In situ hydroclastic fragmentation of subaqueous ponded lavas; New Senator caldera, Abitibi greenstone belt, Quebec, Canada

► Archean subaqueous ponded lavas have been identified in the Abitibi greenstone belt. ► Surrounding volcanic facies indicate the ponded lavas are hosted in a large synvolcanic depression. ► Ponded lavas are separated by hyaloclastite horizons with atypical primary volcanic structures. ► Pillowed forms developed in situ during hydroclastic fragmentation. ► Fragmentation occurred when water entered the system via synvolcanic fractures and faults.