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The Mineral Talc May Host Slow Earthquakes During Subduction in Mexico | AGU's EOS

2023-08-23 16:10:29

Newly published work from UW shows that chemical transformations during subduction play a central role in the mechanical behavior of the faults that accommodate motion between the subducting and overriding tectonic plates. Talc, a water-rich and very weak mineral, may host slow earthquakes during subduction, like those observed in the Cascadia subduction zone in Washington, as well as where the Cocos Plate subducts beneath Mexico. Recent work by PhD student Peter Lindquist, with ESS Assistant Professor Cailey Condit, ESS NSF Postdoctoral Fellow Will Hoover, and collaborators David Hernandez-Uribe and Victor Guevara, was featured in AGU's EOS magazine, and revealed the magnitude of these chemical transformations (e.g., metamorphic dehydration and metasomatism) we might expect during subduction beneath Mexico. In this study, which was published in AGU's Geochemistry, Geophysics, Geosystems journal in August 2023, Lindquist et al. modeled how much of the mineral talc would be produced when fluids released by metamorphic reactions in the Cocos plate interact with rocks at the subduction fault (plate interface) beneath Mexico. Lindquist's results predict enough talc production to host slow earthquakes, which are observed in this subduction zone, but not enough talc to explain the seismic observations of a low velocity zone at the plate interface that has previously been interpreted as the result of a 4 km thick zone of talc-rich rocks. This work shows how important it is to take into account chemical transformations like metamorphism and metasomatism when thinking about the slip behaviors of seismogenic faults and subduction zones.

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