Mathematics – Logic
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.v31a2121z&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #V31A-2121
Mathematics
Logic
1031 Subduction Zone Processes (3060, 3613, 8170, 8413), 3060 Subduction Zone Processes (1031, 3613, 8170, 8413), 3613 Subduction Zone Processes (1031, 3060, 8170, 8413), 8170 Subduction Zone Processes (1031, 3060, 3613, 8413), 8413 Subduction Zone Processes (1031, 3060, 3613, 8170)
Scientific paper
To understand the plume initiation and propagation it is important to understand whether small-scale convection is occurring under the back-arc in the Low Viscosity Wedge(LVW) and its implication on the island-arc volcanism. Honda et al. [Honda and Saito, 2003; Honda, et al., 2007]) already deployed small- scale convection in the Low Viscosity Wedge (LVW) above a subducting slab with kinematically imposed velocity boundary condition. They have suggested that a roll (finger)-like pattern of hot and cold anomalies emerges in the mantle wedge above the subducting slab. Here, we perform three-dimensional coupled petrological-thermomechanical numerical simulations of intraoceanic one-sided subduction with spontaneously bending retreating slab characterized by weak hydrated upper interface by using multigrid approach combined with characteristics-based marker-in-cell method with conservative finite difference schemes[Gerya and Yuen, 2003a], to investigate the 3D instabilities above the slab and lateral variation along the arc. Our results show that water released from subducting slab through dehydration reactions may lower the viscosity of the mantle. It allows the existence of wave-like small-scale convection in the LVW, which is shown as roll-like structure in 2D petrological-thermomechanical numerical experiments [Gorczyk et al., 2006] using in-situ rock properties computed on the basis of Gibbs free energy minimization. However, in our 3D cases, the rolls aligning with the arc mainly occur earlier , while zig-zag small-scale thermal-chemical instabilities may episodically form above the slab at later stages, which is different from the aligning finger-like pattern in purely thermal models (Honda et al,2003;2007). Also in contrast to thermal convection chemically buoyant hydrated plumes rising from the slab in our models are actually colder then the mantle wedge [Gerya and Yuen 2003b] which also strongly modify both the convection pattern and the seismic structure in the wedge. The zig-zag wave-like 3D instabilities have another implication on the Quaternary volcanism in the Northeast Japan. References Gerya, T. V.,Yuen D. A. (2003a), Physics of The Earth and Planetary Interiors, 140, 293-318. Gerya, T.V., Yuen, D.A. (2003b), Earth and Planet Sci. Lett., 212, 47-62. Gorczyk, W., et al. (2006), Geochem. Geophys. Geosyst., 7, doi:10.1029/2005GC001075. Honda, S., Saito M. (2003), Earth and Planetary Science Letters, 216, 703-715. Honda, S., et al. (2007), Island Arc, 16(2), 214-223.
Arcay Diane
Gerya Taras V.
Yuen Dave A.
Zhu Guohuai
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