柴北缘石圈滩地区小煤沟组砂岩型铀矿化与煤层的关联性研究

Correlation Between Sandstone-type Uranium Mineralization and Coal Seams of Xiaomeigou Formation in Shiquantan Area,Northern Margin of Qaidam Basin

石圈滩地区富含油、气、煤、铀等多能源沉积矿产,但目前关于砂岩储层中铀矿体与煤层有何种关联性尚不清楚。文章通过对研究区工业铀矿孔中小煤沟组砂岩样品开展显微观察、电子探针测试和烃类分析,结合铀矿体与煤层空间展布特征,探讨铀矿化与煤层之间的关联性。结果表明,石圈滩地区铀矿体与煤层相距2~10 m,矿体规模与煤层厚度变化呈正相关性。赋矿层小煤沟组砂岩中酸解烃类主要以CH4为主,酸解烃含量在无矿化砂岩、矿化砂岩、铀矿石中依次升高,表明烃类气体参与了该区砂岩型铀成矿。煤层热演化阶段产生的烃类气体可能是铀成矿的关键因素,煤层可作为本区砂岩型铀矿勘查重要的找矿标志。

Shiquantan area is abundant in oil,gas,coal,uranium and other energy resources.However,the relation of uranium orebody in sandstone to the coal seam is not clear.Based on the microscopic observation,electron probe microanalysis and hydrocarbon analysis for ore-bearing rocks in the boreholes,the distribution of uranium orebody and coal seam was studied.The results show that the uranium orebody overlaps or nears to the coal seam in horizontal direction,and the orebody is located 2~10 m above or beneath the coal seams in vertical direction.The size of ore body is positively correlated to the coal seam thickness.The acidolysis hydrocarbon in sandstone of Xiaomeigou Formation is mainly CH4,and its content increases gradually from sterile sandstone,mineralized sandstone and uranium ore,indicating that the hydrocarbon gas was involved in sandstone-type uranium mineralization in this area.The hydrocarbon gas produced in the thermal evolution stage of the coal seam was the key factor of uranium mineralization,and the coal seam can be used as an important prospecting indicator for sandstone-type uranium deposits in this area.