南海北部边缘盆地不同类型非生物成因CO_2成因成藏机制及控制因素

南海北部边缘盆地非生物成因CO2资源丰富,依据通常的成因判识与划分参数（δ13 CCO2和3 He/4 He）,结合运聚成藏的具体地质条件及控制因素,可将CO2成因成藏机制明确划分为泥底辟热流体控制的壳源型及壳幔混合型CO2成因成藏机制和火山幔源活动及深大断裂输导控制的火山幔源型CO2成因成藏机制2种类型。前者,即壳源型及壳幔混合型成因CO2资源丰富储量规模大,这种成因成藏机制形成的CO2运聚成藏规律复杂,主要富集于西北部走滑伸展型边缘的莺歌海盆地中央泥底辟构造带浅层,具有平面上分区、分块、纵向上分层、分带多期运聚成藏的特点,且主要受控于泥底辟热流体上侵活动与巨厚海相含钙砂泥岩的物理化学综合作用;后者即火山幔源型成因CO2在该区资源及储量规模较小,多分布在处于北部裂陷带的琼东南盆地东部Ⅱ断裂带周缘和珠江口盆地北部深大断裂发育区,且主要受控于火山幔源岩浆脱排气之CO2气源供给与深大断裂导气输送作用的有效配置。

Accumulated Mechanisms for Different Genetic Types of Non-biological CO_2 and Controlling Factors in North Marginal Basins,South China Sea

There is plenty of non-biological CO2 in the north marginal basins of South China Sea.Based on patterns of gas origins and classified parameters(i.e.δ13CCO2,3He/4He) as well as specific geological conditions of gas migration and accumulation,two types of CO2 sources are classified into crustal-type CO2 or mixing of crust-mantle mixed type CO2 controlled by both muddy diapiric thermal fluid,and mantle-type CO2 acted by mantle-derived volcanic activity and deep fault.The crustal-type and mixing of crust-mantle type CO2 is widely distributed.After the complex processes of migration and accumulation,this type of CO2 is mainly clustered in the shallow layer of central muddy diapirs zone in the strike-slip extensional brim of northwest Yingge Sea basin,which is characterized as partition block in plane and multi-layer and zone in vertical.So,the crustal-type and mixing of crust-mantle type CO2 accumulation is controlled by muddy diapir intrusion activity and physical-chemical combined action about thick marine calcium sand-shale.Few amount of mantle-type CO2 is developed in the Ⅱfault zone and it’s surrounding of eastern Qiongdongnan basin.The mantle-type CO2 accumulation is mainly controlled by mantle-derived volcanic activity and deep fault.