曲家金矿位于我国重要的蚀变岩型金矿矿集区之焦家金矿带的中段,矿床赋存标高为-726 ~-1 334 m。为研究黄铁矿的演化及其对金成矿过程的指示,运用LA-ICP-MS分析黄铁矿原位微量元素含量,结合岩相学观察和点群分析对黄铁矿进行了分类。发现黄铁矿中Co、Ni、As等微量元素主要以类质同像形式赋存,而Au、Ag、Cu、Zn、Pb、Bi等元素主要以纳米级、微米级矿物包裹体形式赋存。黄铁矿主要分为5种类型: 富Co型Py1,富Ni型Py2,富Au、As型Py3,富Au、Ag、Pb、Bi型Py4及"干净"型Py5。黄铁矿微量元素特征指示成矿物质可能主要来源于前寒武纪变质基底岩石和中生代岩浆岩,少量来源于地幔,成矿热液可能属变质热液、岩浆热液和浅部大气降水的混合成因。不同类型黄铁矿反映成矿热液由富Co、Ni经富As、Au向富Pb、Bi、Au、Ag演化。Py1和Py2形成后受构造活动影响发生强烈破碎,裂隙表面对热液中金络合物增强的吸附作用促使金在裂隙中沉淀,对金的富集成矿可能起重要作用。Co、Ni含量较低,同时Au、Ag、As、Pb、Bi等元素含量较高的黄铁矿与成矿作用有密切关系。另外,黄铁矿中Co、Ni含量较高,但破碎强烈,成矿相关元素含量较高为黄铁矿在早期形成并被后期成矿作用改造的特征。
The Qujia gold deposit is located in the central part of the Jiaojia gold metallogenic belt, which is an important concentrated area of altered-type gold deposits in China. The elevation of the deposit ranges from -726 m to -1 334 m. To study the evolution of pyrite and its indicative role in gold mineralization processes, in-situ trace element analysis of pyrite was conducted using LA-ICP-MS. The pyrites were categorized through petrographic observation and cluster analysis. It is revealed that trace elements such as Co, Ni, and As in pyrite mainly in the form of isomorphism, while elements such as Au, Ag, Cu, Zn, Pb, and Bi predominantly exist as mineral inclusions at the nano- and micron-scale. Pyrite is classified into five main types: Co-rich Py1, Ni-rich Py2, Au- and As-rich Py3, Au-, Ag-, Pb-, and Bi-rich Py4, and "clean" Py5. The trace element characteristics of pyrite indicate that ore-forming materials may have primarily originated from Precambrian metamorphic basement rocks and Mesozoic magmatic rocks, with a lesser contribution from the mantle. Ore-forming hydrothermal fluids likely resulted from a complex mix of metamorphic hydrothermal fluids, magmatic hydrothermal fluids, and shallow atmospheric precipitation. The different types of pyrite reflect the evolution of ore-forming hydrothermal fluids from Co- and Ni-rich to As- and Au-rich, and finally to Pb-, Bi-, Au-, and Ag-rich compositions. After the formation of Py1 and Py2, intense tectonic activities caused significant disturbance and enhanced the adsorption of gold complex compounds onto fracture surfaces, promoting gold precipitation within the fractures. This process likely played an important role in gold enrichment and mineralization. Pyrite with low Co and Ni contents but high fragmentation levels, as well as elevated concentrations of Au, Ag, As, Pb, and Bi, is closely associated with mineralization. In addition, the content of Co and Ni in pyrite is high, the crushing is strong, and the content of ore-forming elements is high, which is the characteristics of pyrite formed in the early stage and transformed by the later mineralization.