Masao Ban

Yamagata University

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Teruki Oikawa

Geological Survey of Japan

Shiho Hirotani

Geological Survey of Japan

Seiko Yamasaki

Geological Survey of Japan

Yuki Nishi

Yamagata University

Tsukasa Ohba

Akita University

Shintaro Hayashi

Morinomiya University of Medical Sciences

Motohiro Sato

Yamagata University

Antonio M. Álvarez‐Valero

Universidad de Salamanca

Yoshinori Takebe

Yamagata University

Yoshiyuki Tatsumi

Kobe University

Cooperative Institutions

Yamagata University

Tohoku University

Japan Agency for Marine-Earth Science and Technology

Universidad de Salamanca

The University of Tokyo

Niigata University

Kyoto University

Graduate School USA

Geological Survey of Japan

Consejo Superior de Investigaciones Científicas

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Petrologic Study of Explosive Pyroclastic Eruption Stage in Shirataka Volcano, NE Japan: Synchronized Eruption of Multiple Magma Chambers

InTech eBooks (2012)

Masao Ban Shiho Hirotani Osamu Ishizuka Naoyoshi Iwat

Some of detailed petrologic studies on rock samples of middle to large sized explosive pyroclastic eruptions recently revealed that the eruptions were caused by simultaneous eruption of multiple distinct magma chambers beneath the volcanoes (e.g., Nakagawa et al. 2003: Shane et al. 2007). It is very important to examine the genetic relationships among the magmas to understand the magma feeding system which caused such explosive eruptions. The explosive pyroclastic eruption stage in Shirataka volcano, NE Japan (Fig. 1) is one of potential candidates for such kind of researches. The aim of this study is to reveal the magma feeding system beneath Shirataka volcano in the explosive pyroclastic eruption stage and examine the genetic relationships among magmas involved in the explosive eruption.

Peléan eruption

Vulcanian eruption

Pyroclastic fall

Phreatic eruption

Effusive eruption

10.5772/24926

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Petrogenesis of Mafic Inclusions in Rhyolitic Lavas from Narugo Volcano, Northeastern Japan

Journal of Petrology (2005)

Masao Ban Koji Takahashi TAKEHIRO HORIE Naruhisa Toya

Mafic inclusions present in the rhyolitic lavas of Narugo volcano, Japan, are vesiculated andesites with diktytaxitic textures mainly composed of quenched acicular plagioclase, pyroxenes, and interstitial glass. When the mafic magma was incorporated into the silica-rich host magma, the cores of pyroxenes and plagioclase began to crystallize (>1000°C) in a boundary layer between the mafic and felsic magmas. Phenocryst rim compositions and interstitial glass compositions (average 78 wt % SiO2) in the mafic inclusions are the same as those of the phenocrysts and groundmass glass in the host rhyolite. This suggests that the host felsic melt infiltrated into the incompletely solidified mafic inclusion, and that the interstitial melt composition in the inclusions became close to that of the host melt (c. 850°C). Infiltration was enhanced by the vesiculation of the mafic magma. Finally, hybridized and density-reduced portions of the mafic magma floated up from the boundary layer into the host rhyolite. We conclude that the ascent of mafic magma triggered the eruption of the host rhyolitic magma.

Phenocryst

Felsic

Melt inclusions

Igneous differentiation

Magma chamber

Silicic

10.1093/petrology/egi025

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Citations (24)

Geochemical Characteristics, Origin, and Evolution of Ore‐Forming Fluids of the Khut Copper Skarn Deposit, West of Yazd in Central Iran

Resource Geology (2014)

