On the effect of lava viscosity on the magnetic fabric intensity in alkaline volcanic rocks

Autor: Jakub Šmíd, Karel Schulmann, Marta Chlupáčová, Prokop Závada, František Hrouda
Rok vydání: 2005
Předmět:
Zdroj: Studia Geophysica et Geodaetica. 49:191-212
ISSN: 1573-1626
0039-3169
Popis: 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 Ceske středohoři 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.
Databáze: OpenAIRE
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