Garnetiferous metamorphic rocks in Jaspa granite, Himachal Pradesh, India: Implication of Tethyan Himalayan metamorphism and tectonics

Abstract

Studies on the magmatic enclaves, pelitic xenoliths and host Jaspa granite pluton outcropped in the Lahaul area, NW Himalaya, India illustrate that the rocks have undergone garnet-grade metamorphism. The P-T pseudosection modelling shows that the met-amorphic mineral assemblage is stable in the P-T range ~4.5-7.3 kbar and ~440-500°C, matching quite well with the results obtained from the conventional geothermobarometers (5.7-8.6 kbar and 409-531°C). The observed garnet-grade metamorphism in and around the Jaspa pluton is proposed to be due to lo-calized perturbation of high-temperature isotherms in the Tethys Himalaya, as a consequence of the Cenozoic tectono-thermal event during Himalayan orogeny. Fur-ther, the Haimanta group of Tethys Himalayan rocks in the Lahaul area has been interpreted to have attained right-way-up metamorphic field gradient.