HR: 09:15h
AN: T41D-06 INVITED    [Abstracts]
TI: Evolution of Subductions Indicated by Mélanges in Taiwan
AU: * Chang, C
EM: cpchang@csrsr.ncu.edu.tw
AF: Center for Space and Remote Sensing Research, National Central University, 300, Jungda Rd., Jungli, Taoyuan, 320, Taiwan
AU: Angelier, J
EM: angelier@geoazur.obs-vlfr.fr
AF: Géosciences Azur, Observatoire Océanologique de Villefranche, Université Pierre-et-Marie- Curie, BP 48, La Darse, Villefranche/Mer, 06235, France
AU: Huang, C
EM: huangcy@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, 1, Dahsueh Rd., Tainan, 701, Taiwan
AB: Two mélange zones occur in Taiwan, the Lichi Mélange in the Coastal Range of eastern Taiwan and the Kenting Mélange in the Hengchun Peninsula of southern Taiwan. Because of the the southward propagation of the Taiwan orogen, these two mélanges now crop out at the western front of the Coastal Range (Lichi Mélange) and the west side of the southern Central Range (Kenting Mélange). These two mélanges are similar in appearance and controversial in origin, being interpreted either as subduction complexes, or as olistostromes. Remnants of neighbouring stratigraphic units, present as slices or clasts in the mélange zones, shed light on the nature and origin of these two mélanges and help deciphering the tectonic evolution of Taiwan orogen and its leading subductions. Based on multiple lines of evidence, including fossil age, clay mineral composition and nature of exotic ophiolitic blocks, we conclude that the Kenting Mélange zone, which was probably active over a longer period of Late Cenozoic time, was a direct result of subduction process, as a relict of subduction fault zone at the front of the Taiwan accretionary prism. The Lichi Mélange, for which the fossil age indicates a shorter Pliocene time span, was part of the Northern Luzon Trough forearc, is regarded as a collision mélange formed during forearc closure in probable relation with arcward backthrusting, when the Luzon arc started to collide with the Eurasian continent margin following subduction of the oceanic crust of the forearc area. After comparing the geological situation of these two mélanges, we obtain a new perspective for the evolution of a trench-prism system, from subduction to arc-continent collision.
DE: 8104 Continental margins: convergent
DE: 8108 Continental tectonics: compressional
DE: 8140 Ophiolites (3042)
DE: 8150 Plate boundary: general (3040)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting