Grain-size dynamics beneath mid-ocean ridges: Implications for permeability and melt extraction

@article{Turner2014GrainsizeDB,
  title={Grain-size dynamics beneath mid-ocean ridges: Implications for permeability and melt extraction},
  author={A J Turner and Richard F. Katz and Mark Dietrich Behn},
  journal={Geochemistry, Geophysics, Geosystems : G(3)},
  year={2014},
  volume={16},
  pages={925 - 946}
}
Grain size is an important control on mantle viscosity and permeability, but is difficult or impossible to measure in situ. We construct a two‐dimensional, single phase model for the steady state mean grain size beneath a mid‐ocean ridge. The mantle rheology is modeled as a composite of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a plastic stress limiter. The mean grain size is calculated by the paleowattmeter relationship of Austin and Evans (2007… 

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References

SHOWING 1-10 OF 52 REFERENCES

Melt extraction from the mantle beneath spreading centers

Generation of permeability barriers during melt extraction at mid‐ocean ridges

Melt focusing at mid‐ocean ridges is necessary to explain the narrowness of the zone of crustal accretion and the formation of large but localized on‐axis seamounts at slow and ultraslow spreading

Channeling instability of upwelling melt in the mantle

We present results of a theoretical study aimed at understanding melt extraction from the upper mantle. Specifically, we address mechanisms for focusing of porous flow of melt into conduits beneath

Permeability of asthenospheric mantle and melt extraction rates at mid-ocean ridges

Application of the measurements in a model of porous-media channelling instabilities yields melt transport times of ∼1–2.5 kyr across the entire asthenosphere, which is sufficient to preserve the observed 230Th excess of mid-ocean-ridge basalts and the mantle signatures of even shorter-lived isotopes such as 226Ra.

The dynamics of melt and shear localization in partially molten aggregates

This work test a formulation for magma dynamics and provides an explanation for localized bands of high-porosity and concentrated shear deformation observed in experiments, and estimates the orientation of melt bands beneath mid-ocean ridges and shows that they may enhance magma focusing toward the ridge axis.

Melt migration beneath mid‐ocean ridges

Summary Using a two-phase flow model, we investigate the formation of a high-percentage melt layer beneath the oceanic lithosphere and focusing of the melt towards the ridge axis, taking into

Energetics of a two-phase model of lithospheric damage, shear localization and plate-boundary formation

SUMMARY The two-phase theory for compaction and damage proposed by Bercovici et al. (2001a, J. Geophys. Res.,106, 8887‐8906) employs a nonequilibrium relation between interfacial surface energy,
...