Late Pan-African magmatism in the Himalaya: new geochronological and geochemical data from the Ordovician Tso Morari metagranites (Ladakh, NW India)

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State: Serval
Version: Final published version
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State: Serval
Version: Final published version
Serval ID
serval:BIB_8230EDD49B4B
Type
Article: article from journal or magazin.
Collection
Publications
Title
Late Pan-African magmatism in the Himalaya: new geochronological and geochemical data from the Ordovician Tso Morari metagranites (Ladakh, NW India)
Journal
Schweizerische Mineralogische und Petrographische Mitteilungen
Author(s)
Girard M., Bussy F.
ISSN
0036-7699
Publication state
Published
Issued date
1999
Peer-reviewed
Oui
Volume
79
Pages
399-418
Language
english
Abstract
Two granitic plutons, the Tso Morari gneiss and the Rupshu metagranite,
crop out in the Tso Morari area. The Polokongka La granite, classically
interpreted as a young intrusion in the Tso Morari gneiss, has been
recognized as the undeformed facies of the latter. Conventional isotope
dilution U-Pb zircon dating on single-grain and small multi-grain
fractions yielded magmatic ages of 479 +/- 2 Ma for the Tso Morari
gneiss and the Polokongka La granite, and 482.5 +/- 1 Ma for the Rupshu
granite. There is a great difference in zircon morphology between the
Tso Morari gneiss (peraluminous type) and the Rupshu granite (alkaline
type). This difference is confirmed by whole-rock chemistry. The Tso
Morari gneiss is a typical deformed S-type granite, resulting from
crustal anatexis. On the other hand, the Rupshu granite is an
essentially metaluminous alkali-calcic intrusion derived from a
different source material. Data compilation from other Himalayan
Cambro-Ordovician granites reveals huge and widespread magmatic activity
all along and beyond the northern Indian plate between 570 and 450 Ma,
with a peak at 500-480 Ma. A major, continental-scale tectonic event is
required to generate such a large magmatic belt; it has been tentatively
compared to the Variscan post-orogenic extensional regime of Western
Europe, as a late evolution stage of a Pan-African orogenic event.
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01/10/2012 20:07
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