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, 550-600degreesC. Decompression, recorded by chloritoid-quartz
pseudomorphs of garnet, probably occurred as temperature decreased.