Generation of Tectonic Over-pressure inside Subducting Slab Involving Phase-Loop of Olivine-Spinel Transition

Abstract:

We conducted a two-dimensional numerical model to analyze the generation of tectonic over-pressure, which is a positive deviation from lithostatic pressure, for deep slabs which are anchored at the 660 km phase boundary. The formation of the ductile shear zone under a compressional tectonic setting induces tectonic over-pressure. We first propose that an apparent shear zone originated from an elastic heterogeneity in the phase loop, which is the two-phase (i.e., olivine and spinel) coexistence interval around the 410 km boundary within subducting slabs, can cause tectonic over-pressure with a range from 0.3 to 1.5 GPa. This over-pressure significantly impacts the formation of the olivine-spinel phase transition. The flattening of the olivine-spinel interface by over-pressures are well-resolved. Therefore, we argue that the over-pressure should be applied when analyzing the phase boundary within the subducting slab. Our results provide a new insight on the interplay among the phase transition, shear zone formation and tectonic over-pressure.

* The draft including the abstract above was submitted on 3rd Aug, 2014 with slight modification.