Metamorphism of Meguma group metasedimentary rocks, Whitehead Harbour area, Guysborough County, Nova Scotia

Authors

  • Robert P. Raeside Department of Geology, Acadia University, Wolfville, Nova Scotia BOP 1X0; Present address: Department of Mining Engineering Technical University of Nova Scotia
  • John D. Hill Geological Survey of Canada, 601 Booth Street Ottawa, Ontario K.1A 0E8; P.O. Box 1000, Halifax, Nova Scotia 3ZJ 2X4
  • Brian G. Eddy Department of Geology, Acadia University wolfville, Nova Scotia BOP 1X0

DOI:

https://doi.org/10.4138/1635

Abstract

The metamorphic development of the Whitehead Harbour area is characterized by low pressure, amphibolite facies conditions. Metamorphic grade generally increases toward the margins of early Late Devonian granite plutons. In pelitlc litbologies of the Goldenville and Halifax Formations, chlorite or chlorite-biotite assemblages + albite occur at the lowest grades, chlorite and cordierite overlap in a narrow range, and extensive development of andalusite + biotite occurred at the expense of nuscovite + cordierite. Within 300 m of the contact of granite plutons in areas where post-granite deformation is weak or absent, hornfelsic textures are developed and fibrolite is present. Garnet-biotite geotberraometry yields temperatures in the range 317 C (chlorite-biotite-albite aasemblage) to 665 C (Billimanite hornfels). Large amounts of spessartine in garnet do not appear to have a significant effect on the calibration of the geotbermometer. Application of garnet-plagloelase geobarometers is limited because of restricted mineral assemblages, but indicates a maximum pressure of metamorphlsm of about 350 MPa, which is consistent with the alundnosllicate phase diagram. RÉSUMÉ Le développement métamorphlque de la région de Whitehead Harbour se caractérise par des conditions de basse pression dans le faciès à amphibolites. Le degré de métamorphisme augmente de façon générale vers les abords de plutons granitlques datés du début du Tardidévonien. Dans les terraes pelitiques des formations de Goldenville et d'Halifax. dea paragenèses à chlorite ou bien chlorite-biotite + albite soulignent les degrés de métamorphisme les plus faibles; la chlorite et la cordierite se chevauchent dans une zone étroite; on observée aussi un développement prononce des andalousite + biotite aux dépens des muscovite + cordiérite. Dans les régions ayant subi peu ou pas de déformation post-granite, des textures de cornéennes se sont développées et la fibrolite est présente. le tout jusqu'à 300 m du contact avec les plutons granitlques. La géothermometrie des grenats et des biotites conduit à des températures de l'ordre de 317 C (assemblage à chlorite-biotite-albite) à 665 C (corneenne à aillimanite). La grande proportion de spessartlte dans le grenat ne semble pas avoir affecté outre mesure la calibration du géotherroometre. Bien que limitée par les assemblages restreints de minéraux, l’utilisation des géobaroraetres à grenat et plagioclase permet d'envlsager une préssion métamorphlque maxlmale d'envlron 350 HPa, ce qui cadre blen avec le diagramroe de phase dée aluminosilicates. [Traduit par le journal]

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Published

1988-04-01

How to Cite

Raeside, R. P., Hill, J. D., & Eddy, B. G. (1988). Metamorphism of Meguma group metasedimentary rocks, Whitehead Harbour area, Guysborough County, Nova Scotia. Atlantic Geoscience, 24(1). https://doi.org/10.4138/1635

Issue

Vol. 24 No. 1 (1988)

Section

Articles

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