鄂尔多斯盆地南部三叠系油页岩沉积条件及沉积模型（英文）

Depositional conditions and modeling of Triassic Oil shale in southern Ordos Basin using geochemical records

基于主量元素、微量元素、稀土元素和生物标志化合物等测试,探讨鄂尔多斯盆地南部三叠系延长组长7油页岩的沉积环境和有机质来源。样品的甾烷特征表明油页岩具有相似的有机质来源,以藻类生物和高等植物为主。U/Th和V/Ni比值表明油页岩沉积于还原环境,铜川地区的缺氧程度较高。Sr/Ba比值表明油页岩沉积在淡水环境中,但铜川地区的盐度高于旬邑地区。Fe/Ti比值表明铜川地区经历了明显的热流体活动。Sr/Cu比值表明两个地区沉积期古气候均为温湿气候,没有明显差异。(La/Yb)NASC表明铜川地区沉积速率低于旬邑地区。Fe/Co和Th/U比值均表明铜川地区的古水体较旬邑地区深。有机质来源分析结果表明,水体中有机质既有低等藻生生物也有高等植物来源,推测这和秦岭造山运动有关。综合对比上述古沉积环境,认为相比于旬邑地区,铜川地区是鄂尔多斯盆地南部三叠系油页岩勘探的重点区域。

Based on the element geochemistry and biomarkers of the oil shale from the Chang 7 sub-unit in the southern Ordos Basin,the depositional conditions and organic source of the oil shale are discussed.Biomarkers analyses show that the oil shale has a homologous organic matter source,with a mix of plankton and advanced plants.U/Th and V/Ni ratios suggest that the redox condition is dominated by a reducing condition,and the degree of anoxia in the Tongchuan area is higher than that of the Xunyi area.Sr/Ba ratios illustrate that the oil shale is deposited in fresh water and the paleosalinity in the Tongchuan area is slightly higher.Fe/Ti ratios imply that the Tongchuan area underwent obvious hydrothermal fluid activities.Sr/Cu ratios show warm and humid paleoclimate in both areas.As assessed by(La/Yb)NASC,the deposition rate in the Tongchuan area is relatively lower.Fe/Co and Th/U ratios suggest that the paleo-water-depth in the Tongchuan area is deeper.The source rock could have the advance plants source,which must have close relationship with the Qinling orogeny.Comparing the paleoenvironment,the Tongchuan area has better depositional conditions,and is the key oil shale exploration area in the southern Ordos Basin.