西秦岭早子沟金矿床成因研究进展与展望

甘肃早子沟金矿床是西秦岭地区的一处超大型金矿床,围岩主要为三叠系古浪堤组浅变质粉砂质、泥质板岩,金矿体主要分布于闪长玢岩内部及其附近的断裂破碎带中,矿石以细脉浸染状为主,矿石矿物为黄铁矿、毒砂、辉锑矿,少量闪锌矿、方铅矿、黄铜矿及辉银矿等,脉石矿物为石英、白云石、方解石及绢云母等。结合近年来最新野外工作认识,基于已有成岩及成矿地质年代学、元素及同位素地球化学数据,文章进一步梳理了早子沟金矿床近5年科研认识,从主要控矿因素(构造控矿时空级序特征、成岩及成矿年代学格架)及主导成矿机制(元素及稳定同位素地球化学特征制约)两个重要方面对矿床地质特征、成岩和成矿时代、岩石成因与成矿的关系、围岩蚀变、成矿流体及成矿物质来源等多方面进行综合讨论,系统总结早子沟金矿床的研究现状及矿床成因,明确早子沟金矿床为受构造控制明显的热液蚀变岩和石英脉型金矿床,为进一步科学研究及矿产勘查提出建议。

Overview on the metallogenesis of the Zaozigou gold deposit in the west Qinling orogen

The Qinling polymetallic metallogenic belt contains a number of economically important gold deposits in the west section. Due to the lack of systemically study, the metallogenesis has long been a matter of debate. Studies on the newly discovered Zaozigou large gold deposit, located in the West Qinling orogen, have important implications for the genesis of such deposits during crustal evolution, and also provide insight into how deposits within the belt evolve, both geochemically and dynamically. The Zaozigou gold deposit is located in Hezuo-Xiahe area, and represents one of the major gold deposit in the West Qinling polymetallic metallogenic belt. The gold ore bodies are hosted mainly in altered Mesozoic granitoids and faults. Gold mineralization consists of alteration, breccia, and quartz-sulfide vein-types. Alteration assemblages around the ore body show a vertical sequence of potassic, phyllic, and propylitic zones, although not profoundly develop. Pyrite, arsenopyrite and stibnite are the most important ore minerals, associated with minor amounts of galena, sphalerite, and chalcopyrite. Quartz, calcite and sericite are the major gangue minerals. Here in this paper, aiming at further discussing the scientific acknowledgements in the past five years of the Zaozigou deposit, the new observations in our field work of recent years and the previous geochronological and geochemical data are systematically considered. We emphasize the main ore controlling factors (ore-controlling structures temporal-spatial characteristics, and geochronological context) and the dominant metallogenic mechanism (fluid evolution and metal source constrains from isotopic and element geochemistry). It is therefore concluded that the Zaozigou gold deposit is a typical altered rock and quartz vein type gold deposit under structure control, which is expected to be of great value for guiding the approaching mineral exploration and establishing the detailed metallogenic models.