热液磷灰石原位U-Th-Pb定年对右江盆地卡林型金矿床成矿时-空格架的约束

右江盆地是全球仅有的2个卡林型金矿集中区之一，因缺少合适的定年矿物，其精确的成矿时代一直悬而未决，金成矿作用的时-空分布特征尚未得到清晰认识，制约了对这一全球重要成矿区带和重要金矿类型成矿作用的深入理解。磷灰石常含较高的晶格U或Th，并具有较高的U-Th-Pb同位素封闭温度，近年已成功用于国内外热液矿床的精确定年。申请者初步研究显示，右江盆地的锦丰、金牙和高龙等卡林型金矿床中，存在粒径多为10-100微米的磷灰石，它们很可能为热液成因并与金成矿同时。本项目拟选择这些金矿床为对象，通过矿物学和矿物化学研究，系统辨识磷灰石的热液成因属性及其与金成矿的时-空-成因关系，通过与金成矿同时的热液磷灰石的SIMS和/或LA-ICP-MS原位U-Th-Pb定年，建立右江盆地卡林型金矿精确可靠的成矿年代时-空格架。研究成果对揭示右江盆地卡林型金矿的成矿动力学背景、时空分布特征和指导找矿勘查具有重要意义。

The Youjiang basin is one of the two unique Carlin-type gold metallogenic provinces throughout the world. However, the difficulty of precisely determining the mineralization age due to the lack of minerals suitable for radiometric dating, has seriously hindered the understanding of the genesis and geodynamic setting and the knowledge about the temporal and spatial characteristics for this important metallogenic domain and Carlin-type gold mineralization. Hydrothermal apatite, which contains high U and Th contents in their lattice and have high closure temperature for Pb diffusion, have successfully been utilized to precisely constrain the mineralization ages of many important hydrothermal deposits worldwide. Our preliminary research shows that, there exist some fine-grained apatite crystals with 10-100 um in size within the mineralized samples from the representative Jinfeng, Jinya and Gaolong gold deposits in the Youjiang basin. Sporadic evidences suggest these apatite crystals are probably of hydrothermal origin and coprecipitation with gold mineralization. In this contribution, we will take these gold deposits as the studying objective, and systematically demonstrate the temporal, spatial and genetic relationships between the apatite and gold mineralization using mineralogical and geochemical evidences. Then, we will conduct in situ U-Th-Pb dating on these hydrothermal apatites with SIMS and/or LA-ICP-MS, aiming to precisely establish the spatial and temporal framework of Carlin-type gold mineralization in Youjiang basin. Achievements attained in this project will contribute to understand ore genesis and geodynamic setting of Carlin-type gold deposits in the Youjiang basin. And then, the results will reveal the temporal and spatial distribution characteristics, and provide some guidance for regional prospecting.