Geology, geochemistry and metallogenesis of the Selinsing gold deposit, central Malaysia

Malaysia is endowed with a number of major sediment-hosted, orogenic gold deposits that lie parallel to but east of the Bentong-Raub Suture Zone, which runs approximately N–S in central Malaysia. The Selinsing gold deposit is one of the major economic deposits in central Malaysia and is hosted by (meta)-sedimentary units. The deposit is affected by later deformation and metamorphism during the Triassic due to the collision of the Sibumasu Terrane with the Sukhothai Arc. Laser ablation ICP-MS U–Pb zircon dating of the host rocks indicates a Carboniferous (ca. 331–300 Ma) maximum depositional age. Ore minerals include pyrite, arsenopyrite, galena, sphalerite, chalcopyrite, pyrrhotite and gold. Detailed textural and geochemical studies revealed five distinctive pyrite types, sub-rounded framboidal pyrite (Pyrite 1), rounded recrystallized pyrite (Pyrite 2), anhedral inclusion-rich pyrite (Pyrite 3), anhedral to subhedral clean pyrite (Pyrite 4) and coarse euhedral clean pyrite (Pyrite 5). Laser ablation ICP-MS trace element analysis of the framboidal pyrite indicates enrichment in V, As, Mo, Ni, Se, Te, Ag, and Zn relative to the other pyrite types. Pyrite sulfur isotope composition (1.2–9.2‰) suggests a likely mixture of magmatic and local sedimentary source for the sulfur. Pyrite Pb isotope results (Pb²⁰⁶/Pb²⁰⁴: 18.94–19.10; Pb²⁰⁷/Pb²⁰⁴: 15.72–15.73) suggest a high-U source rock for the lead. Fluid inclusions are CO₂-rich (95–100 mol%) and yielded homogenization temperatures from 194 to 348 °C and salinities between 1.23 and 9.98 wt.% NaCl equiv. suggesting involvement of metamorphic fluids during ore formation. Based on these results, we suggest a two-stage model for the formation of the gold deposit at Selinsing. Stage 1 consists of early enrichment of the elements Au, V, As, Mo, Se, Te, Ni, Ag, and Zn in framboidal pyrite in the sediments, whereas Stage 2 is characterized by multiple post-diagenetic deformation and metamorphic processes, favoring the development of fluid pathways and Au remobilization into later pyrites. Regionally, the Selinsing gold deposit shares geological similarities (in term of host rocks, ore mineralogy and geochemistry) with many other sediment-hosted, orogenic gold deposits in mainland SE Asia such as the Sepon gold deposit (Laos), Langu gold deposit (Thailand), Modi Taung and Meyon gold deposits (Myanmar), and Phuoc Son gold deposit (central Vietnam). We suggest that our two-stage model may have important implications to mineral exploration for future research on sediment-hosted/orogenic gold deposits in SE Asia.