Open AccessTime‐dependent interaction between subduction dynamics and phase transition kinetics
Author(s) -
Tetzlaff M.,
Schmeling H.
Publication year - 2009
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2009.04182.x
Subject(s) - subduction , geology , slab , olivine , lithosphere , mantle (geology) , transition zone , metastability , buoyancy , spinel , geophysics , thermodynamics , mineralogy , seismology , tectonics , physics , quantum mechanics , paleontology
SUMMARY Numerical subduction models are presented that account for the kinetics of the olivine–spinel transformation and the equilibrium transformation of spinel into perovskite and magnesiowustite. Temperature‐, depth‐ and stress‐dependent rheology is used. Buoyancy due to temperature and the olivine, spinel, and magnesiowustite/perovskite phases leads to free subduction into the transition zone, and retarded penetration into the lower mantle. A dynamic feed back mechanism is found between the different buoyancy forces, the kinetics of the phase transition and the release of latent heat. This mechanism modulates the ‘parachute’‐effect of the metastable olivine (MO) in a subducting slab and leads to characteristic temporal variations of the depth of MO and, with a time delay, variations of the subduction velocity. Time periods are of the order of 3–4 Myr. This mechanism allows to explain variations of the depths of the deepest earthquakes in otherwise similar subduction zones. Further conclusions are as follows. The maximum depth of MO increases roughly linearly with lithospheric thickness, and the maximum depth may reach as deep as 720–750 km. Different subduction zones may represent different stages of ‘velocity–depth phase loops’ of MO.