Control of the large-sized Mesozoic W-Sn mineralization in southern Hunan: Insights from zircon geochronology and trace element geochemistry

Based on detrital zircons from Sinian, Devonian, Carboniferous and Cretaceous clastic rocks and magmatic zircons from Indosinian-Yanshanian granites in southern Hunan, the control of Mesozoic W-Sn large-sized mineralization in southern Hunan are discussed through zircon U-Pb geochronology and trace element geochemistry.Zircon geochronology shows that the detrital zircon age is lacking of the peak at 2.0 Ga, indicating that the provenance of the Sinian and Late Paleozoic sedimentary basins in southern Hunan is related to the Cathaysia block, but not to the Yangtze block, which can represent the record of the Cathaysia block magmatic activity in the study area.The age spectrum peaks of detrital zircons records six periods of pre-Mesozoic tectonic-magmatic events of the Cathaysia Block, including 2.5 Ga, 1.3~1.1 Ga, 950 Ma, 800 Ma, 650 Ma, and 430 Ma, respectively.These periods correspond to the early formation of Precambrian continental crust, Grenville collision orogeny event, and the amalgamation and splitting of the Rodinia supercontinent.The zircon δEu, LREE/HREE, Y/Ho, and Nb/Ta values of the same tectonic-magmatic event in South Hunan vary greatly. With the age getting younger, the LREE /HREE and Nb/Ta values tend to be larger, suggesting that the magma differentiation degree has nothing to do with age.The zircon ∑REE, Y, Th, U, Nb and Ta contents as well as LREE/HREE and Nb/Ta values increase with ages becoming younger, suggesting that the compositional maturity of source area increases accordingly.The results indicate that the scale of tungsten-tin mineralization in southern Hunan increases with times and reaches its peak in Mesozoic, which is closely related to the increasing crustal maturity.The zircon trace elements can be used as an important index to trace the scale of W-Sn mineralization.