Characterization and timing of metamorphism within the Indo-Asian suture zone, Himalayas, northern Pakistan

The Himalayas of northwestern Pakistan mark the zone of deformation and metamorphism related to the collision of India northward into Asia. Geologic mapping in one region where the boundary between the Indian and Asian plates is well-exposed is the basis for a detailed look at the nature and timing of Himalayan metamorphism. In the Upper Kaghan Valley, Indian plate rocks have been overthrust by the Kohistan Island Arc, previously accreted to Asia, along the Main Mantle Thrust (MMT). Immediately below the MMT appear a band of graphitic metapelites interpreted to relate directly to the thrusting. These rocks show metamorphism to mid-amphibolite facies conditions, with garnet-biotite geothermometry indicating temperatures of ca. 500...