安徽铜山铜矿床硫化物Re-Os定年及其地质意义

Re-Os isotopic dating of sulfides from the Tongshan copper deposit,Anhui Province and its geological implications

安徽铜山矽卡岩型铜矿床是长江中下游成矿带的重要矿床之一,其2件辉钼矿样品和2件黄铁矿样品的Re-Os同位素年龄分别为150.70±1.14～151.22±1.11Ma和148.73±3.22～152.50±6.69Ma,4件样品的等时线年龄为150.98±0.78Ma(MSWD=0.68,误差2σ)。这一结果表明,铜山铜矿形成于晚侏罗世,而非早白垩世。考虑到前人获得的长江中下游成矿带的成矿年龄介于134Ma和144Ma之间,我们认为长江中下游成矿带的成矿作用主要发生在侏罗纪-白垩纪之交,与构造体制由挤压转向伸展的过程同步。

The Tongshan skarn-type copper deposit,Anhui Province,is one of the most important mineral deposits in the Middle-Lower Yangtze metallogenic belt.Two molybdenite separates and two pyrite separates from the ores yield Re-Os isotopic ages of 150.70±1.14~151.22±1.11Ma and 148.73±3.22~152.50±6.69Ma,respectively.These four analyses yield an isochron age of 150.98±0.78Ma （MSWD=0.68 at 2σ level）.The result indicates that the Tongshan copper deposit was formed in Late Jurassic,rather than Early Cretaceous.Considering that all the isotope ages previously obtained for mineralizations in the Middle-Lower Yangtze metallogenic belt are between 134Ma and 144Ma,we suggest that the Middle-Lower Yangtze metallogenic belt was formed in the transition from Late Jurassic to Early Cretaceous,coeval with the tectonic transition from compression to extension.