Mineralium Deposita

, Volume 51, Issue 1, pp 13–23 | Cite as

Detailed mineralogy and petrology of manganese oxyhydroxide deposits of the Imini district (Morocco)

  • A. Dekoninck
  • A. Bernard
  • J. Barbarand
  • B. Saint-Bezar
  • Y. Missenard
  • R. Lepretre
  • O. Saddiqi
  • J. Yans


Manganese ore in the Cenomanian-Turonian dolostone of the Imini district (south of the High Atlas, Morocco) displays a high Mn content due to the occurrence of pyrolusite, cryptomelane, hollandite sensu stricto, coronadite, romanechite, and lithiophorite. The orebodies occur mainly as three stratabound layers along the ~25-km-long ore belt following a WSW-ENE direction. Using scanning electron microscopy (SEM-EDS) coupled with X-ray diffraction (XRD), we here refine the mineralogy and petrology of Mn oxides and oxyhydroxides in order to constrain the paragenetic sequence and define the main processes of ore formation. Deposition and concentration of Mn oxyhydroxides follow a two-step sequence after dolomitization: (1) replacement of dolomite fabric (dolomite micrite and dolomite rhombs) by hollandite group minerals leading to a textural conservation and then (2) neoformation of collomorphous aggregates in an opened and brecciated system. These observations are consistent with a multistage evolution including multiple reworking and brecciation. Pyrolusite is the main Mn oxide observed in the Imini district during both early and late stages. The superficial environment provides supergene conditions suitable for the deposition of only Mn oxyhydroxides. This supergene environment and the occurrence of multiple bands of hollandite group minerals indicate an external migration (allochthonous supply) of Mn and associated elements, contemporaneous to an in situ chemical and mechanical dissolution of the host dolostone. The lithological heterogeneities of dolostone and its chemical environment compared to less permeable surrounding rocks may have provided the conditions to concentrate Mn oxides and oxyhydroxides.


Imini Manganese deposits Weathering Cretaceous dolostone Hollandite group minerals 



We thank the IMINI mine and the Société Anonyme Chérifienne d’Études Minières (SACEM) for giving the field authorizations and advice on the location of sampling sites. Thanks are due to two anonymous reviewers who greatly improved this manuscript as well as A. Cheilletz and B. Lehmann for their careful editing.


