Zircon U-Pb geochronology and Sr-Nd-Hf-O isotopic constraints on the relationship between Mo and Pb-Zn mineralization in the Haisugou pluton in the southern Great Xing?an Range, northeast China

The Haisugou pluton and its contact zones with Middle Permian strata contain Cu-Mo and Pb-Zn ore deposits, providing an excellent example to study the relationship between Pb-Zn-Ag and Mo mineralization in the southern Great Xing'an Range (SGXR). Here we present U-Pb zircon ages and Sr-Nd-Hf-O isotope data for biotite monzogranite in the Xiaojingzi Pb-Zn deposit and Mo-bearing biotite monzogranite in the Xiaojingzi Cu-Mo deposit. These rocks yield zircon U-Pb ages of 136.2 +/- 1.1 and 135.5 +/- 1.3 Ma, respectively. The biotite monzogranites are enriched in SiO2 (average = 68.9 wt%) and Na2O + K2O (average = 7.7 wt%), contain 14.3-15.1 wt% Al2O3 (average = 14.7 wt%), and have A/CNK values of 0.97-1.05, indicating the biotite monzogranites are high-K calc-alkaline granites, and peraluminous. The biotite monzogranites are also characterized by negative Eu anomalies (Eu/Eu* = 0.78-0.45), enrichments in Rb, Th, U, Nd, and Hf, and depletions in Ba, Sr, P, Ti, and Nb. The biotite monzogranites have (87Sr/86Sr)i ratios of 0.70519-0.70457, epsilon Nd(t) values of + 0.37 to -0.39, and TDM2 ages of 978-915 Ma. They also have zircon epsilon Hf(t) values of 3.6-9.1, TDM2 model ages of 959-608 Ma, and delta 18O values of 6.68 parts per thousand-7.42 parts per thousand. The Mo and Pb-Zn mineralization around the Haisugou pluton were genetically related to the granitic pluton and occurred simultaneously, forming a porphyry system. Geochemical and Sr-Nd-Hf-O isotope data indicate the Haisugou pluton was probably formed by partial melting of juvenile crust and mixing with mantle-derived components. In the Early Cretaceous, the SGXR was in an extensional setting, which was related to asthenospheric upwelling after the closure of the Mongol-Okhotsk Ocean.