陕西太白双王金矿床地质特征及稳定同位素地球化学研究

Geology and stable isotope geochemistry of the Shuangwang gold deposit in Taibai County,Shaanxi Province

陕西双王金矿床位于西秦岭凤太矿集区东部,为一大型含金钠长角砾岩型金矿床。矿床赋存于上泥盆统星红铺组,为一套由钙质粉砂岩、粉砂质绢云板岩和灰岩组成的类复理石沉积建造。金矿体明显受角砾岩体控制,呈断续带状分布,矿石硫化物主要为黄铁矿,主要围岩蚀变类型为钠长石化。矿床稳定同位素地球化学特征研究表明:早阶段和主阶段成矿流体以岩浆热液和建造水的混合热液为主,晚阶段由岩浆热液向大气降水热液演化;碳主要来源于深部,并混有碳酸盐岩地层溶解形成的碳;硫具有地壳硫和岩浆硫混合来源的特征;铅的来源以上地壳为主,并混有少量地幔铅。结合区域地质构造背景,认为双王金矿床成矿作用与始于印支晚期的陆内碰撞造山作用有关,成矿过程经历了隐爆前的热液交代成矿期和隐爆后的热液充填成矿期,其中隐爆后的热液充填交代阶段是金矿床的主要成矿阶段,双王金矿床成因类型为隐爆角砾岩型金矿床。

The Shuangwang gold deposit,located in the east of the Fengtai ore concentration area of West Qinling,is a large gold deposit of auriferous albite breccias type.The ore deposit occurs in the weakly metamorphosed upper Devonian Xinghongpu Group,dominated by calcareous siltstone,sericite silty slate and carbonate that comprise flyschoid formation.Gold mineralization is strictly controlled by auriferous breccia bodies.Pyrite is the most important ore sulfide,and the main wall-rock alteration is albitization.Systematic stable isotope analyses show that the ore-forming fluids of the early and the main stages came from mixed fluids and those of the late stage mainly came form magmatic hydrothermal fluids with the addition of a little meteoric water.Carbon was derived mainly from the great depth and partly from the dissolution of carbonate strata.Sulfur is the mixed sulfur of the crust and the magma.Lead mainly came from the upper crust with the mixture of a little mantle lead.Based on the regional geological-structural background,it is concluded that the mineralization of the Shuangwang gold deposit was related to the Late Triassic collision between the North China Plate and the Yangtze Plate.The early stage mineralization was mainly caused by hydrothermal metasomatism,and the main gold mineralization occurred at the hydrothermal filling stage after the blasting action.The Shuangwang gold deposit is genetically a cryptoexplosive breccia type gold deposit.