Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-23T06:37:42.654Z Has data issue: false hasContentIssue false
  • English
  • Français

The diamond deposits of the Mandala basin, SE Guinea, West Africa

Published online by Cambridge University Press:  03 November 2011

Donald G. Sutherland
Donald G. Sutherland
Affiliation:
Placer Analysis Ltd, 2 London Street, Edinburgh EH3 6NA, Scotland
Get access Rights & Permissions [Opens in a new window]

Abstract

The Mandala drainage basin lies in the central part of the West African craton immediately to the south of the regional watershed. There has been frequent kimberlite dyke intrusion in the basin. The kimberlites range in grade from apparently barren to having a high diamond content. The presence of other undiscovered kimberlites can be inferred from the distribution, chemistry and abundance of kimberlite satellite minerals and variations in diamond size and character. Secondary diamond deposits are widespread with the main concentrations in the present and former Mandala valley bottoms. Tributaries have lower diamond contents. There are systematic variations in the alluvial diamond characteristics which can be explained in terms of diamond sources as well as transport of the diamonds away from those sources. The occurrence of the secondary diamond deposits is explained by the form and distribution of the primary sources, the nature of the drainage network and the long-term evolution of the drainage basin. Since the Pliocene or Early Pleistocene the Mandala has been rejuvenated with incision of the main channel by up to 26 m. This incision has led to flushing of the tributaries and storage of sediment, including diamonds, in the principal channel.

Keywords

Kimberlitessecondary diamond depositsdiamond characteristicsdrainage basin evolutiondiamond concentration
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 84 , Issue 2 , 1993 , pp. 137 - 149
Copyright
Copyright © Royal Society of Edinburgh 1993

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.)

