The magmatic evolution at the Moroccan outboard of the West African craton between the Late Neoproterozoic and the Early Palaeozoic

Abstract

The Late Neoproterozoic Ouarzazate Group crops out on the north margin of the West African craton (WAC). In this group an important post-collisional magmatism is characterized by a great diversity in plutonic and volcanic rock types of the high-K calc-alkaline series. This series evolved mainly by crystal fractionation and by an important crustal contamination from an anomalous mantle source. The Early Cambrian magmatism began at the same time on both sides of the Anti-Atlas Major Fault, the southwestern side (Kerdous region) and northeastern side (Ouarzazate-Agdz region), interbedded in the Early Cambrian Basal Series and spread later to the Western High Atlas of the Morocco northern WAC outboard areas. This magmatism changes from a continental tholeiitic series (HPT and LPT) at the beginning to an alkaline series at the top (Adoudou and ‘Lie de vin’ formations). Fractional crystallization and pelagic or crustal contamination were the most important processes in the magma differentiation. The geochemical inversion from calc-alkaline to tholeiitic magmatism between the Late Neoproterozoic and the Early Cambrian is documented, as is the major extension of the tholeiitic activity on both sides of the South Atlas Fault. This geochemical variation indicates a transition of the tectonic regime from compressive to extensional. The late local Jbel Boho alkaline magmatism indicates the sink of the source and the mitigation or closure of the extensional cycle at this time.

Re/Os Age Determination, Lead and Sulphur Isotope Constraints on the Origin of the Bouskour Cu–Pb–Zn Vein-Type Deposit (Eastern Anti-Atlas, Morocco) and Its Relationship to Neoproterozoic Granitic Magmatism

“…The geology of the Bouskour district has been summarized by Tixeront (1971), Clavel and Tixeront (1971), Ezzouhairi (1989Ezzouhairi ( , 1997Ezzouhairi ( , 2001), Ezzouhairi et al (2008), and Walsh et al (2008). The following description summarizes work by these authors supplemented by our own observations.…”

“…The granodiorite is equigranular in the central part of the pluton, grading to a porphyritic amphibole-bearing granodiorite along the margins. Based on whole-rock and radiogenic isotope geochemistry, the Bouskour intrusion is a high-K, calc-alkaline granodiorite of island-arc affinity, having a mantle derivation with negligible crustal contamination (Ezzouhairi et al 2008). Intrusion of the granodiorite produced a 300-m-wide contact metamorphic aureole of massive hornfels comprising biotite, cordierite, and andalusite.…”

Interplay of phosphogenesis and hydrothermalism in the latest Ediacaran rift of the High Atlas, Morocco

“…During deposition of the Tabia Member, some grabens dropped down significantly relative to adjacent uplifts and inherited inliers, and slope-related and alluvial sediments accumulated to great thickness in the troughs (Piqué et al, 1999;Algouti et al, 2000;Benssaou and Hamoumi, 2001;Soulaimani et al, 2001Soulaimani et al, , 2003Pouclet et al, 2007). Meanwhile, dike intrusion and local volcanic (tholeiitic) eruptions took place within the rift valleys (Álvaro et al, 2008a;Ezzouhairi et al, 2008). In contrast, the carbonate-dominated Tifnout Member represents a more stable, peritidal platform, wholly colonized by microbial communities.…”

“…The Ouarzazate volcanic episodes consist of basaltic andesites and andesites evolving to dacites and rhyolites and exhibit a calc-alkaline magmatic signature (Pouclet et al, 2007;Ezzouhairi et al, 2008). The overlying basalts display a drastically different signature of continental tholeiites, as well as the interbedded lavas of the subsequent Cambrian episodes, which evolved to alkaline magmatic compositions, with decreasing degrees of partial melting.…”

Late Ediacaran syn‐rift/post‐rift transition and related fault‐driven hydrothermal systems in the Anti‐Atlas Mountains, Morocco

“…). During deposition of the Tabia Member, some grabens dropped down significantly relative to adjacent uplifts and inherited Proterozoic inliers, and slope‐related, alluvial and fluvial sediments accumulated to great thickness in the troughs (Piqué et al ., , ; Algouti et al ., ; Soulaimani et al ., , ; Pouclet et al ., ); meanwhile, dike intrusion and local volcanic eruptions took place within the rift valleys (Álvaro et al ., ; Ezzouhairi et al ., ). As pointed out by Maloof et al .…”