start-ver=1.4
cd-journal=joma
no-vol=391
cd-vols=
no-issue=
article-no=
start-page=158
end-page=176
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2025
dt-pub=20250215
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Magnesium isotope composition of volcanic rocks from cold and warm subduction zones: Implications for the recycling of subducted serpentinites and carbonates
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Magnesium (Mg) isotopes are regarded as a sensitive tracer to the contribution from subducted serpentinites and carbonates. However, the source, distribution, and controlling factors of the Mg isotope composition of arc magmas remain unclear. In this study, we investigated the intra-arc and inter-arc variations in Mg isotope compositions of volcanic rocks from two typical cold subduction zones [NE Japan (NEJ) and Izu arcs] and a typical hot subduction zone [SW Japan (SWJ) arc] to address the question. The volcanic rocks from the frontal-arc regions of NEJ and Izu have isotopically heavy Mg (ƒย26Mg = ?0.20 to ?0.08 ๑) compared to the mantle-like ƒย26Mg values of most of volcanic rocks from SWJ and the rear regions of NEJ and Izu arcs (?0.28 to ?0.17 ๑). It is also worth noting that NEJ arc includes samples with ƒย26Mg values (?0.61 to ?0.39 ๑) significantly lower than the mantle, but similar to the < 110 Ma intra-continental basalts from eastern China, which is the first observation in modern arc rocks. No obvious effects of post-eruptive alteration, fractional crystallization, partial melting, or the addition of silicate-rich sediment and oceanic crust components could be identified in the Mg isotope compositions of these volcanic rocks. By contrast, the correlations between the ƒย26Mg values and the proxy for serpentinite component (i.e., 11B/10B and Nb/B ratios) indicate that the component exerts a strong control on the Mg-isotopic signature of these arc rocks. Considering metamorphic reactions in subduction lithologies under P-T conditions postulated for these arcs, the variations in ƒย26Mg values of these arc magmas are unlikely to have been controlled by dehydration of serpentinites in subducted oceanic lithosphere (slab serpentinite). Instead, the high-ƒย26Mg values of frontal-arc rocks are delivered by the fluids from serpentinite formed in the lowermost part of the sub-arc mantle (mantle wedge serpentinite) in channelized flow. Comparatively, such a high-ƒย26Mg signature is invisible in volcanic rocks from rear-arc regions of NEJ and Izu, and the entire SWJ, suggesting that the major Mg carriers in subducted serpentinites (e.g., talc, chlorite, and serpentine) were broken down completely before subducted slabs reached the depth beneath these volcanoes. Moreover, the volcanic rocks with low ƒย26Mg values from the rear arc of NEJ are characterized by high La/Yb and U/Nb ratios as well as low Ti/Eu, Ti/Ti*, and Hf/Hf* ratios, suggesting the involvements of carbonates in their magma sources. The quantitative modeling suggests that < 20 % of sedimentary carbonate (dolomite) was recycled into their mantle source, revealing that Mg-rich carbonate could be incorporated into a deep mantle wedge at rear-arc depths of 150?400 km in subduction zones.
en-copyright=
kn-copyright=

en-aut-name=ZhangWei
en-aut-sei=Zhang
en-aut-mei=Wei
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=HuangFang
en-aut-sei=Huang
en-aut-mei=Fang
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China
kn-affil=
en-keyword=Magnesium isotopes
kn-keyword=Magnesium isotopes
en-keyword=Arc magmas
kn-keyword=Arc magmas
en-keyword=Mantle wedge serpentinite
kn-keyword=Mantle wedge serpentinite
en-keyword=Slab serpentinite
kn-keyword=Slab serpentinite
en-keyword=Carbonate recycle
kn-keyword=Carbonate recycle
END

