Simoes, Martine and Avouac, Jean Philippe and Beyssac, Olivier and Goffé, Bruno and Farley, Kenneth A. and Chen, Yue-Gau (2007) Mountain building in Taiwan: A thermokinematic model. Journal of Geophysical Research B, 112 (B11). Art. No. B11405. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20101115-093735810
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The Taiwan mountain belt is classically viewed as a case example of a critical wedge growing essentially by frontal accretion and therefore submitted to distributed shortening. However, a number of observations call for a significant contribution of underplating to the growth of the orogenic wedge. We propose here a new thermokinematic model of the Taiwan mountain belt reconciling existing kinematic, thermometric and thermochronological constraints. In this model, shortening across the orogen is absorbed by slip on the most frontal faults of the foothills. Crustal thickening and exhumation are sustained by underplating beneath the easternmost portion of the wedge (Tananao Complex, TC), where the uplift rate is estimated to ~6.3 mm a^(−1), and beneath the westernmost internal region of the orogen (Hsueshan Range units, HR), where the uplift rate is estimated to ~4.2 mm a^(−1). Our model suggests that the TC units experienced a synchronous evolution along strike despite the southward propagation of the collision. It also indicates that they have reached a steady state in terms of cooling ages but not in terms of peak metamorphic temperatures. Exhumation of the HR units increases northward but has not yet reached an exhumational steady state. Presently, frontal accretion accounts for less than ~10% of the incoming flux of material into the orogen, although there is indication that it was contributing substantially more (~80%) before 4 Ma. The incoming flux of material accreted beneath the TC significantly increased 1.5 Ma ago. Our results also suggest that the flux of material accreted to the orogen corresponds to the top ~7 km of the upper crust of the underthrust Chinese margin. This indicates that a significant amount (~76%) of the underthrust material has been subducted into the mantle, probably because of the increase in density associated with metamorphism. We also show that the density distribution resulting from metamorphism within the orogenic wedge explains well the topography and the gravity field. By combining available geological data on the thermal and kinematic evolution of the wedge, our study sheds new light onto mountain building processes in Taiwan and allows for reappraising the initial structural architecture of the passive margin.
|Additional Information:||© 2007 American Geophysical Union. Received 30 October 2006; revised 18 June 2007; accepted 6 July 2007; published 28 November 2007. M.S. wishes to thank Pierre Henry and Laurent Bollinger for introducing her to the FEAP program used in modeling the evolution of the Taiwan mountain belt. Heat flow data were kindly provided by Kuo-Fong Ma and T.-R. A. Song. We are also grateful to Horng-Yuan Yen for providing Bouguer anomaly data corrected for the surface density of 2.76 and to Yi-Min Wu for providing relocalized seismicity data. This manuscript improved thanks to the comments by Steven Kidder and the thoughtful discussions with John Suppe. It also benefited from the constructive reviews of Tim Byrne, Don Fisher, and Jacques Malavieille, as well as from the comments of the AE Gregory Moore. This study has been partly funded by the Gordon and Betty Moore Foundation. This is Caltech Tectonics Observatory contribution 73.|
|Group:||Caltech Tectonics Observatory, Caltech Tectonics Observatory. Taiwan Tectonics and Seismicity|
|Subject Keywords:||mountain building; kinematics; exhumation; thermal structure; Taiwan|
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|Official Citation:||Simoes, M., J. P. Avouac, O. Beyssac, B. Goffé, K. A. Farley, and Y.-G. Chen (2007), Mountain building in Taiwan: A thermokinematic model, J. Geophys. Res., 112, B11405, doi:10.1029/2006JB004824|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||16 Nov 2010 00:02|
|Last Modified:||26 Dec 2012 12:38|
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