赣南矽卡岩型钨矿成岩成矿年代学及地质意义——以焦里和宝山矿床为例

矽卡岩型钨矿是赣南地区的一种重要钨矿床类型。本文以焦里和宝山两个典型的矽卡岩型钨多金属矿床为例,开展了系统的成岩成矿年代学和岩石地球化学研究,结合区域钨锡矿床最新年代学研究成果,探讨了赣南地区钨矿的成岩成矿时代及形成构造环境。结果表明,焦里矽卡岩型钨多金属矿区斑状花岗闪长岩SHRIMP锆石U-Pb年龄为164.4±1.1Ma,辉钼矿Re-Os等时线年龄为170.6±4.6Ma;宝山矽卡岩型钨矿区花岗岩SHRIMP锆石U-Pb年龄为156.6±3.9Ma,辉钼矿Re-Os模式年龄加权平均值为161.0±1.9Ma,厘定了它们的成岩成矿年龄为中-晚侏罗世,同一矿区的成岩和成矿年龄在误差范围内基本一致。结合赣南崇(义)-(大)余-(上)犹钨锡矿集区已有的年代学资料,指出本区的成岩成矿年龄介于170～150Ma,集中在160～150Ma,认为赣南钨矿形成于华南中生代岩石圈伸展-减薄时期的侏罗纪板内拉张的地球动力学背景,系同一成岩成矿系统的产物。

SHRIMP Zircon U-Pb and Molybdenite Re-Os Dating of the Skarn-type Tungsten Deposits in Southern Jiangxi Province, China, and Geological Implications: Examplified by the Jiaoli and Baoshan Tungsten Polymetallic Deposits

Skarn-type tungsten deposit is a very important type of tungsten mineral resources in southern Jiangxi province.Based on detailed field investigation and analysis on major elements,trace elements,rare earth elements and radiometric dating,the ages of tungsten mineralization and petrogenesis of ore-bearing granitoids,and tectonic environment of the skarn-type tungsten deposits in southern Jiangxi province were studied.SHRIMP zircon U-Pb age for the medium to fine-gained porphyritic granodiorite from the Jiaoli ore district is 164.4±1.1 Ma.Molybdenite Re-Os isochron age for the related Jiaoli skarn tungsten deposit is 170.6±4.6 Ma.The SHRIMP zircon U-Pb age of the Baoshan medium to fine-grained granite is 156.6±3.9 Ma,whereas the molybdenite Re-Os mean model age for the related Baoshan skarn-type tungsten deposit is 161.0±1.9 Ma.Thus,W-Sn mineralization and granite crystallization taking place in Middle to Late Jurassic were contemporaneous.These new ages,combined with those available in the literature,indicate that the ages of the granites and related W-Sn ores are Middle to Late Jurassic with a peak at 150 to 160 Ma.It can be concluded that tungsten mineralization occurred under Jurassic intraplate extensional environment which was a phase of lithospheric thinning in southern China.