start-ver=1.4
cd-journal=joma
no-vol=128
cd-vols=
no-issue=5
article-no=
start-page=e2022JB025670
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2023
dt-pub=20230425
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Lithium Isotope Constraints on Slab and Mantle Contribution to Arc Magmas
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Dehydration of subducting oceanic lithosphere (slab) induces Li-isotope fractionation between the fluid and the slab, suggested by the ƒย7Li variation (?10๑) in exhumed subduction complexes. Given that arc magmas represent melt of the supraslab mantle, a large ƒย7Li variation is anticipated for arc volcanic rocks. However, the ƒย7Li values in these rocks are mostly homogeneous within the range of mid-ocean ridge basalts (+1.6 to +5.6๑). The lack of a subduction-related ƒย7Li signature has been explained by (1) homogenization by mixing of different magma sources, (2) loss of Li from the slab via dehydration, or (3) homogenization by diffusive exchange of slab-derived Li and the mantle. The Chugoku district in SW Japan is an ideal place to study the process responsible for Li-isotope variation in arc magmas, since the Chugoku volcanic rocks show large ƒย7Li variation (?1.9 to +7.4๑). High ƒย7Li values (+6.3 to +7.4๑) are found in some high-Sr andesites and dacites (adakites) whereas low ƒย7Li values (?1.0 to ?0.1๑) are found in high-Mg andesites. The parental magmas of these rocks have been sourced from subducted oceanic crust and sediments, respectively, with various extents of the interaction with wedge mantle. The limited extents of Li isotope modification are indicated by the similarity of the ƒย7Li values of these rocks and their supposed sources. The models for a slab dehydration and a diffusive exchange between slab-derived melt and mantle demonstrate that the ƒย7Li signatures of the sources can be preserved in the adakites if they ascent rapidly in mantle.
en-copyright=
kn-copyright=

en-aut-name=ZhangWei
en-aut-sei=Zhang
en-aut-mei=Wei
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=
en-keyword=SW Japan
kn-keyword=SW Japan
en-keyword=slab
kn-keyword=slab
en-keyword=lithium isotope
kn-keyword=lithium isotope
en-keyword=arc magma
kn-keyword=arc magma
en-keyword=melt transport
kn-keyword=melt transport
END

start-ver=1.4
cd-journal=joma
no-vol=125
cd-vols=
no-issue=10
article-no=
start-page=e2019JB019143
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2020
dt-pub=202010
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Feedback of Slab Distortion on Volcanic Arc Evolution: Geochemical Perspective From Late Cenozoic Volcanism in SW Japan
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Southwest Japan is an island arc formed by subduction of the Philippine Sea (PHS) plate. The Quaternary magmatism in this region is characterized by eruptions of high-Sr andesites and dacites, considered to have been derived by melting of the PHS plate. The loci of these volcanoes spatially coincide with seismic discontinuities of the subducted PHS plate. Thus, the magmatism is interpreted as the result of slab melting at the plate tears. However, the processes that promote slab tearing remain unclear. In this study, we applied geochronological and geochemical analyses to late Cenozoic volcanic rocks in southwest Japan as tracers of slab morphology. Two different magma types, ocean-island basalt (OIB) and island-arc basalt (IAB), have occurred over 12 million years (Myr). These two magmas are attributed to different integrations of melts extracted from an originally fertile mantle; the OIBs from high temperature melt (1,300?1,400‹C) were extracted at a depth of 40?80 km, whereas the IABs were extracted from a shallower, lower temperature region (30?60 km, 1,200?1,350‹C). Secular change in Sr enrichment of IAB likely arose due to a transition of slab-derived fluids, incorporated into magmas as they formed, from water- to melt-dominant one. Progressive shallowing of the subducted PHS plate is responsible for secular change in the properties of slab-derived fluids as well as rollback of OIB volcanoes. Production of chemically variable magmas in the Chugoku district is the surface expression of distorting slab morphology by interaction between mantle and the subducting plate.
en-copyright=
kn-copyright=

en-aut-name=NguyenTai Truong
en-aut-sei=Nguyen
en-aut-mei=Tai Truong
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=Pineda]VelascoIvan
en-aut-sei=Pineda]Velasco
en-aut-mei=Ivan
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

affil-num=1
en-affil=Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=4
en-affil=Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=
en-keyword=subduction zone
kn-keyword=subduction zone
en-keyword=volcanism
kn-keyword=volcanism
en-keyword=mantle
kn-keyword=mantle
en-keyword=basalt
kn-keyword=basalt
en-keyword=slab
kn-keyword=slab
END

