Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-27T07:12:47.123Z Has data issue: false hasContentIssue false
  • English
  • Français

Petrology and geochemistry of the alkaline intrusion, Jombo Hill, Kenya

Published online by Cambridge University Press:  01 May 2009

I. O. Nyambok
I. O. Nyambok
Affiliation:
University of Nairobi, Department of Geology, Box 30197, Nairobi, Kenya
Get access Rights & Permissions [Opens in a new window]

Summary

The field occurrence and the known immiscibility between silicate and carbonate melts suggest the Jombo alkaline intrusion and Mrima carbonatite intrusion have come from the same magmatic source. However, only the ijolite series apparently originated from a magma body at Jombo hill intrusion, while the feldspathoidal syenite series appears to have resulted from metasomatic alteration of the country rock-sandstone. The K/Rb ratios seem to indicate a mantle origin for the ijolites and a crustal one for the feldspathoidal syenites. The feldspathoidal syenite series were presumably formed by alkali metasomatism, resulting from magmatic fluid infiltration through intergranular movement. It is suggested that the partitioning of K and Na components in the metasomatizing fluid and solid feldspar phases at different temperatures, was the cause of two rock types – albite nepheline syenite and orthoclase nepheline syenite.

Type
Articles
Information
Geological Magazine , Volume 117 , Issue 4 , July 1980 , pp. 327 - 338
Copyright
Copyright © Cambridge University Press 1980

