System closure during the combustion metamorphic “Mottled Zone” event, Israel

► The Mottled Zone Event was a spontaneous combustion of bituminous chalks and marls. ► This resulted in the formation of high-T low-P metamorphic mineral assemblages. ► On a sufficiently large scale (100-102 m) the metamorphic process was isochemical. ► Isochemistry is most convincingly demonstrated on isocon plots. ► On a < 1 m scale intensive veining indicates mobilization of several elements.