东海陆架盆地西湖凹陷平湖斜坡带南部火成岩发育，岩浆活动导致的局部地温升高对烃源岩热演化和砂岩储层次生孔隙形成具有重要影响，同时也是区域构造运动的一个重要指示，对于理解区域地质历史具有重要意义。

为明确西湖凹陷平湖斜坡带南部盖层火成岩形成期次和分布规律，综合前人研究成果和邻区数据，利用三维地震数据及相关属性，结合钻井、录井和测井资料，分析了火山岩类型、分布地层和范围；通过地层年代学、火山机构形态及其与围岩的接触关系，探讨了火成岩的形成期次。

研究结果表明：(1) 平南地区火成岩地震相可分为火山通道相、爆发相、溢流相和侵入相，其中盾状火山机构和丘状火山机构最为发育。(2) 岩浆活动可分为3期，中新世末期区域性龙井运动岩浆活动最为强烈，影响范围最广；玉泉组沉积晚期和三潭组沉积早期为局部小规模构造运动，岩浆活动较弱，影响较小。(3) 研究区发育5个与岩浆活动有关的岩性、低幅度披覆背斜和断裂复合圈闭。研究成果为后续西湖凹陷平湖斜坡带南部油气勘探开发提供参考。

Igneous rocks are well-developed in the southern Pinghu slope zone, Xihu Sag, East China Sea Shelf Basin. In this zone, the increased local geotemperature caused by magmatic activity produced significant impacts on the thermal evolution of source rocks and the formation of secondary pores in sandstone reservoirs and also serves as a significant indicator of regional tectonic movements, thus holding great significance for understanding the regional geological history.

This study aims to determine the formation stages and distribution patterns of igneous rocks as the cap rocks in the southern Pinghu slope zone. Using previous study results and the data of adjacent areas, as well as 3D seismic data and related attributes, and data from drilling and logs, this study analyzed the types, corresponding strata, and distribution ranges of volcanic rocks in the southern Pinghu slope zone. Furthermore, the formation stages of igneous rocks in the slope zone were explored based on the stratigraphic chronology, the morphologies of volcanic edifices, and the contact relationship between volcanic edifices and surrounding rocks.

The results indicate that the seismic facies of igneous rocks in the Pingnan area can be divided into volcanic vent facies, along with explosive, overflow, and intrusive facies, with mounded and shield volcanic edifices proving the most developed. The magmatic activity in the Xihu Sag can be divided into three stages. Specifically, magmatic activity during the regional Longjing Movement, occurring in the late Miocene, exhibits the highest intensity and widest influence range. Besides, local small-scale tectonic movements occurred in the late depositional stage of the Yuquan Formation and the early depositional stage of the Santan Formation, corresponding to weak magmatic activity with minimal impacts. The Pingnan area contains five lithologic, low-amplitude drape anticline/fault combination traps associated with magmatic activity. The results of this study will provide a reference for future hydrocarbon exploration and production in the southern Pinghu slope zone of the Xihu Sag.