Fig. 1: Electron microscope images showing microtextures of run products.

a Recrystallized aragonite, showing rims of sub-micrometric crystals surrounding relict cores 50–100 µm in size. b Assemblage graphite + aragonite; aragonite crystals show dissolution/reprecipitation microtextures such as crystal size reduction, hoppering, step edges and euhedral crystal intergrowth.