Ore genesis of the late Paleozoic Shizui Cu-polymetallic deposit in central Jilin Province, Northeast China: Constraints from geochemistry of magnetite, chalcopyrite, and pyrite

In the Shizui skarn-type Cu-polymetallic deposit, the ore-forming fluids might have originated from late Paleozoic monzogranitic magmatism during the early mineralization stage, where a high f O 2 environment promoted the formation of magnetite and generated a large amount of HS − . During the quartz-sulfide stage, a high f S 2 environment controlled the solubility of metal ions in different minerals, leading to the enrichment and precipitation of metal sulfides. • The Shizui Cu-polymetallic deposit is the first recognized late Paleozoic Cu-polymetallic deposit along the eastern segment of the northern margin of the North China Craton. • The S-Pb isotope results indicate that the ore-forming materials of the Shizui Cu-polymetallic deposit are mainly derived from monzogranite. • The Shizui Cu-polymetallic deposit is an early Permian skarn-type deposit. Northeast (NE) China is characterized by a predominance of Mesozoic deposits and a scarcity of Paleozoic deposits. The Paleozoic deposits are mainly distributed along the Xar Moron–Changchun–Yanji suture zone, which holds significant importance for studying the Paleozoic tectonic evolution and mineralization processes of the region. The Shizui Cu-polymetallic deposit in Jilin Province, NE China, is the first recognized late Paleozoic Cu-polymetallic deposit along the eastern segment of the northern margin of the North China Craton (NCC). The mineralization process can be divided into three stages: the skarn stage, the early quartz-sulfide stage, and the late quartz-sulfide stage. The early quartz-sulfide stage is the major stage of Cu mineralization. The metallic minerals developed in the deposit are dominated by magnetite, arsenopyrite, pyrite, chalcopyrite, sphalerite, and galena. In-situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data indicate that in magnetite, Si 4+ and Al 3+ mainly enter the magnetite lattice through isomorphous substitution of Fe 3+ , rather than in the form of micro-inclusions of silicate minerals. Elements such as Pb, Zn, Ag, and Bi exist in chalcopyrite as micro-inclusions, while Au, Ag, Pb, and Sb in pyrite are mainly present in the form of solid solutions. In addition, magnetite, chalcopyrite, and pyrite all exhibit hydrothermal origin. Using the magnetite T Mg-Mag geothermometer, the average T Mg-Mag temperatures of the two generations of magnetite (Mag1 and Mag2) are calculated to be 596 °C and 468 °C, respectively. The δ 34 S values of sulfides range from −3.8 ‰ to −1.3 ‰, with an average of −1.9 ‰, suggesting deep-source magmatic sulfur or mantle sulfur. The Pb isotope compositions of sulfides ( 206 Pb/ 204 Pb = 18.457–18.516, 207 Pb/ 204 Pb = 15.592–15.672, and 208 Pb/ 204 Pb = 38.251–38.517) are consistent with those of monzogranite ( 206 Pb/ 204 Pb = 18.386–19.006, 207 Pb/ 204 Pb = 15.547–15.624, and 208 Pb/ 204 Pb = 38.348–38.667). The S-Pb isotope results indicate that the ore materials are mainly derived from the magmas forming the monzogranite. During the late Paleozoic, magmatic fluids underwent reactions with carbonate wall rocks under high oxygen fugacity ( f O 2 ) conditions, forming magnetite containing Si and Al. As the sulfur fugacity ( f S 2 ) in the hydrothermal system increased, the elevated concentration of HS − drove the precipitation of sulfides such as chalcopyrite, sphalerite, and galena, ultimately forming the Shizui skarn-type Cu-polymetallic deposit. Comprehensive analysis indicates that the Shizui Cu-polymetallic deposit is an early Permian skarn-type deposit, and the ore-forming materials are similar to that of the skarn-type Cu-polymetallic deposits in the Tianbaoshan ore district, both associated with the late Paleozoic intermediate-acidic intrusions. This suggests that the Xar Moron-Changchun Metallogenic Belt (XCMB) extends eastward and has significant prospecting potential for exploring late Paleozoic Cu-polymetallic deposits.