Dating palaeo‐seismic faulting in the Taiwan Mountain Belt

Chen, Chih Tung; Wu, C.; Lo, Ching–Hua; Chu, Hao‐Tsu; Yui, Tzen‐Fu

doi:10.1111/ter.12319

Cited by 5 publications

(3 citation statements)

References 27 publications

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“…The possibilities of normal faulting activities in the surrounding area of northeast Taiwan have been reported. For instance, the occurrence of pseudotachylyte veins is believed to be associated with the exhumation-related extension during ~1.5 Ma (Korren et al 2017;Chen et al 2018). As Dewey (1988) elaborated, gravitational sliding or gravitational spreading at shallow crust often occurs in the post-collisional orogens when the lithosphere fails to maintain stability.…”

Section: Exhumation History Between 41 and 02 Ma And Offset In Agesmentioning

confidence: 99%

Post-collisional exhumation and geotherm pattern in northern Tananao Complex, northeastern Taiwan

Shen¹,

Liu²,

Huang³

et al. 2020

Terr. Atmos. Ocean. Sci.

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The northeast region of Taiwan has experienced a stress transition from the compressive collision to the extension induced from the Ryukyu subduction system in a post-collisional orogenic belt. In order to clarify when the extensional stage began and how the cooling and exhumation history varied with the transition of tectonic stress, apatite and zircon fission-track ages on the granitic gneiss in northern Tananao Complex were collected from a ~2700 m high sub-vertical profile. The exhumation rate was estimated as ~4 mm yr-1 since 4.1-3.0 Ma using previous biotite 40 Ar-39 Ar ages with an assumed uniform geothermal gradient. During the period of 1.5-0.2 Ma, the exhumation rate remained at 2.3-1.6 mm yr-1 , evidenced by the similar slopes for apatite and zircon in the age-elevation relationship (AER). The decrease in exhumation occurred in between 3.0 and 1.5 Ma is interpreted as the onset of the extensional impact into NE Taiwan from the Ryukyu subduction zone. After ~0.2 Ma, the intercepts of apatite AER suggest that exhumation accelerated to ~5 mm yr-1 at the mountain range but was steady at the valley bottom. The offset in ages of the vertical profile is supportive of the normal faulting at the shallow crust. The accelerating cooling with the steady exhumation from 1.5-0.2 Ma implies the increase in paleogeothermal gradient with time. The paleogeothermal gradients are estimated to be over 100°C km-1 after 1.5 Ma, suggesting that the Hoping area possesses heat sources induced from the complex tectonic configuration. However, the modern geotherm is relatively low and may be influenced by the water circulation near surface.

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Section: Exhumation History Between 41 and 02 Ma And Offset In Agesmentioning

confidence: 99%

Post-collisional exhumation and geotherm pattern in northern Tananao Complex, northeastern Taiwan

Shen¹,

Liu²,

Huang³

et al. 2020

Terr. Atmos. Ocean. Sci.

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“…The fault zone rocks are mainly cataclasites and mylonites overprinted by pseudotachylytes. Pseudotachylytes were generated at depths >4 km about 1.6 Ma ago (Chen et al, 2017) in faults accommodating displacements by up to 220 mm (corresponding to earthquakes of M W 6.4 ± 0.4 if all the displacement would be associated to a single seismic slip event; Korren et al, 2016). Pseudotachylytes form vein and injection veins networks that intrude the host granitic gneiss, and they were used to infer earthquake source parameters (e.g., slip vectors (Korren et al, 2016) and brushlines (Ferré et al, 2016)).…”

Section: Starting Materialsmentioning

confidence: 99%

Grain Fragmentation and Frictional Melting During Initial Experimental Deformation and Implications for Seismic Slip at Shallow Depths

et al. 2019

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During seismic slip, the elastic strain energy released by the wall rocks drives grain fragmentation and flash heating in the slipping zone, resulting in formation of (nano)powders and melt droplets, which lower the fault resistance. With progressive seismic slip, the frictional melt covers the slip surface and behaves as a lubricant reducing the coseismic fault strength. However, the processes associated to the transition from grain fragmentation to bulk frictional melting remain poorly understood. Here we discuss in situ microanalytical investigations performed on experimentally produced solidified frictional melts from the transition regime between grain fragmentation and frictional melting. The experiments were performed on granitic gneiss at seismic slip rates (1.3 and 5 m/s), normal stresses ranging from 3 to 30 MPa. At normal stresses <12 MPa, the apparent friction coefficient μ app (shear stress versus normal stress) evolves in a complex manner with slip: μ app decreases because of flash weakening, increases up to a peak value μ p1~0 .6-1.0, slightly decreases and increases again to a second peak value μ p2~0 .44-0.83, and eventually decreases with displacement to a steady-state value μ ss~0 .3-0.45. In situ synchrotron observations of the solidified frictional melt show abundance of ultrafine quartz grains before μ p2 and enrichment in SiO 2 at μ p2 . Because partial melting occurs on the ultrafine quartz grains and, as a consequence, it suggested that the second re-strengthening (μ p2 ) is induced by the higher viscosity of the melt due to its enrichment in Si from melting of the ultrafine quartz grains derived from grain fragmentation. Key Points:• Granitic rocks sheared at seismic slip velocities and low normal stress show double-strengthening friction evolution before final weakening • Particle size distribution constrained by in situ synchrotron analysis shows the presence of additive ultrafine quartz grains • The re-strengthening was due to viscous frictional melts by quasi-equilibrium melting and the Gibbs-Thomson effect on quartz grains

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“…Normal-faulting paleo-earthquakes recorded by pseudotachylite veins offsetting mylonitic foliation were also dated at ca. 1.55 Ma (Chen et al, 2018b). Accompanying the extension was fast and accelerating exhumation of 2-4 mm/yr to 4-8 mm/ yr starting at ca.…”

Section: The Hoping Structural Complexmentioning

confidence: 99%

Extensional mountain building along convergent plate boundary: Insights from the active Taiwan mountain belt

Chen

Wang

et al. 2022

Geology

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Late brittle extension is a common feature in orogenic belts, and its role in mountain building processes is still the subject of debate. Its timing relationship with crustal thickening, the building of topography, basin infill, and rock exhumation are of key importance in determining whether it is a major factor in orogenic development or merely causes near-surface secondary effects. We examined this question in relation to the active arc-continent collision of Taiwan, studying its structural evolution by integrating new and critical geochronological results for tensile vein filling of hinterland metamorphic terrane with syn-collision deposition records. Acceleration of rock exhumation and molasse deposition was found to be coeval with the initiation of brittle tensile structures at ca. 1.6 Ma, which was long overdue as continental subduction started well before 6.5 Ma in central to northern Taiwan. The topographic mountain of Taiwan was thus constructed when the upper crust of the thickened orogenic prism turned extensional, as orographic elevation and relief are prerequisites for molasses production. Syn-collisional brittle extension is therefore proposed as a possible facilitator of both augmented extrusive exhumation and the formation of orography.

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Dating palaeo‐seismic faulting in the Taiwan Mountain Belt

Cited by 5 publications

References 27 publications

Post-collisional exhumation and geotherm pattern in northern Tananao Complex, northeastern Taiwan

Post-collisional exhumation and geotherm pattern in northern Tananao Complex, northeastern Taiwan

Grain Fragmentation and Frictional Melting During Initial Experimental Deformation and Implications for Seismic Slip at Shallow Depths

Extensional mountain building along convergent plate boundary: Insights from the active Taiwan mountain belt

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