Water in omphacite fingerprints the thermal history of eclogites

Abstract Omphacite is a diagnostic mineral of high- and ultrahigh-pressure rocks, its association with garnet characteristic eclogites from subduction-related massifs volcano-entrained xenoliths. can accommodate significant amounts water as structurally bound hydroxyl (OH) groups, able to convey into Earth's interior. We show, for the first time, experimental evidence that infrared absorption patterns in omphacite are temperature sensitive. This provides new framework discriminating natural equilibrated at different temperatures. also demonstrate low-temperature omphacite, integral absorbance ratio between OH bands 3620 cm−1 3450 linearly related temperature. Water massif records equilibrium, allowing reconstruction fluid-involved thermal history tectonics rock evolution.