山东省沂水县于家洞地区铀矿地质特征及成矿条件浅析

Geological features and mineralization conditions of uranium deposits in the Yujiadong area of Yishui County,Shandong Province

山东省沂水县于家洞地区位于沂沭断裂带西侧,基底为新太古代泰山岩群及傲徕山序列花岗岩,盖层为南华系、震旦系、寒武系及新生代,断裂构造发育。区内圈定铀异常8个、伽玛总量异常7个,圈定综合异常1处。于综合异常中发现一铀矿体,矿体赋存于朱砂洞组下灰岩段黑色碳质白云岩中,长度540 m,最大斜深100 m,平均厚度0.96 m。矿石矿物主要为沥青铀矿及金属硫化物。经研究认为,朱砂洞组、佟家庄组、泰山岩群及傲徕山序列花岗岩为铀源层;成矿流体具围岩及深部混合来源特征;脉岩提供热量,使铀源层中的铀活化进入溶液;断裂是深部热液上升通道,且为成矿有利位置。铀矿床成因类型属于碳硅泥岩型中的沉积—热液叠加亚类,矿床形成经历了沉积成岩富集阶段及矿后次生热液改造富集阶段。放射性异常及含有机碳、黄铁矿、方铅矿的层位为找矿标志。

Yujiadong area in Yishui County,Shandong Province is located in the west of Yishu fault zone.The basement is Neoarchean Mount Taishan rock group and Aolaishan sequence granite.The cover is Nanhua system,Sinian system,Cambrian system and Cenozoic era.The fault structure is developed.There are 8 uranium anomalies and 7 gamma total anomalies delineated within the area,and 1 comprehensive anomaly delineated.A uranium ore body was discovered in the comprehensive anomaly,occurring in the black carbonaceous dolomite of the lower limestone section of the Zhushadong Formation,with a length of 540 m,a maximum inclined depth of 100 m,and an average thickness of 0.96 m.The ore minerals are mainly pitchblende and metal sulfides.It is believed that the Zhushadong Formation,Tongjiazhuang Formation,Mount Taishan Group and Aolaishan sequence granite are uranium source beds;The ore-forming fluid has the characteristics of surrounding rocks and deep mixed sources;Vein rocks provide heat to activate uranium in the uranium source layer into the solution;The fault is a deep hydrothermal upward channel and a favorable location for mineralization.The genetic type of uranium deposits belongs to the sedimentary hydrothermal superimposition subclass in the carbon silicon mudstone type,and the formation of the deposit has gone through the stages of sedimentary diagenesis enrichment and post ore secondary hydrothermal transformation enrichment.Radioactive anomalies and layers containing organic carbon,pyrite,and galena are prospecting indicators.