Two Types of Highly Differentiated Topaz-Bearing Granites of the Salmi Batholith, Southern Karelia

Abstract

Differences between two types of highly differentiated granites of the Salmi batholith: namely Li-siderophyllite topaz-bearing and Li–F topaz-zinnwaldite granites, were determined based on the study of their structural-morphological, mineralogical and geochemical features are determined. The high degree of the differentiation of these granites is confirmed by the presence of primary topaz, Li-micas of magmatic origin and by the presence of significative tetrad effect of M type. These granites are distinguished due to the types of their micas, the content of topaz (up to 1 and 15%, respectively), the morphology of granite intrusions and the geochemistry of rare elements. The Li–F zinnwaldite granites are depleted in REE and enriched in Ta, Hf, Ba, Sr compared to the Li-siderophyllite granites. The Li-siderophyllite granites clearly fit to the general evolution trend of the Salmi batholith granites, while the genesis of Li–F zinnwaldite granites seems to be associated not only with the processes of crystallization differentiation of the melt but also with the active addition of some components, primarily F and Li, probably from a deeper source, including the mantle.