内蒙古塔木素地区砂岩型铀矿床热活动与铀矿化之间关系

Study on hydrothermal alteration and relation with uranium mineralization of the Tamusu exogenetic uranium deposit,Inner Mongolia,China

巴音戈壁盆塔木素地区砂岩型铀矿目的层普遍固结,矿体多层但连续性差,分布不规律,后生改造特征明显。本文通过野外露头调查、岩芯观察和微观分析,发现该地区普遍发育穿层脉状石膏或方解石、热液金属硫化物矿物、矿物重结晶与新生胶结物等,出现硫酸盐-金属硫化物共生矿物和S同位素分馏,指示存在后生热流体活动。通过对矿体、矿石特征及铀矿物成因的分析,初步认为热改造对成矿控制主要发生在层间氧化作用后期,温度升高造成碳酸钙和硫酸钙沉淀、重结晶,破坏含矿溶液中碳酸铀酰络合物的平衡,造成U的沉淀,促使铀矿化进一步富集。

Tamusu sandstone type uranium deposits in Bayingobi basin,Inner Mongolia,China have obvious characteristics of epigenetic alteration,such as universal consolidation of the target layer,a multilayer with poor continuity of ore body,and irregular distribution.Through a survey of outcrops,core observation and microscopic analysis,this study found that interlayering of gypsum or calcite veins,hydrothermal sulphide minerals,recrystallization and new cements are common in this area,with sulphate-metal sulphide minerals coexisting and fractionation in their S isotope.All of above indicate epigenetic hydrothermal fluid activities.Analysis of the orebody shape,ore characteristics and the formation of uranium minerals indicate the thermal activities occurred during the late period of the interlayer oxidation.As temperature rose,CaS O4 and Ca CO3 began to precipitate and destroyed the balance of uranium complexes,causing a precipitation of uranium and prompting the enrichment of uranium mineralization.