内蒙古苏莫查干敖包萤石矿区流纹岩锆石SHRIMP定年及地质意义

内蒙古苏查（苏莫查干敖包）萤石矿区晚古生代火山沉积岩分布广泛，主要岩石类型有碳泥质板岩、结晶灰岩、凝灰岩、千枚岩、英安岩和流纹岩，其中碳泥质板岩和流纹岩为苏查特大型萤石矿床的顶和底板围岩。采用锆石SHRIMP UPb铅法分别对底板围岩中蚀变流纹岩和顶板围岩中未蚀变流纹岩样品进行了同位素年代测定，所获数据分别为276±10 Ma和271±8 Ma。蚀变和未蚀变流纹岩的形成时间均为海西晚期（早二叠世）。苏查萤石矿区早二叠世流纹岩是华北陆台与西伯利亚板块从碰撞挤压到松弛张裂转折期，酸性岩浆喷发活动的产物，其成岩物质来自壳、幔混合源。早二叠世流纹岩的出现不仅标志着苏查到西里庙地区海西期构造岩浆活动的终结，同时也为苏查特大型萤石矿床的成矿作用提供了动力、热力和物质来源。早二叠世流纹岩成岩时代的厘定不仅为阐明华北陆台北缘西段构造演化历史提供了科学依据，而且对于查明流纹岩的原岩性质和圈定新的萤石矿床找矿靶区也具有重要意义。

Zircon SHRIMP U-Pb Dating on Rhyolite Samples from the Xilimiao Group Occurring in the Su Cha (Sumoqagan Obo) Fluorite District, Inner Mongolia

The Su-Cha(Sumoqagan Obo)fluorite district,located on the northern margin of the North China continental massif,is the largest fluorite-only district in the world.Fluorite mineralization occurs mainly within in Late Paleozoic volcano-sedimentary sequences of the Xilimiao Group.Previous studies show that the geological setting for the Su-Cha fluorite district is a late Paleozoic rift basin along the convergence zone of the Northern China continental massif and Siberian platform.The whole Xilimiao Group can b...