著者

寺林 優 山本 啓司 亀井 淳志

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.123, no.8, pp.599-612, 2017-08-15 (Released:2017-09-05)

参考文献数

41

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領家帯は,白亜紀の花崗岩類とそれらに密接な関係をもつ変成岩類からなる地体構造単位である.これまでに,構造地質学,変成岩および深成岩に関する岩石学,地球化学,年代学などからの研究が数多くなされてきた.領家帯は,下部グラニュライト相に達するような広域変成作用を被っていることから,かつての島弧の地殻断面が隆起・露出していると考えられている.島弧地殻内部で発生する地震の震源は,地下約20kmよりも浅い領域に集中し,それよりも深い領域で稀なのは,地殻の深部では岩石が流動的に変形するために地震を引き起こすような脆性破壊が起きにくいことが理由とされている.島弧地殻を構成している珪長質岩石の変形機構は,石英と長石のレオロジーから,300°Cから450°Cの間の温度条件で脆性から塑性に遷移すると推定され,島弧の地温勾配を25°C/km程度と仮定すると,脆性-塑性遷移領域は12kmから18kmの深さの範囲にある.本巡検では,島弧の深部地殻での花崗岩質マグマの挙動,中部地殻でのコンピテントレイヤーの形成とその破壊における流体の挙動という視点から岩国-柳井地域の領家帯を案内する.

著者

山本 啓司 寺林 優 大麻 広幸 金子 慶之 安間 了

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.110, no.2, pp.119-122, 2004 (Released:2005-01-07)

参考文献数

15

被引用文献数

8 8

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Pelitic metamorphic rocks of the Ryoke Belt are distributed in the Rokuroshi area, southern part of Iwakuni district. Dark-brown biotite schist was locally silicified and decolorized to form milky-white “silicified domain”. Quartz veins were developed in both of the biotite schist and silicified domain. The veins in biotite schist are generally parallel to the schistosity and form boudinage due to ductile flow of the host rock. The veins in silicified domain are oblique to the schistosity with medium to high angles and have not undergone ductile deformation except for some schistosity-parallel veins. The mode of occurrence of these veins indicates that the silicified domain is much more competent than the biotite schist. Ductile deformation after the silicification was accommodated by viscous flow of biotite schist. The silicification probably results from dissolution-precipitation processes which may have raised pore pressure to cause hydraulic fracturing.

著者

丸山 茂徳 寺林 優 藤岡 換太郎

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.98, no.3, pp.319-349, 1989-06-25 (Released:2011-02-17)

参考文献数

143

被引用文献数

2 4

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A brief review of the study on ophiolite is given. 165 years have passed already since a first use of the term “ophiolite” by BRONGNIART (1813), but still have not yet obtained a broadly satisfying solution on its origin and emplacement. However, the rapidly increased data set during the last 15 years on both on-land ophiolite and oceanfloors clearly indicate the strong constraints on its origin and emplacement.The period during 1813-1927 was a time of description of ophiolite. BRONGNIART (1827) classified ophiolite into a group of igneous rocks, since then began a debate whether ophiolitic peridotite is igneous or the other in origin. SUESS (1909) had noticed that ophiolites appear characteristically in orogenic belts. It was STEINMANN (1927) who had first recognized a close association of peridotite, gabbro, diabase-spilite, and radiolarian chert suggesting a deep sea origin of ophiolite. The significance of his finding has never been looked back until the revolutional period of plate tectonics in the late' 60s.The second period of 1927-1949 was the time of debate on igeneous origin. BOWEN and his coworkers insisted igneous origin based on experimental petrology for the ultramafic rocks in general. But if so, an abnormally high temperature ca. 1, 900°C was necessary to explain the occurrence of dunite. BENSON (1926) pointed out that if BOWEN'S idea is true, the country rocks of ophiolite must be subjected a high-temperature contact metamorphism, but not in the field. HESS (1939) has given a new idea of serpentinite magma to solve the problem, but its possibility had completely been disproved by the experiment of MgO-SiO2-H2O by BOWEN and TUTTLE (1949).The third period (1949-1959) began by a break-through idea of DE ROEVER (1957), who speculated that ophiolitic peridotite is a piece of mantle material, which was brought into an orogen by a tectonic process.The fourth period (1959-1973) started by BRUNN (1959) who compared ophiolite with the rocks in the Mid-Atlantic Ridge. This period (1959-1973) was the time of plate tectonics. During the early' 60s the ocean-floor spreading theory was proposed by HESS and DIETZ, and both thought that the layer 3 is composed of serpentinite oreclogite. The year 1969 was a memorial year, when both MOORES and DAVIES distinguished cumulate peridotite from the underlying residue tectonite, the latter of which is a refractory mantle after the formation of oceanic crust by partial fusion of mantle peridotite. The best example of ophiolite was the Troodos massif in Cyprus, where the extensive-scale of parallel dike swarm develops indicating ocean-floor spreading. Thereafter an ophiolite boom has come out, and flood of papers appeared to regard ophiolite to be of mid-oceanic ridge in origin. However, several geologists have doubted mid-oceanic ridge origin by the facts of much thinner crust, more silicic volcanic composition, and frequent occurrence of phenocrystic augite in ophiolites. MIYASHIRO (1973) solved such problems, and concluded that Troodos was formed in an island-arc setting. This paper was very shocking for geologists who wanted to establish the basic framework of orogeny by plate tectonics in those days, but epoch-making on the study of ophiolite, and corresponding to the time, when the method of study has changed to be modernized and more interdisciplinary.

著者

青木 一勝 飯塚 毅 平田 岳史 丸山 茂徳 寺林 優

出版者

日本地質学会

雑誌

地質學雜誌 (ISSN:00167630)

巻号頁・発行日

vol.113, no.5, pp.171-183, 2007-05-15

被引用文献数

10 63

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四国中央部大歩危地域に分布する三波川結晶片岩類は,原岩層序に基づき構造的上位から下位に向かい三縄層,小歩危層,川口層に分類されてきた.今回,それぞれの層から火成ジルコンを分離し,LA-ICP-MSを用いてU-Pb年代測定を行った結果,三縄層中のジルコンの多くが1900-1800Maの火成年代を示した.一方,小歩危層・川口層中のジルコンから得られた火成年代は三縄層よりも若く,その中で最も若い年代は,それぞれ92±4Ma,82±11Maであった.両層の堆積年代は更に若く,その年代は,四万十帯北帯の付加年代と一致する.このことから,従来,三波川帯と見なされてきた小歩危層,川口層は,四万十帯北帯であることが明らかになった.したがって,三縄層と小歩危層の層境界は,三波川帯/四万十帯境界にあたる.また,大歩危地域における構造的累重関係は,三波川変成帯が四万十帯の構造的上位に位置することを示している.

著者

寺林 優 越智 信 仲谷 英夫

出版者

公益社団法人地盤工学会

雑誌

土と基礎 (ISSN:00413798)

巻号頁・発行日

vol.53, no.1, pp.B6-B7, 37-39, 2005-01-01

被引用文献数

1

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The coastal Takamatsu-city was flooded by the storm surge by the typhoon 0416 The maximum tide T P+2 46 m was recorded at the Takamatsu Port at 23 00 in Aug 30, 2004 The authors started the observation from the beginning of the flood by storm surge in the western Takamatsu-city The flood depth was measured at more than 700 points from flood marks, and the maximum depth is 172 centimeters The process of inflow from the coast to the inland through the underpass, has been clarified by the observation and the hearing research The flood districts were not controlled by the sea level and/or back current along river but the presence of channel such as underpass