Granitic rocks

Nakajima, Takahito; Takahashi, Masaki; Imaoka, Teruyoshi; Shimura, Toshiaki

doi:10.1144/goj.10

Cited by 22 publications

(26 citation statements)

References 122 publications

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“…115–65 Ma are now widely distributed in SW Japan and SE Korean Peninsula (e.g. Chough & Sohn, ; Imaoka et al, ; Kim et al, ; Nakajima, Takahashi, Imaoka, & Shimura, ; Sato, Matsuura, & Yamamoto, ; Yamada, Takizawa, Tanase, & Kawada, ). In addition, Shunori, Takeuchi, and Yamamoto () conducted detrital zircon U–Pb dating on the rocks of the Cretaceous forearc basin (Yuasa–Aridagawa basin) on the Kii Peninsula, and they reported that the Cretaceous granitic rocks (Ryoke granitic rocks) were providing material to the forearc basin shortly after their formation.…”

Section: Discussionmentioning

confidence: 99%

Lithological, structural, and chronological relationships between the Sanbagawa Metamorphic Complex and the Cretaceous Shimanto Accretionary Complex on the central Kii Peninsula, SW Japan

et al. 2019

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It is essential to clarify the lithological, structural, and chronological relationships between the Sanbagawa Metamorphic Complex (MC) and the Cretaceous Shimanto Accretionary Complex (AC) for understanding the tectonic evolution of SW Japan. To this end, we carried out a detailed field survey of the Sanbagawa MC and the Cretaceous Shimanto AC on the central Kii Peninsula, where they are in direct contact with each other. We also conducted U-Pb dating of detrital zircons from these complexes. The field survey showed that the boundary between the Iro Complex of the Sanbagawa MC and the Mugitani Complex of the Shimanto AC, Narai Fault, shows a sinistral sense of shear with a reverse dip-slip component, and there are significant differences in the strain intensity and the degree of recrystallization between the two complexes across this fault. Detrital zircon U-Pb dating indicates that the Iro Complex in the hanging wall of the Narai Fault shows a significantly younger maximum depositional age than the Mugitani Complex in the footwall of the fault, and an apparently large gap in the MDA of ca. 35 Myr exists across this fault. This large age gap across the Narai Fault suggests that this fault is an essential tectonic boundary fault within the Cretaceous accretionary-metamorphic complexes on the Kii Peninsula, and is considered to be an out-of-sequence thrust. In addition, a similar shear direction and a large age gap have been identified across the Ui Thrust, which marks the boundary between the Kouyasan and Hidakagawa belts of the Cretaceous Shimanto AC. The Cretaceous accretionary-metamorphic complexes record the large-scale tectonic juxtapositions of complexes, and these juxtaposed structures had been caused by sinistral-reverse movements on the tectonic boundary faults such as the Narai Fault and the Ui Thrust. K E Y W O R D S accretionary complex, Cretaceous, detrital zircon, Kii Peninsula, metamorphic complex,

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Section: Discussionmentioning

confidence: 99%

Lithological, structural, and chronological relationships between the Sanbagawa Metamorphic Complex and the Cretaceous Shimanto Accretionary Complex on the central Kii Peninsula, SW Japan

et al. 2019

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“…For example, contraction, basin inversion, and uplift throughout the NE Japan arc and back‐arc in the Plio‐Pleistocene accompanied rapid, orthogonal subduction (Yoshida et al , ). More‐localized contraction and uplift were caused by Neogene collisions between the NE Japan arc and Kuril fore‐arc and Honshu and Izu‐Bonin arcs in the Hidaka belt of central Hokkaido and Izu Collision Zone of central Honshu, respectively (Nakajima et al , ; Tatsumi et al , ). Seismic and aseismic ridges and seamount chains were also subducted at various times, as exemplified by the Izanagi spreading ridge during the Eocene (Seton et al , ) and Kyushu‐Palau Ridge remnant arc during the Neogene (Mahony et al , ).…”

Section: Regional Factors Influencing Porphyry Cu Potentialmentioning

confidence: 99%

“…This assessment of porphyry Cu potential focuses on the Cretaceous and Paleogene volcano‐plutonic arcs, which were generated while proto‐Japan was still attached to the east Eurasian margin and abutted the Korean peninsula and crustal fragments currently submerged beneath the western half of the Sea of Japan or East Sea (Tamaki, ). Approximately 95% of the intrusive rocks exposed in Japan and the Gyeongsang basin of SE Korea are of this age and they occupy >25% of the land area (Jin et al , ; Nakajima et al , ; Fig. ).…”

Section: Introductionmentioning

confidence: 99%

Why No Porphyry Copper Deposits in Japan and South Korea?

