U-Pb baddeleyite and zircon ages of 2040 Ma, 1650 Ma and 885 Ma on dolerites in the West African Craton (Anti-Atlas inliers): Possible links to break-up of Precambrian supercontinents

Abstract

Precambrian inliers of the Anti-Atlas belt in the southern part of Morocco contain numerous dolerite dyke and sill swarms which were previously poorly dated. Four dykes and two sills dated by the U-Pb TIMS method on baddeleyite and zircon provide the first steps toward a magmatic 'barcode' for the West African Craton (WAC) and constraints on the timing of breakup of the WAC from Precambrian supercontinents. A 2040 +/- 2 Ma (U-Pb zircon) age for a WNW dyke in the Zenaga inlier, matches the published age of a dyke in the Tagragra of Tata inlier, and also those of Eburnean granites observed in several inliers, which are collectively interpreted to represent ca. 2040 Ma bimodal magmatism due to a mantle plume. Based on the presence of matching 2040 Ma ages, the WAC may have been connected to the North Atlantic Craton at the initial stage of fragmentation of a late Archean continent. U-Pb baddeleyite ages of 1656 9 Ma and ca. 1655 Ma from sills in the Zenaga inlier and 1654 +/- 16 Ma from a NE-trending dyke in the Agadir Melloul inlier are similar to intraplate magmatic ages in eastern and northern Baltica, and support the SAMBA reconstruction (part of the Nuna supercontinent) of the WAC adjacent to Baltica. Approximate U-Pb ages of 885 Ma for two dykes in the Iguerda-Taifast and Zenaga inliers date a NE trending swarm (named herein the Iguerda-Taifast swarm) which is connected to the initial breakup of the supercontinent Rodinia, and a specific link with the Sao Francisco/Congo and North China craton is considered. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved