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Geochemistry and petrogenesis of a nepheline syenite-carbonatite complex from the Sudan

Published online by Cambridge University Press:  01 May 2009

N. B. W. Harris ,
A. E. R. O. Mohammed  and
M. Z. Shaddad
N. B. W. Harris
Affiliation:
Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, England
A. E. R. O. Mohammed
Affiliation:
Department of Geology, University of Khartoum, Khartoum, Sudan
M. Z. Shaddad
Affiliation:
Department of Geology, University of Khartoum, Khartoum, Sudan
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Summary

Jabal Dumbeir is a nepheline syenite-carbonatite complex of Cambrian age (550 ± 87 Ma). The earliest igneous event of the complex was the intrusion of a phlogopite-sodalite nepheline syenite (ditroite) which was derived from the partial melting of the upper mantle. K, CO2 and F-rich volatiles metasomatise both the ditroite and the gneissic country rock which results in an orthoclase-rich undersaturated syenite (orthoclasite). Carbonatitic breccias and sovite dykes were subsequently emplaced carrying high levels of F, REE, Y and Th with extremely high LREE/HREE ratios (CeN/YbN = 64 ± 8). Such carbonatiticmagmas may be derived by partial melting of an LREE-enriched upper mantle. Hydrothermal emplacement of fluorite-quartz veins represent the final phase of igneous activity and these carry high levels of REE, Y, Th and U. Their emplacement was strongly controlled by a system of NNE strike-slip faults which have been reactivated in recent times.

Type
Articles
Information
Geological Magazine , Volume 120 , Issue 2 , March 1983 , pp. 115 - 127
Copyright
Copyright © Cambridge University Press 1983

