江西茜坑锂矿床地质地球化学特征与锂云母^(40)Ar/^(39)Ar年代学研究

Geological and geochemical characteristics of the Xikeng lithium deposit and the ^(40)Ar/^(39)Ar chronology of lepidolite of the deposit in Jiangxi Province, China

茜坑锂矿床是近年来新探明的大型锂矿床。锂矿主要产出于白(锂)云母花岗岩中,云母为锂矿最主要的赋存矿物。对茜坑花岗岩进行了矿床地质、地球化学和^(40)Ar/^(39)Ar年代学研究。研究表明,白(锂)云母花岗岩具有富硅、富碱、强过铝质、贫镁铁、富成矿元素、高挥发分、高分异的地球化学特征,稀土总量低(ΣREE平均值为3.41×10^(-6)),Eu具强烈负异常,稀土元素球粒陨石标准化配分曲线具有明显的M型四分组效应,属(高)分异S型花岗岩。锂云母^(40)Ar/^(39)Ar坪年龄为(139.09±0.56) Ma,等时线年龄为(138.45±1.11) Ma,成岩成矿时代为早白垩世,处于扬子板块与华夏板块碰撞后陆内造山挤压至伸展过渡初期。

The Xikeng lithium deposit is a recently discovered newly explored large-scale lithium deposit.Its orebodies mainly occurred in muscovite (lepidolite) granite.Mica is the major Li-hosted mineral.The deposit geology,geochemistry,and;^(40)Ar/^(39)Ar chronology of the Xikeng deposit have been studied in this paper.The geochemical study shows that the muscovite (lepidolite) granite samples are characterized with enriched silicon and alkali,strongly peraluminous,depleted Mg and Fe,enriched ore-forming elements,high contents of volatiles,and high degree of magmatic fractionation;low contents of total rare earth elements (average∑REE value of 3.41×10^(-6)),strongly negative Eu anomalies,and the obvious M-type tetrad effect on the chondrite-normalized REE distribution patterns.Thus,the muscovite (lepidolite) granite belongs to the highly differentiated S-type granite.The obtained ^(40)Ar/^(39)Ar plateau age of lepidolite is 139.09±0.56 Ma,and isochron age of lepidolite is 138.45±1.11 Ma,indicating that the lithium mineralization occurred in the early stage of the transition from intracontinental orogenic compressional to extensional environments after the collision of Yangtze and Cathaysia plates in the early Cretaceous.