K-Ar ages of detrital K-feldspars and muscovites from the Shimanto Supergroup in east Kyushu and west Shikoku, Southewest Japan.

易司, 寺岡; 賢, 柴田; 公男, 奥村; 茂, 内海

doi:10.5575/geosoc.100.477

Cited by 10 publications

(11 citation statements)

References 4 publications

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“…The Cretaceous belt is oversimplified. Stratigraphic age gaps of the northern Shimanto Belt indicate the existence of two diachronous subbelts [ Teraoka et al , ], the Saiki and Kamae Subbelts, from north to south. According to these authors, the Foliated Morotsuka (named Kamae Subbelt there) is the youngest subbelt, with limited age overlapping with the more sandstone‐rich, overlying Coherent Morotsuka (named Saiki Subbelts there), so that the two subbelts cannot originate from a single lithostratigraphic section and have to be diachronously accreted.…”

Section: Reconstruction Of Shimanto Belt Evolutionmentioning

confidence: 99%

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Long-term evolution of an accretionary prism: The case study of the Shimanto Belt, Kyushu, Japan

Raimbourg

Augier

Famin³

et al. 2014

Tectonics

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The Shimanto Belt in SW Japan is commonly described as a paleo-accretionary prism, whose structure is explained by continuous accretion like in modern accretionary prisms such as Nankai. We carried out a structural study of the Cretaceous to Miocene part of the Shimanto Belt on Kyushu to test this hypothesis of continuous accretion. Most deformation structures observed on the field are top-to-the-SE thrusts, fitting well the scheme of accretionary wedge growth by frontal accretion or underplating. In particular, the tectonic mélange at the top of the Hyuga Group records a penetrative deformation reflecting burial within the subduction channel. In contrast, we documented two stages of extension that require modifying the traditional model of the Belt as a "simple" giant accretionary wedge. The first one, in the early Middle Eocene, is mostly ductile and localized in the foliated bases of the Morotsuka and Kitagawa Groups. The second one, postdating the Middle Miocene, is a brittle deformation spread over the whole belt on Kyushu. Integrating these new tectonic features to existing data, we propose 2-D reconstructions of the belt evolution, leading to the following conclusions: (1) Erosion and extension of the margin in the early Middle Eocene resulted from the subduction of a trench-parallel ridge. (2) The Late Eocene to Early Miocene evolution is characterized by rapid growth of the prism, followed by a Middle Miocene stage where large displacements occurred along low-angle out-of-sequence thrusts such as the Nobeoka Tectonic Line. (3) From middle Miocene, the strain regime was extensional.

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Section: Reconstruction Of Shimanto Belt Evolutionmentioning

confidence: 99%

“…The Cretaceous belt is oversimplified. Stratigraphic age gaps of the northern Shimanto Belt indicate the existence of two diachronous subbelts[Teraoka et al, 1994], the Saiki…”

mentioning

confidence: 99%

Long-term evolution of an accretionary prism: The case study of the Shimanto Belt, Kyushu, Japan

Raimbourg

Augier

Famin³

et al. 2014

Tectonics

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“…The distribution of reduced-and oxidised-type granitoids is based on Sato et al (1992) for the Japanese Islands, Romanovsky et al (1996) for Sikhote-Alin and Jin et al (2001) for the Korean Peninsula. Accretionary complexes, high-P/T metamorphic rocks are from Geological Survey of Japan (1992), Kimura (1994) and Teraoka & Okumura (2003). Iron and base metals are excluded for simplicity because of their occurrences in both type granitoid provinces.…”

Section: Figurementioning

confidence: 99%

“…11) were changed to a zone of extensive felsic magmatism in Cretaceous times (Figs 1 & 4). Sato (2000Sato ( , 2003 with reference to Sato et al (1992), Krasnyi et al (1996) and Teraoka & Okumura (2003). Uyeda & Miyashiro 1974;Jahn 1974;Maruyama et al 1997), although the real cause is not well understood.…”

