【摘要】 准噶尔盆地西北部深层分布着大量的二叠纪玄武岩,其发育的流体介质条件缺乏系统研究。本文采用二叠纪玄武岩岩心样品,对基质中的流体化学组成和碳同位素组成进行分步加热质谱法分析,结果表明二叠纪玄武岩的流体组成中H₂O的含量极高（平均13789mm3.STP/g）,次要组分为CO₂、O₂、H₂S和N2等,CO₂和CH₄的δ¹³C值（分别为-28.9‰^-15.8‰和-36.8‰^-21.9‰）位于地壳与甲烷氧化来源组分的范围内;CH₄、C₂H₆、C₃H₈和C₄H₁₀等甲烷同系物的碳同位素组成随碳数增高总体具有正序分布特征,400⁸00℃温度段释出CH₄的δ¹³C值（-25‰左右）明显重于200⁴00℃的（-35‰左右）,部分样品400⁸00℃的CH₄-C₃H₈存在碳同位素反序分布的特征,显示幔源流体挥发份特征,其中混入大量的沉积有机质热裂解成因烃类气体,应为俯冲蚀变大洋板片的沉积物脱出流体挥发份。大量的H₂O指示岛弧俯冲的再循环流体的加入,甲烷氧化来源特征的CO₂和CH₄碳同位素组成揭示经历了长期的风化过程,表明相关岩浆作用后遭受长期的抬升。更多还原

【Abstract】 The Carboniferous-Permian basalts are occurred in deep part of northwestern Junggar basin,Xinjiang,China. The volatile conditions of the Permian basaltic magmatism had not been studied. The chemical and carbon isotopic compositions of volatiles in the matrix of Permian basalt cores were measured by stepwise heating mass spectrometer. The results showed that the volatiles in Permian basalts from northwestern Junggar basin were composed of dominated H₂O with an average of 13789mm³. STP/g（ STP-standard tempeture and pressure）,with minor CO₂,O₂,H₂S and N₂. The δ¹³C values of CO₂（-28. 9‰ to-15. 8‰） and δ¹³CCH₄（-36. 8‰ ^-21. 9‰） were plotted in the δ¹³C ranges of crust and methane oxidation. The CH₄,C₂H₆,C₃H₈ and C₄H₁₀ etc.methane homologues showed the normal distribution pattern of carbon isotopic compositions among CH₄ to C₄H₁₀,which are the carbon isotopic features of thermogenic hydrocarbon gases of organic materials in oceanic sedimentary. The δ¹³C values of CH₄ released at 400 800℃（ about-25‰） are heavier than those at 200 400℃（ about-35‰）,and some samples showed partial reversal pattern in CH₄ to C₃H₈ released at 400 800℃,suggested that volatiles originated from mantle could be mixed by hydrocarbons from thermally cracked by sedimentary organic materials,which should be volatiles degassed from alterated subducted oceanic sedimentary. Large quatity of H₂O indicated the addition of recycled volatiles in arc. The chemical and carbon isotopic compositions of CO₂ and CH₄ reveal long time alteration of organic materials,and imply long time uplifting after basaltic magmatism.更多还原