Synopsis

This paper documents the first identified occurrence of a garnet-bearing olivine-web-sterite rock within the Eastern Glenelg Lewisian of the Glenelg inlier. Bulk chemistries of the rock and associated websterites are comparable with komatiite or ultrabasic intrusive rocks. However, comparison with zoned ultrabasic–basic gneisses from the Scourie area suggests that the rock may be genetically linked to associated eclogites and represents a cumulate from a magma of basaltic composition. Geothermobarometry indicates that the rock equilibrated at eclogite facies P–T conditions: 20 ± 3 kbar, 730 ± 50°C. It is suggested that the magmatic protolith for this rock was emplaced during the Scourian, and from the textural evidence of the pyroxene grains, experienced granulite facies conditions followed by cooling prior to being subject to eclogite facies metamorphism during Grenville events.

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