Abstract:
The Kukaazi Pb-Zn polymetallic deposit is located in Xihexiu township, Yecheng county, Xinjiang. The mining area comprises eastern, southern, and northern ore sections. The ore bodies occur predominantly as lenticular and vein-type formations hosted between the Mesoproterozoic Changcheng system marble, garnet-rich skarn, marble, and metamorphic tuff, exhibiting strata-bound characteristics. The genetic type of this deposit remains inadequately constrained. Therefore, this study endeavors to conduct in situ micro-area trace element analysis of pyrite and pyrrhotite from the mining area using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The trace element signatures of these minerals will subsequently be utilized to constrain the genesis of the deposit. The results demonstrate that pyrite is characterized by enrichment in Ni (mean 43.7×10
−6) and Se (mean 49.1×10
−6), depletion in Co (mean 0.71×10
−6), and extremely low Co/Ni ratios (0.01 – 0.02). Cu and Sn contents are consistently <1 ppm, collectively indicating a low-temperature sedimentary origin. Pyrrhotite exhibits significantly elevated Co and Ni contents compared to pyrite (mean values: 188 ppm and 205 ppm, respectively). The Co/Ni ratios range between 0.02 – 0.67 and 1.58 – 1.74, suggesting multiple mineralization events. Furthermore, trace element occurrence modes reveal that in pyrite, Co, Ni, Mn, and Se exist primarily through isomorphic substitution of Fe or S atoms in the crystal lattice, while Pb and Bi occur as nanoscale particles (typically <100 nm).In pyrrhotite, however, Pb and Bi manifest as micron-sized inclusions (1 – 10 μm). Based on integrated evidence from previous studies, Sb/Bi ratios, and regional Caledonian magmatism (460 – 450 Ma), the deposit is interpreted as having an initial submarine hydrothermal-sedimentary origin, overprinted by Ordovician magmatic-hydrothermal modification. This research establishes key geochemical constraints on multi-stage mineralization events in the West Kunlun Orogen.