MENG Song-ning1,2, MENG Yu-miao2*, HUANG Xiao-wen2, LI Lun3, ZHANG Xin4

(1. College of Earth Sciences, Cheng University of Technology, Chengdu 610059, China;
2. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Science, Guiyang 550081, China;
3. Team 2, Non-Ferrous Metals and Nuclear Industry Geological Exploration Bureau of Guizhou, Liupanshui 553004, China;
4. Faculty of Resources Engineering, Kunming University of Science and Technology, Kunming 650000, China)

Abstract: The Qingshan lead-zinc deposit, located in the Weining－Shuicheng metallogenic belt, is a typical Pb-Zn polymetallic deposit in the northwestern Guizhou deposit concentrated area. In this paper, the textures and compositions of pyrite, marcasite and sphalerite of the Qingshan deposit have been studied in detail through the field investigation combined with the optical microscope, analytical methods of the field emission scanning electron microscope, Laser Raman spetrometer, and electron probe microanalyzer. It is concluded that the deposit was formed by multi-stage fluid mineralization events. Water-rock (or fluid-mineral) reactions and temperature changes could have played important roles in the ore precipitation process. Three mineralization stages in the deposit have been classified. They include the early mineralization stage (S1), main mineralization stage (S2) and late mineralization stage (S3). Five generations of pyrites (Py1 to Py5), three generations of sphalerites (Sp1 to Sp3), two generations of marcasites (Mrc1 and Mrc2), two generations of galenas (Gn1 and Gn2) and two generations of calcites (Cal1 and Cal2) have been identified. The Py1, Mrc1, Py2 and Gn1 were mainly formed in Stage S1; The Py3, Py4, Sp1, Sp2, Gn2, Mrc2 and Cal1 were mainly formed in Stage S2; The Sp3, Py5 and Cal2 were mainly formed in Stage S3. Pyrite is relatively rich in As, Ge, Pb and Au, but poor in Co, Ni and Cu. As and Au occurred possibly as isomorphic substitution in pyrites (Py4 and Py5). Sphalerite is relatively rich in Fe, Cd, Ge, Cl, but poor in Mn, In, Hg, Sb and other trace elements. Fe and Cd occurred possibly as isomorphic substitution in sphalerites (Sp2 and Sp3). The increase of temperature and supersaturation of fluid in the S1 stage fluid evolution process promoted the transformation of marcasite to pyrite, and the primary enrichment of the ore-forming element lead. The S2 stage ore-forming fluid with moderate temperature had strongly interacted with wallrocks (water-rock interaction) which caused the leaching of As and partial ore-forming elements. In the early S2 stage, the ore-forming fluid was in relatively high temperature and relatively stable environment. In the late S2 stage, the ore-forming environment was unstable and the temperature was decreased. This process continued until the S3 stage.

Keywords: Guizhou; Qingshan lead-zinc deposit; Pyrite; Sphalerite; Texture; Chemical composition

ACTA MINERALOGICA SINICA Vol. 43, No. 4, 2023, Page 453