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Crystallization of plagioclase, augite, and olivine in synthetic systems and in tholeiites

Published online by Cambridge University Press:  05 July 2018

G. M. Biggar
G. M. Biggar*
Affiliation:
Department of Geology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW
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Abstract

Experimental data from the system CaO-MgO-Na2O-Al2O3-SiO2 and from the system CaO-MgO-FeO-Al2O3-SiO2 are used to show the nature of the changes in composition, with temperature and with pressure, of liquids in equilibrium with augite, plagioclase, and olivine as MgO in the system CaO-MgO-Al2O3-SiO2 is partially replaced by FeO and as Na2O replaces CaO. As differentiation of tholeiitic basalts proceeds, Fe/Mg increases, Na/Ca increases, and normative hypersthene increases and these effects alter the solubilities, and hence the proportions of augite, plagioclase, and olivine which co-precipitate. In particular olivine becomes more soluble (less is precipitated) as Fe/Mg increases; plagioclase becomes more soluble but augite less soluble as Na/(Na + Ca) increases; augite also becomes less soluble as normative hypersthene increases, and as pressure is reduced during ascent.

Experimental data from remelted ocean tholeiites encounter the same equilibrium and are presented and compared with the data from synthetic systems.

Some natural examples of daughter liquids related to parents by crystallization of augite, plagioclase, olivine, are combined with the experimental data and with some model calculations to demonstrate that only a very limited range of proportions of augite : plagioclase: olivine (approximately 30 : 50 : 15 to 20 : 60: 20) produces daughter liquids which lie on the major element variation of the tholeiitic basalt series. Other proportions lead to daughter liquids which are not basalts. In the light of these restrictions, several recent publications are reinterpreted as examples of fractionation of augite, plagioclase, and olivine, rather than examples of partial melting. The recognition of the small effect that massive (50 to 83%) crystallization has on basaltic chemistry by contrast with the large effect that small accumulations of phenocrysts can have is particularly emphasized in this reinterpretation.

Comparisons and possible relationships are suggested between some low-K2O, low-TiO2 tholeiites; some calcic-, aphyric-, dykes of some tholeiitic provinces; some chilled margins of some layered intrusions; some basalts from Iceland, and some basalts from the ocean ridges.

Type
Research Article
Information
Mineralogical Magazine , Volume 47 , Issue 343 , June 1983 , pp. 161 - 176
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1983

