Comparison of palaeomagnetic data from three Late Caledonian magmatic intrusions piercing the Upper Silesian and Małopolska tectonic blocks (S Poland), and its palaeotectonic significance

Abstract

The dioritic part of the latest Silurian intrusion drilled in the Sosnowiec IG-1 borehole and the diabase from the newly drilled Chrząstowice PIG-1 borehole, both in the Upper Silesia Tectonic Block, were palaeomagnetically studied. The palaeoinclinations of the same polarity primary component “A” are similar in the studied intrusions. They correspond well with the latest Silurian/earliest Devonian palaeoinclination obtained from the Bardo diabase (Holy Cross Mts.), and with those calculated from the Apparent Polar Wander Path for palaeocontinent Baltica. All compared intrusions represent the late Caledonian magmatic event that can be linked with the back-arc extension in the marginal part of the Old Red Continent. The angle between declinations of the latest Silurian/earliest Devonian normal polarity component “A” and the latest Carboniferous/earliest Permian secondary reversed polarity component “B”, both isolated from the Chrząstowice diabase, indicate the lack of palaeomagnetically detectable clockwise tectonic rotations of the Upper Silesia Tectonic Block with respect to stable Europe at least after the Silurian. However, a slight (up to a dozen or so degrees) anti-clockwise rotation of local sense cannot be excluded after the earliest Permian. The distribution of magnetic fabric points to the sill form of both studied intrusions.