Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-13T08:45:01.295Z Has data issue: false hasContentIssue false
  • English
  • Français

Mineralogy, geochemistry and emplacement of the Conakry Igneous Complex, Guinea: implications for the Ni–Cu–PGE mineralization

Published online by Cambridge University Press:  15 April 2018

Thierry Augé ,
Éric Gloaguen ,
Matthieu Chevillard  and
Laurent Bailly
Thierry Augé
Affiliation:
Bureau de Recherches Géologiques et Minières (BRGM), BP 36009, 45060 Orléans cedex 2, France
Éric Gloaguen*
Affiliation:
Bureau de Recherches Géologiques et Minières (BRGM), BP 36009, 45060 Orléans cedex 2, France
Matthieu Chevillard
Affiliation:
Bureau de Recherches Géologiques et Minières (BRGM), BP 36009, 45060 Orléans cedex 2, France
Laurent Bailly
Affiliation:
Bureau de Recherches Géologiques et Minières (BRGM), BP 36009, 45060 Orléans cedex 2, France
*
*E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The Conakry Igneous Complex is a mafic-ultramafic intrusion emplaced contemporaneously with the opening of the Atlantic, forming a complex, 55 km x 5 km dyke-like body within which three main episodes of injection have been recognized, characterized by a lack of mineral layering. Unit 1 consists of dunite and related facies, Unit 2 of wehrlite and pyroxene peridotite and Unit 3 corresponds to various gabbro facies. Units 1 and 2 constitute the Kaloum Peninsula; Unit 3 is its NW extension, forming the 1010 m high Mount Kakoulima. Unit 3 intrudes the two previous units and corresponds to a tholeiitic liquid that crystallized in an almost closed system, and thus exhibits a strong differentiation trend, in contrast to Units 1 and 2. Mineral compositions suggest the existence of a deeper magma chamber where a first stage of differentiation occurred.

Disseminated base-metal sulfides (BMS) are present in all units of the complex and earlier descriptions have mentioned a “massive sulfide layer” with 2 to 4 g/t PGE. Platinum-group minerals (PGM) are almost everywhere included in or attached to composite Ni–Fe–Cu sulfides. Most PGM grains form complex associations resulting either from exsolution or alteration. It is characteristic of the Conakry Igneous Complex PGM, described here for the first time, to be dominated by (Pd,Pt)(Te,Bi) minerals with rare Pd,Sn and Pd,Pb compositions and an absence of Pt,Pd sulfides and Pt,Pd antimonides.

The constant association of the PGM with the BMS shows that the magmatic sulfide liquid acts as an efficient collector of PGE. In such a dynamic environment, the process leading to the formation of massive sulfides must be sought in the accumulation of sulfides in the conduit following host-rock assimilation. Accordingly, considering the multiple injection processes that characterize the whole intrusion, the potential for discovering additional Ni–Cu–PGE mineralization in the Conakry Igneous Complex remains high.

Keywords

Conakry Igneous ComplexGuineaplatinum-group elements
Type
Article
Information
Mineralogical Magazine , Volume 82 , Special Issue 3: Special Issue dedicated to the work and memory of Professor Hazel M. Prichard (1954–2017) , June 2018 , pp. 593 - 624
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2018 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

This paper is published as part of a thematic set in memory of Professor Hazel M. Prichard

