Three magmatic components in the 1973 eruption of Eldfell volcano, Iceland: Evidence from plagioclase crystal size distribution (CSD) and geochemistry (original) (raw)

Abstract

The 1973 eruption of Eldfell volcano, Iceland, appears to have been a short, simple event, but textural and geochemical evidence suggest that it may have had three different magmatic components. The first-erupted fissure magmas were chemically evolved, rich in plagioclase (∼18%) and had shallow, straight crystal size distribution (CSD) curves. The early lavas were less evolved chemically, had lower plagioclase contents (∼ 13%) and steeper, slightly concave up CSDs. The late lavas were chemically similar to the early lavas, but even richer in plagioclase than the initial magmas (∼ 24%) and had the steepest CSDs. There was no chemical evidence for plagioclase fractionation, but compositional diversity could be produced by clinopyroxene fractionation which must have occurred at depth. We propose that the eruption started with old, coarsened (Ostwald ripened) magma left over from a previous eruption, possibly that which produced Surtsey Island ten years earlier. The early flows may be mixtures of small amounts of this old magma with a new, low crystallinity, uncoarsened magma or a completely new magma. The late flows are another new magma from depth, chemically similar to the early flows, but which has grown plagioclase under increasing saturation (undercooling) perhaps during its ascent. All three magmatic components may have originated from the same parent, but had varying degrees of clinopyroxene fractionation, plagioclase nucleation and growth, and coarsening.

Loading...

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

References (31)

