砂岩铀矿体定位条件的铀、钍含量及其放射性同位素研究

The Delineation of Ore Bodies in Sandstone Type Uranium Deposits by U and Th Concentrations and Their Radioisotopes

以512矿床为例,研究了砂岩铀矿体铀、钍含量及其放射性同位素分布规律,由此讨论铀矿体的定位条件。结果表明:①在整个层间氧化带中岩石的钍含量变化不大,表现出钍化学性质的不易被淋洗、迁移、富集的惰性特征;②铀含量从强氧化带到弱氧化带直至矿化带逐渐升高,由矿化带到还原带逐渐降低,铀含量分带性反映了氧化环境铀溶解迁移、还原环境水解沉淀的过程;③铀含量大于100μg/g是砂岩铀矿体的定位条件;④放射性同位素比值作为铀矿体定位条件因矿体所处时期不同而不同;后期矿体放射性同位素定位条件为1≤234U/238U≤2,0≤230Th/238U≤0·2,234U/230Th>1;前期铀矿体放射性同位素定位的标准为0·75≤234U/238U≤1,0·5≤230Th/238U≤1。

Exemplified by No. 512 uranium deposit, this paper discusses the delineation of ore bodies in sandstone type uranium deposits by uranium and thorium concentrations and their radioisotopes. The following conclusions have been reached: ① the contents of thorium in the whole redox zone remain stable, indicating that thorium is not chemically active in rocks, ② the contents of uranium increase gradually from the oxidation zone to the mineralization zone, but decrease gradually from the mineralization zone to the reduction zone, suggesting that uranium is transported in an oxidation environment and precipitates in a reduction environment, ③ the delineation of ore bodies in sandstone type uranium deposits can be made by uranium concentration exceeding 100 μg/g, and ④ the conditions for delineation of ore bodies in sandstone type uranium deposits by radioisotopes are different in different ore-forming periods. The conditions were 1≤ 234U/ 238U≤2, 0≤ 230Th/ 238U≤0.2,and 234U/ 230Th>1 during the last ore-forming stage, but were 0.75≤ 234U/ 238U≤1, and 0.5≤ 230Th/ 238U≤1 during the early ore-forming stage.