Pseudoclastic hydrothermal alteration textures occur within quenched coherent dykes forming part of a subaqueous dome
complex (-4 Ma) on Ponza Island, Italy. These textures are similar to those observed in considerably older (-500 Ma)
subaqueous volcanic rocks at a number of localities throughout the Mount Read Volcanics in Tasmania and elsewhere in
ancient volcanic sequences of this type in Australia. This is significant because the processes of formation, hydrothermal
alteration and secondary mineralisation of ancient volcanic sequences may be better understood if we can make
comparisons with modern analogues. Observations at Ponza imply that these pseudoclastic alteration features form
synvolcanically or immediately after dyke emplacement and lava extrusion. This is compatible with scenarios presented
for their formation in ancient sequences in the Mount Read Volcanics, Tasmania.