Preliminary palaeomagnetic study of the High Tatra granites, Central Western Carpathians, Poland

Abstract

Variscan granitoids of the High Tatra Mts. in Poland were the subject of palaeomagnetic, petrographical and rock magnetic investigations. The sampled rocks were granodiorites, rarely tonalites showing weak hydrothermal alterations (chloritisation, epidotisation). 31 hand samples from 7 localities were palaeomagnetically investigated. Stable palaeomagnetic directions of Late Palaeozoic age were isolated in four localities (mean direction: D = 193º, I = 17º, a95 = 12, k = 59, palaeopole: 4ºE, 31ºS). The stable magnetisation resides in hematite. This mineral occurs in hematite-ilmenite intergrowths that exsolved in high temperatures (670-720ºC) and as secondary hematite of hydrothermal origin. Because of heterogeneity of magnetic carriers it is possible that the characteristic magnetisation is shifted in time between localities. Question of tectonic tilt of the High Tatra granite is discussed. The age of characteristic magnetisation based on palaeoinclination estimations apparently fits the isotopic cooling age of the intrusion (330-300 Ma) if tectonic correction is not applied. The palaeopole is situated between the European and African Apparent Polar Wander Paths (APWP) and could be matched with both reference curves. After tectonic correction the palaeopole could be matched only with the African APWP at the point ca. 360 Ma. In this case the magnetisation related to the high temperature hematite would preceed the cooling ages recorded by Ar-Ar method.