start-ver=1.4
cd-journal=joma
no-vol=127
cd-vols=
no-issue=5
article-no=
start-page=e2021JB023328
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2022
dt-pub=20220525
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Bilateral Heterogeneity in an Upwelling Mantle via Double Subduction of Oceanic Lithosphere
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Vietnam is a major field of Cenozoic volcanism in Southeast (SE) Asia. Two contrasting models have been proposed to explain the mantle upwelling and volcanism in this region; collision of the Indian and Eurasian continents or subduction of the Pacific or Indo-Australian oceanic lithosphere. To place constraints on the origin of the intraplate volcanism in SE Asia, new geochronological and geochemical data for Cenozoic basalts in Vietnam are presented. Based largely on Sr-Nd-Pb isotope systematics, it was found that the sources of basalts from Central and Southern Vietnam are chemically distinct forming a sharp boundary at 13.5‹N. The basalts north of the boundary show isotopic features similar to Enriched Mantle type 2 (EM2) ocean island basalts. Whereas the basalts south of the boundary show isotopic features similar to Enriched Mantle type 1 (EM1) ocean island basalts. The EM1 and EM2 basalts display positive Sr anomalies and elevated Pb/Ce and Th/La ratios, respectively. Such features suggest the origins of the sources through the recycling of deeply-subducted crustal lithologies. Furthermore, subduction of dense oceanic lithosphere can induce a convecting cell in the upper mantle. Therefore, we suggest that the chemically different basalts from Central and Southern Vietnam represent the surface expression of melting in two different convecting cells, one is driven by subduction of the Pacific plate and the other by subduction of the Indo-Australian plate.
en-copyright=
kn-copyright=

en-aut-name=DaoNghiem Van
en-aut-sei=Dao
en-aut-mei=Nghiem Van
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=KobayashiKatsura
en-aut-sei=Kobayashi
en-aut-mei=Katsura
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=NgoThanh Xuan
en-aut-sei=Ngo
en-aut-mei=Thanh Xuan
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=TrinhSon Hai
en-aut-sei=Trinh
en-aut-mei=Son Hai
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=4
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University,
kn-affil=

affil-num=5
en-affil=Department of Geology, Hanoi University of Mining and Geology
kn-affil=

affil-num=6
en-affil=Vietnam Institute of Geoscience and Mineral resources
kn-affil=
en-keyword=intraplate volcanism
kn-keyword=intraplate volcanism
en-keyword=Sr-Nd-Pb isotopes
kn-keyword=Sr-Nd-Pb isotopes
en-keyword=EM1-EM2 basalts
kn-keyword=EM1-EM2 basalts
en-keyword=recycled crustal materials
kn-keyword=recycled crustal materials
en-keyword=subduction-induced mantle upwelling
kn-keyword=subduction-induced mantle upwelling
en-keyword=SE Asia
kn-keyword=SE Asia
END

start-ver=1.4
cd-journal=joma
no-vol=95
cd-vols=
no-issue=4
article-no=
start-page=165
end-page=177
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2019
dt-pub=20190411
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Hypervelocity collision and water-rock interaction in space preserved in the Chelyabinsk ordinary chondrite
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=A comprehensive geochemical study of the Chelyabinsk meteorite reveals further details regarding its history of impact-related fragmentation and melting, and later aqueous alteration, during its transit toward Earth. We support an similar to 30 Ma age obtained by Ar-Ar method (Beard et al., 2014) for the impact-related melting, based on Rb-Sr isotope analyses of a melt domain. An irregularly shaped olivine with a distinct 0 isotope composition in a melt domain appears to be a fragment of a silicate-rich impactor. Hydrogen and Li concentrations and isotopic compositions, textures of Fe oxyhydroxides, and the presence of organic materials located in fractures, are together consistent with aqueous alteration, and this alteration could have pre-dated interaction with the Earth's atmosphere. As one model, we suggest that hypervelocity capture of the impact-related debris by a comet nucleus could have led to shock-wave-induced supercritical aqueous fluids dissolving the silicate, metallic, and organic matter, with later ice sublimation yielding a rocky rubble pile sampled by the meteorite.
en-copyright=
kn-copyright=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KunihiroTak
en-aut-sei=Kunihiro
en-aut-mei=Tak
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=OtaTsutomu
en-aut-sei=Ota
en-aut-mei=Tsutomu
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=SakaguchiChie
en-aut-sei=Sakaguchi
en-aut-mei=Chie
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=TanakaRyoji
en-aut-sei=Tanaka
en-aut-mei=Ryoji
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

en-aut-name=KobayashiKatsura
en-aut-sei=Kobayashi
en-aut-mei=Katsura
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=7
ORCID=

