A possible UHP-eclogite in the Leaota Mts. (South Carpathians) and its history from high-pressure melting to retrograde inclusion in a subduction melange

An unusual eclogite pod containing impure jadeite to omphacite pyroxene with anti-phase domain (APD) visible under the optical microscope is hosted in a medium-grade matrix in the Leaota Massif. Textural relationships support the hypothesis of garnet formation by peritectic reactions involving high-jadeite clinopyroxene, while inclusions entrapped in garnet, mainly a wide range of amphibole compositions, seemingly crystallised from a fluid phase in disequilibrium with the garnet host. Thermobarometric estimates indicate UHP, HT peak conditions (2.8–3.2 GPa, 780–840°C) inconsistent with those of the associated rocks, followed by a complicated exhumation path. The P–T-array of the retrograde path suggests syn-subduction exhumation and tectonic inclusion in a melange with a matrix derived from the accretionary wedge. Partial melting of the subducting slab, which induces tectonic weakening, may be an effective mechanism in detaching and enclosing small eclogite pods in metamorphic terrains.