Tamlalt, Jbel Malek


Main commodities: Au
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The Tamlalt (Jbel Malek) gold deposit lies within the Neoproterozoic Palaeozoic Tamlalt inlier on the north-western margin of the West African craton, and is located in the Eastern High-Atlas of Morocco just north of the South Atlasic fault zone which separates the ENE trending High-Atlas and Anti-Atlas domains.

In the south-western part of the Tamlalt inlier, erosion of post-Palaeozoic and Palaeozoic cover has exposed two Upper Neoproterozoic exposures, the Tamlalt-Menhouhou and Bou Salem blocks, and the Ain Chair Middle Neoproterozoic inlier. These three areas, which define the Central Southern Domain of the Tamlalt inlier.

The Tamlalt-Menhouhou block, which hosts the Tamlalt gold deposit, comprise two Upper Neoproterozoic (569 ±8 Ma) bimodal volcanic and volcano-sedimentary units, which are from the base:
i) the mafic to intermediate volcano-sedimentary unit of mainly basaltic and andesitic flows, andesite meta-tuffites all of which are intruded by metagabbros,
ii) the felsic volcano-sedi-mentary unit, made up from the base of dacites and rhyodacite; rhyolitic meta-tuffites with rhyolitic ignimbrites and intercalated rhyolitic conglomerate layers; banded rhyolitic meta-tuffites with several interbedded polygenic conglomerate (containing abundant barite and BIF pebbles). In the western part of the block the upper part of this unit is only represented by discontinuous rhyodacite and rhyolite flows.

These Upper Neoproterozoic units are unconformably overlain by Lower Palaeozoic sedimentary units, namely a lower-most limestones and dolomites, followed by middle Cambrian sandy shales and quartzites.

In the Tamlalt deposit area the contact between the Upper Neoproterozoic and Palaeozoic is tectonic, represented by the El Hirech Shear. The deposit area is cut by numerous dextral shears.

Two different phases of gold mineralisation are recognised at Tamlalt-Menhouhou, namely:

i) a primary IOCG style characterised by strong sodic (± calcic) alteration, characterised by concentric halos of alteration, with a mineralised core of strong albitisation (albite ±hematite) overprinted by a calcic alteration (epidote, ankerite, calcite, chlorite), slight potassic alteration (phengite) and boron-silica alteration (tourmaline and quartz), and pyritisation; this is surrounded by an zone of quartz +albite ±muscovite ±carbonates. Several zones of the latter alteration type are distributed through a broader 2.5 km x up to 400 m wide, ENE elongated halo of quartz and/or carbonates ±albite ±hematite ±muscovite. Within the core, specular hematite is much more abundant than sulphides, some of which occurs as metre scale hematite breccia with >60% hematite. Low sulphide pyrite-chalcopyrite Cu-Au mineralisation occurs in the core, with a polymetallic association of Co, Ni, Mo, As, Sb, REE and Bi enrichment as tellurobismuthite, molybdenite, tennantite-tetrahedrite and monazite. Gold is found within the hematite breccias or as disseminated sulphides in albitized rocks, and rarely in quartz-pyrite veins.

ii) a secondary, 449 ±8 Ma orogenic shear zone hosted gold mineralisation accompanied by strong argillic and phyllic alteration represented by carbonates, chlorite, hematite, albite and pyrite. Visible free gold is related to goethite-malachite-barite boxworks in quartz veins. Numerous E-W to NE-SW dextral shears cross-cut the Upper Neoproterozoic rocks to form an anastomosed network reflected by numerous quartz veins and lenses (up to several metres thick) which are developed throughout the deposit area as parallel vein networks, stockworks or saddle reefs. The quartz veins are folded and in some places foliated reflecting the polyphase deformation. This second style of mineralisation comprises the bulk of the ore.

Preliminary drilling indicated an initial resource of 1 Mt @ 3.7 g/t Au at a 2 g/t cut-off, with significant potential for expansion.

The most recent source geological information used to prepare this summary was dated: 2007.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Pelleter E, Cheilletz A, Gasquet D, Mouttaqi A, Annich M, El Hakour A and Feraud G,  2008 - The Variscan Tamlalt–Menhouhou gold deposit, Eastern High-Atlas, Morocco: in    J. of African Earth Sciences   v50 pp 204-214
Pelleter E, Cheilletz A, Gasquet D, Mouttaqi A, Annich M, El Hakour A,  2010 - The Tamlalt-Menhouhou Polyphase Gold Deposit (High-Atlas, Morocco): IOCG-Type Mineralisation Overprinted by Shear-Zone Related Gold ?: in Porter T M, (Ed),  2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.4 pp. 535-552

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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