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Maghemite in Icelandic basalts

Published online by Cambridge University Press:  05 July 2018

S. Steinthorsson ,
Ö. Helgason ,
M. B. Madsen ,
C. Bender Koch ,
M. D. Bentzon  and
S. Mørup
S. Steinthorsson
Affiliation:
Science Institute, University of Iceland, Dunhagi 3, IS-107, Reykjavík, Iceland
Ö. Helgason
Affiliation:
Physics Laboratory, H.C. Ørstedt Institute, DK-2100 Copenhagen Ø, Denmark
M. B. Madsen
Affiliation:
Science Institute, University of Iceland, Dunhagi 3, IS-107, Reykjavík, Iceland
C. Bender Koch
Affiliation:
Laboratory of Applied Physics, Technical University of Denmark, DK-2800, Lyngby, Denmark
M. D. Bentzon
Affiliation:
Laboratory of Applied Physics, Technical University of Denmark, DK-2800, Lyngby, Denmark
S. Mørup
Affiliation:
Laboratory of Applied Physics, Technical University of Denmark, DK-2800, Lyngby, Denmark
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Abstract

Curie temperatures indicating non-titaniferous magnetite are common in Icelandic basalts of all ages, especially Tertiary ones. Yet, microprobe analyses of such samples have shown high titanium in the magnetite. To resolve this paradox, and the mechanism at work, the magnetic mineral fraction of eight basalt samples with Js-T curves characteristic for pure magnetite was subjected to a multi-disciplinary analysis including Mössbauer spectroscopy and X-ray diffraction. In most of the samples titanium in the magnetite, as analysed with the microprobe, ranged between 16 and 28 wt.%, indicating submicroscopic solvus exsolution in the titanomagnetite, beyond the power of resolution for the microprobe. More unexpectedly in view of the reversible Js-T curves, Mössbauer spectroscopy showed appreciable proportion of maghemite in the magnetic fraction. A three-stage mechanism is proposed for the formation of the mineral assemblages observed: (1) limited high-temperature oxyexsolution; (2) solvus exsolution during low-temperature hydrothermal alteration; and (3) maghemitization of the magnetite. Finally, the maghemite may transform to hematite with time. It is concluded that maghemite is much more common in Icelandic rocks than hitherto believed.

Keywords

maghemitebasaltsMössbauer spectroscopyX-ray diffractionIceland
Type
Petrology and Geochemistry
Information
Mineralogical Magazine , Volume 56 , Issue 383 , June 1992 , pp. 185 - 199
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1992

