Publication details

Magnetic fabrics in volcanic rocks of Křivoklát-Rokycany Complex, Czech Republic



Year of publication 2016
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description Křivoklát-Rokycany complex consists of Cambrian volcanic rocks, namely rhyolite and andesite-dacite. It was preserved only one part of the complex and the volcanic body is delimited by a tectonic fault with the NE-SE orientation. In the NE outcrops Sýkořice Porphyry and it has been recognized as a feeding structure of the complex. While the rocks inside of the complex have magnetic susceptibility in order of magnitudes at least 10-5 SI, the Sýkořice Porphyry is compound only by diamagnetic minerals. Rhyolite zone in Křivoklát-Rokycany Complex forms a lot of hills. This part is younger than andesitic one. Due to new findings, we consider almost each hill to be a small volcanic center. All the magmatic foliations around the centers are always centroclinal with increasing dip angle towards the center. Steep magmatic foliations in the feeding centers make the rock very resistant to weathering and lead to positive topography. So, we can usually find these centers at the tops of majority of topographic elevations spread in the large area and the NE-SW tectonic fault does not affect settings of those small volcanic centers. The rocks of the older andesitic part contain different AMS fabrics. The highest degree of anisotropy with oblate character was found close to the contact of andesite and dacite. In the andesitic part, it is possible to distinguish three types of volcanic rocks. Two types are controlled by ferromagnetic minerals, the third type consist of paramagnetic minerals. This non-homogeneity probably reflects changes of viscosity and mineral composition. The correlation between magnetic and magmatic fabric was investigated. We observe structures representing magma flow as magmatic foliation and bubble prolongation in andesitic part in few localities. The magnetic lineation is parallel in all cases to the direction of magma flow. Therefore, we can consider magnetic foliations (K3) as poles representing magmatic foliations and magmatic lineations (K1) as directions of magma flow.

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