Dating palaeo‐seismic faulting in the Taiwan Mountain Belt |
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| Authors: | Chih‐Tung Chen Chieh‐Yu Wu Ching‐Hua Lo Hao‐Tsu Chu Tzen‐Fu Yui |
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| Institution: | 1. Department of Earth Sciences, National Central University, Zhongli, Taiwan, R.O.C.;2. Department of Geosciences, National Taiwan University, Taipei, Taiwan, R.O.C.;3. Institute of Applied Geology, National Central University, Zhongli, Taiwan, R.O.C.;4. Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, R.O.C. |
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| Abstract: | In‐situ 40Ar/39Ar laser microprobe dating was carried out on the Hoping pseudotachylite from a mylonite‐fault zone in the metamorphosed basement complex of the active Taiwan Mountain Belt to determine the timing of the responsible earthquake(s). The dating results, distributed from 3.2 to 1.6 Ma with errors ranging from 0.2 to 1.1 Ma, were derived from a combination of two Ar isotopic system end‐members with inverse isochron ages of 1.55 ± 0.05 and 2.87 ± 0.07 Ma, respectively. Petrographical observations reveal fault melt containing ultracataclasites, therefore the older inverse isochron end‐member may be attributed to the relic wall rock Ar isotopic system contained in micro‐breccia. Without significant Ar loss expected, the ~1.6 Ma for the young end‐member defines the exact time of the pseudotachylite formation. Seismic faulting therefore occurred during basement rock exhumation in the Taiwanese hinterland. |
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