Chronology, Geochemistry and Geological Significance of Epo Granite Intrusion, Southern Jiangxi

The Epo intrusion with an exposed area of 200 km², is mainly composed of biotite monzonitic granite, and is located on the western margin of the Yudu-Qingtang basin, the conjunction of E-W trending Nanling tectonic-magmatic belt and the NNE trending Wuyishan tectonic belt. Situated in such a special tectonic position, this region is advantageous to mineralization. The Yinkeng ore field, which lies to the west of the Epo intrusion, consists of Au-Ag-Pb-Zn and W polymetallic deposits. On the basis of field survey, zircon U-Pb dating for Epo biotite monzonitic granite has been carried out by Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICP-MS). Magma series and petrogenesis have been discussed according to geochemical data, and metallogenetic potentiality of the intrusion has been studied by comparing with other metallogenetic granitic bodies in the district. Analysis results show that the diagenetic age of Epo granite is (412.5±1.7) Ma. The granite contains abundant aluminium minerals, such as muscovite and sillimanite. Major and trace elements indicate that Epo granite is strongly peraluminous S-type granite, and belongs to the High potassium calc alkaline-shoshonite series. The pluton stemmed from Neoproterozoic metamorphic shale by remelting and intruding during the Late Caledonian period. Comparative research with Caledonian and Yanshanian W-Sn metallogenetic granites shows that W and Sn had been concentrated during the formation of Epo granite. Proof that the previous Rb-Sr whole rock isochron age (307 Ma) represents a late geological event after the diagenesis period is given in this paper, and Caledonian granites have potential for W-Sn mineralization.