Paleozoic evolution of the Qimantagh magmatic arcs, Eastern Kunlun Mountains: Constraints from zircon dating of granitoids and modern river sands

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• 作者：Wei Li ; Franz Neubauer ; Yongjiang Liu ; Johann Genser ; Shoumai Ren ; Guoqing Han ; Chenyue Liang
• 关键词：Paleozoic ; U&ndash ; Pb ; Qimantagh ; Paleo-Tethyan Ocean ; Magmatic arc ; Eastern Kunlun
• 刊名：Journal of Asian Earth Sciences
• 出版年：2013
• 出版时间：15 November, 2013
• 年：2013
• 卷：77
• 期：Complete
• 页码：183-202
• 全文大小：8034 K

文摘

The Qimantagh area, located along the northwestern margin of the Eastern Kunlun Mountains at the northern margin of the Tibetan plateau, is one of the less studied regions of Central Asia/Western China due to its remote location. In this study, we present new LA-ICP-MS U-Pb zircon ages from granitoids and modern sands collected at the northern slope of Qimantagh. Seven samples of diorites, granites and orthogneiss gave a variety of ages: (1) four samples from Wotoushan yield weighted average ages of 484.6 ¡À 7.3, 439.0 ¡À 5.9, 424.0 ¡À 3.5 and 261.5 ¡À 3.7 Ma; (2) the weighted average ages of two granite samples from Shuangshixia are 461.7 ¡À 8.4 and 428.6 ¡À 4.4 Ma; and (3) the diorite sample from Naitoushan shows the weighted average age of 446.2 ¡À 3.6 Ma. Early Paleozoic ages dominate while one sample gives a Late Paleozoic age. Together, the new ages representing distinct steps of Paleozoic magmatic evolution in the Qimantagh area.To assess further the overall composition of the North Qimantagh block, zircons of three modern sands samples from rivers draining the Qimantagh area into the Qaidam basin yield a wide age range of 3118-211 Ma. Based on new zircon ages from modern river-sand samples and granitoids, combined with previous geochronological age data, we suggest that two stages of tectonic evolution existed in the Qimantagh area: (1) northward subduction of the Qimantagh Ocean (513-420 Ma); (2) continental arc setting (290-257 Ma).