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内蒙古兴和-卓资太古宙孔兹岩系变质峰期水活度、氧逸度及其化学位变化
The activity of H2O,fugacity of O2 and variation of their chemical potential during metamorphic peak of the Archaean khondalite series from Xinghe Zhuozi district,Inner Mongolia
【摘要】 通过脱水反应的平衡热力学计算确定内蒙古兴和-卓资太古宙孔兹岩系变泥砂质岩中变质峰期aH2O 总体较低, 变化于0.12~0.40 之间, 黑云紫苏片麻岩中aH2O为0.20~0.43。前者的logfO2 值最高为- 13~- 15, 但在有些岩石中极低,(μH2 O/XBtM g )P,T和(μO2 /XBtM g )P,T的系数主要变化于- 0.241~- 0.383 和- 1.052~- 1.810,(μH2O /μO2 )P,T的斜率也有一定变化。这些数值变化特征按 “碳质变质”观点不应出现, 主要也不是脱水熔融作用所致, 它们可能与非完全开放系统中H2O较CO2 易于逸散有关
【Abstract】 Based on thermodynamic calculation of dehydration reactions, the activity of H 2O ( a H 2O ) in meta pelitic psammitic rocks of Archaean khondalite series from the studied region during its metamorphic peak has been measured with the value varying from 0 12 to 0 40 Higher a H 2O values of 0 20~0 43 have been obtained from intercalated biotite hypersthene gneiss The fugacity of O 2 in term of log f O 2 in the former rock type is less than -13~-15 The coefficient of ( μ H 2O / X Bt Mg ) P,T and ( μ O 2 / X Bt Mg ) P,T in this rock type is mainly in range of -0 241~ -0 383, and -1 052~-1 810, respectively, and the slop of ( μ H 2O / μ O 2 ) P,T is also variable On the basis of regional geological setting, such characteristics of variation is neither consistent with evidence hoped by the view of “carbonic metamorphism”, nor can be entirely explained by dehydration melting These features may be related to preferably escaping of vapour (formed by dehydration reactions) to CO 2 (produced by oxidation of organic materials from protolith) within a not completely open system
【Key words】 Activity of H2O; Fugacity of O2; Coefficience of chemical potential; Khondalite series; Inner Mongolia;
- 【文献出处】 岩石学报 ,ACTA PETROLOGICA SINICA , 编辑部邮箱 ,1999年04期
- 【分类号】P588.34
- 【被引频次】9
- 【下载频次】219