Discussion on Petrogenesis and HREE Pre-Enrichment Mechanism of Zudong Granite in Southern Jiangxi Province

赣南地区，作为我国风化壳型稀土矿床的发现源地，不仅涵盖了轻、重稀土矿床的各类典型，而且构成了南岭地区最具代表性的风化壳型稀土矿床聚集区。该区域内，成矿岩体分布尤为密集。而足洞矿床是一个典型的重稀土钇矿床，由风化壳所发生的离子吸附过程而形成。本研究系统性地剖析了足洞矿区内及其毗邻花岗岩的锆石U-Pb年代学特征，旨在揭示其地质演化的时间框架。结合前人研究成果，探讨足洞花岗岩成岩过程受构造演化的影响以及重稀土预富集机制。综合地质年代学分析表明，该研究区域所采集的样品其成矿作用发生于164 Ma，即中侏罗世(Aalenian期)。南岭地区在侏罗世发生了大规模的岩浆活动和成矿作用，形成了大量的花岗岩以及相关的钨锡、铅锌、REE等多金属矿床，作为南岭地区广泛岩浆成岩与成矿过程的一个环节，足洞地区的岩浆活动显著。随着古太平洋板块的俯冲后撤，华南地区进入了一个全面的拉张-伸展构造环境，正是在这样的地质背景下，足洞花岗岩得以形成。The southern Jiangxi region, being the discovery site of weathering crust-type rare earth deposits in China, not only encompasses various typical light and heavy rare earth element deposits, but also constitutes the most representative weathering crust-type rare earth deposit concentration area in the Nanling region. Within this region, metallogenic rock bodies exhibit particularly dense distribution. The Zudong deposit represents a typical yttrium-rich heavy rare earth element deposit formed through ion adsorption processes within weathering crusts. This study systematically analyzes zircon U-Pb geochronological characteristics of granites within the Zudong mining area and its adjacent regions, aiming to reveal the temporal framework of its geological evolution. Combined with previous research findings, we discuss the influence of tectonic evolution on the diagenetic process of Zudong granite and its heavy rare earth element pre-enrichment mechanism. Comprehensive geochronological analysis indicates that mineralization of the collected samples in the study area occurred at 167 Ma, corresponding to the Middle Jurassic (Aalenian Stage). The Nanling region experienced large-scale magmatic activities and mineralization events during the Jurassic period, forming numerous granites and associated polymetallic deposits including tungsten-tin, lead-zinc, and REE deposits. As part of the extensive magmatic-metallogenic processes in the Nanling region, the magmatic activities in the Zudong area were particularly significant. With the retreat of the Paleo-Pacific Plate subduction, the South China region entered a comprehensive extensional tectonic environment. It was under such a geological background that the Zudong granite was formed.