The Magmatic-Hydrothermal Ore-Forming Processes of the Tonggou Cu-Zn Deposit, NW China: Constraints from Magnetite Chemistry and Fluid Inclusions

The Tonggou deposit is a porphyry Cu and vein-type Cu-Zn mineralization system located in the Bogda Orogenic Belt, north of Eastern Tianshan. Systematic fluid inclusion analyses were performed on granular quartz from magnetite–quartz stage pyrite–chalcopyrite–quartz mineralization. During early mineralization, ore-forming fluids at high temperatures (450–501 °C) salinity (51.2–55.2 wt.% NaCl equiv.) H2O-NaCl hydrothermal with boiling. These evolved to temperature (412–450 intermediate low (8.3–14.2 during stage. In addition, magnetite was studied as marker for process evolution Sampled can be divided into MagI (allotriomorphic altered granodiorite), MagII (magnetite granodiorite found veinlets or aggregates), MagIII (from mineralization), MagIV polymetallic sulfide–epidote–quartz mineralization). Magnetite LA-ICP-MS data indicate origin. contents Ti, Si, Al, Ta are controlled by temperature, these elements gradually decrease MagIV. Moreover, fO2 has considerable influence substitution Sn, V, Mn magnetite, generally MagIII—increasing only Indeed, (MagIV) shown presence replacement texture ilmenite grains within magnetite. On other hand, samples have relatively Ti + V compared deposits—plotting skarn field (Ti V) vs. (Ca Al Mn) diagram—and shows negative correlations Sn diagram. that formed lower conditions than typical deposits. Finally, both sourced system, result transfer different location.