en-aut-name=YamanakaMasahiro
en-aut-sei=Yamanaka
en-aut-mei=Masahiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=8
ORCID=

en-aut-name=ShimakiYuri
en-aut-sei=Shimaki
en-aut-mei=Yuri
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=9
ORCID=

en-aut-name=BeboutGray E.
en-aut-sei=Bebout
en-aut-mei=Gray E.
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=10
ORCID=

en-aut-name=MiuraHitoshi
en-aut-sei=Miura
en-aut-mei=Hitoshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=11
ORCID=

en-aut-name=YamamotoTetsuo
en-aut-sei=Yamamoto
en-aut-mei=Tetsuo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=12
ORCID=

en-aut-name=MalkovetsVladimir
en-aut-sei=Malkovets
en-aut-mei=Vladimir
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=13
ORCID=

en-aut-name=GrokhovskyVictor
en-aut-sei=Grokhovsky
en-aut-mei=Victor
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=14
ORCID=

en-aut-name=KorolevaOlga
en-aut-sei=Koroleva
en-aut-mei=Olga
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=15
ORCID=

en-aut-name=LitasovKonstantin
en-aut-sei=Litasov
en-aut-mei=Konstantin
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=16
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=4
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=5
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=6
en-affil=Okayama Univ, Inst Planetary Mat, Pheast Mem Lab Geochem & Cosmochem
kn-affil=

affil-num=7
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=8
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=9
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=10
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=11
en-affil=Graduate School of Natural Sciences, Nagoya City University
kn-affil=

affil-num=12
en-affil=Institute of Low Temperature Science, Hokkaido University
kn-affil=

affil-num=13
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=14
en-affil=Institute of Physics and Technology, Ural Federal University
kn-affil=

affil-num=15
en-affil=Institute of Mineralogy, Ural Branch of the Russian Academy of Sciences South-Ural State University
kn-affil=

affil-num=16
en-affil=V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences
kn-affil=
en-keyword=ordinary chondrite
kn-keyword=ordinary chondrite
en-keyword=chronology
kn-keyword=chronology
en-keyword=geochemistry
kn-keyword=geochemistry
en-keyword=impact melting
kn-keyword=impact melting
en-keyword=asteroid
kn-keyword=asteroid
en-keyword=comet
kn-keyword=comet
END

start-ver=1.4
cd-journal=joma
no-vol=60
cd-vols=
no-issue=8
article-no=
start-page=1681
end-page=1715
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2019
dt-pub=20190912
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Transition from Plume-driven to Plate-driven Magmatism in the Evolution of the Main Ethiopian Rift
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract= New K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data are presented for Oligocene to recent mafic volcanic rocks from the Ethiopian Plateau, the Main Ethiopian Rift (MER), and the Afar depression. Chronological and geochemical data from this study are combined with previously published datasets to reveal secular variations in magmatism throughout the entire Ethiopian volcanic region. The mafic lavas in these regions show variability in terms of silica-saturation (i.e. alkaline and sub-alkaline series) and extent of differentiation (mafic through intermediate to felsic). The P-T conditions of melting, estimated using the least differentiated basalts, reveal a secular decrease in the mantle potential temperature, from when the flood basalt magmas erupted (up to 1600 degrees C) to the time of the rift-related magmatism (<1500 degrees C). Variations in the Sr-Nd-Pb isotopic compositions of the mafic lavas can account for the involvement of multiple end-member components. The relative contributions of these end-member components vary in space and time owing to changes in the thermal condition of the asthenosphere and the thickness of the lithosphere. The evolution of the Ethiopian rift is caused by a transition from plume-driven to plate-driven mantle upwelling, although the present-day mantle beneath the MER and the Afar depression is still warmer than normal asthenosphere.
en-copyright=
kn-copyright=

en-aut-name=FeyissaDejene Hailemariam
en-aut-sei=Feyissa
en-aut-mei=Dejene Hailemariam
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=BizunehTesfaye Demissie
en-aut-sei=Bizuneh
en-aut-mei=Tesfaye Demissie
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=TanakaRyoji
en-aut-sei=Tanaka
en-aut-mei=Ryoji
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=KabetoKurkura
en-aut-sei=Kabeto
en-aut-mei=Kurkura
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=4
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=5
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=6
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=
en-keyword=Ethiopian Plateau
kn-keyword=Ethiopian Plateau
en-keyword=Ethiopian rift
kn-keyword=Ethiopian rift
en-keyword=Afar depression
kn-keyword=Afar depression
en-keyword=mantle source
kn-keyword=mantle source
en-keyword=mantle melting
kn-keyword=mantle melting
END