  1. Armienti, P., Pareschi, M.T., Innocenti, F., Pompilio, M., 1994. Effects of magma storage and ascent on the kinetics of crystal growth. The case of the 1991-93 Mt. Etna eruption. Contributions to Mineralogy and Petrology 115, 402-414.
  2. Bedard, L., Barnes, S.-J., 2002. A comparison of N-type semi-planar and coaxial INAA detectors for 33 geochemical reference sam- ples. Journal of Radioanalytical and Nuclear Chemistry 254, 485-497.
  3. Cashman, K.V., 1993. Relationship between plagioclase crystallisation and cooling rate in basaltic melts. Contributions to Mineralogy and Petrology 113, 126-142.
  4. Cashman, K.V., Marsh, B.D., 1988. Crystal size distribution (CSD) in rocks and the kinetics and dynamics of crystallisation II. Makaopuhi lava lake. Contributions to Mineralogy and Petrology 99, 292-305.
  5. Dehoff, R.T., 1991. A geometrically general theory of diffusion controlled coarsening. Acta Metallurgica et Materialia 39 (10), 2349-2360.
  6. Einarsson, T., 1974. The Heimaey Eruption in Words and Pictures. Heimskringla, Reykjavik.
  7. Einarsson, T., Björnsson, S., 1980. Earthquakes in Iceland. Jokull 29, 37-43.
  8. Furman, T., Frey, F.A., Park, K.-H., 1991. Chemical constraints on the petrogenesis of mildly alkaline lavas from Vestman- naeyjar, Iceland; the Eldfell (1973) and Surtsey (1963-1967) eruptions. Contributions to Mineralogy and Petrology 109 (1), 19-37.
  9. Gebrande, H., Miller, H., Einarsson, P., 1980. Seismic structure of Iceland along RRISP -profile-I. Journal of Geophysics- Zeitschrift Fur Geophysik 47 (1-3), 239-249.
  10. Greenough, J.D., Dostal, J., 1992. Cooling history and differentiation of a thick north mountain basalt flow (Nova-Scotia, Canada). Bulletin of Volcanology 55 (1-2), 63-73.
  11. Higgins, M.D., 1994. Determination of crystal morphology and size from bulk measurements on thin sections: numerical modelling. American Mineralogist 79, 113-119.
  12. Higgins, M.D., 1996. Magma dynamics beneath Kameni volcano, Greece, as revealed by crystal size and shape measurements. Journal of Volcanology and Geothermal Research 70, 37-48.
  13. Higgins, M.D., 1998. Origin of anorthosite by textural coarsening: quantitative measurements of a natural sequence of textural development. Journal of Petrology 39, 1307-1325.
  14. Higgins, M.D., 2000. Measurement of crystal size distributions. American Mineralogist 85, 1105-1116.
  15. Higgins, M.D., 2002a. Closure in crystal size distributions (CSD), verification of CSD calculations, and the significance of CSD fans. American Mineralogist 87, 171-175.
  16. Higgins, M.D., 2002b. A crystal size-distribution study of the Kiglapait layered mafic intrusion, Labrador, Canada: evidence for textural coarsening. Contributions to Mineralogy and Petrology 144, 314-330.
  17. Higgins, M.D., 2006a. Quantitative Textural Measurements in Igneous and Metamorphic Petrology. Cambridge University Press, Cam- bridge, UK.
  18. Higgins, M.D., 2006b. Use of appropriate diagrams to determine if crystal size distributions (CSD) are dominantly semi-logarithmic, lognormal or fractal (scale invariant). Journal of Volcanology and Geothermal Research 154, 8-16.
  19. Higgins, M.D., Roberge, J., 2003. Crystal size distribution (CSD) of plagioclase and amphibole from Soufriere Hills volcano, Mon- tserrat: evidence for dynamic crystallisation/textural coarsening cycles. Journal of Petrology 44, 1401-1411.
  20. Hunter, R.H., 1987. Textural equilibrium in layered igneous rocks. In: Parsons, I. (Ed.), Origins of Igneous Layering. D Reidel, pp. 473-503.
  21. Hunter, R.H., 1996. Textural development in cumulate rocks. In: Cawthorn, R.G. (Ed.), Layered Intrusions. Developments in Petrology. Elsevier, Amsterdam, pp. 77-101.
  22. Jakobsson, S.P., 1979. Petrology of recent basalts of the eastern volcanic zone, Iceland. Acta Naturalia Islandica 26, 1-103.
  23. Jakobsson, S.P., Pedersen, A.K., Rönsbo, J.G., Larsen, L.M., 1973. Petrology of Mugearite-Hawaiite: early extrusives in the 1973 Heimaey eruption, Iceland. Lithos 6, 203-214.
  24. Marsh, B.D., 1988. Crystal size distribution (CSD) in rocks and the kinetics and dynamics of crystallization I. Theory. Contributions to Mineralogy and Petrology 99, 277-291.
  25. Marsh, B.D., 1998. On the interpretation of crystal size distributions in magmatic systems. Journal of Petrology 39, 553-600.
  26. Mattsson, H., Höskuldsson, A., 2003. Geology of the Heimaey volcanic centre, south Iceland: early evolution of a central volcano in a propagating rift? Journal of Volcanology and Geothermal Research 127 (1-2), 55-71.
  27. Mattsson, H.B., Oskarsson, N., 2005. Petrogenesis of alkaline basalts at the tip of a propagating rift: evidence from the Heimaey volcanic centre, south Iceland. Journal of Volcanology and Geothermal Research 147 (3-4), 245-267.
  28. Philpotts, A.R., Carroll, M., Hill, J.M., 1996. Crystal-mush compac- tion and the origin of pegmatitic segregation sheets in a thick flood-basalt flow in the Mesozoic Hartford basin, Connecticut. Journal of Petrology 37 (4), 811-836.
  29. Rollinson, H.R., 1993. Using geochemical data: evaluation, presen- tation, interpretation. Geochemistry Series. Longman Scientific & Technical. J. Wiley & Sons, Harlow, UK. 352 pp.
  30. Sigmarsson, O., 1996. Short magma chamber residence time at an Icelandic volcano inferred from U-Series disequilibra. Nature 382, 440-442.
  31. Voorhees, P.W., 1992. Ostwald ripening of two-phase mixtures. Annual Review of Materials Science 22, 197-215.