柴北缘团鱼山地区中侏罗统石门沟组油页岩有机地球化学特征及古湖泊条件

根据Leco（莱科）、岩石热解、GC（气相色谱）和GC-MS（气相色谱/质谱）等分析，开展了柴达木盆地北缘团鱼山地区中侏罗统石门沟组油页岩有机地球化学特征研究，探讨了油页岩的生烃潜力、有机母质来源、沉积环境及成矿差异。结果表明：石门沟组页岩段共发育3层油页岩（自下而上分别为油1、油2和油3），油页岩w（TOC）较高，平均值为8.16%，有机质类型为Ⅰ型和Ⅱ₁型，整体生烃潜力较好，且油1、油2的生烃潜力高于油3；样品中检测出丰富的正构烷烃、类异戊二烯烷烃、甾类化合物、萜类化合物和芳香烃化合物，其中，正构烷烃呈单峰式分布，主峰碳数为nC₂₃或nC₂₇，Pr/Ph值为0.20~1.08，油1、油2的C₂₇/C₂₉值、芳基类异戊二烯烃、藿烷和藿烯质量分数明显比油3高，揭示油1、油2形成于强还原条件，有机母质来源以低等水生生物为主，油3形成于弱还原-还原条件，有机母质来源具有陆源高等植物与低等水生生物双重生源特征。结合油页岩特征的差异及古湖泊条件，说明较深的湖水并不是形成优质油页岩的必要条件，藻类、细菌等提供优质有机质的生物输入以及底层水的强还原条件更有利于优质油页岩的形成。

Organic Geochemical Characteristics and Paleo-Lake Conditions of Oil Shale of Middle Jurassic Shimengou Formation in Tuanyushan Area of Northern Qaidam Basin

The authors studied the organic geochemical characteristics of the oil shale of the Middle Jurassic Shimengou Formation in the Tuanyushan area of the Northern Qaidam basin. The hydrocarbon generation potential, origin of organic matters, depositional environment and metallogenic differences were discussed based on Leco, rock pyrolysis, GC and GC-MS analysis. The results show that three layers of oil shales are developed in the shale member of the Shimengou Formation, and the content of organic carbon is high with an average of 8.16%; the organic matter contains type Ⅰ and type Ⅱ₁ kerogens, with better hydrocarbon generation potential in the first and second layers. Abundant biomarkers, including n-alkanes, isoprenoid, sterane and terpenoid were detected in the samples. The n-alkanes have the features of unimodal distributions with nC₂₃ or nC₂₇ as mean peaks, Pr/Ph from 0.20 to 1.08, C₂₇/C₂₉ sterane ratios, aryl isoprenoids, hopanes and hopenes of the oil shale in the first and second layers are significantly higher than those in the third layer, revealing that the oil shale in the first and second layers were formed under strong reduction conditions, and the organic matters are mainly lower aquatic organisms, whereas the oil shale in the third layer was formed in a weak reduction to reduction environment, and the organic matters are characterized by dual origins of lower aquatic organisms and higher plants. Combined with the differences in the characteristics of oil shale and paleo-lake conditions, it is suggested that deeper lake water is not necessary for the formation of high class oil shale; while the biological input of high class organic matter such as algae and bacteria and strong reduction conditions of bottom water are more conducive to the formation of high class oil shales.