Hostname: page-component-586b7cd67f-tf8b9 Total loading time: 0 Render date: 2024-11-25T18:17:48.288Z Has data issue: false hasContentIssue false
  • English
  • Français

A complex corona between olivine and plagioclase from the Jotun Nappe, Norway, and the diffusion modelling of multimineralic layers

Published online by Cambridge University Press:  05 July 2018

J. R. Ashworth ,
J. J. Birdi  and
T. F. Emmett
J. R. Ashworth
Affiliation:
School of Earth Sciences, Univcrsity of Birmingham, Edgbaston, Birmingham BI5 2TT, U.K.
J. J. Birdi
Affiliation:
School of Earth Sciences, Univcrsity of Birmingham, Edgbaston, Birmingham BI5 2TT, U.K.
T. F. Emmett
Affiliation:
Geology Division, Anglia Polytechnic, East Road, Cambridge CB1 IPT, U.K.
Get access Rights & Permissions [Opens in a new window]

Abstract

Coronas containing Ca-amphibole with aluminous minerals have been characterised optically and by scanning electron microscopy, analytical transmission electron microscopy and electron-probe microanalysis. The layers nearest to plagioclase are amphibole + epidote + kyanite, followed by amphibole + epidote + staurolite + spinel. These assemblages are consistent with waterundersaturated conditions, possibly at lower metamorphic grade than the commoner assemblage amphibole + spinel. Observed mineral proportions and compositions were used in a seven-layer model of steady-state, diffusion-controlled growth with local equilibrium. This model is not fully realistic, because the observed amphibole is strongly zoned from tschermakitic to actinolitic away from plagioclase, suggesting disequilibrium. However, the four-mineral layer has been successfully modelled assuming local equilibrium, with diffusion coefficients Lii larger for i = FeO and MgO than for SiO2, AlO3/2, CaO and FeO3/2. Retarded grain-boundary diffusion of the latter components is explicable by crystal-chemical effects. The number of minerals per layer is constrained by a modified form of the metasomatic phase rule of Korzhinskii, with the role of 'inert' components played by relatively immobile ones (having relatively small fluxes and relatively small diffusion coefficients).

Keywords

coronaskyanitestaurolitetschermakitic amphibolemetasomatic phase rule
Type
Research Article
Information
Mineralogical Magazine , Volume 56 , Issue 385 , December 1992 , pp. 511 - 525
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1992

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

Present address: 17 Stonedown Close, Bilston, Wolverhampton WV7 9YN, U.K.