Sillitoe¹

2018

Resource Geology

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This analysis concludes that there is little realistic likelihood of discovering large, high‐grade porphyry Cu deposits in Japan and South Korea because of an unusual combination of geological factors. First, weak inter‐plate coupling, trench retreat, and extension – a tectonic regime unfavorable for porphyry Cu formation – appears to have characterized the convergent margin during much of Cretaceous through Neogene time. Second, Cretaceous through Quaternary magmatism involved widespread ash‐flow caldera development, a volcanic style that suppresses porphyry Cu formation because the all‐important Cu‐bearing magmatic fluids – if present – would be explosively discharged during silicic ignimbrite eruption and lost to the atmosphere. Third, due to the trench retreat, crustal profiles beneath Japan are dominated by accretionary complexes containing chemically reduced lithologies, which decrease the redox state of subduction‐related magmas during their ascent. The most reduced intrusions belong to the ilmenite‐series, which may lock up chalcophile elements at depth and produce magmatic fluids that are incapable of transporting the Cu required for significant porphyry deposit formation. Fourth, many of the caldera‐related magmatic rocks, including the principal intrusions, are not only derived by partial melting of reduced crust but are commonly also highly fractionated; hence, any associated mineralization tends to be Mo ± W‐rich rather than Cu dominated. Fifth, intrusive rocks with high Sr/Y, typical of hydrous magmas responsible for porphyry Cu belts worldwide, appear to be present only locally. Sixth, two important magmatic and metallogenic tracts in Japan, the Kuroko‐bearing Green Tuff belt and Kitami low‐sulfidation epithermal Au region, are characterized by bimodal magmatism, which worldwide is compositionally unsuited to porphyry Cu generation. Seventh, the Pliocene‐Quaternary andesitic–dacitic volcanoes that could be the surface expressions of porphyry Cu systems are mostly too shallowly eroded to reveal underlying deposits should they exist. Consequently, few magmatic suites in Japan and South Korea provide propitious environments for porphyry Cu exploration, with the last hope believed to lie at depth below late Miocene–Pliocene advanced argillic lithocaps, several of which contain relatively minor high‐sulfidation epithermal Au mineralization. However, even there, the reduced crust may have militated against effective Cu transport into the porphyry environment. The magmatic and metallogenic factors that downgrade the porphyry Cu potential of Japan and South Korea are believed to be equally applicable to other subduction‐related magmatic arc segments worldwide.

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“…These granitoids intrude mainly in the Paleozoic and Mesozoic sedimentary rocks which accreted to the Pacific margin of the Eurasian continent during the Mesozoic (Wakita, ). They form a part of the magmatic arc, related to the subduction of the Kula and Pacific plates beneath the Eurasian continent (Nakajima et al, ). These granitoids are classified into oxidized and reduced ones, and called the magnetite‐series and ilmenite‐series, respectively (Ishihara, ).…”

Section: Cretaceous To Paleogene Granitic Rocks In the Southwestern Jmentioning

confidence: 99%

“…All the granitoids of the Sanin and Sanyo belts belong to the I type, whereas parts of the granitoids of the Ryoke belt are classified into the S type in addition to I type (Ishihara and Chappell, ). The granitoids of the Ryoke belt are differentiated from those of the Sanyo belt by their older intrusive ages, batholitic occurrence, deeper intrusive levels and less fractionated geochemistry (Ishihara and Chappell, ), and such characteristics for the Ryoke belt are ascribed to deeper erosion levels of the belt (Nakajima et al, ).…”

Section: Cretaceous To Paleogene Granitic Rocks In the Southwestern Jmentioning

confidence: 99%

Differential Fractionation of Rare Earth Elements in Oxidized and Reduced Granitic Rocks: Implication for Heavy Rare Earth Enriched Ion Adsorption Mineralization

et al. 2016

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Ion adsorption rare earth element (REE) deposits in southern China are the exclusive source of heavy REEs (HREEs) in the world, and this HREE‐enriched character of the deposits is inherited from the REE compositions of the underlying granitic rocks. Such HREE‐enriched rocks form from heavy fractionation of reduced granitic magmas. We explore why reduced granitic magmas are enriched in HREEs during the fractionation, based on the REE geochemistry of granitic rocks and abundance of REEs in their constituent minerals in the southwestern Japan arc of Cretaceous to Paleogene age. The compilation of the whole rock geochemistry and REE compositions of the granitic rocks of the Sanin (oxidized), Sanyo (reduced) and Ryoke (reduced) belts in the southwestern Japan arc indicates that: (i) light REEs (LREEs) decease with fractionation of the granitoids in the Sanin belt but this trend is not clear in the granitoids in the Sanyo belt and LREEs rather increase in the Ryoke granitoids; (ii) Eu decreases with fractionation in all the belts; and (iii) HREEs slightly, but steadily decrease in the Sanin belt but enrich significantly in the Sanyo and Ryoke belts with fractionation. Analytical results of REE concentrations by scanning electron microscope with energy dispersive X‐ray spectroscope and laser ablation‐inductively coupled plasma mass spectrometer in the constituent minerals in a granodiorite sample from the Sanin belt show a moderate concentration of REEs in hornblende (577 ppm) in addition to high concentrations in allanite (~20 %), britholite (~30 %), primary titanite (8922 ppm), apatite (4062 ppm), and zircon (1693 ppm). Because primary titanite and allanite are commonly present in the oxidized granitoids but not in the reduced ones, the REE depletion in the fractionated, oxidized granites is attributed to the crystallization of these minerals. In contrast, scarcity of these minerals in the reduced granitoids enriches REEs, in particular HREEs in the fractionated magmas, which finally precipitate REEs in the granites and pegmatites. Both positive, but different correlation ratios between the Nb and Dy concentrations in the granitoids of the Sanin and Sanyo‐Ryoke belts suggest that columbite–pyrochlore‐group and fergusonite‐group minerals are the major HREE host in the oxidized and reduced granites, respectively.

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Granitic rocks

Cited by 22 publications

References 122 publications

Lithological, structural, and chronological relationships between the Sanbagawa Metamorphic Complex and the Cretaceous Shimanto Accretionary Complex on the central Kii Peninsula, SW Japan

Lithological, structural, and chronological relationships between the Sanbagawa Metamorphic Complex and the Cretaceous Shimanto Accretionary Complex on the central Kii Peninsula, SW Japan

Why No Porphyry Copper Deposits in Japan and South Korea?

Differential Fractionation of Rare Earth Elements in Oxidized and Reduced Granitic Rocks: Implication for Heavy Rare Earth Enriched Ion Adsorption Mineralization

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