Trace element and sulfur isotope compositions of pyrite from the Tianqiao Zn–Pb–Ag deposit in Guizhou province, SW China: implication for the origin of ore-forming fluids

• Published in: Acta geochimica 2022-04, Vol.41 (2), p.226-243
• Main Authors: Meng, Yumiao, Huang, Xiaowen, Xu, Chunxia, Meng, Songning
• Format: Article
• Language: English
• Subjects: Brines; Carbonates; Carboniferous; Chromium; Clay minerals; Copper; Deformation; Deposits; Devonian; Diagenesis; Dolomite; Dolostone; Earth and Environmental Science; Earth Sciences; Economic importance; Fluids; Fractures; Galena; Gallium; Geochemistry; Germanium; Heavy metals; Hydrothermal springs; Hydrothermal vents; Iron oxides; Isotope composition; Isotopes; Lead; Limestone; Low temperature; Metals; Mineral assemblages; Minerals; Nickel; Original Article; Porphyry copper; Pyrite; Rocks; Seawater; Silver; Sphalerite; Sulfides; Sulfur; Sulphides; Texture; Trace elements; Vents; Zinc; Zincblende
• ISSN: 2096-0956; 2365-7499
• DOI: 10.1007/s11631-021-00511-0

The Tianqiao Zn–Pb–Ag deposit in SW China, hosted by Devonian and Carboniferous limestone and clay rocks, is composed of sulfides such as sphalerite, galena, and pyrite. Pyrite is present in different paragenetic stages and can be divided into four types based on textures and mineral assemblages. Pyrite from the adjacent Shanshulin deposit (Py-SSL) is also used for comparison. Py1 shows framboid texture with grain diameter up to 1 mm and was commonly replaced by sphalerite. Py2 is characterized by overgrowth texture and displays inner oscillatory zoning. Py2 is associated with abundant sphalerite and galena. Py3 shows replacement relics textures where galena fills the fractures of pyrite. Py4 is a euhedral to subhedral crystal disseminated in dolomite and is characterized by deformation and fragmentation textures. Minor sphalerite and galena are associated with Py4. Py-SSL is subhedral and disseminated in dolomite, similar to Py4. Py1 was formed by a diagenetic or sedimentary process, whereas Py2 and Py3 were formed by multiple stages of ore fluids. Py4 and Py-SSL were formed at the carbonate-sulfide stage, but Py4 suffered from deformation after its formation. Py1, Py2, and Py3 are characterized by relative enrichment of Sb, Cu, and As, in contrast to Py4 and Py-SSL with higher Cr, W, Ge, Sn, Tl, Ni, and Ga contents. However, critical metals such as Ge, Ga, and In in pyrite are generally lower than 10 ppm, which are not economically important. The trace element variation in Tianqiao pyrite with paragenesis results from fluid evolution in the Pb–Zn ore system and competition with co-precipitating minerals. Diagenetic and ore-forming hydrothermal fluids are responsible for the formation of different types of pyrite. Ore-related pyrite from the Tianqiao and Shanshulin deposits has Co and Ni distribution features similar to pyrite from sedimentary pyrite and submarine hydrothermal vents, different from those in volcanogenic massive sulfide, iron oxide-copper–gold, and porphyry Cu deposits, indicating their derivation of relatively low-temperature (