Abstract

The two parallel belts of Miocene granite that extend along much of the Himalaya differ in age, petrogenesis, and emplacement style. We suggest that their origin is linked to shear heating on a continuously active decollement that cuts through previously metamorphosed Indian supracrustal rocks that were transformed into basement during the initial stages of the Indian-Asian collision. Numerical simulations assuming a shear stress of 30 MPa indicate that initiation of slip on the Himalayan thrust at 24 Ma could trigger discontinuous melting reactions leading to formation of the High Himalayan granite chain from 24 to 20 Ma and the North Himalayan belt from 18 to 12 Ma. This model result agrees well with observation as do model predictions regarding emplacement style and location.

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