Vapor-phases as Cu transport agents for the shear-zone-hosted mineralization system: A perspective from H-O-S-Cu isotopes

Abstract

Elucidating metal transport agents is the key to understanding the genesis of deposits and tracking the locations of concealed orebodies. Here, we integrate H-O-S-Cu isotopic data from the shear-zone-hosted Lingyun Cu deposit, China, as a means to fingerprint metal transport agents. Sulfide mineralization can be divided into early and late stages, which consist of chalcopyrite + bornite + quartz veins and chalcopyrite + bornite + ankerite veinlets, respectively. Both δ18Ofluid and δD values of fluid inclusions hosted by quartz (δ18Ofluid: 0.5% to 9.9%, δD: –103.9% to –60.1%) and δ65Cu values of sulfides (–1.85% to +0.39%) from the early stage progressively decrease from the southeastern to northwestern portions of the Lingyun deposit, whereas sulfide δ34S simultaneously shifts toward heavier values (–14.4% to 5.0%). The δ34S and δ65Cu values of sulfides from the late stage have restricted ranges from –11.2% to –9.3% and –0.30% to 0.05%, respectively. The possibilities of meteoric water addition, water-rock interaction, inter-mineral Cu partitioning, diffusion, and oxidation could be ruled out as reasons for having caused systematic H-O-S-Cu isotope variations. Vapor-liquid separation resulted in preferential incorporation of light Cu, H, and O isotopes into the vapor phase. The decrease in oxygen fugacity in the fluids resulted in a shift toward heavier δ34S values as fluid flowed outward. Vapor-phases are the dominant transport agents for Cu in the Lingyun deposit, which may be widely applicable to shear-zone-hosted deposits. The direction of progressively increasing δ65Cu, δD, and δ18O values and decreasing δ34S values allows identification of potential locations of concealed orebodies.