Mid-crustal horizontal shear zone in the forearc region of the mid-Cretaceous SW Japan arc, inferred from strain analysis of rocks within the Ryoke metamorphic belt

Okudaira, Takamoto; Beppu, Yuki; Yano, Ryosuke; Tsuyama, Mio; Ishii, Kazuhiko

doi:10.1016/j.jseaes.2008.11.015

Cited by 24 publications

(15 citation statements)

References 45 publications

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“…Correlation between outcrop and borehole data indicates that the MTL in the study area dips to the north at~56° (Shigematsu et al 2012). The Hatai Tonalite, a unit within the Ryoke Belt, crops out to the north of the MTL and was mylonitised during left-lateral deformation (Hayama et al 1982;Takagi 1985;Nakajima 1994;Sakakibara 1996;Shimada et al 1998;Suzuki and Adachi 1998;Okudaira et al 2009). A wide mylonite zone (~1-2 km), interpreted to represent the deep portion of the MTL, initially formed while the Hatai Tonalite was hot (~450°C-500°C), and deformation then localised under lower temperatures (~300°C-400°C) at c. 63-62 Ma (Takagi 1986;Dallmeyer and Takasu 1991;Michibayashi and Masuda 1993;Yamamoto 1994;Sakakibara 1996;Shimada et al 1998).…”

Section: Geological Settingmentioning

confidence: 87%

The architecture of long-lived fault zones: insights from microstructure and quartz lattice-preferred orientations in mylonites of the Median Tectonic Line, SW Japan

Czertowicz

Takeshita

Arai

et al. 2019

Prog Earth Planet Sci

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We combine field mapping with quartz microstructure and lattice preferred orientations (LPO) to constrain the mechanisms and spatio-temporal distribution of deformation surrounding the Median Tectonic Line (MTL), SW Japan. In the study area, the MTL occurs either as a narrow gouge zone or as a sharp contact between hangingwall quartzofeldspathic mylonites to the north and footwall pelitic schists to the south. Along the northern margin of the MTL, there exists a broad zone of mylonitic rocks, overprinted by cataclastic deformation and a damage zone associated with brittle deformation. The mylonitic shear zone is dominated by coarse-grained protomylonite up to~100 m from the MTL, where fine-grained ultramylonite becomes dominant. We observe a systematic variation in quartz LPO with distance from the MTL. In protomylonites, quartz LPOs are dominantly Y-maxima patterns, recording dislocation creep by prism slip at~500°C. Closer to the MTL, we observe Rand Z-maxima, and single and crossed girdles, reflecting dislocation creep accommodated by mixed rhomb and basal slip, likely under cooler conditions (~300°C-400°C). Some ultramylonite samples yield weak to random LPOs, interpreted to result from the influx of fluid into the shear zone, which promoted deformation by grainsize-sensitive creep. Following cooling and uplift, deformation became brittle, resulting in the development of a narrow cataclasite zone. The cataclasite was weakened through the development of a phyllosilicate foliation. However, healing of fractures strengthened the cataclasites, resulting in the development of anastomosing cataclasite bands within the protomylonite.

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Section: Geological Settingmentioning

confidence: 87%

The architecture of long-lived fault zones: insights from microstructure and quartz lattice-preferred orientations in mylonites of the Median Tectonic Line, SW Japan

Czertowicz

Takeshita

Arai

et al. 2019

Prog Earth Planet Sci

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“…Seismic reflection profiles across the MTL indicate that it dips to the north [ Ito et al , 2009]. A broad mylonite zone was formed within the Ryoke metamorphic belt during sinistral top‐to‐the‐west shearing along the MTL in the Late Cretaceous [ Takagi , 1985; Yamamoto , 1994; Sakakibara , 1995, 1996; Shimada et al , 1998; Okudaira et al , 2009]. It has been suggested that mylonites formed in a wide zone of ∼1–2 km along the MTL at high temperatures of ∼450–500°C, as inferred from the temperature of deformation‐controlled myrmekite replacement [ Michibayashi and Masuda , 1993; Sakakibara , 1996].…”

Section: Samplesmentioning

confidence: 99%

Estimates of stress and strain rate in mylonites based on the boundary between the fields of grain‐size sensitive and insensitive creep

