Paragenetic types of muscovite from apogranites of Transbaykal

Crystallochemical interpretations of composition diagrams (fig. 1) which show muscovites as mixtures of rnuscovitic, celadomitic, and trioctahedral (Mg-Fe-Li) minerals, bring out the following relations: a) a dependence of Li content upon the degree of filling of the octahedral positions and its correlation with the content of the ferromagnesial constituents; b) acidity-alkalinity controls of variations in the K :Rb ratio; c) composition and acidity-alkalinity of the postmagmatic solution - rock system as controlling factors in compositional variations of muscovites. Paragenetically, the following groups are identifiable on such premises: a) lithium muscovites in the zones of amazonite granites; b) muscovites in the outer zones of albitization and greisenization; c) muscovites in the inner zones of intensive albitization and greisenization. -- V .P. Sokoloff.