胶东东部金青顶金矿床成因：硫化物矿石与围岩微量元素的制约

金青顶矿床是胶东东部牟平-乳山成矿带最大的金矿床(＞35 t, 平均品位10 g/t), 矿化类型主要为硫化物石英脉型。在野外地质调查的基础上, 利用微量元素组成对金青顶矿床的成矿流体地球化学性质和成矿物质来源进行了研究, 并将金青顶矿床成因确定为受断裂控制的热液脉型金矿床。矿石稀土元素总量变化范围较大, 呈现出明显的轻稀土元素富集和重稀土元素亏损的特征(LREE/HREE=16.75~50.60), 负Eu异常显著, Ce异常不明显。Hf/Sm、Th/La、Nb/La等特征元素比值均小于1, 暗示成矿流体为富Cl体系。结合前人稳定同位素的研究, Ⅰ~Ⅱ阶段矿石δEu值逐渐减小, 可能有大气降水的加入, 说明金青顶矿床成矿流体为岩浆水和大气降水混合来源热液。硫化物矿石、蚀变和新鲜围岩Y/Ho值显示, 蚀变的围岩可为金成矿作用提供必要的成矿物质。

Genesis of Jinqingding gold deposit in eastern Jiaodong Peninsula: constrain from trace elements of sulfide ore and wall-rock

The Jinqingding deposit is the largest gold deposit(> 35 t, average grade 10 g/t) within the Muping-Rushan metallogenic belt of eastern Jiaodong, and the main mineralization category is sulfide quartz-vein category.Based on the study of geological survey as well as trace element composition systematically, the geochemical characteristics of ore-forming fluid and source of ore-forming materials are constrained, and conducts the genesis of Jinqingding deposit as a hydrothermal vein-type gold deposit controlled by faults.In this study, the total rare earth elements(ΣREEs) in the ore varies widely, showing obvious light rare earth elements enrichment and heavy rare earth elements depletion(LREE/HREE=16.75~50.60), with strong negative Eu anomaly and insignificant Ce anomaly.The ratios of Hf/Sm, Th/La, and Nb/La are all less than 1, suggesting that the ore-forming fluid belongs to Cl-rich system.Combined with previous studies on stable isotopes, the δEu value of the ore from stage Ⅰ to Ⅱ gradually decreases in this study, and there may be the addition of meteoric water, indicating that the ore-forming fluid is a mixture of magmatic water and meteoric water.The Y/Ho ratio of sulfide ore, altered and fresh wall-rock implies that altered wall-rock can provide the necessary ore-forming material for gold mineralization.