| 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 |
| 点此下载全文 |
| 引用本文：聂逢君,夏菲,严兆彬,姜美珠,何剑锋,杨东光,封志兵,张成勇,张鑫,吕永华,胡鉴.2022.二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[J].地球学报,43(5):616-632. |
| DOI：10.3975/cagsb.2022.032901 |
| 摘要点击次数: 864 |
| 全文下载次数: 1050 |
|
| 基金项目:国家自然科学基金项目(编号: U2067202; 41772068; 41862010; 42172098);国家重点基础研究发展计划973计划“中国北方砂岩型铀矿流体成矿过程研究”(编号: 2015CB453002) |
|
| 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境岩体, 是一个多期次(海西—燕山期)的复式岩体。其分布面积广(>1000 km2)且有多个铀矿床围绕分布。为查明卫境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, 采取了卫境岩体出露地表、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, 卫境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。卫境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境岩体。卫境岩体与赛汉组砂岩样品Pb同位素分析结果表明, 卫境岩体原始铀含量(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两方面: 一是富含铀的卫境岩体, 二是含矿目的层砂岩(其物源来自卫境岩体)本身。磷灰石裂变径迹模拟结果揭示, 包括卫境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—53.8 Ma), 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 Loss of Weijing Granite and Sandstone-type Uranium Mineralization in Erlian Basin |
|
|
| Abstract:A series of sandstone/mud-type uranium deposits in Erlian Basin over the last 20 years have been determined to be proven deposits, making Erlian Basin an important uraniferous site in China. Weijing granite, which is located in the Bayinbaolige uplifted zone in the northwest of the Erlian Basin, is a multi-staged granite batholith (from Hercynian to Yanshanian), with a large distribution area (>1000 km2), and is surrounded by several uranium deposits. In order to study the relationship between Weijing granite and uranium mineralization, field geological investigation was conducted, in which a series of samples of Weijing granite and sandstone of the Saihan Formation were collected. Through microscopy, the Weijing samples were identified to be medium to coarse-grained biotitic, porphyritic-like granite. Petrological analysis revealed that the sandstone of Saihan Formation consisted mainly of quartz, feldspar (plagioclase and potash feldspar), and lithic fragments sourced from granites. The analytical results of the rare earth elements indicated that the material source of ore-hosting sandstone is Weijing granite. The Pb isotopic analysis demonstrated that the primitive uranium content (U0) of Weijing granite is high, averaging 15.17×10–6. However, the average uranium loss amounts to –45.47%. Similar to granite, the oxidized sandstone of Saihan Fm has obviously lost uranium, with an average of 41.42%. However, the reduced sandstone of Saihan Fm is rich in uranium at an average of 66.8%. Hence, our findings indicated that Weijing granite provides sediment sources for sandstones as well as uranium sources for uranium mineralization in Erlian basin sandstone. From apatite track analysis, we found that the Weijing granite and its adjacent area were rapidly uplifted during Late Cretaceous to Eocene (76.7–53.8 Ma). This tectonic activity was contemporaneous with the uranium mineralization in sandstone and mudstone, indicating that the uplift triggered the uranium mineralization. |
| keywords:uranium source uranium lose Pb isotope Weijing granite Erlian Basin |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|