Section: Reorganisation Of Accretionary Complexmentioning

confidence: 99%

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

Sato¹,

Kovalenko²,

Romanovsky

et al. 2004

Earth and Environmental Science Transactions of the Royal Socie

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Felsic magmatism has occurred over a large region of East Asia since Jurassic times and has provided important mineral resources such as tin, tungsten, base metals and gold. The circum-Japan Sea region preserves various geological records of active continental margins, including Jurassic to Early Tertiary magmatic arcs and subduction zones and pre-Jurassic continental basements, which were separated by the opening of the Japan Sea during the Miocene. The felsic magmatism in this region shows a wide variation in terms of redox state and related mineralisation, encompassing east–west contrasts around the Pacific Ocean. A review of granitoids and associated ore deposits in this region indicates that the character of the crust, sedimentary versus igneous, is an essential factor to control the redox state, and a tectonic setting may be an additional factor in some cases.The reduced-type granitoids, characterised by tin mineralisation, were generated in carbonbearing sedimentary crust which was composed mainly of accretionary complex material and not influenced by previous magmatism. Involvement of sedimentary materials is corroborated by oxygen, sulphur and strontium isotope data. The oxidised-type granitoids, characterised by gold or molybdenum mineralisation, were generated in igneous crust which was depleted in reducing agents as a result of previous magmatism. Granitoid magmatism in a given area tends to become more oxidised with time.Jurassic accretionary complexes in East Asia are thought to have been largely displaced from the original place of accretion and stacked up against the northeastern margin in the Khingan and Sikhote–Alin Mountains. This region, dominated by sedimentary crust, was subsequently subjected to Cretaceous felsic magmatism and converted to a large province of reduced-type granitoids and tin–tungsten mineralisation. Diverse geodynamic processes, including the change of the arc-trench system, the creation and collapse of the back-arc basin and the collision of continents, may have prepared many favourable sites for the generation of reduced-type granitoids in northeast Asia. These processes may have resulted in a remarkable contrast with the Pacific margin of North America, where repeated arc magmatism during the Mesozoic formed granitoid batholiths of the oxidised-type.The granitoid types may also be controlled by the tectonic setting and mode of magma emplacement. In the northern Kitakami area of Northeast Japan, Early Cretaceous episodic magmatism occurred in a Jurassic accretionary complex, and formed the oxidised-type granitoids accompanied by submarine bimodal volcanism associated with kuroko mineralisation. Granitoids of fissure-filling type emplaced under extensional environments may be oxidised, irrespective of basement geology, because of insignificant crustal input.

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“…This paper deals with the Cretaceous formations of the Shimanto Supergroup in the Hokusatsu District, southern Kyushu (Fig. 1b, [5]). The Hokusatsu District is situated at the junction of two island arc segments, the Southwest Japan Arc and the Ryukyu Arc [e.g.…”

Section: Introductionmentioning

confidence: 99%

South-Vergent Imbricate Fan in the Ikenodan Formation of the Shimanto Supergroup, Southern Kyushu, Japan

Doi

Yamamoto²,

Tominaga³

et al. 2013

TOGEOJ

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Abstract:The Noda area in the Hokusatsu District, southwest Kyushu is underlain by the Imanokoba, the Ikenodan and the Ogakura Formations of the Cretaceous Shimanto Supergroup. The Imanokoba Formation comprises beds of sandstone and mudstone. The beds generally trend NE-SW and dip in a moderate to steep angles to the east or west. The Ikenodan Formation comprises beds of sandstone, mudstone, siliceous mudstone and chert and basaltic lavas. The beds generally strike between NE and NW, and dip toward the west in moderate to high angles with a westerly way-up. The chert and basaltic lava beds appear in a left-stepping en echelon arrangement. The contact between the Imanokoba and the Ikenodan Formations is in a N-S trending fault known as the Noda Fault. The Ogakura Formation is composed of alternating beds of sandstone and mudstone. The beds generally strike between NE and NNE and dip toward the west in moderate to high angles with westerly way-up. The contact relationship between the Ikenodan and the Ogakura Formations is not distinct. The westward disappearance of the basaltic lava marks the western limit of the Ikenodan Formation. The en echelon array in the Ikenodan Formation is interpreted as an imbricate fan with the Noda Fault on its bottom as a décollement and is called "the Ikenodan imbricate fan". The Ikenodan imbricate fan is considered to have been formed in an accretionary complex developed in a northbound subduction zone. The primary attitude of the Ikenodan imbricate fan was probably south-vergent then turned over with its west side down. It was previously reported that the strata of the Shimanto Supergroup in the Hokusatsu area form a regional bending structure called the "the Hokustasu Bend". The Noda area is situated in a hinge zone of the Hokusatsu Bend, although the formations in the Noda area have not been involved in the bending structure. The Ikenodan Formation and the Noda Fault presumably extend to the north without bending, otherwise the bending structure occurs anywhere outside the Noda area. In either case, the Hokusatsu Bend is not present as interpreted in the previous studies.

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K-Ar ages of detrital K-feldspars and muscovites from the Shimanto Supergroup in east Kyushu and west Shikoku, Southewest Japan.

Cited by 10 publications

References 4 publications

Long-term evolution of an accretionary prism: The case study of the Shimanto Belt, Kyushu, Japan

Long-term evolution of an accretionary prism: The case study of the Shimanto Belt, Kyushu, Japan

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

South-Vergent Imbricate Fan in the Ikenodan Formation of the Shimanto Supergroup, Southern Kyushu, Japan

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