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Re-Os, Rb-Sr, and O isotopic systematics of the Archean Kolar schist belt, Karnataka, IndiaThe Re-Os, Rb-Sr, and O isotopic compositions of mafic and ultramafic amphibolites, gold ores, and granitic gneisses of the circa 2700 Ma Kolar schist belt are reported which reveal at least two episodes of postmagmatic alteration that affected these systems. The Re-Os isotopic systematics of many of the belt rocks indicate that Os was introduced to the area via fluids that carried very radiogenic Os, probably from ancient crust. The Rb-Sr systematics of most of these rocks indicate that the alteration event probably occurred no later than the early Proterozoic. Samples of several komatiitic amphibolites have very Os-187-depleted compositions, indicating that open-system behavior also occurred at a much later time than the late Archean or early Proterozoic. The results suggest that the Re-Os system may have only limited utility for geochronologic applications in regions for which postcrystallization noble metal mineralization is evident.
Document ID
19900030429
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Walker, Richard J.
(Carnegie Institution of Washington Washington, DC, United States)
Shirey, Steven B.
(Carnegie Institution of Washington Washington, DC, United States)
Hanson, Gilbert N.
(New York, State University Stony Brook, United States)
Rajamani, V.
(Jawaharlal Nehru University New Delhi, India)
Horan, Mary F.
(USGS Reston, VA, United States)
Date Acquired
August 14, 2013
Publication Date
November 1, 1989
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 53
ISSN: 0016-7037
Subject Category
Geophysics
Accession Number
90A17484
Funding Number(s)
CONTRACT_GRANT: NSF EAR-87-20712
CONTRACT_GRANT: NAG9-855
CONTRACT_GRANT: NAGW-398
CONTRACT_GRANT: NSF INT-85-19507
Distribution Limits
Public
Copyright
Other

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