柴达木盆地中侏罗世气候干旱化与油页岩成矿耦合机制

Coupling mechanism between climate aridification and shale oil shale mineralization during the the Middle Jurassic in the Qaidam Basin

谢文泉 谭静强 贾建亮 曹涛涛 王勇

Wenquan XIE Jingqiang TAN Jianliang JIA Taotao CAO Yong WANG

气候对湖泊生物发育以及沉积环境具有重要影响，是影响油页岩成矿的重要因素。在中侏罗世晚期，柴达木盆地气候经历了一次由湿润向干旱的重大转变。在此气候转折期，盆地沉积了一套连续稳定的湖相油页岩。以该套油页岩为研究对象，利用孢粉学和地球化学等手段，探究了气候干旱化与油页岩成矿的协同演化关系。研究表明：①石门沟组页岩段油页岩沉积于不同的干湿气候背景，下部黑色块状油页岩沉积于相对湿润气候背景下的淡水湖泊，而上部纹层状油页岩形成于干旱气候背景下的咸化湖泊。②湿润气候时期繁盛的陆地植被与高的陆源通量向湖泊输入了丰富的陆源有机质和陆源碎屑，导致了其混合的有机质来源和贫氧的有机质保存环境，形成了生烃潜力好的中等品质油页岩。③干旱气候时期萎缩的陆地植被以及藻类勃发造就了藻类为主的有机质来源，而缺氧和高盐的底水环境极大地提高了有机质的保存效率，形成了具有良好生烃潜力的中等偏高品质油页岩。④此次气候干旱化引发的湖盆咸化是驱动这两种油页岩成矿模式转变的关键。该研究不仅有助于揭示气候干旱化与油页岩成矿富集的耦合机制，也可为柴达木盆地优质油页岩矿产预测提供重要依据。

Climate constitutes a crucial factor in the oil shale mineralization， given its pronounced influence on the growth of lacustrine organisms and the depositional environment.. During the late Middle Jurassic， the Qaidam Basin experienced a major climate shift from humid to arid conditions. Amid this transition， a continuously distributed sequence of lacustrine oil shales was deposited in the basin. Focusing on these oil shales， we explore the coevolutionary relationships between aridification and oil shale mineralization using methods such as palynology and geochemistry. The results indicate that the oil shales of the shale interval of the Shimengou Formation were deposited under varying humidity conditions. Specifically， the black， massive oil shales in the lower part are formed in freshwater lakes under a relatively humid climate， while the laminated oil shales in the upper part in saline lakes under arid conditions. During the humid phase， lush terrestrial vegetation and a high flux of terrigenous sediments supplied abundant terrigenous organic matter and clastics to the lakes. This created mixed organic matter sources and a dysoxic environment for organic matter preservation. As a result， medium-quality oil shales with high hydrocarbon-generating potential are created. During the arid phase， reduced terrestrial vegetation and the proliferation of algae led to the formation of algae-dominated organic matter sources. Concurrently， the anoxic， high-salinity sediment-water environment significantly enhances the preservation efficiency of organic matter. Hence， medium- to slightly high-quality oil shales with excellent hydrocarbon-generating potential occur. The salinization of lacustrine basins， induced by the aridification， is identified as the key factor in driving the transition between the two oil shale metallogenic models. This study provides insights into the coupling mechanism between aridification and oil shale mineralization and enrichment while also offering an important basis for predicting high-quality oil shales within the Qaidam Basin.

10.11743/ogg20250212