Paleomagnetism of mafic dikes from the Avalon Peninsula, eastern Newfoundland

Abstract

As part of a major study of the Avalon zone in eastern Newfoundland, we describe the palromagnetism of two series of dikes located in the Bauline and Colliers-Harbour Main areas, respectively. Detailed alternating field (AF) and thermal experiments performed on these dikes indicate that they are characterized by two significantly different mean directions of magnetization: SE++(D = 153°, I = +62°; K = 46, N = 12 sites) and SW (D = 217°, I = +58°, K = 58, N = 12 sites ) with corresponding paleopole positions at A (4°N, 34°W; dp,dm = 8°, 10°) and C (2°N, 81°W; dp, dm = 6°, 9°). Antipoles A and C are located in southerly latitudes, and a comparison with other poles of Avalonian rocks from New Brunswick, Nova Scotia and Newfoundland indicates a Silurian to Siluro-Devonian age for these dikes. Poles A and B are interpreted as representing rapid apparent polar wander with respect to eastern Newfoundland during Silurian time. Two components of magnetization, corresponding to two distinct geological events, are observed in the dikes investigated and this situation favours the following geological scenario for the evolution of the Avalon microcontinent: ; dp,dm = 8°,10°) et C (2°N, 81°0; dp,dm = 6°, 9°). Les antipoles A et C se situent a des latitudes meridionales et par comparaison avec d'autres poles de roches avaloniennes du Nouveau-Brunswick, de la Nouvelle-Ecosse et de Terre-Neuve, on attribue aux dykes un age Silurien a Siluro-Devonien. On interprete les poles geomagnetiques A et B comme le resultat de deplacements rapides du pole par rapport avec l'est de Terre-Neuve durant le Silurien. On observe dans ces dykes deux composantes de magnetisation, correspondant a deux evenements geologiques distincts. Ceci suggere le scenario suivant pour expliquer l'evolution du microcontinent Avalon: (a) un rift intracratonique qui se traduit par une longue periode d'extension continentale depuis l'Hadrynien tardif jusqu'au Cambrlen; (b) du Silurien jusqu'au debut du Devonien, une phase tardive de distension lors de la separation des miniplaques.