Petrophysical properties of volcanic rocks and impacts of hydrothermal alteration in the Guadeloupe Archipelago (West Indies)

Advancing hydrothermal alteration removes magnetic minerals and transforms initial rocks. The original plagioclases and pyroxenes in neoformed chlorite, white micas, quartz, epidote and clay minerals are replaced. This modifies the shape of the pore network. Furthermore, hydrothermal alteration results in a reduction of pore throat diameter. It tends to decrease petrophysical differences between lavas and debris flows, increasing the porosity and permeability of effusive rocks, while the opposite effects are observed for debris flows.