河北大白阳金矿床黄铁矿微量元素及S-Pb同位素地球化学特征

大白阳金矿床位于华北克拉通北缘张家口地区，为一中型金矿床。矿床产于太古宇桑干群化家营组和涧沟河组变质地层中，受区内断裂和褶皱控制，金矿脉总体走向北北西。矿石类型为含金石英脉型和蚀变岩型，矿石矿物主要为磁铁矿、赤铁矿、黄铁矿、方铅矿、闪锌矿、黄铜矿、斑铜矿、自然金、银金矿及少量碲化物。矿床的成矿期可划分为4个成矿阶段，分别为石英-钾长石阶段、石英-黄铁矿阶段、石英-多硫化物阶段和石英-碳酸盐-硫酸盐阶段。矿床硫化物的δ³⁴S_V-CDT为-16.2‰~-10.5‰，为高氧逸度成矿流体所致；Pb同位素组成²⁰⁶Pb/²⁰⁴Pb=16.762~17.293、²⁰⁷Pb/²⁰⁴Pb=15.350~15.463、²⁰⁸Pb/²⁰⁴Pb=36.777~37.328，与区内岩浆岩Pb同位素组成一致。黄铁矿微量元素低，主要赋存于黄铁矿晶格中。黄铁矿中低的Co、Ni质量分数表明，黄铁矿从岩浆流体中沉淀。桑干群斜长角闪岩在蚀变过程中为流体提供部分成矿物质，为矿源层之一。大白阳金矿床属于与岩浆有关的热液矿床，其形成经历了泥盆纪金的初始矿化和侏罗纪-白垩纪的叠加成矿，由此也导致了张宣地区大量金矿床的出现。

Pyrite Trace Element Composition and S-Pb Isotope Characters of the Dabaiyang Gold Deposit,Hebei Province

The Dabaiyang gold deposit is located in the Zhangjiakou district of the north margin of the North China craton. It is a middle-scale gold deposit. The ore bodies are hosted in the Huajiaying Formation and Jiangouhe Formation of the Archean Sanggan Group, and controlled by faults and folds with general strikes of north-northwest. The ore types are gold-bearing quartz vein type and altered rock type. The main minerals are magnetite, hematite, pyrite, galena, sphalerite, chalcopyrite, bornite, native silver, native gold, electrum,and tellurides. Four mineralization stages are recognized, i.e. quartz-k-feldspar stage, quartz-pyrite stage, quartz-sulfides stage, and quartz-carbonate-sulfate stage. The δ³⁴S_V-CDT values of sulfide range from -16.2‰ to -10.5‰, which are resulted from the highly oxidizing ore-forming fluids. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb,and ²⁰⁸Pb/²⁰⁴Pb values are 16.762-17.293, 15.350-15.463,and 36.777-37.328, respectively. The stable isotope compositions indicate that the ore metals were mostly derived from magmatic fluid. The contents of trace elements in pyrite are low, and mostly in the pyrite lattice. The low Co and Ni concentrations suggest that the pyrite precipitated from magmatic hydrothermal fluid. The amphibolite of the Sanggan Group provides a part of materials for ore-forming fluids, an important source bed. The Dabaiyang gold deposit is a magma-related hydrothermal deposit, which experienced initial gold mineralization in the Devonian and overprinting during the Jurassic-Cretaceous, which also resulted in the large amounts of gold deposits in the Zhangjiakou Xuanhua district.