U–Pb and Re–Os Geochronology of the Hucunnan Copper–Molybdenum Deposit in Anhui Province, Southeast China, and its Geological Implications

Abstract

The Middle-Lower Yangtze Region (MLYR) is one of the most important metallogenic belts in China that hosts numerous Cu-Fe-Au-S deposits. The Hucunnan deposit in the central part of MLYR is a newly discovered porphyry-skarn-type copper-molybdenum deposit during recent drilling exploration. Laser ablation ICP-MS analysis carried out in this study yields U-Pb isotopic ages of 137.5 ± 1.2 Ma for the Cu-Mo bearing granodiorite rock and 125.0 ± 1.5 Ma for the Cu-bearing quartz diorites. The Re-Os isotopic dating of seven molybdenite samples gave an isochron age of 139.5 ± 1.1 Ma, suggesting a syn-magma mineralization of molybdenite in the Hucunnan deposit. Since porphyry-type molybdenum deposits are rare in central MLYR, the discovery of the Hucunnan deposit suggests possible molybdenite mineralizations in the deep places of the Cu-Mo bearing granitoids. In addition, the U-Pb isotopic age of 125 Ma for the Cu-bearing quartz diorites implies a new Cu mineralization period for the MLYR that was rarely reported by previous studies.

Geochemical Study of Cretaceous Magmatic Rocks and Related Ores of the Hucunnan Cu–Mo Deposit: Implications for Petrogenesis and Poly-Metal Mineralization in the Tongling Ore-Cluster Region

“…The metallogenic model ages of the Hucunnan Cu-Mo deposit are 138.70 ± 1.87 Ma and 140.03 ± 2.8 Ma, which are consistent with the main metallogenic ages of the Tongling ore-cluster region [19]. The diagenetic age of Hucunnan granodiorite measured by predecessors is 137.5 ± 1.2 Ma [36], indicating that the age of diagenesis and mineralization is basically the same. Therefore, the formation of the Hucunnan Cu-Mo deposit may be closely related to the Hucunnan granodiorite.…”

“…According to previous studies, the diagenetic ages of granodiorite in the Tongling ore cluster are mainly from 147-137 Ma, and the metallogenic ages are mainly from 141-137 Ma [19]. The diagenetic age of Hucunnan granodiorite is 137.5 ± 1.2 Ma [36], and the ages of the metallogenic model are 138.70 ± 1.87 Ma and 140.03 ± 2.8 Ma, which are consistent with the overall diagenetic and metallogenic age of the region, indicating that magmatism and mineralization are inseparable. Research on the major elements of biotite and garnet showed that the ore-forming environment of the Hucunnan Cu-Mo deposit was characterized by high oxygen fugacity.…”

“…They can be used to trace the evolution of the environment and the source of ore-forming materials, and play important roles in judging the As typical porphyry-skarn Cu-Mo polymetallic deposits, the Hucunanan deposit in the Tongling ore-cluster region provides a good example for revealing the magmatic evolution and enrichment and migration of metallogenic materials during the skarn formation process. Previous studies held that the ages of quartz diorites and granodiorite of Hucunan deposit are 125 Ma and 137.5 Ma, respectively [36]. The H-O isotopic signatures and the study of fluid inclusions show that the ore-forming fluids were dominated by magmatic water in the early stages, and gradually mixed with circulating meteoric water in the late stages [37].…”

Genetic Types and Metallogenic Model for the Polymetallic Copper–Gold Deposits in the Tongling Ore District, Anhui Province, Eastern China

“…The Hucunnan Cu-Mo-(Au) deposit is located some 2 km southwest of the Dongguashan deposit ( Figs. 1 and 2a; Chang Yinfo et al, 1991;Zheng Zejun et al, 2015;Yang et al, 2016;Cao et al, 2017). It is a newly discovered porphyry-skarn deposit, which represents a shallow Cu-(Au) dominant skarn system that is underlain by a deeper Cu-Mo dominated porphyry-skarn system (Fig.…”

“…The Dongguashan and Hucunnan are typical porphyryskarn deposits in the Tongling ore district (Xu Xiaochun et al, 2008;Liu Zhongfa et al, 2014;Yuan Feng et al, 2014;Zheng Zejun et al, 2015;Yang et al, 2016).…”