Melting above the mantle transition zone beneath the Pacific margins
Abstract
In this work, we analyze the seismic signatures and stability of melting above the mantle transition zone on both margins of the Pacific. Using seismic signatures of P-to-S receiver functions and transition-zone thickness, we calculate the volume fraction of melt in the seismic low velocity layer (LVL) as a function of potential temperature, recycled eclogite component in the solid, Clapeyron slope of olivine-wadsleyite phase transition and solid-melt dihedral angle. Using a numerical model of advection-diffusion-reaction, we evaluate the timescale for slab-derived and carbon-rich melt to percolate through the mantle, and stabilize an LVL just above the olivine-wadsleyite phase transition. In the numerical models, we quantify the competing effects of volatile input from the stalled subducted slabs and redox freezing in the mantle. Our initial results indicate that the amount and availibility of slab derived fluids plays a significant role in the stability of carbonate-rich melts in a reducing mantle. We show that LVLs can act as major reservoirs of carbon and water in the mantle. An LVL, similar in size to the LVL beneath the western US, can sequester up to 30 Mt C/yr from the subducting slab, a significant protion of global carbon cycle.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMDI31B0009H
- Keywords:
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- 1038 Mantle processes;
- GEOCHEMISTRY;
- 3924 High-pressure behavior;
- MINERAL PHYSICS;
- 7208 Mantle;
- SEISMOLOGY;
- 8124 Earth's interior: composition and state;
- TECTONOPHYSICS