Early Jurassic porphyry–skarn Cu–Mo–Pb–Zn system in the Erguna Block, NE China: A case study of the Xiahulin deposit

The Xiahulin deposit, recently discovered in the Erguna Block, northeastern China, represents a typical skarn Pb–Zn deposit. However, its ore-forming mechanism, tectonic setting, and role within the regional metallogenic system remain unclear. To address these knowledge gaps, this study investigates H–O–S–Pb isotopes, fluid inclusions (FIs), U–Pb geochronology, and geochemical analyses. At the Xiahulin deposit, Pb–Zn mineralization is noted within the contact zone between the Sinian Ergunahe marble and the Early Jurassic porphyritic granite. The following three mineralization stages were identified: the pre-ore skarn (I), the syn-ore quartz–sulfide (II), and the post-ore quartz–calcite (III). Three types of FIs were observed: vapor-rich, liquid-rich, and halite-bearing. The FI homogenization temperatures for stages I, II, and III range from 345–445 °C, 260–365 °C, and 165–258 °C, with salinities ranging from 6.7–49.1, 4.6–15.6, and 3.7–8.1 wt% NaCl equivalent, respectively. According to H–O isotope information, the ore-forming fluids, after originating from magmatic water, were diluted progressively by meteoric water during migration. The principal mechanisms driving Pb–Zn precipitation were phase separation and dilution. According to the S–Pb isotope information, the porphyritic granite, and the Sinian Ergunahe marble constituted the sources of ore-forming substances. The porphyritic granite, as the causative intrusion, displayed a U–Pb age of 199.7 ± 1.5 Ma, consistent with the regional porphyry Cu–Mo metallogenesis (206–181 Ma). The geochemical characteristics indicate that the intrusions associated with regional porphyry–skarn Cu–Mo–Pb–Zn metallogenesis share similar characteristics, exhibiting adakitic signatures and formation within a subduction-related volcanic arc setting. Herein, we propose an Early Jurassic porphyry–skarn Cu–Mo–Pb–Zn metallogenic model linked to the Mongol–Okhotsk Ocean tectonic regime within the Erguna Block. This model deepens our understanding of regional metallogenic processes and provides insights to guide mineral exploration.