Deformation modes of magmatic and amagmatic ocean lithosphere at ultraslow spreading ridges
IPGP - Îlot Cuvier
Séminaires Géosciences Marines
Mid-ocean ridges spreading at velocities of less than 20 mm/y form a separate class of mid-ocean ridges with spreading processes that differ from any faster spreading ridges. The main representatives of these ultraslow ridges, the Arctic Ridge System and the Southwest Indian Ridges, lie in remote areas with difficult working conditions such that our knowledge about ultraslow spreading processes is still limited. Together with my Junior Research Group MOVE, I collected over the past 10 years seismicity data from ultraslow spreading ridges from first reconnaissance data to dedicated local ocean bottom seismometer records. From this dataset we obtain a detailed insight into ultraslow seismicity pattern and spreading processes. We could prove a very thick lithosphere, with amagmatic sections that deform aseismically due to pervasive alteration. The lithosphere is thinner and brittle underneath volcanoes that may collect melts from a larger region. Spreading episodes at these volcanoes may last a decade and produce strong earthquakes and unusual volcanic eruptions.