南岭中段黄沙铀矿区黑云母与绿泥石的矿物化学特征及其对成岩成矿的约束  

Mineral Chemistry of Biotites and Chlorites from Huangsha Uranium Mining Area in the Middle Nangling Range: Constraints on Petrogenesis and Uranium Mineralization

作　　者：钟福军 潘家永[1] 许幼 祁家明 舒田田 牟平[1] 吴德海[1] 

机构地区：[1]东华理工大学核资源与环境国家重点实验室培养基地,南昌330013 [2]核工业290研究所,韶关512026

出　　处：《高校地质学报》2017年第4期575-590,共16页Geological Journal of China Universities

基　　金：国家自然基金项目(U1403292);中国地质调查局项目(12120115035601);省部共建核资源与环境国家重点实验室培育基地自主基金项目(Z1608);江西省研究生创新项目(YC2016-B074)联合资助

摘　　要：黄沙铀矿区位于南岭成矿带中段龙源坝岩体中南部,区内成矿地质条件优越,铀资源找矿潜力大。本文在矿物原位分析技术(EPMA与LA-ICP-MS)的基础上,讨论了黑云母和绿泥石的矿物化学特征对成岩成矿作用过程的约束。结果显示,矿区印支期中粗粒黑云母花岗岩中黑云母为铁质黑云母,指示岩浆演化程度较高,氧逸度和结晶温度较高。黑云母是花岗质熔体中Rb、Ba、Nb、Ta、Sc、V、Co、Ni、Cr元素的主要载体,副矿物(独居石、锆石、磷钇矿等)是Th、Sr、Hf、Zr、Y的主要载体,U主要赋存于晶质铀矿和含铀副矿物中。绿泥石分黑云母假象绿泥石和脉状绿泥石两类,形成于中温、相对酸性、相对氧化性的环境下。黑云母假象绿泥石形成于成矿前期的面状蚀变,以相对富铁为特征,经历了溶解、沉淀过程,伴随晶质铀矿和含铀副矿物中铀的活化与再分配。脉状绿泥石形成于成矿期的热液蚀变,以相对富镁为特征,经历了溶解、迁移与沉淀过程,富U流体流经还原性介质时,流体中的U^(6+)被还原沉淀形成沥青铀矿。The Huangsha uranium mining area, located in the central-south Longyuanba complex of the middle Nanling Range, South China, shows a favorable mineralization condition and prospecting potential for uranium mineral resource. In this paper, the mineral chemistry of biotites and chlorites occurred in the mining area has been analyzed by using EPMA and LA-ICP-MS techniques, and hereby the implications to petrogenesis and mineralization have been discussed. The results have shown that the biotites from Indosinian medium-to coarse-grained biotite granite belong to siderophyllite, and the magma were formed under an environment with high oxygen fugacity and crystallization temperature, and have experienced high degrees of differentiation. Biotite was the important carrier of Rb,Ba, Nb, Ta, Sc, V, Co, Ni, Cr, and accessory minerals(such as monazite, zircon and apatite) were the primary carriers of Th, Sr, Hf, Zr and Y in the granitic melts. U mainly hosted in uraninite and U-bearing accessory minerals. According to the occurrence and mineral chemical characteristics, chlorite in this mining district can be distinguished into two types, i. e., chlorite with biotite pseudomorph and vein form chlorite. These chlorites were formed under an environment with medium temperature, and in relatively acidic and oxidizing conditions. Chlorites with biotite pseudomorph are relatively rich in Fe, and were generated by planar alteration. The formation of these chlorites has experienced dissolution and precipitate processes during the pre-mineralization stage which led U released from uraninite and accessory minerals. However, the vein form chlorites are relatively rich in Mg, and were formed during mineralization stage through a process including dissolution, migration and precipitation. The U^(6+) has been reduced and precipitated as pitchblende when the U-rich fluids flow through a reduced medium.

关 键 词：铀成矿 黑云母 绿泥石 成岩作用 成矿作用 

分 类 号：P58[天文地球—岩石学] P619[天文地球—地质学]