塔里木二叠纪基性-中性-酸性岩浆岩的年代学及其地质意义  

Geochronology of the Permian basic-intermediate-acidic magma suite from Tarim,Northwest China and its geological implications

作　　者：陈咪咪[1] 田伟[1] 张自力[2] 潘文庆[3] 宋宇[1] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]北京大学遥感与地理信息系统研究所,北京100871 [3]中石油塔里木油田公司勘探开发研究院,库尔勒841000

出　　处：《岩石学报》2010年第2期559-572,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划(973)项目(2007CB411307);国家自然科学基金项目(40502009;40821002)联合资助

摘　　要：塔里木西部柯坪地区出露的早二叠纪玄武岩与盆地内其他地区广泛分布的玄武岩共同构成一个面积约0.25Mkm^2的溢流玄武岩省。巴楚地区出露的早二叠纪辉绿岩、正长岩、石英正长岩与石英正长斑岩等多种岩浆岩构成了连续的基性-中性-酸性岩浆序列。野外露头观察表明,巴楚麻扎尔塔格地区的基性-中性-酸性岩浆岩为近同时侵位。柯坪塔格开派兹雷克组顶部层位玄武岩的锆石SHRIMP U-Pb年龄为279.0±4.5Ma,该年龄值可限定该区二叠纪溢流玄武岩喷发的最晚时限。巴楚麻扎尔塔格石英正长斑岩脉的锆石SHRIMP U-Pb年龄为273.0±3.7Ma,与前人测定的巴楚辉绿岩脉和正长岩的锆石年龄在误差范围内一致,表明巴楚地区的基性-中性-酸性岩浆岩为近同时侵位,时间在275Ma左右。综合已发表的塔里木二叠纪岩浆岩高精度年代数据,本文提出:整个塔里木大火成岩省岩浆作用的持续时间约为20Myrs;291～287Ma喷发的巨量溢流玄武岩可能构成塔里木大火成岩省的主体,是地幔柱头部熔融的直接产物;283～272Ma侵位的巴楚、一间房和塔北地区的其它类型岩浆岩体积较小,为塔里木大火成岩省晚期岩浆作用的产物。The Early Permian basalt from Keping,western Tarim,China,together with Permian basalt from elsewhere Tarim basin, constitute a Large Igneous Province(LIP) that coveres an residue area of～0.25Mkm.Zircon SHRIMP U-Pb age of basalt from top of Kapaizileike Formation is 279.0±4.5Ma,which constrains the youngest time of the Tarim Permian flood basalt eruption.An Early Permian basic-intermediate-acidic magma suite,including diabase,syenite,quartz syenite and quartz syenitic porphyry dyke,intruded into Mazhatarger mountain of Bachu area,western Tarim.The nearly simultaneous emplacement of Mazhatarger basic-intermediate-acidic magma suite is proved by the outcrop evidence.Zircon SHRIMP U-Pb age of the quartz syenitic porphyry dyke from Mazhatarger is 273.0±3.7Ma,which is same as published zircon ages of Bachu diabase and Mazhatarger syenite within error.The above ages show the similarity of emplacement times of basic,intermediate and acidic magmas from the Bachu area,which is about in 275Ma.Based on the published high-accuracy ages,it is proposed in this paper that the Tarim Large Igneous Province has a magmatism lifespan of～20Myrs.The flood basalt,which is thought to erupt mainly in 291～287 Ma,constitutes the major pulse of the Tarim LIP and should be generated by partial melting of a plume head.The voluminal-minor basic-intermediate-acidic intrusions from Bachu,Yijiangfang and northern Tarim subsurface area at 282～273Ma,are supposed to belong to post major eruption magmatism of the Tarim LIP.

关 键 词：塔里木 溢流玄武岩 大火成岩省 二叠纪 锆石SHRIMP U-PB年龄 

分 类 号：P588.12[天文地球—岩石学]