Acta Petrologica et Mineralogica

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.

Shangdong; Qujia gold deposit; pyrite; trace element; ore-forming process