1:45 PM - 3:15 PM
[MIS13-P02] A 2D visco-elasto-plastic model of subduction channel growth and exhuming high-pressure metamorphic complexes
Keywords:2D-deodynamic modelling, subduction channel, high-pressure mélange, exhumed metamorphic rocks, P-T path
The exhumation of eclogite or other dense high-pressure metamorphic rocks hardly relies solely on their own buoyancy; this process requires less-buoyant rocks hosting the denser rocks, or alternatively, there can be missing parameters other than buoyancy that can affect the exhumation of eclogite (e.g., Morita, Tsujimori et al. 2022 J. Petrol.). In this contribution, we performed a 2D numerical geodynamic simulation with the I2VIS code (Gerya and Yuen 2003 EPSL). We tested the exhumation of subducted oceanic materials using different input parameters that includes the plate convergence rate, the subduction angle, the age of subducted slab, and the amount of sediments.
As numerical results demonstrate, if the convergence rate is high, more sedimentary materials can be dragged into the subduction channel, which reduces the density of the high-pressure mélange complex. In this case, the hangingwall continental crust deforms to form a fold belt and the width of the subduction channel increases. See more details in the figure attached in this abstract. The figure shows selected calculation results of the model with a convergence rate of 10 cm/yr and oceanic sediment thickness of 1,500 m; notably the P–T paths of the figures represent the exhumations of blueschist-facies metamorphic rocks.
Our preliminary numerical reconnaissance confirms the following two points: (1) Sediments can be a driving force of high-pressure metamorphic rocks to exhume to the relatively shallow level with a blueschist facies P–T condition, but the exhumed chunk stalls near the Moho depth. This is consistent with many petrological observations in literatures; (2) The P–T paths of exhumed high-pressure rocks in the subduction channel are significantly variable with the distance from relatively cold slab.
As numerical results demonstrate, if the convergence rate is high, more sedimentary materials can be dragged into the subduction channel, which reduces the density of the high-pressure mélange complex. In this case, the hangingwall continental crust deforms to form a fold belt and the width of the subduction channel increases. See more details in the figure attached in this abstract. The figure shows selected calculation results of the model with a convergence rate of 10 cm/yr and oceanic sediment thickness of 1,500 m; notably the P–T paths of the figures represent the exhumations of blueschist-facies metamorphic rocks.
Our preliminary numerical reconnaissance confirms the following two points: (1) Sediments can be a driving force of high-pressure metamorphic rocks to exhume to the relatively shallow level with a blueschist facies P–T condition, but the exhumed chunk stalls near the Moho depth. This is consistent with many petrological observations in literatures; (2) The P–T paths of exhumed high-pressure rocks in the subduction channel are significantly variable with the distance from relatively cold slab.