甘肃枣子沟金矿床成矿时代精确测定及其地质意义

Accurate dating of mineralogenetic epoch and its geological significance in Zaozigou gold deposit,Gansu Province

甘肃枣子沟金矿床是西秦岭地区的一处特大型金矿床,围岩主要为三叠系古浪堤组粉砂质、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,矿石主要以细脉浸染状为主;氢氧同位素示踪表明,成矿流体主要为岩浆热液性质的流体,硫、铅同位素研究结果表明,成矿物质具有深源特征。矿床为与闪长玢岩有关的斑岩型金矿床。通过对与成矿有关的2个闪长玢岩锆石SHRIMP U-Pb年龄测试,分别获得(215.5±2.1)Ma和(216.6±2.4)Ma的年龄结果,该年龄代表了枣子沟金矿床的成矿年龄,为形成于印支末期秦岭造山带后碰撞伸展环境。研究表明,西秦岭造山带具有寻找印支末期后碰撞伸展环境有关的斑岩型金矿床的巨大潜力。

The Zaozigou gold deposit in Gansu Province is a super large-scale gold deposit in the western Qinling belt.The silt and argillaceous slates of the Middle Triassic Gulangdi Formation are the wall rock stratum.Gold orebodies with massive veinlet-disseminated ore are mainly hosted in diorite-porphyrite and neighbouring fracture zone.Combined with hydrogen and oxygen isotopic compositions,it is concluded that the main ore-forming fluids derived from the magmatic hydrothermal fluid,sulfur and lead isotope also suggest that ore-forming materials would be of deep origin characteristics.The deposit is a porphyry-type gold deposit related to diorite-porphyrite.SHRIMP U-Pb dating of two diorite-porphyrite Zircons obtains a result of（215.5±2.1）Ma and（216.6±2.4）Ma,indicating that the Zaozigou porphyry-type gold deposit was formed during the end of Indo-China Movement related to the stage of post-collisional extensional environment of Qinling orogenic belt.There are huge potentials in the western Qinling orogenic belt for prospecting porphyry gold deposit of the end stage of Triassic post-collisional extensional environment.