江苏溧水观山高硫型铜铅金矿床40Ar/39Ar 定年及其地质意义

位于江苏溧水盆地的观山铜铅金矿是典型的高硫型浅成低温热液矿床，但一直缺少精确的成矿年龄数据。对观山矿床近矿围岩绢云母化粗安斑岩中的2件绢云母样品进行40Ar/39Ar定年，得到的年龄分别为（120.8±1.0） Ma和（116.0 ± 1.3） Ma，显示观山铜铅金矿形成于中国东部中生代大规模成矿作用时期。距今125 Ma~115 Ma，整个中国东部地区处于伸展背景下, 发生了大规模的岩浆活动，并形成了包括溧水火山盆地在内的一系列的断陷盆地。溧水盆地在构造运动的强烈影响下，深部岩浆上涌, 形成浅部岩浆房。在热动力的驱动下，富含成矿物质的岩浆水不断与大气降水混合，在近地表形成与粗安斑岩次火山岩有关的浅成低温热液铜多金属矿床。

40Ar/39Ar Dating of the Guanshan High Sulphidation Type Cu-Pb-Au Deposit in Jiangsu Province and Its Geological Significance

Guanshan Cu-Pb-Au deposit in Lishui basin of Jiangsu Province is a high sulphidation type epithermal deposit hosted in Late Mesozoic subvolcanic rocks. 40Ar/39Ar dating was performed on two sericite samples collected from sericitized subvolcanic wallrocks of Guanshan deposit. The results yield plateau ages of（120.8±1.0）Ma and（116.0±1.3）Ma，respectively, suggesting that the major mineralization of Guanshan belongs to the large-scale Mesozoic metallogenic event occurred in eastern China. During 125 Ma to 115 Ma, most part of eastern China was affected by extensional tectonic stress, resulting in large-scale magmatism and formed a series of fault-depressed basins, including the Lishui volcanic basin. In this basin, upwelling of deep-seated magma provided magmatic heat, triggered circulation of meteoric water, which mixed with magmatic fluid, and finally deposited the ore minerals in brittle fractures in the trachyte-porphyry wallrocks.