海拉尔盆地乌尔逊凹陷片钠铝石的碳氧同位素组成及流体来源探讨  

C-O isotope composition of dawsonite and its implication on the fluid origin in Wuerxun sag,Hailaer basin,China

作　　者：高玉巧[1] 刘立[1] 张福松[2] 张延洁[3] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中国科学院地质与地球物理所,北京100029 [3]吉林大学测试科学实验中心,长春130026

出　　处：《岩石学报》2007年第4期831-838,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金项目:岩浆成因二氧化碳气藏中储集砂岩的热对流成岩作用(40372060)资助

摘　　要：作为胶结物或交代自生矿物,片钠铝石(分子式为NaAlCO_3(OH)_2)大量发育于海拉尔盆地乌尔逊凹陷下白垩统南屯组、大磨拐河组砂岩中。根据片钠铝石稳定同位素组成,探讨了片钠铝石中碳的来源。片钠铝石的δ^(13)C分布连续,其范围为-5.253‰～-1.210‰(PDB),δ^(18)O分布范围为-24.896‰～-20.960‰(PDB),考虑到海拉尔盆地探井中未钻遇碳酸盐地层,片钠铝石属岩浆成因碳酸盐范畴。结合与片钠铝石平衡的CO_2的δ^(13)C值,含片钠铝石井和幔源CO_2气井分布相吻合且位于燕山期花岗岩或附近的深大断裂带上,认为海拉尔盆地乌尔逊凹陷岩浆活动-砂岩成岩(片钠铝石形成)-幔源CO_2气成藏不论在物质成分上还是在时空上均具备较好的耦合关系,形成片钠铝石所需的CO_2气为与燕山期岩浆作用有关的幔源CO_2气,深大断裂是深部CO_2气向上运移到浅部砂岩的主要通道,片钠铝石形成时因油气充注而介入少量生物成因碳。Dasonite, NaAlCO3 （OH）2, is widespread as a cement and replacement in sandstone from Nantun Formation and Damoguaihe Formation of the lower Cretaceous in Wuerxun sag, Hailaer basin. The origin of the carbon in dawsonite is studied by stable isotope composition. Dawsonite δ^13C （PDB） values range from -5. 253‰ to - 1. 210‰ and are remarkably consistent. δ^18s O（PDB） values range from -24. 896‰ to -20. 960‰. These values indicate magmatic source for carbon in the dawsonite in the view of the fact that carbonate rock is not available in all exploratory well in Hailaer basin. It can be concluded that the coupling between magma activity, diagenesis of sandstone （including the form of dasonite） and CO2 gas reservoir is fine either in composition or in space-time according to the calculated δ^13 C values of CO2 gas in isotope equilibrium with dawsonite and the coincidence of dawsonitecontaining well and CO2 gas well, lying along deep fracture within or adjacent to granite during Stage of Yanshan. Consequently, CO2 gas forming dawsonite is derived from mantle related to magmatic process during Stage of Yanshan. And deep fracture is main channel transporting CO2 gas from the deep to shallow sandstone. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed.

关 键 词：片钠铝石 碳氧同位素 流体来源 海拉尔盆地 

分 类 号：P597.2[天文地球—地球化学]