著者

杉原 重夫

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.107, no.3, pp.390-420, 1998-06-25 (Released:2009-11-12)

参考文献数

40

被引用文献数

1 3 1

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Hachijojima, one of the Izu Islands, is located on the Volcanic front of the Izu-Ogasawara (Bonin) Arc which lies south to north along the boundary of the Pacific plate and the Philippine Sea Plate. Hachijojima consists of two stratovolcanoes : Higashiyama and Nishiyama. There is a sharp contrast between Higahshiyama, which is a well-dissected mountain, and Nishiyama, which is cone-shaped. It is topographically clear that Higashiyama was formed earlier than Nishiyama. The following is a summary of the results of this study.1) The eruptive history of Higashiyama can be divided into six ages : Sokodo I (40-50 ka), Sokodo II (ca. 25-33 ka), Sueyoshi (ca. 17-25 ka), Nakanogo I (ca. 11-17 ka), Nakanogo II (ca. 5.8-11) and Mitsune (ca. 5.8 ka and later).2) At Higashiyama, a large amount of dacitic magma erupted in the Sokodo I Age and the Sueyoshi Age, and formed a caldera. In the Sokodo I age, the early stratovolcanoes were subjected to landslides and collapsed, and the Higashiyama caldera emarged. In the Sueyoshi Age, the summit of Higashiyama stratovolcanoes were subject to landslides and collapsed to form the Nishihakuunzan caldera.3) the Higashiyama stratovolcano (young stratovolcano I) was formed in the Sokodo II Age and Mihara stratovolcano (young stratovolcano II a, b) in the Nakanogo I Age by eruptions of basalt and andesite magma.4) Higashiyama formed a central cone at the end of Nakanogo I Age and eruptions from the summit ended around ca. II ka. Thereafter, it transformed into a flank eruption which issued andesite magma in the Nakanogo II age. In the Mitsune age, volcanic activities of Higashiyama receded.5) In the Nishiyama region, eruptions became active from the Nakanogo I Age and issued mainly basaltic tephra and pyroclastic surges. However, dacitic tephra was also issued. Occasional finding of pumice fall deposit suggest the generation of daciticmagma.6) On Higashiyama, deposits Aira-Tn ash (ca. 24.5 ka) and Kikai-Akahoya ash (ca. 6.3 ka) were transported by westerlies from the Kyusyu area. They prove to be important marker tephras clarifing the tephra stratigraphy and eruptive history in this region.

著者

山田 俊弘 矢島 道子 須貝 俊彦 島津 俊之

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.132, no.3, pp.217-230, 2023-06-25 (Released:2023-07-07)

参考文献数

41

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The historiography of geoscience in the 20th century in Japan is reconsidered through 57 volumes of diaries (1914-1963) of Mochizuki Katsumi (1905-1963), a geology professor at Shizuoka University, from the following four viewpoints: 1) Scientific thought of geotectonics: Considering Mochizuki's own theory of geotectonics from his relations with other researchers such as Otuka Yanosuke (1903-1950), professor at the Earthquake Research Institute and the Faculty of Science of the Imperial University of Tokyo; 2) Mutual relationship between geology and geography: Tracing Mochizuki's teachings and research in the two disciplines at the higher schools of Kanazawa and Shizuoka; 3) History of geoscience education: Illustrating the transition of ‘geoscience’ including human geography, from the World War II era to the post-war period; 4) The life history of a scientist: Positioning a personal history, which records details of educational reforms in the history of universities and cultural history of Japan.

著者

高岡 貞夫

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.122, no.6, pp.1020-1038, 2013-12-25 (Released:2014-01-16)

参考文献数

92

被引用文献数

4 4

---

This paper overviews changes in land use and fauna over the past ca. 100 years in and around Tokyo Metropolis. Rapid changes in fauna occurred during the second half of the last century with urbanization. The faunal changes were caused by habitat destruction due to exploitation, habitat change due to urban warming, regime changes in natural and anthropogenic disturbances, and the invasion of alien species. Although a rapid decline of native species diversity occurred during the period, some species have reinvaded or newly invaded urban and suburban areas in the last few decades. Some alien species have also invaded the built environment such as artificial coasts and abandoned coppice forests. Faunal changes continued even after the rapid environmental changes in the last century. Continuous monitoring is needed to detect further faunal changes in the Tokyo area.

