山东中生代胶莱盆地北缘金矿床硫铅同位素地球化学

Sulfur and Lead Isotopic Geochemistry of Gold Deposits at the Northern Margin of Jiaolai Basin, East Shandong

位于山东胶莱盆地北缘的蓬家夼金矿、发云夼、大庄子等金矿 ,是一类受盆地边缘元古宙荆山群变质岩中的低角度层间滑动断层控制的蚀变构造碎裂 角砾岩型 (蓬家夼式 )金矿。硫同位素组成表明蓬家夼式金矿比胶东其它典型金矿的δ3 4 S偏高 ,且高于老地层和中生代花岗岩的 ,反映大气降水循环淋滤作用使硫同位素发生了较大程度的分馏。蓬家夼、大庄子金矿床矿石铅为异常铅 ,铅同位素组成与胶东群、玲珑、焦家和邓格庄等中生代花岗岩有关的金矿相比 ,其组成范围变化大 ,反映成矿物质的多源性。这与该类金矿所处的构造边缘 (转换 )环境相耦合。

In recent years, a new type of gold deposit, interlayer sliding breccia-type gold deposit, such as Pengjiakuang, Fayunkuang and Dazhuangzi gold deposits, had been discovered at the Northern margin of Jiaolai basin. Pengjiakuang-type gold deposit was controlled by low-angle slip fault zone —structural breccia rock zone. The fault provided structure and physical-chemical conditions for ore- forming processes. The isotope geochemistry research indicates that the sulfur isotope composition of Pengjiakuang-type gold deposit is higher than other typical gold deposit of Jiaodong area and just partially higher than that of meteorite sulfur. The δ 34S of ore sulfur is generally higher than that of old stratum and granite in Mesozoic Era, reflecting atmosphere water circulation results in strong fractionation of sulfur isotope. The scopes of lead isotope of Pengjiakuang-type gold deposit is wide, suggesting ore lead is unusual lead and ore-forming material comes from multiple source.