Abstract
Petrology and oxide mineral chemistry are presented on 5 kimberlite dikes that are classified into three groups: (1) one dike is highly carbonated and highly oxidized (> MH) and is characterised by chlorite+Mn-titanomagnetite+rutile+hematite (after chlorite)+maghemite (after titanomagnetite), with ilmenite and perovskite being absent; (2) three dikes are typified by atoll-textured spinels +phlogopite+euhedral Mn-picroilmenite, of intermediate oxidation state (WM-FMQ) with coexisting deuterically serpentinized olivine+Ni-Fe alloys and magnetite; (3) the remaining dike records an early crystallization event under very low (≤ WM) redox conditions that precipitated anionic-deficient spinels and a Mg-Ti-Cr-wüstite-type phase, followed by late stage more oxidizing (=FMQ) Mnpicroilmenite.
Spinels are complexly zoned and crystallization trends among the dikes are diverse, underscoring the fact that no single compositional trend, or evolutionary sequence is typical of kimberlites. Ilmenites are euhedral, and criteria for groundmass crystallization are established. Extraordinarily high MnO (max 17 wt%) contents and high geikielite (62 mole%) concentrations expand the ilmenite field typically assigned to that of kimberlites. Zirconium, Nb and Cr are present in concentrations of 0.5–3 wt% (as oxides) in ilmenite. These highly incompatible elements, along with Mn, are concentrated in late stage melt fractions. The high pyrophanite contents, which are more typical of silicic alkali suites, are accompanied by phlogopite in the Koidu dikes.
Objective evaluations of kimberlite-carbonatite relations, as outlined in the literature, cannot be made based on the oxide mineral group. Much of the compositional data for oxides in kimberlites are on mantle-derived xenolith suites and are not from oxides derived from the crystallization of kimberlitic melts.
Assessments of the fO2's of kimberlites have considerable potential in evaluating diamond survival through redox reactions. Manganese-rich (+Nb, Zr, Cr) ilmenites are typical of many kimberlites and should be considered in the suite of index minerals employed in prospecting.
Similar content being viewed by others
References
Albee AL, Ray L (1970) Correction factors for electron probe microanalysis of silicates, oxides, carbonates, phosphates, and sulfates. Anal Chem 42:1408–1414
Bence AE, Albee AL (1968) Empirical correction factors for the electron microanalysis of silicates and oxides. J Geol 76:382–403
Boctor NZ, Boyd FR (1979) Distribution of rare earth elements in perovskite from kimberlites. Carnegie Inst Washington Yearb 78:572–574
Boctor NZ, Boyd FR (1981) Oxide minerals in a layered kimberlite carbonatite sill from Benfontein, South Africa. Contrib Mineral Petrol 76:253–259
Boctor NZ, Svisero DP (1978) Iron-titanum oxide and sulfide minerals in carbonatite from Jacupiranga, Brazil. Carnegie Inst Wash Yearb 77:876–880
Brown C, Mahdi A (1980) No 1 pipe geology, 100 ft bench, 1160′ level. Sierra Leone Selection Trust (Ltd)
Dawson JB (1980) Kimberlites and their xenoliths. Springer, Berlin Heidelberg New York
Dawson JB, Hawthorne JB (1973) Magmatic sedimentation and carbonatitic differentiation in kimberlite sills at Benfontein, South Africa. J Geol Soc Lond 129:61–85
Donaldson CH, Reid AM (1982) Multiple intrusion of a kimberlite dike. Trans Geol Soc S Africa 85:1–12
Finger LW (1972) The uncertainty in the calculated ferric iron content of a microprobe analysis. Carnegie Inst Washington Yearb 71:600–603
Gaspar JC, Wyllie PJ (1983a) Magnetite in the carbonatites from the Jacupiranga complex, Brazil. Am Mineral 68:195–213
Gaspar JC, Wyllie PJ (1983b) Ilmenite (high Mg Mn Nb) in the carbonatites from the Jacupiranga complex, Brazil. Am Mineral 68:960–971
