Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Unusual dyke rockfrom prospecting adit in the Matčina hora near Zbiroh
Abstract
Swarm of dykes of trachybasaltic composition intruded the Upper Cambrian rhyolites of the Křivoklát-Rokycany belt near the village of Přísednice, NW of Zbiroh, Teplá-Barrandian Unit (Bohemicum). The rock is composed of slightly chloritised clinopyroxene [Mg/(Fe + Mg) = 0.74-0.59], more intensively chloritised biotite [Mg/(Fe + Mg) = 0.32-0.47], totally destroyed plagioclase (to the mixture of prehnite and albite), apatite and titanite. Ilmenite and zirconolite are present in accessory amount. Two types of chlorite (after cpx and bi, and filling of vugs) and pyrite are secondary. Chemical composition is characterised by a relative higher content of Ti and K, and lower content of Cr and Ni in comparison with other Lower Paleozoic basalts of the area. Among all published chemical analyses of Barrandian basalts, the studied rock is very similar to Silurian diabases.
