Contributions to Mineralogy and Petrology

, Volume 56, Issue 1, pp 101–117 | Cite as

Differentiation of tholeiitic Karroo magma at Birds River, South Africa

  • H. V. Eales
  • J. A. van Robey


Strongly fractionated residua derived by partial crystallization of tholeiitic gabbroic magma were emplaced at shallow depth within sediments of the uppermost part of the Karroo succession. Field evidence suggests that these residua were tapped from a deeper intrusion during cauldron subsidence, but were subsequently engulfed by later intrusion of olivine gabbro on a much larger scale. Ferrogabbro and pegmatoids were produced by differentiation in place of the younger gabbro, but the older intrusion was already chemically evolved when emplacement occurred. The product, a quenched, porphyritic rock containing ferroaugite-ferrohedenbergite, fayalitic olivine and sodic plagioclase in a microcrystalline to glassy matrix, is chemically comparable with the coarse-grained, iron- and alkali-enriched facies of other well known differentiated bodies. Regular trends in the contents of Rb, Sr, Y, Zr and Nb correlate well with fractionation indices based on major-element chemistry.


Iron Crystallization Fractionation Olivine Mineral Resource 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bailey, E.B., Clough, C.T.: Tertiary and post-Tertiary geology of Mull, Loch Aline, and Oban. Mem. Geol. Surv. Scotland 1924Google Scholar
  2. Beswick, A.E.: An experimental study of alkali metal distributions in feldspars and micas. Geochim. Cosmochim. Acta 37, 183–208 (1973)Google Scholar
  3. Birks, L.S.: Electron probe microanalysis. New York: Wiley 1971Google Scholar
  4. Booth, P.W.K.: The Birds River gabbro complex. Unpubl. M. Sc. thesis, Rhodes University 1971Google Scholar
  5. Bottinga, Y., Weill, D.F.: The viscosity of magmatic silicate liquids. Am. J. Sci. 272, 438–475 (1972)Google Scholar
  6. Brown, G.M., Vincent, E.A.: Pyroxenes from the late stage of fractionation of the Skaergaard intrusion. J. Petrol. 4, 175–197 (1963)Google Scholar
  7. Bryan, W.B.: Morphology of quench crystals in submarine basalts. J. Geophys. Res. 77, 5812–5820 (1972)Google Scholar
  8. Chao, E.C.T., Fleischer, M.: Abundance of zirconium in igneous rocks. 21st Internat. Geol. Congr. Rept. 1, 106–131 (1960)Google Scholar
  9. Cox, K.C., Hornung, G.: Petrology of the Karroo basalts of Basutoland. Am. Mineralogist 51, 1414–1432 (1966)Google Scholar
  10. Du Toit, A.L.: Geological survey of Glen Gray and parts of Queenstown and Wodehouse. Ann. Rept. Cape Geological Commission 10, 97–140 (1905)Google Scholar
  11. Du Toit, A.L.: Geological survey of parts of the Stormbergen. Ann. Rept. Cape Geological Commission 16, 113–136 (1911)Google Scholar
  12. Du Toit, A.L.: The Karroo dolerites of South Africa. Trans. Geol. Soc. South Africa 23, 1–42 (1920)Google Scholar
  13. Eales, H.V.: The occurrence and geological significance of quartz paramorphs after tridymite. Trans. Geol. Soc. South Africa 77, 37–51 (1974)Google Scholar
  14. Eales, H.V., Booth, P.W.K.: The Birds River gabbro complex. Trans. Geol. Soc. South Africa 77, 1–15 (1974)Google Scholar
  15. Erlank, A.J.: The terrestrial abundance relationship between potassium and rubidium. In: Origin and distribution of the elements (L.H. Ahrens, ed.), pp. 871–888. New York: Pergamon 1968Google Scholar
  16. Erlank, A.J., Danchin, R.V., Fullard, C.C.: High K/Rb ratios in rocks from the Bushveld Igneous Complex, South Africa. Earth Planet. Sci. Lett. 4, 22–29 (1968)Google Scholar
  17. Erlank, A.J., Hofmeyr, P.K.: K/Rb and K/Cs ratios in Karroo dolerites from South Africa. J. Geophys. Res. 71, 5439–5445 (1966)Google Scholar
  18. Ewart, A., Taylor, S.R.: Trace element geochemistry of the rhyolitic volcanic rocks, Central North Island, New Zealand. Contrib. Mineral. Petrol. 22, 127–145 (1969)Google Scholar
  19. Gast, P.W.: Trace element fractionation and the origin of tholeiitic and alkaline magma types. Geochim. Cosmochim. Acta 32, 1057–1096 (1968)Google Scholar
  20. Goodman, R.J.: Distribution of Ga and Rb in coexisting groundmass and phenocryst phases of some basic volcanic rocks. Geochim. Cosmochim. Acta 36, 303–317 (1972)Google Scholar
  21. Gunn, B.M.: K/Rb and K/Ba ratios in Antarctic and New Zealand tholeiites and alkali basalts. J. Geophys. Res. 70, 6241–6247 (1965)Google Scholar
