粤北下庄铀矿田不同类型矿床成矿流体对比研究

Comparison of Ore-Forming Fluids in the Deposits of Different Types of the Xiazhuang Uranium Ore Field in Northern Guangdong Province

流体包裹体、同位素组成对比研究发现,下庄矿田硅质脉型和交点型铀矿成矿流体具有相同来源,为地幔流体和大气降水混合产物。铀成矿机制为成矿流体减压沸腾成矿、不同流体混合成矿。硅质脉型铀矿两种混合流体的均一温度、盐度分别为270~320℃,5.26%~7.45%;120~160℃,1.57%~4.03%。交点型铀矿两种混合流体的均一温度、盐度分别为350~370℃,6.59%~7.86%;110~250℃、0.58%~4.03%。高温、中等盐度流体来自地幔,气相成分为CO2、H2;中低温、低盐度流体为壳源流体(主要来自大气降水)。相对于交点型铀矿床,硅质脉型铀矿床的成矿深度浅,大气降水成分增多,其深部具有类似交点型铀矿成矿条件,是老矿山扩大资源量的主攻方向。

This study compares the compositions of the fluid inclusions and isotopes of different deposits in the Xiazhuang ore field. It indicates that the silic-vein type uranium deposit and the intersection type uranium deposits have the same source of the ore-forming fluid,which is a mixture of mantle fluid and meteoric water. Fluid decompression boiling and mixture of different fluids are the two types of the metallogenic mechanism. The two different fluids in silic-vein type uranium deposits have high temperature( 270 ~ 320℃),middle salinity( 5. 26% ~ 7. 45%) and low-middle temperature( 120~ 160℃),low salinity( 1. 57% ~ 4. 03%),while the intersection type uranium deposits have high temperature( 350 ~ 370℃),middle salinity( 6. 59% ~ 7. 86%) and low-middle temperature( 110 ~ 250℃),and low salinity( 0. 58% ~ 4. 03%). Compared to the high temperature-mid salinity fluid which is from mantle with gas CO2 and H2,the low-middle temperature-low salinity fluid is from the crust source( meteoric water) with light-oil. The silic-vein type uranium deposit has shallow metallogenic depth and more meteoric water,while its deep portion has the same metallogenic conditions as the intersection type deposit,which is the main target for exploration to enlarge the resource of the old mine.