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Mineralogical evolution of fayalite-bearing rapakivi granites from the Prins Christians Sund pluton, South Greenland

Published online by Cambridge University Press:  05 July 2018

T. N. Harrison ,
I. Parsons  and
P. E. Brown
T. N. Harrison
Affiliation:
Department of Geology and Mineralogy, Aberdeen University, Aberdeen AB9 1AS, Scotland
I. Parsons
Affiliation:
Grant Institute of Geology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, Scotland
P. E. Brown
Affiliation:
Department of Geology and Mineralogy, Aberdeen University, Aberdeen AB9 1AS, Scotland
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Abstract

The Prins Christians Sund rapakivi granite pluton in South Greenland is a member of the early Proterozoic ‘Rapakivi Suite’ and is emplaced into early Proterozoic Ketilidian migmatites. The pluton is composed predominantly of black or dark brown monzonites and quartz monzonites (collectively, rapakivi granites), although a localised white facies is developed adjacent to metasedimentary xenoliths. The back rapakivi granites are extremely fresh and have an anhydrous primary mafic mineralogy of olivine and orthopyroxene, with rare inverted pigeonite and clinopyroxene; minor amounts of biotite and amphibole occur in most fayalite-bearing rapakivi granites. Feldspars in these rocks are black and non-turbid. The white rapakivi granites have a wholly hydrous mafic silicate assemblage and turbid, white or cream-coloured feldspars. Electron microprobe analyses of the mafic silicates in the black rapakivi granites show that they are Fe-rich, comprising fayalite (Fa93−96.5), orthopyroxene (Fs77−81), ferro-pargasitic and ferro-edenitic hornblende (Fe/(Fe + Mg) = 0.72−0.93), and biotite (Fe/(Fe + Mg) = 0.77−0.88). Both biotite and amphibole crystallised subsolidus, and often adopt symplectic morphologies. Biotite has formed in response to a fayalite-consuming reaction at temperatures below 650–700°C and fO2, of 10−16.5 to 10−17.5 bars, and continued to grow under reducing conditions below the QFM buffer to temperatures below 450–500°C. Orthopyroxene formed in response to a low-pressure fayalite-consuming reaction in the melt. The correlation of black, pristine feldspar with anhydrous mafic silicates, and of turbid feldspar with hydrous phases suggests either that the feldspars reflect the anhydrous nature of the parent magma, or more likely that the mafic mineralogy of the white rapakivi granites is secondary.

Keywords

Rapakivi graniteSouth Greenlandfayalitesubsolidus biotite
Type
Geochemistry and Petrology
Information
Mineralogical Magazine , Volume 54 , Issue 374 , March 1990 , pp. 57 - 66
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1990

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Footnotes

*

Now at: Dept. of Geology, The University, St. Andrews, Fife KY16 9ST, Scotland.