Associate Editor: John Bowles

References

Augé, T., Genna, A., Legendre, O., Ivanov, K.S. and Volchenko, Y.A. (2005) Primary platinum mineralization in the Nizhny Tagil and Kachkanar ultramafic complexes, Urals, Russia: A genetic model for PGE concentration in chromite-rich zones. Economic Geology, 100, 707–732.Google Scholar
Augé, T., Morin, G., Bailly, L. and Serafimovsky, T. (2017) Platinum-group minerals and their host chromitites in Macedonian ophiolites. European Journal of Mineralogy, 29, 585–596.CrossRefGoogle Scholar
Barrère, J. (1959) La presqu’île du Kaloum et le massif du Kakoulima (République de Guinée). Notes du Service de Géologie et de Prospection Minière, Dakar, 2, 3–44.Google Scholar
Barrie, I., Wijbrans, J., Andriessen, P., Beunk, F., Strasser-King, V. and Fode, D. (2010) Combined 40Ar/39Ar and Fission-Track study of the Freetown Layered Igneous Complex, Freetown, Sierra Leone, West Africa: Implications for the Initial Break-up of Pangea to form the Central Atlantic Ocean and Insight into the Post-rift Evolution of the Sierra Leone Passive Margin. Geophysical Research Abstracts Vol. 12. EGU2010-7322-2, 2010, EGU General Assembly 2010.Google Scholar
Beckinsale, R.D., Bowles, J.F.W., Pankhurst, R.J. and Wells, M.K. (1977) Rubidium-strontium age studies and geochemistry of acid veins in the Freetown Complex, Sierra Leone. Mineralogical Magazine, 41, 501–511.CrossRefGoogle Scholar
Bering, D. (1998) Evaluation de l'Inventaire des Ressources Minérales de Guinée. BGR, Hannover, Germany, 109 pp.Google Scholar
Bertrand, H. (1991) The Mesozoic tholeiitic province of northwest Africa: A volcano-tectonic record of the early opening of Central Atlantic. Pp. 147–188 in: Magmatism in Extensional Structural Settings (Kampunzu, A.B. and R.T., Lubala, editors). Springer-Verlag.CrossRefGoogle Scholar
Bertrand, H. and Villeneuve, M. (1989) Records of the early Jurassic opening of the central Atlantic: the continental tholeiitic dolerites of Guinea (West Africa). Comptes Rendus Académie Sciences Paris, 308, 93–98.Google Scholar
Bessoles, B. (1977) Géologie de l'Afrique: le craton Ouest-Africain. Mémoires du BRGM Orleans, Vol. 88, France.Google Scholar
Boufeev, Y.B. (1968) Notice explicative de la carte géologique de la République de Guinée au 1/200 000. Service Géologique de Guinée, Conakry, Guinea, 182 pp.Google Scholar
Bowles, J.F.W. (1981) The distinctive suite of platinum-group minerals from Guma Water, Sierra Leone. Bulletin de Minéralogie, 104, 478–483.CrossRefGoogle Scholar
Bowles, J.F.W. (2000 a) Prassoite, vysotskite and keithconnite from the Freetown Layered Complex, Sierra Leone. Mineralogy and Petrology, 68, 75–84.CrossRefGoogle Scholar
Bowles, J.F.W. (2000 b) A primary platinum occurrence in the Freetown layered intrusion, Sierra Leone. Mineralium Deposita, 35, 583–586.CrossRefGoogle Scholar
Bowles, J.F.W., Prichard, H.M., Suarez, S. and Fisher, P.C. (2013) The first report of platinum-group minerals in magnetite-bearing gabbro, Freetown Layered Complex, Sierra Leone: occurrences and genesis. Canadian Mineralogist, 51, 455–473.CrossRefGoogle Scholar
Briden, J.C., Henthorn, D.I. and Rex, D.C. (1971) Palaeomagnetic and radiometric evidencefor the age of the Freetown igneous complex, Sierra Leone. Earth and Planetary Science Letters, 12, 385–391.CrossRefGoogle Scholar
Cabri, L.J. (2002) The platinum-group minerals. Pp. 13–129 in: The Geology, Geochemistry, Mineralogy and Mineral Beneficiation of Platinum-Group Elements (Cabri, L.J., editor). Canadian Institute of Mining, Metallurgy and Petroleum Special Vol. 54. Ottawa, Canada.Google Scholar
Chalokwu, C.I. (2001) Petrology of the Freetown layered complex, Sierra Leone; Part II, Magma evolution and crystallisation conditions. Journal of African Earth Sciences, 32, 519–540.CrossRefGoogle Scholar
Chalokwu, C.I. and Ghazi, A.M. (1995) REE Systematics of the Freetown layered complex of Sierra Leone: Implications for the heteradcumulus growth of Augite. EOS, Transactions AGU, 76, 296.Google Scholar
Chalokwu, C.I. and Seney, P.J. (1995) Open-system magma chamber process in the Freetown Complex of Sierra Leone: evidence from zone 3. Geological Magazine, 132, 261–266.CrossRefGoogle Scholar
