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Kabbaldurga-type charnockitization: A local phenomenon in the granulite to amphibolite grade transition zoneIn the deeply eroded Precambrian crust of South India and Sri Lanka, a series of spectacular exposures shows progressive development of coarse-grained charnockite through dehydration of amphibolite grade gneisses in different arrested stages. At Kabbaldurga, charnockitization of Archaean grey biotite-hornblende gneisses occurred about 2.5 Ga ago and evidently was induced by the influx of external carbonic fluids along a system of ductile shears and the foliation planes. The results of oxygen isotope thermometry and of geothermobarometry in adjacent areas indicate a P-T regime of 700 to 750 C and 5 to 7 kb. The decrease of water activity in the fluid infiltrated zones caused an almost complete breakdown of hornblende and biotite and the new growth of hypersthene. Detailed petrographic and geochemical studies revealed marked changes in mineralogy and chemistry from granodioritic to granitic which document the metasomatic nature of the process.
Document ID
19890012870
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Raith, M.
(Bonn Univ.)
Staehle, H. J.
(Bonn Univ.)
Hoernes, S.
(Bonn Univ.)
Date Acquired
September 5, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Lunar and Planetary Inst., Workshop on the Deep Continental Crust of South India
Subject Category
Geophysics
Accession Number
89N22241
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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