新疆哈图金矿蚀变岩型矿体地质和地球化学研究

Studies on geology and geochemistry of alteration-type ore in Hatu gold deposit (western Junggar),Xinjiang,NW China

哈图金矿主要由石英脉型和蚀变岩型矿体组成。蚀变岩型矿体的矿化蚀变主要包括钠长石化、黄铁矿化、毒砂化、碳酸盐化和绢云母化,其中黄铁矿化、毒砂化和碳酸盐化与成矿作用密切相关。矿体中主要金属矿物为黄铁矿、毒砂、黄铜矿、闪锌矿、磁黄铁矿和自然金。自然金主要存在于毒砂颗粒间隙内或被黄铁矿包裹。蚀变岩型矿体成矿作用可划分为5个阶段:石英-钠长石阶段(Ⅰ)、黄铁矿-钠长石阶段(Ⅱ)、毒砂-碳酸盐阶段(Ⅲ)、黄铜矿-碳酸盐阶段(Ⅳ)和石英-方解石阶段(Ⅴ),其中Ⅲ—Ⅳ阶段是主要的成矿期。黄铜矿-碳酸盐阶段(Ⅳ)沉淀了大量黄铜矿和少量辉铜矿。不同程度蚀变的玄武岩围岩具有相似的平坦型球粒陨石标准化稀土元素配分模式,并富集Cs、Ba、Rb、Sr和Pb等大离子亲石元素。石英-钠长石脉的轻、重稀土元素发生了弱分馏,呈弱右倾式配分模式,显示弱的Eu正异常。石英-方解石脉的轻、重稀土元素分馏和Eu正异常较石英-钠长石脉明显,说明成矿作用过程中,成矿流体向轻稀土元素富集和Eu正异常增强的方向演化。

Hatu gold deposit, locating in West Junggar of Xinjiang, is composed ot quartz vein-type orebody and alteration-type orebody. In this paper we study the alteration-type orebody which mainly locates in the deep part of Hatu mine. Albitization, pyritization, arsenopyritization, carbonation, sericitization and chloritization are widespread in the alteration-type orebody. Gold mineralization is closely related to pyritization, arsenopyritization and carbonation. Pyrite, arsenopyrite, chalcopyrite, sphalerite, pyrrhotite and native gold are major metallic minerals. Native gold generally occurs in the boundary of arsenopyrite grains or as inclusions in pyrites. The ore-forming process of alteration-type orebody can be divided into five stages： quartz-albite stage （ Ⅰ ）, pyrite-albite stage （ Ⅱ ）, arsenopyrite-carbonate stage （ Ⅲ ）, chalcopyrite- carbonate stage （ Ⅳ ） and quartz-calcite stage （ Ⅴ ）. Stage Ⅲ and Ⅳ are main periods for gold deposition. Chalcopyrite-carbonate stage also corresponds with gold deposition. Basalts are enriched in Ba, Rb, Pb and Sr. The chondrite-normalized REE patterns of variously altered basalts are similar. The chondrite-normalized REE pattern of quartz-albite veins in alteration-type orebody are right-inclined and characterized by slightly positive Eu anomalies, with slight fractionation between LREE and HREE. The chondrite-normalized REE pattern of quartz-calcite vein is also right-inclined, with evidently positive Eu anomalies and evident fractionation between LREE and HREE conclud that the ore-forming fluid was gradually enriched in LREE with evidently positive Eu anomaly.