A seminar presented by Dr Catriona Menzies, Durham University. Geological processes at subduction zone margins control seismicity, plutonism/ volcanism, and geochemical cycling between the oceans, crust, and mantle.
The down-going plate experiences dehydration, and the associated metamorphism alters the physical properties of the plate interface and mantle wedge. Serpentinite mud volcanoes in the Mariana forearc are up to 50 Myrs old, 1-3 km high and up to 50 km in diameter. These mud volcanoes permit sampling of fluids and xenoliths ascending from ~13 to 20 km depth from the subducting slab and forearc mantle as fluid-laden serpentinite flows along active faults in the extending upper plate of the subduction zone. The changes in major and trace element chemistry and isotopic composition (D/H, O, B and 87Sr/86Sr) of pore fluids between seamounts trace the evolution of the down going slab during progressive subduction. Thermodynamic modelling reveals that the evolution of pore water chemical compositions reflect mineralogical characteristics of a predominately basaltic source from the downgoing Pacific Plate. Our results indicate that with progressive subduction the lawsonite-epidote mineral transformation boundary at 250 °C may help drive slab carbonate destabilisation, despite its apparent thermodynamic stability at such temperatures and projected pressures (300 °C and 0.6 GPa).
|Date||Wednesday, 8 February 2023|
|Time||1:00pm - 2:00pm|
|Audience||Career advisers,Future students,Parents,Public,Undergraduate students,Postgraduate students,Staff,Alumni|
|Location||Benson Common Room (Gn9, Geology Building), Dunedin and |
Zoom via https://bit.ly/otagogeology
|Contact Name||Jack Williams|