Genesis of the Poroshiri ophiolite, Hokkaido, Japan; Inference from geochemical evidence

Miyashita, Sumio; Adachi, Yoshiko; Tanaka, Shinji; Nakagawa, Mitsuhiro; Kimura, Jun-Ichi

doi:10.5575/geosoc.113.212

Cited by 8 publications

(4 citation statements)

References 27 publications

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“…1 km --, 1994, 1994 --- Niida, 1981 , 2007 Fig Miyashita and Hashimoto, 1975;, 1983 Fig. 5l Miyashita and Niida 19811983Miyashita et al 1994, 2007 Miyashita and Niida (1981), Miyashita et al (1994Miyashita et al ( , 1997 Fig. 11a A C1 An% 0.7 45.4% A Table . Representative amphibole analyses showing compositional zoning in porphyroclast cores and rims and in matrix amphiboles within upper schistose amphibolite in the Chiroro River area.…”

Section: D0mentioning

confidence: 98%

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Geology and metamorphism in the northern Poroshiri ophiolite, Hokkaido, Japan

Tanaka

Kizaki²,

Miyashita

2012

Jour. Geol. Soc. Japan

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The Poroshiri ophiolite is exposed on the western side of the Hidaka metamorphic belt in central Hokkaido, Japan. Here, we present a study of metamorphism in the northern part of the ophiolite, in the Chiroro River area, to determine the relationship between metamorphism and large-scale folding and faulting. Along the northern E-W transect, the ophiolite succession in the western area forms an isoclinal anticline, whereas the eastern area of the transect shows an open syncline. Along the southern E-W transect, the upper sequence of the ophiolite is exposed in the eastern part of the transect along a NW-SE trending thrust fault. The metamorphic grades in these areas change sharply from greenschist to amphibolite facies at the western margin, then gently increases to °C towards the central fault in the northern transect, whereas the metamorphic temperature to the east of this central fault is around °C, indicating a temperature gap of about °C at the central fault. The folded structure of the ophiolite along the northern transect is discordant with the metamorphic thermal structure, indicating that peak metamorphism occurred after folding. This also indicates that the central fault must have been active after peak metamorphism to cause the temperature gap recorded in the northern transect. The metamorphic temperature of the upper sequence of the ophiolite in the eastern section of the southern transect is about °C, similar to the eastern margin of the western section of the ophiolite within the northern transect. This suggests that the upper sequence along the southern transect was transported from the west after peak metamorphism along the NW-SE trending thrust fault. Amphibole porphyroclasts record pervasive prograde but no retrograde zoning, probably resulting from rapid exhumation after peak metamorphism. The metamorphism observed in the Poroshiri ophiolite is vastly different from ordinary regional metamorphism.

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Section: D0mentioning

confidence: 98%

“…1 , 1951Fig. 1 , 1955, 1961Hashimoto 19753 19792 1970Grapes et al 197719781983, 1989, 1989;Miyashita et al, 1994;, 1994;, 2007, 2006;, 2006N-MORB N-MORB , 2007Jolivet and Miyashita 1985 Hidaka Shear Zone Miyashita (1983) and Arai and Miyashita (1994).…”

Section: Kmmentioning

confidence: 99%

Geology and metamorphism in the northern Poroshiri ophiolite, Hokkaido, Japan

Tanaka

Kizaki²,

Miyashita

2012

Jour. Geol. Soc. Japan

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“…The Poroshiri ophiolite (age unknown), located west of the HMB (Figure 1c), comprises mafic to ultra‐mafic metacumulate, dunite, harzburgite, metagabbro and amphibolite (Arai et al, 1995). Metabasaltic rocks display normal MORB characteristics and are assumed to have formed at an ultrafast‐spreading ridge (Miyashita et al, 2007). The boundary between the HMB and the Poroshiri ophiolite is a major thrust fault, the Hidaka Main Thrust.…”

Section: Geological Backgroundmentioning

confidence: 99%

Repeated metamorphism in the pelitic granulites of the Hidaka metamorphic belt, Hokkaido, Japan: Implications for the formation of the present‐day trench‐arc‐basin system in NE Asia

