【摘要】 脱水反应的热力学计算确定本区太古宙麻粒岩系变 质峰期水活度很低,太平寨地区富铝片麻岩和紫苏黑云片麻岩麻粒岩中aH 2O值一般均在0.10～0.20之间,娄子山地区相对稍高,一般为0.15～0.25。全区峰期 氧逸度lgfO2在-8～-14之间。(μH2O/XBt Mg)和(μO2/XBtMg)系数平均值太平寨地区分别为- 0.293和-1.60,娄子山地区分别为-0.364和-1.42。全区aH2O很低,同一地 区上述各种数值相当均匀,不同地区则有一定差异,这些特征与“碳质变质”机理相符,说明 峰期水活度可能受深源CO2流渗透的控制,属于外部缓冲性质。更多还原

【Abstract】 Based on the thermodynamic calculation of dehydration reaction s, the activity of water in the Archaean granulite complex in the studied region during metamorphic peak is very low (α-H-2O=0.1-0.2). The v alues of α-H-2O in Al-rich gneiss and hypersthene biotite gn eiss-granulite of the Taipingzhai district are usually 0.10-0.16, and those of the Louzishan district are somewhat higher, within the range of 0.15-0.25. Th e fugacity of O-2 in peak metamorphism in terms of lgf-O-2 is probably between -8 and -14. The average coefficients of (μ-H -2O/XBt-Mg)-p,T and (μO-2/XBt-Mg) in the Taipingzhai district are -0.293 and -1.60, respectively, and those of the Louzishan district are -0.364 and -1.420. The activity of water is very low in the whole region. Its va lues and other data mentioned above are considerably homogeneous in space even i n different lithologies of the same district. However, they vary obviously in di fferent districts. Such characteristics are compatible with the genetic mechanis m of !carbonic metamorphism" advanced by Newton et al.,i.e., the activity of H -2O in the peak stage is controlled by the permeation of pervasive CO-2 influx of the mantle source, showing features of external buffering.更多还原