著者

酒井 治孝

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.114, no.1, pp.113-117, 2005-02-25 (Released:2009-11-12)

参考文献数

8

被引用文献数

1 1

著者

ホッペ グンナー 岩田 修二

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.90, no.2, pp.62-72, 1981-04-25 (Released:2010-11-18)

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ヴァイクゼル氷期 (最終氷期) に広く氷床におおわれたスカンジナビアや北極海の島じまのなかに, 氷におおわれることからまぬがれた地域があったかどうかは, 生物学と地球科学における重要な問題になっている。この問題に加えて, 氷床の大きさと海面変化との関係, 過去の気候条件などの問題を解決するために, ストックホルム大学の自然地理学教室では, 過去25年間にわたって数多くの探険・調査をおこなってきた。氷河擦痕からみて, シェットランド島は, ヴァイクゼル氷期には東側から拡大してきた氷床 (スカンジナビア氷床) によって完全におおわれたことがあった。その後一時期, 島は, スカンジナビア氷床から分離した孤立アイスキャップにおおわれていた。スバールバード周辺では, 隆起汀線から知られた解氷後の地盤隆起と, 氷河の擦痕から, 次のような氷河の変遷があきらかになった。まず, 氷河が拡大し, それぞれの島ごとにアイスキャップをつくり, 次にそれらが合体して大きな氷床になった。最大拡張期には, バレンツ海に氷床の中心があった。その後, 氷河の拡大とは逆の変遷をへて氷河は現在の状態にまで縮小したヴァイクゼル氷期のアイスランドは, 小さなヌナタックをのぞいて, 大陸だなのへりまで氷床におおわれていたことがあきらかになった。これらをまとめると, ノルウェー海をとりまく地域では, ヴァイクゼル氷期には, 現在の海岸線までは確実に, おそらくは大陸だなのへりまで氷床におおわれていたといえる。しかし, バレンツ海の氷床の範囲はまだよくわかっておらず, 1980年におこなわれるイーメル80の調査に大きな期待がかけられている。

著者

千秋 博紀 丸山 茂徳 李野 修士

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.119, no.6, pp.1215-1227, 2010-12-25 (Released:2011-03-17)

参考文献数

57

被引用文献数

6 6

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It has long been believed that granite remains on the surface of solid Earth indefinitely due to its low density, hence continents increased in volumes to cover about 30% of the Earth's surface over time. However, recent studies on the accretion history of continents reveals that at least 80% of the granite that ever formed had been subducted into the deep mantle to form “second continents” at the mantle transition zone (410-660 km). These second continents would affect mantle dynamics in two ways. First, as the second continents are gravitationally stable at the depth of the mantle transition zone, they act as a barrier to descending cold slabs. The stagnation of cold slab would be partly due to the pre-existing second continents. Another effect of the second continents on mantle dynamics relates to their chemical component. Because granite is enriched with incompatible elements, including long-lived radiogenic elements K, Th, and U, the second continents act as heat sources in the mantle. In particular, the heat generation of the second continents is a key to understanding the formation-breakup cycle of supercontinents. Granite that piled up beneath a supercontinent during continent accretion would cause thermal instability to form a superplume beneath the supercontinent. A numerical study on the thermal evolution of subducted granite gives the characteristic time scale of thermal instability which is consistent with the lives of supercontinents suggested by geological studies.

著者

鈴木 敬治

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.97, no.4, pp.271-278, 1988-08-25 (Released:2011-02-17)

参考文献数

13

被引用文献数

3 2

著者

小野 有五

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.121, no.2, pp.187-214, 2012-04-25 (Released:2012-05-29)

