Glaucophane-bearing eclogites in the Tso Morari dome (eastern Ladakh, NW Himalaya)

Abstract

Lenses of glaucophane-bearing eclogites have been discovered within the Cambro-Ordovician metagranitic basement and in the Permian metasedimentary cover of the Tso Morari dome (eastern Ladakh, India). Petrological and thermobarometrical evidence shows that these rocks underwent a high-pressure event (P> 16 kbar, probably near 20±3 kbar) associated with relatively low-temperature conditions (T = 580±60 °C). The beginning of decompression was isothermal down to l 1 ± 2 kbar. Subsequently, temperature increased to 610±70°C under amphibolite-facies conditions. This record of high-pressure and relatively low-temperature metamorphism in the Himalayan belt implies that an early subduction of the whole NW part of the Indian continental margin to a minimum depth of 70+10 km occurred during the India-Asia convergence. Two different units can be distinguished in the Higher Himalaya of Ladakh-Zanskar, recording two successive and distinct orogenic events: (i) the North Himalayan Massif related to the continental subduction and (ii) the High Himalayan Crystalline slab related to the intracontinental subduction.