渤海湾盆地黄骅坳陷上古生界暗色泥岩地球化学特征及其发育机制

上古生界暗色泥岩是渤海湾盆地黄骅坳陷主力烃源岩之一,具有重要的勘探价值。为进一步明确黄骅坳陷上古生界暗色泥岩有机质富集环境与形成机制,开展了岩石学、元素地球化学、有机地球化学分析。结果表明:渤海湾盆地黄骅坳陷上古生界暗色泥岩具有近源沉积特点,沉积时处于炎热潮湿向温暖湿润气候转换期,整体处于中高风化程度,沉积分选与再循环作用较弱,较好地保存了物源信息,且源岩为长英质岩石; 暗色泥岩从太原组沉积期到下石盒子组沉积期,有机质的富集不是由单一因素所控制的,而是氧化-还原条件、古生产力、古气候、沉积速率等多个要素共同控制与相互耦合的结果; 太原组沉积期,表层水具有较高的生产力和相对还原-硫化的水底环境,有利于有机质富集和保存; 山西组沉积期,在炎热潮湿的气候条件下表层水体也保持较高的初级生产力,同时较高的沉积速率有利于有机质的保存; 下石盒子组沉积期,温暖湿润的气候有利于有机质的富集,但较低的沉积速率导致有机质被黏土矿物以及其他无机矿物稀释,相对较难保存。

Geochemical Characteristics and Development Mechanism of Upper Paleozoic Dark Mudstone in Huanghua Depression of Bohai Bay Basin,China

The dark mudstone of Upper Paleozoic, which is one of the main source rocks in Huanghua depression of Bohai Bay Basin, has important exploration value. In order to further clarify the environment and formation mechanism of organic matter accumulation from the dark mudstone of Upper Paleozoic in Huanghua depression, the petrological, element geochemical and organic geochemical analyses were carried out. The results show that the dark mudstones of Upper Paleozoic in Huanghua depression of Bohai Bay Basin are near source deposits, which are in the transition period from hot and humid to warm and moist climate; the parent rocks are mainly felsic rocks, which are generally in medium to high weathering degree; the sedimentation sorting and recycling are weak, so the source information is well preserved; the enrichment of organic matter of the dark mudstone of Upper Paleozoic in Huanghua depression from the sedimentary period of Taiyuan Formation to the sedimentary period of Lower Shihezi Formation is not controlled by a single factor, but is the result of the joint control and mutual coupling of many factors, such as oxidation-reduction conditions, paleo-productivity, paleo-climate, and sedimentation rate; during the sedimentary period of Taiyuan Formation, the surface water has higher productivity and a relatively reductive sulfurizing underwater environment, which is conducive to the enrichment and preservation of organic matter; during the sedimentation period of Shanxi Formation, the surface water body also maintains high primary productivity under hot and humid conditions, and the higher sedimentation rate is conducive to the preservation of organic matter; during the sedimentary period of Lower Shihezi Formation, the warm and humid climate is conducive to the enrichment of organic matter, but the low deposition rate results in the dilution of organic matter by clay minerals and other inorganic minerals, which is relatively difficult to be preserved.