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华南一些重要的中、新生代红盆中多夹暗色岩段。这些暗色岩段中的原油、油页岩与石膏、钙芒硝、岩盐共生现象比较普遍,是主要的找油和找矿的目的层。众所周知,石油的形成条件是温暖潮湿气候下具有一定面积的深水沉积、生物繁茂而又不断沉降的湖盆;在这样的湖盆中有机质才能转化成为石油。与此相反,蒸发型膏盐矿床的形成机制却是在长期干旱气候条件控制的浅湖,水体被蒸干或含膏盐类矿物浓缩到饱和度以上,膏盐类矿物经结晶而析出。油与膏盐层的形成机制既有这样大的差别,而在华南一些红盆中又共生在一起,这就引起人们的不同认识和争论。澧盐盆地是洞庭湖盆西部的组成部分,暗色岩段也出现油页岩、油气与膏盐共生的现象。本文对其成因问题提出一些初步的看法,以供探讨。
A number of important mid-Cenozoic red basins in southern China have many dark-colored rock fragments. The coexistence of crude oil, oil shale and gypsum, glauberite and rock salt in these dark-colored rocks is relatively common and is the main target for oil discovery and prospecting. It is well-known that the formation of oil is a deep-water sediment with a certain area in warm and humid climates, and a lush and continuously declining lake where organic matter can be transformed into oil. In contrast, the formation mechanism of evaporite gypsum salt deposits is a shallow lake controlled by long-term arid climatic conditions. Water bodies are evaporated to dryness or the gypsum salts are concentrated to saturation above the gypsum salts. Crystals of gypsum salts are precipitated by crystallization. Both the formation mechanism of oil and gypsum salt layer have such a big difference, and they are symbiotic in some red basins in southern China, which leads to people’s different understanding and debate. Salt basins are part of the western part of the Dongting Lake basin, and oil shale, oil and gas and gypsum salt also occur in the dark rock. This article puts forward some preliminary opinions on its causes for discussion.