Natural radioactivity of metamorphic and igneous rocks and pre-Cenozoic sedimentary rocks on the map sheet 14-41 ŠumperkArticle PDF
Natural radioactivity of metamorphic and igneous rocks and pre-Cenozoic sedimentary rocks on the map sheet 14-41 Šumperk
The aim of the paper is to inform about natural radioactivity of metamorphic and igneous rocks and pre-Cenozoic sedimentary rocks on the map sheet 14-41 Šumperk. The area covering the map sheet belongs to the Lugicum, namely to five groups of the Orlica-Śnieżnik Unit (Młynowiec-Stronie, Śnieżnik-Gierałtów, Nové Město, Staré Město and Zábřeh Groups) including serpentinites and a so-called tonalite sill, and to the Silesicum (Keprník, Branná and Desná Groups, and Šumperk Massif). Unmetamorphosed pre-Cenozoic sedimentary rocks are represented by siliciclastics of the Bohemian Cretaceous Basin (Bílá Hora and Jizera Formations). Contents of potassium, uranium and thorium were measured using a laboratory gamma-ray spectrometer in 1481 rock samples. Data are tabled and discussed. Most rocks outcropping on the map sheet show low values of mass activity of 226Ra equivalent, lower than that for average Earth crust (about 180 Bq.kg-1). Increased values of mass activity were found in three types of rocks near Ruda nad Moravou: syenitoid (363 Bq.kg-1 in average), rodingite (465 Bq.kg-1) and leucotonalitic pegmatite with high uranium and thorium contents in a plagioclase+quartz+diopside subunit.
Jiří Zimák, Department of Geology, Faculty of Science, Palacký University, 17. Listopadu 12, 771 46 Olomouc, Czech Republic, e-mail: email@example.com