Extremely magnetic granitoids from the Eastern part of the Brno
batholith: influence of late-magmatic alteration in oxidizing
regime

k 2018

Extremely magnetic granitoids from the Eastern part of the Brno batholith: influence of late-magmatic alteration in oxidizing regime

KUBEŠ, Martin a Jaromír LEICHMANN

Základní údaje

Originální název

Extremely magnetic granitoids from the Eastern part of the Brno batholith: influence of late-magmatic alteration in oxidizing regime

Název česky

Extrémně magnetické granitoidy východní zóny brněnského batolitu: vliv pozdně magmatické alterace v oxidačním režimu

Autoři

KUBEŠ, Martin a Jaromír LEICHMANN

Vydání

Brunovistulicum 2018, 2018

Další údaje

Typ výsledku

Prezentace na konferencích

Utajení

není předmětem státního či obchodního tajemství

Klíčová slova česky

brněnský masiv; Fe-Ti oxidy; magnetit

Klíčová slova anglicky

Brno batholith; Fe-Ti oxides; magnetite

Příznaky

Mezinárodní význam

Změněno: 12. 5. 2019 17:56, Mgr. Martin Kubeš, Ph.D.

Anotace

V originále

Within Eastern Granitoid Complex were distinguished two petrophysically different varieties of plutonic rocks: (1) extremely magnetic amphibole-biotite tonalites (κ ~ 1 x 10-2 SI) exhibiting lower contents of radioactive elements (2) biotite granodiorites with lower susceptibility ca. 1 x 10-4 SI and relatively higher natural radioactivity. The bulk magnetic susceptibility of granitoids is controlled by the presence of pure magnetite with low TiO2 content (< 0,145 wt. %) and other trace components, such as V2O3, Al2O3, Cr2O3, SiO2 (< 1 wt. %). Additionally, the results of thermal analysis confirmed the absence of earlier magmatic titanomagnetite and measured values of Curie temperature (585 – 601 oC) and the Verwey transition (approximately – 160 oC) demonstrated the occurrence of pure to slightly oxidized pure multi-domain magnetite closely associated with mafic silicates. The increased contents of pure magnetite along with diamond-shaped titanite originated as a result of the reaction between early magmatic titanomagnetite, annite and anorthite in metaluminous tonalites due to different whole-rock chemistry (SiO2 58–65 wt. %, FeO 3,98–7,19 wt %, MgO 1,46–3,52 wt %, CaO 3,7–6,05 wt. %, TiO2 0,63–0,89 wt. %) reflecting distinct chemical composition of Fe-rich mafic silicates (chamosite ~ 24 wt. % FeO) which represented the substantial source of Fe2+ for the formation of pure magnetite in an evolved and crystallized magmatic system under relatively oxidative conditions. In contrast with more felsic metaluminous to peraluminous biotite granodiorites (SiO2 ~ 67,3 wt. %, FeO 2,86–3,04 wt. %, MgO 1,08–1,28 wt. %, CaO 1,5–1,86 wt. %, TiO2 0,38–0,5 wt. %) which characteristically contain mafic silicates depleted in Fe2+ (Mg-clinochlore ~ 20 wt. % FeO).

Citovat

KUBEŠ, Martin a Jaromír LEICHMANN. Extremely magnetic granitoids from the Eastern part of the Brno batholith: influence of late-magmatic alteration in oxidizing regime. In Brunovistulicum 2018. 2018.

@proceedings{1422898,
   author = {Kubeš, Martin and Leichmann, Jaromír},
   booktitle = {Brunovistulicum 2018},
   keywords = {Brno batholith; Fe-Ti oxides; magnetite},
   title = {Extremely magnetic granitoids from the Eastern part of the Brno batholith: influence of late-magmatic alteration in oxidizing regime},
   year = {2018}
}

TY  - CONF
ID  - 1422898
AU  - Kubeš, Martin - Leichmann, Jaromír
PY  - 2018
TI  - Extremely magnetic granitoids from the Eastern part of the Brno batholith: influence of late-magmatic alteration in oxidizing regime
KW  - Brno batholith
KW  - Fe-Ti oxides
KW  - magnetite
N2  - Within Eastern Granitoid Complex were distinguished two petrophysically different varieties of plutonic rocks: (1) extremely magnetic amphibole-biotite tonalites (κ ~ 1 x 10-2 SI) exhibiting lower contents of radioactive elements (2) biotite granodiorites with lower susceptibility ca. 1 x 10-4 SI and relatively higher natural radioactivity. The bulk magnetic susceptibility of granitoids is controlled by the presence of pure magnetite with low TiO2 content (< 0,145 wt. %) and other trace components, such as V2O3, Al2O3, Cr2O3, SiO2 (< 1 wt. %). Additionally, the results of thermal analysis confirmed the absence of earlier magmatic titanomagnetite and measured values of Curie temperature (585 – 601 oC) and the Verwey transition (approximately – 160 oC) demonstrated the occurrence of pure to slightly oxidized pure multi-domain magnetite closely associated with mafic silicates. The increased contents of pure magnetite along with diamond-shaped titanite originated as a result of the reaction between early magmatic titanomagnetite, annite and anorthite in metaluminous tonalites due to different whole-rock chemistry (SiO2 58–65 wt. %, FeO 3,98–7,19 wt %, MgO 1,46–3,52 wt %, CaO 3,7–6,05 wt. %, TiO2 0,63–0,89 wt. %) reflecting distinct chemical composition of Fe-rich mafic silicates (chamosite ~ 24 wt. % FeO) which represented the substantial source of Fe2+ for the formation of pure magnetite in an evolved and crystallized magmatic system under relatively oxidative conditions. In contrast with more felsic metaluminous to peraluminous biotite granodiorites (SiO2 ~ 67,3 wt. %, FeO 2,86–3,04 wt. %, MgO 1,08–1,28 wt. %, CaO 1,5–1,86 wt. %, TiO2 0,38–0,5 wt. %) which characteristically contain mafic silicates depleted in Fe2+ (Mg-clinochlore ~ 20 wt. % FeO).
ER  -

KUBEŠ, Martin a Jaromír LEICHMANN. Extremely magnetic granitoids from the Eastern part of the Brno batholith: influence of late-magmatic alteration in oxidizing regime. In \textit{Brunovistulicum 2018}. 2018.

Podrobný výpis o publikaci