Erosion rates and orogenic-wedge kinematics in Taiwan inferred from fission-track thermochronometry

New apatite and zircon fission-track ages and previously published thermochronometric data are used to evaluate erosion rates and particle paths within the active Taiwan arc-continent collision. We present 20 new apatite fission-track ages and 6 new zircon fission-track ages. Apatite and zircon ages are all reset in the northern and eastern parts of Taiwan, although the region of reset apatite ages is larger. We interpret this pattern as resulting from crustal accretion at the western margin of the orogenic wedge combined with southward propagation of the collision zone. A one-dimensional thermal model including erosion provides prediction of the fission-track ages. The distribution of reset ages is best explained with an erosion rate of 4-6 mm/yr. Given a propagation velocity of 60 mm/yr, this erosion rate implies that nearly 25 km of material has been eroded from northern Taiwan. The lack of reset 40Ar/39Ar ages from muscovite and biotite suggests that rock-particle paths have a large horizontal component, a result consistent with an eroding orogenic-wedge model.