Intra-oceanic island arc origin for Iratsu eclogites of the Sanbagawa belt, central Shikoku, southwest Japan

Utsunomiya, Atsushi; Jahn, Bor‐ming; Okamoto, K.; Ota, Tsutomu; Shinjoe, Hironao

doi:10.1016/j.chemgeo.2010.11.001

Cited by 38 publications

(34 citation statements)

References 44 publications

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“…This indicates the presence of landmass above sea-level, because andesitic volcaniclastic gravels were rounded by erosion during the transportation through river systems. This is also true in the 3.5 Ga Pilbara craton, Western Australia, where a huge oceanic plateau similar to the modern Ontong-Java plateau in the western Pacific (formed during Cretaceous time, Ishikawa et al, 2011;Utsunomiya et al, 2011) accreted to be preserved as fragments in the 3.5 Ga accretionary complex (Kitajima et al, 2008). Within the huge fragment, an excellent unconformity is present with basal conglomerate layers having rocks derived from on-land above sea-level in the 3.5 Ga Earth.…”

Section: Archean Earth and Thickness Of Oceanmentioning

confidence: 80%

The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

Maruyama

Ikoma

Genda

et al. 2013

Geoscience Frontiers

126

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a b s t r a c tOur blue planet Earth has long been regarded to carry full of nutrients for hosting life since the birth of the planet. Here we speculate the processes that led to the birth of early life on Earth and its aftermath, finally leading to the evolution of metazoans. We evaluate: (1) the source of nutrients, (2) the chemistry of primordial ocean, (3) the initial mass of ocean, and (4) the size of planet. Among the life-building nutrients, phosphorus and potassium play a key role. Only three types of rocks can serve as an adequate source of nutrients: (a) continent-forming TTG (granite), enabling the evolution of primitive life to metazoans; (b) primordial continents carrying anorthosite with KREEP (Potassium, Rare Earth Elements, and Phosphorus) basalts, which is a key to bear life; (c) carbonatite magma, enriched in radiogenic elements such as U and Th, which can cause mutation to speed up evolution and promote the birth of new species in continental rift settings. The second important factor is ocean chemistry. The primordial ocean was extremely acidic (pH ¼ 1e2) and enriched in halogens (Cl, F and others), S, N and metallic elements (Cd, Cu, Zn, and others), inhibiting the birth of life. Plate tectonics cleaned up these elements which interfered with RNA. Blue ocean finally appeared in the Phanerozoic with pH ¼ 7 through extensive interaction with surface continental crust by weathering, erosion and transportation into ocean. The initial ocean mass was also important. The birth of life and aftermath of evolution was possible in the habitable zone with 3e5 km deep ocean which was able to supply sufficient nutrients. Without a huge landmass, nutrients cannot be supplied into the ocean only by ridge-hydrothermal circulation in the Hadean. Finally, the size of the planet plays a crucial role. Cooling of massive planets is less efficient than smaller ones, so that return-flow of seawater into mantle does not occur until central stars finish their main sequence. Due to the suitable size of Earth, the dawn of Phanerozoic witnessed the initiation of return-flow of seawater into the mantle, leading to the emergence of huge landmass above sea-level, and the distribution of nutrients on a global scale. Oxygen pump also played a critical role to keep high-PO 2 in atmosphere since then, leading to the emergence of ozone layer and enabling animals and plants to invade the land.To satisfy the tight conditions to make the Earth habitable, the formation mechanism of primordial Earth is an important factor. At first, a 'dry Earth' must be made through giant impact, followed by magma ocean to float nutrient-enriched primordial continents (anorthosite þ KREEP). Late bombardment from asteroid belt supplied water to make 3e5 km thick ocean, and not from icy meteorites from Geoscience Frontiers 4 (2013) 141e165Kuiper belt beyond cool Jupiter. It was essential to meet the above conditions that enabled the Earth as a habitable planet with evolved life forms. The tight constraints that we evaluate for birth and evolution of l...

