西天山北部晚古生代火山-浅侵位岩浆岩^(40)Ar/^(39)Ar同位素定年  

^(40)Ar/^(39)Ar chronological study of Late Paleozoic volcanic hypabyssal igneous rocks in western Tianshan, Xinjiang

作　　者：赵振华[1] 白正华[1] 熊小林[1] 梅厚钧[1] 王一先[1] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640

出　　处：《地球化学》2003年第4期317-327,共11页Geochimica

基　　金：国家重点基础研究计划(2001CB409803);国家"305"项目(96-915-03-02);国家攀登计划预选项目(95-预-25)

摘　　要：西天山火山岩属玄武安山流纹岩建造,钙碱性(中钾、高钾)和橄榄玄粗岩系列。其40Ar/39Ar年龄范围为250～306Ma,以260～290Ma为高峰值。浅侵位岩浆岩属偏碱性、碱性岩石或高钾钙碱性系列岩石,40Ar/39Ar年龄范围为260～290Ma。综合Ar-Ar和Rb-Sr、U-Pb年龄资料,西天山地区火山-浅侵位岩浆活动高峰期发生在晚石炭世—早二叠世。40Ar/39Ar坪年龄资料还显示了晚二叠世、侏罗纪—早白垩世的热事件信息。对区内高钾钙碱性火山岩、橄榄玄粗岩和埃达克质岩石等富碱火成岩的年龄测定表明,本区构造格架的重大转折———由俯冲、碰撞造山的挤压,转向后碰撞的伸展、拉张———发生在石炭纪末—早二叠世(250～300Ma)期间。Volcanic rocks in western Tianshan belong to basalt andesite rhyolite series, or medium potassic calc alkaline, high potassic calc alkaline and shoshonitic series. The range of 40Ar/39Ar ages of the volcanic rocks is 250～ 306 Ma with peak values of 260～ 290 Ma. The hypabyssal igneous rocks belong to subalkaline alkaline or high potassic calc alkaline series. Their 40Ar/39Ar ages are from 260 Ma to 290 Ma. These 40Ar/39Ar ages have shown that the volcanic hypabyssal magmatic activities happened during late Carboniferous to early Permian, and mainly at the end of late Carboniferous to early Permian. According to the data of 40Ar/39Ar dating several thermal events may take place in late Permian, and Jurassic to early Cretaceous. The 40Ar/39Ar chronological data of high potassic calc alkaline series, shoshonitic series and adakite alkali rich igneous rocks have shown that in the orogeny process of western Tianshan the tectonic framework transformed from the compression of subduction and collision orogeny to the extension of post collision during the end of Caboniferous to early Permian (250～ 300 Ma).

关 键 词：西天山火山岩 玄武安山流纹岩 晚古生代 氩同位素年龄 浅侵位岩浆岩 斑岩 橄榄玄粗岩 埃达克岩 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]