Lithium v granitech a jejich slidach v karlovarsko-eibenstockem masivu v Krusnych horach (Ceska republika)

Occurrence of the Li as a constituent of the Sn-W mineral assemblage is significantly anomalous within the whole Smrčiny-Krušné hory Mts. granite batholith. Lithium, tin and fluorine in micas and their source rocks have been used for geochemical mapping of their relationship to the greisen Sn deposits. The aim of the study is to increase the precision of mineral potential mapping of the lithium resources in the Nejdek part of the Karlovy Vary-Eibenstock granite Massif (Fig. 1). Rock-forming trioctahedral micas present in local granites range in composition from Fe-biotites in granites of the Older Intrusive Complex (OIC) through siderophyllite and lithian siderophyllite to zinnwaldite in the granites of the Younger Intrusive Complex (YIC). The concentrations of Li, and F in trioctahedral micas increase during differentiation proportionally to their whole rock concentrations. This pattern is in a good agreement with unique position of trioctahedral micas as the Li carriers in the rocks investigated. Contour maps of the distribution of Sn, Li and F in both the YIC and OIC granites and their trioctahedral micas show broad correspondence within high values, which in turn, reflect the already observed high positive correlation coefficients between Li and Sn. There is also a broad negative relationship of the distributions between these elements and Mg in their bulk rock composition and in micas. Locations of the known Sn greisen deposits within the „tin ring“ (Fig. 5) is broadly controlled by altitude reflecting proximity to the granite stock roof, and can be traced also by positive and negative relationships between the distributions of Sn, Li and F and Mg in granites and in micas. Seven out of eleven greisen deposits in YIC granites lie within the > 0.1 wt. % Li₂O contour in granites and within > 1.4 wt. % Li₂O in rock-forming micas (Fig. 4). Such anomalies point to the advantages of using Sn, F and Li content in such micas in exploration for greisen-type tin deposits and in the search for new lithium resources. On the other hand, the OIC granite micas have considerably lower contents of these elements (Fig. 5).