...M. F. Thomas; M. B. Thorp; R. M. Teeuw Abstract 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...

...-peridotite interaction experiments (Fig. DR1). The coexisting clinopyroxenes are mainly diopsidic in composition (Na 2 O = 1.71–3.72 wt%; Hills and Haggerty, 1989 ). Figure 1. Generalized geological map of northeastern Sierra Leone (from Rollinson, 1999 ), showing location of Koidu kimberlites (8°37...

... pipes? It was not until very large ilmenites (>10 cm in diam; Haggerty, 2013 ) were found, comparable to those from the Koidu Kimberlite Complex (pipes and dikes) in Sierra Leone ( Tompkins and Haggerty, 1984 ), that a pipe was seriously considered. Eluvial kimberlite can be recognized from rebar...

... orogen, northwestern Canada : Journal of Volcanology and Geothermal Research , v. 32 p. 99 – 118 . Hills , D.V. , and Haggerty , S.E. , 1989 , Petrochemistry of eclogites from the Koidu kimberlite complex, Sierra Leone : Contributions to Mineralogy and Petrology , v. 103 p. 397...

... 61 Thomas M. F. Thorp M. B. Teeuw R. Palaeogeomorphology and the occurrence of diamondiferous deposits in Koidu, Sierra Leone J geol Soc London 1985 142 789 802 Tricart J. Existence de périodes sèches au Quaternaire en Amazonie et dans les régions voisines Rev...

.... Thorp M. B. Teeuw R. M. Palaeogeomorphology and the occurrence of diamondiferous placer deposits in Koidu, Sierra Leone J geol Soc London 1985 142 789 802 Tourtelot H. A. Hydraulic equivalence of grains of quartz and heavier minerals and implications for the study of placers...

...F igure 5. ( a ) Ternary diagram (mol%) for ilmenite compositions from Mukorob (Table 1 ). The mineral data plot well within the main compositional field of megacrystic upper-mantle ilmenite. Exsolution pairs are from the carbonated Koidu Kimberlite Complex, Sierra Leone. Oxygen fugacity...

...S. J. Culver; H. R. Williams Abstract The post-Archaean geology of Sierra Leone is reviewed and interpreted. Late Precambrian development of fault-controlled sedimentation of glacigenic, fluviatile, and marine deposits with minor volcanics culminated in the Rokelide thermo-tectonic event at 550 Ma...

.... , McLennan , S.M. , 1985 . The Continental Crust: Its Composition and Evolution . Blackwell , Oxford . Tompkins , L.A. , Haggerty , S.E. , 1985 . Groundmass oxide minerals in the Koidu kimberlite dikes, Sierra Leone, West Africa . Contributions...

.... Although halloysite had not developed significantly in the topmost Koidu soils, 148 Some engineerhTg experiences in tropical soils TABLE 2. Mineralogical composition of fresh and weathered kimberlite, Sierra Leone. [After Fairbairn & Robertson] I"1 I 6, ; , ; .Kao l i . i te I , . t , 1" ' t FNontro- r...

... deficient, and the same may be true for olivine-bearing cpx- or garnet-rich delaminated lower crust of continents or arcs ( Jull and Kelemen, 2001 ) and for veins formed in the oceanic lithosphere ( Halliday et al., 1995 ). For example, the silica-deficient ilmenite eclogites from Koidu, Sierra Leone...

...Fig.2 Photomicrographs of some Lamprophyre clan rocks in ppl: a. Serpentinized olivine macrocrysts in a kimberlite from Koidu, Sierra Leone (photo J. John), b. Pinky phlogopite and calcite in orangeite from Finsch mine, S. Africa (photo J. Faithfull), c. Phlogopite laths and olivine...

...F ig . 2. Primitive-mantle-normalized spectra of aphanitic kimberlite dyke samples from Koidu, Sierra Leone ( Taylor et al . 1994 ). ...