Geology and Mineralogy of the Hercynian Koudiat Aicha Polymetallic (Zn-Pb-Cu) Massive Sulfide Deposit, Central Jebilet, Morocco

Lotfi, Fouad; Belkabir, Abdelhay; Brown, Alexandra; Marcoux, Éric; Brunet, S.; Maacha, Lhou

doi:10.2113/gsemg.17.3-4.145

Cited by 11 publications

(33 citation statements)

References 23 publications

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“…The gabbros with a tholeiitic affinity (both below and above mineralization) preceded metamorphism and deformation, and imply a magmatic heat source for the hydrothermal ore system (Lotfi et al, 2008). The hydrothermal envelope surrounding the deposit is asymmetric from the footwall up to the hanging wall.…”

Section: Discussionmentioning

confidence: 98%

“…The hydrothermal fluids (magmatic and possibly meteoric) circulating through the volcano-sedimentary sequences would have been enriched in Fe, Mg and associated base metals leached from the predominantly sedimentary footwall. These fluids precipitated chlorite and sulphides, with sulphur derived from the reduction of biogenic marine sulphates (Lotfi et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…From its projected extensions at depth, the sulphide mineralization is seen to be located on the eastern flank of a P 1 anticline dipping steeply to the east (Lotfi et al, 2008), and to be formed mainly of N-S trending pyrrhotitic lenses measuring decameters in length and metres in thickness. Sulphide lenses generally increase in size with depth and may attain widths of 20-25 m (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The argillites are intercalated with siltstone and sandstone layers and with minor rhyodacite lava flows and tuffs, all of which are cut by gabbroic dikes and sills (10-15%). The principal lithofacies and their petrographic descriptions are presented in Table 1, as well as in Lotfi et al (2008). All lithologies have undergone greenschist-facies metamorphism, resulting in the formation of abundant sericite, chlorite (ripidolite to pycnochlorite), quartz and epidote.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…As described by Lotfi et al (2008), the sulphide mineralization consists principally of several lenses of massive to semi-massive pyrrhotite, 1-20 m in thickness, enclosed by a large halo of asymmetrically disseminated sulphides. The ore sulphides are pyrrhotite, along with lesser amounts of sphalerite, chalcopyrite, arsenopyrite, galena, pyrite and stannite.…”

Section: Introductionmentioning

confidence: 99%

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Lithogeochemical, mineralogical analyses and oxygen–hydrogen isotopes of the Hercynian Koudiat Aïcha massive sulphide deposit, Morocco

Lotfi

Belkabir

Brunet

et al. 2010

Journal of African Earth Sciences

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Koudiat Aïcha is a Visean stratiform, volcanogenic massive sulphide (VMS) zinc-copperlead deposit, situated northwest of Marrakech, within the Central Domain of the Jebilet massif of the Western Moroccan Meseta. The Central Domain is formed mainly of sedimentary (argillite, siltstone, sandstone, carbonate) and magmatic (gabbro and rhyodacite) rocks that host numerous massive sulphide deposits (e.g., Koudiat Aïcha, Kettara and Draa Sfar) in a thick grayish argillite sequence (rhythmic metapelite). The deposit is stratabound and consists of highly deformed, sheet-like lenses of massive sulphide located structurally on the eastern flank of a large anticline. Prior to metamorphism, the country rocks were subjected to hydrothermal alteration which is particularly pronounced in the immediate vicinity of the sulphide deposits where chloritization and sericitization are prevalent. Hydrothermal alteration extends into both the stratigraphic footwall and the stratigraphic hanging wall. The footwall lacks an obvious pipe zone (sulphide stringers or vent complex) beneath the sulphide mineralization, but is characterized by an increase in the modal proportion of Mg-chlorite and by the breakdown of feldspar and sericite. Chloritization, the most extensive and readily recognizable alteration useful in mineral exploration, is evident for more than 60 m above the subcropping sulphide deposits. The hanging wall rocks show a pervasive sericitization (over 30 m wide) and a weak chlorite alteration accompanied by disseminated nodules of pyrrhotite stretched parallel to the S 1 foliation. Because chlorite and sericite are metamorphic minerals that also occur in unaltered rocks surrounding the sulphide deposits, abundant Mg-rich chlorite and the absence of feldspar in the footwall are used to distinguish hydrothermal alteration facies from metamorphic facies. The chlorite geothermometer reveals temperatures between 250 and 330 °C. Higher temperatures (up to 300 °C) are associated with chlorite located in and adjacent to sulphide mineralization, whereas lower temperatures correlate with distal chlorite in both the footwall and hanging wall rocks.Chemical trends in altered footwall rocks are shown by absolute mass gains for Fe 2 O 3total , MnO and MgO, by absolute mass losses for CaO, K 2 O and Na 2 O, and by a moderate loss in SiO 2 . Oxygen and hydrogen isotope compositions of Koudiat Aïcha lithofacies (6.2-12.4‰ for oxygen and −51‰ to −36‰ for hydrogen) have also been used to determine the temperature and origin of metalliferous fluids. The couple plagioclase-amphibole of gabbros provides equilibrium temperatures between 310 and 380 °C and suggests that the heat source for the ore-forming fluid system may have been igneous. On the other hand, oxygen and hydrogen isotope ratios cluster between normal values for sedimentary and magmatic rocks, suggesting a magmatic-metamorphic origin for the ore fluid.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lithogeochemical, mineralogical analyses and oxygen–hydrogen isotopes of the Hercynian Koudiat Aïcha massive sulphide deposit, Morocco