References

Ashworth, J. R. and Birdi, J. J. (1990) Diffusion modelling of coronas around olivine in an open system. Geochim. Cosmochim. Acta, 54, 2389–401.CrossRefGoogle Scholar
Ashworth, J. R. and Birdi, J. J. and Emmett, T. F. (1992) Diffusion in coronas around clinopyroxene: modelling with local equilibrium and steady state, and a non-steady-state modification to account for zoned actinolite-horn-blende. Contrib. Mineral. Petrol., 109, 307–25.CrossRefGoogle Scholar
Brady, J. B. (1977) Metasomatic zones in metamorphic rocks. Geochirn. Cosmochirn. Acta, 41, 113–25.CrossRefGoogle Scholar
Carlson, W. D. and Johnson, C. D. (1991) Coronal reaction textures in garnet amphibolites of the Llano Uplift. Am. Mineral., 76, 756–72.Google Scholar
Dowty, E. (1981)) Crystal-chemical factors affecting the mobility of ions in minerals. Ibid. 65, 174-82.Google Scholar
Emmett, T. F. (1982) Structure and petrology of the Bergen-Jotun kindred rocks from the Gjendebu region, Jotunheimen, central southern Norway. Norges Geol. Unders., 373, 1–32.Google Scholar
Emmett, T. F. (1989) Basic igneous rocks from a portion of the Jotun Nappe: evidence for Late Precambrian ensialic extension of 13altoscandia? In The Caledonide Geology of Scandinavia (R. A. Gayer, ed.). Graham & Trotman, London, pp. 143-51.CrossRefGoogle Scholar
Enami, M. and Zang, Q. (1988) Magnesian staurolite in garnet-corundum rocks and eclogite from the Dong-hai district, Jiangsu province, east China. Am. Mineral., 73, 48–56.Google Scholar
Frantz, J. D. and Mao, H. K. (1975) Bimetasomatism resulting from intergranular diffusion: mnltimineralic zone sequences. Carnegie Inst. Washington Yearb., 74, 417–24.Google Scholar
Frantz, J. D. and Mao, H. K. (1979) Bimetasomatism resulting from inter granular diffusion: lI. Prediction of multimineralic zone sequences. Am. J. Sci., 279, 302–23.CrossRefGoogle Scholar
Gil Ibarguchi, J. I., Mendia, M., and Girardeau, J. (1991) Mg- and Cr-rich staurolite and Cr-rich kyanite in highpressure ultrabasic rocks (Cabo Ortegal, northwestern Spain). Am. Mineral., 76, 501–11.Google Scholar
Grant, S. M. (1988) Diffusion models for corona formation in metagabbros from the western Grenville Province, Canada. Contrih. Mineral. Petrol., 98, 49–63.CrossRefGoogle Scholar
Grew, E. S. and Sandiford, M. (1985) Staurolite in a garnet-hornblende-biotite schist from the Lanterman Range, northern Victoria Land, Antarctica. Neues Jahrb. Mineral. Mh., 396-410.Google Scholar
Helms, T. S., McSween, H. Y. Jr, Labotka, T. C., and Jarosewich, E. (1987) Petrology of a Georgia Blue Ridge amphibolite unit with hornblende + gedrite + kyanite + staurolite. Am. Mineral., 72, 1086–96.Google Scholar
Joesten, R. (1977) Evolution of mineral assemblage zoning in diffusion metasomatism. Geochim. Cosmo- chim. Acta, 41, 649–70.CrossRefGoogle Scholar
Joesten, R. (1991) Local equilibrium in metasomatic processes revisited: Diffusion-controlled growth of chert nodule reaction rims in dolomite. Am. Mineral., 76, 743–55.Google Scholar
Johnson, C. D. and Carlson, W. D. (1990) The origin of olivine-plagioclase coronas in metagabbros from the Adirondack Mountains, New York. J. Metamorphic Geol., 8, 697–717.CrossRefGoogle Scholar
Korzhinskii, D. S. (1959) Physicochemical Basis of the Analysis of the Paragenesis of Minerals. Consultants Bureau, New York.Google Scholar
Kretz, R. (1983) Symbols for rock-forming minerals. Am. Mineral., 68, 277–9.Google Scholar
Leake, B. E. (1978) Nomenclature of amphiboles. Mineral. Mag., 42, 533–63.CrossRefGoogle Scholar
Lorimer, G. W. and Cliff, G. (1976) Analytical electron microscopy of minerals. In Electron Microscopy in Mineralogy (H.-R. Wenk, ed.). Springer-Verlag, Berlin etc., pp. 506-19.CrossRefGoogle Scholar
Morioka, M. (1981) Cation diffusion in olivine—II. Ni- Mg, Mn-Mg, Mg and Ca. Geochim. Cosmochirn. Acta, 45, 1573–80.CrossRefGoogle Scholar
Schreyer, W. (1988) Experimental studies on metamor- phism of crustal rocks under mantle pressures. Mineral. Mag., 52, 1–26.CrossRefGoogle Scholar
Schumacher, R. (1985) Zincian staurolite in Glen Doll, Scotland. Ibid., 49, 561-71.Google Scholar
Selverstone, J., Spear, F. S., Franz, G. and Morteani, G. (1984) High-pressure metamorphism in the SW Tauern Window, Austria: P-T paths from horn- blende-kyanite-staurolite schists. J. Petrol., 25, 501–31.CrossRefGoogle Scholar
Spear, F. S. (1982) Phase equilibria of amphibolites from the Post Pond Volcanics, Mt Cube Quadrangle, Vermont. Ibid., 23, 383-426.Google Scholar
Thompson, J. B., Jr (1970) Geochemical reaction and open systems. Geochim. Cosmochim. Acta, 34, 529–51.CrossRefGoogle Scholar
Ward, C. M. (1984) Magnesium staurolite and green chromian staurolite from Fiordland, New Zealand. Am. Mineral., 69, 531–40.Google Scholar