Eclogitic metasediments from the Tso Morari area (Ladakh, Himalaya): evidence for continental subduction during India-Asia convergence

Metasediments in the Tso Morari area (Ladakh, Himalaya) provide new insights into the Higher Himalayan metamorphism in the northwestern part of the Himalayan belt. Whole-rock analyses and petrologic observations show that the metasediments correspond to Fe-rich metapelites, Mg-rich metapelites, intermediate metapelites and metagreywackes of the Indian continental margin. Jadeite + chloritoid + paragonite + garnet in the Fe-rich metapelites indicate pressures of 20 ±2 kbar at temperatures of 550 ±50 °C according to major element partitioning thermobarometry, stability fields of minerals and Thermocalc P-T estimates. These results are consistent with P-T estimates on other metasediments and with the occurrence of eclogites. Subsequent retrogression at the eclogite-blueschist facies transition (from 18 to 13 kbar and 540 ±50 °C) was followed by an increase in temperature to 630 ±30 °C at amphibolite facies conditions. The metamorphic evolution is related to subduction of the Indian continental margin beneath the southern Asian margin at the onset of the Indian-Eurasian collision. Received: 17 April 1996 / Accepted: 19 February 1997