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References

Bender, J. F., Hodges, F. N., and Bence, A. E. (1978) Earth Planet. Sci. hat. 41, 277–302.CrossRefGoogle Scholar
Biggar, G. M. (1981) Bull. Mineral. 104, 375–80.Google Scholar
Biggar, G. M. and Humphries, D. J. (1981) Mineral. Mag. 44, 309–14.CrossRefGoogle Scholar
Biggar, G. M.and Kadik, A. (1981) Progr. Exptl. Petrol. 5, 122–6.Google Scholar
Clague, D. A., and Bunch, T. E. (1976) J. Geophys. Res. 81, 4247–56.CrossRefGoogle Scholar
Cox, K. G. (1980) J. Petrol. 21, 629–50.CrossRefGoogle Scholar
Bell, J. D., and Pankhurst, R. J. (1979) The interpretation of igneous rocks. George Allen & Unwin, London. 450 pp.Google Scholar
Dixon, S., and Rutherford, M. J. (1979) Earth Planet. Sci. Lett. 45, 45–60.CrossRefGoogle Scholar
Drever, H. I., and Johnstone, R. (1966) J. Petrol. 7,414–20.CrossRefGoogle Scholar
Fisk, M. R., Schilling, J. G., and Sigurdsson, H. (1980) Contrib. Mineral. Petrol. 74, 361–74.CrossRefGoogle Scholar
Flower, M. F. J. (1980) Nature, 287, 530–2.CrossRefGoogle Scholar
Fujii, T., and Kushiro, I. (1977) Carnegie lnst. Wash. Yearb. 76, 461–4.Google Scholar
Hekinian, R., and Aumento, F. (1973) Marine Geol. 14, 47–72.CrossRefGoogle Scholar
Hoover, J. D. (1978) Carnegie lnst. Wash. Yearb. 77, 739– 43.Google Scholar
Humphries, D. J. (1975) Phase Equilibrium studies of some basalt-like compositions in the system CaO-MgOAl2O3– SiO2–Na2O-Fe-O2. Thesis Edinburgh University.Google Scholar
Humphries, D. J. (1981) Progr. Exptl. Petrol. 5, 133–4.Google Scholar
Humphries, D. J. and Biggar, G. M. (1981) Ibid. 5, 148–60.Google Scholar
Irvine, T. N. (1977) Carnegie lnst. Wash. Yearb. 76,454–61.Google Scholar
Jakobsson, S. P., Jonsson, J., and Shido, F. (1978) J. Petrol. 19, 669–705.CrossRefGoogle Scholar
Kushiro, I. (1973) Tectonophys. 17, 211–22.CrossRefGoogle Scholar
Le Roex, A. P., Erlank, A. J., and Needham, H. D. (1981) Contrib. Mineral. Petrol. 77, 24–37.CrossRefGoogle Scholar
Lindstrom, M. M., and Haskin, L. A. (1981) Geochem. Cosmochim. Ada, 45, 15–31.CrossRefGoogle Scholar
Maaløe, S. (1979) Iithos, 12, 59–72.Google Scholar
Morel, J. M., and Hekinian, R. (1980) Contrib. Mineral. Petrol. 72, 425–36.CrossRefGoogle Scholar
Mori, T., and Biggar, G. M. (1981) Prog. Exptl. Petrol. 5, 144–5, 147.Google Scholar
Noe-Nygaard, A., and Pedersen, A. K. (1974) Bull. Geol. Soc. Denmark 23, 175–90.Google Scholar
O'Hara, M. J. (1976) Prog. Exptl. Petrol. 3, 103–26.Google Scholar
O'Hara, M. J. and Matthews, R. E. (1981) J. Geol. Soc. 138, 237–77.CrossRefGoogle Scholar
Presnall, D. C. Dixon, J. R., O'Donnell, T. H., Brenner, N. L., Schrock, R. L., and Dycus, D. W. (1978) Contrib. Mineral. Petrol. 66, 1232–41.CrossRefGoogle Scholar
Presnall, D. C and Dixon, S. A. (1979) J. Petrol. 20, 3–35.CrossRefGoogle Scholar
Richardson, S. H. (1979) Geochim. Cosmochim. Acta, 43, 1433–41.CrossRefGoogle Scholar
Saunders, A. D., and Tarney, J. (1979) Ibid. 43, 555–72.Google Scholar
Sigurdsson, H., Schilling, J-G., and Meyer, P. S. (1978) J. Geophys. Res. 83, 3971–82.CrossRefGoogle Scholar
Sigvaldason, G. E. (1969) Contrib. Mineral. Petrol. 20, 357–70.CrossRefGoogle Scholar
Sigvaldason, G. E. (1974) J. Petrol. 15, 497–524.CrossRefGoogle Scholar
Skelhorn, R. R., Henderson, P., Walsh, J. N., and Longland, P. J. N. (1979) Scott. J. Geol. 15, 161–7.CrossRefGoogle Scholar
Staudigel, H., and Bryan, W. B. (1981) Contrib. Mineral. Petrol. 78, 225–62.Google Scholar
Stolper, E. (1980) Ibid. 74, 13–27.Google Scholar
McSween, H. Y., and Hays, J. F. (1979) Geochim. Cosmochim. Acta, 43, 589–602.CrossRefGoogle Scholar
Sun, S-S., Nesbitt, R. W. and Sharaskin, A. Y. (1979) Earth Planet. Sci. Lett. 44, 119–38.CrossRefGoogle Scholar
Takahashi, E. (1980) Carnegie lnst. Wash. Yearb. 79, 271–6.Google Scholar
Thompson, R. N. (1974) Contrib. Mineral. Petrol. 45, 317–41.CrossRefGoogle Scholar
Walker, D., Shibata, T., and De Long, S. E. (1979) Ibid. 70, 111–25.Google Scholar
Wood, D. A. (1978) J. Petrol. 19, 393–436.CrossRefGoogle Scholar