Zhang

Dong

et al. 2022

Journal Metamorphic Geology

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The timing and mechanism of the tectonic transition from an active continental margin to a trench‐arc‐basin system in NE Asia are debated. In this study, we report the pressure–temperature–time (P–T–t) path of this transition based on petrographic observations, phase‐equilibrium modelling, and U–Pb ages of zircon and rutile from pelitic granulites in the Hidaka metamorphic belt (Hokkaido, Japan). The granulites contain an early phase mineral assemblage of staurolite + sillimanite + biotite + plagioclase + quartz + rutile/ilmenite, a peak phase granulite assemblage of garnet + biotite + cordierite + plagioclase + quartz + rutile/ilmenite and a symplectic intergrowth of spinel + cordierite ± sillimanite within garnet porphyroblasts. Phase‐equilibrium modelling indicates two phases of metamorphism with P–T conditions, respectively, of ~6 kbar/620–670°C and ~6 kbar/850°C. A clockwise P–T path was thus reconstructed for the granulites, showing a near‐isobaric temperature increase to the peak conditions and a post‐peak cooling. U–Pb dating of zircon and rutile in the granulites yielded two groupings of metamorphic ages at c. 37 Ma and 19 Ma, related to early phase amphibolite facies and late phase granulite facies metamorphism, respectively. The age of magmatism from the previous work at the NE Asian continental margin overlaps with these metamorphic ages, and the two phases of metamorphism in the pelitic granulites is attributed to discrete episodes of supra‐subduction‐zone magmatism (late Eocene, c. 37 Ma) and back‐arc extension (early Miocene, 24–19 Ma). Consequently, we suggest that the Hidaka metamorphic belt has undergone two phases of metamorphism, which represent two pulsed and separated thermal events. Moreover, we relate the granulites facies metamorphism to the underplating of mafic magma and lithospheric thinning during the opening of the Japan Sea at 24–19 Ma, which is attributed to slab rollback and trench retreat processes in NE Asia.

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“…The geochemistry of the basalt and mineralogy of cumulate and peridotite all suggest that the ophiolite originated from normal oceanic crust formed at an oceanic spreading ridge (Miyashita, Adachi, Tanaka, Nakagawa, & Kimura, 2007;Miyashita et al, 1994). Zircon U-Pb dating of plagiogranite yields an age of 96.7 Ma ±2.6 Ma (Kizaki, 2000) contemporaneous with pelagic sedimentation in the Late Cretaceous unit of the Idonnappu terrane.…”

Section: Poroshiri Ophiolitementioning

confidence: 99%

The basement geology of Japan from A to Z

et al. 2020

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The Precambrian and lower Paleozoic units of the Japanese basement such as the Hida Oki and South Kitakami terranes have geological affinities with the eastern Asia continent and particularly strong correlation with units of the South China block. There are also indications from units such as the Hitachi metamorphics of the Abukuma terrane and blocks in the Maizuru terrane that some material may have been derived from the North China block. In addition to magmatism, the Japanese region has seen substantial growth due to tectonic accretion. The accreted units dominantly consist of mudstone and sandstone derived from the continental margin with lesser amounts of basaltic rocks associated with siliceous deep ocean sediments and local limestone. Two main phases of accretionary activity and related metamorphism are recorded in the Jurassic Mino-Tanba-Ashio, Chichibu, and North Kitakami terranes and in the Cretaceous to Neogene Shimanto and Sanbagawa terranes. Other accreted material includes ophiolitic sequences, e.g. the Yakuno ophiolite of the Maizuru terrane, the Oeyama ophiolite of the Sangun terrane, and the Hayachine-Miyamori ophiolite of the South Kitakami terrane, and limestone-capped ocean plateaus such as the Akiyoshi terrane. The ophiolitic units are likely derived from arc and back-arc basin settings. There has been no continental collision in Japan, meaning the oceanic subduction record is more complete than in convergent orogens seen in intracontinental settings making this a good place to study the geological record of accretion. Hokkaido lacks most of the Paleozoic history recognized in Honshu, Shikoku, Kyushu, and the Ryukyu Islands to the south and its geology reflects the Cenozoic development of two convergent domains with volcanic arcs, their approach, and eventual collision. The Hidaka terrane reveals a cross section through a volcanic arc and the main accretionary complex of the convergent system is represented by the Sorachi-Yezo terrane.

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Genesis of the Poroshiri ophiolite, Hokkaido, Japan; Inference from geochemical evidence

Cited by 8 publications

References 27 publications

Geology and metamorphism in the northern Poroshiri ophiolite, Hokkaido, Japan

Geology and metamorphism in the northern Poroshiri ophiolite, Hokkaido, Japan

Repeated metamorphism in the pelitic granulites of the Hidaka metamorphic belt, Hokkaido, Japan: Implications for the formation of the present‐day trench‐arc‐basin system in NE Asia

The basement geology of Japan from A to Z

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