泌阳凹陷核桃园组三段富有机质泥页岩形成环境及发育模式

通过Rock-Eval、饱和烃色谱质谱、电感耦合等离子质谱分析和X荧光光谱等测试方法，对南襄盆地泌阳凹陷核桃园组三段2油组和3油组泥页岩开展了有机质丰度、类型，生物标志化合物特征和常微量元素参数综合分析，探讨了湖相富有机质泥页岩地球化学特征及其沉积环境，并建立了富有机质泥页岩发育模式。研究结果表明，2油组沉积时期，泥页岩有机碳含量相对较低，湖盆内的有机质由水生生物和陆源有机质共同供给，有机质类型从Ⅰ型到Ⅲ型均有分布，高盐度下的水体分层和还原环境为有机质提供了良好的保存条件，但高盐环境抑制了水生生物的繁盛，一定程度上降低了湖泊生产力，此外较高的陆源碎屑的输入稀释了湖泊生产力，不利于有机质的富集；而3油组沉积时期，泥页岩有机碳含量相对较高，有机质类型以Ⅰ型和Ⅱ₁型为主，尽管水体盐度降低，分层作用减弱，但是缺氧的还原环境为有机质提供了保存条件，该环境下的湖泊高生产力是富有机质页岩形成的主控因素。

The Sedimentary Environment and Deposition Mode of Organic-Rich Mudstone from the Third Member of Hetaoyuan Formation in the Biyang Depression

According to various test methods, including Rock-Eval, GC-MS, ICP-MS, XRF and others, the abundance and type of organic matter, the major/trace elements, and the biomarker characteristics of the mudstone from the second and third beds of the third member of the Hetaoyuan Formation from the Biyang depression of the Nanxiang Basin were investigated. Based on this analysis, the geochemical characteristics and sedimentary environment of the lacustrine organic-rich mudstone have been discussed, and the deposition mode of the organic-rich mudstone has been definitively established. The results show that, during the depositional period of the second bed, the TOC values of the mudstone were relatively lower, and the organic matter of the lacustrine basin consisted of aquatic organisms and terrigenous organic matter. The kerogen types of the second-bed source rocks ranged from I to Ⅲ. The water column caused by high-salinity water and a reducing environment provided excellent preservation conditions for organic matter enrichment. However, high-salinity water conditions tend to lead to reduced primary productivity in lakes. In addition, the relatively higher terrigenous detrital matter input decreased lake productivity and was not conducive to organic matter accumulation. In contrast, during the sedimentary period of the third bed, the TOC values of the mudstone were relatively higher. The kerogen types of third-bed source rocks were mainly I and Ⅱ₁. The lacustrine salinity decreased dramatically, and the water column was not obvious, meaning that the anoxic bottom water environment was responsible for organic matter preservation. Under such circumstances, high productivity is the controlling factor for organic matter accumulation in third-bed mudstone.