EXTENDED ABSTRACTS: 19TH HIMALAYA-KARAKORAM-TIBET WORKSHOP, 2004, NISEKO, JAPAN Ion microprobe U-Pb ages of the Khunjerab granodiorite and some granitoids from Karakoram, Pakistan Masatsugu Ogasawara† *, Tahseenullah Khan‡ , Firdous Khan‡ , Noriko Kita† and Yuichi Morishita† † Geological Survey of Japan/AIST, Tukuba Central 7, Tsukuba, 305-8567, JAPAN ‡ Geological Survey of Pakistan, Islamabad, PAKISTAN * To whom correspondence should be addressed. E-mail:
[email protected] .................................................................................................................................................................................................................................................................... The Karakoram block was located at the southern margin of Asian 206Pb/238U ages of the zircons range from 107 to 120 Ma, with mean continent before the Late Cretaceous amalgamation of the value of 112 Ma. Further ion microprobe analysis will be perform Kohistan block to Asia. The northward subduction of the ocean to obtain statistically more precise age and to search inherited under the Asian continent was considered to form Early core of zircons from the Khunjerab granodiorite. Cretaceous continental arc magmatism in the Karakoram block. Ogasawara et al. (1992) obtained K-Ar hornblende and The Karakoram Batholith is a major granitic body in the biotite ages, 107±5 Ma and 96.9±4.8 Ma, respectively. Zircons Karakoram block, extending from Baltoro to Chitral regions. were separated from the same sample for the K-Ar dating. Treloar However, several smaller granitic bodies are present to north of et al. (1989) presented two K-Ar biotite ages of 105±5 Ma and the Karakoram Batholith, which comprise the Khunjerab-Tirich 107±5 Ma for the Khunjerab granodiorite. The biotite age of Mir granite belt. Ogasawara et al. (1992) investigated several Ogasawara et al.