Abstract Studies of occluded oxygen-bearing compounds inside kerogen are scarce, although such studies are important in understanding early-stage transformation of organic matter. A relatively low-maturity kerogen from the late Permian mudstone of the Lucaogou Formation of the Santanghu Basin, northwestern China, was successively extracted with n -hexane, acetone and dichloromethane to release the adsorbed components, and the extracted kerogen was treated with a mild oxidation reagent H 2 O 2 to release the occluded components. Gas chromatography–mass spectrometry analysis of the adsorbed and occluded components revealed a suite of oxygen-bearing compounds, including n -alkan-2-ones, n -aldehydes and fatty acid methyl esters. The n -alkan-2-ones were mainly detected in the adsorbed fraction and n -aldehydes in the occluded component. Comparison of the long-chain oxygen-bearing compound distributions and their individual stable carbon isotope characteristics both suggest that the oxygen-bearing compounds released by H 2 O 2 treatment were occluded in the kerogen. The shorter-chain (C 15 to C 19 ) occluded n -aldehydes reflected similar isotopic distribution trends to the adsorbed n -alkan-2-ones, and the δ 13 C values of the mid-length (C 21 to C 25 ) occluded n -aldehydes were much closer to the adsorbed n -alkanes. Bacterially mediated methylation and decarbonylation of the n -aldehydes during kerogen formation may be important source(s) of n -alkan-2-ones and n -alkanes, respectively. The mid-chain ketones mainly originated from hydrothermal alteration of n -alkanes after kerogen formation. Uplift of the Lucaogou Formation in the Yuejingou section allowed surface-enhanced aerobic reactions.

中文翻译：

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三塘湖盆地芦草沟组干酪根中多系长链含氧化合物的测定及地球化学意义

摘要 对干酪根内的吸藏含氧化合物的研究很少，尽管这些研究对于理解有机质的早期转化很重要。以三塘湖盆地芦草沟组晚二叠世泥岩中成熟度较低的干酪根为研究对象，依次用正己烷、丙酮、二氯甲烷提取干酪根，释放吸附组分，对提取的干酪根进行轻度氧化处理试剂 H 2 O 2 以释放封闭的组分。吸附和吸留组分的气相色谱-质谱分析揭示了一系列含氧化合物，包括 n-alkan-2-ones、n-醛和脂肪酸甲酯。n-alkan-2-ones主要在吸附组分中检测到，n-醛类在吸留组分中检测到。长链含氧化合物分布及其各自稳定碳同位素特征的比较表明，H 2 O 2 处理释放的含氧化合物被夹杂在干酪根中。较短链（C 15 至 C 19 ）夹杂的正醛反映了与吸附的正构烷烃 2-酮相似的同位素分布趋势，并且中段（C 21 至 C 25 ）夹杂的 δ 13 C 值正醛更接近吸附的正烷烃。在干酪根形成过程中，细菌介导的正醛甲基化和脱羰可能分别是正构烷烃 2-酮和正构烷烃的重要来源。中链酮主要来源于干酪根形成后正构烷烃的热液蚀变。