Magnetotelluric imaging beneath the Taiwan orogen: An arc-continent collision

Arc-continent collisions are a fundamental plate tectonic process that control continental growth, orogen development and the distribution of natural hazards and natural resources. This process actively occurs in Taiwan where the Luzon Volcanic Arc collides obliquely with the passive margin of the Eurasian Plate. An important characteristic of the arc-continent collision in Taiwan is that oblique convergence has produced an orogen that decreases in age from north to south. Investigation of the temporal evolution of the Taiwan orogen is therefore made possible through studies at different latitudes on the island.;In this thesis, the central Taiwan TAIGER MT data are shown to be inconsistent with orogen-scale thin-skinned tectonic models and instead support predictions of lithospheric-scale deformation (i.e. thick-skinned tectonics) beneath the Central Ranges. Similarity between resistivity models of central and southern Taiwan indicate that thick-skinned tectonics is occurring in both locations, and is therefore a persistent mode of deformation that operates as the orogen develops. The resistivity model for northern Taiwan is shown to be consistent with dewatering of the subducting Philippine slab, and with deformation described by the subducting indenter tectonic model.;A global context for the Taiwan results is provided by comparison to the South Island of New Zealand that shares many similarities with the tectonic setting in Taiwan. MT resistivity models support lithospheric deformation beneath the Southern Alps, and the occurrence of fluid-based conductors in the Marlborough region caused by dewatering of the Pacific slab.;The first long-period magnetotelluric (MT) measurements in Taiwan were recorded at 82 locations on three profiles across south, central and north Taiwan during 2006--2007. These MT data were collected as a component of the TAIGER (Taiwan Integrated Geodynamics Research) project and are analyzed and interpreted in this thesis. The TAIGER project was initiated to: (1) collect multi-technique high resolution geophysical data required to unambiguously distinguish between end-member tectonic models proposed for central Taiwan, and (2) to investigate the orogen evolution by comparison of data collected at latitudes ranging from south to north Taiwan.