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Hydrothermal alteration of CM carbonaceous chondrites: Implications of the identification of tochilinite as one type of meteoritic PCPPoorly characterized phases (PCP's) constitute up to 30 volume percent of some CM carbonaceous chondrites, and are therefore an important key to an understanding of the physico-chemical conditions attending matrix evolution. An iron rich form of the terrestrial phase tochilinite was recently identified as a common type of PCP. Tochilinite has the general formula 6Fe(0.9)S.5(Mg,Fe)(OH)2 and consists of alternating machinawite (FeS) and brucite ((Mg,Fe)(OH)2) sheets, with iron vacancies in the sulfide sheets. In iron rich tochilinite, ferrous hydroxide, called amakinite, replaces brucite. If CM carbonaceous kchondrites have underdone hydrothermal alteration, iron rich tochilinite, at least, probably grew from aqueous solutions characterized by low FO2, high FS2, pH 10 to 12, and at a temperature at or below 170 C.
Document ID
19850007307
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Zolensky, M. E.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1984
Publication Information
Publication: Lunar and Planetary Institute The 47th Ann. Meteoritical Soc. Meeting
Subject Category
Lunar And Planetary Exploration
Accession Number
85N15616
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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