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References

REFERENCES

Balashov, Yu. A. & Pozharitskaya, L. K. 1968. Factors governing the behaviour of rare earth elements in the carbonatite process. Geochem. int. 271–89.Google Scholar
Bell, K. & Powell, J. L. 1969. Sr isotopic studies of alkalic rocks: the K-rich lavas of Birunga and Toro-Ankole regions, east and central Equatorial Africa. J. Petrology 10, 536–72.CrossRefGoogle Scholar
Boettcher, A. L. & O'Neil, J. R. 1980. Stable isotope, chemical and petrographic studies of high pressure amphiboles and micas; evidence for metasomatism in the mantle source regions of alkali basalts and kimberlites. Am. J. Sci. 280 A, 594–621.Google Scholar
Brueckner, H. K. & Rex, D. C. 1980. K-A and Rb-Sr geochronology and Sr isotopic study of the Alnö complex, northeastern Sweden. Lithos 13, 111–19.CrossRefGoogle Scholar
Cortini, M. & Hermes, O. D. 1981. Sr isotopic evidence for a multi-source origin of the K magmas in the Neopolitan area (South Italy). Contr. Miner. Petr. 77, 47–55.CrossRefGoogle Scholar
Cullers, R. L. & Medaris, L G. 1977. REE in carbonatite and cogenetic alkaline rocks. Examples from Searbrook Lake and Callander Bay, Ontario. Contr. Miner. Petr. 65, 143–53.CrossRefGoogle Scholar
Deans, T., Sukheswala, R. N., Sethur, S. F. & Viladkar, S. G. 1972. Metasomatic feldspar rocks (K-fenites) associated with the fluorite deposits of carbonatites of Amba Dongar, Gujarat, India. Trans. Instn Min. Metall. Sect. B, 81, 1–9.Google Scholar
Eby, G. N. 1975. Abundance and distribution of the REE and Y in the rocks and minerals of the Oka carbonatite complex, Quebec. Geochim. cosmochim. Acta 39, 597–620.CrossRefGoogle Scholar
Ellis, A. J. 1979. Geochemistry of some explored geothermal systems. In Ore Deposits (ed. Barnes, H. L.), pp. 465–514. New York: Holt, Reinhart and Winston Inc.Google Scholar
Ellis, A. J. & Mahon, W. A. J. 1967. Hydrothermal systems and experimental host water/rock interactions. Geochim. cosmochim. Acta 31, 519–38.CrossRefGoogle Scholar
El Sharkawi, M. A. & El Raba'a, S. M. 1973. First record of carbonatite in Sudan. In Second Conference of African Geology (ed. T., Hailu), pp. 129–35. Addis Abba: Geol. Soc. Africa.Google Scholar
Fuge, R. 1976. The automated calorimetric determination of fluorine and chlorine in geological samples. Chem. Geol. 17, 37–43.CrossRefGoogle Scholar
Flynn, R. T. & Burnham, C. W. 1978. An experimental determination of rare element partition coefficients between a chloride containing vapour phase and silicate melts. Geochim. cosmochim. Acta 42, 685–701.CrossRefGoogle Scholar
Gerasimovsky, V. I., Balashov, Yu. A. & Karpushina, V. A. 1972. Geochemistry of the REE in the extrusive rocks of the east African rift zone. Geochem. int. 9, 305–19.Google Scholar
Hamilton, D. L., Freestone, I. C., Dawson, J. B. & Donaldson, C. J. 1979. Origin of carbonatites by liquid immiscibility. Nature, Lond. 279, 52–4.CrossRefGoogle Scholar
Hamilton, D. L. & Mackenzie, W. S. 1965. Phase equilibrium studies in the system NaAlSiO4- KAlSiO4-SiO2-H2O. Mineralog. Mag. 34, 214–31.Google Scholar
Hansen, K. 1981. Systematic Sr-isotopic variation in alkaline rocks from West Greenland. Lithos 14, 183–89.CrossRefGoogle Scholar
Harris, N. B. W. 1981. The role of fluorine and chlorine in the petrogenesis of a peralkaline complex from Saudi Arabia. Chem. Geol. 31, 303–10.CrossRefGoogle Scholar
Harris, N. B. W. 1982. The petrogenesis of alkaline intrusives from Arabia and North-East Africa and their implications for within-plate magmatism. Tectonophysics 83, 243–58.CrossRefGoogle Scholar
Harrison, W. J. 1981. Partitioning of REE between minerals and coexisting melts during partial melting of a garnet lherzolite. Am. Miner. 66, 242–59.Google Scholar
Heinrich, E. W. & Moore, D. G. 1970. Metasomatic potash feldspar rocks associated with igneous alkalic complexes. Can. Mineral. 10, 571–24.Google Scholar
Koster van Groos, A. F. & Wyllie, P. J. 1969. Melting relationships in the system NaAlSiO8-NaCl-H2O at l k'bar pressure with petrological applications. J. Geol. 77, 581–605.CrossRefGoogle Scholar
Kuehner, S. M., Edgar, A. D. & Arima, M. 1981. Petrogenesis of the ultrapotassic rocks from the leucite hill, Wyoming. Am. Miner. 66, 633–77.Google Scholar
Larsen, L. M. 1979. Distribution of REE and other trace elements between phenocrysts and peralkaline undersaturated magmas, exemplified by rocks from the Gardar igneous province, S. Greenland. Lithos 2, 303–15.CrossRefGoogle Scholar
Leake, B. E. 1978. Nomenclature of amphiboles. Mineralog. Mag. 42, 533–63.CrossRefGoogle Scholar
Mineyev, D. A. 1963. Geochemical differentiation of the rare earths. Geochem. int. 1129–49.Google Scholar
Mitchell, R. H. & Bell, K. 1976. REE geochemistry of potassic lavas from the Birunga and Toro-Ankole regions of Uganda, Africa. Contr. Miner. Petr. 58, 293–303.CrossRefGoogle Scholar
Mitchell, R. H. & Brunfelt, A. O. 1975. REE geochemistry of the Fen alkaline complex, Norway. Contr. Miner. Petr. 52, 247–59.CrossRefGoogle Scholar
Mitchell, R. H. & Crocket, J. H. 1972. Isotopic exchange of Sr in rocks of the Fen alkaline complex, southern Norway. J. Petr. 13, 83–97.CrossRefGoogle Scholar
Mysen, B. O. 1975. Solubility of volatiles in silicate melts at high pressures and temperatures. Yb. Carnegie Instn Wash. 74, 454–68.Google Scholar
Mysen, B. O. 1981. REE partitioning between minerals and (CO2 and H2O) vapour as a function of pressure, temperature and vapour composition. Yb. Carnegie Instn Wash. 80, 347–9.Google Scholar
Mysen, B. O. & Boettcher, A. L. 1975. Melting of a hydrous mantle: 2. Geochemistry of crystals and liquids by anatexis of mantle peridotite at high pressures and temperatures as a function of controlled activities of water, hydrogen and carbon dioxide. J. Petr. 16, 549–93.CrossRefGoogle Scholar
Potts, P. J., Thorpe, O. W. & Watson, J. S. 1981. Determination of the REE abundances in 29 international rock standards by Instrumental Neutron Activation Analysis: a critical appraisal of calibration errors. Chem. Geol. 34, 331–52.CrossRefGoogle Scholar
Qureshi, I. R. & Sadig, A. A. 1967. Earthquakes and associated faulting in Central Sudan. Nature, Lond. 215, 263–65.CrossRefGoogle Scholar
Roberson, C. E. & Barnes, R. B. 1978. Stability of F complexes with silica and its distribution in natural water systems. Chem. Geol. 21, 239–56.CrossRefGoogle Scholar
Sutherland, D. S. 1965 a. Nomenclature of the potassic-feldspathic rocks associated with carbonatites. Bull. geol. Soc. Am. 76, 1409–12.CrossRefGoogle Scholar
Sutherland, D. S. 1965 b. Potash trachytes and ultrapotassic rocks associated with the carbonatite complex of the Toror Hills, Uganda. Mineralog. Mag. 35, 363–78.Google Scholar
Sweatman, T. R. & Long, J. V. P. 1969. Quantitative electron-probe microanalysis of rock-forming minerals. J. Petr. 10, 332–79.CrossRefGoogle Scholar
Wendlandt, R. F. & Harrison, W. J. 1979. Rare element partition between immiscible carbonate and silicate liquids and CO2 vapor: Results and implications for the formation of light REE enriched rocks. Contr. Miner. Petr. 69, 409–19.CrossRefGoogle Scholar
Wyllie, P.J. 1977. Mantle-fluid compositions buffered by carbonates in peridotite-CO2-H2O. J. Geol. 85, 187–207.CrossRefGoogle Scholar
Wyllie, P. J. & Huang, W. L. 1976. Carbonation and melting reactions in the system CaOMgO-SiO2-CO2. Contr. Miner. Petr. 54, 79–107.CrossRefGoogle Scholar