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Section: Archean Earth and Thickness Of Oceanmentioning

confidence: 80%

The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

Maruyama

Ikoma

Genda

et al. 2013

Geoscience Frontiers

126

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“…Whole‐rock major element compositions of quartz eclogites and mafic clots from the Gongen area and other lithologies of the Sanbagawa metamorphic belt. Data sources are as follows: Quartz eclogite and mafic clot (Miyamoto et al, ; Utsunomiya et al, ; Yokoyama, unpublished data; this study), metabasalt and metagabbro (Aoya et al, ; Banno, ; Endo et al, ; Ernst, Seki, Onuki, & Gilbert, ; Goto & Banno, ; Nozaki et al, ; Okamoto et al, ; Utsunomiya et al, ; Weller, Wallis, Aoya, & Nagaya, ; Enami, Iwata, and Yokoyama, unpublished data), metasediments (Aoya et al, ; Banno, ; Ernst et al, ; Fujiwara, Yamamoto, & Mimura, ; Goto et al, ; Kiminami, ; Kiminami & Ishihama, ; Kiminami & Toda, ; Utsunomiya et al, ; Zaw Win Ko et al, ; Enami, unpublished data) of the Sanbagawa metamorphic belt. Mfc, mafic clot; Qpd, quartz‐poor domain; Qrd, quartz‐rich domain in quartz eclogite (GE1501a) shown in Figure .…”

Section: Chemical Compositions Of Quartz Eclogitementioning

confidence: 94%

“…This body records equilibrium P–T conditions of 2.9–3.8 GPa and 700–810 °C and represents the deepest part of the Sanbagawa subduction zone (Enami et al, ; Mizukami & Wallis, ). The bodies of Tonaru, Seba, and the eastern half of Iratsu (Eastern Iratsu body) are mostly metamorphosed layered gabbros (Banno et al, ), and the western half of the Iratsu body (Western Iratsu body) is a combination of metamorphosed oceanic basalt, pelagic sediments, chert, and limestone (Endo, ; Kugimiya & Takasu, ; Ota, Terabayashi, & Katayama, ; Takasu, ; Utsunomiya et al, ). Aoya (), Miyagi and Takasu (), and Ota et al () reported P–T conditions of 1.2–2.4 GPa and 610–640 °C, 1.4–2.5 GPa and 500–800 °C, and 1.5–2.5 GPa and 700–730 °C for the peak metamorphism of eclogites in the Seba, Iratsu, and Tonaru bodies, respectively.…”

Section: Geological Settingmentioning

confidence: 99%

“…Whole‐rock minor element compositions of quartz eclogites and mafic clots from the Gongen area and other lithologies of Sanbagawa metamorphic belt in (a) Ti/50‐Zr‐Sr/2 and (b) V–Ba diagrams. Data sources are as follows: Quartz eclogite and mafic clot (Miyamoto, Enami, Tsuboi, & Yokoyama, ; Utsunomiya, Jahn, Okamoto, Ota, & Shinjoe, ; this study), metabasalt and metagabbro (Aoya, Tsuboi, & Wallis, ; Endo, Wallis, Tsuboi, Aoya, & Uehara, ; Nozaki, Nakamura, Awaji, & Kato, ; Okamoto, Maruyama, & Isozaki, ; Uno et al, ; Utsunomiya et al, ; Enami, unpublished data), metasediments (Aoya et al, ; Goto, Higashino, & Sakai, ; Kiminami, ; Kiminami & Ishihama, ; Kiminami & Toda, ; Utsunomiya et al, ; Enami, unpublished data). Mfc, mafic clot; Qpd, quartz‐poor domain; Qrd, quartz‐rich domain in quartz eclogite (GE1501a) shown in Figure .…”