参考文献数

133

被引用文献数

1 4

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Fifty years of studies on glacial landforms in Japan between 1960 and 2010 are reviewed from the personal perspective of a researcher who devoted a major part of his life to these studies. The 1960s was a period in which there was a paradigm shift in the history of glacial landform studies in Japan. This resulted from a series of studies by Tomoya Iozawa using aerial photograph interpretation. He was the first researcher to observe and identify all of the glacial landforms in Japan using aerial photographs, and divided them into two groups: the older and more widespread (Yokoo Stage) and the younger and much less widespread (Karasawa Stage). Following his methodology and staging, extensive research was done in the 1970s, and tephrochronological studies revealed that the older and younger stages correspond to MIS 4 and 2 respectively, although MIS 3 glaciation was recognized later in the Hidaka Range, Hokkaido. A researchers union of glacial and periglacial landforms called Kanrei-chikei Danwakai was established in 1972, Proposed and organized by Isozawa and other young students including the author, it stimulated research. In the 1980s, a reconstruction of the mass balance and flows of past glaciers from glacial landforms was attempted by the author and other researchers. This led to the estimation of the Equilibrium Line Altitude (ELA) of former glaciers in Japan. Inventory work and monitoring of perennial snow patches in the Japanese Alps were also begun in the 1980s, and they encouraged studies on the transformation from perennial snow patch to glacier. In addition, the discovery of an ice body at the bottom of Kuranosuke Cirque, Mt. Tateyama, Northern Japanese Alps gave an important hint to estimating the present (topographical) snowline altitude, which could be much lower than the former evaluation determined only from free air temperature. Both the study of perennial snow patches and mapping of the former ELA clarified the importance of precipitation when determining snowline altitude, and the present ELA was estimated at 2970 m just below the peak of Mt. Tateyama (3003 m). Since the 1990s, glacial landform studies became more closely related to global climatic change within the framework of IGBP-PAGES. Glacial fluctuations in Japan in the last glacial period were mainly controlled by monsoon changes and migration of westerlies, which caused a southern migration of the polar frontal zone. Although the glaciers in Japan were small, even in the glacial period, it is now believed that they are an important indicator of climatic changes because they are very sensitive to monsoon and westerly changes.

著者

藤井 昭二 奈良 正義 畑中 盛 山口 吾一郎 堀内 一穂 奈須 紀幸 竹内 貞子 吉田 明弘 能城 修一 鈴木 三男 邑本 順亮

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.113, no.3, pp.415-420, 2004-04-25 (Released:2009-11-12)

参考文献数

14

被引用文献数

1 1

著者

鈴木 康弘 堤 浩之 渡辺 満久 植木 岳雪 奥村 晃史 後藤 秀昭 Mihail I STRELTSOV Andrei I KOZHURIN Rustam BULGAKOV Nikolai TERENTIEF Alexei I IVASHCHENKO

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.109, no.2, pp.311-317, 2000-04-25 (Released:2010-11-18)

参考文献数

12

被引用文献数

3 4

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We have prepared a preliminary active fault map of Sakhalin, Russia, based on an interpretation of aerial photographs and satellite images. Major active structures include 110-km-long active faults along the western margin of the Yuzhno-Sakhalinsk Lowland in southern Sakhalin and 120-km-long active faults along the western margin of the Poronaysk Lowland in central Sakhalin. These active faults are parallel to but are located as far as 10 km east of the Tym-Poronaysk fault. Geomorphic surfaces on the upthrown side of the fault are tilting westward, therefore, the faults are considered to be west-dipping low-angle reverse faults. The vertical component of slip rates of these faults are >0.3 mm/yr in southern Sakhalin and 1.0-1.5 mm/yr in central Sakhalin. The net-slip rates could be much greater because the faults are low-angle reverse faults. If these faults rupture along their entire length during individual earthquakes, the earthquakes could be as great as M7.6-7.7. In northern Sakhalin, we have identified a series of right-lateral strike-slip faults, including the 1995 Neftegorsk earthquake fault. The slip rates for these faults are estimated at 4 mm/yr. The right-lateral shear in northern Sakhalin and east-west compression in central and southern Sakhalin may reflect relative plate motion in far-east Asian region.

著者

吉田 英嗣

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.124, no.4, pp.575-586, 2015-08-25 (Released:2015-09-17)

参考文献数

36

被引用文献数

1 1

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Hummocks are conically shaped mounds, which occur following catastrophic sector collapses, and are mainly observed around volcanoes. Empirical relationships of hummocks proposed by Yoshida et al. (2012) are basically applicable if hummocks now distributed on a debris avalanche depositional area do not have remarkable disturbances due to topographical barriers or modifications after deposition. Using these empirical relationships, the Old Yotei volcano, whose mega-collapse in the Late Pleistocene has not been clarified yet, is examined. The results show that the size-distance relationship of hummocks (N=297), distributed west of the volcano can be expressed by an exponential function as,   A=α exp (−β D),where A is the average area of a hummock within a certain span and D is the average distance from the source. For the Old Yotei volcano, the values of coefficients α and β of the fitted curve are 170286.4 and 0.000429, respectively. Based on a geomorphological interpretation of both α and β values, it can be concluded that the collapse volume of the Old Yotei volcano is ca.1.3 km3, and the equivalent coefficient of friction of the debris avalanche is 0.129. The latter also reveals a high probability that the pre-collapse summit of the Old Yotei volcano reached 1700 m a.s.l. Thus, the image of the flank collapse of the Old Yotei volcano has been restored more decisively by the distribution of hummocks.

