甘肃阳山特大型金矿床地质特征及成因

Geological features and origin of Yangshan supper large gold deposit, Gansu

阳山金矿为近年发现的一特大微细浸染型金矿床 ,已发现 4个矿段 ,均赋存于泥盆系地层中。矿体在平面上呈舒缓波状 ,剖面上为脉状、似层状。矿石中金属矿物主要为黄铁矿和毒砂 ,金主要以微细粒 (2～ 3μm)包裹于毒砂、黄铁矿等矿物之中。矿石中As、Sb及C有机 含量较高 ,并且Au与Ag、As、Hg、Sb等低温热液元素相关性明显。对矿床地质地球化学特征的研究表明 ,赋矿围岩为一套Au含量较高的C、Si、泥质沉积 ,在沉积成岩及印支期区域浅变质过程中Au被初步富集 ,其后又叠加了燕山早期岩浆、热液活动 ,使Au进一步富集 。

Yangshan gold deposit is a supper large gold deposit found in recent years.Four discovered ore area of the deposit all occur in Devonian epimetamorphised,phyllite or limestone. Ore bodies being little undulatory forms in plane and veinlike or bedded forms.Pyrite and arsenopyrite are the main metallic minerals which usually contain micrograined native gold(2～3 μm).As,Sb and C contents in the ore are high,and Au show positive correlation with epithermal ore elements such as Ag,As,Hg,Sb.Studies on geology and geochemistry of the deposit show that the host rock is a suite of carbonaceous,siliceous and argillaceous sediments with higher gold content. Gold was primarily enriched during the sedimentary and the later regional metamorphic process.In the early Jurassic period,magmatic and relevant ore fluid activities superposed in the rocks, and gold was enriched further. Therefore,Yangshan gold deposit is a superposed fine disseminated gold deposit.