Acta Musei Moraviae

Distribution of tremolite marbles in the Bohemian massif

Tremolite marbles with abundant, large porphyroblasts of dark to light gray tremolite represent a specific lithotype of marbles in some crystalline complexes of the Bohemian Massif. They are typically located in the geological units overlying the units with at least Proterozoic age. The host rock complexes consist of dominant metapelites (mica schists, gneisses) with common intercalations of quartzites, marbles, minor metabasites and graphite-rich rocks, Tremolite marbles form relatively thin layers within large metacarbonate bodies or relatively small individual lenses. Two compositional types were recognized, calcite- and dolomite-dominant, respectively. Typical mineral assemblages are Cal+Tr±Phl and Dol+Cal+Tr±Phl, the higher-grade minerals such as forsterite, diopside and spinel occur only exceptionally. Tremolite is present in several texturally and perhaps also compositionally distinct types; however, early large porphyroblasts are dominant.