西藏聂荣微陆块奥陶纪和侏罗纪岩浆事件的年龄证据

为了加深对班公湖-怒江缝合带构造演化过程的认识，选择聂荣微陆块内的花岗质片麻岩和花岗闪长质片麻岩中的锆石进行LA-ICP-MS U-Pb定年，结果主要显示两组206Pb/238U的加权平均年龄:一组为453.7±2.5 Ma; 另一组为176.6±1.1 Ma和178.04±0.8 Ma.花岗质片麻岩中黑云母和花岗闪长质片麻岩中白云母的40Ar-39Ar定年结果显示，坪年龄分别为161.8±1.1 Ma和178.9±1.2 Ma.上述年龄结果表明，聂荣微陆块主要经历了晚奥陶世和早侏罗世两期岩浆事件，这两期岩浆事件分别与冈瓦纳大陆北缘早古生代的造山作用和班公湖-怒江洋壳的俯冲闭合存在密切的动力学关系. 

Geochronological Evidence of Ordovician and Jurassic Magmatic Events in Nyainrong Microcontinent,Tibet

In order to deepen our knowledge and understanding about the tectonic evolution of the Bangonghu-Nujiang suture zone(BNS), zircon U-Pb dating was conducted for granitic gneiss and granodioritic gneiss of Nyainrong microcontinent by LA-ICP-MS in this study. Results show two groups of average zircon U-Pb ages, with one of 453.7±2.5 Ma, and the other of 176.6±1.1 Ma and 178.04±0.8 Ma. 40Ar-39Ar dating was conducted for biotite from granitic gneiss and muscovite from granodioritic gneiss in Nyainrong microcontinent.The 40Ar-39Ar plateau ages yield 161.8±1.1 Ma and 178.9±1.2 Ma, respectively, showing that the study area experienced the Late Ordovician and the Early Jurassic magmatic events. Combined with field condition and study results, it is suggested that the Ordovician magmatic event was related to the Early Paleozoic orogeny which could be caused by proto-Tethyan oceanic subduction along Gondwana continental margin, and the Jurassic magmatic event was related to the subduction and closure of the Bangong-Nujiang oceanic crust.