Abstract
Ore microscopic studies reveal two main parageneses in the banded iron-formations of Nigeria. In the low-grade metamorphic schist belts of northern Nigeria, a magnetitic paragenesis comprising magnetite, silicates (grunerite and garnet), and quartz is developed. Magnetite which sometimes contains carbonate inclusions is markedly martitized. In contrast, the higher-grade metamorphic terrains of central Nigeria exhibit a different paragenesis consisting of hematite (including specularite) and quartz. Here, minerals of the magnetitic paragenesis only occur as relics. The protolith of these banded iron-formation occurrences envisioned as carbonate-containing sediments, with high concentrations of Fe and Si, and lower contents of Ca, Mg, Al (and also Mn where they are associated with gondite) underwent both submarine weathering and metamorphic changes in their evolution. During submarine weathering, sheet silicates and porphyroblasts of Fe-Mn-(Mg-Ca)-carbonate solid solutions, were formed. At the outset of a regional metamorphic episode, grunerite, garnet and porphyroblastic magnetite were developed. Magnetite formed at the expense of carbonate and sheetsilicates but was later martitized under post-metamorphic conditions. In the course of a later heterogeneous tectono-metamorphic event, martitized magnetite was transformed as follows: under low-grade metamorphism, as observed in the northern Nigerian schist belts, recrystallization into coarse-grained martite occurred, while at the higher grades of metamorphism in central Nigeria, recrystallization into hematite and, ultimately, specularite, took place. This relationship between magnetite and hematite has also been observed in many other banded iron-formations from different parts of the world, thus underscoring its widespread significance. Magnetite crystallizes first at the expense of carbonate and silicate minerals and hematite is subsequently derived from it directly or generally through martitization. This metamorphic phenomenon contradicts the common assumption that magnetite and hematite in banded iron-formations are invariably the products of direct precipitation from solution, in response to changes in environmental Eh/pH or different (reducing/oxidizing) diagenetic alterations of precipitated ferric hydroxide.
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Acharya, S., Amstutz, G.C., Sarangi, S.K. (1982) Diagenetic crystallization and migration in banded iron formations of Orissa, India. In: Amstutz, G.C. (ed.) Ore Genesis. State of Art. Springer, Berlin Heidelberg New York, pp. 442–449
Ajibade, A.C. (1980) Geotectonic evolution of the Zungeru Region, Nigeria. Unpublished Ph.D. thesis, University of Wales (Aberystwyth), 302 pp.
Annor, A.E. (in preparation) U-Pb zircon age for Kabba-Okene granodiorite gneiss: implications for Nigeria's basement chronology
Ayres, D.E. (1972) Genesis of iron-bearing minerals in banded iron formation mesobands in the Dales Gorge Member, Hamersley Group, Western Australia. Econ. Geol. 67:1214–1233
Berner, R.A. (1969) Goethite stability and the origin of red beds. Geochim. Cosmochim. Acta 33:267–273
Berge, J.W., Johanssen, K., Jack, J. (1977) Geology and origin of the hematite ores of the Nimba Range, Liberia Econ. Geol. 72: 582–607
Boderick, T.M. (1920) Economic geology and stratigraphy of the Gunflint iron district, Minnesota. Econ. Geol. 15: 422–452
Chakraborty, K.L., Majunder, T. (1992) An unusual diagenetic structure in the Precambrian banded iron formation (BIF) of Orissa, India, and its interpretation. Mineral. Deposita 27:55–57
Eichler, J. (1976) Origin of the Precambrian Banded Iron-Formations. In: Handbook of Strata-Bound and Stratiform Ore Deposits, Vol. 7, Elsevier, Amsterdam Oxford New York, pp. 157–201
Floran, R.J., Papike, J.J. (1975) Petrology of the low-grade rocks of the Gunflint iron-formation, Ontario-Minnesota. Geol. Soc. Am. Bull. 86:1169–1190
French, B.M. (1973) Mineral assemblages in diagenetic and low-grade metamorphic iron-formation. Econ. Geol. 68:1063–1074
Frey, M., Hunzicker, C. (1973) Progressive niedriggradige Metamorphose glaukonitführender Horizonte in den helvetischen Alpen. Contr. Miner. Pert. 39:185–218
Gastil, G., Knowles, D.A. (1960) Geology of the Wabush Lake Area, Southwestern Labrador and Eastern Quebec, Canada. Bull. Geol. Soc. Am. 71:1243–1254
Gole, M.J., Klein, C. (1981) Mineralogy and petrology of parts of the Marra Mamba Iron Formation, Hamersley Basin, Western Australia. Am. Min. 66:507–525
Goodwin, A.M. (1956) Facies relations in Gunflint iron-formation. Econ. Geol. 51:565–595
Goodwin, A.M. (1973) Archean iron formations and basins. Econ. Geol. 68:915–930
Han, T.M. (1982) Iron formations of Precambrian age. Hematite-magnetite relationships in some Protorozoic iron deposits. — A microscopic observation. In: Amstutz, G.C. (ed.) Ore Genesis. State of Art. Springer, Berlin Heidelberg New York, pp. 451–459
Hartlieb, Ch. (1990) Die regionalmetamorphe BIF von Maraba Hill (Maru Belt, Nordnigeria) in Assoziation mit Mn-haltigen Gesteinen. Unpublished Diplomarbeit, University of Göttingen, 128 pp.
