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

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 ~0.25Mkm2. 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 291~287Ma, 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.