新疆中天山古生代侵入岩浆序列及构造演化

The Paleozoic Intrusive Magmatic Sequence and Tectonic Evolution of Central Tianshan Mountains in Xinjiang,NW China

新疆中天山构造岩浆带是中亚造山带的重要组成部分,广泛分布着古生代花岗质侵入体。本研究重点对中天山南缘巴音布鲁克及巴伦台地区的花岗质侵入体进行了LA-ICP-MS锆石U-Pb测年,并获得了岩体侵位年龄由老到新分别为463±3Ma(石英闪长岩)、437±5Ma(石英闪长岩)、424±3Ma(二长花岗岩)、383±4Ma(二长花岗岩)、356±3Ma(二长花岗岩)和303±5Ma(正长花岗岩)。综合区域地质分析认为,中天山古生代侵入岩浆活动可分为四个构造岩浆演化阶段:(1)晚寒武世—晚奥陶世阶段,Terskey洋盆和南天山洋盆自新元古代打开形成广阔洋盆,Terskey洋盆在晚寒武世开始初次俯冲,于晚奥陶世洋盆闭合,南天山洋盆于早奥陶世初次俯冲,具有自西向东、由早到晚的俯冲特点;(2)早志留世—中泥盆世阶段,南天山洋盆持续向北俯冲,该阶段北天山洋开始向南侧俯冲,在伊犁地块北缘形成了弧岩浆;(3)晚泥盆世—早石炭世阶段,南天山洋盆闭合于晚泥盆世末期,在早石炭世中晚期进入残余洋盆演化阶段;(4)晚石炭世—早二叠世阶段,该阶段为后碰撞伸展环境,区域上为陆内演化阶段。

The Central Tianshan Mountains tectonic magmatic belt widely distributed with the Paleozoic granitoids, which is an important part of the Central Asian Orogenic Belt （CAOB） in Xinjiang. The LA-ICP-MS zircon U-Pb dating was carried out on granitoids from Bayinbuluke and Baluntai area in south of central Tianshan Mountains, and the age were 463 ± 3Ma （quartz diorite）, 437 ± 5Ma （quartz diorite）, 424 ± 3Ma （monzogranite）, 383 ± 4Ma （monzogranite）, 356 ± 3Ma （monzogranite） and 303 ± 5 Ma （syenogranite）, respectively. Through synthetically analyzed, the Paleozoic intrusive magmatism in the central Tianshan Mountain can be divided into four stages of tectonic magmatic evolution. The first stage is from late Cambrian to late Ordovician. The Terskey ocean basin and southern Tianshan ocean basin opened to form vast ocean basins in the Neoproterozoic. The Terskey ocean basin began to subduct in the late Cambrian and closed in the late Ordovician, and the southern Tianshan ocean basin northward subduction began in the early Ordovician from west to east gradually. The second stage is from early Silurian to middle Devonian. The southern Tianshan ocean basin continued to subduction northward, and the northern Tianshan ocean basin began to subduction southward and formed arc magma in the northern edge of the Yili block. The third stage is from late Devonian to early Carboniferous. The southern Tianshan basin closed at the end of the Late Devonian and started the residual oceanic basin in the middle and late of early Carboniferous. The last stage is from late Carboniferous to early Permian with post-collisional orogenic environment and continental evolution in region.