622铀矿床近矿围岩蚀变地质地球化学特征

GEOLOGLCAL AND GEOCHEMIC AL FEATURES OF WALLROCK AL TERATION OF SURROUNDING ORE MINERALIZATION INURANIUM DEPOSIT 622

本文从６２２铀矿床围岩蚀变的野外和镜下地质观察入手，结合常量元素、稀土元素地球化学综合示踪，揭示了与铀矿化密切相关的热液活动主要有两期：首先，岩浆起源的较深富钾、钠碱性热液活动及其稍晚的成矿作用形成的中等富集重稀土的碱交代－赤铁矿型铀矿化；随后，由于大气降水形成的富含氟的酸性热液的浅部地下循环水活动，导致轻、重稀土元素的进一步分馏，重稀土的高度富集以及萤石一木云母型铀矿化的叠加。并指出了广泛发育的红化、萤石化、水云母化现象、蚀变成才带内Ｐ＿２Ｏ＿５，Ｍｇｏ，ＴｉＯ＿２，ＣａＯ含量的增加，ＳｉＯ＿２，Ｎａ＿２ｏ含量的减少，ＲＥＥｔ和ＨＲＥＥ显著增高及ＬＲＥＥ／ＨＲＥＥ降低等均可作为找矿标志。

Based on the geological field and micrdscope observation of wallrock alteration of u- ranium deposit 622 and field and microscope geochemcal trace of major element and rare earth el-ement , two main periods of hydrothermal actions closely related to mineralization have been classi- fied here,The first is alkalic metasomatism and hematite type of uranium mineraliZation withmiddle enrichment of H R E E caused by alkalic hydrothermal action from the deeper magmatismand late mineralizatian. The second is acid hydrothermal action produced by near- surface circulat- ing underground water which was mainly from atmosphere. This process brought about furtherfractionation of LREE and HREE high HREE concentration , and superimposition of fluorite-damourite type of U ranium metallogenesis. It is suggested that hematitization , fluoritization anddamouritization phenomena which are widespread in the alterated metallogenic zone , the contentincrease of P_2O_5,MgO,TiO_2,CaO, REE and HREE,the decrease of SiO_2,Na_2Oand the ratio of LREE/HREE ,can be used as criteria for ore prospecting.