Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-23T08:43:03.687Z Has data issue: false hasContentIssue false

Oxygen fugacity variations and mineral reactions in sapphirine-bearing paragneisses, E. Grenville province, Canada

Published online by Cambridge University Press:  05 July 2018

R. K. Herd
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada, K1 OE8
D. Ackermand
Affiliation:
Mineralogisches Institut der Universität, D-2300 Kiel, Federal Republic of Germany
A. Thomas
Affiliation:
Department of Mines and Energy, Govt. of Newfoundland and Labrador, P.O. Box 4750, St Johns, Newfoundland, Canada
B. F. Windley
Affiliation:
Department of Geology, The University, Leicester, LE1 7RH, U.K.

Abstract

Sapphirine-bearing assemblages occur in paragneisses in a 200 km long block in the Grenville province in Labrador-Quebec. The occurrence of some of these rocks was previously known, but their considerable extent is now recognised from regional mapping. The mineral assemblages, reactions, and compositions and the tectonic structure in the paragneisses of this block are surprisingly uniform. Within feldspar-quartz layers we recognise assemblages with sapphirine, quartz, iron titanium oxides, spinel, corundum, diaspore, orthopyroxene, sillimanite, cordierite, garnet, and biotite in metre to millimetre-thick layers. These minerals reacted with their matrix, especially quartz, during cooling and uplift. At least 11 retrograde reactions gave rise to spectacular corona textures and define a P-T-time trajectory from c. 8 kbar at 900 °C to 6 kbar at 700 °C which changed from early isobaric to late isothermal. Based on successive generations of sapphirine and orthopyroxene with constant XMg and decreasing Fe3+/Fe2+ ratio in recalculated formulae, we deduce an accompanying change from high to low oxygen fugacity along this trajectory. The isothermal section of the trajectory is consistent with predicted rapid uplift and with field evidence for thrust tectonics and mylonitisation.

Type
Petrology
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1987

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.)

References

Anastasiou, P., and Seifert, F. (1972) Contrib. Mineral Petrol., 34, 272-87.Google Scholar
Emslie, R.F., Hulbert, U J., Brett, C.P., and Garson, D.F., (1978) Geol. Surv. Canada, Current Research Part A, Pap. 78-1A, 129-34.Google Scholar
Fleet, M.E., and Arima, M. (1985) Am. Mineral., 70, 1232-7.Google Scholar
Gittins, J., and Currie, K.L. (1979) Geol. Surv. Canada, Current Research Part A, Pap. 79-1 A, 77-82.Google Scholar
Grew, E.S. (1980) J. Petrol., 21, 39-68.Google Scholar
Harley, S.L. (1984) Ibid. 25, 697-712.Google Scholar
Hsü, L.C. (1968) Ibid. 9, 40-83.Google Scholar
Jackson, V., and Finn, G. (1982) Newfoundland and Labrador Dept. of Mines and Energy, Open File Lab. 13E/7(40), 22 pp.Google Scholar
Leong, K.M., and Moore, J.M., Jr. (1972) Can. Mineral., 11, 777-90.Google Scholar
Morse, S.A., and Talley, J.H. (1971) Can. Earth Planet. Sci. Lett., 10, 325-8.Google Scholar
Nielsen, P.A., and Gittins, J. (1977) J. Geol. Soc. Am. Abst. with Prog., 9, 305.Google Scholar
Newton, R.C. (1972) J. Geol., 80, 398-420.Google Scholar
Sen, S., and Bhattacharya, A. (1984) Contrib. Mineral. Petrol., 88, 64-71.Google Scholar
Thomas, A., and Wood, D. (1983) Geol. Surv. Canada, Current Research Part. A, Pap. 83-1A, 305-12.Google Scholar
Thomas, A., Culshaw, N.G., Mannard, G., and Whelan, G. (1984) Ibid. Pap. 84-1A, 485-93.Google Scholar
Thomas, A., Nunn, G.A. G., and Wardle, R.J. (1985) NATO ASI Series C,, 158, 151-61.Google Scholar