粤西河台金矿锆石SHRIMP年龄及其地质意义

SHRIMP Zircon U-Pb Dating of the Hetai Gold Deposit in Western Guangdong, China and Geological Implications

河台金矿是一个受剪切带控制的金矿床，成矿作用分为韧性剪切变质成矿期的韧性剪切变质成矿作用阶段和热液蚀变成矿期的金硅化石英脉阶段、金硫化物阶段以及方铅矿闪锌矿碳酸盐脉阶段，金的成矿主要发生在热液蚀变成矿期的金石英脉阶段和金硫化物阶段。SHRIMP锆石U—Pb测年显示赋矿围岩混合岩中继承性锆石的核部和幔部年龄为343．9～1732Ma，代表形成混合岩原岩的源区岩石的年龄；继承性锆石边部和混合岩化变质作用中新生锆石的年龄平均值为239．6±3．9Ma，属印支期，为混合岩化变质作用的年龄，这一年龄与印支期印支板块与扬子板块、扬子板块与华北板块的碰撞时代相一致，证实在中国华南存在印支期的混合岩化变质作用。韧性剪切变质成矿作用的年龄小于混合岩化变质作用的年龄（239．6±3．9Ma）；富硫化物含金石英脉中热液锆石普通铅含量高，为0．65％～2．27％，Th／U值变化围很小，为0．306～0．557，其年龄为152．5±3．1Ma，属燕山期，代表河台金矿主成矿期年龄。

The Hetai gold deposit is strictly controlled by ductile shear zone. The metallogenesis process can be divided into two epochs and four stages, viz. , ductile shear metamorphic metallogenesis epoch of ductile shear metamorphic metallogenesis stage and hydrothermal alteration metallogenesis epoch of gold quartz vein stage, gold sulfides stage and galena-sphalerite-carbonate vein stage. Gold mineralization occurred mainly in the gold quartz vein stage and the gold sulfide stage. SHRIMP zircon U-Pb dating show that the core and mantle ages of zircons from wallrock migmatite that hosted the deposit are 343.9-1732Ma,representing the source rock age for protolith of migmatite. The average age of the marginal zone ages of inherited zircons and the newly grown zircons in migmatite is 239.6±3.9Ma, belonging to the Indosinian period,and representing the age of migmatic metamorphism, which also corresponds with the times of the North--South China and Indochina South China collision, and approves the occurrence of migmatic metamorphism in South China in the Indosinian epoch. The age of ductile share metamorphic mineralization is younger than the migmatite metamorphism age of 239. 6±3. 9Ma. The zircons from sulfide-rich gold-bearing quartz vein have high common Pb concentration, 0. 65-2.27%0, the range of Th/U ration is narrow, 0. 306-0. 557, and the age is 152.5±3.1Ma, belonging to the Yanshanian epoch, and representing the age of the main mineralization epoch of the Hetai gold deposit.