排山楼金矿床40Ar-39Ar年龄及其地质意义

采用Ar-Ar同位素测年法对辽宁排山楼金矿床矿化阶段形成的钾长石和似斑状花岗岩中的钾长石进行了测试,获得矿化阶段形成钾长石40Ar-39Ar坪年龄为(116.69±1.15)Ma,等时线年龄为(116.97±1.39)Ma,以及似斑状花岗岩中原生钾长石40Ar-39Ar坪年龄为(126.71±2.03)Ma,等时线年龄为(124.00±4.32)Ma的数据.前者代表了该矿床的形成年龄,即该矿床形成于早白垩世,后者表明金矿化不早于(126.71±2.03)Ma.这一成矿年龄与华北陆块北缘大部分金矿床的成矿年龄一致,表明华北陆块北缘绝大多数金矿床形成于中国东部中生代动力学体制发生转折的时期.

~(40)Ar-~(39)Ar Isotopic Dating for Paishanlou Gold Deposit and Its Geological Implication

The Paishanlou big gold deposit is situated in the margin of the North China Craton, and the gold deposit is in the Archeozoic meta-volcanic rock of Wulashan group. The ore body especially the host is strictly controlled by ductile shear zone and in the biotite-anorthose and gneissic/felsic mylonite. The ⁴⁰Ar-³⁹Ar isotopic geochronology of the potassium feldspar formed in the metallization phase in the gold deposit was studied. The result showed that the K-feldspar has an ⁴⁰Ar-³⁹Ar plateau age (116.69 ± 1.15) Ma and isochron age (116.97 ± 1.39) Ma, which reveal the age of the deposit, i.e., formed in early Cretaceous. And the K-feldspar in the prorphyro-like granite has an ⁴⁰Ar-³⁹Ar plateau age (126.71 ± 2.03) Ma and isochron age (124.00 ± 4.32) Ma, which reveal that the mineralization was beginning not earlier than (126.71 ± 2.03) Ma ago. The age of Paishanlou gold deposit is in close coincidence with other gold deposits situated in the margin of the North China Craton. The result indicated that most of the gold deposits in the same region formed in the period during which the geodynamic metamorphism occurred in East China during Mesozoic era.