变质岩岩石学研究——第四讲 变质相和变质相系的研究

THE STUDY OF METAMORPHIC FACIES AND FACIES SERIES

变质相和变质相系能清楚的反映不同变质岩系和含矿建造形成时的物化条件及其在时间和空间上的变化规律。它们是研究变质作用和编制变质地质图的主要内容,也是研究变质矿床形成条件的重要方面,对它们的研究具有很大的理论和实际意义。现就这方面的发展情况作一些简要介绍。

The metamorphic facies concept has developed greatly due to the expand in the study of metamorphic rocks.The consideration of equilibrium that is necessary to be reached in metamorphic mineral assemblages has been excluded in the newly developed metamorphic facies concept.In recent years, the number of metamorphic facies has a tendency of continual increase,the author proposed four principles on the division of metamorphic facies.Based on the characteristic metamorphic mineral assemblage and metamorphic reaction and geological background,the author proposed a scheme on for the division and nomenclature of regional metamorphic facies. In this scheme the regional metamorphic facies is divided into very low temptrature metamorphic facies,low temperature metamorphic facies, medium temperature metamorphic facies, high temperature metamorphic facies and high pressure metamorphic facies.The author especially disscu-sed the indexes for making the division, forming condition and the velated problems of the regional metamorphic facies.Based on the data in our country and abrofid,the author has some different riews on the metamorphic facies series. The extensive distribution of metamorphic rocks of single metamorphic facies has been found in many metamorphic areas, thei facies series can not be determined. The 3'standard'facies series are rare in reality, and for in most of the cases only transitional types between the 3 'standard'facies series have been found in the field,tneir geothermal gradients are various. The author puts forward another concept on the paired metamorphic belts as they are composed of two different types of metamorphism, they differ from Miyashiro's paired metamorphic belts in that they are not necessarily presenting the so called low and high pressur metamorphic belts.