粤西黄泥坑金矿床地质地球化学特征和成矿时代

Geological and geochemical characteristics and metallogenic age of Huangnikeng gold deposit in western Guangdong Province

粤西黄泥坑金矿是近年来新发现的一个中-大型金矿床。其成矿作用分为石英-黄铁矿阶段、石英-多金属硫化物阶段和石英-碳酸盐阶段。其中,石英-黄铁矿阶段为金的主成矿阶段。对含金石英脉进行了流体包裹体Rb-Sr同位素定年,获得等时线年龄为(233.4±8.6)Ma(MSWD=2.3,n=5),表明黄泥坑金矿形成于印支期。对矿区花岗闪长岩进行了锆石LA-ICP-MS U-Pb定年,获得的206Pb/238U加权平均年龄为(451.1±2.7)Ma(MSWD=2.1,n=21),表明其形成于加里东期。综合分析花岗闪长岩和矿石的微量元素分析数据及已有的研究成果显示,黄泥坑金矿床中金的来源并非加里东期花岗闪长岩,可能来自于寒武系及隐伏的晚期岩浆岩。矿床的形成主要受罗定-广宁推覆构造控制,挤压推覆后拉张剪切作用形成的剪切破碎带及其热液蚀变作用与成矿密切相关。

The Huangnikeng gold deposit in western Guangdong Province is a newly discovered middle-large sized gold deposit. Its ore-forming process can be divided into three stages, i.e., quartz-pyrite stage, quartz-polymetallic sulfide stage and quartz-carbonate stage, with the first stage being the main metallogenic stage. The fluid inclusions of quartz from ore-bearing quartz-veins samples yielded a Rb-Sr isochron age of （233.4±8.6） Ma （MSWD=2.3, n=5）, interpreted as the gold ore-forming age. LA-ICP-MS U-Pb dating of zircons from the granodiorite yielded 206Pb/238U weighted mean age of （451.1±2.7） Ma （MSWD=2.1, n=21）, indicative of the Caledonian origin. The trace element data of the granodiorites and quartz-vein ores, combined with previous studies, suggest that the gold source was probably derived from the Cambrian strata or later concealed magmatic body rather than from the Caledonian granodiorite. The deposit is mainly controlled by the Luoding-Guangning nappe structure. The shear fracture zone and hydrothermal alteration caused by the tensile and shearing stress after the nappe structure was closely related to the formation of this gold deposit.