Microstructure and mechanical properties of massive and porous of lavas from S. Miguel Island (Azores, Portugal)

The role of elongated pores and crystals of lavas influences their mechanical and physical behaviour, providing a first microstructural clue. In the context of a doctoral project, two samples – a trachyte and a basalt/andesite (s.l.) - representative of Fogo Volcano (S. Miguel Island, Azores, Portugal) were collected as part of an intact rock study. They were microstructurally assessed in the INGV-OV (Naples) using the ZEISS Xradia Versa 410 X-ray computed microtomography to obtain high-resolution 3D images, as well as to perform real-time in-situ mechanical tests (uniaxial – 7 mm diameter cylinders - and Brazilian – 13 mm diameter discs) to assess how elongated pores/crystals control strength. In addition to 3D images of the samples, which allow segmentation of the pore space and crystals, mechanical tests show that trachytes are more competent than vesicular basalts/andesites. Both pores and crystals control the development of the crack pattern.