车排子凸起构造演化对铀成矿的控制作用

Structural evolution and its control on uranium mineralization in Chepaizi uplift,western Junggar basin,Xinjiang

车排子凸起是准噶尔盆地西部砂岩型铀矿“新地区、新类型、新层位”三新找矿的重点勘查区,近年来在该凸起铀矿找矿有所突破,发现多个工业孔和矿化孔。通过分析车排子凸起区域地质背景、构造演化,研究沙湾组沉积特征,结合岩心观察和基础地质综合图件的编制,探讨构造演化对目的层改造、古水系和含铀成矿流体的控制,并讨论断裂控制油气运移方向,将古氧化带二次还原的机制,明确车排子凸起构造演化对铀成矿的作用。研究认为喜山运动造成北天山的多次抬升,使车排子凸起接受沉积,形成沙湾组辫状河三角洲有利的沉积相带。喜山运动晚期北部扎伊尔山前掀斜抬升,形成南倾的单斜带,开启含铀含氧水的补给窗口。车排子凸起形成演化中发育的断裂构造和不整合面,是深部油气藏不断迁移的通道,造成了沙湾组古氧化带的二次还原,在灰绿色与灰色带砂体界面富集成矿的特点。

Chepaizi uplift is the key exploration area in western Junggar basin and some breakthrough has been made in the exploration of uranium deposits in this area,with the discovery of several economic and mineralized boreholes in recent year.By summarizing the regional geological setting and structural evolution of Chepaizi uplift,observing core samples and compiling comprehensive maps,we discussed the affect process of structural evolution on the transformation of target layer,the control of ancient water system on uraniumbearing ore-forming fluid in target layer and fracture structure control on the secondary reduction mechanism of oil and gas,and came to the following conclusions:1)the multiple uplifting of the northern Tianshan Mountains in Himalayan tectonic period,resulted in the depression and sedimentation in Chepaizi area,forming a favorable sedimentary facies belt of the Shawan formation;2)in the late Himalayan tectonic period,the northern Zaire mountain front was tilted and uplifted,forming a south-dipping monoclinic zone and some structural window for uranium-containing oxygenated water;3)the development of fault structure and unconformity in the evolution of Chepaizi bulge provided the channel for the continuously migration of deep oil and gas reservoirs,resulting in the secondary reduction of the ancient oxidation zone of Shawan formation,and the enrichment and mineralization of uranium in the interface of grey and green sand bodies.