Zircon U–Pb dating, Lu–Hf isotopic composition and geological significance of granites in the Haobugao Pb–Zn deposit, southern Great Xing’an Range, China

Abstract

The Haobugao Pb–Zn deposit located in the southern Great Xing’an Range (SGXR) is one of the most important deposits within the Huanggangliang–Ganzhuermiao polymetallic metallogenic belt. Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite are present in the ore area and are assumed to be closely related to the mineralization. In this study, a new isotopic dating technique, zircon U–Pb laser ablation inductively coupled plasma mass spectrometer analysis, was applied to the granites; the analyses indicate that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite were emplaced at 143.9 ± 1.1 Ma and 151.3 ± 1.4 Ma, respectively. Geochemically, these A-type granites are characterized by relatively high SiO2 and K2O contents, low Al2O3 content, and negative Eu anomalies. Additionally, both granites display strong Rb, Th, U, and Ce enrichment and Ba, K, Sr, and Ti depletion. Their relatively high eHf (t) values (with averages of 7.13 and 7.87, respectively) and young two-stage Nd and Hf model ages indicate that the two granites may have predominantly derived from the partial melting of a juvenile lower crust, followed by fractional crystallization during magma ascent. The geological, elemental, and isotopic evidence shows that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite formed due to the upwelling of mantle-derived alkaline magma and partial melting of the crust, with a certain degree of mixed dyeing, under a tectonic background of asthenosphere upwelling and lithosphere extension via the subduction of the ancient Pacific plate.