Atsushi Kamei
Shimane University
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Publication
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Geochemistry Geophysics Geosystems | 2014
Jun-Ichi Kimura; James B. Gill; Tomoyuki Kunikiyo; Isaku Osaka; Yusuke Shimoshioiri; Maiko Katakuse; Susumu Kakubuchi; Takashi Nagao; Katsuhiko Furuyama; Atsushi Kamei; Hiroshi Kawabata; Junichi Nakajima; Peter E. van Keken; Robert J. Stern
In response to the subduction of the young Shikoku Basin of the Philippine Sea Plate, arc magmas erupted in SW Japan throughout the late Cenozoic. Many magma types are present including ocean island basalt (OIB), shoshonite (SHO), arc-type alkali basalt (AB), typical subalkalic arc basalt (SAB), high-Mg andesite (HMA), and adakite (ADK). OIB erupted since the Japan Sea back-arc basin opened, whereas subsequent arc magmas accompanied subduction of the Shikoku Basin. However, there the origin of the magmas in relation to hot subduction is debated. Using new major and trace element and Sr-Nd-Pb-Hf isotope analyses of 324 lava samples from seven Quaternary volcanoes, we investigated the genetic conditions of the magma suites using a geochemical mass balance model, Arc Basalt Simulator version 4 (ABS4), that uses these data to solve for the parameters such as pressure/temperature of slab dehydration/melting and slab flux fraction, pressure, and temperature of mantle melting. The calculations suggest that those magmas originated from slab melts that induced flux melting of mantle peridotite. The suites differ mostly in the mass fraction of slab-melt flux, increasing from SHO through AB, SAB, HMA, to ADK. The pressure and temperature of mantle melting decreases in the same order. The suites differ secondarily in the ratio of altered oceanic crust to sediment in the source of the slab melt. The atypical suites associated with hot subduction result from unusually large mass fractions of slab melt and unusually cool mantle temperatures.
American Mineralogist | 2012
Toshiaki Shimura; Junji Akai; Biljana Lazic; Thomas Armbruster; Masaaki Shimizu; Atsushi Kamei; Kazuhiro Tsukada; Masaaki Owada; Masaki Yuhara
Abstract Högbomite-group minerals are complex Fe-Mg-Zn-Al-Ti oxides related to the spinel group. Their polysomatic structure is composed of spinel (S) and nolanite (N) modules. The new polysome magnesiohögbomite-2N4S (IMA 2010-084) was found in the Sør Rondane Mountains, East Antarctica. It occurs in Mg-Al-rich, Si-poor skarns, characterized by a corundum-spinel-phlogopite-clinochlore assemblage. The new magnesiohögbomite polysome formed during the retrograde metamorphic stage. Magnesiohögbomite-2N4S appears macroscopically orange red, the streak is light orange colored. Euhedral crystals are hexagonal plates or prisms with cleavage planes on {001}. The mineral is optically uniaxial (-) and pleochroic with O = reddish brown and E = pale brown. The mean refractive index calculated from reflectance data in air at 589 nm is 1.85(3). The calculated density is 3.702(2) g/cm3. The Mohs hardness is 6.5-7, and VHN300 = 1020-1051, mean 1032 kg/mm2. The crystal structure of the new polysome magnesiohögbomite-2N4S has been solved and refined (R1 = 2.74%) from single-crystal XRD data. The crystal chemical formula is T10M24O46(OH)2 where T and M represent tetrahedral and octahedral sites. The mineral is hexagonal, space group P63mc (no. 186), a = 5.71050(10), c = 27.6760(4) Å, Z = 1, V = 781.60(2) Å3. The strongest lines in the powder XRD pattern [d (Å), I (%), hkl] are: 2.8561(4), 37, 110; 2.6120(3), 39, 109; 2.42818(16), 100, 116; 2.4160(4), 39, 1010; 2.01181(13), 50, 208; 1.54892(16), 35, 2110; 1.42785(6), 57, 220. Strongest peaks in Raman spectra are at 302, 419, 479, 498, 709, 780, and 872 cm-1, with a broad OH-characteristic absorption around 3400 cm-1. The mean chemical composition (wt%) is SiO2 0.05, TiO2 7.08, SnO2 0.15, Al2O3 66.03, Cr2O3 0.02, Fe2O3 0.50, FeO 4.87, MnO 0.06, MgO 18.71, CaO 0.01, ZnO 0.96, NiO 0.01, CoO 0.02, F 0.06, Cl 0.01, H2O 1.00, sum 99.51. The simplified formula is (Mg8.2Fe1.2Zn0.2)2+(Al22.7Fe0.1)3+ Ti4+1.6O46(OH)2 and ideal formula is Mg10Al22Ti2O46(OH)2. This mineral is a solid solution between the two ideal end-members, (Mg,Fe,Zn)102+(Al,Fe)223+Ti24+O46(OH)2 and (Mg,Fe,Zn)82+(Al,Fe)263+O46(OH)2.
Gondwana Research | 2006
Yasuhito Osanai; Masaaki Owada; Atsushi Kamei; Takuji Hamamoto; Hiroo Kagami; Tsuyoshi Toyoshima; Nobuhiko Nakano; Tran Ngoc Nam
Lithos | 2009
Atsushi Kamei; Yasuyuki Miyake; Masaaki Owada; Jun-Ichi Kimura
Precambrian Research | 2013
Yasuhito Osanai; Yoshifumi Nogi; Sotaro Baba; Nobuhiko Nakano; Tatsuro Adachi; Tomokazu Hokada; Tsuyoshi Toyoshima; Masaaki Owada; M. Satish-Kumar; Atsushi Kamei; Ippei Kitano
Journal of Mineralogy, Petrology and Economic Geology | 1997
Atsushi Kamei; Masaaki Owada; Yasuhito Osanai; Takuji Hamamoto; Hiroo Kagami
Precambrian Research | 2013
Atsushi Kamei; Kenji Horie; Masaaki Owada; Masaki Yuhara; Nobuhiko Nakano; Yasuhito Osanai; Tatsuro Adachi; Yuki Hara; Madoka Terao; Shinjiro Teuchi; Toshiaki Shimura; Kazuhiro Tsukada; Tomokazu Hokada; Chika Iwata; Kazuyuki Shiraishi; Hideo Ishizuka; Yuhei Takahashi
Precambrian Research | 2013
Naho Otsuji; M. Satish-Kumar; Atsushi Kamei; Noriyoshi Tsuchiya; Tetsuo Kawakami; Masahiro Ishikawa; Geoffrey H. Grantham
Precambrian Research | 2013
Masaaki Owada; Atsushi Kamei; Kenji Horie; Toshiaki Shimura; Masaki Yuhara; Kazuhiro Tsukada; Yasuhito Osanai; Sotaro Baba
Lithos | 2014
Teruyoshi Imaoka; Kazuo Nakashima; Atsushi Kamei; Tetsumaru Itaya; T. Ohira; Mariko Nagashima; N. Kono; Michio Kiji
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National Institute of Advanced Industrial Science and Technology
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