库车坳陷新近系砂岩型铀矿成矿条件分析

Ore-forming Conditions Analysis of Neogene Sandstone-type Uranium Deposits in Kuqa Depression

库车坳陷位于塔里木盆地北缘,区内矿产资源丰富,铀矿找矿启动时间也较早,在新近纪地层中发现了许多矿化点以及矿化异常。文章将库车坳陷新近纪地层作为研究对象,对其铀源条件、构造条件、后生氧化以及油气还原作用进行探讨,总结了新近系砂岩型铀矿成矿条件。结果表明,库车坳陷铀源条件较好,坳陷北部天山地区为蚀源区,其古元古界绿片岩、下二叠统火山岩以及海西期花岗岩等富铀岩体在风化作用、淋滤作用下,为铀矿形成提供了丰富铀源。区内构造活动强烈,抬升剥蚀部分新近纪地层的同时,其形成的断裂构造为油气运移提供了条件,补充了区域内的还原剂,有利于还原富集含氧含铀水中的铀元素。新近纪地层中含多层泥-砂-泥的互层,胶结物疏松且具有良好透水性,有利于层间氧化作用的发育,部分地层被抬升出露地表,部分剥蚀所残留的矿体则形成倒转矿体,抬升剥蚀区以北的部分地区有层间氧化发育的条件,同时由于油气的渗出,有利于矿体的叠加,找矿潜力较大。

Kuqa depression is located at the northern margin of the Tarim Basin.The area is rich in mineral resources.Uranium exploration has been conducted for quite long times,and many mineralized points and anomalies have been found in the Neogene strata.In this paper,the Neogene strata in the Kuqa depression are taken as the research object,and its uranium source conditions,structural conditions,epigenetic oxidation and oil-gas reduction were discussed,and the Neogene sandstone-type uranium deposit-forming conditions were summarized.The results show that the uranium source conditions in Kuqa depression are favorable.Uranium-rich strata such as the Lower Proterozoic greenschist,Lower Permian volcanic rock,and Hercynian granite in Tianshan adjacent to the northern part of Kuqa depression have been weathered and provided uranium source by the action of leaching for the formation of uranium mineralization.The tectonic activities in the area were intense,resulting uplifting and denuding some Neogene formations,the fault provided conditions for oil and gas migration,which is conducive to the reduction and enrichment of uranium in the oxygenic-uraniferous water.The Neogene strata contains interbedded layers of sediment and mud,and the cement is loose and has good water permeability,which is conducive to the development of interlayer oxidation.Part of the strata was lifted out of the surface,and the ore body left by part of the denudation forms an inverted ore body.Part of the area to the north of the uplift and denudation area still has the conditions for the development of interlayer oxidation.At the same time,the seepage of oil and gas provide condition for the superposition of uranium mineralization,which may bring greater prospecting potential.