Abstract: The Lufeng 22 subsag is a magmatic diapir reformed subsag in Dongsha uplift，Pearl River Mouth basin. In order to clarify the structural deformation characteristics and evolution process of such kind of subsag, the research reconstructed the evolution process of the study area based on the structural interpretation of seismic data, the analysis of residual stratum thickness, and the balanced profile technology. it is found that, The west slope and the east sub-depression of Lufeng 22 subsag was subjected to three stages of strong magmatic diapirism, and the most active diapri is in member 4 of Wenchang Formation. The effect of magma diapirism on the depression structure is mainly shown in three aspects. First, magma diapir destroyed the initial structural style of the subsag, caused the boundary fault to bend and even break, showed a characteristics of plane zoning; Second, the strong uplift of magma lead to the strong tilting of the strata, thus the gentle slope strata was greatly uplifted and subjected to strong denudation; Third, the magma diapir produced secondary bulge, which influenced the location, scale and evolution of the sedimentary center, thus showed a very complex structural characteristics and evolution process. The west slope and eastern subsag with strong magmatic diapirism only experienced evolution stages of fault-down thrown basin and faulted-sag basin, while the western subsag, high-in-sag and east slope with weak magmatic diapirism completely developed three evolution stages of fault-down thrown basin, faulted-sag basin and sag basin. The tectonic units showed lateral zoning characteristics.

Key words: magmatic diapirism, reformed sag, sag structure, structural evolution, Pearl River Mouth basin, Lufeng 22 subsag