滇西南澜沧群多硅白云母的多型和化学成分特征及其意义

从理论、实验及实际观察的结果都表明，随着压力的增加白云母中绿鳞石的含量显著地增加，可以认为在多期变质作用过程中，尤其是在变质压力不同的多期变质作用下，形成的多硅白云母，其化学成分就会打上不同的烙印。７７个多硅白云母化学成分的统计结果表明，澜沧群低级变质岩中的多硅白云母有两种成因。在Ｎａ－Ｍｇ相关图上，反映了高压和中压变质特征，高压变质的多硅白云母约占７０％。这与用多硅白云母ｂ０值鉴别的高压和中压变质是相吻合的。多硅白云母的多型为３Ｔ和２Ｍ１型，以２Ｍ１型为主

Characteristics and Significance of Polytypes and Chemical Compositions of Phengite in Lancang Group, Southwest Yunnan Province

Theoretical and experimental researches and practical observation have all indicated that the celadonite content in the micas obviously increases with the rise of pressure. Therefore, it is considered that phengites formed in multi metamorphism, especially in the multi metamorphism of different metamorphic pressures, must be stamped with the brand of chemical composition. According to the statistical analyses of chemical compositions of 77 samples, there are two generations of phengites in Lancang Group, about 70% of the phengites are the product of high pressure metamorphism, which are consistent with the high and medium pressure metamorphisms of b o values of phengites High and medium pressure metamorphisms are also reflected in the Na Mg figure of phengites. The polytypes of phengites are 3T and 2M 1, and the last is the main polytype.