Distribution and isomerization of C₃₁–C₃₅ homohopanes and C₂₉ steranes in oligocene saline lacustrine sediments from Qaidam Basin, Northwest China

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• 作者：Changchun Pan ; Dehua Peng ; Min Zhang ; Linping Yu ; Guoying Sheng ; Jiamo Fu
• 关键词：Radiological assessment ; Uranium ; Radium ; Polonium ; Lead ; Isotope ; Rehabilitation ; Mining ; South Alligator River
• 刊名：Organic Geochemistry
• 出版年：2008
• 期刊代码：40_01466380
• 类别：pw
• 出版时间：June 2008
• 卷：39
• 期：6
• 页码：646-657
• 文件大小：627 K

摘要

The 22S/(22S + 22R) ratios for C₃₁–C₃₅ homohopanes and the 20S/(20S + 20R) ratio for C₂₉ steranes were measured by gas chromatography–mass spectrometry (GC–MS) on six Oligocene saline lacustrine rock samples from a borehole located in the western Qaidam Basin, northwest China. These ratios vary significantly and irregularly with burial depth from 2831 m to 3054 m around the threshold of the oil generation window. In addition, 22S/(22S + 22R) ratios also vary substantially among different homologs within the same sample, generally decreasing from C₃₁ to C₃₅ homohopanes. The distribution patterns of homohopanes for the six samples are unusual, such as, C₃₁ < C₃₂ > C₃₃ > C₃₄ < C₃₅, or C₃₁ > C₃₂ > C₃₃ < C₃₄ < C₃₅, or C₃₁ < C₃₂ > C₃₃ < C₃₄ < C₃₅. All of these observations can be mainly ascribed to the release of bound hopanes and steranes from kerogen and other macromolecules.