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

Abstract

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, εNd(t) values of + 0.37 to –0.39, and TDM2 ages of 978–915 Ma. They also have zircon εHf(t) values of 3.6–9.1, TDM2 model ages of 959–608 Ma, and δ18O values of 6.68‰–7.42‰. 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.