白云凹陷浅成岩浆侵入体发育特征、成因及油气地质意义

珠江口盆地白云凹陷内发育大量早中新世(约15.5 Ma)浅成岩浆侵入体(侵入深度<3 km).目前对其形态特征、相互关系以及岩浆侵入诱发的强制褶皱等尚缺乏系统研究.通过利用高精度三维地震资料,细致刻画了侵入体的形态、岩浆运移通道以及岩床复合体内各岩床的空间关系,定量分析了强制褶皱与侵入体的几何关系.白云凹陷内岩浆侵入体...

Characteristics and Mechanisms of Shallow Igneous Intrusions and Their Implications on Hydrocarbon Geology in the Baiyun Sag

A large number of Early Miocene (ca. 15.5Ma) shallow igneous intrusions(intrusion depths < 3 000 m) have been identified in the Baiyun Sag of Pearl River Mouth Basin. Their morphological characteristics, relationships and forced folds above them have not been systematically studied. This paper detailedly describes the shapes, vertical migration pathways and spatial relationships (sill complexes) of igneous intrusions, using high-resolution 3D seismic data. Moreover, the geomorphological relationship between the forced folds and the intrusions are quantitatively analyzed. The igneous intrusions are characterized by saucer, strata-concordant, tongue orlentoid shapes. The source and flow direction of magma could be indicated from the geomorphological characteristics and spatial relationship of sills. Magma emplacement is transported from adjacent sills(lateral supply) or from dykes(vertical supply).The geomorphological characteristics of igneous intrusion are mainly controlled by the viscosity of magma, the cohesion of host rock and the emplacement depth of magma. Moreover, some igneous intrusions could trigger sediment deformations of overlying strata and form forced folds. The amplitudes of forced folds are usually less than the thickness of the igneous intrusion, because of the plastic deformation. These folds could serve as hydrocarbon traps whose sizes are mainly influenced by the scale and thickness of underlying igneous intrusion. Furthermore, normal faults that are located within the folded strata and generated by differential compaction provide pathways for vertical hydrocarbon migration.