准东卡姆斯特地区中新生代隆升-剥蚀过程及其对砂岩铀成矿的约束

The formation, preservation or denudation of sandstone-hosted uranium deposits are dominated by the evolution of tectonic uplift and subsidence in the edge of the basin. The newly discovered Kamster sandstone-hosted uranium deposit is a typical example that tectonic evolution control deep burial of ore bodies in eastern Junggar basin, where the elevation between Kelameili mountain and the basin is extremely small. Furthermore, all the ore-bodies buried deeper than 600 m, obviously defined by the interlayer oxidation, unconformity and the uplift-depression structural framework. However, It still lacks chronological constraints to quantitatively study the coupling relationship between tectonic uplift-denudation and uranium mineralization. In this proposal, we will reconstruct Mesozoic-Cenozoic tectonic evolution through using the method of apatite fission track and (U-Th)/He. Based on the research of the types and morphology of uranium minerals, the metallogenic age will be accurately obtained combined with whole rock U-Pb isotope dating of uranium ores and fs-LA-ICP-MS in-situ U-Pb isotope dating of uranium minerals. Finally, we will discuss the internal connecting links between Mesozoic-Cenozoic tectonic uplift-denudation process and the spatiotemporal of uranium ore body from the angle of temporal chain. This proposal will not only establish the multi-stage tectonic evolution-uranium metallogenic model of the deposit, but also deepen the basin-orogen coupling ore-controlling theory of sandstone-hosted deposit.

构造隆升沉降演化是控制盆缘砂岩型铀矿形成、保存或剥蚀的主导因素。准噶尔盆地东部新发现的卡姆斯特铀矿床是构造演化控制矿体深埋的典型代表，具有盆山高差小，矿体埋深均大于600米，受层间氧化带、不整合面和隆坳构造格局控制明显的鲜明特征；但至今对区内构造演化-铀成矿耦合关系的精细刻画较为薄弱，其主要原因是缺乏定量的年代学约束。本申请拟采用磷灰石裂变径迹法和（U-Th）/He法，精细反演构造冷却史，并分析盆-山耦合关系；利用铀矿石全岩U-Pb同位素测年及fs-LA-ICP-MS铀矿物原位微区U-Pb同位素定年手段，精准厘定铀成矿时代；从时间链的角度详细解剖中新生代构造隆升-剥蚀过程与铀矿时空定位之间的内在联系。这不仅有助于准东卡姆斯特地区多阶段构造演化-铀成矿模式的构建，还将深化砂岩型铀矿盆-山耦合控矿理论。

准噶尔盆地东部卡姆斯特地区的中侏罗统头屯河组产有埋深普遍较大（>800m）的砂岩铀矿体，南北两侧分别为近EW向的卡拉麦里山和NW向的青格里底山。本项目通过碎屑锆石U-Pb-Hf、磷灰石低温热年代学研究，重塑了区内的源汇体系和中新生代差异的盆山耦合演化过程；恢复出北部蚀源区具有早白垩世末、晚白垩世末和古近纪末3幕式快速抬升过程，南部蚀源区仅存在早白垩世早中期快速隆升，山前沉积部位的快速隆升主要发生在晚侏罗世-早白垩世期间，后期的构造升降幅度应小于1000m。联合对铀矿石采用岩矿鉴定、原位微区分析及U-Pb同位素定年等手段，剖析了低温表生铀矿床铀的沉淀富集机理，成矿过渡带实为酸碱和氧化还原综合地球化学障；厘定出古近纪末（ca27~ca.21Ma）的一期铀成矿时间；最终构建了研究区中侏罗统头屯河组目的层形成、晚侏罗世-早白垩世早期初始成矿、白垩纪中晚期泥岩超覆掩盖和新近纪叠加改造的四阶段铀成矿模式。该研究深化完善了砂岩铀成矿机制和构造控矿模式，有助于指导区内铀矿预测和找矿。