论砾岩层控型半宽金矿的地质特征和成因

ON THE GEOLOGIC CHARACTERISTICS AND GENESIS OF THE CONGLOMERATE STRATABOUND TYPE BANKUAN GOLD DEPOSIT

半宽金矿产于崤山地体铁铜沟组与下代岩层的不整合面或铁铜沟组底砾岩中，赋矿层金丰度明显高于其它岩石，属典型的层控矿床，称之砾岩层控型。矿物包裹体、同位素、微量元素等研究表明，矿床形成经历了Ⅰ期高温变质热液蚀变矿化、Ⅱ期中温变质－雨水混合热液蚀变矿化、Ⅲ期低温雨水热液蚀变矿化。Ⅲ期对矿床形成的贡献较小。成矿物质来源复杂，以深源为主。矿床形成于中生代沿马超营断裂向北的陆内俯冲作用，结晶基底与上覆地层的不整合面及上覆地层的底部是寻找半宽式金矿的有利位置。

The Bankuan gold deposit is located at the unconformity between the Tietonggou formation and the underlying rocks in the Xiaoshan terrane or within the hasal conglomerate of theTietonggou formation. Gold abundance of the host rock bed is clearly higher than that in,'ether .rocks. The deposit is a typical stratabound one, and can be called as conglomeratestratabound type. A study on fluid inclusions in minerals,isotopes and trace elements showsthat the ore-forming process consists of three epochs. Epoch I is high-temperature metamorphic hydrothermal alteration-mineralization, epoch E, moderate-temperature mixed hydrothermal alteration-mineralization of metamorphic and meteoric solutions,epoch m, lowtemperature meteoric hydrothermal alteration-mineralization. Epoch N contributed negligiblyto the formation of the gold deposit. The source of ore-forming materials,dominated by thosefrom deep source,is very complex. The deposit was formed by the Mesozoic northward intracontinental subduction along the Machaoying fault. The most favourable positions ofprospecting for the Bankuan-type gold deposit are the unconformities between the crystalline'basement and the overlying strata and the bottom of the overlying strata.