Geophysical Characteristics of the Roztoky Volcanic Centre, The České Středohoří Mts., Bohemia

Get it

Geophysical investigation of the Roztoky volcanic centre started by tentative modelling of a gravity low identified during gravimetric survey at scale 1:25,000. Gravity modelling was based on rock density data and roughdepthestimation derived from borehole Pd-2 (600 m deep) and core samples. It resulted in a simple model of about 1 km thickness of the caldera filling, the density of which was considered lower than that of the surrounding countryrocks.In the next stage, a complex geophysical survey including detailed gravity measurements, magnetometry, gamma-ray spectrometry and geoelectrical methods were performed. As shown by its results, the inner part of the volcaniccentre isdivided into two gravity minima separated by a zone where higher content of subvolcanic rocks (essexites, monzodiorite - "rongstockite") can be expected. The "rongstockite" body, clearly distinguished from thesurroundingpseudotrachyte breccia filling of the caldera by all methods, is probably a part of a larger intrusive are present at the other side of the caldera (NW). On regular geophysical profiles, rocks or zone of different contentof magneticminerals and K-U-th elements were localized, as well as the faults and indications of mineralization. These data were utilized to modify the geological map of the area. the whole study was supported by detailed rocksampling fromsurface outcrops and from boreholes Pd-2 and R-1 … full description

Bibliographic Details

Main Author

Jan Mrlina

Document Type

Articles

Physical Description

il.

Published in

Geolines. -- ISSN 1210-9606. -- Roč. 9, (1999), s. 97-103

Subjects

Magmatism and Rift Basin Evolution > (1998 : > Rychnov nad Kněžnou, Česko)

vulkano-tektonická struktura > kaldera > essexit > trachyt > nefelinit > brekcie vulkanická > dajka > vlastnosti fyzikální > měření gravimetrické > měření radiometrické > terciér > Česká republika > Čechy