Folding and inversion tectonics in the Anti‐Atlas of Morocco

Abstract

The late Variscan Anti‐Atlas of Morocco shows some conspicuous deviations from the standard anatomy of foreland fold‐and‐thrust belts. Large basement inliers crop out at a very short distance of less than 50 km behind the southeastern front of the fold belt, reminiscent of Windriver‐style basement uplifts. In contrast to the Rocky Mountain foreland, however, the Anti‐Atlas basement uplifts punctuate tightly folded Paleozoic cover series similar in tectonic style to the Appalachian Valley and Ridge province. Cover shortening is exclusively accommodated by buckle folding, and the Anti‐Atlas fold belt lacks any evidence for duplexing or thrust faults other than the occasional steep reverse fault found near basement inliers. Basement domes have classically been considered as the result of vertical tectonics in a horst and graben fashion, or, alternatively, as large “plis de fond” [Argand, 1924], basement folds. Unfolding of a large portion of an Ordovician quartzite marker bed reveals a minimum shortening of 17% (30 km). Balancing this section at the crustal scale indicates a lower crustal detachment level at 18 to 25 km depth. Basement shortening is inferred to be accommodated through massive inversion of former extensional faults, inherited from a Late Proterozoic‐Lower Cambrian rifting phase.

Geology and Metallogenesis of the Sediment-Hosted Cu-Ag Deposit of Tizert (Igherm Inlier, Anti-Atlas Copperbelt, Morocco)

“…The epigenetic view is supported when the copper sulphide mineralization displays an intense structural control indicating that mineralization took place contemporaneously with basin inversion and orogeny. The Anti-Atlas Belt in Morocco comprises large Proterozoic basement inliers consolidated during the Eburnean and the Pan-African orogeny [11] and a Late Ediacaran to Paleozoic sedimentary cover weakly folded during the Hercynian orogeny [12,13]. The terminal Neoproterozoic to Lower Cambrian cover includes important copper orebodies ( Figure 1), with up to 200 occurrences [14], some of which are currently mined.…”

Illite crystallinity patterns in the Anti-Atlas of Morocco

“…the shortening in the western part of the AA lies between 15% and 25% (Helg et al 2004;burkhard et al 2006). No large-scale thrusting or duplexing is known.…”

“…the Variscan shortening in the western Anti-Atlas varies between 15 and 25% (caritg et al 2003;Helg et al 2004;burkhard et al 2006;robert-charrue & burkhard this volume). In a very simple model assuming constant cross section area, the tectonic thickening would be roughly of the same magnitude, i.e.…”

Application of remote sensing and GIS in mineral resource mapping-An overview

“…The white sinuous band against a fold ridge is a dry stream. Recently, Helg et al (2004) showed that the Anti Atlas of Morocco is a special type of foreland fold belt lacking any evidence for thrust faults other than the occasional steep reverse fault found near basement inliers. (Courtesy: NASA and Earth Satellite Corporation.)…”