Occurrence and significance of in-situ greenstones from the Mugi Formation in the Upper Cretaceous Shimanto Supergroup, eastern Shikoku, Japan.

和雄, 君波; 庸孝, 柏木; 純夫, 宮下

doi:10.5575/geosoc.98.867

Cited by 36 publications

(44 citation statements)

References 16 publications

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“…The zircon UePb ages of tuff layers in the upper section range from 66.2 ± 3.5 to 73.2 ± 3.6 Ma, while ages in the lower section range from 58.3 ± 3.4 to 63.8 ± 2.2 Ma (Shibata et al, 2008). These ages are consistent with the biostratigraphy (Kiminami et al, 1992). The maximum burial temperature, determined from vitrinite reflectance (Ro), is 170e200 C in the upper section (2.5% < Ro < 3.2%) Kitamura et al, 2005) and 130e150 C in the lower section (1.0% < Ro < 1.8%) (Ohmori et al, 1997;Matsumura et al, 2003).…”

Section: The Mugi M Elangesupporting

confidence: 75%

“…Lithological differences and radiolarian fossils suggest that the Mugi M elange and the Kainan Formation are separated by the Aki Tectonic Line (Kiminami et al, 1992). The northernmost part of the m elange is bounded by the Minami-Awa Fault, which we now describe in detail.…”

Section: The Mugi M Elangementioning

confidence: 95%

“…It consists mainly of sheared dark-gray shale (herein the m elange matrix shale) containing sandstone blocks. Other lithologies in the Mugi M elange include oceanic basalt, red and varicolored hemipelagic shales, pelagic chert, and acidic tuff (Kumon, 1981;Kiminami et al, 1992;Onishi and Kimura, 1995;Ikesawa et al, 2005).…”

Section: The Mugi M Elangementioning

confidence: 99%

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Complete 40Ar resetting in an ultracataclasite by reactivation of a fossil seismogenic fault along the subducting plate interface in the Mugi Mélange of the Shimanto accretionary complex, southwest Japan

Tonai

Ito

Hashimoto

et al. 2016

Journal of Structural Geology

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Section: The Mugi M Elangesupporting

confidence: 75%

Section: The Mugi M Elangementioning

confidence: 95%

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Complete 40Ar resetting in an ultracataclasite by reactivation of a fossil seismogenic fault along the subducting plate interface in the Mugi Mélange of the Shimanto accretionary complex, southwest Japan

Tonai

Ito

Hashimoto

et al. 2016

Journal of Structural Geology

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“…3). Basaltic dykes with chilled contacts and xenoliths of hemipelagic rocks are also observed (Kiminami et al 1992). The hemipelagic rocks are overlain by alternating sandstone and mudstone, and the succession is repeated by seaward vergent thrusting.…”

Section: Late Cretaceous Ridge Subductionmentioning

confidence: 96%

“…Ridge subduction that formed the Mugi sub-belt is also evidenced by the near trench magmatism (Kiminami et al 1992) (Fig. 3).…”

Section: Late Cretaceous Ridge Subductionmentioning

confidence: 96%

Normal faults in an accretionary complex formed at trench‐trench‐ridge triple junction, as an indicator of angle between the trench and subducted ridge

Osozawa

1993

Island Arc

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Normal faults parallel to the trend of an active ridge are formed in the accretionary prism at trench-trench-ridge triple junction, due to continuous spreading of the subducted ridge. Normal faults are observed in the Nabae and Mugi sub-belts, accretionary zones formed by ridge subduction in the Shimanto Belt. Igneous and sedimentary dykes intrude through the previous normal faults. Using these fault and dyke data, intermediate principal axis of stress relating to the normal faulting is determined, and is fitted to the trend of the subducted ridge.Normal faults formed by ridge subduction are useful for plate reconstruction.

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Missing western half of the Pacific Plate: Geochemical nature of the Izanagi‐Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

Miyazaki

Kimura

Senda

et al. 2015

Geochem Geophys Geosyst

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The source mantle of the basaltic ocean crust on the western half of the Pacific Plate was examined using Pb-Nd-Hf isotopes. The results showed that the subducted Izanagi-Pacific Ridge (IPR) formed from both Pacific (180-80 Ma) and Indian (80-70 Ma) mantles. The western Pacific Plate becomes younger westward and is thought to have formed from the IPR. The ridge was subducted along the KurileJapan-Nankai-Ryukyu (KJNR) Trench at 60-55 Ma and leading edge of the Pacific Plate is currently stagnated in the mantle transition zone. Conversely, the entire eastern half of the Pacific Plate, formed from isotopically distinct Pacific mantle along the East Pacific Rise and the Juan de Fuca Ridge, largely remains on the seafloor. The subducted IPR is inaccessible; therefore, questions regarding which mantle might be responsible for the formation of the western half of the Pacific Plate remain controversial. Knowing the source of the IPR basalts provides insight into the Indian-Pacific mantle boundary before the Cenozoic. Isotopic compositions of the basalts from borehole cores (165-130 Ma) in the western Pacific show that the surface oceanic crust is of Pacific mantle origin. However, the accreted ocean floor basalts in the accretionary prism along the KJNR Trench have Indian mantle signatures. This indicates the younger western Pacific Plate of IPR origin formed partly from Indian mantle and that the Indian-Pacific mantle boundary has been stationary in the western Pacific at least since the Cretaceous.

show abstract

Occurrence and significance of in-situ greenstones from the Mugi Formation in the Upper Cretaceous Shimanto Supergroup, eastern Shikoku, Japan.

Cited by 36 publications

References 16 publications

Complete 40Ar resetting in an ultracataclasite by reactivation of a fossil seismogenic fault along the subducting plate interface in the Mugi Mélange of the Shimanto accretionary complex, southwest Japan

Complete 40Ar resetting in an ultracataclasite by reactivation of a fossil seismogenic fault along the subducting plate interface in the Mugi Mélange of the Shimanto accretionary complex, southwest Japan

Normal faults in an accretionary complex formed at trench‐trench‐ridge triple junction, as an indicator of angle between the trench and subducted ridge

Missing western half of the Pacific Plate: Geochemical nature of the Izanagi‐Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

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