新疆西天山菁布拉克基性杂岩体闪长岩锆石SHRI MP定年及其地质意义  

Shrimp zircon U-Pb dating of diorite from Qingbulake basic complex in western Tianshan Mountains of Xinjiang and its geological significance

作　　者：张作衡[1] 王志良[1] 王彦斌[2] 左国朝[3] 王龙生[1] 吕林素[4] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]中国地质科学院地质研究所,北京100037 [3]甘肃省地质调查院,甘肃兰州730000 [4]中国地质大学地质过程与矿产资源国家重点实验室,北京100083

出　　处：《矿床地质》2007年第4期353-360,共8页Mineral Deposits

基　　金：国家自然科学基金项目(40402012);地质调查项目(1212010634001;1212010561603-3);地质过程与矿产资源国家重点实验室科学基金(GPMR200627)资助

摘　　要：文章对新疆西天山特克斯县菁布拉克基性杂岩体中辉石闪长岩样品中的锆石进行了SHRIMP U-Pb定年研究,获得了(434.4±6.2)Ma的和谐年龄,该结果表明菁布拉克岩体的侵位时间为早志留世。结合岩石地球化学分析所揭示的形成环境信息和最新的区域地质资料,认为菁布拉克岩体的形成与早志留世到早石炭世发生的南天山洋向北与中天山板块的俯冲作用密切相关,岩浆显现出的岛弧岩浆特点可能是由于洋壳向亏损地幔的俯冲所引起的。The Qingbulake mafic-ultramafic rock belt is distributed in we.stem Tianshan Mountains of Xinjiang. There are about ten intrusions in the Qingbulake rock belt, with Qingbulake being the largest one. As a part of the copper＇nickel sulfide metallogenic belt related to mafic-ultramafic intrusions in northern Xinjiang, it was previously considered to be formed in a tectonic environment similar to that of the Karatunk complex on the southern margin of the Altay orogenic belt and the Huangshandong complex in eastern Tianshan, i.e., in a post-collisional extensional environment. In this study, the authors obtained the high precise SHRIMP zircon U-Pb age of （434,4 ± 6.2） Ma for the pyroxene diorite facies of the Qingbulake basic complex. This age represents the diorite formed during Early and Middle Silurian. Geochemical studies of the Qingbulake basic complex show that it is characterized by low content of Ti, depletion of Nb and Ta and enrichment of large lithosphile elements and slight enrichment of LREE. The magma also displays some features of inland arc magma. The magma was probably derived from the MORB type depleted mantle, and was not or was even slightly contaminated by the crust or the wall rock during the emplacement. Combined with the recent research achievements on regional tectonic evolution, it is considered that the formation of the complex might have been closely related to Early Silurian subduction of the southern Tianshan oceanic crust to central Tianshan plate.

关 键 词：地球化学 基性杂岩体 锆石SHRIMP测年 菁布拉克 西天山 

分 类 号：P597.3[天文地球—地球化学]