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The timing and mechanism of depletion in Lewisian granulitesLarge Ion Lithophile (LIL) depletion in Lewisian granulites is discussed. Severe depletions in U, Th, and other LIL have been well documented in Lewisan mafic and felsic gneisses, but new Pb isotopic analyses show little or no depletion in lithologies with high solidus temperatures, such as peridotite. This suggests that LIL transport in this terrane took place by removal of partial melts rather than by pervasive flooding with externally derived CO2. The Pb and Nd isotopic data gathered on these rocks show that the depletion and granulite metamorphism are distinct events about 250 Ma apart. Both fluid inclusions and cation exchange geothermometers date from the later metamorphic event and therefore have little bearing on the depletion event, suggesting a note of caution for interpretations of other granulite terranes.
Document ID
19880020825
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Cohen, A. S.
(Cambridge Univ. (England), United States)
Onions, R. K.
(Cambridge Univ. (England), United States)
Ohara, M. J.
(University Coll. of Wales Aberystwyth., United States)
Date Acquired
September 5, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Lunar and Planetary Inst., Workshop on the Growth of Continental Crust
Subject Category
Geophysics
Accession Number
88N30209
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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