四川若尔盖地区寒武系硅质岩成因及其对铀成矿的意义  

GENESIS OF CAMBRIAN SILICEOUS ROCKS IN ZOIGE AREA OF SICHUAN PROVINCE AND ITS SIGNIFICANCE FOR URANIUM MINERALIZATION

作　　者：郭世文 徐争启[1,2,3] 李宝新 尹明辉 王永飞[4] 黄小昆 阚磊 吴广彬 GUO Shiwen;XU Zhengqili;LI Baoxin;YIN Minghui;WANG Yongfei;HUANG Xiaokun;KAN Lei;WU Guangbin(Key Laboratory of Earth Exploration and Information Technology,Ministry of Education,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Geosciences and Nuclear Technology of Sichuan Province,Chengdu,Sichuan 610059,China;College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Sichuan Institute of Uranium Geological Survey,Chengdu,Sichuan 610061,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]地球勘探与信息技术教育部重点实验室,四川成都610059 [3]地学核技术四川省重点实验室,四川成都610059 [4]四川省核工业地调中心,四川成都610061

出　　处：《矿物岩石》2023年第4期78-89,共12页Mineralogy and Petrology

基　　金：四川省自然科学基金项目“四川若尔盖碳硅泥岩型铀矿田深部赋铀岩浆岩特征及其对深部成矿作用制约”;成都理工大学珠峰科学研究计划(项目编号:2023ZF11413);中国核工业地质局项目“康滇地轴前寒武纪地质构造演化及其对铀成矿的制约”(项目编号:AH2023-0410)。

摘　　要：硅质岩作为若尔盖铀矿区重要的含矿主岩之一,铀多于志留系硅质岩中广泛富集,而近年来于寒武系地层中也发现了铀含量较高的硅质岩,目前寒武系含铀硅质岩与区内铀成矿的关系尚不明确,研究这些寒武系含铀硅质岩可以为若尔盖铀矿田铀矿找矿提供新思路、新层位。本文在结合前人研究的基础上,利用镜下观察、地球化学分析等方法对若尔盖铀矿区寒武系硅质岩进行综合分析,探究其成因及其对铀成矿的意义。在地球化学特征上,多数样品w(SiO_(2))为81.18%~98.55%,平均值高达93.16%,其余氧化物含量除P_(2)O_(5)和CaO较高外均在1%左右或以下;硅质岩Al/(Al+Mn+Fe)为0.16~0.52,Th/U为0.03~0.10,MnO/TiO_(2)为1.2~6.0,δCe为0.530~0.718,La_(N)/Ce_(N)为1.111~2.051,这表明寒武系硅质岩具有热水沉积成因与远洋盆地的形成环境。部分铀含量较高的样品在背散射及扫面图像上观察到的主要矿物为石英和磷灰石,这与样品主量数据反应的高硅、高钙、高磷含量结果相对应,同时经研究发现样品U含量与P_(2)O_(5)、CaO含量呈正相关关系,相关系数高达0.99。这表明深部热液经构造裂隙后与硅质岩发生充填交代作用,部分热液矿物留存于硅质岩中,使硅质岩发生了磷酸盐蚀变,从而使铀得到富集。这证明了热水沉积作用为寒武系硅质岩后期铀成矿提供了良好的物质基础和储铀条件,其构造裂隙处产生的磷酸盐蚀变对铀的富集与成矿有着重要作用,对将来寒武系铀矿找矿具有一定的指示意义。Siliceous rocks,as one of the important ore bearing host rocks in the Zoige uranium mining area,uranium is more widely enriched in Silurian siliceous rocks.In recent years,siliceous rocks with higher uranium content have also been discovered in the Cambrian strata.At present,the relationship between Cambrian uranium bearing siliceous rocks and uranium mineralization in the region is not yet clear.Studying these Cambrian uranium bearing siliceous rocks can provide new ideas and horizons for uranium exploration in the Ruoergai uranium ore field.On the basis of previous studies,this paper comprehensively analyzes Cambrian siliceous rocks in Zoige uranium mining area by means of microscopic observation and geochemical analysis,and explore their genesis and relationship with uranium mineralization.In terms of geochemical characteristics,most of the samples have w(SiO_(2))contents ranging from 81.18% to 98.55%,with an average value as high as 93.16%,and the rest of the oxides are around or below 1%,except for P_(2)O_(5) and CaO,which are higher;The siliceous rock have Al/(Al+Mn+Fe)ranging from 0.16 to 0.52,Th/U ranging from 0.03 to 0.10,MnO/TiO_(2) ranging from 1.2 to 6.0,δCe ranging from 0.530 to 0.718,and La_(N)/Ce_(N) ranging from 1.111 to 2.051,This suggests that Cambrian siliciclastics have a hot-water depositional genesis with a pelagic basin formation environment.The main minerals observed in some samples with high uranium content on backscatter and scanning images are quartz and apatite,This corresponds to the results of high silicon,high calcium,and high phosphorus content reflected in the main data of the sample,At the same time,research has found a positive correlation between the U content of the sample and the P_(2)O_(5) and CaO contents,with a correlation coefficient of as high as 0.99.This indicates that deep hydrothermal fluids undergo filling and metasomatism with siliceous rocks after passing through structural fractures,and some hydrothermal minerals remain in the siliceous rocks,causing phosphate a

关 键 词：若尔盖铀矿田 寒武系硅质岩 热水沉积成因 磷酸盐蚀变 构造裂隙 铀成矿 

分 类 号：P619.14[天文地球—矿床学]