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Subduction and volatile recycling in Earth's mantleThe subduction of water and other volatiles into the mantle from oceanic sediments and altered oceanic crust is the major source of volatile recycling in the mantle. Until now, the geotherms that have been used to estimate the amount of volatiles that are recycled at subduction zones have been produced using the hypothesis that the slab is rigid and undergoes no internal deformation. On the other hand, most fluid dynamical mantle flow calculations assume that the slab has no greater strength than the surrounding mantle. Both of these views are inconsistent with laboratory work on the deformation of mantle minerals at high pressures. We consider the effects of the strength of the slab using two-dimensional calculations of a slab-like thermal downwelling with an endothermic phase change. Because the rheology and composition of subducting slabs are uncertain, we consider a range of Clapeyron slopes which bound current laboratory estimates of the spinel to perovskite plus magnesiowustite phase transition and simple temperature-dependent rheologies based on an Arrhenius law diffusion mechanism. In uniform viscosity convection models, subducted material piles up above the phase change until the pile becomes gravitationally unstable and sinks into the lower mantle (the avalanche). Strong slabs moderate the 'catastrophic' effects of the instabilities seen in many constant-viscosity convection calculations; however, even in the strongest slabs we consider, there is some retardation of the slab descent due to the presence of the phase change.
Document ID
19950015385
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
King, S. D.
(Purdue Univ. West Lafayette, IN, United States)
Ita, J. J.
(California Inst. of Tech. Pasadena, CA., United States)
Staudigel, H.
(Vrije Univ. Amsterdam, Netherlands)
Date Acquired
September 6, 2013
Publication Date
January 1, 1994
Publication Information
Publication: Lunar and Planetary Inst., Conference on Deep Earth and Planetary Volatiles
Subject Category
Geophysics
Accession Number
95N21802
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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