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References

Ade-Hall, J. M., Palmer, H. C., and Hubbard, T. P. (1971) The magnetic and opaque petrological res-ponse of basalts to regional hydrothermal alteration. Geophys. J. astron Soc., 24, 137–74.CrossRefGoogle Scholar
Akimoto, S. and Kushiro, I. (1960) Natural occurrence of titanomaghemite and its relevance to the unstable magnetisation of rocks. J. Geomagn. Geoelect., 11, 94–110.CrossRefGoogle Scholar
Allan, J. E. M., Coey, J. M. D., Rosende, M. and Fabris, J. D. (1988) Magnetic properties of iron-rich oxysoils. Phys. Chem. Mineral., 15, 470–5.CrossRefGoogle Scholar
Allan, J. E. M., Coey, J. M. D., Rosende, M. and Fabris, J. D. Sanders, I. S., Schwertmann, U., Friedrich, G., and Wiechowski, A. (1989) An occurrence of a fully-oxidised natural titanomaghemite in basalt. Mineral. Mag., 53, 299–304.CrossRefGoogle Scholar
Aragon, R. and Honig, J. M. (1988) Mean-field model of the Verwey transition in magnetite. Phys. Rev., B37, 209-18.CrossRefGoogle Scholar
Basta, E. Z. (1960) Natural and synthetic titanomagne-tites (the system Fe304-Fe2TiO4-FeTiO3). Neues Jahrb. Mineral. Abh., 94, 1017–48.Google Scholar
Becker, H. (1980) Magnetic anomalies (DZ) in NE-Iceland and their interpretation based on rock-magnetic investigations. J. Geophys., 47, 43–56.Google Scholar
Carmichael, C. M. (1961) The magnetic properties of ilminite-hematite crystals. Proc. Roy. Soc. London, Ser. A, 263, 508–30.Google Scholar
Carmichael, I. S. E. (1967) The iron-titanium oxides of salic volcanic rocks ard their associated ferromagne-sian silicates, Contrib. Mineral Petrol., 14, 36454.Google Scholar
Elmore, W. C. (1938) Ferromagnetic colloid for studying magnetic structures. Phys. Rev., 54, 309–10.CrossRefGoogle Scholar
Fridleifsson, I. B. and Kristjansson, L. (1972) The Stardalur magnetic anomaly, SW-Iceland. JOkull, 22, 69–78.Google Scholar
Haggerty, S. E. (1976) Oxidation of opaque mineral oxides in basalts. In Reviews in Mineralogy, 3. Oxide Minerals. (Rumble, III, D., ed.). Mineralogical Society of America, Hg-l-Hg-98.Google Scholar
Haggerty, S. E. and Baker, I. (1967) The alteration of olivine in basaltic and associated lavas. Part 1: High tempera-ture alteration. Contrib. Mineral. Petrol., 16, 233–57.CrossRefGoogle Scholar
Häggström, L., Annersten, H., Ericsson, T., Wäippling, R., Karner, W., and Bjarman, S. (1978) Magnetic dipolar and electric quadrupolar effect on the M6ss-bauer spectra of magnetite above the Verwey transition. Hyperf. Int., 5, 201–14.CrossRefGoogle Scholar
Helgason, Ö., Steinthorsson, S., Madsen, M. B., and Mørup, S. (1990) On anomalously magnetic basalt lavas from Stardalur, Iceland. Ibid., 57, 2209-14.Google Scholar
Helgason, Ö., Steinthorsson, S., Madsen, M. B., and Mørup, S. Gunnlaugsson, H. P., Steinthorsson, S., and Mcrup, S. (1992) High temperature stability of maghemite in partially oxidised basalt lava. Ibid. (in press).CrossRefGoogle Scholar
Imsland, P. (1984) Petrology, Mineralogy and Evolution of the Jan May en Magma System. Soc. Sci. Isl., Reykjavik, 332 pp.Google Scholar
Irving, E. (1970) The mid-Atlantic ridge at 45°N XVI. Oxidation and magnetic properties of basalt. Review and discussion. Can. J. Earth Sci., 7, 1528–38.CrossRefGoogle Scholar
Kristjansson, L. (1985) Magnetic and thermal effects of dike intrusions in Iceland—-locations and paleomag-netic characteristics of samples. J. Geophys. Res., 90, 10129–35.CrossRefGoogle Scholar
Jensen, A. (1968) Opaque minerals in the Precambrian plutonic rocks of Bornholm and their relation to the development of these rocks. Medd. Dansk. Geol. Foren., 18, 79–96.Google Scholar
