Ore genesis of the large Narenwula W polymetallic deposit, NE China: Evidence from mineral geochemistry and in-situ S isotope analyses of sulfides

Abstract

Sulfide geochemistry has been extensively used to elucidate ore-forming processes in diverse ore deposits, but its application in granite-related W polymetallic mineralization systems remains limited. The Narenwula deposit (89950 t WO₃ @ 0.78 %, 26,700 t Zn @ 1.23 %, 8100 t Pb @ 1.06 %, and 3100 t Cu @ 1.51 %), located in the eastern Inner Mongolia, is a large-scale quartz-vein type W polymetallic deposit in NE China. In this study, we present a detailed investigation of the deposit geology, in-situ S isotope, and geochemical compositions of wolframite and sulfides to constrain the genesis of the Narenwula deposit. The hydrothermal process can be divided into four stages: stage 1 is dominated by wolframite, and represents the dominant stage of W mineralization; stage 2 features the development of coexisting wolframite, pyrite, arsenopyrite, and chalcopyrite; stage 3 is the predominant stage of sulfide mineralization; and stage 4 is characterized by the occurrence of quartz, carbonate, fluorite, and minor amounts of pyrite. The δ³⁴S values of sulfides from different stages vary from 4.68 to 7.02 ‰, indicating the sulfur originated from granitic magmas. LA-ICP-MS trace element analyses reveal that two-stage wolframite displays analogical trace elements and REE_N patterns, as well as relatively constant Nb/Ta and Y/Ho ratios. Combined with consistent Co/Ni (mainly 1–10) and high As/Ni ratios (> 10) of pyrite from three stages, we suggest that the multistage hydrothermal fluids originated from a common source–a highly evolved granitic magma. Wolframite, pyrite, arsenopyrite, and chalcopyrite are all important trace element carriers, but element enrichment varies markedly among these minerals: wolframite is enriched in Ti, Zr, Sc, Nb, Ta, and HREEs, pyrite in As, arsenopyrite in Sb and Te, and chalcopyrite in Zn, Cd, In, and Sn. These elements are primarily incorporated into mineral lattices as solid solutions. From early to late stage, the fluid temperature and oxygen fugacity decreased, as indicated by the systematic variations of trace element contents in wolframite and sulfides. Greisenization is genetically linked to W mineralization, whereas sericitization promotes the formation of stage 3 sulfide mineralization. Our findings highlight the significance of in-situ mineral geochemical analyses in revealing the origin, composition, and evolution of ore minerals in quartz-vein W polymetallic deposits, which is critical for elucidating detailed ore-forming processes of intrusion-related W polymetallic mineralization systems in NE China and globally.