著者

淺香 幸雄

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.46, no.6, pp.292a-295, 1934-06-15 (Released:2010-10-13)

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.19, no.7, pp.513-513, 1907-07-15 (Released:2010-12-22)

著者

小野 昭

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.111, no.6, pp.840-848, 2002-12-25 (Released:2009-11-12)

参考文献数

18

被引用文献数

1 1

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A framework of climatic changes and archaeological chronologies during the Last Glacial is discussed with particular reference to the correlation among MIS stages, GISP2 ice core oscillation, and calibrated radiocarbon dates from palaeolithic sites in Rhineland, Germany as one of the most intensively studied areas in Central Europe. Although the fine chronologies have been set up in the last decade, an analysis of a concrete example of a palaeollithic site is needed when hominid adaptation in the Last Glacial has to be discussed. This paper focuses on the subsistence of a late Magdalenian Gennersdorf settlement in the oldest Dryas period. Excavations have revealed two large houses, one big hut, and two small huts. Archaeological features that have been well preserved made it possible to set out a hypothesis that the large house was repeatedly used every winter and the small huts were used in summer by different human groups, in relation to the lithic raw material, procurement systems. Hominids of the late Palaeolithic period were characterized by having developed a subsistence system for the all round adaptive procurement of environmental conditions through seasonal migrations.

著者

川本 竜彦

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.124, no.3, pp.473-501, 2015-06-25 (Released:2015-07-10)

参考文献数

165

被引用文献数

2 2

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Subduction-zone magmatism is triggered by the addition of H2O-rich slab-derived flux: aqueous fluids, hydrous partial melts or supercritical fluids from the subducting slab through reactions. Whether the slab-derived flux is an aqueous fluid, a partial melt, or a supercritical fluid remains an open question. In general, with increasing pressure, aqueous fluids dissolve more silicate components and silicate melts dissolve more H2O. Under low-pressure conditions, those aqueous fluids and hydrous silicate melts remain isolated phases due to the miscibility gap. As pressure increases, the miscibility gap disappears and the two liquid phases becomes one phase. This vanishing point is regarded as critical end point or second critical end point. X-ray radiography experiments locate the pressure of the second critical end point at 2.5 GPa (83 km depth) and 700°C for sediment-H2O, and at 2.8 GPa (92 km depth) and 750°C for high-Mg andesite (HMA)-H2O. These depths correspond to the depth range of a subducted oceanic plate beneath volcanic arcs. Sediment-derived supercritical fluids, which are fed to the mantle wedge from the subducting slab, may react with the mantle peridotite to form HMA supercritical fluids due to peritectic reaction between silica-rich fluids and olivine-rich mantle peridotite. Such HMA supercritical fluids may separate into aqueous fluids and HMA melts at 92 km depth during ascent. HMA magmas can be erupted as they are, if the HMA melts segregate without reacting to the overriding peridotite. Partitioning behaviors between aqueous fluids and melts are determined with and without (Na, K) Cl using synchrotron X-ray fluorescence. The data indicate that highly saline fluids effectively transfer large-ion lithophile elements. If the slab-derived supercritical fluids contain Cl and subsequently separate into aqueous fluids and melts in the mantle wedge, then such aqueous fluids inherit much more Cl and also more or less amounts of large ion lithophile elements than the coexisting melts. In contrast, Cl-free aqueous fluids can not effectively transfer Pb and alkali earth elements to the magma source. Enrichment of some large-ion lithophile elements in arc basalts relative to mid-oceanic ridge basalts has been attributed to mantle source fertilization by such aqueous fluids from a dehydrating oceanic plate. Such aqueous fluids are likely to contain Cl, although the amount remains to be quantified. If such silica-rich magmas survive as andesitic melts under a limited reaction with mantle minerals, they may erupt as HMA magmas having slab-derived signatures.