  1. Beaudoin B, Lesavre A, Pélissonnier H (1976) Action des eaux superficielles dans le gisement de manganèse d’Imini (Maroc). Bull Soc Geol Fr 18:95–100CrossRefGoogle Scholar
  2. Bouladon J, Jouravsky G (1952) Géologie des Gîtes minéraux marocains. Notes Mém Serv Géol Maroc 87:44–80Google Scholar
  3. Crerar D, Cormick R, Barnes H (1980) Geochemistry of manganese: an overview. Geol Geochem Manganese 1:63–77Google Scholar
  4. Decrée S, Deloule E, Ruffet G, Dewaele S, Mees F, Marignac C, Yans J, De Putter T (2010a) Geodynamic and climate controls in the formation of Mio-Pliocene world-class oxidized cobalt and manganese ores in Katanga province, DR Congo. Mineral Deposita 45:621–629CrossRefGoogle Scholar
  5. Decrée S, Ruffet G, De Putter T, Baele JM, Recourt P, Jamoussi F, Yans J (2010b) Complex Mn oxides in the Tamra iron mine: Ar-Ar geochronology and efficient traps for metal pollutants in a Fe-Pb-Zn mine environment. J Afr Earth Sci 57:249–261CrossRefGoogle Scholar
  6. Force E, Back W, Spiker E, Knauth L (1986) A ground-water mixing model for the origin of the Imini manganese deposit (Cretaceous) of Morocco. Econ Geol 81:65–79CrossRefGoogle Scholar
  7. Frizon de Lamotte D, Saint-Bézar B, Bracène R, Mercier E (2000) The two main steps of the Atlas building and geodynamics of the western Mediterranean. Tectonics 19:740–761CrossRefGoogle Scholar
  8. Frizon de Lamotte D, Leturmy P, Missenard Y, Khomsi S, Ruiz G, Saddiqi O, Guillocheau F, Michard A (2009) Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria, Morocco, Tunisia): an overview. Tectonophysics 475:9–28CrossRefGoogle Scholar
  9. Gaudefroy G (1960) Caractères distinctifs de la pyrolusite – ex manganite (application au minerai de l’Imini). Notes Serv Géol Marocain 19:77–86Google Scholar
  10. Gebert H (1989) Schichtgebundene Manganlagerstätten. Enke Verlag, StuttgartGoogle Scholar
  11. Gutzmer J, Beukes N, Rhalmi M, Mukhopadhyay J (2006) Cretaceous karstic cave-fill manganese-lead-barium deposits of Imini, Morocco. Econ Geol 101:385–405CrossRefGoogle Scholar
  12. Hem JD (1963) Chemical equilibria and rates of manganese oxidation. US Government Printing Office, US Geological SurveyGoogle Scholar
  13. Lalaoui MD (1987) Étude sédimentologique et métallogénique du gisement manganésifère de l’Imini. PhD Thesis (Unpubl.), Université de Marrakech, Marrakech, 159pGoogle Scholar
  14. Lalaoui MD, Beauchamp J, Sagon JP (1991) Le gisement de manganèse de l’Imini (Maroc): un dépôt sur la ligne de rivage. Chroniques Rech Min 502:23–36Google Scholar
  15. Lesavre A (1975) Le gisement de manganèse d’Imini (Maroc). PhD Thesis (Unpubl.), Université Pierre-et-Marie-Curie, Paris, 101pGoogle Scholar
  16. Neltner L (1933) Le manganèse dans les possessions françaises : Les Ressources Minérales de la France d’Outremer. Publ Bur d’Etudes Géol Min Coloniales 2:81–144Google Scholar
  17. Nicholson K (1992) Contrasting mineralogical-geochemical signatures of manganese oxides; guides to metallogenesis. Econ Geol 65:1253–1264CrossRefGoogle Scholar
  18. Orcel J (1942) La Coronadite et le minerai qui la renferme dans les gîtes de manganèse de l’Imini (Sud Marocain). Bull Soc Fr Minér 65:73–111Google Scholar
  19. Pokrovsky OS, Golubev SV, Schott J, Castillo A (2009) Calcite, dolomite and magnesite dissolution kinetics in aqueous solutions at acid to circumneutral pH, 25 to 150 °C and 1 to 55 atm pCO2: new constraints on CO2 sequestration in sedimentary basins. Chem Geol 265:20–32CrossRefGoogle Scholar
  20. Post JE (1999) Manganese oxides mineral: crystal structure, economic and environmental significance. Proc Natl Acad Sci U S A 96:3447–3454CrossRefGoogle Scholar
  21. Pouit G (1964) Les gîtes de manganèse marocains encaissés dans les Formations carbonatées : éléments pour une synthèse. Chron Min Rech Min 337:371–380Google Scholar
  22. Pouit G (1976) La concentration de manganèse de l’Imini (Maroc) peut-elle être d’origine karstique ? C R Somm Soc Géol France 5:227–229Google Scholar
  23. Pouit G (1980) Manganèse. Notes Mém Serv Géol Maroc 13:61–67Google Scholar
  24. Rhalmi M (1992) Les systèmes sédimentaires cénomano-turoniens et sénoniens de la région manganésifère d’Imini (Haut-Atlas Central, Maroc) et leur évolution diagénétique. PhD Thesis (Unpubl.) University Bourgogne, Dijon, 168pGoogle Scholar
  25. Rhalmi M, Pascal A, Lang J (1997) Contrôle sédimentaire et diagénétique de la minéralisation manganésifère au cours du Crétacé Supérieur dans la région d’Imini (Haut-Atlas central, Maroc). C R Acad Sci 324:213–220Google Scholar
  26. Rhalmi M, Pascal A, Chellai E (2000) Litho-biostratigraphie, diagenèse et paléogéographie au Cénomanien supérieur-Turonien inférieur des bassins sud-atlasiques marocains. Géol Alp 76:135–149Google Scholar
  27. Thein J (1990) Paleogeography and geochemistry of the “Cenomano-Turonian” formations in the manganese district of Imini (Morocco) and their relation to ore deposition. Ore Geol Rev 5:257–291CrossRefGoogle Scholar
  28. Turner S, Buseck PR (1979) Manganese oxide tunnel structures and their intergrowths. Science 203:456–458CrossRefGoogle Scholar
  29. Zouhri S, Kchikach A, Saddiqi O, El Haïmer FZ, Baidder L, Michard A (2008) The cretaceous-tertiary plateaus. In: Michard A et al (eds) Continental evolution: the geology of Morocco. Springer-Verlag, Berlin, pp 331–358CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Département de GéologieNaGRIDD, Université de NamurNamurBelgique
  2. 2.Département des Sciences de la Terre et de l’Environnement, Laboratoire de Minéralogie et Géochimie AppliquéeUniversité Libre de BruxellesBruxellesBelgique
  3. 3.Département des Sciences de la Terre, Relief et BassinUniversité Paris Sud, UMR CNRS-UPS 8148 IDESOrsayFrance
  4. 4.Laboratoire GéosciencesUniversité Hassan IICasablancaMaroc

Personalised recommendations