References

Adams, J., Zimpfer, G. L. & McLane, C. F. 1978. Basin dynamics, channel processes, and placer formation: a model study. ECON GEOL 73, 416–26.Google Scholar
Afanas'yev, V. P., Ivaniv, I. N., Koptil, V. I. & Khar'kiv, A. D. 1974. Typomorphism of diamonds from kimberlite veins and the possible bedrock sources of diamond-bearing placers in northwestern Yakutiya. DOKL AKAD NAUK SSSR 214, 154–7.Google Scholar
Bardet, M G. 1974. Géologie du Diamant. Tome II. MEM B R G M83.Google Scholar
Bessoles, B. 1977. Géologie de l'Afrique, Tome I: Craton de l'Ouest Afrique. MEM B R G M 88.Google Scholar
Grantham, D. R. & Allen, J. B. 1960. Kimberlite in Sierra Leone. OVERSEAS GEOL MINER RESOUR 81, 5–25.Google Scholar
Gurney, J. J. 1984. A correlation between garnets and diamonds in kimberlites. In Glover, J. E. & Harris, P. G. (Eds) Kimberlite Occurrence and Origin: a basis for conceptual models in exploration. GEOLOGY DEPARTMENT UNIVERSITY EXTENSION, UNIVERSITY WESTERN AUSTRALIA PUBLICATION 8, 143–66.Google Scholar
Haggerty, S. E. 1975. The chemistry and genesis of opaque minerals in kimberlites. PHYS CHEM EARTH 9, 295–307.CrossRefGoogle Scholar
Haggerty, S. E. 1982. Kimberlites in western Liberia: an overview of the geological setting in a plate tectonic framework. J GEOPHYS RES 87(B13), 10, 811–26.Google Scholar
Hall, P. K. 1968. The Diamond Fields of Sierra Leone. BULL GEOL SURV SIERRA LEONE 5.Google Scholar
Harris, J. W. 1987. Recent physical, chemical, and isotopic research of diamond. In Nixon, P. H. (Ed.) Mantle xenoliths, 477–500. Chichester: John Wiley and Sons.Google Scholar
Harris, J. W. 1992. Diamond Geology. In Field, J. E. (Ed.) Properties of natural and synthetic diamonds, 345–93. London: Academic Press.Google Scholar
Harris, J. W., Hawthorne, J. B., Oosterveld, M. M. & Wehmeyer, E. 1975. A classification scheme for diamond and a comparative study of South African diamond characteristics. PHYS CHEM EARTH 9, 765–83.CrossRefGoogle Scholar
Harris, J. W., Hawthorne, J. B. & Oosterveld, M. M. 1984. A comparison of diamond characteristics from the De Beers mines, Kimberley, South Africa. ANNAL SCI UNIV CLERMONT-FERRAND II 74, 1–13.Google Scholar
Hurley, P. M., Leo, G. W., White, R. W. & Fairbairn, H. W. 1971. Liberian Age Province (about 2,700 m.y.) and adjacent provinces in Liberia and Sierra Leone. BULL GEOL SOC AMER 82, 3483–90.CrossRefGoogle Scholar
Kozlov, I. T. 1966. Geology and petrography of the kimberlites in Guinea. SOV GEOL 1966(6), 113–25. (In Russian.)Google Scholar
Macfarlane, A., Crow, M. J., Arthurs, J. W., Wilkinson, A. F. & Aucott, J. W. 1981. The geology and mineral resources of northern Sierra Leone. OVERSEAS MEM INST GEOL SCI 7.Google Scholar
Mitchell, R. H. 1977. Geochemistry of magnesian ilmenites from kimberlites from South Africa and Lesotho. LITHOS 10, 29–37.CrossRefGoogle Scholar
Mitchell, R. H. 1989. Aspects of the petrology of kimberlites and lamproites: some definitions and distinctions. In: Kimberlites and related rocks volume 1: their composition, occurrence, origin and emplacement. GEOL. SOC AUSTRALIA SPEC PUBL 14, 7–45.Google Scholar
Prokopchuk, B. I. 1974. The types of primary sources of diamonds and their role in forming diamond placers of different genetic types. GEOL GEOF 15(11), 76–81.Google Scholar
Robinson, D. N. 1979. Surface textures and other features of diamonds. (2 volumes). PhD Thesis, University of Cape Town.Google Scholar
Robinson, D. N., Scott, J. A., Van Niekerk, A. & Anderson, V. G. 1989. The sequence of events reflected in the diamonds of some southern African kimberlites. In: Kimberlites and related rocks, volume 2: their mantle/crust setting. Diamonds and diamond exploration. GEOL SOC AUSTRALIA SPEC PUBL 14, 990–1000.Google Scholar
Rombouts, L. 1987. Geology and evaluation of the Guinean diamond deposits. ANNAL SOC GEOL BELGIUM 110, 241–59.Google Scholar
Schumm, S. A., Mosley, M. P. & Weaver, W. E. 1987. Experimental fluvial geomorphology. New York: John Wiley and Sons.Google Scholar
Selivertsov, Yu. P. 1965. Neotectonics and topography of the West African platform. DOKL AKAD NAUK SSSR 158, 72–3.Google Scholar
Sichel, H. S. 1972. Statistical valuation of diamondiferous deposits. J S AFR INST MIN METALL 73, 235–43.Google Scholar
Sutherland, D. G. 1982. The transport and sorting of diamonds by fluvial and marine processes. ECON GEOL 77, 1631–20.CrossRefGoogle Scholar
Sutherland, D. G. 1984. Geomorphology and mineral exploration: some examples from exploration for diamondiferous placer deposits. ZEITS GEOMORPH N F SUPPL 51, 95–108.Google Scholar
Sutherland, D. G. 1985. Geomorphological controls on the distribution of placer deposits. J GEOL SOC LONDON 142, 727–37.Google Scholar
Sutherland, D. G. 1993. Drainage basin evolution in SE Guinea and the development of diamondiferous placer deposits. ECON GEOL 88, 44–54.CrossRefGoogle Scholar
Teeuw, R. M., Thomas, M. F. & Thorp, M. B. 1991. Geomorphology applied to exploration for tropical placer deposits. In: Alluvial mining1, 458–80. London: Institution of Mining and Metallurgy.Google Scholar
Thomas, M. F. & Thorp, M. B. 1980. Some aspects of the geomorphological interpretation of Quaternary alluvial sediments in Sierra Leone. ZEITS GEOMORPH N F SUPPL 36, 140–61.Google Scholar
Thomas, M. F. & Thorp, M. B. 1985. Environmental change and episodic etchplanation in the humid tropics of Sierra Leone: the Koidu etchplain. In Douglas, I. & Spencer, T. (Eds) Environmental change and tropical geomorphology, 239–67. London: George Allen and Unwin.Google Scholar
Thomas, M. F., Thorp, M. B. & Teeuw, R. M. 1985. Palaeogeomorphology and the occurrence of diamondiferous placer deposits in Koidu, Sierra Leone. J GEOL SOC LONDON 142, 789–802.Google Scholar
Tompkins, L. A. & Haggerty, S. E. 1984. The Koidu kimberlite complex, Sierra Leone: geological setting, petrology and mineral chemistry. In Kornprobst, J. (Ed.) Kimberlites I: kimberlites and related rocks, 83–105. Amsterdam: Elsevier.Google Scholar
Vladimirov, B. M., Tverdokhlebov, V. A. & Kolesnikova, T. P. 1971. Geology and petrography of igneous rocks from the southeastern part of the Guinea-Liberian shield. AKAD NAUK SSSR, SIBERIAN BRANCH (in Russian).Google Scholar