Abstract
A rare type of eclogite at Glenelg contains finegrained, white streaks about 1 mm across consisting of kyanite-oligoclase ±quartz ±Kfeldspar. Garnet and omphacite bordering the streaks are relatively enriched in grossular and jadeite components respectively. The streaks are interpreted as former plagioclase which reacted with neighbouring garnet and omphacite during a period of shearing and compression. P-T conditions during the reaction are estimated as 740° C and 17 kbar. Subsequent reaction, manifest by narrow rims of oligoclase on kyanite, new growth of garnet and resorption of omphacite, is interpreted as an effect of near-isothermal decompression by about 2 kbar. The compressive phase is attributed to dextral transpression (oblique convergence) along the Grenville Front in Scotland.
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Sanders, I.S. Plagioclase breakdown and regeneration reactions in Grenville kyanite eclogite at Glenelg, NW Scotland. Contr. Mineral. and Petrol. 98, 33–39 (1988). https://doi.org/10.1007/BF00371907
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DOI: https://doi.org/10.1007/BF00371907