Mineralization age, tectonic setting and ore genesis of the Wuxing Pt-Pd-rich magmatic Cu-Ni sulfide deposit, Northeast China

The Wuxing deposit in Northeast China, tectonically located in the Jiamusi-Khanka Block, is a Pt-Pd-rich Cu-Ni sulfide deposit related to mafic-ultramafic rocks. The zircon U-Pb ages of pyroxenites, gabbros, porphyritic granites, and leucogranits in the mining area are 516.7 +/- 2.6, 513.8 +/- 2.0, 505.4 +/- 2.3 and 499.5 +/- 2.9 Ma, respectively, indicating that the diagenesis and metallogenesis of the Wuxing deposit occurred during the Cambrian. The ore-forming complex is cut by quartz diorite porphyritic and plagiogranite porphyry dikes. Zircon U-Pb ages of the quartz diorite porphyrite and plagiogranite porphyry are 206.6 +/- 2.1 and 201.6 +/- 1.3 Ma, respectively. The U-Pb ages indicate the metallogenic age constraint of 516.7 +/- 2.6 Ma for the Wuxing deposit, rather than Cambrian and Triassic magmatic activities. The Hf isotopic composition epsilon Hf(t) of zircons in the pyroxenites and gabbros are -11.5 to -7.7 and -5.8 to -2.5, with the two-stage model ages (tDM2) of 2198-1958 and 1841-1633 Ma, respectively. Geochemically, the mafic-ultramafic complexes are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and depleted in high-field strength elements (HFSE), indicating these rocks originated from the enriched mantle. The porphyritic granites are high-K calc-alkaline rocks (Rittman index 3 = 1.92-2.00), and the leucogranites are low-K alkaline rocks (3 = 4.76-4.86) with epsilon Hf(t) and tDM2 of -9.2 to +0.8 and 2037-1411 Ma, respectively. The porphyritic granites and leucogranites are characterized by low A/CNK values (0.91-1.05), 10,000 Ga/Al values (1.76-2.36), and Zr saturation temperature (731-823 celcius) similar to those of I-type granites. Along with contemporaneous intrusions, the Wuxing deposit is inferred to have formed in a post-collisional extension environment. Consequently, the origin of the Wuxing deposit is likely related to the evolution of enriched mantle magma during the Cambrian post-collision extensional setting of the Jiamusi-Khanka Block.