Magmatic intrusion impacts on source-to-sink system of rift basins: Eocene Lufeng-22 sub-sag, Pearl River Mouth Basin, South China Sea

Abstract

• Magmatic intrusion is classified based on deformation and position. • Magmatic intrusion changes the figuration of border faults and basin structure. • Intrusion-induced deformation separates original unified source-to-sink system into minor system. • Intrusion-induced deformation transforms distal source-to-sink system into proximal system. Magmatism plays an important role in the rifting of the continental margins. The intrusion effects on topography and petroleum systems within sedimentary basins have been well reported. However, the way in which the source-to-sink (S2S) system responds to intrusions is less well studied. In order to ascertain the effects of intrusions, different types of intrusion and their relationship with the S2S system are investigated. Three-dimensional seismic data calibrated with wireline logs covering Eocene Lufeng-22 sub-sag in the Northern Pearl River Mouth Basin provide support for the construction of a stratigraphic framework and for the recognition and timing of magma emplacement, and the restoration of the S2S system. Six types of magmatic intrusion are classified based on various intrusion-induced deformation in different tectonic units. The geomorphology shows that the original half-graben basin structure is complicated by intrusion-induced forced folds and secondary faults. Accompanied with deformation along border faults, weak-deformation intrusions generate low-throw secondary faults and uplift with little denudation, whereas intense intrusions result in the large-offset faults and high-amplitude denudation. The intense uplift and denudation occur both in the erosional and depositional zones of the pre-emplacement S2S system, which transform distal source system into proximal system. Moreover, forced folds and faults in the sink area separate original unified subsidence center into several minor centers. In addition, the S2S system of the syn-emplacement period exhibits complex basin structure and a reduced storage area. The analysis of intrusion-induced deformation is important in basin analysis and quantitative restoration of the S2S system.