Metamorphic evolution of peliticasemipelitic granulites in the Kon Tum massif (south-central Vietnam)

Pelitic and semipelitic anatectic granulites form one of the major lithological units in Kan Nack complex of the Kon Tum massif (in south-central Vietnam), which comprises HT metamorphic and magmatic rocks including granulites and charnockites is classically regarded as the older part of the Gondwan...

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Bibliographic Details
Published in:Journal of geodynamics 2013-09, Vol.69, p.148-164
Main Authors: Tich, Vu, Leyreloup, Andrey, Maluski, Henry, Lepvrier, Claude, Lo, Chinh-hua, Vuong, Nguyen
Format: Article
Language:English
Subjects:
Cooling
Evolution
Heating
Massifs
Metamorphic
Plagioclase
Rocks
Vietnam
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Summary:Pelitic and semipelitic anatectic granulites form one of the major lithological units in Kan Nack complex of the Kon Tum massif (in south-central Vietnam), which comprises HT metamorphic and magmatic rocks including granulites and charnockites is classically regarded as the older part of the Gondwana-derived Indosinia terrain. Metamorphic evolution study of pelitic granulite, the most abundant among granulites exposed in this massif, facilitates to understand that tectonic setting take place during the Indosinian time. The paragenetic assemblages, mineral chemistry, thermobarometry and PaT evolution path of peliticasemipelitic granulites from Kon Tum massif has been studied in detail. Petrographic feature demonstrates that the pelitic granulite experienced prograde history, from pregranulitic conditions in the amphibolite facies up to the peak granulitic assemblages. Successive prograde reactions led to the temperature-climax giving rise to assemblages with cordierite-hercynite and cordierite-hercynite-K-feldspar. Then, as attested by the mineralogic association occurring in cordieritic coronas, these rocks have been affected by retrograde conditions coeval with a decrease of the pressure. Thermobarometic results show that the highest temperature obtained by ksp/pl thermometry is 850 degree C and the highest pressure obtained by GASP (Garnet Alumino-Silicate Plagioclase) is 7.8 kbar. The obtained clockwise PaT evolution path involving heating decompression, then nearly isothermal decompression and nearly isobar cooling conditions shows that high temperaturealow pressure metamorphism of the studied pelitic anatectic granulites of Kan Nack complex occurred possibly in extensional setting during the Indosinian orogeny of 260a240 Ma in age.
ISSN:0264-3707
DOI:10.1016/j.jog.2012.03.013