Zahedi Azam Mohammad Boomeri Kazuo Nakashima Mohammad Ali Mackizadeh Masao Ban

Abstract The K hut copper skarn deposit is located at about 50 km northwest of T aft City in Y azd province in the middle part of the U rumieh‐ D okhtar magmatic arc. Intrusion of granitoid of O ligocene– M iocene age into carbonate rocks of the T riassic N ayband Formation led to the formation of marble and a calcic skarn. The marble contains high grade Cu mineralization that occurs mainly as open space filling and replacement. Cu ‐rich sulfide samples from the mineralized marble are also anomalous in Au , Zn , and Pb . In contrast, the calcic skarn is only weakly anomalous in Cu and W . The calcic skarn is divided into garnet skarn and garnet–pyroxene skarn zones. Paragenetic relationships and microthermometric data from fluid inclusions in garnet and calcite indicate that the compositional evolution of skarn minerals occurred in three main stages as follows. (i) The early prograde stage, which is characterized by Mg ‐rich hedenbergite ( Hd 53.7 Di 42.3 – Hd 86.1 Di 9.5 ) with Al ‐bearing andradite (69.8–99.5 mol% andradite). The temperature in the early prograde skarn varies from 400 to 500°C at 500 bar. (ii) The late prograde stage is manifested by almost pure andradite (96.2–98.4 mol% andradite). Based on the fluid inclusion data from garnet, fluid temperature and salinity in this stage is estimated to vary from 267 to 361°C and from 10.1 to 21.1 wt% NaCl equivalent, respectively. Pyrrhotite precipitation started during this stage. (iii) The retrograde stage occurs in an exoskarn, which consists of an assemblage of ferro‐actinolite, quartz, calcite, epidote, chlorite, sphalerite, pyrite, and chalcopyrite that partially replaces earlier mineral assemblages under hydrostatic conditions during fracturing of the early skarn. Fluids in calcite yielded lower temperatures ( T < 260°C) and fluid salinity declined to ∼8 wt% NaCl equivalent. The last stage mineralization in the deposit is supergene weathering/alteration represented by the formation of iron hydroxide, Cu ‐carbonate, clay minerals, and calcite. Sulfur isotope data of chalcopyrite (δ 34 S of +1.4 to +5.2‰) show an igneous sulfur source. Mineralogy and mineral compositions of the prograde assemblage of the Khut skarn are consistent with deposition under intermediately oxidized and slightly lower f S 2 conditions at shallow crustal levels compared with those of other typical Fe ‐bearing Cu – Au skarn systems.

Andradite

Grossular

Ore genesis

10.1111/rge.12037

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Citations (11)

Magmatic Evolution and Timescales of the Naruko Caldera System (Ne Honshu): Insight from Orthopyroxene and Quartz Mineral Zoning

А.А. Котов Noriyoshi Tsuchiya Satoshi Okumura Masao Ban Masaoki Uno

Caldera

Mineral resource classification

10.2139/ssrn.5125705

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Petrology of Oninomi monogenetic volcano in Yufu-Tsurumi Graben, Kyushu

Programme and abstracts the Volcanological Society of Japan (1990)

Takehiro Ohta Toshiaki Hasenaka Masao Ban Minoru Sasaki

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Sequence of the 1895 eruption of the Zao volcano, Tohoku Japan

Journal of Volcanology and Geothermal Research (2012)

Kotaro Miura Masao Ban Tsukasa Ohba Akihiko Fujinawa

Phreatic eruption

Peléan eruption

Phreatomagmatic eruption

Pyroclastic fall

Volcanic ash

Phreatic

Effusive eruption

Vulcanian eruption

Dense-rock equivalent

Lithology

Caldera

10.1016/j.jvolgeores.2012.08.005

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Citations (16)

The Tephra Layers Distributed around the Eastern Foot of the Zao Volcano : Ages and Volumes of the Za-To 1 to 4 Tephras

Kazan/Kazan. Dai2shu (2008)

Kotaro Miura Masao Ban Hiroshi Yagi

Foot (prosody)

10.18940/kazan.53.5_151

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Stratigraphy of Kurohana-Yama basalt, Sendai: Pigeonite bearing basalts erupted in the period between late Miocene and early Pliocene.

JOURNAL OF MINERALOGY PETROLOGY AND ECONOMIC GEOLOGY (1997)

Tsukasa Ohba Masao Ban

Detailed stratigraphical investigation revealed that pigeonite-phyric basalts from Kurohana-Yama, Sendai, Japan erupted at late Miocene or early Pliocene, with the age of the eruption is younger than 8 Ma. It is because K-Ar ages of dikes which are stratigraphicaly older than Kurohana-Yama lavas are about 8 Ma (Tsunakawa et al., 1983). The pigeonite basalts from Kurohana-Yama are chemically devided into two types; type A basalts contain higher MgO (7 wt%) and lower Al2O3 (17-18 wt%) than type B basalts (MgO 5.2-5.5 wt% and Al2O3 19-20 wt%). All these basalts contain plagioclase and olivine phenocrysts .Assemblages of phenocryst pyroxenes are various and most of the basalts contain large pigeonite phenocrysts.

Phenocryst

Pigeonite

10.2465/ganko.92.55

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Citations (6)

The origin of compositional variation of mafic magma and genesis of associated silicic magma in the Shirataka volcano, NE Japan: Constraints from Sr isotopic compositions of mafic inclusions and their hosts, with detailed petrologic features of the mafic inclusions

Geochimica et Cosmochimica Acta (2007)

Mitsuhiro Nakagawa Masao Ban Shiho Hirotani

Silicic

Magma chamber

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