五台地区早前寒武纪金矿床类型及其地质特征

The Types and Their Geological Characteristics of Early-Precambrian Gold Deposits in Wutai Area,China

综合对比不同矿床产出的基本地质地球化学特征 ,五台地区典型早前寒武纪金矿床可划分出三种不同的类型 ,即小板峪式铁建造型金矿床、东腰庄型金矿床和康家沟型金矿床。小板峪式铁建造型金矿床赋存于条带状铁建造中 ,属后生叠加成因 ,矿石矿物组成除继承原铁建造矿物磁铁矿、赤铁矿外 ,主要为黄铁矿、少量黄铜矿和微量金、银 ,矿体随铁建造一起遭受了两期褶皱变形作用的改造 ,成矿时代早于 2 .3Ga。东腰庄型金矿床受控于韧 -脆性剪切带构造 ,具有复杂的矿物组成如黄铁矿、毒砂、黄铜矿、辉钼矿、电气石等 ,矿化具多阶段性 ,黄铁矿化、碳酸盐化、硅化围岩蚀变发育 ,成矿时代为 2 4 5 1Ma。康家沟型金矿床赋矿围岩主要为侵入成因碳酸岩 ,矿化产物为含黄铁矿、黄铜矿的碳酸盐石英脉或石英脉 ,成矿时代晚于 (2 140± 3)Ma。本区早前寒武纪多类型金矿床的形成 ,表明了五台地区早前寒武纪金矿成矿作用的复杂性和矿床成因的多样性 ,也为认识我国早前寒武纪金矿成矿作用特点创造了极为有利的条件。

There are different kinds of Early Precambrian gold deposits within the Archean greenstone belt in Wutai area. The main gold deposits can be divided into three types: Xiaobanyu type BIF hosted gold deposit,Dongyaozhuang type gold deposit and Kangjiagou type gold deposit. Xiaobanyu type BIF hosted gold deposits were hosted in the banded iron formation(BIF) that was formed in Archean. The main metal minerals of ore were pyrite, chalcopyrite with minor gold and silver, except magnetite and hematite which derived from the BIF. All the orebodies of BIF hosted gold deposits were reworked by two stages of folding deformation. The mineralization era was ca. 2.3 Ga. Dongyaozhuang type gold deposit was strongly restricted within the ductile brittle shear zone. This kind of gold deposit contains complex mineral composition such as pyrite, chalcopyrite, arsenopyrite, molybdenite, tourmaline and so on. Re Os isotopic age of molybdenite coming from the ore was (2 451±29)Ma, representing the ore forming era. Kangjiagou type gold depositwas characterized by the formation of quartz vein with pyrite, chalcopyrite. The origin of this kind of gold deposit was closely related to the formation of carbonatite intruded in (2 140 ±3)Ma( Sm Nd isochron curve dating). The variation of type of gold deposits in Wutai area shows complexities of ore forming process in Early Precambrian period.