Okudaira¹,

Shigematsu²

2012

J. Geophys. Res.

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[1] Microstructural analyses of mylonites next to the Median Tectonic Line (MTL), SW Japan, reveal a transition in the dominant deformation mechanism of quartz from grain-size-insensitive dislocation creep to grain-size-sensitive grain-boundary sliding (GBS). The transition occurred under greenschist-facies conditions ($300-400 C) during grain-size reduction by dynamic recrystallization. The stereologically corrected grain size for the transition is approximately 4.3 mm. At the boundary between the fields of dislocation creep and GBS, as calculated from creep constitutive relations, the differential stress and strain rate for this corrected grain size are estimated to be $280 MPa and 1.2 Â 10 À11 s À1 for 300 C, and $110 MPa and 1.0 Â 10 À10 s À1 for 400 C. The strain rates estimated for the mylonites next to the MTL are much higher than those estimated for the surrounding metamorphic rocks ($10 À14 s À1), and the displacement rates calculated based on the thickness of high-strain mylonites and their strain rates are comparable with the average slip rates of the most active intraplate faults in Japan. These inferences suggest that the high-strain mylonite zones next to the MTL are the exhumed downward extension of a seismogenic fault in the ductile region. The zones were highly localized (<10 m) and experienced very high strain rates (10 À11 to 10 À10 s À1 ).Citation: Okudaira, T., and N. Shigematsu (2012), Estimates of stress and strain rate in mylonites based on the boundary between the fields of grain-size sensitive and insensitive creep,

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“…However, the south wing lacks most of the low metamorphic facies (chlorite–biotite and biotite zone) because they are cut by the MTL (Suwa, ). Mylonitization developed in the southern margin of the Ryoke Metamorphic Belt along and within (< 1 km in width) the MTL (Okudaira et al, ). The mylonites were formed with the uplift (Okudaira et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Activity of the Ryoke granitic intrusion continued to ca 85 Ma in western part and ca 75 Ma in eastern part of the belt (Suzuki & Adachi, ; Yuhara, Kagami, & Nagao, ). After or during intrusion of granitic magmas, localized deformations occurred in the southern margin of the Ryoke Metamorphic Belt (Okudaira, Beppu, Yano, Tsuyama, & Ishii, ). These deformations were largely related to its uplift (Okudaira & Suda, ).…”

Section: Introductionmentioning

confidence: 99%

Late Cretaceous uplift history of the Cretaceous volcanic arc in Southwest Japan: Provenance analysis of the Yuasa–Aridagawa basin based on U–Pb zircon ages

2018

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The Ryoke Metamorphic complex has undergone low‐P/T metamorphism and was intruded by granitic magmas around 100 Ma. Subsequently, the belt was uplifted and exposed by the time deposition of the Izumi Group began. The tectonic history of uplift, such as the timing and processes, are poorly known despite being important for understanding the spatiotemporal evolution of the Ryoke Metamorphic Belt. U–Pb zircon ages from sedimentary rocks in the forearc and backarc basins are useful for constraining uplift and magmatism in the provenance. U–Pb dating of detrital zircons from 12 samples (four sandstones and eight granitic clasts) in the Yuasa–Aridagawa basin, a Cretaceous forearc basin in the Chichibu Belt of Southwest Japan, gave mostly ages of 60–110 Ma. Granitic clasts contained in conglomerate suggest that granitic intrusions predate the formation of Coniacian and Maastrichtian conglomerate. Emplacement ages of granitic bodies originated from granitic clasts in Coniacian conglomerate are (110.2 ±1.3) Ma, (106.1 ±1.8) Ma, (101.8+5.8–3.8) Ma, and (95.3 ±1.4) Ma; for granitic clasts in Maastrichtian conglomerate, (89.6 ±1.8) Ma, (87.3+2.4–1.8) Ma, (85.7 ±1.2) Ma, and (82.7 ±1.2) Ma. The results suggest that detrital zircons in the sandstones were mainly derived from volcanic eruptions contemporaneous with depositional age, and plutonic rocks of the Ryoke Metamorphic Belt. Zircon ages of the granitic clast samples also indicate that uplift in the provenance began after Albian and occurred at least during the Coniacian to Maastrichtian. Our results, together with the difference of provenance between backarc and forearc basins suggest that the southern marginal zone of the Ryoke Metamorphic Belt was uplifted and supplied a large amount of clastic materials to the forearc basins during the Late Cretaceous.

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Mid-crustal horizontal shear zone in the forearc region of the mid-Cretaceous SW Japan arc, inferred from strain analysis of rocks within the Ryoke metamorphic belt

Cited by 24 publications

References 45 publications

The architecture of long-lived fault zones: insights from microstructure and quartz lattice-preferred orientations in mylonites of the Median Tectonic Line, SW Japan

The architecture of long-lived fault zones: insights from microstructure and quartz lattice-preferred orientations in mylonites of the Median Tectonic Line, SW Japan

Estimates of stress and strain rate in mylonites based on the boundary between the fields of grain‐size sensitive and insensitive creep

Late Cretaceous uplift history of the Cretaceous volcanic arc in Southwest Japan: Provenance analysis of the Yuasa–Aridagawa basin based on U–Pb zircon ages

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