Gaspar JC, Wyllie PJ (1984) The alleged kimberlite carbonatite relationship: Evidence from ilmenite and spinel from Premier and Wesselton mines and the Benfontein Sill, South Africa. Contrib Mineral Petrol 85:133–140
Gold DP (1966) The average and typical chemical composition of carbonatites. Mineralogical Society of India, IMA: 83–91
Haggerty SE (1975) The chemistry and genesis of opaque minerals in kimberlites. LH Ahrens JB Dawson AR Duncan and AJ Erlank (eds) Physics and Chemistry of the Earth 9:295–307
Haggerty SE (1976) Opaque mineral oxides in terrestrial igneous rocks. D. Rumble (ed) Oxide Minerals Short Course Notes, Mineral Soc Am 3:101–300
Haggerty SE, Tompkins LA (1983) Redox state of Earth's upper mantle from kimberlitic ilmenites. Nature 303:295–300
Hauck J (1981) Crystallography and phase relations of MeO, M2O3, TiO2 systems (Me = Fe Mg Ni, M = Al Cr Fe). J Solid State Chem 36:52–65
Heinrich E Wm (1966) The geology of carbonatites. Rand McNally and Company, Chicago
Hunter RH, Kissling RD, Taylor LA (1984) Mid to late stage kimberlitic melt evolution, phlogopites and oxides from the Fayette county kimberlite, Pennsylvania. Am Mineral 69:30–40
Hsu J-A, Taylor LA (1978) An unusual mineralogy in the Norris kimberlite of Tennessee. Geol Soc Am (Abstracts with Progams) p 172
Jones AP, Wyllie PJ (1985) Paragenetic trends of oxide minerals in carbonate-rich kimberlites, with new analyses from the Benfontein Sill, South Africa. J Petrol 26:210–222
Kapustin UYL (1980) Mineralogy of Carbonatites. Amerind Publishing Co Ltd, New Delhi
Katsura T, Kitayam K, Aoyagi R, Sasajima S (1976) High temperature experiments related to Fe Ti oxide minerals in volcanic rocks. Kazan (Volcanoes) Bull Volcanol Soc Jap 21:31–56
King OF (1965–1967) No 1 shaft Koidu geological plan at 300 ft level. National Diamond Mining Co (SL) Ltd
Lindsley DH (1976) Experimental studies of oxide minerals. D Rumble (ed) Oxide Minerals Short Course Notes. Mineral Soc Am 3:61–68
Lindsley DH, Spencer KJ (1982) Fe-Ti oxide geothermometry: reducing analyses of coexisting Ti-magnetic (Mt) and ilmenite (Ilm), (abs) EOS Am Geophys Union 63:471
Lipman PW (1971) Iron titanium oxide phenocrysts in compositionally zoned ash flow sheets from southern Nevada. J Geol 79:438–456
McMahon BM, Haggerty SE (1979) The Oka carbonatite complex: Magnetite compositions and the related role of titanium in pyrochlore. FR Boyd and HOA Meyer (eds) Kimberlites, Diatremes, and Diamonds: Their Geology Petrology and Geochemistry. Am Geophysical Union, Washington pp 382–392
McMahon BM, Haggerty SE (1980) Experimental studies bearing on the magnetite alloy sulfide association in the Allende meteorite: Constraints on the conditions of chondrule formation. Proceedings of the Eleventh Lunar and Planetary Science Conference. Pergamon Press, New York, pp 1003–1025
McMahon BM, Haggerty, SE (1984) The Benfontein kimberlite sills: Magmatic reactions and high intrusion temperatures. Am J Sci 284:893–941
Mitchell RH (1972) Composition of perovskite in kimberlite. Am Mineral 57:1748–1753
Mitchell RH (1979) The alleged kimberlite carbonatite relationship: Additional contrary mineralogical evidence. Am J Sci 279:570–589
Mitchell RH, Clarke DB (1976) Oxide and sulphide mineralogy of the Peuyuk kimberlite, Somerset Island, N.W.T., Canada. Contrib Mineral Petrol 56:157–172
Muan A, Hauck J, Osborn EF, Schairer JF (1971) Equilibrium relations among phases occuring in lunar rocks. Proceedings of the Second Lunar Science Conference. MIT Press 1:497–505
Neumann ER (1974) The distribution of Mn2+ and Fe2+ between ilmenites and magnetites in igneous rocks. Am J Sci 274:1074–1084
