西藏驱龙矿区流纹斑岩及英安流纹斑岩年代学研究及其地质意义

驱龙超大型斑岩铜矿床是冈底斯斑岩铜矿带上最为重要的矿床,矿区侵入岩较发育,但流纹斑岩及英安流纹斑岩的形成时代存在争议。在野外及岩相学观察基础上,结合LA-ICP-MS锆石U-Pb测年,获得流纹斑岩年龄值为169.9±0.61 Ma,英安流纹斑岩年龄值分别为166.0±1.8 Ma及173.8±0.56 Ma,黑云母花岗闪长岩年龄值为16.98±0.15 Ma。结合前人年代学研究,认为流纹斑岩及英安流纹斑岩可能在早侏罗世即开始活动,一直持续到晚侏罗世。而黑云母花岗闪长岩的形成时代与前人研究一致,皆为中新世。此外,驱龙矿区岩浆岩演化经历了早-晚侏罗世、中新世早期和中新世中期三个阶段,其中,中新世早期岩浆活动与成矿时代具有很好的一致性。最后认为,驱龙矿区岩浆岩活动时间与新特提斯洋俯冲阶段及印度-亚洲大陆碰撞后汇聚过程中发生的岩浆作用阶段相对应。岩浆活动与成矿受到这两大构造活动事件的影响。

Chronology and Its Geological Significance of Rhyolitic Porphyry and Dacite-rhyolite Porphyry in Qulong Ore District, Tibet

The Qulong ultra-large porphyry copper deposit is the most important deposit in Gangdise porphyry copper belt. There are many intrusive rocks in ore district, but the age of rhyolite porphyry, dacite-rhyolite porphyry is controversial. Based on the field survey and petrographic observations, combined LA-ICP-MS zircon U-Pb dating, the age of rhyolite porphyry is 169.9±0.61 Ma, dacite-rhyolite porphyries are 166.0±1.8 Ma and 173.8±0.56 Ma, and biotite granodiorite is 16.98±0.15 Ma. Based on the previous studies of chronology, it is believed that rhyolitic porphyry and dacite-rhyolite porphyry may have started to invade in the early Jurassic and lasted until the late Jurassic. The biotite granodiorites were formed in the Miocene, the same as previous studies. In addition, it is concluded that the magmatic rocks evolution experienced three stages in Qulong ore district: early-lower Jurassic, early Miocene and middle Miocene, the early Miocene magmatic activity and mineralization age have a good consistency. The activity time of the magmatic rocks in Qulong ore district corresponds to the subduction stage of the Neo-Tethyan Ocean and the magmatism stage of the convergence process after Indo-Asian collision. Magmatic activity and mineralization are influenced by these two tectonic events.