二连盆地砂岩型铀矿找矿方向探讨

文章通过岩性和铀含量分析,进一步确定了二连盆地主要找矿目的层为赛汉组上段(K1s2),重要找矿层位为赛汉组下段(K1s1),探索找矿层位为腾格尔组上段(K1t2),兼顾找矿层位为二连组(K2e)。从铀源-构造-建造-改造全要素进行了铀成矿条件整体分析,认为赛汉组上段主要沿各凹陷长轴方向发育古河谷,形成古河谷型铀矿化,受古河谷、凹陷中央低洼构造、后生蚀变控制;赛汉组下段和腾格尔组上段主要沿盆缘斜坡带发育扇三角洲沉积体系,形成潜水-层间氧化带型铀矿化,受铀源、三角洲沉积体系、后生蚀变控制;二连组主要在额仁淖尔凹陷中部发育湖泊沉积体系,形成沉积成岩型铀矿化,受铀源、二连期最大湖泛面控制;二连盆地发育大规模铀成矿作用,大致可划分为三期:99~78 Ma为沉积成岩期,67~37 Ma为后生作用主成矿期,25~8 Ma为后生叠加改造期。在此基础上,分层位按类型指明了找矿方向,总体认为二连盆地找矿工作应以乌兰察布和马尼特坳陷为重点,辐射川井、腾格尔和乌尼特三大坳陷,统筹兼顾、合理部署,具有很大找矿潜力。

Prospecting Direction of Sandstone Type Uranium Deposits in Erlian Basin

Based on the analysis of lithology and uranium content,four layers were determined as the the prospecting objects.The main target layer in Erlian Basin is the upper member of Saihan Formation(K1 s2),the important layer is the lower member of Saihan Formation(K1 s1),the concerned layer is the second segment of Tenggeer formation(K1 t2)and the considered layer is the Erlian Formation(K2 e).An overall analysis on the conditions of uranium metallogenic process was conducted from uranium source-structure evolution-sedimentary covers-transformation.It was believed that the upper member of the Saihan Formation mainly developed paleo-valleys along the long axis of each sag,forming paleo-valley-type uranium mineralization,which was controlled by the paleo-valley,the low-sag in the center of the depression and the epigenetic alteration;The lower member of the Saihan Formation and the second member of the Tengger Formation mainly developed fan delta sedimentary system along the slope of the basin margin,forming phreatic-interlayer oxidation zone type uranium mineralization,which was controlled by uranium source,delta sedimentary system and epigenetic alteration;The Erlian Formation mainly developed lacustrine sedimentary system in the central part of Errennao depression,and formed sedimentary diagenetic uranium mineralization,which was controlled by uranium source and the largest lake flooding surface in Erlian period;At the same time,it was pointed out that large-scale uranium mineralization was developed in Erlian Basin,which can be roughly divided into three stages:sedimentary diagenesis at 99~78 Ma,epigenetic main mineralization at 67~37 Ma and reformation superimposed epigenetic at 25~8 Ma.On this basis,the prospecting direction was pointed out by the type of strata.The prospecting work in Erlian basin should be focused on Ulanqab and Manit depression,radiating three major depressions,namely Chuanjing,Tengger and Unit,with overall consideration and reasonable deployment,which has great prospecting potential.