Serpentinized forearc mantles: Thermal and mineralogical stability and implications for the hydrology of the former deep forearc hydrology and seismicity of the San Andreas Fault System after the northward migration of the Mendocino Triple Junction
Stephen Kirby
USGS
- Date & Time
- Location
- Hybrid In-Person and Online seminar via Microsoft Teams
- Summary
It has been more than 30 years since Simon Peacock first proposed that the forearc mantle of the Cascadia subduction system is partially serpentinized. Geophysical evidence published since then strongly supports his hypothesis. Similar observations in southwest Japan also point to the Nankaido subduction system as another warm-slab subduction system having a serpentinized forearc mantle. Moreover, a rich set of seismic observations in both systems point to EPS phenomena being related to the updip migration of fluids from a dehydrating forarc mantle. An important question is whether certain changes in subduction inputs at trenches that lead to warming of the forearc mantle could release this stored water into the forearc crust and/or updip into the interplate thrust zone and could influence the deep hydrology and rheology of the forearc crust and the interplate thrust zone. I use as example of the San Andreas Fault System in the California Coast Ranges, suggesting that such models give insights into independent phenomena in the distributed plate boundary of the California Coast Ranges, including the occurrence of block-and-matrix serpentinite melanges occuring along the active faults in the California Coast Ranges.