夭折大洋盆地构造演化及充填特征探讨——以南海双峰盆地为例

夭折大洋盆地是陆缘裂谷盆地向大洋盆地演化过程中形成的一种特殊的盆地类型，其特点是洋壳基底已经形成，但很快就停止扩张而转入坳陷。以南海双峰盆地为例,探讨了夭折大洋盆地的构造演化及沉积充填特征。研究表明，这种盆地的构造演化过程包括陆缘断陷、洋壳扩张和坳陷3个阶段。断陷期为陆相或海陆过渡相沉积，目前这套地层分布于靠近盆地边缘的部位；洋壳扩张期为半深海 深海沉积，这套地层表现为由靠近盆地边缘部位向洋壳扩张中心被动超覆的特点；坳陷期为深海平原环境，远离物源区，以深海静水泥岩沉积为主。夭折大洋盆地一般都具有较高的大地热流值和地温梯度，有利于有机质的热演化生烃作用，生烃门限深度浅。尽管夭折大洋盆地属深水或超深水范畴，但由于具有良好的生、储、盖匹配关系，因而将是未来南海深水油气勘探的重要领域。

Tectonic evolution and infilling characteristics of the aborted oceanic basin:Taking Shuangfeng Basin of South China Sea as an example

The aborted oceanic basin is a special basin generated during basin evolution from epicontinental rift to ocean basin. This kind of basin is characterized by formation of the oceanic basement, which stopped expanding later and switched to depression. The tectonic evolution period of this type basin includes 3 stages of epicontinental fault subsidence, oceanic basement expanding and depression. The formation generated during the period of epicontinental fault subsidence belongs to the continental facies distributed near the margin of the basin. The formation formed during the period of oceanic basement expanding belongs to the hemipelagic or pelagic deposit, which passively overlapped upon the prior layer from the brim to expending center of the basin. The formation formed during the period of depression belongs to deep-sea plain deposit and deep-sea mudstone. The aborted oceanic basin has higher geothermal heat flow and gradient, which are favorable to the organic material thermal evolution and result in the smaller hydrocarbon-generating threshold value. The aborted oceanic basin might become significant province of deep-water hydrocarbon exploration activity, because of good matching of source rock, reservoir bed and capping formation.