Přirozená radioaktivita hornin moravskoslezského kulmu v oblasti Nízkého Jeseníku a Oderských vrchů: příspěvek k poznání zdrojové oblasti klastického materiálu

• Title in English: Natural radioactivity of rocks in the Moravian-Silesian Culm area in the Nízký Jeseník Mts. and Odra Hills: A contribution to understanding of a source zone of clastic material
• Authors: ZIMÁK Jiří; ŠTELCL Jindřich
• Year of publication: 2004
• Type: Article in Periodical
• Magazine / Source: Geologické výzkumy na Moravě a ve Slezsku v roce 2003
• MU Faculty or unit: Faculty of Science
• Field: Geology and mineralogy
• Keywords: Moravian-Silesian Culm; Lower Carboniferous sediments; gamma-ray spectrometry
• Description: The Upper Devonian - Lower Carboniferous siliciclastic flysch formations called the Moravian-Silesian Culm are widespread on the northeastern margin of the Bohemian Massif. The Moravian-Silesian Culm belongs to the Rhenohercynian belt of the Central European Variscides, it forms an accretion wedge developed as a result of a collision of two blocks of continental crust - the inner parts of the Bohemian Massif and the Bruno-Vistulicum. The Culm sequences in the Nízký Jeseník Mts. and Odra Hills are formed by various types of psammites (mainly graywackes), conglomerates and clay shales to siltstones, epizonally metamorphosed in the westernmost part (in the Andělská Hora Fm.). In the source zone of clastic sediments of Andělská Hora Fm. epizonally metamorphic rocks and anchimetamorphic sediments dominated. Contents of K, U, and Th in sediments of Andělská Hora Fm. were correspondingly low. Radioactivity of sediments of Moravice Fm. is much higher and even increases moderately in Horní Benešov Fm. Maximum average values are found in Hradec-Kyjovice Fm. Relatively high radioactivity of these three formations suggests a significant and gradually increasing contribution of acid magmatic rocks in the source zone of clastic material. This is especially evident in the north (in the zone of Žulová Pluton outcrop).