Major Oxides Geochemistry of Tourmaline from Selected Gem-Mineral Deposits in Southwestern Nigeria
DOI:
https://doi.org/10.18034/apjee.v5i2.253Keywords:
Southwestern Nigeria, Tourmaline, Major oxides, Pegmatite, Host rock, Magmatic originAbstract
Tourmaline occurs in associations with other gem minerals such as beryl, topaz, garnet and kunzite alongside rock-forming minerals like quartz, feldspar and muscovite in various gem mineral deposits across southwestern Nigeria. These occurrences of tourmaline in varieties of colors resulting from its range in chemical compositions remain puzzling, more so when there is a lack of sufficient information on the chemistry of the Nigerian tourmalines. This study is aimed at the major oxides investigation of tourmalines from selected gem-mineral deposits in southwestern Nigeria and how the chemistry can be used to infer their environment and processes of mineralization. A total of 22 differently colored tourmaline samples obtained from different locations in southwestern Nigeria were prepared and analyzed, using the inductively coupled plasma - mass spectrometry (ICP-MS) to determine the elemental constituents. Komu and Ijero-Ekiti, being the two areas with highest concentrations of the study samples were specially chosen and mapped, at least to reveal the geology of some gem mineral deposits in the area. Results of the geochemical analysis of the tourmaline samples showed enrichment in SiO2 and Al2O3, but depletion in the remaining major oxides. However, a few of the tourmaline samples showed unusual enrichment in CaO, revealing the fact that the samples have crystallized from highly fractionated melt. The major oxide compositions of the tourmalines exhibited wide and distinct variations, especially in SiO2, Al2O3 and CaO, indicating magmatic origin for the southwestern Nigerian tourmalines. Similarly, the strong negative correlations observed between CaO and the oxides Al2O3, Na2O, K2O and SiO2 in the tourmaline samples, coupled with the relatively high Fe/Fe+Mg ratio, averaging 0.89,clearly reinforced magmatic sourcing for the tourmalines. Almost all the southwestern tourmaline samples plot in the predefined field of Li-rich granitoidpegmatites and aplites in the Al-Fe-Mg and Ca-Fe-Mg plots. Southwestern Nigerian tourmalines are thus magmatic in origin with their chemistry reflecting control by host rocks and granitic-pegmatitic fluid. The study also revealed that the intensity of coloration in tourmalines can be linked to the presence or otherwise of iron concentration. The iron content varies directly and proportionately with the depth of color in the greens, and inversely in the pinks and reds.
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Adetunji, A., Olarewaju, V. O.,Ocan, O. O., Ganev, V. Y. and Macheva, L. 2016.Geochemistry and U-Pb zircon geochronology of the pegmatites inEde area, southwestern Nigeria: A newly discovered oldest Pan Africanrock in southwestern Nigeria. Journal of African Earth Sciences 115, 177-190
Akande, S. O. and Reynolds, P. H. 1990. 40Ar/39Ar spectrum ages of micas from the Sn-Nb-Ta bearing pegmatites in Nigeria. In: Proceeding, Volume 15, Colloquium of African Geology. Centre International Pour la Formation Et les EchangesGeologiques (CIFEG) Occassional Publication 1990/20 p243.
Annor, A. E., Olobaniyi, S. B. and Mucke, A. 1996. A note on the geology of the Isanlu area in the Egbe-Isanlu Schist Belt, S. W. Nigeria. Journal of Mining and Geology.32(1)47-51
Annor, A.E. 1995. U-Pb zircon age for the Kabba-Okene granodiorite gneiss:implication for Nigeria's basement chronology. Afr. Geosci. Rev. 2, 101-105.
Ball, E. 1980. An example of very consistent brittle deformation over a wide intra-continental area: The late Pan-African Fracture system of the Tuareg and Nigerian Shield. Tectonophys 61,363-379.
Black, R. 1980. Precambrian of West Africa, Episodes, 4, 3-8.
Cavarretta, G. and Puxeddu, M. 1990. Schorl-dravite-ferridravite tourmalines deposited by hydrothermal magmatic fluids during early evolution of the Larderello geothermal field, Italy. Economic Geology. 85 (6), 1236-1251.
