Occurrence and Genesis of Cobalt in the Qiaoxiahala Fe–Cu–Au Deposit, Xinjiang, NW China

Cobalt (Co) is a critical metal for the energy transition, and its enrichment mechanisms are crucial for resource assessment. Here, we investigate Co mineralization in the Qiaoxiahala Fe–Cu–Au deposit through integrated mineralogical, geochemical, and isotopic approaches, including microscopy, SEM, bulk geochemistry, electron-probe microanalysis, and published fluid inclusion data. Co contents range from 17 to 3120 ppm (mean 419.8 ppm); Co-rich samples are commonly enriched in As, Ni and S, whereas Co and Cu vary independently. Here, we identify, for the first time, to our knowledge, discrete cobaltite (CoAsS) as an independent Co mineral in Co-rich ores from the deposit. Cobaltite contains 28.43–34.52 wt.% Co (mean 31.71 wt.%). Among the analyzed sulfides, pyrite has the highest mean Co content (1.17 wt.%; range below detection to 4.16 wt.%), compared with 0.04 wt.% in chalcopyrite and 0.11 wt.% in sphalerite. Chlorite geothermometry yields 224–342 °C, mainly 286–330 °C, indicating intermediate-to-late-stage hydrothermal activity. The Co–Ni association and published Sr–Nd–Pb isotopic data from potential source rocks suggest that Co may have been derived mainly from mafic magmatic rocks and subsequently remobilized by hydrothermal fluids before precipitation in pyrite and cobaltite.