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|Title: ||Fault-related rocks from the thrust zone in Miaoli Area, west Taiwan|
|Authors: ||Song S.R.;Chen H. F.;Li L. J.;Liu J.M.;Lo H. J.|
|Contributors: ||NTOU:Institute of Applied Geosciences|
|Issue Date: ||2011-10-20T08:17:34Z
|Publisher: ||2001 AGU (American Geophysical Union) Fall Meeting|
|Abstract: ||abstract:Taiwan is located in the orogenic belt, which the fault-related earthquakes were very common and severe in last few myrs. However, there are no any fault-related rocks have been reported until now. This research is the first article to report an unambiguous occurrence of pseudotachylyte and cataclasite in Taiwan. The fault-related rocks, including the pseudotachylyte and cataclasite have been found in the drilled core, about 600 meters in depth below the surface in the western foothill sedimentary sequences of Miaoli area, Taiwan. The pseudotachylytes are thin, submillimeter to centimeter in thickness and distribute intercalated in thick fault zone. They dominantly occur as injection veins, which contact sharply with host rocks, the sandstones and siltstones, and normal or cut with the major shearing zone. Petrogaphically, the pseudotachylytes consist of a black or dark brown, fine-grained to glassy aphanitic matrix with microlites, rounded or embayed clasts and numerous rock and mineral fragments. The presence of pseudotachylytes indicates that the fault zone has suffered the rapid seismic displacements. The cataclastic rocks include non-foliated clast-supported to matrix-supported cataclasites and foliated clastic-supported cataclasites. The former form either thin dark films underlining isolated shear plane or accumulating as thick lens or pods. The later have large varieties in structures, such as thin dark films displaying S-C fabrics silimar to those of mylonites, injected veins and well-polished slickensided surface. Under the microscope, the muscovite fragments show the structures of brittle-plastic shearing processes, such as fish, cleavage-steps, bending and folding. Those characteristics of cataclasites infer that the cataclasites may form under either the slow seismic movement or aseismic creep. From the occurrence, location and regional geology, this fault zone with abundant fault-related rocks may be correlated to the Shenchoshan thrust fault, which is a seismic fault moved in 1935. The coeval formation of pseudotachylyte and foliated cataclasite infers that the seismic displacement and aseismic creep occurred in the same shear zone.|
|Appears in Collections:||[應用地球科學研究所] 演講及研討會|
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