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Garnet-chloritoid-kyanite metapelites from the Raspas Complex (SW Ecuador)

¹ Equipe Lithosphère, Géosciences Rennes (UMR CNRS 6118), Université de Rennes 1, F-35042 Rennes Cedex, France
² Institut pour la Recherche et le Développement - Laboratoire de Géologie des Chaînes Alpines, BP 53, F-38041 Grenoble Cedex 9, France
³ Institut de Minéralogie et Géochimie, Université de Lausanne, BFSH2, CH-1015 Lausanne, Suisse

^* E-mail: Piercarlo.Gabriele{at}univ-rennesl.fr

Mineral abbreviations are from Kretz (1983).

The Raspas Complex (Ecuador) contains one of the few eclogitic bodies in the northern Andes. It consists of metaperidotites, eclogites, and metapelites. The latter display three assemblages: (i) garnet + chloritoid + kyanite, (ii) garnet + chloritoid and (iii) garnet + chlorite, in all cases with quartz and muscovite in addition. The growth of these assemblages was coeval with the main ductile deformation, and was followed by minor reequilibration (chlorite growth in garnet + chloritoid samples and chloritoid + quartz aggregates replacing garnet and kyanite in garnet + chloritoid + kyanite samples). Detailed microprobe analyses show increasing magnesian compositions for garnet (from core to rim) and chloritoid (inclusions within garnet compared to matrix grains) in kyanite-bearing samples. The above data are interpreted in the framework of the KFMASH system. Reaction progress along the divariant reaction Cld = Grt + Ky explains the change in chemistry of coexisting phases. The divariant Grt-Cld-Ky assemblage has a narrow stability field, and the P-T conditions are estimated at about 20 kbar, 550–600°C. Decompression, recorded by chloritoid-quartz pseudomorphs of garnet, probably occurred as temperature decreased.

Key-words: eclogite-facies metamorphism, Ecuador, metapelite, Raspas Complex.

This article has been cited by other articles:

				E. Negulescu, G. Sabau, and H.-J. Massonne Chloritoid-Bearing Mineral Assemblages in High-Pressure Metapelites from the Bughea Complex, Leaota Massif (South Carpathians) J. Petrology, January 7, 2009; (2009) egn075v1. [Abstract] [Full Text] [PDF]