赣西大港花岗岩型锂矿床锂赋存状态及成岩成矿年代学  

Occurrence of Lithium and Geochronology of Magmatism and Mineralization in Dagang Granite-Associated Lithium Deposit,West Jiangxi Province

作　　者：龚敏 吴俊华 季浩 徐敏林 况二龙 姜宝亮 李国猛 李艳军[4] Gong Min;Wu Junhua;Ji Hao;Xu Minlin;Kuang Erlong;Jiang Baoliang;Li Guomeng;Li Yanjun(Jiangxi Exploration Breakthrough Technology Center,Nanchang 330052,China;The First Geological Brigade,Jiangxi Bureau of Geology,Nanchang 330052,China;Jiangxi Bureau of Geology,Nanchang 330036,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]江西省找矿突破勘查技术中心,江西南昌330052 [2]江西省地质局第一地质大队,江西南昌330052 [3]江西省地质局,江西南昌330036 [4]中国地质大学资源学院,湖北武汉430074

出　　处：《地球科学》2023年第12期4370-4386,共17页Earth Science

基　　金：江西省重点研发计划"揭榜挂帅"项目(No.20223BBG71015)。

摘　　要：大港锂矿床是赣西地区近年来新探明的超大型花岗岩型锂矿之一,成矿与白云母花岗岩密切相关.研究开展了云母矿物学特征及电子探针分析确定锂赋存状态,并利用锆石和锡石LA-ICPMS U-Pb定年法对白云母花岗岩进行了系统的年代学研究,精确厘定成岩成矿时代.年代学结果显示I型热液锆石Tera-Wasserburg U-Pb下交点年龄为129±2 Ma,而颜色较暗的II型锆石下交点年龄为100±4 Ma.锡石核部和边部Tera-Wasserburg U-Pb下交点年龄分别为125±3 Ma和108±7 Ma,同期结果与锆石年龄在误差范围内一致.这些年龄数据显示大港锂矿呈多期次成矿特点.成矿作用均形成于早白垩世,与江南造山带中段燕山期大规模稀有金属成矿时限一致.大港锂矿床中云母主要为富锂白云母、铁锂云母和锂云母,且云母具有明显环带特征,边部较核部富Si、Li和F等元素.云母微观结构及矿物化学特征表明大港高演化花岗岩型锂矿床经历了早期岩浆分异和晚期热液交代两个阶段.晚期富氟富锂热液对白云母花岗岩进行了强烈的交代改造,使锂元素在云母边部高度富集,从而形成富锂矿物.九岭南缘高演化花岗岩型锂矿床的厘定指示了江南造山带中段具有良好的锂矿找矿前景.The Dagang lithium deposit is a giant granite-associated deposit in the West Jiangxi Province,central Jiangnan orogenic belt(JNOB).Lithium mineralization is closely associated with muscovite granites.However,the occurrence of lithium and geochronology of magmatism and mineralization are not well defined.In this study,it presents microtextural studies,electron probe microanalysis(EPMA)of micas,as well as laser ablation inductively coupled plasma(LA-ICPMS)zircon and cassiterite UPb dating results to further constrain the occurrence state,metallogenic mechanism,and geochronology.LA-ICPMS U-Pb dating of cassiterite core yielded a Tera-Wasserburg U-Pb lower intercept age of 125±3 Ma and cassiterite rim yielded a lower intercept age of 108±7 Ma.Type I zircon,which shows lower content of U,has an LA-ICPMS Tera-Wasserburg U-Pb lower intercept age of 129±2 Ma,and Type II zircon grains with higher U content yielded a lower intercept age of 100±4 Ma.Geochronological results reveal two episodic Li mineralization events during the Early Cretaceous in the Dagang deposit.In addition,the mineralization ages of the Dagang Li deposit are consistent with the large-scale magmatic and metallogenic events for rare metal deposits in the central JNOB.Zoned micas which are revealed by BSE images from the Dagang Li deposit are composed of Limuscovite,zinnwaldite,as well as lepidolite.The Li-bearing micas are the principal ore minerals in the muscovite granites.A gradual increase in Li,Si,and F in all micas from core to rim is exhibited by electron probe microanalysis(EPMA).The occurrence and geochemical features indicate that the Dagang Li deposit formed through an early-stage magma fractional crystallization and a late-stage hydrothermal process.The temporal relationship between Early Cretaceous S-type granitic magmatism and Li mineralization in the central JNOB can be used as a guideline for mineral exploration of granite rare metal deposits.

关 键 词：花岗岩型锂矿床 副矿物U-Pb定年 赋存状态 岩浆-热液演化 大港 地球化学 

分 类 号：P618[天文地球—矿床学]