A geophysical index to map alteration, permeability, and mechanical properties within volcanoes. Application to the soft volcanic rocks from Whakaari/White Island (New Zealand)

• Published in: Journal of Volcanology and Geothermal Research
• Main Authors: Revil, André, Coperey, Antoine, Heap, Michael, Carbillet, Lucille
• Other Authors: Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Institut de physique du globe de Strasbourg (IPGS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDU]Sciences of the Universe [physics]; New Zealand; White Island
• Online Access: https://hal.science/hal-03005820; https://hal.science/hal-03005820/document; https://hal.science/hal-03005820/file/2020-JVGR-alteration%20index%20volcan.pdf; https://doi.org/10.1016/j.jvolgeores.2020.106945

International audience The alteration of soft volcanic rocks (i.e., characterized by a low uniaxial compressive strength b35 MPa) can change their permeability and mechanical strength. We built an alteration indicator based on porosity and cation exchange capacity (CEC) to connect the degree of alteration of soft volcanic rocks to their permeability and uni-axial compressive strength. The proposed empirical petrophysical relationships are validated using a dataset of 62 samples from Whakaari/White Island (New Zealand). Since porosity and CEC can be imaged with induced polarization , this geophysical method can be used to map permeability and mechanical properties for near-surface formations at active volcanoes worldwide.