記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

To investigate the nature and origin of across-arc geochemical variations over time in mantle wedge derived magmas, we have carried out a geochemical study of basalts in the NE Japan arc spanning an age range from 35Ma to the present. Back-arc basalts erupted at 24-18 Ma, 10-8 Ma, 6-3Ma and 2.5-0Ma have higher concentrations of both high field strength elements (HFSE) and rare earth elements (REE) [particularly light REE (LREE) and middle REE (MREE)], and higher incompatible trace element ratios compared with frontal-arc basalts at any given time. Geochemical modeling of Nb/Yb versus Nb shows that the frontal-arc and back-arc compositional differences are independent of subduction modification and can, in many cases, be explained by different degrees of melting (higher degrees of melting for frontal-arc magmas and lower degrees of melting for back-arc magmas) of a nearly homogeneous depleted mid-ocean ridge basalt (MORB) mantle (DMM)-like source, although there are several exceptions. These include some Pliocene frontal-arc basalts that may originate from a source that is slightly more depleted than DMM, several 35-32Ma and 24-18Ma back-arc basalts derived from a lithospheric mantle source that is enriched in HFSE compared with DMM, and a rare 16-12Ma basalt that was erupted in the back-arc but was produced by a similar degree of melting to frontal-arc basalts erupted at the same time. Variations in ratios of fluid-mobile and -immobile elements and those of melt-mobile and -immobile elements for the 35-0Ma NE Japan basalts indicate that the principal subduction component added to the source mantle prior to generation of these basalt magmas is a sediment-derived melt. Comparison of Sr and Nd isotopic compositions for Pacific Ocean MORB, the NE Japan basalts and subducting sediments suggests that the isotopic compositions of most post-16Ma more depleted back-arc basalts can be explained by the addition of <2% bulk sediment; the most enriched isotope compositions of the subcontinental lithosphere-derived magmas can be accounted for by addition of a maximum 5-7% Japan Trench Sediment (JTS), if the original Sr and Nd compositions of the lithosphere approximated that of DMM. The Sr and Nd isotope composition of the frontal-arc basalts can be accounted for by the addition of 1-5% JTS. A depleted asthenospheric mantle (DMM-like) upwelling model with interaction between asthenospheric mantle-derived magmas and overlying lithospheric mantle can account for the geochemical characteristics of the 35-0Ma NE Japan basalts. The frontal-arc magmas were generally generated by higher degrees of melting of the shallower part of the asthenospheric mantle, whereas the back-arc magmas resulted from lower degrees of melting of the deeper part of asthenospheric mantle. These latter magmas underwent interaction with the lithospheric mantle, resulting in more enriched Sr and Nd isotopic signatures for the pre-18Ma back-arc basalts and post-22Ma frontal-arc basalts, but less interaction, resulting in more depleted Sr and Nd isotopic signatures, for most of the back-arc basalts younger than 16 Ma.

DOI： 10.1093/petrology/egv073

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：新潟大学  

Petrography and mineral chemistry were studied for gabbroic inclusions in the middle Miocene Ogi Basalt, Sado Island, Japan. The gabbroic inclusions are mainly olivine gabbro and gabbronorite, which are divided into three types based on a mafic-mineral assemblage: Ol-Cpx type with olivine and clinopyroxene, Ol-2Px type with olivine, clinopyroxene, and orthopyroxene, and 2Px type with clinopyroxene and orthopyroxene. Each mineral has similar range in composition. However, some Ol-Cpx type samples rich in modal olivine are characterized with the highest Fo# and NiO content of olivine and highest Mg# and Cr_2O_3 content of clinopyroxene. Spinel included in the olivine also has high Cr#. Primitive basaltic magma is expected as their parent. As far as based on a similarity in mineral chemistry, the gabbroic inclusions are cognate with olivine basalt composing the Ogi Basalt. Consequently, the gabbroic inclusions may represent a plutonic facies of new crust originated by basaltic magmatism during the back-arc rifting to form the Japan Sea.

