Report of a rare, well-preserved lawsonite eclogite (Elekdağ, Central Pontides, Türkiye)

Abstract

Although lawsonite eclogite is predicted from experimental, thermodynamic, and geophysical methods to be common in cold subduction zones, the defining metamorphic assemblage in metabasite (garnet + omphacite + lawsonite) is rare in exhumed subduction complexes. To date, there are nine well-documented complexes with these phases in apparent textural equilibrium in the matrix. A 10th (Elekdağ, Central Pontides, Türkiye) has previously been interpreted as a lawsonite eclogite based on lawsonite and omphacite inclusions in garnet. We report the first observation of an Elekdağ eclogite that contains abundant matrix lawsonite with omphacite + garnet, allowing determination of near-peak metamorphic conditions. Zr-in-rutile thermometry and phase diagram calculations indicate lawsonite eclogite facies conditions of ∼ 500 °C at P ∼ 2.3 GPa, higher than previous estimates of pressure but similar to other fresh lawsonite eclogites reported worldwide. In most Elekdağ metabasites, lawsonite eclogite was retrogressed to epidote ± lawsonite blueschist. The prevalence of epidote in eclogite and blueschist in this and other subduction complexes indicates exhumation conditions that were warmer than prograde or peak metamorphism. These apparently relatively “warm” conditions should not be extrapolated to characterize the overall thermal state of subduction in the forearc region that is typically represented by subduction complexes.

The authors' abstract, as published at the source. European Journal of Mineralogy, 2026 · DOI ↗