Oxygen isotope compositions of Miocene Garam Chashma granites, Trans-Himalayas (Hindukush Range), North Pakistan

Abstract

The Garam Chashma granites in the Hindukush Range (Trans-Himalayas) on the southern margin of the Asian plate, northwestern Pakistan, are peraluminous with a restricted SiO₂ range and K-Ar biotite ages of 20-18 Ma. Their δ¹⁸O values range between 11.48 and 12.72‰, which represent the S-type nature. The K-Ar ages and petrological characteristics of Garam Chashma granites are similar to those of Pakistan, India and Nepal Higher Himalayan S-type granites. Since most of the granitic rocks in the Trans-Himalayas are I-type with ages from 100 to 40 Ma, the Garam Chashma granite are considered to be formed by the similar source and at the same time as the other Higher Himalayan S-type granites.