新生代以来,北部湾盆地福山凹陷曾发生多期火山-岩浆活动,早期火山-岩浆活动伴随珠琼运动,有玄武岩喷发与部分浅成侵入的辉绿岩(45 Ma),中、晚期火山-岩浆活动先后伴随南海运动(30 M a)和东沙运动(10~5 Ma以及1 Ma),共发生4期玄武岩喷发;在福山凹陷油气钻探中发现了高CO₂含量的天然气藏,其CO₂稳定碳同位素、伴生稀有气体氦和氩同位素组成特征指示,福山凹陷天然气藏中的CO2主要为壳幔混合成因;壳幔混合成因CO₂气藏主要分布在花场次凸和南部斜坡的F8、F10井区,其分布范围与始新统流沙港组的岩浆岩体吻合很好,表明该期岩浆活动可能是壳幔混合成因CO₂气生成和聚集的主要原因;H _3-4井下部流沙港组三段和上部流沙港组一段CO₂聚集成藏的差异,反映了断裂活动对CO2气生成和聚集的控制作用。指出,在始新统流沙港组岩浆活动强烈的地区,由切割流沙港组三段及其以下地层的深大断裂所沟通的流沙港组三段是寻找具有经济价值纯CO₂气藏的有利勘探方向。

Natural gas pools with high content of CO₂ were discovered during the hydrocarbon exploration in Fushan depression,Beibuwan basin.The carbon isotopic composition of CO₂,Helium and Argon isotopic composition of noble gas indicate that the CO₂ is curst-mantal source.Magma activities frequently occurred since Cenozoic.In this area.The first epoch associated by Zhuqiong Motion,occurred in 45 Ma with basalt eruption and part of diabase formed by shallow intrusion.The next three epochs occurred in 30,10~5 and 1Ma associated by Nanhai and Dongsh a Motions respectively. The basalt and diabase of Liushagang formed in Eocene ma inly occur in Huachang, F8 and F10 blocks, which just coincide with the occurren ce of natural pools with high contents of CO₂. This indicates that the magma  activity occurred in Eocene is the mainly controlling factors that caused the ge neration and accumulation of CO₂ gas. The difference between the third member  and the first member of Liushagang Formation in CO₂ accumulation indicate tha t the distribution and activity of fault systems is another important factors th at controls the accumulation of CO₂. 