Recycling of the Proterozoic crystalline basement in the Coastal Block (Moroccan Meseta): New insights for understanding the geodynamic evolution of the northern peri-Gondwanan realm

Abstract

Detrital zircon age spectra from the siliciclastic rocks of the Lalla Mouchaa Calcschists and El Jadida Dolomitic formations (the Coastal Block of the Moroccan Meseta) are dominated by Paleoproterozoic and Ediacaran ages. The provenance of these two formations is a composite Proterozoic crystalline basement. El Jadida rhyolite (584.2 ± 4.8 Ma) represents the Ediacaran crystalline basement of the El Jadida dome. El Jadida rhyolite is unconformably overlain by the microbreccia, arkosic sandstone and dolostone of the El Jadida Dolomitic Formation with a maximum depositional age of ca. 539 Ma (Lower Cambrian). Detrital zircon-age spectra from El Jadida Dolomitic Formation (ca. 583-582 Ma) suggest direct recycling of El Jadida rhyolite as an exclusive original primary source. However, in the Western Rehamna massif, detrital zircon-age spectra from pre-Middle Cambrian microbreccia and arkosic sandstone of the Lalla Mouchaa Calcschists Formation (ca. 2.05-2.03 Ga) indicate exclusive recycling of the ca. 2.05 Ga-aged crystalline basement rocks (original primary source). Detrital zircon contents of the siliciciclastic rocks from these two formations of the Coastal Block are consistent with derivation from either Eburnian (Paleoproterozoic) or Cadomian/Pan-African (Ediacaran) igneous rocks. The discovery of this composite Proterozoic crystalline basement in the Moroccan Meseta stresses that Cadomian/ Pan-African magmatic arcs were built on an Eburnian basement in a paleoposition close to the West African craton, as part of the northern peri-Gondwanan realm.

Tectonic Evolution of the Eastern Moroccan Meseta: From Late Devonian Forearc Sedimentation to Early Carboniferous Collision of an Avalonian Promontory

“…Nevertheless, the paleogeographic relevance of these structures is unclear, since they do not include suture‐related rocks (e.g., ophiolites), and the Ordovician‐Devonian stratigraphic successions in all the Moroccan Variscides, as well as in other zones of the northern margin of Gondwana, indicate deposition in a shared passive margin (Piqué, 1994; Simancas et al, 2009), suggesting that all the domains of the Moroccan Variscides remained attached to northern Gondwana throughout the Paleozoic. This paleogeographic affinity is also supported by the detrital zircon provenance studies performed to date (Abati et al, 2010; Accotto et al, 2019; Avigad et al, 2012; El Houicha et al, 2018; Ghienne et al, 2018; Letsch et al, 2018), which suggest a Gondwanan provenance for the Cambrian to Devonian sediments of the Moroccan Variscides. The only exception would be the Sehoul Block in the Western Moroccan Meseta (Figure 1b), which is thought to have an Avalonian derivation based on the presence of a mid‐Paleozoic (i.e., Caledonian) deformation that occurred before the emplacement of granites radiometrically dated at the Late Devonian (U‐Pb on zircons; Tahiri et al, 2010).…”

“…Paleozoic rocks are exposed in the Eastern Moroccan Meseta in relatively small (from a few square kilometers up to approximately 1,200 km 2 ) and isolated inliers (Figure 1b), characterized by Cambrian–Permian successions deformed by Eovariscan (Late Devonian–Early Carboniferous) to Variscan (Carboniferous) events (Hoepffner, 1987). The Ediacaran basement that crops out in several areas of the Western Moroccan Meseta and Coastal Block (e.g., El Haibi et al, 2020; El Houicha et al, 2018; Ouabid et al, 2017; Pereira et al, 2014, 2015; Tahiri et al, 2010) has not been reported in the Eastern Moroccan Meseta. Thus, the oldest sedimentary rocks described in this latter region are shales and schists attributed to the Cambrian–Ordovician in the Midelt Massif by correlation with similar facies in the Western Moroccan Meseta (Hoepffner, 1989).…”

Syn-collisional detrital zircon source evolution in the northern Moroccan Variscides

“…The igneous Precambrian basement of the northern Moroccan Variscides crops out in the WMM in relatively small and isolated areas of the Central Zone and Coastal Block (e.g. El Haibi et al, 2020;El Houicha et al, 2018;Ouabid et al, 2017;Pereira et al, 2014Pereira et al, , 2015Tahiri et al, 2010). This basement is covered by a thick, more or less continuous, passive margin succession that is exposed in large areas of the WMM, and in more scarce and relatively small inliers of the EMM (Figure 1).…”

Integrated multi-proxy source-to-sink analysis of the Lower Cretaceous of the Essaouira-Agadir Basin.

“…The oldest rocks of the WAC are Archean in age, found within the Man-Leo and Reguibat Shields, which record crustal growth from 3.5-3.0 Ga as part of the Leonian and Liberian orogenic cycles (Potrel et al, 2007). The next major period of zircon formation was during the Paleoproterozoic Eburnean-Birimian orogeny, which impacted the Reguibat Shield and formed the basement of the Anti-Atlas mobile belt (Boher et al, 1992;Gasquet et al, 2008) and the Moroccan Meseta (El Houicha et al, 2018).…”