伊犁盆地南缘西山窑组下段骨架砂体沉积特征及与铀矿化关系

Skeleton sand body depositional characteristics of the lower member of Xishanyao Formation and their relationship to sandstone type uranium mineralization in the southern margin of Yili basin

通过对伊犁盆地南缘西山窑组下段骨架砂体平面和空间展布规律的分析,开展重点区块的沉积微相精细解剖,并探讨其与铀成矿关系。研究认为,伊犁盆地南缘西山窑组下段发育两个大型沉积朵体控制了两个大型矿集区。矿集区骨架砂体展布较厚,联通性强,具有良好的储层性质。西山窑组下段为扇三角洲沉积体系,发育平原和前缘亚相。主要的控矿微相为分流河道、水下分流河道与前缘席状砂。分流河道的矿体一般富集在粗粒砂体中,水下分流河道的矿体主要赋存在靠近泥岩特别是碳质泥岩或煤线的夹层附近,前缘席状砂的矿体主要发育在与河道过渡相连的中粗砾级砂体中。

Based on the skeleton sand body analysis in planar and spatial distribution rules of lower member of Xishanyao Formation, the key blocks of sedimentary mierofacies are shown in detail in the article, and the relationship between sedimentary microfacies and uranium mineralization is explored. It is suggested that two large sedimentary bodies of the lower member of Xishanyao Formation control two key ore-concentrated areas （Ku-Hong and Men-Zha-Wu） at the southern margin of Yili basin. Skeleton sand body in ore-concentration areas has good reservoir properties due to its large thickness and strong connectivity. Fan delta sedimentary system which includes delta plain facies and delta front facies developed in the lower member of Xishanyao Formation. The main ore-controlling microfacies are distributary channel, underwater distributary channel and front sheet sand. Ore bodies of distributary channel are enriched in the coarse sand body and ore bodies of underwater distributary channel are enriched in the nearby shale, especially carbonaceous shale and coal line in general. Ore bodies of front sheet sand are enriched in the middle-coarse sand body that connected to the channel transition.