西准噶尔额敏东缘晚泥盆世油页岩的发现及沉积环境浅析

The Discovery and Sedimentary Environment Analysis of the Late Devonian Oil Shale in Eastern Margin of Emin,West Junggar

西准噶尔额敏东缘发现晚泥盆世油页岩,分布较为广泛(走向延长大于5 km),具有含油率高(13.4%~16.6%)、单层厚度大(9.77~17.90 m)、多层分布(可采3层)、走向延伸稳定等特征。含矿岩系位于上泥盆统塔克台组下段(D_(3)tk^(1)),总体上反映出缓慢海侵的沉积层序,由粗大砾石砾岩→细小砾石砾岩(含砾砂岩)→砂岩→粉砂岩/泥页岩(油页岩)→生物碎屑灰岩组成。油页岩矿层沉积环境特殊,处于滨浅海三角洲相的沉积环境,海水相对较浅,非常适宜于大量海百合生物的繁衍生殖,油页岩层主要(或全部)由海百合茎碎片堆积而成,据其分选性及沉积方式判别,海百合茎似乎经历过搬运分选后被异地埋藏,可能为正常死亡后水流搬运聚集的结果。

The late Devonian oil shale was found in eastern margin of Emin,West Junggar,and its distribution is wide(the extension along strike is greater than 5km).It is characterized in high content of oil(13.4%-16.6%),big mono-layer thickness(9.77-17.90 m),multi-layers distributing(3 recoverable layer),and the extension along strike is relatively stable,etc.The ore-bearing rock series is located in the lower segment of the upper Devonian Taketai Formation(D_(3)tk^(1)).Taketai Formation(D_(3)tk^(1))and the series generally reflect the slow transgressive depositional sequence:coarse gravel conglomerate→small gravel conglomerate(pebbly sandstone)→sandstone→siltstone/clay shale(oil shale)→bioclastic limestone.It is very special sedimentary environment for oil shale-forming,which situates in the sedimentary environment of delta facies of littoral-neritic sea,and seawater is relatively shallow.This environment is very suitable for the reproduction of a large number of crinoids,and oil shale-bearing strata are mainly(or wholly)made up of crinoid stem fragments.On the basis of its sorted behavior and depositional mode,it seems that crinoids stems have been transported and sorted before being buried in different places,and it may be the result of carrying and gathering of water flow after the normal death of crinoids.