  22. Hamilton, D.L., Anderson, G.M.: Effects of water and oxygen pressures on the crystallization of basaltic magmas. In: Basalts (H.H. Hess, ed.), pp. 445–482. New York: Wiley 1967Google Scholar
  23. Heier, K.S., Compston, W., McDougall, I.: Thorium and uranium concentrations and the isotopic composition of strontium in the differentiated Tasmanian dolerites. Geochim. Cosmochim. Acta 29, 643–659 (1965)Google Scholar
  24. Hotz, P.E.: Petrology of granophyre in diabase near Dillsburg, Pennsylvania. Bull. Geol. Soc. Am. 64, 675–704 (1953)Google Scholar
  25. Jensen, B.B.: Patterns of trace element partitioning. Geochim. Cosmochim. Acta 37, 2227–2242 (1973)Google Scholar
  26. Lambert, R.St.J., Holland, J.G.: Yttrium geochemistry applied to petrogenesis utilising calciumyttrium relationships in minerals and rocks. Geochim. Cosmochim Acta 38, 1393–1414 (1974)Google Scholar
  27. Lambert, R.St.J., Holland, J.G., Owen, P.F.: Chemical petrology of a suite of lavas from Mount Ararat. Turkey. J. Geol. 82, 419–438 (1974)Google Scholar
  28. Maske, S.: The petrography of the Ingeli Mountain Range. Annals Univ. Stellenbosch 41, 1–109 (1966)Google Scholar
  29. McDougall, I.: Differentiation of the Tasmanian dolerites. Bull. Geol. Soc. Am. 73, 279–315 (1962)Google Scholar
  30. Muir, I.D., Tilley, C.E.: Basalts from the northern part of the Mid-Atlantic Ridge. J. Petrol. 7, 193–201 (1966)Google Scholar
  31. Murthy, V.R., Griffin, W.L.: K/Rb fractionation by plagioclase feldspars. Chem. Geol. 6, 265–271 (1970)Google Scholar
  32. Nockolds, S.R., Allen, R.: The geochemistry of some igneous rock series. Geochim. Cosmochim. Acta 5, 245–285 (1954)Google Scholar
  33. Norrish, K., Chappell, B.W.: X-ray fluorescence spectrography. In: Physical methods in determinative mineralogy (J. Zussman, ed.), pp. 161–214. New York: Academic Press 1967Google Scholar
  34. Norrish, K., Hutton, J.T.: An accurate X-ray spectrographic method for the analysis of a wide range of geological samples. Geochim. Cosmochim. Acta 33, 431–453 (1969)Google Scholar
  35. Osborn, E.F.: Role of oxygen pressure in the crystallization and differentiation of basaltic magma. Am J. Sci. 257, 609–647 (1959)Google Scholar
  36. Philpotts, J.A., Schnetzler, C.C.: Phenocryst-matrix partition coefficients for K, Rb, Sr and Ba, with applications to anorthosite and basalt genesis. Geochim. Cosmochim. Acta 34, 307–322 (1970)Google Scholar
  37. Poldervaart, A.: The petrology of the Elephant's Head dike and the New Amalfi sheet. Trans. Roy. Soc. South Africa 30, 85–119 (1944)Google Scholar
  38. Poldervaart, A.: The petrology of the Mount Arthur Complex (East Griqualand). Trans. Roy. Soc. South Africa 31, 83–110 (1946)Google Scholar
  39. Prinz, M.: Geochemistry of basaltic rocks. In: Basalts (H.H. Hess., ed.), pp. 271–323. New York: Wiley 1967Google Scholar
  40. Scholtz, D.L.: The magmatic nickeliferous ore deposits of East Griqualand and Pondoland, Trans. Geol. Soc. South Africa 39, 81–210 (1936)Google Scholar
  41. Sen, N., Nockolds, S.R., Alien, R.: Trace elements in minerals from rocks of the S. Californian batholith. Geochim. Cosmochim. Acta 16, 58–78 (1959)Google Scholar
  42. Shaw, H.R.: Viscosities of magmatic silicate liquids: an empirical method of prediction. Am. J. Sci. 272, 870–893 (1972)Google Scholar
  43. Siedner, G.: Geochemical features of a strongly fractionated alkali igneous suite. Geochim. Cosmochim. Acta 29, 113–137 (1965)Google Scholar
  44. Taubeneck, W.H.: An appraisal of some potassium-rubidium ratios in igneous rocks. J. Geophys. Res. 70, 475–478 (1965)Google Scholar
  45. Taylor, S.R.: The application of trace element data to problems in petrology. Phys. Chem. Earth 6, 133–214 (1965)Google Scholar
  46. Vincent, E.A.: Analysis by gravimetric and volumetric methods. In: Methods in geochemistry (A.A. Smales, L.R. Wager, eds.), pp. 33–80. New York: Interscience 1960Google Scholar
  47. Wager, L.R., Brown, G.M.: Layered igneous rocks. London: Oliver and Boyd 1968Google Scholar
  48. Walker, K.R.: The Palisades sill, New Jersey: a reinvetigation. Geol. Soc. Am. Spec. Paper 111 (1970)Google Scholar
  49. Walker, F., Poldervaart, A.: Karroo dolerites of the Union of South Africa. Bull. Geol. Soc. Am. 60, 591–706 (1949)Google Scholar

Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • H. V. Eales
    • 1
  • J. A. van Robey
    • 1
  1. 1.Department of GeologyRhodes UniversityGrahamstownSouth Africa

Personalised recommendations