Lotfi

Belkabir

Brunet

et al. 2010

Journal of African Earth Sciences

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Geologic, Hydrothermal, and Geochemical Relationships Between Bimodal Magmatism and Massive Sulphide Mineralization in the Central Jebilet-Guemassa Province (Western Moroccan Hercynides)

Bouabdellah

Hibti²,

Maacha³

et al. 2016

Mineral Deposits of North Africa

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The Jebilet-Guemassa volcanic-hosted massive sulphide (VHMS) province comprises four sheet-like, polymetallic deposits. These are referred to as Kettara (>20 Mt at 0.6 % Cu with traces of Pb and Zn), Hajar (*20 Mt at 10.5 % Zn, 3.2 % Pb, 0.6 % Cu, and 60 g/t Ag), Draa Sfar (*11 Mt at 5.9 % Zn, 2.2 % Pb, and 0.3 % Cu), and Koudiat Aicha (3-5 Mt at 3 % Zn, 1 % Pb, and 0.6 % Cu), which collectively total >80 Mt of Pb-Zn-Cu ore. Host rocks consist predominantly of variably altered, mafic to felsic, submarine volcanic and tuffaceous volcaniclastic rocks within the metasedimentary Visean Sarhlef Series composed of black argillite with interbedded carbonate, siltstone, and sandstone. Hydrothermal alteration is distinctly asymmetric, occurring regionally in rocks of the stratigraphic footwall, immediate footwall, and hanging wall. In order of decreasing abundance, alteration assemblages consist of varying proportions of sericite, chlorite, quartz, carbonates (calcite, siderite, ankerite, and dolomite), talc, and epidote, with minor albite and tremolite-actinolite. These assemblages were controlled mainly by temperature and pH of the hydrothermal fluids. Mass-balance calculations indicate that hydrothermal alteration of the footwall rocks was accompanied by pervasive leaching of K 2 O, Na 2 O, and CaO, moderate loss of SiO 2 , and addition of FeO, MgO, and MnO under a high-temperature (>150°C) regime and high water/rock ratios (>10). In contrast, sericite-and calcite-rich alteration of hanging wall rocks involved lower temperatures (<150°C) and water-rock ratios of <5. Sulphide ores are dominated by pyrrhotite with variable proportions of sphalerite, chalcopyrite, galena, and pyrite ± tetrahedrite ± arsenopyrite ± marcasite ± bismuthinite ± cassiterite ± stannite ± cobaltite ± cubanite ± electrum. Overall, the ore and host rocks were strongly deformed, foliated, and mylonitized under greenschist-facies metamorphic conditions. Lithogeochemistry, alteration mineralogy, mineral chemistry, fluid inclusion data, and stable and radiogenic isotope constraints indicate that the Jebilet-Guemassa VHMS deposits formed in the Upper Visean (*330 Ma) from an evolving hydrothermal system that was initiated by regional-scale convection of magmatic-hydrothermal fluids and ambient seawater. Compared to classical VHMS systems, the Jebilet-Guemassa deposits possess a number of distinctive attributes that set them apart. These include (1) a banded sheet-like morphology, (2) predominance of pyrrhotite (up to 90 vol.%) over pyrite, (2) lack of well-developed stockwork zones, (4) absence of barite, (5) high Zn/Cu ratio, and (6) volumetrically minor igneous rocks.

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Black shales and massive sulfide deposits: causal or casual relationships? Insights from Rammelsberg, Tharsis, and Draa Sfar

et al. 2010

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Geology and Mineralogy of the Hercynian Koudiat Aicha Polymetallic (Zn-Pb-Cu) Massive Sulfide Deposit, Central Jebilet, Morocco

Cited by 11 publications

References 23 publications

Lithogeochemical, mineralogical analyses and oxygen–hydrogen isotopes of the Hercynian Koudiat Aïcha massive sulphide deposit, Morocco

Lithogeochemical, mineralogical analyses and oxygen–hydrogen isotopes of the Hercynian Koudiat Aïcha massive sulphide deposit, Morocco

Geologic, Hydrothermal, and Geochemical Relationships Between Bimodal Magmatism and Massive Sulphide Mineralization in the Central Jebilet-Guemassa Province (Western Moroccan Hercynides)

Black shales and massive sulfide deposits: causal or casual relationships? Insights from Rammelsberg, Tharsis, and Draa Sfar

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