著者

高井 研 稲垣 史生

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.112, no.2, pp.234-249, 2003-04-25 (Released:2009-11-12)

参考文献数

82

被引用文献数

5 2

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Seafloor hydrothermal system and deep subsurface are of great interest for microbiologists as paradise of unusual lives so-called “Extremophiles” in this planet. Such peculiar microorganisms have been believed to be minority in the earth throughout the long history after the early evolution of life. Recent investigations for microorganisms present in the active hydrothermal seafloor and subsurface have revolutionized the concept. Ubiquity, predominance and diversity of extremophiles in the present and past global environments signify the unresolved, but significant role in the co-evolution of earth and life. In this article, we summarize the expeditions for the microbial world in the seafloor hydrothermal system and deep subsurface and shed light on the foci of the future investigation.

著者

早川 由紀夫 新井 房夫 北爪 智啓

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.106, no.5, pp.660-664, 1997-10-25 (Released:2009-11-12)

参考文献数

10

被引用文献数

1

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The Edifice of Hiuchi Volcano was founded on the Mokake ignimbrite plateau which is directly underlain by the Nanairi pumice. They erupted from near the present summit successively about 350ka. On the plateau, the Ozorizawa cone was first established about 100 ka. Next, the Shibayasugura cone having twin peaks, Shibayasugura (2, 356 m) and Manaitagura (2, 346 m), was built shifting slightly southeast. At 19ka, the Jubeike lava flow and Kumazawa Tashiro lava dome were issued from the northeastern flanks. The latter was accompanied by a devastating blast. Southward-opening horseshoe depression is source of the Nushiri debris avalanche, which dammed up the Nushiri River and formed the Oze marsh about 8ka. The Akanagure lava dome and flows immediately occupied the depression. The youngest volcanic feature at Hiuchi is the Miike lava dome, 300m south of the Manaitagura peak. It emplaced during the 16th century, just before the Shirohikemizu flood descended the Hinoemata River on July 28, 1544. Hiuchi Volcano has erupted 17 × 1012 kg of magma since its birth, 350 thousand years ago. Average discharge rate is 4.9 × 1010 kg per thousand years, an order of magnitude smaller than that of the most active Japanese volcanoes.

著者

本多 啓太 須貝 俊彦

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.119, no.5, pp.924-933, 2010-10-25 (Released:2011-01-21)

参考文献数

82

被引用文献数

3 3

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In warm-humid and tectonically active regions such as Japan it is important to investigate the geomorphic development of recent alluvial plains controlled by sea-level changes to prevent natural disasters. This is because human activities concentrate coastal alluvial plains composed of unconsolidated soft sediments (alluvium) including inner-bay mud, which amplify seismic intensity. However, we know little about the general shape of the alluvium quantitatively although several river basins have been investigated in detail. We selected 33 trunk rivers throughout Japan and measured the Present River long-Profile (PRP) along with the Last Glacial River long-Profile (LGRP) defined by the depositional surface of basal gravel layers formed under the influence of falling sealevels during the last glacial period. The thickness of the alluvium given by the relative altitude between PRP and LGRP was basically in proportion to the size of the river basin, and it decreased linearly upstream with the exception of several rivers such as Shinano, Kiso, Oita, and Yoshino. Along these rivers, the alluvium is markedly thicker than expected probably because of tectonic subsidence occurring repetitively after formation of basal gravel layers. This implies that the fluvial response to sea-level change is sensitive enough to distinguish the effects of the accumulation of tectonic movements after deposition of basal gravels. In stable or slightly uplifted areas, the inland distribution of inner-bay mud is basically controlled by river basin size.

著者

宮縁 育夫

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.125, no.3, pp.421-429, 2016

