多硅白云母b_0值对澜沧群中压和高压变质的反映  

THE MEDIUM-AND HIGH-PRESSURE METAMORPHISMS OF LANCANG GROUP REFLECTED BY b_0 VALUES OF PHENGITES

作　　者：宋仁奎[1] 应育浦[1] 叶大年[1] 

机构地区：[1]中国科学院地质研究所,北京100029

出　　处：《地质科学》1997年第1期56-64,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金

摘　　要：多硅白云母b_0值作为相对地质压力计的理论和方法,已受到各国地质学家的普遍重视。本文以澜沧群多硅白云母作为研究对象,提出运用多硅白云母b_0值区分不同压力变质的方法。研究结果表明澜沧群经历了中压和高压变质作用,两期变质的多硅白云母b_0值分别为9.027A和9.047A。The theory and method of b_0 values of phengites regarded as a relative geobarometer have been valued by geologists of the world. There is no research on polymetamorphism reflected by b_0 values of phengites reported in the world today. We think that the populations of b_0 values must be distinguished in the study of b_0 values of phengites of low grade metamorphic rocks occurred in ancient orogenic belts, especially, for the polycyclic orogenesis in China. In this paper, the authors put forward a method of distinguishing polymetamorphism by statistical analyses of b_0 values of phengites on the basis of research on phengites of Lancang Group. Statistical analyses of 486 b_0 values of phengites show that there are medium-and high-pressure metamorphisms in Lancang Group. The intersection of two straight lines representing bi-nomal distributions is situated at the point corresponding to b_0=9.040A in probability graph. The mean b_0 value of high-pressure is 9.047, the standard deviation and cumulative probability are 0.005 and 55% respectively. The average b_0 value of medium-pressure metamorphism is 9.027A, its standard deviation is 0.010. The cumulative frequency curve of medium-pressure metamorphism is situated between cumulative frequency curves of Ryoke and Easterm Alps. The cumulative frequency curve of high-pressure is similar to that of Sanbagawa.

关 键 词：多硅白云母 b0值 高压变质 澜沧群 变质岩 

分 类 号：P588.3[天文地球—岩石学]