Geology and wall rock alteration at the Hercynian Draa Sfar Zn–Pb–Cu massive sulphide deposit, Morocco
Introduction
The newly opened (2005) Draa Sfar massive sulphide deposit, located in the southeastern margin of the Hercynian Jebilet massif, is one of two principal Zn producers in Morocco (Fig. 1). The Draa Sfar deposit is a sheet-like, massive sulphide deposit hosted within the Sarhlef series, a terrigeneous, sediment-dominated, volcano-sedimentary succession consisting of carbonaceous argillite, argillite, siltstone and sandstone with subordinate volcanic and volcaniclastic rocks (Huvelin, 1977). The massive sulphide deposit occurs near the top of an argillite–siltstone succession that conformably overlies a rhyodacite dome complex and associated volcaniclastic rocks and is conformably overlain by carbonaceous argillite. The Draa Sfar deposit is overturned, dips steeply to the east and faces west (Fig. 2). The massive sulphide deposit consists of two, highly deformed, sheet-like orebodies, Tazakourt and Sidi M'Barek, that combined have a total strike length of 1.5 km. Only Tazakourt has been developed and is currently in production. It has an average thickness of 20 m and an N–S strike length of 1 km (Fig. 2). Boudinage of the Tazakourt massive sulphide lens has resulted in several, en echelon, moderately north-plunging lenses.
In this paper we present the results from mapping, petrographic, mineralogical (X-ray diffraction), electron microprobe (EPMA) and geochemical studies of the sedimentary and volcanic lithofacies and alteration assemblages that host the Draa Sfar deposit. Our objectives are: (1) to provide the first reconstruction of the volcano-sedimentary environment in which the Draa Sfar deposit formed; (2) to describe the mineralogy, composition and distribution of hydrothermal alteration assemblages, particularly those that developed within the sedimentary lithofacies as they are only sparsely documented in the literature; and (3) to compare the pyrrhotite-rich Draa Sfar deposit to the more common and larger pyritic massive sulphide deposits of the Iberian Pyrite Belt, which share a similar age, sedimentary host rocks, and tectonic setting. This paper is complemented by a second contribution that focuses on the mineralogy, composition and origin of the sulphide ores at Draa Sfar (Marcoux et al., 2008).
Section snippets
Geological setting
The Draa Sfar mine is located along the southern margin of the Jebilet massif, in the southern part of the west Moroccan Meseta (Fig. 1a). The Jebilet massif, which extends for 170 km E–W and 40 km N–S, has been interpreted as a Devono-Carboniferous, intra-continental, rift basin (Huvelin, 1977, Beauchamp, 1984, Aarab and Beauchamp, 1987, Piqué and Michard, 1989, Beauchamp et al., 1991). The Jebilet massif consists of three lithotectonic domains, the western, central, and eastern domains (Fig. 1
Geology of the Draa Sfar deposit
The Central Jebilet succession has been subdivided into a lower volcano-sedimentary succession, the Sarhlef series and an upper sedimentary succession, the Teksim series (Huvelin, 1977, Bordonaro, 1983). The Draa Sfar deposit is located in the upper part of the Sarhlef series (Fig. 2, Fig. 3) and is underlain by more than 500 m of strata consisting of carbonaceous argillite, argillite, intercalated siltstone and a subordinate, but locally dominant coherent rhyodacite and associated
Geochemistry and hydrothermal alteration
One hundred and twenty-five drill core samples (7 cm in length) were collected from three representative drill holes, DS110, DS132, and DS125. These, plus fifteen surface samples were selected to provide coverage of the entire Draa Sfar deposit, its enclosing host rocks, and related hydrothermal alteration (Fig. 2). The drill core samples were powdered using an agate shatter box at the sample preparation laboratory, Marrakech—Cadi Ayyad University, Morocco.
Major elements (oxides), trace
Mineralogical characteristics and zonation
Alteration was examined using samples collected from outcrops and the three drill holes mentioned previously. Chemical, petrographic, microprobe, and X-ray diffractometry (XRD) analysis (Rietveld method) were performed on the samples (see Fig. 2; Supplementary Tables 1a,b and c). The principal minerals formed by hydrothermal alteration are chlorite and muscovite, with minor quartz and calcite. These minerals are also present in the least-altered volcanic and sedimentary rocks, but the
Discussion and conclusions
The dominance of more than 1 km of black, carbonaceous argillites within the footwall and hanging wall strata to the Draa Sfar deposit suggests that it formed within a restricted, sediment-starved, anoxic basin within the upper part of the Sarhlef Formation (e.g., Beauchamp et al., 1991). The argillites formed through background suspension sedimentation within the basin whereas the siltstones, which noticeably lack carbon, are distal turbidites that were derived from the basin margins. This
Acknowledgements
This research would not have been possible without the financial support of REMINEX. In particular we would like to thank Solange Brunet for her time, effort and guidance. Dr Andrew McDonald, MERC, Laurentian University, provided the excellent XRD analysis and modal analysis using the Rietveld method. Thorough and helpful reviews by Ore Geology Reviews reviewers Rodney Allen and Fernando Tornos and a subsequent review by Philips Thurston improved the manuscript. H.L Gibson gratefully
References (59)
Mechanism of deposition from pyroclastic flows
American Journal of Science
(1966)- et al.
Geochemistry and petrogenesis of Archean mafic volcanic rocks of the southern Abitibi belt, Québec
Precambrian Research
(1992) - et al.
Draa Sfar: a Hercynian pyrrhotite–Zn–Cu–Pb ore deposit in the Jebilet, Morocco. Mineralogy, geochemistry and deformation as constrains for a genetic model features
Ore Geology Reviews
(2008) Determination of REE, Ba, Fe, Mg, Na, and K in carbonaceous and ordinary chondrites
Geochimica et Cosmochimica Acta
(1974)- et al.
Geochemical discrimination of different magma series and their differentiation products using immobile elements
Chemical Geology
(1977) - Aarab, E.l., 1995. Genèse et differentiation d'un magma tholeitique en domaine extensif intracontinental: l'exemple du...
- et al.
Le magmatisme carbonifère pré-orogénique des Jebilet centrales (Maroc). Précisions pétrographiques et sédimentaires. Implications géodynamiques
Comptes Rendus de l'Académie des Sciences Paris (Série II)
(1987) - et al.
Mass changes in hydrothermal alteration zones associated with VMS deposits of the Noranda area
Exploration and Mining Geology
(1994) - et al.
Volcanic sequences, lithogeochemistry, and hydrothermal alteration in some bimodal volcanic-associated massive sulphide systems
Reviews in Economic Geology
(1999) Le Carbonifère inférieur des Jebilet et de l'Atlas de Marrakech (Maroc): Migration et comblement d'un bassin marin
Bulletin Société Géologique de France
(1984)
Les bassins d'avant-pays de la chaîne hercynienne au Carbonifère inférieur
Canadian Journal of Earth Sciences
Aperçu sur les amass sulfurés massifs des hercynides marocaines
Mineralium Deposita
Classification and genesis of submarine iron–manganese deposits
Tectonique et pétrographie du district à pyrrhotite de Kettara (Paléozoïque des Jebilet, Maroc)
Le géosynclinal carbonifère sud-mésétien dans les Jebilet (Maroc); une corrélation avec la province pyriteuse du sud de l'Espagne
Compte Rendus Académie Sciences Paris
The origin and fate of ferromanganoan active ridge sediments
Stockholm Contributions in Geology
Les minéralisations à sulfures massifs de la région de Marrakech, Maroc: contexte géologique et exploration
A chlorite solid solution geothermometer: the Los Azufres (Mexico) geothermal system
Contributions to Mineralogy and Petrology
Hydrothermal alteration, fluid flow and volume change in shear zones: the layered mafic–ultramafic Kettara intrusion (Jebilet Massif, Variscan belt, Morocco)
Journal of Metamorphic Geology
The behaviour of so-called immobile elements in hydrothermally altered rocks associated with volcanogenic submarine–exhalative ore deposits
Mineralium Deposita
Depositional model for shallow-marine manganese deposits around black-shale basins
Economic Geology
Volcanogenic massive sulphide deposits
Volcanic-associated massive sulphide deposits
Target vectoring using lithogeochemistry: applications to the exploration for volcanic-hosted massive sulphide deposits
Canadian Institute of Mining and Metallurgy Bulletin
The subsea-floor formation of volcanic-hosted massive sulphide: evidence from the Ansil deposit, Rouyn-Noranda, Canada
Economic Geology
Volcano-hosted ore deposits
The spectrum of volcano-sedimentary environments hosting volcanogenic massive sulphide deposits of the Visean, Jebilet and Guemassa Terrains, Morocco
Submarine volcanic processes, deposits and environments favourable for the location of volcanic-associated massive sulphide deposits
Reviews in Economic Geology
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2022, Applied GeochemistryCitation Excerpt :Furthermore, SWIR results confirm that the mica compositions show systematic trends from phengite muscovite in proximal zones to paragonitic muscovite in distal areas surrounding the main sericite zone at Bukit Botol. Similar relationships are recognized in other VHMS deposits like Prince Lyell (Hendry 1981), Hellyer (Yang 1998), Salgandinho (Plimer and Carvalho 1982), and Draa Sfar (Belkabir et al., 2008), but contrast with the observations at other VMS deposits, such as Myra Falls (Jones et al., 2005) and Western Tharsis (Huston and Kamprad, 2001; Herrmann et al., 2001; Gifkins et al., 2005). In addition, at Bukit Ketaya, minor pyropyhllite and kaolinite spectral profile was identified by SWIR from both alterations, as also supported by XRD data.
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2016, Journal of African Earth SciencesCitation Excerpt :The origin of the massive sulfide deposits is the subject of continuing debate. They have been variously considered as deformed syngenetic VMS or SEDEX bodies (Belkabir et al., 2008; Marcoux et al., 2008; Moreno et al., 2008; Lotfi et al., 2008) or as later syntectonic bodies (Essaifi and Hibti, 2008). The Kettara deposit is a pyrrhotite-rich, near-vertical massive sulfide lens located near the mafic-ultramafic Kettara intrusion.
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2015, Ore Geology ReviewsCitation Excerpt :The Draa Sfar deposit in the Jebilet Massif of western Morocco (Belkabir et al., 2008; Marcoux et al., 2008; Moreno et al., 2008) has many features in common with the Nicholas-Denys deposit. Its genetic classification has been the subject of much debate, and suggestions range from syngenetic (Belkabir et al., 2008; Bernard et al., 1988; Marcoux et al., 2008) to epigenetic (Essaifi and Hibti, 2008). The Draa Sfar deposit is thought to have formed in a volcano–sedimentary rift basin within anoxic sediments in an oxic–suboxic water column.
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2012, Journal of South American Earth SciencesCitation Excerpt :Al–OH wavelength distribution in the Arroyo Rojo deposit shows a sericitic alteration halo of phengitic composition surrounding the main mineralized lenses. The occurrence of phengite in the proximity of ore bodies has been described in other VMS deposits like Prince Lyell (Hendry, 1981), Hellyer (Yang, 1998), Salgandinho (Plimer and Carvalho, 1982), and Draa Sfar (Belkabir et al., 2008). Variations of chlorite Fe–OH bond absorption wavelength values in the deposit lie between 2231 and 2260 nm, corresponding to Mg in intermediate-Fe chlorite compositions (Pontual et al., 1997; Scott et al., 1998).