Semi-closed hydrous pyrolysis (HP) of whole-rock cuboids is a relatively novel technique aimed at improving the knowledge of the geochemical and petrographic alteration of petroleum source rocks. This study evaluates the comparability of observations on petroleum generation and migration in a natural maturation sequence and after HP in the same source rock. Two artificially matured samples of the Lower Jurassic (Toarcian) Posidonia Shale from the Hils Syncline (Lower Saxony Basin) were subjected to 24 h-HP experiments at 280 °C, 300 °C, 320 °C, 330 °C and 340 °C. The samples were subsequently analyzed with respect to changes in Rock-Eval pyrolysis parameters, molecular organic geochemistry, and organic petrography. After HP at 280 °C and 300 °C, organic geochemical composition and organic petrographic characterization show only minor changes. Significant geochemical and petrological changes occur at 320 °C: and phytoclasts show weakened fluorescence and volume loss, accompanied by a pronounced decrease in the Rock-Eval S2 yield of the sample, indicating conversion of kerogen to petroleum products. Optical changes are even more pronounced at 330 °C and 340 °C, when very high transformation ratios are reached, exceeding those under natural conditions. The majority of aliphatic molecular geochemical proxies for thermal maturation show systematic changes with increasing vitrinite reflectance, similar to maturation trends observed in the natural maturation sequence. However, some hopanoid thermal maturity proxies (e.g. moretane/C hopane) show unexpected inverse trends, whereas aromatic hydrocarbon ratios hardly change with increasing HP temperatures. These observations suggest that the reactions leading to changes in these parameters require considerably more time than CC bond breaking (cracking) within the kerogen structure. A large part of the organic carbon remaining in the cuboids after HP at 330 °C and 340 °C is soluble in dichloromethane and should, therefore, be classified as bitumen rather than kerogen.

中文翻译：

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下托阿统 Posidonia 页岩岩芯含水热解实验的地球化学和岩石学评价：人工和自然热成熟度系列的比较

全岩长方体半封闭含水热解（HP）是一项相对较新的技术，旨在提高对石油源岩地球化学和岩相蚀变的认识。本研究评估了同一烃源岩中自然成熟序列和高压后石油生成和运移观测结果的可比性。对来自 Hils 向斜（下萨克森盆地）的下侏罗统（Toarcian）Posidonia 页岩的两个人工成熟样品在 280 °C、300 °C、320 °C、330 °C 和 340 °C 下进行了 24 h-HP 实验。随后对样品进行了岩石评估热解参数、分子有机地球化学和有机岩相学变化的分析。在 280 °C 和 300 °C 高压后，有机地球化学成分和有机岩相表征仅显示出微小的变化。320°C 时发生显着的地球化学和岩石学变化：植物碎屑显示出荧光减弱和体积损失，同时样品的 Rock-Eval S2 产量显着下降，表明干酪根转化为石油产品。在 330 °C 和 340 °C 时，光学变化更加明显，此时转化率非常高，超过了自然条件下的转化率。大多数热成熟的脂肪族分子地球化学代理显示随着镜质体反射率的增加而发生系统变化，类似于在自然成熟序列中观察到的成熟趋势。然而，一些藿烷类热成熟度指标（例如moretane/C藿烷）表现出意想不到的反向趋势，而芳香烃比例几乎不随HP温度的升高而变化。这些观察结果表明，导致这些参数变化的反应比干酪根结构内的 CC 键断裂（裂解）需要更多的时间。在 330 °C 和 340 °C 高压处理后，长方体中剩余的大部分有机碳可溶于二氯甲烷，因此应归类为沥青而不是干酪根。