Magmatic records from the Karakoram terrane: U–Pb zircon ages from granites and modern sediments in the Nubra Valley, NW Himalaya

The Karakoram terrane is a sliver of peri-Gondwana continental crust preserved within the Karakoram and Saltoro ranges in Ladakh, India. It became a part of Eurasia during the Jurassic, and until Late Cretaceous its southern margin was an active continental margin represented by the Karakoram (Arc) Batholith. Its magmatism is thought to be extinguished during Late Cretaceous by collision with the Shyok ophiolite, however, geochronological data are limited. The Karakoram terrane is a key element in the geodynamics of Himalaya and more studies are needed to improve geological understanding and tectonic evolution of the southern margin of Eurasia pre- and post- final continental collision with the Indian continent. We present petrographic, geochemical, and geochronological observations for anatectic magmatism which formed granitic intrusions within the terrane at c. 14 Ma and 12 Ma. Results from detrital zircon dating of modern sediments from the Karakoram terrane reveal three distinct age populations at c. 108, 82, and 13 Ma which correspond to known geological events. Current geochronological data for the Karakoram terrane indicate presence of two major magmatic episodes, the first occurred during Jurassic–Cretaceous and was related to subduction processes, and second, occurred during the Miocene and was related to the anatexis of the Karakoram lithosphere upon the terminal continental collision. The intervening magmatic events are still uncharacterised.