References

Allaart, J. H. (1967) Basic and intermediate igneous activity and its relationships to the evolution of the Julianehaab granite, South Greenland. Medd. om Gronland, 175, no. 1.Google Scholar
Allaart, J. H. (1976) Ketilidian mobile belt in South Greenland. In: Eseher, A. and Watt, W.S (eds.) Geology of Greenland. Copenhagen: Grønlands Geologiske Undersøgelse, 120-51.Google Scholar
Bohlen, S. R. and Boettcher, A. L. (1981) Experimental investigations and geological applications of orthopyroxene geobarometry. Amer. Mineral. 66, 951-64.Google Scholar
Bridgwater, D. (1963) A review of the Sydprøven granite and other ‘New Granites’ of South Greenland. Medd. Dansk Geol. Foren. 15, 167-82.Google Scholar
Bridgwater, D., Sutton, J. and Watterson, J. (1974) Crustal downfolding associated with igneous activity. Tectonophys. 21, 57-77.CrossRefGoogle Scholar
Brown, P. E., Tocher, F. E. and Chambers, A. D. (1982) Amphiboles from the Lilloise intrusion, East Greenland. Mineral. Mag. 45, 47-54.CrossRefGoogle Scholar
Brown, W. L. and Parsons, I. (1984) Exsolution and coarsening mechanisms and kinetics in an ordered crypt0perthite series. Contrib. Mineral. Petrol. 86, 3-18.CrossRefGoogle Scholar
Burnham, C. W., Holloway, J. R. and Davies, N. F. (1969) Thermodynamic properties of water to 1000∼ and 10,000 bars. Spec. Paper Geol. Soc. Amer. 132.CrossRefGoogle Scholar
Czamanske, G. K. and Wones, D. R. (1973) Oxidation during magmatic differentiation, Finnmarka Complex, Oslo area, Norway: Part 2, the mafic silicates. J. Petrol. 14, 359-80.CrossRefGoogle Scholar
Deer, W.A., Howie, R.A. and Zussmann, J. (1978) Rock-forming minerals, 2A. Single-chain silicates (2nd ed.) Longman, London. 688pp.Google Scholar
Eugster, H. P. and Wones, D. R. (1962) Stability relations of the ferruginous biotite, annite. J. Petrol. 3, 82-125.CrossRefGoogle Scholar
Frisch, T. and Bridgwater, D. (1976) Iron- and manganese- rich minor intrusions emplaced under lateorogenic conditions in the Proterozoic of South Greenland. Contrib. Mineral. Petrol. 57, 25-48.CrossRefGoogle Scholar
Furhman, M. L. and Lindsley, D. H. (1988) Ternaryfeldspar modelling and thermometry. Amer. Mineral. 73, 201-15.Google Scholar
Gilbert, M. E. (1966) Synthesis and stability relations of the hornblende ferropargasite. Amer. J. Sci. 264, 698-742.CrossRefGoogle Scholar
Gulson, B. L. and Krogh, T. E. (1975) Evidence of multiple intrusion, possible resetting of U-Pb ages, and new crystallisation of zircon in the post-tectonic intrusions (‘Rapakivi granites’) and gneisses from South Greenland. Geochim. Cosmochim. Acta, 39, 65-82.CrossRefGoogle Scholar
Harley, S. L. (1984) An experimental study of the partitioning of Fe and Mg between garnet and orthopyroxene. Contrib. Mineral. Petrol. 86, 359-73.CrossRefGoogle Scholar
Harrison, T. N., Brown, P. E., Parsons, I., Hutton, D. H. W., Dempster, T. J., and Becker, S. M. (1988) Granulite facies metamorphism, magmatism and extensional tectonics in the Ketilidian mobile belt of Southern Greenland. Mineral. Soc. Bull. no. 80, p. 8 (abstr.).Google Scholar
Harrison, T. N., Reavy, R. J., Finch, A. A. and Brown, P. E. (in press) Coexisting mafic and felsic magmas in the early Proterozoic rapakivi granite suite of Southern Greenland Bull. Geol. Soc. Denmark, 38.Google Scholar
Hewin, D. A. (1978) A redetermination of the fayalitemagnetite- quartz equilibrium between 650° and 850°. Amer. J. Sci. 278, 715-24.Google Scholar
Leake, B. E. (1978) Nomenclature of amphiboles. Mineral. Mag. 42, 533-63.CrossRefGoogle Scholar
Nash, W. P. (1976) Fluorine, chlorine and OH-bearing minerals in the Skaergaard intrusion. Amer. J. Sci. 276, 546-57.CrossRefGoogle Scholar
Oyawoye, M. O. and Makanjuola, A. A. (1972) Bauchite: a fayalite-bearing quartz monzonite. 24th. Int. Geol. Congr., Section 2, 251-66.Google Scholar
Parsons, I. (1978) Feldspars and fluids in cooling plutons. Mineral. Mag. 42, 1-17.CrossRefGoogle Scholar
Parsons, I. (1981) The Klokken gabbro-syenite complex, South Greenland: quantitative interpretation of mineral chemistry. J. Petrol. 22, 233-60.CrossRefGoogle Scholar
Parsons, I. and Brown, W. L. (1984) Feldspars and the thermal history of igneous rocks. In Feldspars and Feldspathoids (Brown, W. L., ed.) Reidel, Berlin, 31–71.Google Scholar
Perkins, D. and Chipera, S. J. (1985) Garnet-orthopyroxene-plagioclase-quartz barometry: refinement and application to the English River subprovince and the Minnesota River valley. Contrib. Mineral. Petrol. 89, 6-80.CrossRefGoogle Scholar
Piwinskii, A. J. and Wylfie, P. J. (1968) Experimental studies of igneous rock series: a zoned pluton in the Wallowa batholith, Oregon. J. Geol. 76, 205-34.CrossRefGoogle Scholar
Smith, D. (1971) Stability of the assemblage iron-rich orthopyroxene-olivine-quartz. Amer. J. Sci. 271, 370-82.CrossRefGoogle Scholar
Smith, D. (1974) Pyroxene-olivine-quartz assemblages in rocks associated with the Nain anorthosite massif. J. Petrol. 15, 58-78.CrossRefGoogle Scholar
Streckeisen, A. (1976) To each plutonic rock its proper name. Earth. Sci. Rev. 12, 1-33.CrossRefGoogle Scholar
Windley, B. F. (1965) The composite net-veined diorite intrusives of the Julianehaab district, South Greenland. Medd. om GrOnland 172, no. 8.Google Scholar
Worden, R. H., Walker, F. D. L., Parsons, I. and Brown, W.L. (1989) Micropores and perthite coarsening. Terra Abstracts 1, 290-1.Google Scholar