Geology, geochemistry, and geochronology of the Wangjiazhuang porphyry-breccia Cu(-Mo) deposit in the Zouping volcanic basin, eastern North China Block

The Wangjiazhuang porphyry-breccia Cu(-Mo) deposit is located in the Zouping volcanic basin, western Shandong Province. Seven molybdenite samples yield a Re-Os weighted mean age of 127.8±0.7Ma (2σ), which is identical within error to the zircon weighted mean ²⁰⁶Pb/²³⁸U age of 128.3±1.3Ma (2σ) determined for quartz monzonite samples. The host rock is characterized by high concentrations of K₂O (4.26-4.53wt.%), Na₂O (4.97-5.76wt.%), LILEs and LREEs, and high Mg# (>40), and low concentrations of HFSEs and HREEs, with K₂O/Na₂O ratios of 0.76-0.88. The quartz monzonite also has high Sr/Y (69.9-112.5) and (La/Yb)_N (22.0-30.0) ratios, similar to adakitic rocks worldwide. Relatively low initial ⁸⁷Sr/⁸⁶Sr ratios (0.70549-0.70556), high ε_Nd(t) values (2.58-3.06), high radiogenic Pb [(²⁰⁶Pb/²⁰⁴Pb)i=18.3424-18.4606, (²⁰⁷Pb/²⁰⁴Pb)_i=15.5692-15.5985, (²⁰⁸Pb/²⁰⁴Pb)_i=38.1714-38.2734] and high zircon ε_Hf(t) values (-2.1 to +4.3) indicate that the magma was likely derived from the partial melting of subducted oceanic crust which then reacted with the peridotitic mantle wedge. Both the breccia and porphyry ores have a narrow range of δ³⁴S (-4.8 to +2.1‰) and Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb=18.295-18.402, ²⁰⁷Pb/²⁰⁴Pb=15.551-15.573, and ²⁰⁸Pb/²⁰⁴Pb=38.215-38.331), suggesting that the ore metals were extracted primarily from the quartz monzonite or similar source. Subduction of the Paleo-Pacific slab during the Early Cretaceous resulted in the formation of the Wangjiazhuang quartz monzonite and associated Cu(-Mo) deposit in western Shandong Province.