与盐碱矿共生的油页岩形成环境及沉积演化——以桐柏吴城盆地油页岩矿床为例

The Forming Environment and Sedimentary Evolution of the Oil Shale Intergrowthing with Salt Alkali Mine——With the Oil Shale Deposit of Wucheng,Tongbai Basin as an Example

桐柏吴城盆地五里堆组油页岩为棕黑色,质细而软,呈薄片状产出,平均含油率为6.2%。其内可见大量星点状、结核状黄铁矿,并作为天然碱矿层的直接底板与天然碱、盐岩、白云岩及粉砂质泥岩构成了多个韵律旋回。研究表明:该油页岩形成于湿热气候下的山间封闭盆地;盆地构造环境稳定、周围陆源碎屑供给贫乏;沉积介质为弱还原还原、半咸水咸水的浅湖静水环境。在干湿交替但以干热为主的山间封闭盆地大背景下,五里堆组含油页岩岩系经历了“湿热作用较强→干热为主→高度干热→干热为主→湿热为主”的气候变化旋回,形成了油页岩、天然碱、盐岩、白云岩、粉砂质泥岩的不同韵律组合。

The oil shale of Wulidui Formation in the Wucheng Basin, Tongbai occurs as brownblack, thin and soft slices with an average oil yield up to 6.2%. Many sparsely disseminated and nodular pyrite can be found in the oil shales. With the oil shale occurring in the bottom, trona, salt, dolomite and silty mud rock also the oil shale make up many sedimentary rhythms. The study show that the oll shale was formed in a closed intermountainal basin under muggy climate, stable tectonic environment and sparse supply of terrestrial debrics. Standing water featured by week deoxidize-deoxidize and brackish water-saltwater is suggested for their deposition. Within a prevailing dry, but sometimes with drywet alternated, closed intermountainal basin, the oil shale of Wulidui Formation, together with trona, salt, dolomite and silty mud rock, underwent a climatic variation circle from hot humid →dry heat→ in tensively dry-heat→dry-heat→hot-humid.