A newly Found Biotite Syenogranite in the Huangshaping Polymetallic Deposit, South China: Insights into Cu Mineralization

The W-Sn-Mo-Cu-Pb-Zn polymetallic mineralization in the Huangshaping Deposit is associated with different types of Jurassic granitic intrusions such as quartz porphyry, granophyre and granite porphyry. In this study, we carried out detailed mineralogical, petrological, geochemical, zircon U-Pb geochronological and Hf isotopic studies on a newly found, Cu-mineralization-related fine-grained biotite syenogranite at Huangshaping. This syenogranite is mainly composed of quartz (40%), K-feldspar (30%), plagioclase (15%) and biotite (5%), enriching in SiO 2 (75.58 wt.%–76.02 wt.%), K 2 O (5.24 wt.%–5.78 wt.%), Al 2 O 3 (12.23 wt.%–12.46 wt.%), Rb (405 ppm–504 ppm), U (18.5 ppm–40.7 ppm), Th (47 ppm–52.3 ppm), Nb (49.6 ppm–57.5 ppm), and Cu (54 ppm–288 ppm) whereas depleting in P 2 O 5 (0.01 wt.%), TiO 2 (0.05 wt.%–0.06 wt.%), Ba (5 ppm–13.1 ppm), Sr (6.8 ppm–23.9 ppm) and Eu (0.04 ppm–0.05 ppm), with A1-type alkaline granite characteristics. Magmatic and hydrothermal zircons were separated from a Cu-mineralized syenogranite sample and yielded the 206 Pb/ 238 U concordant ages of 156.5±1.8 and 154.4±2.9 Ma, representing the intrusive age of the pluton and probable Cu-mineralization time at the Huangshaping Deposit, respectively. Zircon Hf isotopes suggest a crust-derived (partial melting of Paleoproterozoic basement) magma for the syenogranite, with some degree of crust-mantle interaction. We infer that the syenogranite is a transitional phase between the granophyre and the granite porphyry, not only contributed greatly to the Cu mineralization but also provided W-Sn polymetallic ore-forming metals for the Huangshaping Deposit.