Jurassic accretionary complexes of the North Kitakami Belt in the Akka-Kuji area, Northeast Japan

Ehiro, Masayuki; Yamakita, Satoshi; Takahashi, Satoshi; Suzuki, Noritoshi

doi:10.5575/geosoc.114.s121

Cited by 27 publications

(43 citation statements)

References 11 publications

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“…Cape Shiriya is located at the northeastern tip of the Honshu (Figure ), and forms part of the North Kitakami Belt. In the North Kitakami Belt, timing of tectonic accretion of sediments, as approximated by the age of trench‐fill clastic deposits, youngs from southwest to northeast (Ehiro, Yamakita, Takahashi, & Suzuki, ; N. Suzuki, Ehiro et al, ). Accretion ages shift from Early Jurassic in the Hirosaki area (H. Ueda et al, ) via dominantly Middle Jurassic in the Kuzumaki–Kamaishi Subbelt (N. Suzuki, Ehiro et al, ; N. Suzuki, Yamakita et al, ; Yoshihara et al, ) and the Late Jurassic Akka–Tanohata Subbelt (A. Matsuoka & Oji, ; Nakae & Kamada, ) of the western and eastern parts of the Kitakami Mountains, respectively, to the Early Cretaceous in the Cape Shiriya area at the northeastern margin (A. Matsuoka, ; this study).…”

Section: Geological Backgroundsmentioning

confidence: 99%

Material recycling in a sediment‐starved trench recorded in the Early Cretaceous Shiriya accretionary complex, Northeast Japan

et al. 2018

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Identifying and examining geological processes that have occurred in sediment‐starved trenches of ancient non‐accretionary subduction zones exposed on land are still challenging, because such style of subduction is believed to leave scarce rock records. Our new geological mapping, petrography of coarse clastic rocks, radiolarian and zircon U–Pb dating of the Shiriya accretionary complex in Northeast Japan suggest that the younger parts (Sr1 unit) of the complex formed in a sediment‐starved trench. The key observation is that debris derived from the inner trench slope directly overlies pelagic chert in many sections where trench turbidites are lacking. A significant mass of turbidites occurring in other sections are also considered to represent distal facies of the debrites from the adjacent inner trench slope, rather than normal trench‐fill turbidites directly supplied from the continental landmass. These recycled materials from the inner trench slope comprised an imbricate frontal accretionary wedge, together with pelagic siliceous deposits of ocean floor origin. This accretionary wedge of debrite origin suggests that mass wasting on inner slopes of sediment‐starved trenches does not always result in tectonic erosion (removal of materials from the upper plate), but results in material recycling to reconstruct a new frontal accretionary wedge. The spatial dimensions of the recycling cell may be one of the critical differences between accretionary and non‐accretionary margins. Recycled continental materials transported by turbidites from remote landmasses construct frontal wedges in accretionary margins, whereas mass wasting on adjacent slopes and re‐accretion at the trench recycle continental materials in non‐accretionary margins. The transition from an accretionary to non‐accretionary (i.e. sediment‐starved) trench detected in the Shiriya Complex potentially records tectonic response of the inner trench slope to increased friction along the subduction interface.

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Section: Geological Backgroundsmentioning

confidence: 99%

Material recycling in a sediment‐starved trench recorded in the Early Cretaceous Shiriya accretionary complex, Northeast Japan

et al. 2018

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“…; Miura & Ishiwatari ; Ehiro et al . ). This massif is bordered to the southwest by a Carboniferous accretionary complex known as the Nedamo belt (Hamano et al .…”

Section: A Review On the Hayachine–miyamori Ophiolite And The Kitakammentioning

confidence: 97%

“…These accretionary complexes have been successively developed above the westward‐dipping subduction from the west to the east since Carboniferous times (Ehiro et al . ).…”

Section: A Review On the Hayachine–miyamori Ophiolite And The Kitakammentioning

confidence: 97%

“…The North Kitakami Massif is a Jurassic accretionary complex Otoh & Sasaki 2003;Ehiro et al 2008; Fig. 1).…”

