陕西省华阳川U-Nb矿床矿化蚀变特征研究

Characteristics of mineralization alteration from Huayangchuan U-Nb deposit in Shaanxi province

陕西省华阳川U-Nb矿床位于华北板块南缘小秦岭地区,矿床内可见含独居石、磷灰石、贝塔石、褐帘石脉体及旁侧明显的蚀变分带现象。为探讨矿化蚀变特征,对矿脉、矿旁蚀变带岩石、近矿蚀变带岩石以及围岩的结构构造、稀土、微量元素含量进行研究,结果表明由围岩→近矿蚀变带→矿旁蚀变带,石英、斜长石含量逐步减少,微斜长石含量显著增多,微斜长石的存在使得蚀变岩石显现红色,并可作为寻找U-Nb矿体以及判别蚀变程度的标尺;细小黑云母、微斜长石沿裂隙或粒间贯入碎裂围岩中,证明存在碱性流体,同时微斜长石交代石英和斜长石说明存在碱交代作用,微斜长石、黑云母化可作为U-Nb矿化的寻找标志;稀土元素配分图、微量元素蛛网图以及差异明显的δEu、(U/Th)_N均表明矿液和围岩存在明显的差别。

HuayangchuanU-Nb deposit is located in Xiao Qinling at the southern margin of North China Block.The monazite-apatite-betafite-allanite-bearing veins occurred near the apparent mineralization alteration zone.In order to discuss the characteristics of mineralization alteration,the structure,texture,and REE,trace elements composition of ore veins,rocks in alteration zone and wall rock have been studied and reached as the following conclution;1） the content of quartz,plagioclase decrease,from country rock to altered rocks while microcline increase,which resulted in the occurrence of red,and can be used to search U-Nb ore bodies;2） fine biotite and microcline injected into cracked country rock along the fractures and intergranular space,which suggested the occurrence of alkali fluid.The microcline metasomatized quartz,which can be regarded as the occurrence of alkali alteration.Microcline and biotite can be used as symbols of finding U-Nb ore bodies.Study of REE patterns,trace elements spider diagrams,δEu,（U/Th）_N demonstrate that there is a big difference between mineralizing solution and country rock.