Příspěvek k petrografii a mineralogii lokality Vyskočilka (Praha-Malá Chuchle, silur Barrandienu)

Classical locality Vyskočilka in the Barrandian Basin displays a well-exposed section of black Silurian shales penetrated by ca. 10-m thick diabase sill. We examined petrographic character and mineral composition intrusive body enclosing shales, as well hydrothermal veins cutting rocks. The is rock with basic affinity (paleobasaltoid), which was strongly influenced post-magmatic alterations including albitization zeolitization feldspars chloritization clinopyroxenes Fe-Ti spinelides. Host sediments show variously intense thermal overprint at contact predominating are rarely accompanied laminites, formed siliciclastic material, calcite, apatite probably also pyroclastic component. A minor component all Ti-rich chromspinelides, classified chromite, magnetite, spinel. Chromspinelides form isolated euhedral single crystals reaching up to 50 µm size, their intergrowths fragments, do not display marks abrasion due transport. therefore presuppose that they represent relics ultrabasic material (volcanic ash), deposited during sedimentation sediments. There known few sills meimechites Prague containing chromspinelides comparable chemical composition, can thus likely source chromspinelides. vein mineralizations, present study site, originated different geological processes. calcite quartz hydrocarbons Variscan tectono-thermal area. By contrast, mineralization quartz, titanite, anatase, Zn-Fe-Ni-Cu sulphides associated contact-metamorphic processes related intrusion diabase.