6 Magmatism in evolving orogens: Collision to extension. Posters Part 1

Monday, 4 October 2010
8:30 AM - 6:30 PM
Exhibition Hall

CHARACTERISATION OF THE VOLCANIC SERIEES IN THE DAMRANE (WESTERN OUGARTA, ALGERIA) AND IMPLICATION FOR THE GLOBAL MODEL OF THE WEST AFRICAN SHIELD NORTEASTERN MARGIN

Paper number: 6-6
Program: Scientific Sessions
Time: 8:30 AM – 6:30 PM

Authors

  • L. Remichi Presenting Author
    Faculty of Hydrocarbones and Chemistry, Boumerdes, N/A
  • S. Yesba
    Faculty of Hydrocarbones and Chemistry, Boumerdes, N/A
  • M. Sadaoui
    Faculty of Hydrocarbones and Chemistry, Boumerdes, N/A
  • K. Badari
    Faculty of Hydrocarbones and Chemistry, Boumerdes, N/A

Abstract

In the variscan chain of Ougarta (South Algeria), the Proterozoic is only known from some anticline cores, southeastern equivalent of the Anti-Atlas inliers of Morocco; in general, it deals the uppermost ignimbritic levels, assigned to P.III structuro-lithostratgraphic unit. However, more ancient, levels have already been described in the southeastern Ougarta (Sebkha el Mellah and assigned to the P.II unit; by comparison, the lowermost levels underlying the ignimbrites in the Damrane (southwestern Ougarta), have been assigned to this structuro-lithostratigraphic unit (P.II). Moreover, on this basis of their mostly mafic volcanic composition and of the presence of a positive gravimetric anomaly in this area, it was concluded that the western Ougarta was a landmark, between Ahaggar and Anti-Atlas of the West- African Shield. It was thus inferred that is occurred there, first and oceanization and a further obduction and related continental collision.

The detailed studies of the Damrane we present here, lead to challenge most of these conclusions, and demonstrate that:

*) the geostructural origin of both and felsic volcanisms is of late-to post orogenic (compressive) intra- continental type, devoid of any obvious nearby subduction- zone relationships ;

**) it is thus inferred that, during the Middle- Upper Proterzoic, the western Ougarta belong to a thineed continental-crust domain, backwards a hypothecal defined (aborted subduction zone or active margin? rifting?) would at most have occurred in eastern Ougarta (Sebkha el Mellah) or even farther to the east (?). As a result, the Pan-African geosuture, as far as it really exists in Ougarta, is to be searched in this direction, not in the Damrane, which at these times was governed by intra-continental crust subaerial conditions.