被引用文献数

18

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The Kumamoto earthquake(Mj7.3) on April 16, 2016 triggered numerous landslides in and around Minamiaso Village, which is located at the western part of Aso caldera, southwestern Japan. The landslides were divided into two types:landslides occurring at steep caldera walls and landslides generated on the slopes of post-caldera central cones of Aso Volcano. Several landslides occurred on slopes steeper than 25°at the northwestern to western caldera walls, which comprise pre-Aso volcanic rocks (lavas and pyroclastics). The largest landslide (ca. 300m high, 130-200m wide) occurred on the western caldera wall, damaging National Route 57 and the Hohi line of the Japan Railway. Because a clear rupture surface could not be observed, unstable blocks which had been divided by cracks, were likely to collapse due to the intense earthquake on April 16. At the post-caldera central cones of Aso Volcano, earthquake-induced landslides were generated not only on steep slopes but also on slopes gentler than 10°. They occurred in unconsolidated superficial tephra deposits overlying lavas and agglutinates, and the thickness of the slides usually ranged from 4 to 8 m. The sliding masses traveled long distances (<600m), compared to small differences in elevation. The deposits were composed of tephra blocks of a few meters and there was no evidence that they were transported by water. These facts suggest that some landslides mobilized rapidly into debris avalanches, traveling a few hundred meters. The associated debris avalanche resulted in five casualties and severe damage to houses at the foot of the Takanoobane lava dome. The characteristics of the April 16, 2016 earthquake-induced landslides differ from those of rainfall-induced landslides in July 2012, June 2001, and July 1990 at Aso Volcano, and provide important imformation for preventing or mitigating future landslide disasters in the Aso caldera region.

著者

吉川 清志

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.99, no.7, pp.743-758, 1990-12-25 (Released:2009-11-12)

参考文献数

32

被引用文献数

9 17

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Inductively coupled plasma emission spectrometry (ICP) is applied for the chemical analyses of volcanic glasses to improve the efficiency of identification of widespread tephra.The differences of specific gravity and magnetic property among glass and minerals are effective for purification.The ICP method is very useful for routine analyses. The values of chemical analysis by the ICP are close to the EPMA data. The reproducibility is exellent, while fluctuation coefficients of most elements of tephra are about 5 %. Good correlations are found between the sum of major elements except of SiO2 and the refractivity of glass, and between the Fe/Mg ratio and the refractivity of orthopyroxene.Unique tephra in middle Pleistocene can be classified into two different groups of tephra by their minor elements Y and MnO. Tephra in north eastern Hokkaido are mainly came from two sources, which can not be distinguished in the field. The contents of incompatible elements of two types of tephra are clearly different. The source regions of Pliocene to Pleistocene tephra in Tokai and Kinki area can be estimated by the regional characteristics of their chemical compositions. The ICP method is also successfully applied for identification of submarine tephra in eastern Japan Sea, and correlation of sediments of Kanto to Kyushu areas and discovery of source of some widespread tephra in early to middle Pleistocene.

著者

吉村 稔

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.102, no.2, pp.131-143, 1993-04-25 (Released:2010-11-18)

参考文献数

12

被引用文献数

4 14

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In order to reconstruct the march of climate before instrumental observations in Japan, Historical Weather Data Base has been constructed. Weather descriptions in historical documents, such as official diaries of Feudal Clans in Edo Era, or of local offices in each clan, are objects of the data base. Other descriptions are in those diaries of large temples, large shrines and large farmers, and in some of private diaries Considering the description of weather phenomena in old diaries, they were grouped into 13 weather conditions In this data base, “weather range” means weather conditions in a day. A rough tendency of the weather in a day (HN), or remarkable conditions such as hot, cold, dry and wet (HT), are also important to understand weather conditions for each day. Accompanied phenomena (TK) and wind conditions (KT, TT, KH) are also objects to encode. Daily weather records for the years from 1700 to 1889 are mainly under collections. So far, more than 2, 500 years weather records have been inputted in the daily data base. The main files of the system are PC-DA (paleo climatic data), and PC-REC (paleo climatic record). The former consists of encoded weather data which will be used chiefly to retrieve weather conditions and to draw maps or to make tables. The latter contains weather descriptions in each day with Katakana, one of the Japanese characters. This will support detailed investigationAs an index of wet or dry condition for each month, “PI” is proposed. Weather conditions having some relations with precipitation are grouped to three kinds. Monthly frequencies of each type are multiplied by constants. These are 1 for “little rain”, 2 for “rain” and 5 for “much rain”. The total value in each month in each day is “PI”, which is useful for the comparison within the same daily series. The scatter diagrams of PI in Kokura Kita Kyushu City and Precipitation at Moji for each season are shown in Fig. 4. Time series of PI in 6 cities show the existence of different march in summer precipitations over Japan (Fig. 5). The monthly conditions in summer months from 1781 to 1789 are reconstructed in Fig. 6.

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.

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.103, no.6, pp.719a-719a, 1994-12-10 (Released:2009-11-12)