Rifting, subduction and collisional records from pluton petrogenesis and geochronology in the Hindu Kush, NW Pakistan

Abstract

New U-(Th)/Pb geochronology and geochemical analyses of plutonic bodies in the Hindu Kush range, NW Pakistan, provide insight on the crustal growth and tectonic evolution of the southern Eurasian margin. These new data outline a protracted magmatic history that spans the Cambrian to the Neogene (ca. 538 to 23Ma) and record a variety of petrogenetic associations variably influenced by within plate, volcanic arc, and collision tectonic environments. The Kafiristan pluton (538±4 to 487±3Ma) yields geochemical signatures consistent with extensional plutonism and rifting of the Hindu Kush terrane from Gondwana. The Tirich Mir (127±1 to 123±1Ma) and Buni-Zom (110±1 to 104±1Ma) plutons have geochemical signatures that can be attributed to a subduction related continental volcanic arc system that developed along the southern margin of Eurasia in the Mesozoic. The Garam Chasma pluton, the youngest body in the study area (27.3±0.5 to 22.8±0.4Ma), yields a geochemical signature consistent with widespread anatexis during crustal thickening related to the development of the Himalaya. The present geochemical and geochronological analysis from the Hindu Kush have produced important new constraints on the timing of tectonic events and variable tectonic settings along the south Eurasian margin before and after the continued India–Asia collision.