Volcanostratigraphy and geologic structure of Cretaceous Abu Group, and finding of Sasanami cauldron, central part of Yamaguchi Prefecture, Southwest Japan.

寿之, 井川; 照喜, 今岡

doi:10.5575/geosoc.107.243

Cited by 12 publications

(3 citation statements)

References 12 publications

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“…17, Table 1). The historically famed silver deposits mined during the early Edo period at Ichinosaka, Yamaguchi Prefecture, are thought to be related to felsic dikes intruded along a cauldron wall of the Sasanami cauldron (Ikawa and Imaoka, 2001). Galenas from sphalerite-galena-rhodochrosite veins yield -5.0 and -5.5 permil δ 34 S (no.…”

Section: Sanyo-naegi Beltmentioning

confidence: 99%

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Paired Sulfur Isotopic Belts: Late Cretaceous-Paleogene Ore Deposits of Southwest Japan.

舜三

昭

2002

Bull. Geol. Surv. Japan

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Abstract:Sulfides from late Cretaceous-Paleogene ore deposits of the Inner Zone of Southwest Japan were analyzed for 34 S/ 32 S ratios (δ 34 SCDT values) on 5 samples from the Ryoke Belt, 18 from the Sanyo-Naegi Belt, 15 from the Uetsu-Kanto District and 47 samples from the Sanin-Shirakawa Belt. Together with the published data, the average δ 34 S values are calculated for individual deposits of the whole region; 109 localities for the ilmenite-series granitic belt and 56 localities for the magnetiteseries granitic belt.The sulfur isotopic ratios vary regionally rather than with sulfide species or types and commodities of the ore deposits. The δ 34 S values are generally negative in the fore-arc, ilmenite-series belt, and positive in the back-arc, magnetite-series belt. This regional variation is considered to reflect the ilmenite-/magnetite-series pairing of the genetically related granitic or volcanic activities, in which the positive δ 34 S ore sulfur was derived from a deep igneous source, but the negative δ 34 S sulfur was originated in biogenic sulfur of the accreted sedimentary complex. Within each terrane, δ 34 S values and mineral commodities vary locally, which is called domains in this paper. A few negative δ 34 S minima are observed in the Kinki, Hiroshima and Mino domains. These anomalies may have been brought by the most sediments-dominant granitic magmas generated within the accretionary sedimentary complex.The paired δ 34 S belts, called the Japanese-type pattern, may be unique to island arcs where their fore-arc sediments have been accreted in the arc-front associated with the back-arc rifting.

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Section: Sanyo-naegi Beltmentioning

confidence: 99%

“…HB, Hobenzan granodiorite-granite stock. Outline of the Sasanami cauldron taken from Ikawa and Imaoka (2001). granite intrudes into the Akiyoshi limestone plateau (Fig. 3).…”

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confidence: 99%

Paired Sulfur Isotopic Belts: Late Cretaceous-Paleogene Ore Deposits of Southwest Japan.

舜三

昭

2002

Bull. Geol. Surv. Japan

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“…1994; Satoh et al . 1999; Takeda & Imaoka 1999; Ikawa & Imaoka 2001). In particular, Koido (1991) interpreted the Nohi Rhyolite, occupying an area of approximately 5000 km 2 in the central part of Japan, to be made up of six eruption sequences of voluminous pyroclastic flows from ca 80–58 Ma.…”

Section: Introductionmentioning

confidence: 99%

Lithofacies and eruption ages of Late Cretaceous caldera volcanoes in the Himeji–Yamasaki district, southwest Japan: Implications for ancient large‐scale felsic arc volcanism

Yamamoto¹

2003

Island Arc

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The Himeji–Yamasaki region in the Inner Zone of southwest Japan is underlain mainly by Late Cretaceous volcanic rocks called the Ikuno Group or the Hiromine and Aioi Groups. A new stratigraphic and geochronological study shows that the volcanic rocks in this area consist of 15 eroded caldera volcanoes between 82 and 65 Ma; they are, in order of decreasing age, the Hiromine, Hoden, Ibo, Okawachi, Seppikosan, Hayashida, Shinokubi, Fukusaki, Kurooyama, Ise, Fukadanigawa, Nagusayama, Matobayama, Yumesaki and Mineyama Formations. These calderas vary in diameter from 1 to 20 km and are bounded by steep unconformities; they coalesce and overlap each other. The individual caldera fills are composed mainly of single voluminous pyroclastic flow deposits, which are often interleaved with debris avalanche deposits and occasionally underlie lacustrine deposits. The intracaldera pyroclastic flow deposits are made up of massive, welded or non‐welded tuff breccia to lapilli tuff, and are characterized by their great thickness. The debris avalanche deposits are ill‐sorted breccia, generated by the collapse of the caldera wall toward the caldera floor during the pyroclastic‐flow eruption. The large calderas that are more than 10 km in diameter contain original values of approximately 100 km3 of intracaldera pyroclastic flow deposits. These large calderas are similar to the well‐known Valles‐type calderas in their dimensions, although it is uncertain whether their caldera floors are coherent plates or incoherent pieces. Conversely, the small calderas have diatreme‐like subsurface structures. The variety of the caldera volcanoes in this area is caused by the difference in the volume of caldera‐forming pyroclastic eruptions, as the large and small calderas coexisted. The caldera‐forming eruption rates in Late Cretaceous southwest Japan, including the studied area, were similar to those in late Cenozoic central Andes and northeast Honshu arc, Japan, but obviously smaller than those of late Cenozoic intracratonic caldera clusters in western North America and the Quaternary extensional volcanic arcs in Taupo, New Zealand. The widespread Late Cretaceous felsic igneous rocks in southwest Japan were generated by a long‐term accumulation of low‐rate granitic magmatism at the eastern margin of the Eurasian Plate.

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Anatomy of the Cretaceous Hobenzan pluton, SW Japan: Internal structure of a small zoned pluton, and its genesis

Imaoka

Nakashima

Kamei

et al. 2014

Lithos

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Volcanostratigraphy and geologic structure of Cretaceous Abu Group, and finding of Sasanami cauldron, central part of Yamaguchi Prefecture, Southwest Japan.

Cited by 12 publications

References 12 publications

Paired Sulfur Isotopic Belts: Late Cretaceous-Paleogene Ore Deposits of Southwest Japan.

Paired Sulfur Isotopic Belts: Late Cretaceous-Paleogene Ore Deposits of Southwest Japan.

Lithofacies and eruption ages of Late Cretaceous caldera volcanoes in the Himeji–Yamasaki district, southwest Japan: Implications for ancient large‐scale felsic arc volcanism

Anatomy of the Cretaceous Hobenzan pluton, SW Japan: Internal structure of a small zoned pluton, and its genesis

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