凌源－宁城盆地中元古界铁岭组烃源岩生物标志化合物特征及意义

采用气相色谱、气相色谱-质谱技术, 对凌源-宁城盆地中元古界铁岭组烃源岩生物标志化合物特征进行研究, 剖析其蕴含有机质生源、沉积环境、有机质热演化程度等方面的信息及地球化学意义.铁岭组烃源岩饱和烃气相色谱以"前峰型"的单峰分布为主, 主峰碳多为nC18, 表明有机质来源以低等生物为主; Pr/Ph比值主要分布于0.16~0.73之间, 植烷优势较明显, 指示为强还原的沉积环境, 少部分为还原环境.铁岭组烃源岩具有长侧链三环萜烷丰富、伽马蜡烷含量高和C27甾烷分布占优势的分子化石组合特征, 伽马蜡烷指数(Ga/C30H)为0.10~0.31, 平均值0.19, 反映出铁岭组烃源岩形成于微咸水-半咸水环境; Ts/Tm比值为0.54~1.19, 平均值为0.88, 表明烃源岩热演化程度较高; 甾烷与藿烷的含量比值主要分布于0.24~0.59之间, 平均值0.42, 表明低等生物藻类的贡献较低, 而细菌等微生物的贡献相对较大.铁岭组烃源岩甾烷呈现C27甾烷占优势的"L"型, 表明生烃母质生源构成是低等水生生物来源的有机质特征.

THE SOURCE ROCKS OF MESOPROTEROZOIC TIELING FORMATION IN LINGYUAN-NINGCHENG BASIN: Biomarker Characteristics and Implication

Based on gas chromatography and gas chromatography-mass spectrometry, the paper studies the characteristics of biomarker compounds in the source rocks of Tieling Formation in Lingyuan-ningcheng Basin, and analyzes the organic source, sedimentary environment and thermal evolution degree of organic matter, as well as geochemical implication. The saturated hydrocarbon gas chromatography of source rocks is front-peak type unimodal distribution dominated, with the main peak carbon mostly nC18, indicating that the organic matter is mainly derived from lower organism. The Pr/Ph ratio mainly ranges from 0.16 to 0.73, with obviously more phytane, indicating a strongly reducing sedimentary environment. The source rocks of Tieling Formation are characterized by abundant long-side chain tricyclic terpane, high content of gamacerane and dominant distribution of C27 sterane, with Ga/C30H of 0.10-0.31, averagely 0.19, reflecting the source rocks were formed in slight saline water-brackish water environment. The Ts/Tm ratio of 0.54-1.19 (averagely 0.88) shows the thermal evolution degree of source rocks is relatively high. The ratio of sterane/hopane contents is mainly in the range of 0.24-0.59, averagely 0.42, reflecting the lower organism of algae contributes little to organic matter, while the microorganisms such as bacteria contribute a lot. The sterane in the source rocks are L-shape with dominant C27 sterane, indicating the hydrocarbon generating parent material is of lower aquatic biological organism origin.