【摘要】 通过脱碳反应的平衡热力学计算 ,推导出碳酸盐岩石变质流体中CO2 活度αCO2 的估算公式。将其用于内蒙古集宁群孔兹岩系的大理岩 ,得出在麻粒岩相变质峰期前进变质阶段流体已具有较高αCO2 的值 (>0 .5 )。此结果与已有研究结果吻合 ,表明在进变质过程中随脱碳反应规模加大 ,析出的CO2 使流体中αCO2 值相应增大 ,至变质峰期此值达 0 .8以上。不同样品中αCO2 值有一定变化 (0 .5 37～ 0 .6 43)也进一步表明变质过程中CO2 为内部缓冲 ,并非深部来源。更多还原

【Abstract】 The equation for estimating α CO 2 in metamorphic fluid of carbonate rocks is formulated by thermodynamic calculation for equilibrium state of decarbonation. The application of this method to marble from Jining Group in Inner Mongolia reveals that the α CO 2 value of fluid in the progressive stage of granulite facies metamorphism is higher than 0.50,which is consistent with the data from recent researches. All evidence displays that the α CO 2 value of fluid increased gradually in the progressive metamorphic process and reached 0.80 in its peak stage, which is attributed to the continuous separation of CO 2 with the intensification of decarbonation. Morever, some variations of α CO 2 among samples (from 0.537～0.643) also suggest that CO 2 in the decarbonation process is most likely derived from internal buffering rather than from the deep source. Key word:更多还原