Contrasting P-T paths in the eastern Himalaya, Nepal; inverted isograds in a paired metamorphic mountain belt

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doi: 10.1093/petrology/41.12.1673
Authors:Goscombe, Ben; Hand, Martin
Author Affiliations:Primary:
Adelaide University, Department of Geology and Geophysics, Adelaide, South Aust., Australia
Volume Title:Journal of Petrology
Source:Journal of Petrology, 41(12), p.1673-1719. Publisher: Oxford University Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:2000
Note:In English. 104 refs.; illus., incl. 8 tables, geol. sketch maps
Summary:Two N-NE profiles across eastern Nepal near Makala and Kangchenjunga, reveal a paired metamorphic belt of two thrust-bound metamorphic terrains of contrasting metamorphic style. The higher level one has a high T, moderate P and an anticlockwise P-T path with peak garnet-cordierite-sillimanite equilibrated at ∼ 850°C and ∼7 kbar. Underlying and below the Main Central Thrust is an inverted Barrovian sequence of high P, moderate T, and clockwise P-T path with peak garnet-K-feldspar-bytownite-sillimanite-biotite + melt ± kyanite, the highest P being ∼ 10 kbar and, but not at the same time, peak T > 700°C, i.e. a deeply buried sequence. The inverted isograds resulted from ductile over-thrusting of the hot upper sequence during prograde metamorphism, the two terrains being juxtaposed during the formation of sillimanite-biotite ± gredite layers formed at ∼ 674°C and ∼ 6 kbar. Summary compositions of garnet, cordierite, staurolite, kyanite, sillimanite, K-feldspar, biotite, muscovite, chlorite, clinopyroxene, hornblende, epidote and scapolite are listed with the original data on the WWW. [B.E.L.]
Subsections:Metamorphism: regional, dynamic
Subjects:Biotite gneiss; Gneisses; Isograds; Metamorphic belts; Metamorphic rocks; Metamorphism; Mineral assemblages; P-T conditions; P-T-t paths; Prograde metamorphism; Asia; Himalayas; Indian Peninsula; Lesser Himalayas; Nepal
Coordinates:N270000 N280000 E0880000 E0860000
Abstract Numbers:01M/2303
Record ID:2001013849
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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