诸广南棉花坑铀矿床热液蚀变伊利石矿物学和稳定同位素特征

Mineralogical and stable isotopic characteristics of hydrothermal altered illite in Mianhuakeng uranium deposit,south Zhuguang area

为了探究诸广南长江地区的黏土蚀变特征,在对棉花坑矿床开展野外工作和室内镜下观察的基础上,利用X射线粉晶衍射、氢氧同位素测试等方法对棉花坑铀矿床的热液蚀变伊利石进行了分析研究。伊利石的产出形式分为碎裂充填型、长石原位蚀变型和构造脉型三种,结晶度平均值分别为0.336、0.315和0.395,伊利石结晶受水/岩比和温度共同限制。伊利石的δ^(18)Ο值在0.4‰~9.1‰,δD在-92.4‰~-73.7‰。根据稳定同位素测试和计算,得出形成伊利石流体中水的氧同位素特征和前人研究中成矿晚期流体中水的氧同位素特征一致,同时根据计算所得伊利石形成温度在50~170℃,与成矿晚期流体温度一致;根据形成伊利石的流体中水的氢氧同位素投图可知其流体来源主要为大气降水,与成矿晚期流体来源一致,因此认为伊利石是棉花坑铀矿床成矿晚期特征蚀变矿物。

In order to explore the characteristics of clay alteration in Changjiang,Zhuguangnan area,the hydrothermal alteration illite of Mianhuakeng uranium deposit was analyzed by means of X-ray powder diffraction and hydrogen and oxygen isotope test on the basis of field survey and indoor microscopic observation.The test result found that The average crystallinity of illite was 0.336,0.315 and 0.395 respectively,the crystallization was limited by water/rock ratio and temperature.the δ^(18)Ο was 0.4‰~9.1‰,andδD was between-92.4‰and-73.7‰.According to the stable isotope test and the calculation,the oxygen isotope characteristics of water in the illite fluid are consistent with those of water in the middle and late metallogenic period studied by the predecessors,the forming temperature of illite was 50~170℃,which is consistent with the fluid temperature in the late stage of mineralization;According to the hydrogen and oxygen isotopic mapping of water in illite forming fluid,it can be seen that the source of illite is mainly meteoric water,which is consistent with that of late mineralization.Therefore,the illite was believed with the characteristic of alteration mineral in the late stage of mineralization.