Physics – Geophysics
Scientific paper
Jan 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999georl..26..119m&link_type=abstract
Geophysical Research Letters, Volume 26, Issue 1, p. 119-122
Physics
Geophysics
20
Tectonophysics: Dynamics Of Lithosphere And Mantle-General, Tectonophysics: Earth'S Interior-Composition And State, Tectonophysics: Plate Motions-General, Mathematical Geophysics: Modeling
Scientific paper
Although velocities of subducting slabs should be controlled primarily by their negative thermal buoyancies, their mineralogy can also have significant effects. We explore this by using thermo-kinetic modeling to predict mineralogy and compare the resultant buoyant (driving) force to the opposing viscous drag. Phase transitions of (Mg,Fe)2SiO4 in subducting slabs depend on thermal structure in two ways. First, equilibrium phase boundaries should be deflected, causing local buoyancy anomalies whose sign depends upon that of the Clapeyron slope. As slabs first enter the transition zone, negative anomalies should accelerate them, but positive anomalies that arise when they fully penetrate the transition zone should slow them. Such effects may induce geologically abrupt changes in plate motions. Second, olivine that persists metastably in slabs will form regions of positive buoyancy which should reduce slap velocities. The coldest and fastest slabs should be slowed more greatly, thus narrowing the range of feasible subduction rates. Decreased descent rates, however, allow slabs to warm and metastable wedges to thermally erode. Such negative feedback mechanisms may serve to regulate subduction rates.
Bina Craig R.
Marton Frederic C.
Rubie David C.
Stein Seth
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