Department of Geosciences, Faculty of Science, Osaka City University
抄録(英)
Two types of sapphirine-bearing granulites have been found in South Harris, NW Scotland. Both indicate ultra-high temperature conditions (over 900℃). Sapphirine-bearing orthopyroxene-sillimanite granulite contains orthopyroxene+sillimanite+sapphirine+garnet±cordierite as the pre-stable assemblage, indicating P-T conditions of 930-980℃ and 8-9 kbar. The other type, sapphirine-bearing orthopyroxene-kyanite granulite, contains two types of orthopyroxene (porphyroblast and intergrowth with kyanite), and sapphirine inclusions within aluminosilicate (mainly sillimanite). The orthopyroxene porphyroblasts have Al_2O_3 up to 9.7 wt%, indicating P-T condition of 1000-1050℃ and 10-11 kbar, while orthopyroxene intergrown with kyanite only have Al_2O_3 up to 7.5 wt%, indicating P-T conditions of 900℃ and 12-14 kbar. The inferred P-T path, mainly based on the orthopyroxene-kyanite granulite, had an anticlockwise trajectory with sapphirine+quartz breaking down to produce sillimanite+orthopyroxene intergrowths, followed by the aluminosilicate transition from sillimanite to kyanite. This is the first record of such ultra-high temperature metamorphism in South Harris. The UHT metamorphism may be a significantly distinctive thermal event that will prove important in reconstruction of the evolutional history of the Lewisian Complex at Palaeoproterozoic period.
雑誌書誌ID
AA00733561
雑誌名
Memoirs of National Institute of Polar Research. Special issue
Ultra-high temperature metamorphism in the Lewisian Complex, South Harris, NW Scotland
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KJ00000012892
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概要
