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 εNd(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 εHf(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.