Exhumation history of the Yushan area- the highest peak of the Taiwan Orogenic belt in Central Taiwan

Taiwan Orogeny to be the result of an oblique arc-continental collision between the Philippine Sea Plate and Eurasia Plate. This collision results in that there are more than 100 peaks of mountain are high than 3000 m. This Yushan is located on Central part of Taiwan Orogenic belt and its elevation is 3952 m which is the highest mountain around the Taiwan area. Although there are some fission track data to study the erosion rate or exhumation rate of mountain area, but there is no any data around the Yushan area. In order to identify the exhumation history of the Yushan area we use the zircon and apatite fission track dating method. The total reset zone of zircon fission track is limit in western side of Dili fault and the highest peak of Yushan and surrounding area all show total reset. The zircon fission track age of the Yushan is 5.6 Ma and the other lower topographic area shows from 3.7 to 5.3 Ma. Assuming the geothermal gradient is 30¢J and the annealing temperature of zircon fission track is 235¢J, the average exhumation rate is near 1.28 mm/yr from 5.6 Ma to now. This average exhumation rate is rather lower comparing with other area. We supposed that the later stage exhumation rate will accelerate and we will identify by following apatite fission track dating.