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その他リンク： http://hdl.handle.net/10191/31989

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

The Sawasaki basalt unit of the Ogi Basalt Member is a middle Miocene submarine volcano formed in a marginal basin, cropping out on the coast of the Ogi Peninsula, Sado Island, Japan. It is approx. 100m thick, more than 4km wide, and is composed of pillow lavas (Sawasaki pillow lava) and overlying fire fountain deposits (Sawasaki pyroclastic rocks). The Sawasaki pillow lava is a pile of nearly-horizontal lava flows. Massive sheet lavas and lava pods grade into pillow lavas. The flat surfaces of the sheet lavas suggest that they spread over a summit plain. The margin of the Sawasaki pillow lava is dominated by thin elongated pillow lobes (20-30cm across) dipping at 45-60 degrees, contrast with the large pillows (40-100cm across) in the core. The proximal lithofacies of the Sawasaki pyroclastic rocks is scoria agglomerate which is composed of tens of stratified beds. Individual beds have a range of clast sizes and abundance of subaqueous bombs (sometimes up to >70%), which suggests that they were formed by submarine spasmodic fire fountain eruptions. Progressive aggradation from a turbulent flow allowed settling of well-preserved fluidal-shaped subaqueous bombs in a fines-depleted matrix. The basal layer shows lamina, scour and imbrication of scoria clasts. The thick scoria agglomerate beds with large subaqueous bombs, derived from energetic fire fountains, were emplaced during transition to higher degrees of hydrovolcanic fragmentation. Alternating scoria lapilli tuff and tuff beds in the distal area may represent the coupled topset and foreset beds formed by deposition from dilute, turbulent flows, and cascading of volcanic debris from the crest of the volcanic hill.

DOI： 10.1111/iar.12091

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：新潟大学教育学部  

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その他リンク： http://hdl.handle.net/10191/13293

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：実業公報社  

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：三条市  

三条市下田地域の地質について解説した。また、調査結果をもとに、八木ヶ鼻の絶壁を作った海底火山活動と溶岩ドームの構造に関する新知見を述べた。

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：新潟大学教育人間科学部附属教育実践総合センター  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：International Mineralogical Conference 2006  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：17th International Sedimentological Congress  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

In the Niigata region of the NE Japan arc, basaltic and intermediate to felsic volcanic rocks (silicic andesite, dacite and rhyolite) have been produced during the Early Miocene, Middle Miocene and Pliocene ages, spanning the pre-Japan Sea opening to post-opening stages. Early Miocene basaltic rocks are characterized by enriched Sr and Nd isotopic signatures (initial Sr-87/Sr-86 (SrI) = 0.70557 to 0.70592 and initial Nd-143/Nd-144 (NdI)=0.51255 to 0.51262), whereas Middle Miocene and Pliocene basaltic rocks are slightly enriched than MORB in terms of SrI (0.70314-0.70416) and NdI (0.51286-0.51310). Early Miocene basaltic rocks are also characterized by higher abundances of HFSE and LREE, and higher Zr/Y compared to Middle Miocene and Pliocene basaltic rocks. The geochemical features of Early Miocene basaltic rocks are almost identical to those of basaltic rocks found in continental rift zones, such as the Rio Grande rift. The different geochemical signatures of Early and Middle Miocene basaltic rocks can be ascribed to the geochemical differences in the mantle source. Apart from andesitic rocks of the Kakuda area, most of Early and Middle Miocene intermediate to felsic volcanic rocks from the Niigata region show significantly higher SrI values (0.70673-0.70773) and lower NdI values (0.51234-0.51254) than Early Miocene basaltic rocks, indicating a lower crustal origin for these more felsic volcanic rocks.

