Geochronology, Isotopic Geochemistry of Diorite Porphyrite in Tianming Gold Deposit, Hunan

The exploration in the Tianming Mining Area, Anhua, Hunan, has uncovered the concealed mica−plagioclase lamprophyre. In order to study the relationship between the dike and mineralization, we conducted various studies including petrographic, LA−ICP−MS zircon U−Pb chronology, whole−rock major and trace elements and Sr−Nd isotope composition analyses on the mica-plagioclase lamprophyre. The results indicate that the mica−plagioclase lamprophyre underwent significant carbonate alteration. The diagenesis age is estimated to be no earlier than 104 Ma and may be a response to the Late Yanshanian tectonic−magmatic events in South China Block. The concordant ages of (418.79±1.57) Ma and (2506±14 )Ma document the events of Silurian arc−crust collision of the Yangtze plate and the Cathaysia island arc, and Archaean crustal accretion, respectively, indicating the crystal basement material source. The mica−plagioclase lamprophyre belongs to a high−K calcium−alkaline series with an enriched light rare−earth element (LREE) and depleted heavy rare−earth element (HREE), with Eu negative anomalies and Ce positive anomalies. The rock also has large ionic lithophile and high−field strength elements depleted and high compatible element content. Whole−rock εNd(t) values ranging from −8.28 to −7.61 suggest crust−mantle mixing. Our findings suggest that the mica−plagioclase lamprophyre was formed by mantle magma in the source area with residual hornblende, ilmenite, and/or rutile. It underwent fractional crystallization dominant of plagioclase, was mixed by crust, and finally intruded in near−EW faulting tectonics. Comparison of the Au and Sb contents of dikes in central Hunan, ore−bearing formation, and crust, implies that the dikes and antimony may have deep homology. These findings suggest that the Tianming deposit has antimony mineralization potential. Overall, the study highlights the complex geological processes that lead to the formation of mineral deposits. By using a multidisciplinary approach, it is able to unravel the complex history of the mica−plagioclase lamprophyre and its association with mineralization. These findings can provide valuable insights for future exploration activities in the region.