巢湖高骊山组页岩有机质富集与沉积环境特征

Organic Matter Enrichment and Depositional Environment Characteristics of Carboniferous Gaolishan Formation Shale in Chaohu Area of Anhui Province

目的安徽巢湖地区石炭系高骊山组发育多段杂色页岩层,组内沉积环境变化大,有利于探讨页岩有机质富集与沉积环境特征的关系。方法以巢湖石炭系高骊山组页岩为研究对象,系统开展了有机地球化学和元素地球化学特征分析。结果高骊山组页岩的TOC含量整体较低,变化范围为0.03%~0.89%,生烃潜力低,T_(max)介于519~543℃,指示页岩经历了较高的热演化阶段。页岩中Fe_(2)O_(3)含量范围为2.19%~17.90%,氧化还原敏感元素含量亦波动明显,表明沉积水体氧化/缺氧环境交替频繁。古生产力、水动力、古盐度和氧化还原条件等元素地球化学指标揭示高骊山期水体环境演化趋势为早期静水、氧化性的淡水环境转成晚期动荡、次氧化-还原状态的微咸水环境。结论高骊山组页岩整体上沉积于低古生产力、水体较动荡、主体为氧化的环境,含有较低的TOC含量,而下部I段页岩相对较高的TOC含量,反映该时期古生产力和安静的水体环境相对利于有机质的富集。

Objective To study the effect of different sedimentary environment on shale organic matter enrichment with the shales from the Carboniferous Gaolishan Formation in Chaohu area of Anhui province.Methods Based on organic geochemical and elemental geochemical analyses,the differences of organic matter enrichment and sedimentary environment characteristics of the Gaolishan shales were investigated.Results The research results showed that the Gaolishan shales had a low TOC content ranging from 0.03%to 0.89%with low generation potential,and T max values from 519 to 543℃indicated that shales had evolved into the highly mature stage.As to the elemental geochemistry,the Gaolishan shales had a Fe_(2)O_(3)content ranging from 2.19%to 17.90%,indicating that the changes of the sedimentary water depth and the alternation of oxidation/hypoxia was relatively frequent.The paleo-productivity,hydrodynamics,paleo-salinity and redox elements parameters reflected the evolution trend of the sedimentary environment during the Gaolishan Period,which changed from the quiet and oxidized fresh water environment in the lower part to the turbulent and reduced brackish water environment in the upper part.Conclusion The Gaolishan Formation is developed in the environment of low paleoproductivity,turbulent and oxidation water body,not conducive to the enrichment of organic matter.The relatively high TOC contents of Member I shales indicate that paleoproductivity and quiet water environment are the main influencing factors of organic matter enrichment in study area.