Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Geological setting of “nephrite” in the contact aureole of the Tanvald-granite, North Bohemia
Abstract
A forthright outcrop of a homfelsed metabasite known up to now from the southern foreground of the granitic ridge between Tanvald and Liberec in N-Bohemia from fragments, loose stones and boulders only is reported. This rock is the source material of neolithic stone artifacts used in wide areas of Central Europe (ŠREIN et al. 2002, PŘICHYSTAL 2002, ŠREIN et al. in press). The metabasite, having the character of an amphibole hornfels, was newly uncovered in a building excavation between the Jeřmanice and Rádlo townships, 8 km SE of Liberec. The character of the outcrop clearly proves that the rock is situated in the inner part of contact aureole of the Tanvald - alkali feldspar granite and that its remarkable geotechnical properties are due to the effects of contact metamorphism. A small thickness of several decimetres and large lateral extension (a segmented length of several km) of the nephrite layer obviously represents neither a dyke nor a lava sheet, but rather a sill altered by tectonic deformation.
