KUBEŠ, Martin and Jaromír LEICHMANN. The origin of extremely magnetic granitoids from the Brno batholith: evidence of metasomatic replacement of paramagnetic to ferromagnetic phases influencing geomagnetic properties of the entire Slavkov terrane. In 11th Geosymposium of Young Researchers : Silesia 2018. 2018. ISBN 978-83-951016-0-1.
Other formats:   BibTeX LaTeX RIS
Basic information
Original name The origin of extremely magnetic granitoids from the Brno batholith: evidence of metasomatic replacement of paramagnetic to ferromagnetic phases influencing geomagnetic properties of the entire Slavkov terrane
Name in Czech Původ extrémně magnetických granitoidů brněnského batolitu: metasomatická přeměna paramagnetických na feromagnetické fáze ovlivňující geomagnetické vlastnosti slavkovského teránu
Authors KUBEŠ, Martin (203 Czech Republic, guarantor, belonging to the institution) and Jaromír LEICHMANN (203 Czech Republic, belonging to the institution).
Edition 11th Geosymposium of Young Researchers : Silesia 2018, 2018.
Other information
Original language English
Type of outcome Presentations at conferences
Field of Study 10505 Geology
Country of publisher Poland
Confidentiality degree is not subject to a state or trade secret
WWW URL
RIV identification code RIV/00216224:14310/18:00106977
Organization unit Faculty of Science
ISBN 978-83-951016-0-1
Keywords (in Czech) granitoidy; Fe-Ti oxidy; slavkovský terán
Keywords in English granitoids; Fe-Ti oxides; Slavkov terrane
Tags International impact, Reviewed
Changed by Changed by: Mgr. Martin Kubeš, učo 397225. Changed: 13/2/2020 19:00.
Abstract
The bulk magnetic susceptibility of granitoids is controlled by the presence of pure magnetite (TiO2 < 0.145 wt. %) which originated along with diamond-shaped titanite as a result of the reaction between early magmatic Fe-Ti oxides, annite and anorthite during late-magmatic stages under relatively oxidizing conditions. The late oxidation of granitoids has led to releasing of Fe2+ from mafic silicates and subsequent formation of pure magnetite with increased contents within tonalites due to different whole-rock chemistry (SiO2 58–65 wt. %, FeO 3.98–7.19 %, MgO 1.46–3.52 %, CaO 3.7–6.05 %, TiO2 0.63–0.89 %) and degree of fractionation (Rb/Sr 0.036–0.048, K/Ba 19.434–22.43) reflecting distinct chemical composition of Fe-rich mafic silicates (chamosite ~ 24 wt. % FeO) compared to more felsic granodiorites (SiO2 ~ 67.3 wt. %, FeO 2.86–3.04 %, MgO 1.08–1.28 %, CaO 1.5–1.86 %, TiO2 0.38–0.5 %) exhibiting relatively higher degree of fractionation (Rb/Sr 0.085–0.233, K/Ba 30.23–51.91) which typically contain Mg-clinochlore depleted in Fe2+ (~ 20 wt. % FeO). The substantial source of Fe2+ for production of pure magnetite in an evolved and crystallized magmatic system in oxidizing regime appears to be biotite which consumes O2 as was experimentally proven: Annite + 1/2O2 = Magnetite + K-feldspar + H2O (Wones and Eugster 1965). The metasomatic mineralogical alteration, well described on examined granitoid varieties of the Eastern complex of the Brno batholith, apparently had a tremendous impact on the geomagnetic behaviour of entire eastern part of the Brunovistulicum (Slavkov terrane) forming widespread regional magnetic anomalies in the basement of Neogene sediments of Western Carpathians.
PrintDisplayed: 16/8/2022 11:18