Work

Fluid sources and genetic mechanism of the Zhaishang gold deposit, West Qinling Orogen: Constraints from textures, trace elements, and in-situ S-Pb isotopes of pyrite

Year: 2026

Type: article

Abstract: • Primary gold mineralization derived from metamorphic fluid source. • Superimposed mineralization derived from magmatic fluid source formed high-grade ores. • A genetic model is proposed for gold deposits in the West Qinling Orogen. The fluid sources and genetic mechanisms of the giant Zhaishang gold deposit in the West Qinling Orogen remain debated. This study integrates geological observations with textural, trace element, and in-situ S–Pb isotopic analyses of pyrite to address this issue. Four distinct generations of pyrite (Py I –Py Ⅳ ) are recognized. The Py I occurs parallel to cleavage and displays porous textures associated with sericite and quartz alteration. The Py I δ 34 S values range from +21.0 ‰ to +25.9 ‰ in Devonian strata, and from +1.9 ‰ to +2.9 ‰ in Permian strata, both of which are interpreted to be of diagenetic origin. The Py II is texturally characterized by porous cores and overgrowth rims, and is associated with calcite-ankerite alteration in Devonian strata (Py II-D ) and quartz alteration in Permian strata (Py II-P ). The primary gold enrichment is localized in the core of Py II-D and the rim of Py II-P . In the high-grade ores, the Py III is associated with polymetallic sulfide mineralization and ankerite-siderite alteration, and exhibits a distinct core-mantle-rim texture. The Py III exhibits repeated Au-rich zones in both cores and rims. The Py II-D has δ 34 S values of +9.8 ‰ to +14.0 ‰ (average = +12.0 ‰), and Py II-P ranges from –6.5 ‰ to –4.2 ‰ (average = –5.3 ‰). The S isotopic signatures of Py II , which are similar to those of global sediment-hosted orogenic gold deposits, together with the Pb isotopic data, collectively support a metamorphic fluid origin. In contrast, the narrow variation of δ 34 S values (–2.8 ‰ to +0.4 ‰), Pb isotopic signatures and high Co/Ni ratios, are indicative of magmatic fluids for high-grade gold mineralization. The Py Ⅳ is associated with native gold and LMCE minerals (low-melting point chalcophile elements) in calcite veinlets. Combined with the LMCE-rich characteristics of Py III , the dissolution-reprecipitation of pyrite driven by magmatic-hydrothermal fluids, which remobilized both LMCE elements and Au, is considered the primary mechanism for high-grade mineralization. We conclude that multistage mineralization involving metamorphic and subsequent magmatic fluid superimposition led to the formation of the Zhaishang deposit, a model that may also apply to other gold systems in the West Qinling Orogen.

Source: Ore Geology Reviews

DOI: 10.1016/j.oregeorev.2026.107131