福建华安地区花岗岩锆石U-Pb年代学、岩石地球化学特征及其与华安玉成矿的关系

Petrogeochemical Characteristics and Zircon U-Pb Age of Granite in the Hua’an Region, Fujian Province and their Relaition with Hua’an Jade Minerlaization

华安玉的形成与区域花岗岩的分布关系密切。对与华安玉形成密切相关的花岗岩进行了岩石地球化学、LA-ICP-MS锆石U-Pb年代学研究,分析其岩石成因、形成时代、构造环境及其与华安玉成矿的关系。研究认为,区内与华安玉成矿最密切相关的岩体为似斑状(中)细粒正长花岗岩,具高硅、富碱、贫钙镁,属弱过铝质-过铝质,具高分异壳源型特点,LA-ICP-MS锆石U-Pb法测得其结晶年龄为(123±1.5)Ma。华安玉的成矿与区域花岗岩多期次侵入活动关系密切,结合矿物组合等研究认为华安玉矿床成因为接触交代型(矽卡岩型)。似斑状(中)细粒正长花岗岩的成岩时代代表了华安玉的主要成矿时代(主成矿期),华安玉主要形成于早白垩世中期。

The formation of Hua'an Jade is closely related to the distribution of regional granites, but previous studies of the granites in this area are still very weak. In this paper, the petrogeochemistry, LA-ICP-MS zircon U-Pb chronology studies of granites in Hua'an Jade Mining Area have been carried out to explore their petrogenesis, formation age, tectonic environment and their relationship with mineralization. The granite is biotite syenite granite ,characteristic of high silicon, rich alkali, poor calcium and magnesium belongs to prealuminous granite,and highly differentiated crustal type . The U-Pb dating of LA-ICP-MS zircon yields a crystallization age of 123+1.5Ma (MSWD=1.8, n=22). The mineralization of Huaan Jade is closely related to the multi-stage intrusion of regional granite. Combined with mineral assemblages, it is considered that the Huaan Jade deposit is of contact metasomatic type (skarn type). The diagenetic epoch of porphyritic (medium) fine-grained syenite represents the main metallogenic epoch (main metallogenic epoch) of Huaan Jade, which was mainly formed in the middle of Early Cretaceous .