Ages of Alpine tectonometamorphic events in the northwestern Himalaya (northern Pakistan) by ³⁹Ar/⁴⁰Ar method

Abstract

The main tectonometamorphic alpine events which occurred in the western part of the western Himalayan virgation at south of the main suture, in northern Pakistan, are dated by the 39 Ar/ 40 Ar method. These events are as follows: (1) the blueschist metamorphism (80 ± 5 Ma) present in tectonic/ophiolititic melanges along the suture (this event occurred during an early subduction or obduction stage) (2) the alpine barrovian metamorphism (50–30 Ma) developed in the sedimentary cover and orthogneisses of the Indian Plate during the postcollisional northward underthrusting of this plate below Asia, and (3) the emplacement of postmetamorphic leucogranites (23 Ma) resulting from the melting of the Indian crust during the climax of the alpine metamorphism.