Chalokwu, C.I., Ripley, E.M. and Park, Y. (1999) Oxygen isotopic systematics of an open-system magma chamber; an example from the Freetown layered complex of Sierra Leone. Geochimica et Cosmochimica Acta, 63, 675–685.CrossRefGoogle Scholar
Chalokwu, C.I., Seney, P.J., Wurie, C.A. and Bersch, M. (1995) Petrology of the Freetown layered complex, Sierra Leone; Part I, Stratigraphy and mineral-chemical evidence for multiple magma injection. International Geology Review, 37, 230–253.CrossRefGoogle Scholar
Chardon, D., Chevillotte, V., Beauvais, A., Grandin, G. and Boulangé, B. (2006) Planation, bauxites and epeirogeny: One or two paleosurfaces on the West African margin? Geomorphology, 82, 273–282.CrossRefGoogle Scholar
Dallmeyer, R.D., Caen-Vachette, M. and Villeneuve, M. (1987) Emplacement age of post-tectonic granites in southern Guinea (West Africa) and the peninsular Florida subsurface: Implications for origins of southern Appalachian exotic terranes. Geological Society of America Bulletin, 99, 87–93.2.0.CO;2>CrossRefGoogle Scholar
Dars, R. (1960) Les formations sédimentaires et les dolérites du Soudan occidental (Afrique de l'Ouest). Thèse de doctorat, Université de Paris, Paris.Google Scholar
Deckart, K., Féraud, G. and Bertrand, H. (1997) Age of Jurassic continental tholeiites of French Guyana, Surinam and Guinea: Implications for the initial opening of the Central Atlantic Ocean. Earth and Planetary Science Letters, 150, 205–220.CrossRefGoogle Scholar
Deckart, K., Bertrand, H. and Liégeois, J.P. (2005) Geochemistry and Sr, Nd, Pb isotopic composition of the Central Atalantic Magamatic Province (CAMP) in Guyana and Guinea. Lithos, 82, 289–314.CrossRefGoogle Scholar
Diallo, D., Bertrand, H., Azambre, B., Grégoire, M. and Caseiro, J. (1992) The mafic-ultramafic complex of Kakoulima (Guinea-Conakry): a tholeiitic layered intrusion related to the Central Atlantic rifting. Comptes Rendus Académie Sciences Paris, 314, 937–943.Google Scholar
Djon, M.L., Olivo, G.R., Miller, J.D., Peck, D.C. and Joy, B. (2017) Stratiform platinum-group element mineralization in the layered Northern Ultramafic Center of the Lac des Iles Intrusive Complex, Ontario, Canada. Ore Geology Reviews, 90, 697–722.CrossRefGoogle Scholar
Hattori, K. and Chalokwu, C.I. (1995) Source for early magmatism related to the opening of the Atlantic Ocean: Sr- and Nd- isotopes of mineral separates from the Freetown Complex of Sierra Leone. EOS, Transactions AGU, 76, 87.Google Scholar
Konaté, A.A. and Pan, H. (2013) Mount Kakoulima: An Overview and Analysis. Earth Science Research, 2, 23–33.Google Scholar
Lachassagne, P., Wyns, R. and Dewandel, B. (2011) The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes. Terra Nova, 23, 145–161.CrossRefGoogle Scholar
Legoux, P. (1960) Les Péridotites de Conakry et du Kaloum (République de Guinée) et leur serpentinisation. Bulletin de la Société géologique de France, S7, 50–63.CrossRefGoogle Scholar
McDonough, W.F. and Sun, S.-S. (1995) The composition of Earth. Chemical Geology, 120, 223–253.CrossRefGoogle Scholar
Maier, W.D., Barnes, S.-J. and Li, C. (2001) A re-evaluation of the role of crustal contamination in the formation of magmatic sulfides in the Bushveld complex. 9th International Platinum Symposium. Billings, Montana, USA, pp. 283–285.Google Scholar
Mega Uranium (2006) http://www.megauranium.com/news_room/2006/index.php?&content_id=192Google Scholar
Milési, J.-P., Ledru, P., Feybesse, J.-L., Dommanget, A. and Marcoux, E. (1992) Early Proterozoic ore deposits and tectonics of the Birimian orogenic belt, West Africa. Precambrian Research, 58, 305–344.CrossRefGoogle Scholar
Moreau, C., Ohnenstetter, D., Demaiffe, D. and Robineau, B. (1996) The Los Archipelago nepheline syenite ring-structure; a magmatic marker of the evolution of the Central and Equatorial Atlantic. Canadian Mineralogist, 34, 281–299.Google Scholar
Nomade, S., Knight, K.B., Beutel, E., Renne, P.R., Verati, C., Féraud, G., Marzoli, A., Youbi, N. and Bertrand, H. (2007) Chronology of the Central Atlantic Magmatic Province: Implications for the Central Atlantic rifting processes and the Triassic–Jurassic biotic crisis. Palaeogeography, Palaeoclimatology, Palaeoecology, 244, 326–344.CrossRefGoogle Scholar