Levi, S., Audunsson, H., Duncan, R. A. Kristjansson, L., Grillot, P. V., and Jakobsson, S. P. (1990) Late Pleistocene geomagnetic excursion in Icelandic lavas: Confirmation of the Laschamp excursion. Earth Planet. Sci., Letters, 96, 443-57.CrossRefGoogle Scholar
Lindsley, D. H. (1976a) The crystal chemistry and structure of oxide minerals as exemplified by the Fe-Ti oxides. In Reviews in Mineralogy, 3. Oxide Minerals. (Rumble, III, D., ed.). Mineralogical Society of America, L-I-L-60.CrossRefGoogle Scholar
Lindsley, D. H. (1976b) Experimental studies of oxide minerals. In Reviews in Mineralogy, 3. Oxide Minerals. (Rumble, III, D., ed.). Mineralogy Society of America, L-61-L-88.CrossRefGoogle Scholar
Madsen, M. B., Mørup, S., and Knudsen, J. M. (1989) Extraterrestrial magnetite studied by M6ssbauer spectroscopy. Hyperf Int., 50, 659–66.CrossRefGoogle Scholar
Mørup, S., Saksager, O., Madsen, M. B., Bentzon, M. D. and Koch, C. J. W. (1990) Weathering of basalt in an arctic climate. Ibid., 57, 2269-74.Google Scholar
O'Reilly, W. (1984) Rock and Mineral Magnetism. Chapman and Hall, New York, 220 pp.CrossRefGoogle Scholar
Oskarsson, N., Sigvaldason, G. E., and Steinthorsson, S. (1982) A dynamic model of rift zone petrogenesis and the regional petrology of Iceland. J. Petrol., 23, 28–74.CrossRefGoogle Scholar
Ramdani, A., Steinmetz, J., Gleitzer, C., Coey, J. M. D., Friedt, J. M. (1987) Pertubation de l'echange electronique rapide par les lacunes cation-iques dans Fe3-xO4 (x ≤ 0.09). J. Phys. Chem. Solids, 48, 217–28.CrossRefGoogle Scholar
Ramdohr, P. (1953) Ulvöspinel and its significance in titaniferous iron ores. Econ. Geol., 48, 677–88.CrossRefGoogle Scholar
Readman, P. W. and O'Reilly, W. (1972) Magnetic properties of oxidised (cation-deficient) titanomagne-tites (Fe, Ti, [])304. Geomag. Geoelect., 24, 69–90.CrossRefGoogle Scholar
Rumble, D. (1976) Oxide minerals in metamorphic rocks. In Reviews in Mineralogy, Oxide Minerals. (Rumble, III, D., ed.). Mineralogical Society of America, R-I-R-24.Google Scholar
Sato, M. and Wright, T. L. (1966) Oxygen fugacities directly measured in magmatic gases. Science, 153, 1103–5.CrossRefGoogle Scholar
Smith, B. M. (1987) Consequences of the maghemitisa-tion on the magnetic properties of submarine basalts: Synthesis of previous works and results concerning basement rocks from mainly D.S.D.P. Legs. 51 and 52. Phys. Earth Planet. Int., 46, 206–26.CrossRefGoogle Scholar
Steinthorsson, S. and Sigvaldason, G. E. (1971) Report on petrological investigations at Stardalur (in Icelandic). Sci. Inst., University of Iceland (Mimeographed).Google Scholar
Steinthorsson, S. and Sigvaldason, G. E. Kristjansson, L., and Sigvaldason, G. E. (1971) Studies of drill cores from an unusual magnetic high in SW-Iceland. (Abstr.). 1st Eur. Earth Planet. Phys. Colloq., Reading, England.Google Scholar
Steinthorsson, S. and Sigvaldason, G. E. Oskarsson, N., Arnorsson, S., and Gunlaugsson, E. (1987) In Chemical Transport in Metasomatic Processes. (Helgeson, H. C., ed.). D. Reidel Publ. Co., 355-87.Google Scholar
Tanaka, H. and Kono, M. (1987) M6ssbauer spectra on titanomagnetite: A reappraisal. J. Geomag. Geo-electr., 39, 463–75.CrossRefGoogle Scholar
Walker, G. P. L. (1960) Zeolite zones and dike distributions in relation to the structure of the basalts of eastern Iceland. J. Geol., 68, 515–28.CrossRefGoogle Scholar
Watkins, N. D. and Haggerty, S. E. (1967) Primary oxidation and petrogenesis in a single lava. Contrib. Mineral. Petrol., 15, 251–71.CrossRefGoogle Scholar