Garnet and Zircon U-Pb Geochronology and Geochemistry Reveal Genesis of the Dafang Au-Pb-Zn-Ag Deposit, Southern Hunan

Abstract

Garnet is a primary mineral in skarn deposits and plays a significant role in recording copious mineralization and metallogenic information. This study systematically investigates the geochemistry and geochronology of garnet and zircon in the Dafang Au-Pb-Zn-Ag deposit, which represents prominent gold mineralization in southern Hunan, China. Garnet samples with distinct zoning patterns and compositional variations were identified using various analytical techniques, including Backscattered Electron (BSE) imaging, Cathodoluminescence (CL) response, textural characterization, and analysis of rare-earth elements (REE), major contents, and trace element compositions. The garnet was dated U-Pb dating, which yielded a lower intercept age of 161.06 ± 1.93 Ma. This age is older than the underlying granodiorite porphyry, which has a concordia age of 155.13 ± 0.95 Ma determined by zircon U-Pb dating. These results suggest that the gold mineralization may be related to the concealed granite. Two groups of garnet changed from depleted Al garnet to enriched Al garnet, and the rare earth element (REE) patterns of these groups were converted from light REE (LREE)-enriched and heavy REE (HREE)-depleted with positive europium (Eu) anomalies to medium REE (MREE)-enriched from core to rim zoning. The different REE patterns of garnet in various zones may be attributed to changes in the fluid environment and late superposition alteration. The development of distal skarn in the southern Hunan could be a significant indicator for identifying gold mineralization.