松辽盆地南部无机CO2成藏机理与分布

松辽盆地南部的幔源CO₂气主要存在3种脱气方式：热底辟体脱气、岩浆房脱气和地幔热底垫体脱气。古近纪末-新近纪时期的岩浆活动和岩石圈断裂是无机CO₂气藏形成的主控因素；属于岩石圈断裂的郯庐断裂北部断裂系，当处于活动期时，诱导幔源岩浆上涌，促使无机CO₂气从幔源岩浆脱出,先期富集在下地壳底部，并沿着下地壳的网状剪切带迂回向上运移到达拆离带；当断至拆离带的低角度基底断裂处于活动期时，无机CO₂气体沿着壳源断裂上移进入地壳浅层圈闭富集成藏。气源断裂体系的展布与幔源火成岩活动脱气是无机CO₂气运聚成藏的两大主控因素。幔源CO₂气藏主要分布在长岭断陷和德惠断陷:前者主要沿着孙吴-双辽断裂带分布，后者受控于哈尔滨-四平断裂带。长岭断陷的幔源CO₂气藏埋藏较深，由于向北西的红岗阶地和东部的德惠断陷层位在变新，导致CO₂气藏埋藏深度逐渐变浅。

Distribution and Accumulation of Inorganic CO2 in Southern Songliao Basin

There are three kinds of degassing methods of mantle-derived CO₂ in southern Songliao basin:the mantle thermal diapir, crustal magma chamber, the magma chamber at lowerest crust. Magmatic activity and lithospheric fault leads to the formation of inorganic CO₂ reservoir during the end of Paleogene and Neogene. Mantle-derived magma upwelling caused by geological activity in the northern part of Tan-Lu fault belt which belongs to lithospheric fault, results in the extrusion of inorganic CO₂ from the mantle-derived. Inorganic CO₂ is accumulated at the bottom of lower crust and then raised along network shear belt circuitously to detachment zone. When the low-angle basement fault is at active period which extends to detachment zone, inorganic CO₂ gas migrated to trap and formed gas reservoies along the crustal fault. There are two primary factors controlling concentration and accumulation of the inorganic CO₂ gas reservoir, one is the spread of gas source fault system, the other is the degassing of mantle-derived igneous activity. Mantle-derived CO₂ reservoirs are mainly distributed in the Changling fault depression and the Dehui fault depression, the former is distributed along Sunwu-Shuangliao fault, the later distributed in Harbin-Siping fault. Compared with mantle-derived CO₂ reservoir in Changling fault depression, layers CO₂-bearing in Honggang terrace and Dehui fault depression are younger and shallower.