二连盆地西部隆起区卫境岩体铀丢失与盆内铀矿成矿关系探讨*
投稿时间:2021-11-16  修订日期:2022-03-08  点此下载全文
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聂逢君 东华理工大学核资源与环境国家重点实验室 330013
夏菲 东华理工大学核资源与环境国家重点实验室 
严兆彬 东华理工大学核资源与环境国家重点实验室 
姜美珠 东华理工大学核资源与环境国家重点实验室 
何剑锋 东华理工大学核资源与环境国家重点实验室 
杨东光 东华理工大学核资源与环境国家重点实验室
核工业大队 
封志兵 东华理工大学核资源与环境国家重点实验室 
张成勇 东华理工大学核资源与环境国家重点实验室 
张鑫 东华理工大学核资源与环境国家重点实验室 
吕永华 核工业208大队 
胡鉴 核工业208大队 
基金项目:国家自然科学基金项目(重点项目,面上项目):U2067202;41772068;41862010;42172098
中文摘要:二连盆地在近20年已探明多个砂岩、泥岩型铀矿床,是我国重要的产铀盆地。位于二连盆地边缘西北部隆起区的卫镜岩体,是一个多期次(海西-燕山期)的复式岩体。其分布面积广(>1000km2)且有多个铀矿床围绕分布。为查明卫镜岩体与盆地内铀成矿之间的关系,开展了详细地野外地质调查,采取了卫镜岩体出露地表、钻孔中揭露的岩石以及盆地内含矿目的层砂岩样品。露头观察和镜下鉴定结果表明,卫镜岩体主要为中粗粒黑云母似斑状花岗岩。其在地表已被强烈风化、剥蚀乃至夷平。含矿目的层砂岩中主要碎屑颗粒为石英、长石(斜长石与钾长石),部分为花岗岩岩屑,它们主要来自花岗岩岩体。卫镜卫镜岩体和哈达图铀矿床目的层(赛汉组)砂岩样品稀土元素及其参数对比表明,含矿层砂岩物质成分来自于卫镜岩体。卫镜岩体与赛汉组砂岩样品Pb同位素分析结果表明,卫镜岩体原始铀含量(U0)较高,平均达15.17×10-6,丢失的铀含量平均达到-45.47%。赛汉组氧化带砂岩中铀明显丢失,平均铀的丢失率为-41.42%,而还原带砂岩中铀多为获得,平均铀获得率达66.80%。由此可知,目的层铀矿化中铀的来源有2方面:一是富含铀的卫镜卫镜岩体,二是物源来自卫镜卫镜岩体的含矿目的层砂岩(其物源来自卫镜岩体)本身。磷灰石裂变径迹模拟结果揭示,包括卫镜卫镜岩体在内的二连盆地西部隆起区快速抬升始于晚白垩世,止于始新世(76.7~53.8Ma),这一结果与盆地中砂岩、泥岩型铀矿化时代基本一致。因此,抬升作用诱发了二连盆地外生铀矿床的形成。
中文关键词:铀源  铀丢失  Pb同位素  卫境岩体  二连盆地
 
Study on Uranium Lose of Weijing Granite and Sandstone-type Uranium Mineralization in Erlian Basin. Earth Science Frontiers
Abstract:A series of sandstone/mud-type uranium deposits have been proven within the Erlian Basin in the last 20 years, thus the basin is an important uraniferous basin in China. Weijing granite, located in the Bayinbaolige uplifted zone, the northwest of the Erlian Basin, is a multi-staged granite (from Hercynian to Yanshanian). Its distribution area is large (>1000km2), and surrounded by several uranium deposits. In order to study the relationship between the Weijing granite and uranium mineralization, field geological investigation has been conducted, and a series of samples of Weijing granite and sandstone of Saihan Formation have been taken. By means of microscopy, Weijing granite is medium to coarse-grained biotitic porphyritic-like granite. Petrologically, sandstone of Saihan Fm consists mainly of quartz, feldspar ( plagioclase and potash feldspar), and lithic fragments sourced from ganites. The analytic results of REE indicate that the material sources of ore-hosting sandstone are sourced also from Weijing granite. Pb isotopic analysis demonstrates that the primitive uranium content (U0) of Weijing granite is high, ave. 15.17×10-6, whereas, the average lost uranium amounts to -45.47%. Like the granite, the oxidized sandstone of Saihan Fm is lost obviously in uranium, ave. 41.42%. But the reduced sandstone of Saihan Fm is rich in uranium, ave. 66.8%. Hence, all studies show that Weijing granite provides both sediment sources for sandstones and uranium sources for uranium mineralization in sandstone in Erlian basin. From apatite track analysis, the Weijing granite and its adjacent area were rapidly uplifted during Late Cretaceous to Eocene (76.7 ~ 53.8Ma). This tectonic activity is accordant temporally to the uranium mineralization in sandstone and mudstone. Conclusively, the uplift trigged the uranium mineralization.
keywords:uranium source  uranium lose  Pb isotope  Weijing granite  Erlian Basin
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