Dada, S. S., Lancelot, J. R. and Briqueu, I. 1987. Age and origin of a Pan-African charnockitic complex: U-Pb and Rb-Sr evidence from the charnockitic complex at Toro, Northern Nigeria. Abtr. Vol. 14 Coll. Afri. Geol. Berlin, 72-73.
Dada, S.S. 2006. Proterozoic Evolution of Nigeria. In: The Basement Complex of Nigeria and its Mineral Resource. Oshin, O. Ed. Akin Jinad and Co. Ibadan, Nigeria, pp24 – 44.
Dada, S.S., 1998. Crust-forming ages and Proterozoic crustal evolution in Nigeria: areappraisal
Deer W.A, Howie R.A. and Zussmam, J. 1966. An introduction to the rock-forming minerals. 2nd ed. London: Longman group ltd. 696p.
Demirel, S. 2004. Origin and significance of a quartz tourmaline breccia zone within the central Anatolian crystalline complex, Turkey. M.Sc project. Dept. of geological engineering. Middle East technical university. Xv + 111pp.
Dunn, P. J. 1977. Elbaite from Newry, maine. Mineralogical Record, 6:22-25
Ekwueme, B. N. and Matheis, G. 1995. Geochemistry and economic value of pegmatites in the Pre-cambrian basement of Southeast Nigeria. In: Magmatism in relation to diverse tectonic settings. Srivastava, R. K. and Chandra, R. eds. IBH Publishing Co., New Delhi, India, 375-392pp.
Elueze, A. A. 1992. Rift system for Proterozoic schist belts in Nigeria. Tectonophysics.209 167-169.
Elueze, A. A. 2000. Compositional appraisal and petrotectonic significance of Imelu banded ferruginous rock in the Ilesha schist belt south western Nigeria. Journ. Min. Geol. 36(1). 9-18.
Frondel, C., and Collette, R. L. 1957. Synthesis of toumaline by reaction of mineralgrains with NaCl-H3BO3 solution, and its implications in rock metamorphism. American Mineralogist, 42, 754-758.
Garba, I. 1992. Geology, geochemistry and origin of gold mineralization at Bin Yauri, Nigeria. PhD Thesis, University of London, UK. 264pp.
Garba, I. 2003. Geochemical discrimination of newly discovered rare-metal bearing and barren pegmatites in the Pan-African (600±150Ma) basement of northern Nigeria. Applied Earth Science (Trans. Inst. Min. Metall.) 112; 287-292.
Grant, N. K. 1969. The late Precambrian to Early Paleozoic Pan- African orogeny in Ghana, Togo, Dahomey and Nigeria. Bull Geol. Soc. Amer. Vol. 50 pp.45 – 56.
Grew, E. S. 1996. Borosilicates (exclusive of tourmaline) and boron in rock-forming minerals in metamorphic environments. Reviews in Mineralogy, 33, 387-502.
Harper, C. T., Sherrer. G., McCurry, P. and Wright, J. B. 1973. K-Ar retention ages from the Pan- African of Northern Nigerian, Bull. Geol. Soc. Amer. Pp. 919 – 926.
Hawthorne, F. C, McDonald, D.J., Burns, P.C., 1993. Reassignment of cation site occupancies in tourmaline: AI-Mg disorder in the crystal structure of dravite. American Mineralogist, 78, 265-270.
Hawthorne, F. C. and Henry, D. J. 1999. Classification of the minerals of the tourmaline group. European Journal of Mineralogy, 11, 201-215.
Henry, D.J. and Guidotti, C. V. 1985. Tourmaline as a petrogenetic indicator mineral: an example from the staurolite-grade metapelites of NW Maine. American mineraogistl.70,1-15.
Jacobson, R.R. E and Webbs, J. S. 1946. The pegmatites of central Nigeria. Geol. Surv. Nigeria Bull. 17, 66p.
Kabata-Pendias, A. 2001. Trace elements in soils and plants. 3rd ed. CRS press. NY.
Kuster, D. 1990. Rare-metal pegmatites of Wamba, Central Nigeria-their formation in relationship to late Pan-African granites. Mineral Deposita25, 25-33.
Macdonald, D.J., Hawthorne, F.C. and Grice, J.D. 1993.Foitite, a new alkali deficient tourmaline: description and crystal structure. Am. Mineral. 78, 1299-1303.