DOI： 10.1016/j.lithos.2005.06.001

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：XXIII General Assembly of the International Union of Geodesy and geophysics 2003  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Temporal-spatial variations in Late Cenozoic volcanic activity in the Chugoku area, southwest Japan, have been examined based on 108 newly obtained K-Ar ages. Lava samples were collected from eight Quaternary volcanic provinces (Daisen, Hiruzen, Yokota, Daikonjima, Sambe, Ooe-Takayama, Abu and Oki) and a Tertiary volcanic cluster (Kibi Province) to cover almost all geological units in the province. Including published age data, a total of 442 Cenozoic radiometric ages are now available. Across-arc volcanic activity in an area approximately 500 km long and 150 km wide can be examined over 26 million years. The period corresponds to syn- and post-back-arc basin opening stages of the island arc. Volcanic activity began in the central part of the rear-arc ca 26 Ma. This was followed by arc-wide expansion at 20 Ma by eruption at two rear-arc centers located at the eastern and western ends. Expansion to the fore-arc occurred between 20 and 12 Ma. This Tertiary volcanic arc was maintained until 4 Ma with predominant alkali basalt centers. The foremost-arc zone activity ceased at 4 Ma, followed by quiescence over the whole arc between 4 and 3 Ma. Volcanic activity resumed at 3 Ma, covering the entire rear-arc area, and continued until the present to form a Quaternary volcanic arc. Adakitic dacite first occurred at 1.7 Ma in the middle of the arc, and spread out in the center part of the Quaternary volcanic arc. Alkali basalt activities ceased in the area where adakite volcanism occurred. Fore-arc expansion of the volcanic arc could be related to the upwelling and expansion of the asthenosphere, which caused opening of the Japan Sea. Narrowing of the volcanic zone could have been caused by progressive Philippine Sea Plate subduction. Deeper penetration could have caused melting of the slab and resulted in adakites. Volcanic history in the Late Cenozoic was probably controlled by the history of evolution of the upper mantle structure, coinciding with back-arc basin opening and subsequent reinitiation of subduction.

DOI： 10.1046/j.1440-1738.2003.00377.x

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：論文集(書籍)内論文   出版者・発行元：Blackwell Publishing Ltd  

The Middle Miocene Ogi Basalt, formed in a back-arc basin, contains products of a variety of eruption processes, from extrusion of pillow lava (Sawasaki pillow lava) associated with formation of hyaloclastite to explosive formation of fluidal spatter and scoriaceous pyroclasts (Sawasaki pyroclastic rocks). The vesiculation textures of juvenile samples were examined to determine eruption style. The Sawasaki pillow lava, hyaloclastite, and pyroclastic rocks are characterized by their high vesicularities: 22—44% for the pillow lava and hyaloclastite, and 19-64% for the pyroclastic rocks. The Sawasaki pyroclastic rocks are characterized by their high contents of small vesicles (&lt
0.2mm across) that show an abrupt increase in vesicle size-frequency patterns. Large vesicles, up to 1 cm in diameter, are minor in the spatter clasts. Population densities calculated for the small vesicles are similar to those of Kilauea lava fountain products. Vesiculated magma that rose slowly erupted effusively to make pillow lava and then hyaloclastite. Subsequently, accelerated magma, rich in small bubbles, must have erupted in lava fountain style through the water column and produced spatter clasts. Those were hydroclastically disintegrated into scoria lapillis, and formed thick scoriaceous pyroclastic rocks, instead of a formation of clastogenic lava on land.

DOI： 10.1029/140GM17

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：The American Geophysical Union  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：山口大学  

Gesu-jima basalt at 10Ma and Gongen-yama basalt at 7Ma erupted in Amakusa-Shimoshima, Southern Kyushu. Major, trace and rare-earth elements, and Sr and Nd isotopic ratios were analyzed from these basalts. Gesu-jima basalt shows within-plate-type signature. Gongen-yama basalt has a slight depletion in Nb. Gesu-jima basalt might be derived from fertile mantle. However, source mantle of Gongen-yama basalt was probably generated by mixing between a large amount of fertile mantle and a small amount of depleted mantle weakly metasomatized by subduction component.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本地質学会  

東北日本弧の北端に位置する積丹半島-支笏湖地域の10～2 Maの火山岩類の主成分, 微量成分, Sr, Nd同位体組成の時空変遷について検討した。その結果, 第四紀火山岩類と同様に, 10 Ma以降の火山岩について背弧側へ向かってのK_2O, Ba, Rb量, ^<143>Nd/^<144>Nd 比の増加, ^<87>Sr/^<86>Sr比の減少傾向が認められた。また, 6 Maを境に, 背弧側の高K_2O量, 高^<143>Nd/^<144>Nd比, 低^<87>Sr/^<86>Sr比の性質がよりフロント側へ拡大し, K_2O量と^<143>Nd/^<144>Nd比が最も低く, ^<87>Sr/^<86>Sr比の高い領域は札幌西部～支笏湖にかけての狭い範囲に収束する傾向がある。同位体的にdepleteした最も背弧側の火山岩は高いBa/Zr, Rb/Zr比を示し, これは中新世中期に日本海側に上昇定置した同位体的にもLIL元素にも枯渇したマントルプリュームに, 島弧的性質(LIL元素に富む)が付加したためではないかと考えられる。この高Ba/Zr, Rb/Zr比の分布は6 Ma以降東へ拡がる。これは東北日本弧下への太平洋プレートの沈み込み角度の増加にともなう現象ではないかと考えられる。

