丹凤地区花岗伟晶岩型铀矿床铀成矿作用机理研究

Guangshigou and Chenjiazhuang uranium deposit which located in Danfeng areas-the most important granite-pegmatite-type uranium deposit production area in China have been selected in this study.Granite, granitic and alaskitic stock，pegmatite as well as the regional metamorphic rocks be regarded as the uranium-deposite-product system.Based on detailed field investigation,in suit analysis technology such as EPMA and LA-ICP-MS methods be employed to study the characteristics of mineral in ore-bearing and non-ore-bearing pegmatite, for the purpose to reveal the physical chemical conditions and its influence factors.The evolution relationship and the characteristic of the enrichment of uranium in different stage of metamophic, granite, stock and pegmatite will be revealed by means of petro-geochemical,isotopic tracing, dating combining with fission track and leaching experiment. Than it will be used to determining the condition of the activation and migration of uranium to help revealing the enrichment mechanism of pegmatite-type uranium deposit. This study have great significance in deeping the metallogenic theory and guiding the prospecting of pegmatite-type uranium deposit.

本项目选择我国伟晶岩型铀矿最重要的产区-丹凤地区的光石沟铀矿床和陈家庄铀矿床，将区域变质岩，特别是花岗岩、花岗质和白岗质岩株、伟晶岩看作为一个产铀伟晶岩体系，通过详细的野外地质调查，采集代表性的岩、矿石样品，采用电子探针和LA-ICP-MS等原位微量分析技术，开展含矿和非含矿伟晶岩的精细矿物学研究，探讨和揭示铀在伟晶岩型铀矿床中富集的物理化学条件和影响因素；通过产铀伟晶岩体系的岩石地球化学、同位素示踪和年代学研究，结合裂变径迹和溶浸实验研究，揭示变质岩、花岗岩、小岩株与伟晶岩的演化关系及不同阶段铀元素的富集特征，确定产铀伟晶岩体系中铀的活化、迁移条件，探讨伟晶岩型铀矿床的富集和形成机制，本研究对深化伟晶岩型铀矿成矿理论和指导伟晶岩型铀矿的找矿工作均具有重要的理论和实际意义。

本项目通过详细的野外地质调查和采集代表性的岩、矿石样品，对我国最重要的伟晶岩型铀矿集区-丹凤地区的光石沟铀矿床和陈家庄铀矿床采用径迹蚀刻、显微观察、扫描电镜、电子探针、LA-ICP-MS等试验和微区测试技术和方法，开展了含矿和非含矿伟晶岩的精细矿物学和成岩成矿条件研究，探讨了该区伟晶岩型铀矿成矿作用的时代、成岩、成矿物理化学条件等，获得的主要成果和认识是：1）查明了该矿集区铀的赋存和产出状态、矿物形成世代及富集形式；2）确定了该区铀成矿作用主要有416.9±10Ma和407. 6±8Ma~401±10Ma 2个主成矿期，分别对应于该区同期的花岗伟晶岩成岩作用； 3）确定了该区铀成矿作用机制是铀主要以晶质铀矿的形式从花岗伟晶岩岩浆中直接结晶析出成矿，花岗伟晶成岩作用就是铀成矿作用；4）晶质铀矿周围绿泥石、黄铁矿等蚀变晕圈的存在表明：丹凤地区铀矿床（特别是陈家庄矿床）形成后经历了热流体的改造作用，初步的研究成果（绿泥石温度计）表明指示改造作用流体的性质为中低温、低氧逸度和高硫逸度。但由于蚀变晕圈的范围较小，本项目研究成果中由电子探针测试获得的成岩成矿物理化学条件特别是改造流体的性质尚需要今后开展相关微区结构等研究工作来进一步考证。