U-Pb Isotopic Age and a Further Understanding of the Ore-forming Mechanism in Granite from the Southern Jiangxi Province

Magmatic rocks in the Southern Jiangxi are widely distributed. The diagenetic ages of some rocks are clear, but are still in dispute for others. The U-Pb ages of the Tianxin, Lujing, Shuitou, Baie, Gaoshanjiao, Hanfang, Yangcun, Hunandong, Zhulanbu, Linyang, Dafuzu, Youshan, Huangsha, Yangbu, Wantian and other granites were obtained by using Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICPMS). The data show that these granites did not all intrude in the Yanshanian stage. Although the Tianxin, Lujing, Shuitou, Baie, Hanfang, Yangcun and some granites intruded mainly in the Yanshanian stage, they hosted some earlier zircons, which means most of the rocks experienced a 6-10 Ma crystallization rock-forming history. By comparing with K-Ar and Rb-Sr geochronologies, the granites in the Southern Jiangxi mainly intruded during the Jurassic era. However, areas of Indosinian rocks are substantial, in addition to there being more and more petrogenic information in the early Cambrian and Caledonian eras. All the research results indicate that granites in the Southern Jiangxi experienced a long term evolution and many of them were formed in multiple stages. Although Caledonian rocks were ignored previously since they had no relationship with W deposits, they can be primary rocks for ion-adsorption type rare earth element deposits.