Hostname: page-component-76fb5796d-x4r87 Total loading time: 0 Render date: 2024-04-30T05:49:37.628Z Has data issue: false hasContentIssue false
  • English
  • Français

Oxidation-induced postmagmatic modifications of primary ilmenite, NYG-related aplite dyke, Tibchi complex, Kalato, Nigeria

Published online by Cambridge University Press:  05 July 2018

E. M. Sakoma  and
R. F. Martin
E. M. Sakoma*
Affiliation:
Department of Earth and Planetary Sciences, 3450 University Street, McGill University, Montreal, Quebec H3A 2A7, Canada
R. F. Martin
Affiliation:
Department of Earth and Planetary Sciences, 3450 University Street, McGill University, Montreal, Quebec H3A 2A7, Canada
*
*E-mail: emmanuel@eps.mcgill.ca
Get access Rights & Permissions [Opens in a new window]

Abstract

We describe an ilmenite-bearing aplitic syenite dyke in the roof zone of the Tibchi granite, exposed at Kalato, in the Tibchi ring-complex, northern Nigeria. Inclusions of ferrocolumbite, rutile and ixiolite in the ilmenite are inferred to have been trapped at the magmatic stage. The main mafic mineral is annite. Compositionally, the ilmenite, rutile and ferrocolumbite have near-end-member compositions. A positive correlation between Sc and Ta/(Ta+Nb) indicates that Sc behaved incompatibly as ferrocolumbite grew. Such entrapped accessory minerals may well have formed by local saturation at the ilmenite-melt and annite-melt interface. During and after their crystallization, the melt reached saturation in H2O and degassed. A second generation of ilmenite enriched in Mn and Zn replaced the primary ilmenite along fractures and grain margins. As fO2 began to increase, composite blebs and rinds of ‘ferropseudobrookite’, rutile and hematite began to develop by oxidation-induced exsolution in the primary ilmenite. Incorporation of Nb, Ta, Sc and Si in the ‘ferropseudobrookite’ may well have stabilized it at Kalato. Ultimately, it is transformed to hematite + rutile. The IMA-sanctioned view that the solid solution between pseudobrookite and Ti3O5 is complete, and thus that ‘ferropseudobrookite’, as an intermediate member of the series, does not merit species status, needs to be re-evaluated.

Keywords

ilmeniteferrocolumbite‘ferropseudobrookite’aplite dykesyeniteoxygen fugacityring complexTibchinorthern Nigeria
Type
Research Article
Information
Mineralogical Magazine , Volume 66 , Issue 4 , August 2002 , pp. 591 - 604
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bacon, C.R. (1989) Crystallization of accessory phases in magma by local saturation adjacent to phenocrysts. Geochimica et Cosmochimica Acta, 53, 1055–1066.CrossRefGoogle Scholar
Bowles, J.F.W. (1988) Definition and range of composition of naturally occurring minerals with the pseudobrookite structure. American Mineralogist, 73, 1377–1382.Google Scholar
Černý, P. and Ercit, T.S. (1985) Some recent advances in the mineralogy and geochemistry of Nb and Ta in rare-element granitic pegmatites. Bulletin de Minéralogie, 108, 499–532.CrossRefGoogle Scholar
Delvigne, J.E. (1998) Atlas of Micromorphology of Mineral Alteration and Weathering. The Canadian Mineralogist, Special Publication 3.Google Scholar
Droop, G.T.R. (1987) A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria. Mineralogical Magazine, 51, 431–435.CrossRefGoogle Scholar
El Bouseily, A.M. and El Sokkary, A.A. (1975) The relation between Rb, Ba, and Sr in granitic rocks. Chemical Geology, 16, 207–209.CrossRefGoogle Scholar
Grey, I.E. and Reid, A.F. (1975) The structure of pseudorutile and its role in the natural alteration of ilmenite. American Mineralogist, 60, 898–906.Google Scholar
Grey, I.E. Watts, J.A. and Bayliss, P. (1994) Mineralogical nomenclature: pseudorutile revalidated and neotype given. Mineralogical Magazine, 58, 597–600.CrossRefGoogle Scholar
Haag, H.L. (1943) Wolframite in Nigeria with notes on cassiterite, wolframite, and columbite zones. Transactions of the Institute of Mining and Metallurgy, 52, 119–183.Google Scholar
Haggerty, S.E. (1991) Oxide textures – a miniatlas. Pp. 128–219 in: Oxide Minerals: Petrologic and Magnetic Significance (Lindsley, D.H., editor). Reviews in Mineralogy, 25, Mineralogical Society of America, Washington, D.C.Google Scholar
Ike, E.C. (1983) The structural evolution of the Tibchi ring complex: a case study of the Nigerian Younger Granite Province. Journal of Geological Society, London, 140, 781–788.CrossRefGoogle Scholar
Janovsky, J.V. (1880) Über Niobit und ein neues Titanit von Isergebirge. Akadademische Wissenschaften Wien Klasse, (1) 80, 39.Google Scholar
Kinnaird, J.A. (1985) Hydrothermal alteration and mineralization of the alkaline anorogenic ring complexes of Nigeria. Journal of African Earth Sciences, 3, 229–251.CrossRefGoogle Scholar
Lindsley, D.H. (1991) Experimental studies of oxide minerals. Pp. 69–106 in: Oxide Minerals: Petrologic and Magnetic Significance (Lindsley, D.H., editor). Reviews in Mineralogy, 25, Mineralogical Society of America, Washington, D.C.CrossRefGoogle Scholar
MacChesny, J.B. and Muan, A. (1959) Studies in the system iron oxide–titanium oxide. American Mineralogist, 44, 926–945.Google Scholar
Rowins, S.M., Lalonde, A.E. and Cameron, E.M. (1991) Magmatic oxidation in the syenitic Murdock Creek intrusion, Kirkland Lake area, Ontario: evidence from the ferromagnesian silicates. Journal of Geology, 99, 395–414.CrossRefGoogle Scholar
Sakoma, E.M. (1986) A Comparative Study of the Geology and Mineralization in Diko (Niger State) and Kalato (Bauchi State). M.Sc. thesis, Ahmadu Bello University, Zaria, Nigeria.Google Scholar
Tattam, C.M. (1941) Wolfram investigations in the Kalato – Kogo dist rict (Tibchi – Yelli Hills). Geological Survey of Nigeria, Unpublished Report 702.Google Scholar
Von Knorring, O. and Fadipe, A. (1981) On the mineralogy and geochemistry of niobium and tantalum in some granite pegmatites and alkali granites of Africa. Bulletin de Minéralogie, 104, 496–507.CrossRefGoogle Scholar