Section: Chemical Compositions Of Quartz Eclogitementioning

confidence: 99%

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Coexisting different types of zoned garnet in kyanite‐quartz eclogites from the Sanbagawa metamorphic belt: Evidence of deformation‐induced lithological mixing during prograde metamorphism

et al. 2018

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Garnet grains in Sanbagawa quartz eclogites from the Besshi region, central Shikoku commonly show a zoning pattern consisting of core and mantle/rim that formed during two prograde stages of eclogite and subsequent epidote–amphibolite facies metamorphism, respectively. Garnet grains in the quartz eclogites are grouped into four types (I, II, III, and IV) according to the compositional trends of their cores. Type I garnet is most common and sometimes coexists with other types of garnet in a thin section. Type I core formed with epidote and kyanite during the prograde eclogite facies stage. The inner cores of types II and III crystallized within different whole‐rock compositions of epidote‐free and kyanite‐bearing eclogite and epidote‐ and kyanite‐free eclogite at the earlier prograde stage, respectively. The inner core of type IV probably formed during the pre‐eclogite facies stage. The inner cores of types II, III, and IV, which formed under different P–T conditions of prograde metamorphism and/or whole‐rock compositions, were juxtaposed with the core of type I, probably due to tectonic mixing of rocks at various points during the prograde eclogite facies stage. After these processes, they have shared the following same growth history: (i) successive crystal growth during the later stage of prograde eclogite facies metamorphism that formed the margin of the type I core and the outer cores of types II, III, and IV; (ii) partial resorption of the core during exhumation and hydration stage; and (iii) subsequent formation of mantle zones during prograde metamorphism of the epidote–amphibolite facies. The prograde metamorphic reactions may not have progressed under an isochemical condition in some Sanbagawa metamorphic rocks, at least at the hand specimen scale. This interpretation suggests that, in some cases, material interaction promoted by mechanical mixing and fluid‐assisted diffusive mass transfer probably influences mineral reactions and paragenesis of high‐pressure metamorphic rocks.

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“…Contour currents have turned east on the east side of the Izu Bonin Ridge. The volcanic activities around, sediment gravity flow area and a large slope movement may be important causes of relative sediment transport and accumulation (Utsunomiya et al, 2011). As the affect of terrain, the Antarctic Bottom Water (AABW) within the Shikoku Basin rotates along counterclockwise.…”

Section: Effect Of Ocean Currents On Sediment Provenancementioning

confidence: 99%

Geochemistry and provenances of core sediments from the Shikoku Basin

Han

Liu

et al. 2016

Geological Journal

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Provenances of pelagic sediments are a less well‐known and key problem of sedimentation in the deep sea. Two sediment cores from the south and middle Shikoku Basin are selected for grain size analysis and element geochemical analysis in this paper. Grain size analysis for the studied cores shows that the grain sizes become coarser upwards gradually, especially for subsurface sediments. It probably reveals the enhancement of terrigenous clastic material. Rare elements analysis reveals that two cores are enriched in Ba and Th. However, the other elements are more or less the same as those of the North American Shales (NAS). Through the NASC‐normalized REE distribution, curves are nearly aclinic, and there are no Ce and Eu anomalies. The geochemical characteristics of elements indicate that the sediments in the Shikoku Basin should mainly be regarded as hemipelagic and pelagic sediments. The comparison of samples from the Nankai Trough, Kyushu Ridge and Izu Island Arc and the analysis of DSDP and ODP cores jointly show that the sediments of the core SG1‐2 have an apparent ‘affinity’ with the Nankai Trough. The core SG1‐1 is influenced by the submarine volcanic activities, having a relatively complex provenance, and is possibly derived from the spreading centre of the Kyushu Ridge and the central Shikoku Basin. Copyright © 2016 John Wiley & Sons, Ltd.

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Intra-oceanic island arc origin for Iratsu eclogites of the Sanbagawa belt, central Shikoku, southwest Japan

Cited by 38 publications

References 44 publications

The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

Coexisting different types of zoned garnet in kyanite‐quartz eclogites from the Sanbagawa metamorphic belt: Evidence of deformation‐induced lithological mixing during prograde metamorphism

Geochemistry and provenances of core sediments from the Shikoku Basin

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