新疆西昆仑塔什库尔干高压变质岩的重新厘定及其构造意义

Redefinition of High Pressure Metamorphic Rocks from West Kunlun Orogen and Its Tectonic Significance

新疆西昆仑塔什库尔干以东解体出一套"斜长角闪片麻岩-矽线石榴黑云斜长片麻岩组合"。岩石地球化学特征表明,斜长角闪片麻岩原岩为基性火山岩,具有岛弧玄武岩的特征,在构造环境判别图中(TiO_2/10-MnO-P_2O_5、Zr-TiO_2、Hf/3-Th-Nb/16),样品均落入岛弧环境;矽线石榴黑云斜长片麻岩原岩为过铝质碎屑岩,构造环境判别图(K_2O/Na_2O-SiO_2、La-Th-Sc、Th-Sc-Zr/10)显示,其形成环境为活动大陆边缘的岛弧环境;LA-ICP-MS锆石同位素年代学表明,斜长角闪片麻岩形成于早寒武世,并经历了志留纪、二叠纪、白垩纪、中新世4期岩浆热事件。该区高压变质岩的重新厘定对于探讨西昆仑的构造演化具有重要意义。

A set of ＂Grt - P1 - Hbl gneiss and Sil - Grt - Bit - P1 gneiss＂ has been disintegrated from the eastern part of Tashkurghan area in West Kunlun. According to the geochemical characteristics study, the Grt- P1- Hbl gneiss was derived from basic volcanic rocks, with the features of island-arc basalt. In the discrimination diagram, their samples are plotted in the field of islandarc basalt. The Sil -Grt -Bit -P1 gneiss was sourced from clastic rocks. In the discrimination diagram, their samples are plotted in the active continental margin and in the continental arc. According to the isotope chronology, the Grt - P1 - Hbl gneiss was formed in early Cambrian epoch. Since the formation of magma, the Grt- P1 -Hbl gneiss has experienced four notable thermal events in Silurian, Permian, Cretaceous and Miocene. The redefinition of high pressure metamorphic rocks in this area has a great significance to discussing the tectonic evolution in West Kunlun.