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Géologie, géochimie et géochronologie du gisement aurifère de Tamlalt-Menhouhou (Haut-Atlas oriental)

Abstract : Because of its particular location at the edge of the West African Craton, Morocco has experienced a complex geodynamic history, starting in the Palaeoproterozoic and continuing until the most recent alpine events. This polyphase history resulted in the formation of mineralizations that overlap in time and space. The Tamlalt-Menhouhou gold deposit is located on the southern edge of the Neoprotérozoic-Palaeozoic Tamlalt inlier (Eastern High- Atlas), just north of the limit between the Atlasic intra-cratonic High-Atlas belt and the Panafrican Anti-Atlas belt. Mineralizations are enclosed in Ediacaran volcano-sedimentary formations (U/Pb age: 569 ± 8 Ma) which were probably produced in a back-arc basin. The Neoproterozoic felsic rocks reveal the fertile character of the Upper Neoproterozoc crust and include both barite mineralization and an iron-bearing mineralization that can be described as a “Banded Iron Formation”. The Tamlalt-Menhouhou gold deposit is crosscut by many shear faults compatible with a dextral shearing phase. Two different gold mineralizations were identified: (i) a primary gold mineralization of the type “Iron Oxide Copper Gold deposit” (IOCG) characterized by a strong sodic (± calcic) alteration and (ii) a secondary gold mineralization corresponding to a “Shear zone related gold deposit” and related to a strong argillic and phyllic alteration localized along the shear faults. A detailed ion microprobe study of hydrothermal zircons genetically associated with albitization provide a Late Ordovician age (449 ± 8 Ma) for primary gold mineralization. This age is confirmed by 40Ar/39Ar dating of two muscovite mono-grains, which underscores the potential of zircons to record hydrothermal events, and the interest of these phases for metallogeny. A Late Variscan age (293 ± 7 Ma) is defined by 40Ar/39Ar analysis of phengites from the phyllic alteration synchronous with auriferous quartz vein development, and which is assumed to represent the age of gold mineralization. This age is in agreement with the Late Variscan dextral shearing phase, and demonstrates the consequences of the Variscan orogeny for the re-mobilization of metalliferous pre-concentrations.
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Contributor : Ewan Pelleter <>
Submitted on : Wednesday, November 28, 2007 - 12:13:24 AM
Last modification on : Thursday, February 25, 2021 - 9:46:09 AM
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  • HAL Id : tel-00192430, version 1

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Ewan Pelleter. Géologie, géochimie et géochronologie du gisement aurifère de Tamlalt-Menhouhou (Haut-Atlas oriental). Géologie appliquée. Institut National Polytechnique de Lorraine - INPL, 2007. Français. ⟨tel-00192430⟩

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