Stilpnomelane in the Proterozoic of the Říčany-area in Central Bohemia

 

Tamara Sidorinová, Ferry Fediuk

Geoscience Research Reports 41, 2008 (GRR for 2007), pages 191–193
Map sheets: Říčany (13-31)

Full text (PDF, 1.42 MB)

 

Abstract

Stilpnomelane, formerly known from volcano-sedimentary sequences of Central and Western parts of Barrandian Neoproterozoic, is now reported from slightly metamorphosed greywackes and albite-rhyolite tuffs and tuffites in the easternmost area of the unit. It is the first occurrence of this mineral east of the Vltava River. This typical low-grade metamorphic silicate occurs in the prehnite-pumpellyite as well as in the chlorite zones and gradually disappears in the biotite zone. Increased Fe/Mg ratios and low K-contents in the rock together with LT/LP metamorphic regime represent the prerequisite for its origin.