Geochemical contrasts between Late Triassic ore-bearing and barren intrusions in the Weibao Cu–Pb–Zn deposit, East Kunlun Mountains, NW China: constraints from accessory minerals (zircon and apatite)

The Weibao copper–lead–zinc skarn deposit is located in the northern East Kunlun terrane, NW China. Igneous intrusions in this deposit consist of barren diorite porphyry (U–Pb zircon age of 232.0 ± 2.0 Ma) and ore-bearing quartz diorite and pyroxene diorite (U–Pb zircon ages of 223.3 ± 1.5 and 224.6 ± 2.9 Ma, respectively). Whole-rock major and trace element and accessory mineral (zircon and apatite) composition from these intrusions are studied to examine the different geochemical characteristics of ore-bearing and barren intrusions. Compared to the barren diorite porphyry, the ore-bearing intrusions have higher Ce4+/Ce3+ ratios of zircon and lower Mn contents of apatite, indicating higher oxidation state. Besides, apatite from the ore-bearing intrusions shows higher Cl contents and lower F/Cl ratios. These characteristics collectively suggest the higher productivity of ore-bearing quartz diorite and pyroxene diorite. When compared with ore-bearing intrusions from global porphyry Cu deposits, those from Cu–Pb–Zn skarn deposits display lower Ce4+/Ce3+ and EuN/EuN* ratios of zircon and lower Cl and higher F/Cl ratios of apatite. We conclude that these differences reflect a general geochemical feature, and that zircon and apatite composition is a sensitive tool to infer economic potential of magmas and the resulting mineralization types in intrusion-related exploration targets.