James, H.L. (1954) Sedimentary facies of iron formation. Econ. Geol. 49:235–293
James, H.L. (1955) Zone of regional metamorphism in the Precambrian of Northern Michigan. Geol. Soc. Am. Bull. 66: 1455–1488
Kalliokoski, J. (1965) The metamorphosed iron ore of El Pao, Venezuela. Econ. Geol. 60:100–166
Kaufmann, A.J., Hayes, J.M., Klein, C. (1990) Primary and diagenetic controls of isotopic compositions of iron-formation carbonates. Geochim. Cosmochim. Acta 54:3461–3473
Kimberley, M.M. (1989a) Nomenclature for iron formations. Ore Geology Reviews 5:1–12
Kimberley, M.M. (1989b) Exhalative origins of iron formations. Ore Geology Reviews 5:13–145
Klein (Jr.), C. (1973) Changes in mineral assemblages with metamorphism of some banded Precambrian iron-formations. Econ. Geol. 68:1075–1088
Krumbein, W.C., Garrels, R.H. (1952) Origin and classification of chemical sediments in terms of pH and oxidation-reduction potential. J. Geol. 60:1–33
LaBerge, G.L. (1964) Development of magnetite in iron-formations of the Lake Superior region. Econ. Geol. 59:1313–1342
Leith, C.K. (1931) Secondary concentration of Lake Superior iron ores. Econ. Geol. 26:274–288
Lougheed, M.S. (1983) Origin of Precambrian iron-formations in the Lake Superior region. Geol. Soc. Am. Bull. 94:325–340
Mann, V.J. (1953) The relation of oxidation to the origin of soft iron ores of Michigan. Econ. Geol. 48:251–281
Mel'nik, Y.P. (1982) Precambrian banded iron-formations. In: Windley (advisory ed.) Developments in Precambrian Geology 5. Elsevier, Amsterdam Oxford New York, 310 pp.
Morris, R.C. (1980) A textural and mineralogical study of the relationship of iron ore to banded iron-formation in the Hamersley iron province of Western Australia. Econ. Geol. 75:184–209
Morris, R.C. (1985) Genesis of iron ore in banded iron-formation by supergene and supergene-metamorphic processes — a conceptual model. In: Wolf K.H., (ed.) Handbook of strata-bound and stratiform ore deposits, Vol. 13. Elsevier, Amsterdam pp. 73–235
Morris, R.C. (1987) Iron ores derived by the enrichment of banded iron-formation. In: Hein J.R., (ed.) The genesis of ores and petroleum associated with sedimentary siliceous deposits Van Nostrand, New York, pp. 231–267
Morris, R.C., Horwitz, R.C. (1983) The origin of the iron-formation-rich Hamersley Group of Western Australia — Deposition on a platform. Prec. Res. 21:273–297
Mücke, A. and Woakes, M. (1986) Pyrophanite, a typical mineral in the Pan-African province of western and central Nigeria. J. African Earth Sci. 5:675–689
Neumann, U. (1988) Mineralogie und Genese der Manganverkommen in den Schiefergürteln von Nordnigeria. Unpublished Dissertation, Universität Göttingen, 227 pp.
Ogezi, A.E.O. (1977) Geochemistry and geochronology of basement rocks from northwestern Nigeria. Unpublished Ph.D. thesis, University Leeds, UK, 295 pp.
Okonkwo, C.T. (1991) The petrology and geochemistry of Koriga iron-formation, N.W. Nigeria. Geol. en Mijnbouw 70:39–44
Quade, H. (1988) Natural and simulated (10.4) pole figures of polycrystalline hematite. Textures Microtextures 8/9: 719–736
Trendall, A.F., Blockley, J.G. (1970) The iron formations of the Precambrian Hamersley Group, Western Australia; with special reference to crocidolithe. Geol. Surv. West. Aust. Bull. 119:336
Tyler, S.A. (1949) Development of Lake Superior soft iron ores from metamorphosed iron-formation. Geol. Soc. Amer. Bull. 60: 1101–1124
Walker, I.C.G. (1984) Suboxic diagenesis in banded iron formations. Nature 309:340–341
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Mücke, A., Annor, A. Examples and genetic significance of the formation of iron oxides in the Nigerian banded iron-formations. Mineral. Deposita 28, 136–145 (1993). https://doi.org/10.1007/BF00196338
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DOI: https://doi.org/10.1007/BF00196338