Pressure-temperature conditions in granulite facies rocks of the northern Canadian Shield, Arctic Canada

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6596880

Frisch, T

The northernmost part of the Churchill Structural Province of the Canadian Shield, underlying 60,000 km/sup 2/ of southeastern Ellesmere Island, Coburg Island and eastern Devon Island, consists of granulite facies metasedimentary, meta-igneous and plutonic intrusive rocks 2400 to 1900 m.y. old. Garnet+pyroxene+plagioclase of quartzofeldspathic gneisses from Ellesmere and Coburg islands indicate pressures, at 750/sup 0/C, ranging from greater than or equal to 6 to approx. 4kb; the lower pressures are derived largely, but not solely, from rim compositions. Similar rocks from Devon Island consistently indicate higher pressures of 6 to 7 kb. Garnet and plagioclase cores in sillimanite+cordierite-rich pelitic gneisses give pressures between 5 and 6.5 kb at 750/sup 0/C, the highest pressures being found in Devon Island rocks. Orthopyroxene+cordierite symplectites around garnet in magnesian metapelites indicate pressures under 4 kb at 650/sup 0/C. All cordierite is clearly of retrograde origin, having formed as a result of decompression during uplift, but even the highest pressures determined fall below the stability limit of cordierite in metapelites. Circumstantial evidence exists for the former stable coexistence of orthopyroxene+sillimanite, which would attest to pressures well in excess of 7 kb, but existing geobarometric equilibria have been strongly influenced by retrograde processes. Retrograde pressure-temperature conditions may well predominate in many granulite terranes but are not always recognized due to a scarcity of suitable mineral assemblages.

• Research Organization: Geological Survey of Canada, Ottawa
• OSTI ID: 6596880
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ANORTHOSITES
BASEMENT ROCK
CANADA
CHALCOGENIDES
GABBROS
GARNETS
GEOBAROMETRY
GEOTHERMOMETRY
GNEISSES
IGNEOUS ROCKS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METAMORPHIC ROCKS
MINERALOGY
MINERALS
NORTH AMERICA
NORTHWEST TERRITORIES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PETROGENESIS
PLUTONIC ROCKS
PRESSURE MEASUREMENT
PYROXENES
ROCKS
SILICATES
SILICON COMPOUNDS
SPINELS