Subduction thermal regime, petrological metamorphism and interface seismicity in Solomon
Description
Based on the thermomechanical model Stag3D and the finite difference method (FDM), we constructed a 3D, time-evolving thermomechanical finite difference model. The model dimensions are 1500 × 750 × 400 km (width × length × depth), and the mesh is 80 × 80 × 100. In comparison with a fully dynamic model, we created a thermal model that includes a kinematic slab and other dynamic domains for the mantle and crust. In our model, we adopted the updated geometry of the subducted oceanic plate following Slab2.0 and NNR-MORVEL56 data sets. The oceanward temperature boundary condition was set according to the plate cooling model, and the plate ages were provided by EarthByte. The seafloor ages of the Solomon Sea plate are 40-42 Ma, whereas ages of 134-150 Ma occur along the Pacific Plate. The bottom and boundaries of the slab are prescribed as adiabatic and permeable, and the top surface is assumed to be rigid and have a fixed temperature of 0°C. The oceanic lithospheric thickness is specified according to its age. Here, we investigate the slab water content using the P–T–wt%–facies database following Omori et al. (2009) and Hacker et al. (2003). The temperature and pressure at each P–T grid point follow the preliminary reference Earth model (PREM). Through interpolation, we obtain the intraslab temperature (°C) and water content distribution (wt%) at different intraslab depths. The slab temperature gradient (°C/km) and dehydration rate (wt%/km) are then calculated based on the temperature/water content differences divided by the distance (km) along the slab between neighboring grids. The modeling results are constrained by the observations of surface heat flow from the global heat flow database and heat flow from Curie point depth estimates.