On the effect of lava viscosity on the magnetic fabric intensity in alkaline volcanic rocks |
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| Authors: | F Hrouda M Chlupá?ová K Schulmann J ?míd P Závada |
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| Institution: | (1) AGICO Inc., Je ná 29a, Box 90, CZ-621 00 Brno, Czech Republic;(2) Institute of Petrology and Structural Geology, Charles University, Albertov 6, CZ-128 43 Prague 2, Czech Republic;(3) Université Louis Pasteur Strasbourg I., 1 rue Blessig, F-670 84 Strasbourg Cedex, France |
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| Abstract: | The degree of the anisotropy of magnetic susceptibility (AMS) of basaltic rocks, as is known from the large AMS database of these rocks, is generally very low, while in more acidic volcanic rocks such as andesites, trachytes and phonolites, which have been investigated much less frequently, it is in general much higher. In the present study, the AMS of various volcanic rocks including trachytic and phonolitic rocks was investigated in the Tertiary volcanic region of the  eské st edohoí Mts. Viscosities of the respective lavas were calculated from the chemical composition using the KWARE program. A rough correlation was found between the degree of AMS and lava viscosities, probably resulting from different mechanisms orienting the magnetic minerals. In basaltic lava flows this mechanism is traditionally considered to be of a hydrodynamic nature, in trachytic and phonolitic bodies it can also be represented by quasi-intrusive flows resembling, at least partially, ductile flow deformation. This is in agreement with the AMS data predicted by the viscous (liquid flow) and line/plane (ductile flow) models. |
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| Keywords: | magnetic anisotropy lava viscosity volcanic rocks |
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