Paleomagnetism and the Alpine tectonics of Eurasia U the magnetism of the Permian porphyries near Lugano (Northern Italy, Switzerland)

Abstract

The magnetic properties of 25 oriented samples of the Permian porphyries from the Lugano district are investigated. After a.c. demagnetization (up to 900 Oe peak value) eleven samples produce a characteristic direction of magnetization, declination (D) = N 143.5°E, inclination (I) = −17°. The other samples show streaking towards the direction of the present-day geomagnetic field; their recent magnetic components are very hard and could not be removed by our a.c. demagnetization procedures. The paleomagnetic pole derived from the Lugano rocks is situated at 41.5°N 119.5°W, and is equally divergent from the other Permian poles from extra-Alpine European rocks as are the ones traced in other parts of the Alps. This divergency is best explained by assuming large-scale tectonic displacements of the south Alpine unit before and during the Alpine orogenesis.