17:15 〜 19:15
[SGL23-P08] Structural history and kinematic evolution during exhumation processes in the retrowedge: an example from the eastern Central Range, Taiwan
キーワード：Exhumation、Eastern Central Range、Taiwan
Kinematic evolution of exhumation process is always a fascinating mystery for solid earth sciences. Analyses of structures, strain distribution, and P-T-stress state during the exhumation processes in the eastern Central Range of Taiwan provide a unique opportunity to understanding the structural history and kinematic evolution in the retro-wedge of orogenic belts.
It is well known that sub-horizontally along-strike stretching lineation is noticeable on the NE-striking foliation with moderate dip at the eastern Central Range, contrast to the down-dip stretching lineation at the western Central Range. Magnetic fabrics consistent with petro-fabrics provides the strain pattern across the eastern Central Range. With shear-sense indicators, it illustrates that along-strike shearing associated with almost E-W compression took place during ductile and semi-ductile deformation under the strike-slip faulting stress regime, which is still active inferred from current earthquakes. Conversely, later shallow structures including the sub-horizontal crenulation cleavages, listric normal faults and NW-striking sub-vertical joints and quartz veins subparallel to the motion of the Philippine Sea Plate locally cut the foliation throughout the eastern Central Range, displaying that sub-vertical ductile thinning associated with N 20-30E extension was active during semi-brittle and brittle deformation under normal faulting stress regime with NE-extension. The results of fluid inclusions with CO2-H20 system display that these sub-vertical quartz veins were formed at the sub-supercritical conditions of CO2 with 407°C trap temperature and 109MPa trap pressure at the depth of around 5km, where is almost overlapped the depth of earthquakes with strike-slip faulting stress regime.
Variation of kinematics at the brittle-ductile transition might indicate that dynamics changes dramatically in the orogenic exhumation system and might further suggest that the existence of a lid separated brittle behavior from overpressurized ductile deformation to facilitate the exhumation at the eastern Central Range, Taiwan.
It is well known that sub-horizontally along-strike stretching lineation is noticeable on the NE-striking foliation with moderate dip at the eastern Central Range, contrast to the down-dip stretching lineation at the western Central Range. Magnetic fabrics consistent with petro-fabrics provides the strain pattern across the eastern Central Range. With shear-sense indicators, it illustrates that along-strike shearing associated with almost E-W compression took place during ductile and semi-ductile deformation under the strike-slip faulting stress regime, which is still active inferred from current earthquakes. Conversely, later shallow structures including the sub-horizontal crenulation cleavages, listric normal faults and NW-striking sub-vertical joints and quartz veins subparallel to the motion of the Philippine Sea Plate locally cut the foliation throughout the eastern Central Range, displaying that sub-vertical ductile thinning associated with N 20-30E extension was active during semi-brittle and brittle deformation under normal faulting stress regime with NE-extension. The results of fluid inclusions with CO2-H20 system display that these sub-vertical quartz veins were formed at the sub-supercritical conditions of CO2 with 407°C trap temperature and 109MPa trap pressure at the depth of around 5km, where is almost overlapped the depth of earthquakes with strike-slip faulting stress regime.
Variation of kinematics at the brittle-ductile transition might indicate that dynamics changes dramatically in the orogenic exhumation system and might further suggest that the existence of a lid separated brittle behavior from overpressurized ductile deformation to facilitate the exhumation at the eastern Central Range, Taiwan.