The Ediacaran volcanic rocks and associated mafic dykes of the Ouarzazate Group (Anti-Atlas, Morocco): Clinopyroxene composition, whole-rock geochemistry and Sr-Nd isotopes constraints from the Ouzellarh-Siroua salient (Tifnoute valley)

Belkacim, Said; Gasquet, Dominique; Liégeois, Jean-Paul; Arai, Shoji; Gahlan, Hisham A.; Ahmed, Hassan S.; Ishida, Yoshito; Ikenne, Moha

doi:10.1016/j.jafrearsci.2016.08.002

Cited by 28 publications

(8 citation statements)

References 43 publications

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“…As for ignimbrites, tuffs with andesitic to rhyolitic composition are widespread through the Imiter sequence. Geochemically, all pyroclastic rocks at Igoudrane mine are characterized by a medium-to high-K calcalkaline, peraluminous signature, in accordance with other reported areas of the Anti-Atlas system [50].…”

Section: Volcanic and Volcaniclastic Rockssupporting

confidence: 88%

“…Neoproterozoic marine carbonates compositional field is from [69]. 87 Sr/ 86 Sr isotopic ratios for rhyolite and dacite are from [50]. Assuming an overall average temperature of 250 °C as inferred from fluid inclusion data and fahlore thermochemistry (Figure 13), the calculated oxygen isotope compositions of the ore-forming fluids (δ 18 O f V-SMOW) using the calcite-H2O fractionation factor of [67,68] range from 1.2 to 12.3‰; most are between 5 and 10‰.…”

Section: Figure 12mentioning

confidence: 99%

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Mineralogy, Fluid Inclusion, and C-O-Sr Isotope Geochemistry to Unravel the Evolution of the Magmatic-Hydrothermal System at the Igoudrane Silver-Rich Deposit (Imiter District, Eastern Anti-Atlas, Morocco)

Diallo¹,

Bouabdellah²,

Levresse

et al. 2021

Minerals

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The Igoudrane mine with a total production of 700,000 t of ore grading 485 g/t Ag is currently one of the most productive mines in the Imiter district of the eastern Anti-Atlas in Morocco. The silver-rich ± base metal deposit occurs dominantly as vein- and hydrothermal breccia-hosted orebodies at the interface between the lower Ediacaran turbidites of the Saghro Group and the unconformably overlying, dominantly felsic volcanic, and volcaniclastic rocks of the late Ediacaran Ouarzazate Group. Higher-grade ores are lithologically hosted by the uppermost organic-rich black shale unit and structurally controlled by the intersection of subvertical NW- and NE-trending fault systems. Ore-related hydrothermal alteration includes, in order of decreasing abundance, carbonatization, silicification, sericitization, and chloritization. Three primary paragenetic stages of veining and associated silver ± base metal mineralization have been recognized: (1) early pyrite + quartz + Ag-bearing sulfides and sulfosalts; (2) main Ag-bearing sulfides and sulfosalts + calcite ± fluorite ± dolomite; and (3) late quartz + calcite + base-metal sulfides (galena, sphalerite, pyrite, chalcopyrite). Irrespective of the ore stage, the dominant Ag-bearing ore minerals are Ag-Hg amalgam, argentite, freibergite, acanthite, polybasite, pyrargyrite, and proustite. Fluid inclusion data show a trend of decreasing temperatures with time, from the main silver stage (Th = 180 ± 12 °C) to late base-metal stage (Th = 146 ± 7 °C), consistent with fluid mixing, cooling, and/or dilution. The coexistence of aqueous-rich and vapor-rich fluid inclusions together with variations in bulk salinity (NaCl + CaCl2) of the mineralizing fluids during the main silver stage, at similar temperatures, indicate that boiling and subsequent degassing occurred during the main ore-forming event due to a pressure decrease. Calculated δ18Ofluid values along with REE+Y and Sr isotope constraints suggest that the ore-forming fluids originated from a predominantly magmatic source, although incursion of meteoric waters during collapse of the hydrothermal system could have contributed to deposition. The post-ore, base-metal quartz-carbonate-dominated mineralization was deposited from dilute Ca-Na-Cl-bearing fluids at temperature below 150 °C. Overall, fluid–rock interaction with the black shales along major faults and thin permeable horizons, boiling-degassing—with subsequent fluid mixing, cooling, and/or dilution—were the main mechanisms of silver deposition.

