伊犁盆地地下水水文地球化学特征与铀成矿条件分析

Hydrogeochemistry Characteristics and Uranium Metallogenic Conditions of the Groundwater in Yili Basin

砂岩型铀矿的形成是水-岩相互作用的结果,研究含铀储层地下水化学特征有助于分析铀成矿条件。通过系统采集伊犁盆地不同类型含水层的地下水样品,开展伊犁盆地地下水中水文地球化学组分及铀含量测试,分析了地下水水文地球化学特征与铀成矿条件。结果表明:伊犁盆地地下水补给区的浅循环地下水均呈现为低TDS、低—中等铀含量的HCO_3-Ca型水;而地下水径流区的地下水则往往呈现出中等TDS、中等—高铀含量的HCO_3·SO_4-Na型或SO_4·Cl-Ca·Na型水,表现为岩石中的铀及其他物质成分已被充分氧化和溶滤进入地下水,即发生着"铀随水去"的氧化溶解过程;地下水径流-排泄区的地下水呈现出高TDS、低—中等铀含量的SO_4·Cl-Ca·Na型或Cl·SO_4-Na·Ca型水,地下水中铀含量沿程降低,表明地下水径流已进入还原带,地下水中的铀已被还原吸附到铀储层的固体颗粒表面,即发生着"水去铀留"的还原富集过程。

The formation of sandstone-type uranium deposits is the result of water-rock interaction.Studying the chemical characteristics of groundwater in uranium-bearing reservoirs is helpful to analyze the uranium metallogenic conditions.This paper collects of the groundwater samples of different types of aquifers in Yili Basin,tests chemical composition and uranium content in groundwater,and analyzes the groundwater hydrogeochemistry characteristics and uranium metallogenic conditions.The results show that the shallow circulating groundwater in the recharge area is HCO 3-Ca type water with low salinity and low or medium uranium content.Well water collected in groundwater runoff area is HCO 3·SO 4-Na or SO 4·Cl-Ca·Na type water with medium salinity and medium-high uranium content,indicating that the uranium and other components in the rock have been fully oxidized and leached into the groundwater,as the uranium goes with water,oxidative dissolution process occurs.As the groundwater continues to migrate deeper into the groundwater discharge area,groundwater is SO 4·Cl-Na·Ca or Cl·SO 4-Na·Ca type water with high salinity but low-medium uranium content,where total dissolved minerals increase along the flow path but uranium content decrease.It indicates that the uranium in the water has been reduced and adsorbed to the surface of the solid particles of the uranium reservoir in the reduction zone,when the reduction and precipitation process that water goes but uranium retention occurs.