Pagé, P. and Barnes, S.-J. (2009) Using trace elements in chromites to constrain the origin of podiform chromitites in the Thetford Mines Ophiolite, Québec, Canada. Economic Geology, 104, 997–1018.CrossRefGoogle Scholar
Peck, D.C., Keays, R.R., James, R.S., Chubb, P.T. and Reeves, S.J. (2001) Controls on the formation of contact-type platinum-group element mineralization in the East Bull Lake Intrusion. Economic Geology, 96, 559–584.CrossRefGoogle Scholar
Pollett, J.D. (1931) Platinum mining in Sierra Leone. Engineering Mining World, 2, 747–748.Google Scholar
Ponsard, J.F. (1984) La marge du craton Ouest-Africain du Sénégal à la Sierra Leone: interprétation géophysique de la chaîne panafricaine et des bassins du protérozoïque à l'actuel. Unpublished PhD thesis, Aix-Marseille III University, France, 198 pp.Google Scholar
Ponsard, J. F., Roussel, J., Villeneuve, M. and Lesquer, A. (1988) The Pan-African orogenic belt of southern Mauritanides and northern Rokelides (southern Senegal and Guinea, West Africa): gravity evidence for a collisional suture. Journal of African Earth Sciences, 7, 463–472.CrossRefGoogle Scholar
Prichard, H.M., Barnes, S.-J., Fisher, P.C., Pagé, P. and Zientek, M.L. (2017) Laurite and associated PGM in the Stillwater chromitites: implications for processes of formation, and comparisons with laurite in the Bushveld and ophiolitic chromitites. Canadian Mineralogist, 55, 121–144.CrossRefGoogle Scholar
SEMAFO Inc. (1999) Semafo annual report 1998, Public report. Saint-Laurent, Quebec, Canada, 22 pp.Google Scholar
SEMAFO Inc. (2001) Semafo annual report 2000. Public report. Saint-Laurent, Quebec, Canada, 13 pp.Google Scholar
Sluzhenikin, S.F. (2011) Platinum-copper-nickel and platinum ores of Norilsk region and their ore mineralization. Russian Journal of General Chemistry, 81, 1288–1301.CrossRefGoogle Scholar
Taylor, G. and Eggleton, R.A. (2001) Regolith Geology and Geomorphology. John Wiley & Sons, Ltd., New York, 384 pp.Google Scholar
Thiéblemont, D., Goujou, J.C., Egal, E., Cocherie, A., Delor, C., Lafon, J.M. and. Fanning, M.C. (2004) Archean evolution of the Leo Rise and its Eburnean reworking. Journal of African Earth Sciences, 39, 97–104.CrossRefGoogle Scholar
Umeji, A.C. (1983) Geochemistry and mineralogy of the Freetown Layered Basic Igneous Complex of Sierra Leone. Chemical Geology, 39, 17–38.CrossRefGoogle Scholar
Villeneuve, M. (1984) Etude géologique sur la bordure sud-ouest du craton Ouest-Africain. La suture Panafricaine et l’évolution des bassins sédimentaires Protérozoïques de la marge NW du continent de Gondwana. PhD Thesis, Université d'Aix-Marseille, Aix-Marseille, France.Google Scholar
Villeneuve, M. (2008) Review of the orogenic belts on the western side of the West African craton: the Bassarides, Rokelides and Mauritanides. Pp. 169–201 in: The Boundaries of the West African Craton (Ennih, N. and Liégeois, J-P, editors). Geological Society, London, Special Publications, 297. The Geological Society, London.Google Scholar
Villeneuve, M. and da Rocha Araujo, P.R. (1984) La stratigraphie du bassin paléozoïque de Guinée (Afrique de l'Ouest). Bulletin de la Société Géologique de France, Séries 7, Vol. XXVI, 1033–1039.CrossRefGoogle Scholar
Villeneuve, M., Bellon, H., Corsini, M., Le Metour, J. and Chatelee, S. (2015) New investigations in southwestern Guinea: consequences for the Rokelide belt (West Africa). International Journal of Earth Sciences, 104, 1267–1275.CrossRefGoogle Scholar
Vymazalová, A., Laufek, F., Sluzhenikin, S.F. and Stanley, C.J. (2017) Norilskite, (Pd,Ag)7Pb4, a new mineral from Noril'sk-Talnakh deposit, Russia. Mineralogical Magazine, 81, 531–541.CrossRefGoogle Scholar
Wells, M.K. (1962) Structure and petrology of the Freetown layered basic complex of Sierra Leone. Overseas Geology and Mineral Resources. Bulletin Supplement, 4, 115 pp.Google Scholar
Supplementary material: File

Augé et al. supplementary material

Augé et al. supplementary material 1

Download Augé et al. supplementary material(File)
File 92.5 KB