Matheis, G. and Caen-Vachette, M. 1983. Rb-Sr isotopic study of rare-metal bearing and barren pegmatites in the Pan-African reactivation zone of Nigeria. J. Afr. Ear. Sci. 1, 35-40.
Morgan, G. B. and London, D. 1989. Experimental reactions of amphibolite with boron-bearing aqueous fluids at 200 MPa: implications for tourmaline stability and partial melting in mafic rocks. Contributions to Mineralogy and Petrology, 102, 281–297.
Obaje, N.G. 2009. Geology and Mineral Resources of Nigeria. Lecture Notes in Earth Sciences. 120, DOI 10.1007/978-3-540-92685-6 2.
of current interpretations. Precambrian Res. 87, 65-74.
Okonkwo, C.T., Ganev, V.Y., 2012. U-Pb zircon geochronology of the Jebba granitic gneiss and its implications for the Paleoproterozoic evolution of Jebba area, southwestern Nigeria. Int. J. Geosci. 3, 1065-1073.
Olarewaju, V. O. 1999. Fluid inclusion studies of Coarse- grained Charnockitic and hybrid rocks in Ukpilla area, Southwestern Nigeria. Joun. Min. Geology 35 (1) pp 1- 8.
Oversby, V. M. 1975. Lead Isotope study of aplites from the Precambrian basement rocks near Ibadan, Southwestern Nigeria. Earth Planets, Sci. Lett. 27, pp177 – 180.
Parkin, K. M., Loeffler, B. M., and Burns, R. G. 1977. Mössbauer spectra of kyanite, aquamarine, and cordierite showing intervalence charge transfer. Physics and Chemistry of Minerals. 1(3), 301-311
Pezzotta, F. and Laurs, B. M. 2011. Tourmaline: The kaleidoscopic gemstone. Elements 7: 333-338.
Platonov, A. N., Langer, K., Chopin, C., Andrut, M., and Taran, M. N. 2000. Fe2+-Ti4+charge-transfer in dumortierite. European Journal of Mineralogy. 12 (3), 521-528.
Rahaman, M. A. and Ocan O. 1978. On relationships in the Precambrian Migmatite-gneisses of Nigeria. Niger J Min Geol 15:23–32.
Rahaman, M. A., Ajayi, T. R., Oshin, I. O., and Asubiojo, F. O. 1988. Trace elements Geochemistry and geotectonic setting of Ife-Ilesha schist belts. Precambrian Geology of Nigeria. GNS Publications. Kaduna., pp241-256.
Rahaman, M. A., Emofurieta, W. D.and Caen-Vachette, M. 1983. The potassic granites of the Igbeti area: Further evidence of the polycyclic evolution of the Pan-African belt in South Western Nigeria. Precamb. Res. 22, 27-92.
Rahaman, M.A. 1988. Recent advances in the study of the basement complex of Nigeria. In: Oluyide, P.O., Mbonu, W.C., Ogezi, A.E.,Egbuniwe, I.G., Ajibade, A.C., Umeji, A.C. (Eds.).Precambrian Geology of Nigeria. Geological Survey of Nigeria Special Publication. pp. 11-41.
Selway, J.B., Novák, M., Hawthorne, F.C., Černý, P., Ottolini, L. and Kyser, T.K. 1998.Rossmanite, □(Li,Al2)Al6Si6O18(BO3)3(OH)3(OH), a new alkali deficient tourmaline; description and crystal structure. Am. Mineral. 83, 896-900.
Slack, J. F. 1996. Tourmaline associations with hydrothermal ore deposits. Boron mineralogy, petrology and geochemistry. E.S. Grew and L.N. Anovitz. Eds. Reviews in Mineralogy. 33. 559-643.
Turner, D. C. 1983. Upper Proterozoic schist belts in the Nigerian sector of the Pan-African province of West Africa. Precambrian Research, 21, 55-79.
Umeji, A. C. and Caen-Vachette, M.1984. Geochronology of Pan-Africa Nasarawa Eggon and MkarGboko granites, South East Nigeria. Precambr. Res. 23, 317-324.
Van Breemen, O., Pidgeon, R. T. and Bowden, P. 1977. Age and isotopic studies of Pan-African granites from North-Central Nigeria.Precambr. Res. 4, 307-319.
Wright, J. B. 1970. Controls of mineralization in the Older and Younger tin fields of Nigeria. Economic Geology. 65:945-951.
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