银额盆地中新生代断陷湖盆中原生红色沉积与后生红色改造的区分标志与分布规律OA

Numerous investigations and studies have indicated that the mineralization of sandstone-type uranium deposits is associated with the epigenetic transformation of ore-bearing sandstones.However,in the red variegated formations,the types and identification of epigenetic transformations become complex.Distinguishing between original sedimentary red sandstones and red sandstones formed by epigenetic oxidation has always been a challenge in field surveys and exploration.This paper focuses on the genetic differentiation markers of different types of red variegated geological bodies.selects the Mesozoic-Cenozoic Yingen-Ejin basin through outcrop observations,borehole core observations,and logging,combined with laboratory analysis.The results show that the formation and distribution of original red variegated layers are closely related to the depositional environment,mainly controlled by paleoclimate and paleowater depth variations.In a semi-arid to arid climate context,the color of sediments is controlled by paleowater depth,forming alluvial fans,fan deltas,and semi-deep lacustrine deposits from the basin margin inward.As the paleowater depth of deposition increases,the color of sediments gradually changes from red and red variegated to gray.Original red formations are dominated by dark red,brown,and purplish red,with a high content of matrix and developed hematitization but rarely limonitization.Original gray sandstones undergo later oxidation,marked by red with yellow,developed disseminated hematite and limonite,and clayization.The re-oxidation of original red sandstones is characterized by partial dissolution of clastic particles and weak clayization,with the main identification feature being a lighter red color.This study significantly promotes the identification of epigenetic oxidation transformations in red variegated formations and has important implications for the exploration of sandstone-type uranium deposits in these formations.