Contributions to Mineralogy and Petrology

, Volume 63, Issue 2, pp 149–160 | Cite as

Clinopyroxene composition in mafic lavas from different tectonic settings

  • Euan G. Nisbet
  • Julian A. Pearce


Many metamorphosed and weathered basalts contain fresh clinopyroxene crystals set in an altered groundmass. Microprobe analysis of these relict grains can be used to identify the magma type of the host lava. Statistical discrimination of clinopyroxenes from known magma types provides a test of the effectiveness of this method, showing that any attempt to classify an unknown clinopyroxene as either an ocean-floor basalt, a volcanic arc basalt, a within plate tholeiite or a within plate alkali basalt magma type should have a 70% chance of success. Identification of within plate alkali basalts is most likely to be successful because their pyroxenes characteristically have high Na and Ti and low Si contents. Within plate tholeiites can usually be distinguished from volcanic arc basalts because their pyroxenes contain more Ti, Fe and Mn. However, neither of these last two magma types can be easily distinguished from ocean floor basalts on the basis of pyroxene analyses. Diagrams of pyroxene composition based on discriminant functions and on Na2O vs MnO vs TiO2, SiO2 vs TiO2 and SiO2 vs Al2O3 provide the basis for visual discrimination. The discrimination achieved is mainly due to differences in the bulk chemistry of the host magmas and in the partitioning of cations into the pyroxene lattice; differences in temperature and crystallization histroy of the magmas are of lesser, but nevertheless finite, importance. Application of this technique to pyroxenes in metabasalts from Othris, Greece gave results consistent with, but more ambiguous than, results obtained from immobile trace element studies.


TiO2 Na2O Ocean Floor Alkali Basalt Statistical Discrimination 
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  1. Barberi, F., Bizouard, H., Varet, J.: Nature of the clinopyroxene and iron enrichment in alkalic and transitional basaltic magmas. Contrib. Mineral. Petrol. 33, 93–107 (1971)Google Scholar
  2. Bickle, M.J., Nisbet, E.G.: The oceanic affinities of some alpine mafic rocks based on their Ti-Zr-Y contents. J. Geol. Soc. 128, 267–271 (1972)Google Scholar
  3. Carmichael, I.S.E., Nichols, J., Smith, A.L.: Silica activity in igneous rocks. Am. Mineralogist 55, 246–263 (1970)Google Scholar
  4. Chayes, F., Welde, D.: On distinguishing basaltic lavas of circum-oceanic and ocean-island type by means of discriminant functions. Am. J. Sci. 263, 206–222 (1965)Google Scholar
  5. Coombs, D.S.: Trends and affinities of basaltic magmas and pyroxenes as illustrated on the diopside-olivine-silica diagram. Mineral. Soc. Am. sp. paper 1, 227–250 (1963)Google Scholar
  6. Donaldson, C.H., Usselman, T.M., Willians, R.J. Lofgren, G.E.: Experimental modelling of the cooling history of Apollo 12 olivine basalts. Proc. Lunar Sci. Conf. 6th 843–869 (1975)Google Scholar
  7. Garcia, M.: Clinopyroxene composition, an indicator of magma type in altered volcanic rocks. Geol. Soc. Am. Abstracts with Program, 7, No. 7, pp. 1082–1083 (1975)Google Scholar
  8. Gibb, F.G.F.: The zoned pyroxenes of the Shiant Isles Sill, Scotland. J. Petrol. 4, 203–230 (1973)Google Scholar
  9. Glassley, W.E.: Geochemistry and tectonics of the Crescent volcanic rocks, Olympic Peninsula Washington. Geol. Soc. Am. Bull. 85, 785–794 (1974)Google Scholar
  10. Hess, P.C.: Polymer model of silicate melts. Geochim. Cosmochim. Acta 35, 289–306 (1971)Google Scholar
  11. Hynes, A.J.: Notes on the petrology of some ophiolites. Othris mountains, Greece. Contrib. Mineral. Petrol. 46, 233–239 (1974)Google Scholar
  12. Kushiro, I.: Si-Al relation in clinopyroxenes from igneous rocks. Am. J. Sci. 258, 548–554 (1960)Google Scholar
  13. Le Bas, M.J.: The role of aluminium in igneous clinopyroxenes with relation to their parentage. Am. J. Sci. 260, 267–288 (1962)Google Scholar
  14. Lofgren, G., Donaldson, C.H., Williams, R.J., Mullins, O., Usselman, T.M.: Experimentally reproduced textures and mineral chemistry of Apollo 15 quartz normative basalts. Proc. 5th Lunar Conf., suppl. 5 Geochim. Cosmochim. Acta 1, 549–567 (1974)Google Scholar
  15. Nisbet, E.G.: The geology of the Neraida area, Othris mountains, Greece. Unpubl. Ph. D thesis, Univ. of Cambridge (1974)Google Scholar
  16. Nisbet, E.G., Cameron, W.E.: Igneous activity at the birth of a Mesozoic ocean — II (in preparation)Google Scholar
  17. Pearce, J.A.: Statistical analysis of major element patterns in basalts. J. Petrol. 17, 15–43 (1976)Google Scholar
  18. Pearce, J.A., Cann, J.R.: Tectonic setting of basic volcanic rocks determined using trace element analyses. Earth Planet. Sci. Lett. 19, 290–300 (1973)Google Scholar
  19. Smith, A.G., Hynes, A.J., Menzies, M., Nisbet, E.G., Price, I., Welland, M.J.P., Ferriere, J.: The stratigraphy of the Othris Mountains, Eastern Central Greece: a deformed Mesozoic Continental margin. Eclogae Geol. Helv. 68, 463–481 (1975)Google Scholar
  20. Vallance, T.J.: Pyroxenes and the basalt-spilite relation, In: Spilites and spilitic rocks (G.C. Amstutz, ed.), pp. 59–68. Berlin-Heidelberg-New York: Springer 1974Google Scholar
  21. Verhoogen, J.: Distribution of titanium between silicates and oxides in igneous rocks. Am. J. Sci. 260, 211–220 (1962)Google Scholar
  22. Watson, E.B.: Two-liquid partition coefficients: experimental data and geochemical implications. Contrib. Mineral. Petrol. 56, 119–134 (1976)Google Scholar

Copyright information

© Springer-Verlag 1977

Authors and Affiliations

  • Euan G. Nisbet
    • 1
  • Julian A. Pearce
    • 2
  1. 1.Department of Geology and MineralogyOxfordUK
  2. 2.Department of Earth Sciences Open UniversityMilton KeynesUK

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