Pasteris JD (1980) The significance of groundmass ilmenite and megacryst ilmenite in kimberlites. Contrib Mineral Petrol 75:315–3225
Pasteris JD (1983) Spinel zonation in the de Beers kimberlite, South Africa: Possible role of phlogopite. Canad Mineral 21:41–58
Pasteris JD (1984) Justification for possible use of indigenous kim berlite minerals in evaluation of diamond potential. Process Mineral Spec Issue Am Inst Min Metall, Eng (in press)
Platt RG, Mitchell RH (1979) The Marathon dikes: I. Zirconium rich titanian garnets and manganoan magnesian ulvöspinel magnetite spinels. Am Mineral 64:546–550
Prins P (1972) Composition of magnetite from carbonatites. Lithos 5:227–240
Robinson DN (1975) Magnetite serpentine calcite dykes at Premier mine and aspects of their relationship to kimberlite and to carbonatite of alkali carbonatite complexes. LH Ahrens, JB Dawson, AR Duncan, AJ Erlank (eds) Physics and Chemistry of the Earth 9:61–70
Scott-Smith BH, Danchin RV, Harris JW and Stracke KJ (1984) Kimberlites near Orroroo South Australia. J Kornprobst (ed) Kimberlites I: Kimberlites and related rocks. Developments in Petrology 11A. Elsevier, Amsterdam pp 121–142
Shee SR (1984) The oxide minerals of the Wesselton Mine Kimberlite, Kimberley, South Africa. J Kornprobst (ed) Kimberlites I: Kimberlites and Related Rocks. Developments in Petrology 11A, Elsevier, Amsterdam pp 59–73
Smith CB (1983) Two types of sources for southern African Cretaceous kimberlites: Pb, Sr and Nd isotopic evidence. Nature 304:51–54
Speidel DH (1967) Phase equilibria in the system MgO-FeO-Fe2O3: The 1300° C isothermal section and extrapolations to other temperatures. Am Ceram Soc J 50:243–248
Spencer KJ, Lindsley DH (1981) A solution model for coexisting iron-titanium oxides. Am Mineral 66:1189–1202
Tatarintsev VI, Tsymbal SN, Garanin VG, Kudryatseva GP, Marshintsev VK (1983) Quenched particles from kimberlites of Yakutia. Doklady Earth Sci Sect 270:144–148
Tompkins LA (1983) The Koidu Kimberlite Complex, Sierra Leone, West Africa. Unpublished MS Thesis University of Massachusetts Amherst, Mass
Tompkins LA, Haggerty SE (1984) The Koidu kimberlite complex Sierra Leone: Geological setting, petrology and mineral chemistry. J Kornprobst (ed) Kimberlites I: Kimberlites and Related Rocks. Developments in Petrology 11A. Elsevier, Amsterdam pp 83–105
Tompkins LA, Bailey SW, Haggerty SE (1984) Kimberlitic chlorites from Sierra Leone, West Africa: Unusual chemistries and structural polytypes. Am Mineral 69:237–249
Ulmer GC (1970) Chromite spinels. AM Alper (ed) High temperature oxides. Part I Magnesia, lime and chrome refractories. Acad Press New York pp 251–314
Vartiainen H, Kresten P, Kafkas Y (1978) Alkaline lamprophyres from the Sokli Complex, northern Finland. Bull Geol Soc Finland 50:59–68
Wasilewski P, Virgo D, Ulmer GC, Schwerer, FC (1975) Magnetochemical characterization of Fe (FexCr(in2−x) O4 Spinels. TN Irvine (ed) Chromium: Its physiochemical behavior and petrologic significance. Pergamon, Oxford New York, pp 889–902
Wyatt BA (1979a) Manganoan ilmenite from the Premier kimberlite. (extended abstracts) Kimberlite Symposium II, Cambridge
Wyatt BA (1979b) Kimberlitic chromian picroilmenite with inter growths of titanian chromite and rutile. FR Boyd and HOA Meyer (eds) The Mantle Sample: Inclusions in kimberlites and other Volcanics. Am Geophysical Union, Washington pp 257–264
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tompkins, L.A., Haggerty, S.E. Groundmass oxide minerals in the Koidu kimberlite dikes, Sierra Leone, West Africa. Contr. Mineral. and Petrol. 91, 245–263 (1985). https://doi.org/10.1007/BF00413351
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00413351