Abstract

The timing of the prograde metamorphism of continental crust buried during the collision of India and Eurasia is of importance to our understanding of the mechanics of mountain building and crustal metamorphism. Our knowledge of the Himalaya indicates that continental collision (at 55–50 Ma) culminated in crustal melting and leucogranitic magmatism at 24–18 Ma. However, the timing of events in the intervening 30 m.y. is poorly understood. Here we present Sm-Nd isotope analyses of garnets from the Zanskar Himalaya that also preserve information on crustal and orogenic evolution during that period. The prograde P-T-t paths indicate that heating and burial (from 6 to 10 kbar) continued until at least 25–30 Ma and imply peak temperatures (∼700 °C) close to those necessary to cause the crustal melting in the Himalaya at ca. 20 Ma, without a requirement for additional heat sources such as shear heating on major crustal shear zones. The persistence of high temperatures as late as 20 Ma in the Himalaya may be related to postcollisional thrusting south of the suture zone and within the Indian plate at 40–35 Ma.

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