Record details

Title
    Geophysical Characteristics of the Roztoky Volcanic Centre, The České Středohoří Mts., Bohemia
Statement of responsibility
    Jan Mrlina
Other titles
    Magmatism and Rift Basin Evolution (Variant.)
Author
    Mrlina, Jan
Language
    anglicky
Source title - serial
    Geolines
Vol./nr.
    Vol. 9
Pages
    p. 97-103
Year
    1999
Notes
    9 obr., 1 tab., 10 bibl.
Subject group
    brekcie vulkanická
    dajka
    essexit
    kaldera
    měření gravimetrické
    měření radiometrické
    nefelinit
    prvky radioaktivní
    struktura vulkano-tektonická
    terciér
    trachyt
    vlastnosti fyzikální
    vulkanity Českého středohoří
Geographical name
    ČR-Čechy
    Roztoky (Ústí nad Labem)
Keyword
    Bohemia
    Centre
    Characteristics
    České
    Geophysical
    Mts
    Roztoky
    Středohoří
    Volcanic
Abstract (in english)
   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 rough depth estimation 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 country rocks. 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 volcanic centre is divided 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 the surrounding pseudotrachyte 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 content of magnetic minerals 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 rock sampling from surface outcrops and from boreholes Pd-2 and R-1
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    21. 3. 2008
Import date
    8. 8. 2012