Section: North Kitakami Massif and The Boundary Zone Of The North Andmentioning

confidence: 99%

“…1). It comprises the early-middle Jurassic accretionary complex of the Kuzumaki-Kamaishi subbelt in the west, including Carboniferous-Permian allochthonous blocks composed of oceanic island basalt and limestone, and the late Jurassic accretionary complex of the Akka-Tanohata subbelt in the east, including Triassic ocean island basalt capped by limestone (Tsuchiya et al 1999;Miura & Ishiwatari 2001;Ehiro et al 2008). This massif is bordered to the southwest by a Carboniferous accretionary complex known as the Nedamo belt (Hamano et al 2002;Ehiro & Suzuki 2003;Uchino et al 2005;2008a;Uchino & Kawamura 2010;Kawamura et al 2013; Fig.…”

Section: North Kitakami Massif and The Boundary Zone Of The North Andmentioning

confidence: 99%

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Evolution processes of Ordovician–Devonian arc system in the South‐Kitakami Massif and its relevance to the Ordovician ophiolite pulse

et al. 2015

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The South Kitakami Massif is one of the oldest geological domains in Japan having Silurian strata with acidic pyroclastic rocks and Ordovician–Silurian granodiorite–tonalite basement, suggesting that it was matured enough to develop acidic volcanisms in the Silurian period. On the northern and western margin of the South Kitakami Massif, an Ordovician arc ophiolite (Hayachine–Miyamori Ophiolite) and high‐pressure and low‐temperature metamorphic rocks (Motai metamorphic rocks) exhumed sometime in the Ordovician–Devonian periods are distributed. Chronological, geological, and petrochemical studies on the Hayachine–Miyamori Ophiolite, Motai metamorphic rocks, and other early Paleozoic geological units of the South Kitakami Massif are reviewed for reconstruction of the South Kitakami arc system during Ordovician to Devonian times with supplementary new data. The reconstruction suggests a change in the convergence polarity from eastward‐ to westward‐dipping subduction sometime before the Late Devonian period. The Hayachine–Miyamori Ophiolite was developed above the eastward‐dipping subduction through three distinctive stages. Two separate stages of overriding plate extension inducing decompressional melting with minor involvement of slab‐derived fluid occurred before and after a stage of melting under strong influence of slab‐derived fluids. The first overriding plate extension took place in the back‐arc side forming a back‐arc basin. The second one took place immediately before the ophiolite exhumation and near the fore‐arc region. We postulate that the second decompressional melting was triggered by slab breakoff, which was preceded by slab rollback inducing trench‐parallel wedge mantle flow and non‐steady fluid and heat transport leaving exceptionally hydrous residual mantle. The formation history of the Hayachine–Miyamori Ophiolite implies that weaker plate coupling may provide preferential conditions for exhumation of very hydrous mantle. Very hydrous peridotites involved in arc magmatism have not yet been discovered except for in the Cambrian–Ordovician periods, suggesting its implications for global geodynamics, such as the thermal state and water circulation in the mantle.

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Preservation of Permian–Triassic boundary section in the Jurassic accretionary complex of the Lake Hamana, Central Japan

2020

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We examined the lithostratigraphy and deformation structures of the accreted pelagic rocks in Lake Hamana area, Central Japan, based on a detailed field mapping and the radiolarian ages. The constructed lithostratigraphy is composed of Lopingian (Upper Permian) grey chert, black chert, black claystone with a high carbon content of 4.85-6.78 wt%, siliceous claystone, black chert, and Anisian (Middle Triassic) grey chert, in the ascending order. The symmetry in the lithostratigraphy and the change in the radiolarian ages with respect to black carbonaceous claystone are presumed to represent a deep-sea anoxic event that occurred across the Permian-Triassic (P-Tr) boundary. The P-Tr boundary black carbonaceous claystone suffered from an intense shear, resulting in blocks of siliceous claystone in the scaly black claystone matrix. In places, the sheared terrigenous rocks composed of sandstone blocks in the mudstone matrix are intercalated into the pelagic rocks, possibly representing complex mélange forming processes during the development of the Jurassic accretionary complex.

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Jurassic accretionary complexes of the North Kitakami Belt in the Akka-Kuji area, Northeast Japan

Cited by 27 publications

References 11 publications

Material recycling in a sediment‐starved trench recorded in the Early Cretaceous Shiriya accretionary complex, Northeast Japan

Material recycling in a sediment‐starved trench recorded in the Early Cretaceous Shiriya accretionary complex, Northeast Japan

Evolution processes of Ordovician–Devonian arc system in the South‐Kitakami Massif and its relevance to the Ordovician ophiolite pulse

Preservation of Permian–Triassic boundary section in the Jurassic accretionary complex of the Lake Hamana, Central Japan

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