南天山库米什地区孔雀沟岩体年代学、岩石成因及地质意义

Geochronology,petrogenesis and geological significance of Kongquegou in Kumishi area,Southern Tianshan

库米什地区孔雀沟岩体位于南天山造山带,岩性主要为正长花岗岩,其成岩年代学、成因类型对于限定南天山洋的闭合时限具有重要意义。通过锆石U-Pb定年、全岩分析,对孔雀沟岩体进行研究。锆石U-Pb定年结果显示,孔雀沟岩体成岩年龄为295.1~296.5 Ma,属于早二叠世岩浆活动产物。岩相学与元素组成表明,孔雀沟岩体具有高分异I型花岗岩特点,具体表现为:①低w(Zr)/w(Hf)值(19~26);②较低的Zr饱和温度(749℃~802℃);③发育角闪石。综合分析认为,在早二叠世南天山洋已经闭合,孔雀沟岩体形成于后碰撞环境。此外,孔雀沟岩体岩石地球化学特征与区内同时代的矽卡岩型钨矿化成矿岩体特征相似,表明其具有一定的钨找矿潜力。

Kongquegou rock body is situated in Kumishi area of Southern Tianshan,and the lithology is mainly syenogranite.Its geochronology and petrogenesis type bear significance in defining the time of Southern Tianshan Ocean Basin closure.Zircon U-Pb isotope and whole-rock analysis were carried out to study Kongquegou rock body.Zircon U-Pb dating indicates that Kongquegou rock was formed during Early Permian(295.1-296.5 Ma)magmatism.The petrology and element composition indicate that Kongquegou rock body is characterized by high fractionated I-type granite,specifically:①low w(Zr)/w(Hf)value(19-26);②fairly low Zr saturation temperature(749℃-802℃);③development of hornblende minerals.In this study,comprehensive analysis believed that Southern Tianshan Ocean had closed before Early Permian,and Kongquegou rock body was formed in a post-collision tectonic setting.In addition,Kongquegou rock body has a similar geochemical feature with the coeval skarn W mineralization ore-forming rock body,indicating W prospecting potential.