The Dating and Analysis of Ore-forming Conditions for Hanfang Granite Intrusions in Ganxian, Jiangxi Province

Zircons collected from Hanfang intrusions in Ganxian, Jiangxi province, whose weathered crust produced many rare earth element (REE) deposits, have been dated by using Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICPMS) and are presented here. The dating results from typical magmatic zircons with good shape and oscillatory zoning show that the coarse-grained biotite monzonitic granite intruded in the Caledonian era, during the convergence between Yangtse block and Cathaysia block, and the fine-grained biotite monzonitic granite intruded in the early Yanshan epoch as the results of lithospheric thinning and delamination during subduction of the old Pacific plate to the South China Plate. The granite intrusions formed in the Yanshan epoch have a close relationship with large scale mineralization of W, Sn in the Nanling district, while the intrusions formed in the Caledonian era have a significant contribution to the formation of ion adsorption type REE deposits. The intrusions in the Caledonian era host REE-rich accessory minerals, such as orthite, zircon and fluorite. The fractures of the intrusions were well developed as a result of a few tectonic events. The bad weathering was attributed to the hot and rainy climate in this region. Therefore, the intrusions in the Caledonian era tend to produce ion adsorption type REE deposits for the reasons previously mentioned.