鄂尔多斯盆地西缘中新生代构造演化与铀成矿作用

受周边板块离散、汇聚的影响,中-新生代鄂尔多斯盆地及其西缘构造应力场发生了多次转变,造成不同时期盆地类型与沉积充填、构造变形特征的差异。据此,将盆地西缘中-新生代构造演化划分为7个阶段。其中,晚三叠世强烈的挤压,使盆地西侧阿拉善地块上富铀岩石剥出地表,并为盆地提供铀源;早-中侏罗世弱挤压构造背景下辫状河发育,形成了有利的含矿建造;晚侏罗世的强烈挤压,使中-下侏罗统发生构造变形并遭受地下水的渗入改造,但构造变形太强烈,影响了铀成矿的潜力;晚白垩世-渐新世早期盆地西缘整体隆升,使区内目标层长期遭受地下水渗入改造,形成了主要的铀矿化;渐新世之后,银川断陷隔断了盆地与蚀源区的联系,铀成矿作用基本停止。

Meso-Neozoic structural evolution in the western margin of Ordos basin with respect to uranium ore formation

Under the influence of divergence and convergence of Pacific plate,Indian plate,etc.,the structural stress field underwent several changes in the western margin of Ordos basin in the Meso-Neozoic,and gave rise to differences in basin types,sedimentary filling and structural deformation in different stages. Based on these differences,the Meso-Neozoic structural evolution is divided into seven stages in the western margin of Ordos basin. Among these stages,the strong squeezing in the late Triassic made uranium-rich rocks exposed in Alxa block to the west of the basin,which provided uranium source for the basin; the braided river was well developed under the structural setting of weak squeezing in the early and middle Jurassic and favorable uranium-bearing formations were formed; the strong extrusion in the late Jurassic made the middle and lower Jurassic altered due to the infiltration of underground water. However,the strong structural deformation had an adverse effect on the uranium metallogenic prospect; the uplift in the western margin of the basin from the late Cretaceous to early Oligocene made the target strata suffer from a long-term alteration due to the infiltration of underground water and the major uranium mineralization was formed; Since the Oligocene Yinchuan faulted basin has cut off the relation between the basin and the provenance area and the uranium mineralization was halted basically.