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Section: Volcanic and Volcaniclastic Rockssupporting

confidence: 88%

Section: Figure 12mentioning

confidence: 99%

Mineralogy, Fluid Inclusion, and C-O-Sr Isotope Geochemistry to Unravel the Evolution of the Magmatic-Hydrothermal System at the Igoudrane Silver-Rich Deposit (Imiter District, Eastern Anti-Atlas, Morocco)

Diallo¹,

Bouabdellah²,

Levresse

et al. 2021

Minerals

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“…It is located in the central zone of the Anti-Atlas and belongs to the Pan-African Neoproterozoic domain. It is made up of a Pan-African basement and Upper to Terminal Neoproterozoic volcanic cover, as well as a much more recent Cretaceous and Neogene cover (Belkacim et al 2017). This massif is cut to the south by the Anti-Atlas Major Fault (AAMF) (Choubert 1947) (Fig.…”

Section: In the Eastmentioning

confidence: 99%

Mapping soil erosion–prone sites through GIS and remote sensing for the Tifnout Askaoun watershed, southern Morocco

et al. 2021

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The Moroccan High Atlas is very sensitive to soil erosion due to its steep slopes, torrential rains, and degraded plant cover. The degradation of fertile soils in this mountainous watershed influences negatively upon agricultural productivity. The objective of this study is to quantify soil erosion in the Tifnout Askaoun watershed in southern Morocco. The Revised Universal Soil Loss Equation (RUSLE), the geographic information system (GIS) techniques, and the Tropical Rainfall Measuring Mission (TRMM) data were adopted for mapping the annual rate of soil loss in this watershed area of around 1488 km 2 . The spatial distribution of annual soil erosion rates was obtained by integrating the geo-environmental variables into a GIS. These variables are the rainfall erosivity (R) generated from the TRMM data, the soil erodibility factor (K), the length and slope inclination (LS), the vegetation and management factor (C), and the practice support factor (P). Results reveal an average annual soil erosion rate of 14.44 t/ha/year and a good correlation with the slope length and steepness factor (r = 0.72) and in a lesser extent with the rainfall erosivity factor (r = 0.63). The sub-catchments of the study area were mapped and grouped into five classes of vulnerability to soil erosion risk, with results indicating that the Toubkal sub-catchment is the most threatened by water erosion risk as reflected by an average erosion rate of 48.05 t/ha/year. Approaches and results from this study, which was conducted between 2017 and 2019, may benefit researchers and decision-makers concerned with soil management primarily in mountainous areas where soil degradation impacts the activities of the rural population.

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“…The different behaviours of the Ediacaran vs Cryogenian-Tonian zircons can be related to the contrasted terranes present in the Pan-African belts around the WAC, i.e. the Trans-Saharan belt (Liégeois et al, 1998(Liégeois et al, , 2003Fezaa et al, 2010), the Anti-Atlas belt (Ennih and Liégeois, 2008;Toummite et al, 2013;Belkacim et al, 2017), the Souttouf massif (Gärtner et al, 2016), the Bassarides and the Rockelides (Villeneuve et al, 2010(Villeneuve et al, , 2015. In these terranes, the juvenile Cryogenian and in a much lesser amount Tonian island arc terranes have been generated before the ocean closures (> 630 Ma), while the 630-545 Ma period corresponds to collision and post-collision events with large amounts of high-K calc-alkaline magmatism (Liégeois et al, 1998).…”

Section: U-pb Ages Of Magmatic Rocks and Comparison With The Brabant Massifmentioning

confidence: 99%

“…Such a situation could be imaged by the late Ediacaran Ouarzazate volcanic province in the Moroccan Anti-Atlas, which is very large (80 x 600 km), mostly felsic and potassic in composition, that lasted 60 Myr and which emplaced along the northern boundary of the West African craton (e.g. Ennih and Liégeois, 2008;Gasquet et al, 2008;Belkacim et al, 2017). Another example is the Early Cretaceous bimodal (basalts and rhyolites) Parana Province associated with the opening of the South Atlantic Ocean, which is very large with a preserved surface of > 1.2 million km 2 and an average thickness of 0.7 km (Peate, 1997 and references therein).…”

Section: The Bimodal Magmatismmentioning

confidence: 99%

The Stavelot-Venn Massif (Ardenne, Belgium), a rift shoulder basin ripped off the West African craton: Cartography, stratigraphy, sedimentology, new U-Pb on zircon ages, geochemistry and Nd isotopes evidence

Herbosch

Liégeois

Gärtner

et al. 2020

Earth-Science Reviews

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The Ediacaran volcanic rocks and associated mafic dykes of the Ouarzazate Group (Anti-Atlas, Morocco): Clinopyroxene composition, whole-rock geochemistry and Sr-Nd isotopes constraints from the Ouzellarh-Siroua salient (Tifnoute valley)

Cited by 28 publications

References 43 publications

Mineralogy, Fluid Inclusion, and C-O-Sr Isotope Geochemistry to Unravel the Evolution of the Magmatic-Hydrothermal System at the Igoudrane Silver-Rich Deposit (Imiter District, Eastern Anti-Atlas, Morocco)

Mineralogy, Fluid Inclusion, and C-O-Sr Isotope Geochemistry to Unravel the Evolution of the Magmatic-Hydrothermal System at the Igoudrane Silver-Rich Deposit (Imiter District, Eastern Anti-Atlas, Morocco)

Mapping soil erosion–prone sites through GIS and remote sensing for the Tifnout Askaoun watershed, southern Morocco

The Stavelot-Venn Massif (Ardenne, Belgium), a rift shoulder basin ripped off the West African craton: Cartography, stratigraphy, sedimentology, new U-Pb on zircon ages, geochemistry and Nd isotopes evidence

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