西藏冈底斯西部地区印支期闪长岩的特征及其地质意义

The discovery and significance of the Indosinian diorites in western Gangdise,Xizang

对西藏冈底斯西部措勤县打加错地区辉石角闪二长闪长岩进行了LA-ICP-MS锆石U-Pb法定年及岩石地球化学研究,结果表明:辉石角闪二长闪长岩的结晶年龄为207.3±3.6Ma,其物质来源与下地壳基性熔岩及上地幔的部分熔融有关,是特提斯洋在晚印支期仍在俯冲的证据。该印支晚期侵入岩系首次在南冈底斯带西侧发现,对研究冈底斯带在晚印支期的构造岩浆演化具有重要意义。

The determinations of LA-ICP-MS zircon U-Pb dating,isotopic compositions and major elements give a magmatic crystallization age of 207.3 ± 3.6 Ma for the pyroxene amphibole monzodiorite from the Daggyai Lake area,Coqen,western Gangdise,Xizang.The origin of matter may be related with the lower crustal basic lava and partial melting of the upper mantle.The late Indosinian intrusive rocks discovered for the first time in western Gangdise were formed in the orogenic tectonic setting,and attested to the continuous subduction of the Tethyan Ocean during the late Indosinian.The findings in this study will provide useful approaches to the tectonic evolution of the Gangdise region during the late Indosinian.