A new Jurassic paleomagnetic data and emplacement conditions study of the CAMP Gara Djebilet dykes (Tindouf Basin, Southwest Algeria).
Résumé
The Central Atlantic Magmatic Province (CAMP) is one of the largest
identified Mesozoic basalt provinces formed approximately 200 Ma ago as a preamble
to the Pangea dismemberment. Recent 40Ar/39Ar dating and geochemical analyses of
dolerite sills and dykes and basalt lava flows in southwestern Algeria (Bechar area,
Reggane, Hank and Tindouf basins) showed that these rocks are parts of the CAMP.
These data represented good arguments to perform geological field observations and
sampling for paleomagnetic and magnetic fabric (AMS) investigations in the Tindouf
basin CAMP formations. Three NE-SW oriented long doleritic dykes (198.9 ±1.8 Ma)
in this basin were targeted in order to find out the structural context of their
emplacement (magnetic fabric) and to determine a new reliable Jurassic pole. The
magnetic fabric, in almost the whole sampled sections, is defined mainly by clustering
of k1 and k2 axes on the dyke plane whereas the k3 axis is nearly perpendicular to it.
This fabric is therefore interpreted as due to magma flow. The new Jurassic
paleomagnetic pole, of a good quality, is very close to those obtained from coeval
detrital Algerian Saharan formations and those recently determined from coeval
Moroccan igneous formations, it is also very close to the 200 Ma mean African pole.
These results constitute a considerable contribution to a more precise knowledge of the
geodynamical context during this period.