Sedimentary characteristics of Lower Cretaceous in Wuerhe—Huanghuagou area,northwestern margin of Junggar Basin
Objectives:By combining outcrop,core,and logging,the sedimentary characteristics and sand body development characteristics of the Lower Cretaceous were finely characterized,and the exploration direction of sandstone type uranium deposits in the Wuerhe-Huanghuagou area was explored.Methods:Based on the comprehensive analysis of outcrops,drilling cores,drilling and logging in the Wuerhe-Huanghuagou area on the northwestern margin of the Junggar Basin,combined with microscopic observation,the main petrological characteristics,stratigraphic structure,sedimentary facies types and distribution characteristics of the Lower Cretaceous Tugulu Group were comprehensively analyzed.Guided by the metallogenic theory of sandstone-type uranium deposits,the types and distribution of favorable ore-forming sand bodies in the Lower Cretaceous Tugulu Group in the study area were discussed from the perspective of sedimentology.Results:① The rock types of the Lower Cretaceous Tugulu-a Subgroup in the study area are mainly feldspar lithic sandstone and lithic feldspar sandstone,while the Tugulu-b,Tugulu-c and Tugulu-d subgroups are mainly feldspar sandstone and feldspar lithic sandstone.② There are four types of sedimentary facies in the Lower Cretaceous Tugulu Group in the study area,which are alluvial fan,braided river,delta and lake,its provenance is from the northwest of Semistan Mountain.With the Delunshan as the boundary,the Wuerhe-Xiazijie area is dominated by shallow-water delta deposits with far-source weak current,while the Delunshan-Huanghuagou area is dominated by high-energy braided river deposits,its provenance should come from the northern part of the basin.③ The favorable prospecting horizon of the Lower Cretaceous is the primary gray-gray green coarse clastic formation of the Tugulu-a+Tugulu-b Subgroup.Conclusions:The branch channel of delta plain subfacies in Wuerhe-Youshashan area is an important prospecting direction.The underwater distributary channel of delta front and the thick sand body of sheet sand widely developed in the Xiazijie area have good lateral extensibility,it has the ability to form a certain scale sandstone-type uranium deposit.The Huanghuagou area developed a wide and large-scale braided river sand body in the Tugulu-a+Tugulu-b period,which is a favorable area for interlayer oxidation and phreatic oxidation.
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