贵州北部马鬃岭铝土矿床中富锂铝质粘土岩碎屑锆石U-Pb年龄、Lu-Hf同位素特征及其对锂源的制约

U-Pb Ages and Lu-Hf Isotopic Characteristics of Detrital Zircons for Li-Rich Aluminous Argillite and Their Constraints to the Lithium Source in the Mazongling Bauxite Deposit,Northern Guizhou Province

为研究贵州北部马鬃岭铝土矿床中富锂铝质粘土岩的物源体系及其锂的来源,对出露于大竹园组顶部的该类岩石进行了锆石U-Pb定年、Lu-Hf同位素及锆石微量元素分析。分析结果表明富锂铝质粘土岩中碎屑锆石普遍发育岩浆振荡环带,为造山作用/弧作用相关的岩浆岩类锆石。碎屑锆石U-Pb年龄从早泥盆世到太古宙(411~3001 Ma)均有分布,具627~879 Ma和925~1018 Ma两个主峰及539~602 Ma一个次峰。ε_(Hf)(t)值为-27.61~7.03之间,二阶段模式年龄(t_(DM2))分布在1242~3387 Ma之间。结合碎屑锆石U-Pb-Hf同位素、微量元素特征及区域地质对比,认为富锂铝质粘土岩中碎屑锆石最主要的初始物源区为南岭-云开地体、江南造山带西段新元古代岩浆岩,其锂可能来源于江南造山带西段桂北-黔东地区860~750 Ma的基性岩。

In order to determine the provenance system of Li-rich aluminous argillite and its source of lithium in the Mazongling bauxite deposit,northern Guizhou,LA-ICP-MS U-Pb micro-dating,Lu-Hf isotope and trace elements analysis of detrital zircons of Li-rich aluminous argillite in the top of the Dazuyuan Formation were conducted.Detrital zircons generally show magmatic oscillating zonation,and are magmatic zircons related to orogenic/arc interactions.U-Pb ages of detrital zircons distributions appear to be from the Early Devonian to Archean(411~3001 Ma),with two main clusters at 627~879 Ma,925~1018 Ma and one minor cluster at 539~602 Ma.ε_(Hf)(t)values of detrital zircons vary from-27.61 to 7.03 with two-stage Hf model ages(t_(DM2))of 1242~3387 Ma.Based on the above results,it is considered that the primary provenance of detrital zircons is the Neoproterozoic magmatic rocks in the Nanling-Yunkai terrane and western segment of the Jiangnan Orogen.The lithium in the Li-rich aluminous argillite may have come from the basic rock of 860~750 Ma in the northern Guangxi-eastern Guizhou region of the western part of Jiangnan Orogen.