煌斑岩在玲珑金矿田形成过程中的地质意义

GEOLOGICAL SIGNIFICANCE OF LAMPROPHYRE DURING GOLD MINERALIZATION IN THE LINGLONG ORE FIELD

玲珑金矿田发育的金矿脉以黄铁石英脉为主。发育的含金石英脉在时空及成因方面与煌斑岩脉有密切联系。在空间上,煌斑岩脉与黄铁石英矿脉呈小角度相交,且大都错断矿脉。在时间上,同位素测年显示,煌斑岩脉的形成时间范围较大,一般为80～132Ma,而石英脉的形成主要集中在100～110Ma。通过煌斑岩中金含量测定及高温高压实验,煌斑岩并非是金元素的来源,金元素与煌斑岩在高温高压条件下不相溶,在成因方面,形成矿脉的大部分金元素与煌斑岩脉应同属于地幔物质;地幔岩浆含大量的地幔流体,根据金的化学性质,金易和地幔流体中的Cl-、OH-结合形成络合物,在地幔岩浆上侵过程中随地幔流体上升到地壳上部,并在适当的位置聚集形成含金石英矿脉,而煌斑岩浆从上侵的基性岩浆中分离出来,充填于构造裂隙中,形成煌斑岩脉。

The gold veins in the Linglong ore field are mainly pyrite quartz veins. Space-time and origin of the gold veins in the ore field were closely related with some lamprophyre dykes. The angle degrees between lamprophyre and pyrite-quartz veins are smaller in space, and lots of lamprophyre dykes cut pyrite-quartz veins. Formation time of gold-bearing quartz veins among 100-110Ma was shorter than that of lamprophyre dykes among 80-132Ma. Gold did not come from lamprophyre because gold and lamprophyre can't compatible in the condition of high temperature and pressure, and there is very little gold in lamprophyre through determination and experiment. Most gold in ore bodies and lamprophyres all belong to mantle substance that contents a great deal of fluids. The fluids containing gold departed from mantle magma during the magma rising up, and gold deposited in appropriate position in the upper crust. In the mean time, the lamprophyre magma also departed from mantle magma and filled up the fracture and became lamprophyre dykes.