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

Bailey, D. K. 1969. The stability of acmite in the presence of H2O. Am. J. Sci. 267 (Schairer volume), 1–16.Google Scholar
Bailey, D. K. 1974. Nephelinites and ijolites. In The Alkaline Rocks (ed. Sørensen, H.), pp. 53–66. London: John Wiley.Google Scholar
Baker, B. H. 1953. The alkaline complex of Jombo. In Geology of the Mombasa-Kwale area (Caswell, P. V.). Kenya Geol. Surv. Rep. no. 24, pp. 32–48.Google Scholar
Barber, C. 1974. The geochemistry of carbonatites and related rocks from two carbonatite complexes, South Nyanza, Kenya. Lithos 7 (1), 53–63.Google Scholar
Bowen, N. L. & Tuttle, O. F. 1950. The system NaAlSi3O8–KAlSi3O8–H2O. J. Geol. 58, 489–511.Google Scholar
Brown, F. H. 1970. Zoning in some volcanic nephelines. Am. Miner. 55, 1670–80.Google Scholar
Coetzee, G. L. & Edwards, C. B. 1959. The Mrima hill carbonatite, Coast Province, Kenya. Trans. geol. Soc. S. Africa 62, 373–95.Google Scholar
Currie, K. L. 1971. A study of potash fenitization around the Brent Crater, Ontario: A Paleozoic alkaline complex. Can. J. Earth Sci. 8 (5), 481–97.Google Scholar
Currie, K. L. & Ferguson, J. 1971. A study of fenitization around the alkaline carbonatite complex at Callander Bay, Ontario, Canada. Can. J. Earth Sci. 8, 498–517.Google Scholar
Eckerman, H. von. 1948. The alkaline district of Alnö Island. Sveriges Geol. Undersökning, Ser. Ca, no. 36.Google Scholar
Eitel, W. 1954. The Physical Chemistry of the Silicates. University of Chicago Press.Google Scholar
Ekström, T. K. 1972. Coexisting scapolite and plagioclase from two iron formations in northern Sweden. Lithos 5, 175–85.Google Scholar
Gorbatschev, R. 1960. On the alkali rocks of Almunge: A preliminary report on a new survey. Bull. Geol. Uppsala 39, 1–69.Google Scholar
Gregory, J. W. 1900. The nepheline syenite and camptonitic dykes intrusive in the coast series. Q. Jl geol. Soc. 56, 223–9.Google Scholar
Harris, P. M. 1965. Pandaite from the Mrima Hill niobium deposit, Kenya. Mineralog. Mag. 35, 277–90.Google Scholar
Hobley, C. W. 1895. Upon a visit to Tsavo and the Taita highlands. Geogr. J. 5, 559–61.CrossRefGoogle Scholar
King, B. C. 1965. Petrogenesis of the alkaline igneous suites of the volcanic and intrusive centres of eastern Uganda. J. Petrology 6, 67–100.CrossRefGoogle Scholar
King, B. C., Le Bas, M. J. & Sutherland, D. S. 1972. The history of the alkaline volcanoes and intrusive complexes of eastern Uganda and western Kenya. J. Geol. Soc. 128, 173–205.Google Scholar
Koster van Groos, A. F. 1975. The effect of high CO2 pressure on alkalic rocks and its bearing on the formation of alkalic ultrabasic rocks and the associated carbonatites. Am. J. Sci. 275, 163–85.CrossRefGoogle Scholar
Koster van Groos, A. F. & Wyllie, P. J. 1973. Liquid immiscibility in the join NaAlSi3O8-CaAlSi2O8-H2O. Am. J. Sci. 273, 465–87.Google Scholar
Larsen, L. M. & Steenfelt, A. Alkali loss and retention in an iron-rich peralkaline phonolite dyke from the Gardar province, South Greenland. Lithos 7, 81–90.Google Scholar
McCall, G. J. H. 1963. A reconsideration of certain aspects of the Rangwa and Ruri carbonatite complexes in western Kenya. Geol. Mag. 100, 181–5.Google Scholar
McKinnon Wood, M. 1930. Reports on the geological collection from the coastlands of Kenya. Mon. Geol. Dept, Hunterian Museum, Glasgow University, IV.Google Scholar
Mysen, B. O. 1976. The role of volatiles in silicate melts; solubility of carbon dioxide and water in feldspar, pyroxene and feldspathoid melts to 30 kb and 1625 °C. Am. J. Sci. 276, 969–96.Google Scholar
Nyambok, I. 1976. Fenitization around an alkaline intrusion: A study of Jombo hill, Kenya. Kenya Geographer 2 (1), 45–57.Google Scholar
Nyambok, I. O. & Lindqvist, B. 1978. Microprobe and X-ray diffraction analyses of the major minerals from Jombo hill alkaline rocks, Kenya. UUDMP Research Rep. no. 9.Google Scholar
Orville, P. M. 1972. Plagioclase cation exchange equilibria with aqueous chloride solutions; results at 700 °C and 2000 bars in the presence of quartz. Am. J. Sci. 272, 870–93.Google Scholar
Peng, C. C. J. 1970. Intergranular albite in some granites and syenites of Hong Kong. Am. Mineral. 55, 270–82.Google Scholar
Pulfrey, W. 1949. Ijolitic rocks near Homa Bay, western Kenya. Q. Jl geol. Soc. 105, 425–59.Google Scholar
Pulfrey, W. 1954. Alkaline syenites at Ruri, South Nyanza, Kenya. Geol. Mag. 91, 209–19.Google Scholar
Rankin, A. H. & Le Bas, M. J. 1974. Liquid immiscibility between silicate and carbonate melts in naturally occurring ijolite magma. Nature, Lond. 250, no. 5463, 206–9.Google Scholar
Rock, N. M. S. 1976. Petrogenetic significance of some new xenolithic alkaline rocks from East Africa. Mineralog. Mag. 40, 611–25.CrossRefGoogle Scholar
Shaw, D. M. 1960. The geochemistry of scapolite II. J. Petrology 1, part 2, 2161–85.Google Scholar
Sigurdsson, H. 1971. Feldspar relations in a composite magma. Lithos 4, 231–8.Google Scholar
Sørensen, H. 1974. Alkali syenite, feldspathoidal syenites and related lavas. In The Alkaline Rocks (ed. Sørensen, H.) pp. 22–57. London: John Wiley.Google Scholar
Sutherland, D. S. 1969. Sodic amphiboles and pyroxenes from fenites in east Africa. Contr. Miner. Petrol. 24 (2), 114–35.CrossRefGoogle Scholar