Mountain Building in Taiwan: Insights From 3‐D Geodynamic Models

Abstract

AbstractTaiwan is widely considered to be a typical example of an arc‐continent collision surrounded by two opposite dipping subduction zones. The manner by which the interaction of the two neighboring slabs caused plate collision and mountain building is insufficiently understood. Various hypotheses have been proposed, but the geodynamic feasibility of those remains to be tested. Here we present 3‐D thermomechanical models to study the geodynamic evolution process of a Taiwan‐like setting after an initial transform fault was consumed. In our model setup, the boundary between the Eurasian plate and the South China Sea is northeast trending. The results show that all simulations result in toroidal mantle flow around the slab edges and that slab breakoff as well as a small‐scale mountain belt with high topography and crustal exhumation occurs in most cases. The Eurasian continental crust is exhumed in a dome‐like manner exposing higher‐grade metamorphic rocks, facilitated by high erosion rates and a weak continental lower crust rheology, but inhibited by the presence of a weak arc. A high topography within the orogen, as well as continental slab detachment, can develop for the convergence direction of N307° and large convergence rates. Our modeling results are thus generally consistent with the Eurasian slab‐tearing model proposed for Taiwan based on seismic tomographic studies, and we suggest that the main characteristic features in Taiwan can be explained by the combined effects of fast erosion, a weak lower crust, fast convergence, and a small convergence azimuth.