Chloritoid-Bearing Mineral Assemblages in High-Pressure Metapelites from the Bughea Complex, Leaota Massif (South Carpathians)

High-Mg chloritoid (X-Mg 040047) and relatively high-Mg staurolite (X-Mg 025028) coexisting with kyanite and garnet were identified in a micagarnet-rich rock associated with very high-pressure eclogites in the Bughea Complex of the Leaota Massif (South Carpathians). Major and trace element geochemical data for both fresh eclogites and associated rocks which represent a metasomatic or retrograde alteration rind of the eclogites, indicate a pelitic precursor. Magnesian chloritoid was found as inclusions in garnet as part of a chloritoidkyanitegarnet assemblage which is indicative of high-pressure conditions. The host garnet shows a typically prograde chemical zoning pattern. The chloritoid-bearing assemblage is confined to the inner part of the garnet porphyroblasts, whereas the matrix assemblage in equilibrium with Mg-rich garnet rims has exceeded the thermal stability limit of chloritoid. Pressuretemperature pseudosections for simplified compositions approaching the rock bulk-chemistry show a high-pressure field for the identified chloritoid-bearing assemblage in good agreement with pressuretemperature estimates in the CFMASH and KCFMASH chemical subsystems using analysed mineral compositions. The derived pressuretemperature path is clockwise, indicating overprinting during exhumation from 18 GPa and 580C to 115 GPa and 620C, at a water activity approaching a(H2O) 1. These conditions were attained in a subduction mlange indicating transient thermal perturbations of a subduction channel.