Oblique arc-continent collision has occurred in Taiwan since the late Miocene and has generated the Taiwan orogen. This collision provides an ideal location for studying the evolution of these poorly understood tectonic features. To explain the tectonics beneath central Taiwan, two competing end-member models have been proposed; (1) thin-skinned tectonics and (2) the lithospheric deformation model (thick-skinned). These models have very different structures at mid and lower crustal depths. Insufficient geophysical data exist to determine which model is applicable in Taiwan. In 2006 and 2007, long-period Magnetotelluric data were acquired on a profile across central Taiwan as part of the Taiwan Integrated Geodynamics Research (TAIGER) project. These MT data are sensitive to lower crustal depths and can be used to infer crustal composition and rheology. Forward modeling suggests these data are sensitive to lithospheric differences predicted by the end-member models. A 2-D analysis of these data has been justified by a careful dimensionality and distortion assessment. A joint inversion of the TE, TM and tipper data produces a model that displays a prominent conductive feature coincident at the surface with the trace of the Lishan Fault. The depth extent of thin-skinned tectonic model. It is difficult to reconcile the thin-skinned model with this continuous vertical conductor from depth. In contrast, the lithospheric deformation model supports such a feature, owing to fluids released from prograde metamorphism within a thickened crust.
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