塔里木盆地北缘秋里塔格地区新构造运动及铀成矿作用阶段划分——来自不整合的约束

Unconformity Constraint on the Neotectonic Movement Stage and Uranium Mineralization in Qiulitage Area,Northern Margin of Tarim Basin

秋里塔格构造带为新构造运动的产物,构造变形复杂且强烈,然而对其构造变形时间和变形过程的认识仍存在争议,同时对第四纪以来的构造变形过程刻画较少,制约了铀成矿过程的研究。文章以秋里塔格构造带不整合为研究对象,在探讨不整合构造意义的基础上进行新构造运动过程研究;以上新统库车组下段为主要研究层位,探讨其赋矿砂体、层间氧化带等两大成矿要素特征及其与新构造运动的关系,进而进行铀成矿作用过程研究。研究表明,秋里塔格构造带不整合包括下更新统西域组下伏不整合、中更新统乌苏群下伏不整合、上更新统新疆群下伏不整合,分别显示为削截低角度不整合、超覆平行-高角度不整合、削截平行-高角度不整合。秋里塔格构造带新构造运动阶段可划分为3个阶段:平缓背斜发育阶段(N_(2)^(1)-Qp_(1))、箱式背斜发育阶段(Qp_(1)-Qp_(3))、构造突破阶段(Qp_(3)-今)。上新统库车组铀成矿过程可划分为3个阶段:同生沉积预富集阶段(N_(2)^(1)-N_(2)^(2)),时限为5.5~4.3 Ma;褶皱期层间氧化阶段(N_(2)^(2)-Qp_(2)),时限为4.3~0.12 Ma;剥蚀突破期改造-氧化阶段(Qp_(2)-今),时限为0.12 Ma~今。

Qiulitage fold-thrust belt(FTB)is the product of neotectonic movement with intensive and complex structural deformation.However,there is divergence in the understanding of its deformation time and process,and few research concerning the Quaternary structural deformation,which restricts the understanding of uranium mineralization process.In his paper,the neotectonic movement process of Qiulitage FTB was studied by analyzing the significance of unconformity.The unconformity in the lower member of Pliocene Kuqa Formation was discussed in its constrain on uranium mineralization process in sedimentary characteristics,interlayer oxidation zone characteristics.The unconformity of Qiulitage FTB included the unconformity under Xiyu Formation of Lower Pleistocene,Wusu Group of Middle Pleistocene,Xinjiang Group of Upper Pleistocene,which belongs to the cutting low-angle unconformity,overlapping parallel-high-angle unconformity and cutting parallel-high-angle unconformity.The neotectonic movement stage of Qiulitage FTB was divided into three stages:gentle anticline development stage from Early Pliocene to Early Pleistocene,box anticline development stage from Early Pleistocene to Late Pleistocene,breakthrough stage from Early Pleistocene to present.The uranium mineralization process of the lower part of Pliocene Kuqa Formation was divided into three stages:the pre-enrichment stage of syngenetic deposition from Early Pliocene to Middle Pliocene,fold interlayer oxidation stage from Middle Pliocene to Middle Pleistocene,breakthrough transformation-oxidation stage from Middle Pleistocene to present.