柴西北缘花土沟地区新近系狮子沟组沉积特征与砂岩型铀矿关系分析

Analysis of the relationship between sedimentary characteristics and uranium deposits from the Neogene Shizigou Formation in Huatugou area,Northwest Qaidam Basin

【研究目的】柴西北缘花土沟地区发育典型砂岩型铀矿床,铀储层为七个泉组、狮子沟组及油砂山组,狮子沟组介于七个泉组与油砂山组之间,正确认识狮子沟组沉积特征与砂岩型铀矿关系成为亟待解决的地质问题。【研究方法】本文基于柴达木盆地砂岩型铀矿找矿工作,研究了狮子沟组沉积特征,分析了狮子沟组地层层序格架、成因机制、物源特征与铀矿关系。【研究结果】跃进2号地区ZK10杂砂岩颜色为棕红色,主体上为钙质泥砂岩,属碳酸盐陆源碎屑杂砂岩,CIA=37.79~69.14,ICV=0.84~2.13,Σ=1.39~2.14,K_(2)O/Na_(2)O=0.90~1.18(平均为1.06),说明杂砂岩中钾长石或钾矿物较多。224~240 m处测得的GR为0~30 API,RT为-5~45Ω·m,测井相为箱型,曲线的幅度较大。K_(2)O/Al_(2)O_(3)=0.22~0.27,Ni/Co=0.34~0.53。【结论】狮子沟组在该地区为河流相沉积环境,其上段源岩物质为干燥寒冷的古气候环境下的首次沉积,含有黏土物质较少。杂砂岩原岩形成于大陆岛弧环境,其源岩为浅源的碱性长石数量较少的长英质岩石,该组沉积环境非常有利于铀矿形成。

This paper is the result of mineral exploration engineering.[Objective]Typical sandstone type uranium deposits are developed in Huatugou area,Northwest Qaidam Basin.The uranium reservoirs are Qigequan Formation,Shizigou Formation and Youshashan Formation,while Shizigou Formation is somewhere in between Qigequan Formation and Youshashan Formation.It is an urgent geological problem to correctly understand the relationship between sedimentary characteristics of Shizigou Formation and sandstone-type uranium deposits.[Methods]In this paper,the sedimentary characteristics of Shizigou Formation are studied based on the sandstone-type uranium deposit prospecting work in the Qaidam Basin,and we analyzed the stratigraphic sequence frame,cause mechanism,provenance characteristics and their relationship with uranium ore from Shizigou Formation.[Results]The colour of greywacke collected from ZK10 in Yuejin 2 area is brownish red,while the main body is calcareous argillaceous sandstone,which belongs to carbonate terrigenous clastic greywacke.Specific value of CIA=37.79-69.14,ICV=0.84-2.13,Σ=1.39-2.14,K_(2)O/Na_(2)O=0.90-1.18(the average is 1.06),which indicated that there are relatively much more potassium feldspar or potassium minerals in the greywacke.The measuring result from a depth of 224 to 240 meter is GR=0-30 API,RT=-5-45Ω·m.The logging facies is box type,and the amplitude of the curve is large.The measuring result of greywacke is K_(2)O/Al_(2)O_(3)=0.22-0.27,Ni/Co=0.34-0.53.[Conclusions]The sediment environment of Shizigou Formation in Yuejin 2 area belongs to fluvial facies.The source rocks of the upper Shizigou Formation contain less clay material,and were deposited for the first time under the dry and cold paleoclimate environment.The source rock of greywacke in the Shizigou Formation were formed in the continental island arc environment,which the sedimentary source rock of the greywacke is the alkali feldspar with a small amount of felsic rocks.The sedimentary environment of the formation is very conducive for the formation of uranium deposits.