Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Journal of the Geological Society

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Thomas, M. F. Articles by Teeuw, R. M. Search for Related Content GeoRef GeoRef Citation

Palaeogeomorphology and the occurrence of diamondiferous placer deposits in Koidu, Sierra Leone

Department of Environmental Science, The University, Stirling FK9 4LA, Scotland, UK
^* Department of Geography, University College, Dublin 4, Republic of Ireland

The geomorphology and diamond distribution within the Koidu alluvial diamond field in Sierra Leone are examined to provide a methodology for palaeoplacer appraisal within a humid tropical environment of diverse relief and headwater drainage containing local diamond sources. A morphogenetic terrain model is proposed for use in devising prospecting programmes, based on geomorphological mapping and sediment analysis of terrain units mapped at 1:1250. Valley floors including headwater swamps and stream floodplains provide a radiocarbon-dated late Quaternary stratigraphic framework for deductions concerning interfluvial domains containing remnant river terraces, and colluvial stoneline deposits interspersed with non-alluvial erosional slopes. Planar interfluves as well as piedmont ‘glacis’ contain alluvial indicators within gravels composed of bedrock quartz and iron concretions derived from former landsurfaces. A process history for the interfluvial domain indicates downwasting and diagenesis of ancient degraded alluvials, lateral shifts of drainage lines and continued supply of diamonds from erosion of local sources, the ‘stonelines’ functioning as feeders of coarse clasts from the interfluves towards the valley floors. The use of geomorphology to provide descriptive and genetic terrain models to guide prospecting for alluvial placers is advocated as a standard procedure for use by mining geologists.

This article has been cited by other articles:

				D. G. Sutherland Geomorphological controls on the distribution of placer deposits Journal of the Geological Society, October 1, 1985; 142(5): 727 - 737. [Abstract] [PDF]

				I. a. n. Reid and L. E. Frostick Role of settling, entrainment and dispersive equivalence and of interstice trapping in placer formation Journal of the Geological Society, October 1, 1985; 142(5): 739 - 746. [Abstract] [PDF]