ANTI-ATLAS MOROCCO GEOCHEMICAL AND FIELD DATA ANALYSIS INDICATE CADOMIAN SUBDUCTION & COLLISIONAL TECTONISM TO EDIACARAN-CAMBRIAN BOUNDARY

Thirteen erosional inliers within the Anti-Atlas Mountains of Morocco expose Neoproterozoic rocks associated with the Pan African orogenic cycle. Precision geochronologic dating, geochemical analysis and field mapping document three distinct Pan African orogenic events: the Iriri-Tichibanine orogeny (760-700 Ma), Bou Azzer orogeny (680-640 Ma) and the Ediacaran WACadomian orogeny (620-544 Ma). Traditionally, the Ediacaran WACadomian rock assemblages have been interpreted as post-collisional, overthickened crustal rocks that experienced extension and passive margin rifting. An alternative hypothesis suggests that Pan African subduction and tectonism continued to the Ediacaran-Cambrian boundary. This study has compiled geochemical data from granitoid, basaltic and BADR rocks in 8 of the 13 major erosional inliers. Over 200 geochemical plots using over 20 different binary and ternary discrimination diagrams have been analyzed. Geochemical discrimination diagrams document a clear subduction and collision related signal within all 8 of the erosional inliers studied. In addition, field data from selected inliers indicate angular unconformities between Ediacaran age Ouarzazate Supergroup rocks and younger Cambrian age rocks. Together, geochemical and field evidence suggest a continuation of Pan African collisional tectonism in the Anti-Atlas Mountains to the Ediacaran-Cambrian boundary. These results indicate that the Cadomian orogeny, previously documented in Southern Europe, continued synchronously into Northwest Africa as part of the Ediacaran Gondwana supercontinent assembly. Supercontinent rifting did not initiate until Early Cambrian time.