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台湾省南部泥火山异常发育,泥火山伴生气地质地球化学特征具有明显的沉积型壳源成因特点,并非火山幔源活动成因。这些泥火山活动所伴生的天然气组成大多数均以甲烷为主,乙烷及其重烃含量甚低。泥火山伴生气甲烷碳同位素值为-31.7‰～-35.9‰,二氧化碳碳同位素值为-10.0‰～-15.2‰。稀有气体氦、氩同位素值偏低。其中,3 He/4 He(Ra)即R/Ra值分布在0.21～1.34之间,40 Ar/36 Ar值则在304.6～330.0之间。上述地球化学特征表明,这些泥火山伴生气主要属热解有机成因的成熟烃类气,且主要是较年轻的新近纪巨厚海相沉积烃源岩的贡献。深入分析泥火山地质特征及伴生气地球化学特点,能为建立这种特殊的天然气成因成藏机制提供重要地质依据与基础研究资料,因此,具有十分重要的油气地质意义。
The abnormal development of mud volcanoes in southern Taiwan Province and the geological geochemical characteristics of mud volcano associated gas have obvious characteristics of sedimentary crustal origin and are not the cause of volcanic mantle source activity. Most of the gas components associated with these mud volcano activities are mainly methane, with very low levels of ethane and heavy hydrocarbons. Mud volcano associated gas methane carbon isotope value of -31.7 ‰ ~ -35.9 ‰, carbon isotope value of carbon isotopes -10.0 ‰ ~ -15.2 ‰. Rare gas helium, argon isotope value is low. Among them, 3 He / 4 He (Ra) that R / Ra distribution between 0.21 to 1.34, 40 Ar / 36 Ar values between 304.6 to 330.0. The above geochemical characteristics indicate that these mud volcano associated gases are mainly mature hydrocarbon gases of pyrolytic organic origin and are mainly contributed by the younger Neogene giant marine sedimentary source rocks. In-depth analysis of the geological characteristics of mud volcanoes and associated gas geochemical characteristics can provide important geological basis and basic research data for the establishment of this special natural gas accumulation mechanism. Therefore, it has very important geological meaning of oil and gas.