内蒙古平庄盆地黑水地区上白垩统孙家湾组上段沉积相及其与铀矿化关系  

Sedimentary facies of the upper member of upper Cretaceous Sunjiawan Formation and its relation to uranium mineralization in Heishui area of Pingzhuang Basin,Inner Mongolia

作　　者：席海银 陈德兵[1] 饶明辉[2] 王黎明[1] 

机构地区：[1]核工业240研究所,辽宁沈阳110032 [2]东华理工大学,江西抚州344000

出　　处：《矿床地质》2010年第6期1079-1087,共9页Mineral Deposits

基　　金：内蒙古平庄-辽宁黑水地区1:25万铀资源区评价项目(No.200712)资助

摘　　要：内蒙古平庄盆地黑水地区上白垩统孙家湾组上段沉积相为冲积扇相,宏观上分为近端砾质辫状平原、远端砂质辫状平原及扇前洪泛平原3个亚相,进一步细分为泥石流、砾质辫状河道、砾质坝、砂质辫状河道、砂质坝、洪泛细粒、泥炭沼泽等微相。孙家湾组上段可划分为3个亚段,第一亚段为干旱-潮湿过渡气候下形成的退积型序列的旱地扇沉积;第二亚段为潮湿气候下形成的退积型序列的湿地扇沉积;第三亚段为潮湿气候下形成的进积型序列的湿地扇沉积。黑水地区的孙家湾组上段经历了早期退积型旱地扇—中期退积型湿地扇—晚期进积型湿地扇的过程。沉积相对该区铀成矿具有控制作用,铀矿化主要以不连续、局部富集的形式赋存于远端砂质辫状平原前缘的砂质辫状河砂体中,泥炭沼泽和泥质含量少的泥石流沉积中有少量存在。泥炭沼泽沉积所形成的泥岩及泥质含量高的泥石流沉积充当了局部隔水层,但由于泥炭沼泽沉积较薄,以及泥石流沉积的不均一性,致使铀矿(化)不连续、不稳定。The sediments of upper Sunjiawan Formation in Heishui area of Pingzhuan Basin are considered to be of the alluvial fan facies which can be divided roughly into three sub-facies：proximal pebbly braided plain,distal sandy braided plain and fan front flood plain;these sub-facies can be further divided into the following microfacies：debris flow,pebbly braided channel and bar,sandy braided channel and bar,flood fine-grained and peat swamp sediments.Three sub-members are recognized in upper Sunjiawan Formation,i.e.,retrogradational arid fan formed in dry-humid transitional climate,retrogradational humid fan formed in dampness,and progradational humid fan formed in dampness.Upper Sunjiawan Formation in Heishui area experienced the process from early retrogradational arid fan through medium retrogradational humid fan to late progradational humid fan.The uranium mineralization in this area was governed by sedimentary facies,and was concentrated in sand bodies of sandy braided rivers in the front of the distal sandy braided plain in the form of discontinuous and local enrichment,with less mineralization existent in peat swamp and mud-rock flow.The mudstone in peat swamp and mud-rock flow with abundant mud served as the local aquifuge,so that uranium mineralization shows discontinuous and unstable characteristics due to the thin peat swamp and inhomogeneous mud-rock flow sediments.

关 键 词：地质学 冲积扇相 砂岩型铀矿 孙家湾组上段 黑水地区 平庄盆地 内蒙古 

分 类 号：P619.14[天文地球—矿床学]