start-ver=1.4
cd-journal=joma
no-vol=43
cd-vols=
no-issue=1
article-no=
start-page=147
end-page=161
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2018
dt-pub=20181025
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Determination of Abundances of Fifty-Two Elements in Natural Waters by ICP-MS with Freeze-Drying Pre-concentration
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract= To precisely determine the abundances of fifty-two elements found within natural water samples, with mass fractions down to fg g(-1) level, we have developed a method which combines freeze-drying pre-concentration (FDC) and isotope dilution internal standardisation (ID-IS). By sublimation of H2O, the sample solution was reduced to < 1/50 of the original volume. To determine element abundance with accuracy better than 10%, we found that for solutions being analysed by mass spectrometry the HNO3 concentration should be > 0.3 mol l(-1) to avoid hydrolysis. Matrix-affected signal suppression was not significant for the solutions with NaCl concentrations lower than 0.2 and 0.1 cg g(-1) for quadrupole ICP-MS and sector field ICP-MS, respectively. The recovery yields of elements after FDC were 97-105%. The detection limits for the sample solutions prepared by FDC were <= 10 pg g(-1), except for Na, K and Ca. Blanks prepared using FDC were at pg-levels, except for eleven elements (Na, Mg, Al, P, Ca, Mn, Fe, Co, Ni, Cu and Zn). The abundances of fifty-two elements in bottled drinking water were determined from five different geological sources with mass fractions ranging from the fg g(-1) to mu g g(-1) level with high accuracy.
en-copyright=
kn-copyright=

en-aut-name=HoangQue D.
en-aut-sei=Hoang
en-aut-mei=Que D.
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=KunihiroTak
en-aut-sei=Kunihiro
en-aut-mei=Tak
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=SakaguchiChie
en-aut-sei=Sakaguchi
en-aut-mei=Chie
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=YamanakaMasahiro
en-aut-sei=Yamanaka
en-aut-mei=Masahiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=4
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=5
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=6
en-affil=The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University
kn-affil=
en-keyword=pre-concentration
kn-keyword=pre-concentration
en-keyword=freeze-drying
kn-keyword=freeze-drying
en-keyword=ID-IS
kn-keyword=ID-IS
en-keyword=natural water
kn-keyword=natural water
en-keyword=drinking water
kn-keyword=drinking water
END

start-ver=1.4
cd-journal=joma
no-vol=10
cd-vols=
no-issue=1
article-no=
start-page=3022
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2019
dt-pub=201907
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Origin of ocean island basalts in the West African passive margin without mantle plume involvement
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract= The geochemical variabilities in intraplate basalts (IB) from the West African passive margin (WAPM) region, have generally been employed to indicate the presence of recycled materials in an associated upwelling mantle plume. However, the absence of time-progressive linear hotspot tracks in WAPM-IB make it difficult to explain their genesis solely by the mantle plume hypothesis. Here, we show that the Sr?Nd?Hf?Pb isotopic variations in basalts from most of the WAPM-IB could have mainly attributed to the derivation from two types of fusible regions of the refertilized subcontinental lithospheric mantle (SCLM) and the sub-lithospheric mantle. The locations and magma genesis of WAPM-IB are strongly related to the distance from the Mesozoic rift axis and the structure of the rifted SCLM. The melting of the source region can possibly be attributed to small-scale mantle convection at the base of the SCLM without the involvement of a mantle plume.
en-copyright=
kn-copyright=

en-aut-name=BelayIyasu Getachew
en-aut-sei=Belay
en-aut-mei=Iyasu Getachew
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=TanakaRyoji
en-aut-sei=Tanaka
en-aut-mei=Ryoji
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=KitagawaHiroshi
en-aut-sei=Kitagawa
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=KobayashiKatsura
en-aut-sei=Kobayashi
en-aut-mei=Katsura
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=NakamuraEizo
en-aut-sei=Nakamura
en-aut-mei=Eizo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

affil-num=1
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=2
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=3
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=4
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=

affil-num=5
en-affil=The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University
kn-affil=
END