The Relationship Of Inorganic CO₂ Gas Reservoirs And Igneous Rocks

There are seven inorganic CO₂ gas reservoirs discovered in Jiyang Depression, and the contents of CO₂ is always more 60% in the inorganic CO₂ gas reservoirs. The inorganic CO₂ gas reservoir, as a kind of abnormal gas reservoir, has many features in the genetic type, migration, rule of accumulation and the factors of influence. So many questions have been existing, especially the affinities showed between the inorganic CO₂ gas reservoirs and Cenozoic igneous rocks. In spit of many scholars focused on it more than more, but the research of the affinities of them was rarely reported officially recently, and shorter of exploration and study. Therefore this paper aims at the disclosing the relationship essentially based on the study objects of inorganic CO₂ gas reservoirs and the interrelated basalts in Jiyang Depression. On the base of field geological investigation and collection of predecessor's studying by the numbers, this paper tested and analyzed the major elements, trace elements and isotopic ratios for the associated basalts of the CO₂ gas reservoirs in Jiyang Depression. And through multidisciplinary analyzing the associated data about CO₂ and the result of deep geophysical exploration and regional tectonic geology by predecessors, this thesis studied the characters of gas reservoir and geochemical characters of basalts in Jiyang Depression, and more explored the relation between the CO₂ gas reservoir and basalts. The research shows that in the Jiyang Depression, CO₂ gas reservoirs all belong to the inorganic genetic type, and the gas-source comes mostly from mental and is related to metal-sourced magmatic activities. Cenozoic basalts probably derived from convection asthenosphere depleted mantle, but Eocene magma source was subjected slightly to contamination by EMâ… enriched mantle, Oligocene magma source was mostly asthenosphere depleted mantle, and Miocene magma source had lithosphere mantle contamination in some degrees. The characters of CO₂ gas reservoirs and associated basalts show that the both are close in the space-time, formation and accumulation. The thesis draws conclusions: â‘ Most formation of CO₂ gas reservoir were later than igneous rocks showing phenomenon of lag. â‘¡Cenozoic basalts and CO₂ gas have same source, and basalts are carrier or gas-source rocks of CO₂. â‘¢The migration mechanism is divided into four phases namely lifting of mantle magma enriched CO₂ gas , mantle degassing primarily, second liberating gas and accumulating of CO₂ in available trap structure. â‘£The formation of inorganic CO₂ reservoir included mainly some contacted processes,which include Pacific tectonic plate subduction and withdraw, asthenosphere depleted mantle convection upwelling, mantle-source basalts magma forming, lithosphere extensional attenuating, extension fracture systems forming, CO₂ migrating and accumulating.