Geobarometric constraints on the depth of emplacement of granite from the Ladakh batholith, Northwest Himalaya, India.

Abstract

The Ladakh batholith is exposed along the 600 km long and 20 to 80 km wide NW-SE trending Ladakh range north of the Indus-Tsangpo Suture Zone. It was emplaced with in an unmetamorphosed thick pile of mafic and felsic volcanics, ultramafics and sediments of Upper Cretaceous-Eocene age (Dras Volcanics, Khardung Volcanics). The granites from the Ladakh batholith (60 Ma phase) within the Leh-Khardung La and Sakti-Chang La sections (samples collected between altitude of 3600 M and 5440 M above mean sea level) have been estimated for pressure and temperature of crystallization employing the hornblende geobarometer of Schmidt (1992) and hornblende-plagioclase geothermometer of Blundy and Holland (1990), with the results of pressure of 254±67 MPa and temperature of 695±20°C. Therefore, these granites were solidified at a depth of 8.6±2.3 km suggesting an unroofing of this thickness in this region.