Mathilde Cannat

The 2023 Arthur Holmes Medal & Honorary Membership is awarded to Mathilde Cannat for her contribution to the understanding of mid-ocean ridges in terms of tectonic processes and dynamics.

Mathilde Cannat has shown an everlasting passion for ocean floor tectonics, integrating a wide range of approaches, in a very original way. Indeed, petrology and geophysics became her main tools to explore mid-ocean ridges, leading her to propose several fundamental models for the formation, composition, and deformation of the oceanic crust. Our current vision of slow-spreading ridges is for a great part the result of Mathilde Cannat’s research.

Mathilde’s contribution to the field of tectonics is undoubtedly outstanding, in terms of observations, characterization, and quantification of structures and processes at work during ocean floor spreading. In the early ’90s, Mathilde developed new concepts of the formation of oceanic crust and the emplacement of mantle rocks at the active axis of spreading ridges, based on geophysics and petrology. These models soon became classical and are still up to date 25 years later. Mathilde continued to develop new concepts by investigating several mid-ocean ridges, especially the Southwest Indian Ridge, where she discovered and proposed the smooth seafloor as a new type of oceanic seafloor. The discovery of mantle rocks exhumed at the seafloor was the beginning of a new era of her research, devoted to mantle exhumation and serpentinisation processes. She developed the long- term in situ observation of the seafloor via a European Network (MOMARNET).

Mathilde conducted many fruitful cruises (17 cruises as chief scientist) in the Atlantic and Southwestern Indian ridges, investigating several topics (tectonic, hydrothermal, petrology…) applying multiple data acquisition techniques (submersible dives, dredging, multibeam mapping, gravity modelling, seismic reflection and refraction, heat-flow, seismicity). These numerous methods allowed her to quantify many different aspects of mantle exhumation dynamics at different scales (from the grain, up to the lithospheric scale). At very slow spreading centres mantle-derived peridotite, intruded by numerous gabbroic intrusions, can be tectonically uplifted to the seafloor along detachments faults. Her approach of living mid-ocean ridges was extended to ophiolites exposed on the continents, where Mathilde applied structural geology and petrology to better characterise the seafloor spreading mechanisms.

Medal lecture video (Vimeo) of the Arthur Holmes Medal given at the EGU General Assembly 2023.