Paleomagnetic and magnetostructural study of Jurassic formations of Gara Djebilet (Tindouf Basin, Southwestern Algeria)

Abstract

International audienceRecent geochemical analyzes and 40Ar/39Ar datings of dolerite sills and dykes and basalticlava flows from Southwestern Algeria (Tindouf, Reggane, Bechar and Hank basins) haveshown that these rocks are related to the Central Atlantic Magmatic Province (CAMP). TheCAMP is one of the largest among the Mesozoic basaltic provinces identified and formed about200 Ma ago as a preamble to the breakup of Pangea. These data were solid arguments for undertakinggeological observations and sampling for paleomagnetic studies and magnetic fabrics onthe CAMP formations. A network of three long doleritic dykes (198.9 ± 1.8 Ma) located in theTindouf Basin were targeted to clarify the structural context of their emplacement (magneticfabrics) and to determine a new reliable Mesozoic pole.The magnetic fabric, in almost all the sections sampled, is defined mainly through groupingof k1 and k2 axes on the dyke plane whereas axis k3 is almost perpendicular to the dykeplane. This fabric can therefore be interpreted as the magma flow direction. The new Jurassicpaleomagnetic pole, of excellent quality, is very close to those obtained on detrital formationsof the Algerian Sahara and close to those recently determined on igneous formations of Morocco.This new pole is also very close to the North African pole at 200 Ma. These results representa new contribution for a better knowledge of the geodynamic context during this period