, TX
Start Date: March 19, 1979
End Date: March 23, 1979
Accession Number
80A23598
Funding Number(s)
CONTRACT_GRANT: NSF EAR-78-02539
CONTRACT_GRANT: NGR-22-010-089
Distribution Limits
Public
Copyright
Other

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