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In-situ geochemical and isotopic analyses of multiple pyrite generations: Insights for the giant Beiya Au polymetallic ore genesis in southwestern China.

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Title: In-situ geochemical and isotopic analyses of multiple pyrite generations: Insights for the giant Beiya Au polymetallic ore genesis in southwestern China.
Authors: Zhang, Hong-Rui1,2 (AUTHOR), He, Wen-Yan1 (AUTHOR) wyhe@cugb.edu.cn, Yang, Li-Qiang1 (AUTHOR), Zhou, Yun-Man3 (AUTHOR), Zhang, Rui-Rui1 (AUTHOR), Zhao, Bo1 (AUTHOR)
Source: Ore Geology Reviews. Aug2024, Vol. 171, pN.PAG-N.PAG. 1p.
Subjects: Ore genesis (Mineralogy), Sulfur isotopes, Isotopic analysis, Pyrites, Analytical geochemistry, Trace elements
Abstract: Box plot of trace element contents in different pyrite types, and comparison of sulfur isotopic compositions of pyrite at related major geological bodies. [Display omitted] • We studied the pyrite texture and chemistry of Beiya Au skarn deposit (SW China). • Pyrite texture and chemistry reveal multi-stage magmatic-hydrothermal mineralization. • Geochemical maps and S isotopes suggest pyrite chemistry is controlled by magma fractionation. The Beiya giant Au polymetallic deposit is located in the Sanjiang Tethyan Orogen, northwestern Yunnan (SW China). The ores occur as disseminations or veinlets in granite porphyry. To unravel the ore genesis at Beiya, we analyzed the ore-related sulfide trace elements and sulfur isotopes. Py-1 is mainly euhedral-subhedral medium-/coarse-grained (size: > 100 μm), with relatively smooth surface and some pores. Py-2 is mostly coarse grained (size: 50–200 μm), with well-developed pores and inclusions. The pyrite is usually Co-Cu rich and V-Ti-Sb poor, resembling typical magmatic-hydrothermal pyrite. In addition, the Co/Ni ratios decrease from pyrite-1 (Py-1) to pyrite-2b (Py-2b), suggesting that their chemical compositions are controlled by magma fractionation. We found that Co, Ni, As, and Se occurred as solid solution in the pyrite lattice, while Pb, Bi, Ag, and Mn occurred mainly in inclusions in the pyrite. Pb and Bi display good positive correlation, suggesting that they occurred as inclusions or nano-particles in pyrite lattice. The pyrite samples have sulfur isotope value (δ 34 S) of 0.62–3.45 ‰ (avg. 2.35 ‰) for Py-1, 0.18–3.12 ‰ (avg. 1.85 ‰) for Py-2a, and 0.62–4.18 ‰ (avg. 2.51 ‰) for Py-2b. These characteristics may have played a vital role in the initial enrichment of Cu, Mo, Au, and ultimately formed the complex polymetallic system at Beiya. [ABSTRACT FROM AUTHOR]
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Abstract:Box plot of trace element contents in different pyrite types, and comparison of sulfur isotopic compositions of pyrite at related major geological bodies. [Display omitted] • We studied the pyrite texture and chemistry of Beiya Au skarn deposit (SW China). • Pyrite texture and chemistry reveal multi-stage magmatic-hydrothermal mineralization. • Geochemical maps and S isotopes suggest pyrite chemistry is controlled by magma fractionation. The Beiya giant Au polymetallic deposit is located in the Sanjiang Tethyan Orogen, northwestern Yunnan (SW China). The ores occur as disseminations or veinlets in granite porphyry. To unravel the ore genesis at Beiya, we analyzed the ore-related sulfide trace elements and sulfur isotopes. Py-1 is mainly euhedral-subhedral medium-/coarse-grained (size: > 100 μm), with relatively smooth surface and some pores. Py-2 is mostly coarse grained (size: 50–200 μm), with well-developed pores and inclusions. The pyrite is usually Co-Cu rich and V-Ti-Sb poor, resembling typical magmatic-hydrothermal pyrite. In addition, the Co/Ni ratios decrease from pyrite-1 (Py-1) to pyrite-2b (Py-2b), suggesting that their chemical compositions are controlled by magma fractionation. We found that Co, Ni, As, and Se occurred as solid solution in the pyrite lattice, while Pb, Bi, Ag, and Mn occurred mainly in inclusions in the pyrite. Pb and Bi display good positive correlation, suggesting that they occurred as inclusions or nano-particles in pyrite lattice. The pyrite samples have sulfur isotope value (δ 34 S) of 0.62–3.45 ‰ (avg. 2.35 ‰) for Py-1, 0.18–3.12 ‰ (avg. 1.85 ‰) for Py-2a, and 0.62–4.18 ‰ (avg. 2.51 ‰) for Py-2b. These characteristics may have played a vital role in the initial enrichment of Cu, Mo, Au, and ultimately formed the complex polymetallic system at Beiya. [ABSTRACT FROM AUTHOR]
ISSN:01691368
DOI:10.1016/j.oregeorev.2024.106195