江西石门寺钨多金属矿床花岗岩独居石U-Pb精确定年及地质意义

石门寺钨多金属矿床位于大湖塘矿田的北部,赣北九岭成矿带中段,是目前世界上最大的几个钨矿之一。本文对矿区出露的似斑状黑云母二长花岗岩、细粒黑云母二长花岗岩和花岗斑岩的独居石进行了LA-ICP-MS U-Pb年龄测定,其年龄分别为150.0±0.7 Ma、149±1 Ma和148.2±1.2 Ma。独居石测年数据显示,三种岩性的样品Tera-Wasserburg反向谐和图的下交点年龄与206Pb/238U加权平均年龄一致,反映了花岗岩的结晶年龄为燕山期,结合矿区辉钼矿的Re-Os成矿年龄(150.4±1.4 Ma),表明石门寺钨矿成矿作用与花岗岩的形成密切相关。大湖塘钨矿区的成岩成矿作用与钦杭成矿带的大规模钨锡多金属成矿作用在时间上一致(~(150) Ma),具有统一的地球动力学背景,形成于岩石圈拉张减薄的动力环境下。

In-situ Monazite U-Pb Geochronology of Granites in Shimensi Tungsten Polymetallic Deposit,Jiangxi Province and its Geological Significance

The Shimensi tungsten polymetallic deposit, located in the north part of the Dahutang ore field in the Jiuling metallogenic belt, North Jiangxi, is one of the world’s largest tungsten deposits. In-situ LA-ICP-MS monazite U-Pb dating was used to determine the ages of the ore-bearing granites in this study. Analyses of the monazite from the porphyric biotite monzogranite, fine-grained monzogranite and granite porphyry, yield concordant ages of 150.0±0.7 Ma, 149±1 Ma and 148.2±1.2 Ma, respectively. Furthermore, their lower intercept ages on the Tera-Wasserburg plots and the corresponding weighted average 206Pb/238U ages are consistent within error, reflecting the crystallization age of the granites. Combining the molybdenite Re-Os age of 150.4±1.4 Ma, the rock- and ore-forming processes in the Shimensi tungsten polymetallic deposit are under a geodynamic setting of lithospheric thinning and extension, which is consistent with the large scale tungsten-tin polymetallic mineralization (~150 Ma) in the Qinhang metallogenic belt, South China.