Studia Geophysica et Geodaetica

, Volume 54, Issue 1, pp 77–94 | Cite as

Magnetic properties of high-Ti basaltic rocks from the Krušné hory/Erzgebirge MTS. (Bohemia/Saxony), and their relation to mineral chemistry

  • Petr Schnabl
  • Jiří K. Novák
  • Vladimír Cajz
  • Miloš Lang
  • Kadosa Balogh
  • Zoltan Pécskay
  • Martin Chadima
  • Stanislav Šlechta
  • Tomáš Kohout
  • Petr Pruner
  • Jaromír Ulrych
Article

Abstract

This study provides new thermomagnetic and petrographic data on specific basaltic rock association from the broader vicinity of the Loučná-Oberwiesenthal volcanic centre, western Bohemia/Saxony. Two types of volcanic rocks were recognized there: (i) high-Ti types (3.5–5.2 wt% TiO2) represented by (mela)nephelinite s.s., and sporadically present (ii) medium-Ti types (2.5–3.5 wt% TiO2) of olivine nephelinite, nepheline basanite and phonotephrite compositions. In order to examine the rock-magnetic behaviour, they were studied for their variations in the Curie temperature (TC) and field-dependent susceptibility, spinel group minerals, chemistry and petrology.

Magnetic susceptibility of ulvöspinel-rich titanomagnetite, as a dominant magnetic carrier, depends on the amplitude of measured magnetic field, whereas pure magnetite is field-independent. Field dependence parameter kHD of the studied basaltic rocks ranges from 0.8 to 18.7%, TiO2 contents in titanomagnetite range from 12.7 to 20.1 wt.%. TiO2 content in titanomagnetite does not correlate with whole-rock TiO2 content (2.8 to 5.6 wt.%). The content of substituted titanium in the sublattice of magnetite is also sensitively reflected in the Curie temperature, ranging from 200 to 580°C. The spinel group minerals are designated as titanomagnetite with the dominance of ulvöspinel, magnetite and magnesioferrite components, or titanomagnetite with the magnetite, ulvöspinel and magnesioferrite components. Only two samples are characterized by a significant presence of Cr-spinel and magnesiochromite components forming cores of titanomagnetites.

The titanomagnetite-bearing rocks in the studied area, likewise the low- to medium-Ti basaltic rocks from the České středohoří Mts., provide similar thermomagnetic curves.

Keywords

high-Ti and medium-Ti basaltic rocks magnetic carriers thermomagnetic experiments Curie temperature variation field-dependent susceptibility Krušné hory/Erzgebirge Mts. Ohře/Eger Rift 

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Copyright information

© Institute of Geophysics of the ASCR, v.v.i 2010

Authors and Affiliations

  • Petr Schnabl
    • 1
  • Jiří K. Novák
    • 1
  • Vladimír Cajz
    • 1
  • Miloš Lang
    • 1
  • Kadosa Balogh
    • 1
  • Zoltan Pécskay
    • 2
  • Martin Chadima
    • 1
  • Stanislav Šlechta
    • 1
  • Tomáš Kohout
    • 1
    • 3
  • Petr Pruner
    • 1
  • Jaromír Ulrych
    • 1
  1. 1.Institute of GeologyAcad. Sci. of the Czech RepublicPraha 6Czech Republic
  2. 2.Institute of Nuclear Research of the Hungarian Academy of SciencesBem tér 18/CDebrecenHungary
  3. 3.Department of PhysicsUniversity of HelsinkiHelsinkiFinland

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