鄂西恩施地区中—上二叠统界线黏土岩成因及其Nb-REE含矿性研究  

Genesis and Nb-REE Mineralization of Clay Rock at Guadalupian-LopingianBoundary in Enshi Area,Western Hubei Province

作　　者：张友军 雷福斌 李明龙 黄强[1] Zhang Youjun;Lei Fubin;Li Minglong;Huang Qiang(Second Geological Brigade of Hubei Geological Bureau,Enshi,Hubei 445000;Badong County Bureau of Natural Resources and Planing,Badong,Hubei 444399;Department of Resources and Environment,Henan Polytechnic University,Jiaozuo,Henan 454000)

机构地区：[1]湖北省地质局第二地质大队,湖北恩施445000 [2]巴东县自然资源和规划局,湖北巴东444399 [3]河南理工大学资源环境学院,河南焦作454000

出　　处：《资源环境与工程》2022年第5期529-538,共10页Resources Environment & Engineering

基　　金：湖北省地质局科技项目——恩施地区中二叠统—下三叠统火山沉积岩系及其资源与环境意义研究(KJ2022-16)。

摘　　要：扬子北缘中—上二叠统界线处的王坡层黏土岩与峨眉山大火成岩省密切相关,但其成因仍存在争议。近期云贵川上二叠统底部黏土岩中均发现了与峨眉山玄武岩风化有关的Nb、REE等稀有金属矿床,而扬子北缘王坡层黏土岩的含矿性研究还较薄弱。以鄂西恩施地区王坡层黏土岩为研究对象,通过详细的岩石学和地球化学研究,探讨其成因,并对其稀有金属找矿潜力进行初步评价。结果表明,研究区王坡层黏土岩具有低Al_(2)O_(3)/TiO_(2)比值(4.04~8.21)、较高的烧失量(LOI=7.24%~11.71%)、极高的化学蚀变指数(CIA=87.99~97.31)和较低的成分变异指数(ICV=0.36~0.87),而且镜下可见大量基性火山物质和气孔构造,长石亦无磨圆,推测其主要为强烈风化条件下峨眉山玄武岩近源堆积产物。黏土岩中Nb含量介于108~326μg/g,平均值187.67μg/g;Ta含量介于6.15~17.7μg/g,平均值10.74μg/g;REE介于298.6~1123.5μg/g,平均值623.79μg/g,显示其具有较好的找矿前景;Zr、Nb、Ta等元素异常富集,个别样品Eu和Ce显示正异常,表明黏土岩可能存在碱性火山灰的混入,Nb、REE等稀有元素在母岩风化沉积和成岩过程中经强烈蚀变而富集。本研究对完善峨眉山大火成岩省成矿系统具有一定意义。The Wangpo Layer clay rock at Guadalupian-Lopingian Boundary(GLB)in northern margin of Yangtze plate is closely correlated to Emeishan large igneous province(ELIP).However,the genesis is still debatable.It was reported recently about the rare metal deposits of Nb-REE related to the weathering of Emeishan basalts,which generated the clay rock at the bottom of upper Permian in Yunan,Guizhou and Sichuan area.It is still feeble about the research on the mineralization of Wangpo Layer clay rock in northern Yangtze plate.Based on Wangpo Layer clay rock in Enshi area,this study makes a detailed research on the mineralization of Nb-REE and genesis of Wangpo Layer clay rock according to the petrological and geochemical research.The results suggest low Al_(2)O_(3)/TiO_(2) ratios(4.04-8.21)and ICV(0.36-0.87),high LOI(7.24%-11.71%)and CIA(87.99-97.31)associated with amounts of basic volcanic ash,vesicles and unrounded feldspars under the microscope.All these characteristics indicate that the clay rock might be generated from Emeishan basalts under the intense weathering condition.The content of Nb is between 108 to 326μg/g with an average of 187.67μg/g.The content of Ta is between 6.15 to 17.7μg/g with an average of 10.74μg/g.The content of REE is between 298.6 to 1123.5μg/g with an average of 623.79μg/g.These results give a prospect on the mineral exploring of Nb,Ta,and REE.Both the enrichment of Zr,Nb,and Ta,and positive anomaly in Eu and Ce in several samples imply that alkaline volcanic ash was also interfused during the sedimentation.Nb and REE are thus enriched during the weathering,sedimentation and diagenesis of the clay rock.This study is remarkable significance for completing the metallogenesis system in Emeishan large igneous province.

关 键 词：中—上二叠统界线 黏土岩 NB REE 峨眉山大火成岩省 恩施 

分 类 号：P588.22[天文地球—岩石学] P618.7[天文地球—地质学]