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その他リンク： http://dl.ndl.go.jp/info:ndljp/pid/10810152

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2465/ganko.88.295

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本地質学会  

1980年代後半以降に千島弧，本州弧，琉球弧の火成岩について報告されたSr, Nd同位体の問題を中心に，これと関連した地球化学的研究について概観した．内容は古生代，中生代ジュラ紀，後期白亜紀ー古第三紀，第三紀・第四紀に分けてまとめ，第三紀・第四紀についてはさらに東北日本弧ー千島弧，西南日本弧と九州，琉球弧に分けてレビューした．

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：International Geological Congress  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：International Geological Congress  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：China-Japan symposium on Geochronology, Cosmochronology and Isotope Geology  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.5575/geosoc.96.795

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：International Conf, Geochronol. Cosmochronol. and Isotope Geol  

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記述言語：英語   掲載種別：学位論文（その他）  

中国地方に分布する新生代アルカリ玄武岩類を，主要元素からMF-typeとSA-typeに分け，それぞれの微量元素および同位体化学組成，構成鉱物化学組成から、前者はプレート内玄武岩，後者は陸弧玄武岩の特徴をもつことを指摘した。また、Sr, Nd同位体比の広域的変化から、日本海形成とマグマ発生との関連性が示唆された．

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：American Geophys. Union  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2465/ganko.84.429

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Association of Mineralogical Sciences  

Highly potassic mafic rocks are rarely found in Southwest Japan Arc. Recently, we found highly potassic lamprophyre (minette) from the northeastern part of the Sera Plateau in the Chugoku Mountains. It consists of phenocrysts of phlogopite (mg 85.6, TiO₂ 4.08-4.18), clinopyroxene (diopside-salite), olivine (mg 84.5) and apatite set in a groundmass of poikilitic sanidine ?? anorthoclase, phlogopite, clinopyroxene, apatite and titanomagnetite. The minette is high in K₂O content (5.88 wt%) and K₂O/Na₂O ratio (3.51). The rock shows relatively high concentration of MgO, Ni and Cr, and is strikingly enriched in incompatible elements, particularly Rb, Sr, Ba, Zr and P. The MORB-normalized pattern of the minette is most closely matched by certain alkali basalts of island arcs and continental margins, having negative Nb-anomalies. However, it is highly enriched in incompatible elements compared with island arc basalts. This suggests that the source for the minette is similar to that for the island arc alkali basalt but spiked with K, Rb, Sr, Ba, Zr and P prior to melting.

DOI： 10.2465/ganko.84.270

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記述言語：日本語   出版者・発行元：特定非営利活動法人日本火山学会  

DOI： 10.18940/vsj.1989.1.0_30

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：火成作用研究会  

鮮新世後期から更新世前期の肥薩・北薩火山岩類の全岩化学組成と鉱物化学組成を分析し、火山フロント側によりK2Oに富む火山岩が分布すること、輝石のAl含有量は高圧下の結晶作用を示唆することなどの特徴を明らかにした。東側で圧縮的で、西側で引張的な応力場が働き、これは「北薩の屈曲」に関連する可能性を示した。

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：新潟大学理学部  

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）  

北薩の屈曲に分布する肥薩火山岩類は、矢筈岳系と鬼岳系に区分され、火山フロントから離れた鬼岳系のほうがK2Oに富むことがわかっていた。本研究では、さらに離れたい地に分布する長島の火山岩類を調査分析した結果、さらにK2Oに乏しいことがわかった。長島は北薩の屈曲の背斜軸部に分布することから、より引張応力が働いたためと考えられる。

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記述言語：日本語   出版者・発行元：特定非営利活動法人日本火山学会  

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