著者

巽 好幸 末永 伸明 吉岡 祥一 金子 克哉

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.130, no.4, pp.585-597, 2021-08-25 (Released:2021-09-23)

参考文献数

58

被引用文献数

2 2

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Water circulation, along with plate subduction, is considered based on the stabilities of hydrous phases and pressure–temperature profiles of the sinking oceanic plate. Water in a rather hot slab like the present one may be largely liberated at shallow depths (< 150 km) and return to the ocean via. arc magmatism. On the other hand, stabilization of dense hydrous minerals under cooler conditions, which current subduction zones will soon experience, causes the transportation or reflux of seawater to the deep mantle, which reduces the total mass of surface seawater. Simple calculations accepting water contents in the subducting slab suggested by a recent seismic velocity structure model indicate that the Earth's oceans are likely to disappear ∼80 million years hence. Significant changes may happen such as the end of plate tectonics and the onset of snowball Earth, with associated catastrophes affecting life. The only way to confirm this picture of the future of the ocean planet Earth is to examine deep hydration taking place along the outer rise through direct analyses of the upper mantle across the Moho.

著者

石村 大輔

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.122, no.3, pp.448-471, 2013-06-25 (Released:2013-07-08)

参考文献数

74

被引用文献数

1 3

---

Fluvial and marine terraces have been used as geomorphic indicators to reconstruct the paleoenvironment and estimate crustal movements. This study focuses on the west coast of Ise Bay, where fluvial terraces are widely distributed and active faults have developed. The region is located far from active volcanoes; therefore, terrace chronology and processes of terrace formation during the late Quaternary have been poorly established. This study applies a tephra analysis of aeolian deposits covering terrace surfaces to identify invisible tephra horizons, and discusses the chronology and processes of terrace formation. Furthermore, it estimates crustal movements during the late Quaternary using altitudes of climatic terrace surfaces and data on subsurface geology. The tephra analysis identifies widespread tephras such as Kikai-Akahoya tephra (K-Ah: 7.3 ka) and Aira-Tn tephra (AT: 26–29 ka) from aeolian deposits. Whether or not Kikai-Tozurahara tephra (K-Tz: 95 ka) covered terrace surfaces is assessed from the existence of β-quartz. Based on these tephras and geomorphic features, it is deduced that terrace formation in the study area corresponds to climate changes. In particular, L2 and Md1 terraces that formed during Marine Isotope Stage (MIS) 2 and MIS 5e are important landforms for discussing the processes of terrace formation in response to climate changes. The process of L2 terrace formation indicates that a decrease in precipitation is a major factor of terrace formation upstream during glacial periods. Uplift and subsidence rates during the late Quaternary are estimated not only along active faults but also in areas remote from them. The distribution of uplift and subsidence is consistent with geomorphic and geologic features. This implies that movements of active faults greatly affected geomorphic and geologic development in the study area since they began to move. Based on uplift and subsidence rates across the faults, vertical slip rates of the Yoro, Kuwana, and Yokkaichi faults are estimated at > 1.7 mm/yr, 1.0–1.2 mm/yr, and 0.5 mm/yr, respectively.

著者

守屋 以智雄

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.123, no.1, pp.89-122, 2014-02-25 (Released:2014-03-07)

参考文献数

43

被引用文献数

5 5

---

The evolution of 84 volcanoes in the Philippines is outlined geomorphologically on the basis of interpretations of volcanic landforms using aerial photographs, topographic maps, satellite images, and geomorphological and geological field surveys. Fifty-six stratovolcanoes, three caldera, three lava domes, four scoria cones, four lava fields, and 10 shield volcanoes are identified. Large basaltic volcanoes such as lava fields and shield volcanoes were found unexpectedly in subduction zones. No lava field or shield volcano has been discovered on the Japanese Islands. Among the 34 subduction zones in the world, 19 do not have lava fields or shield volcanoes. Two oblique subduction zones form the Philippine Fault Zone. The fault zone mostly coincides with the eastern volcanic zone. At the southwestern part of Mindanao Island, a volcanic chain, consisting of Bulibu, Basilan, and Cagayan Sulu lava fields, Balatukan, Mangabon, Katangrad, Kalatungan, Makaturing, Bacolod, and Pagayawan shield volcanoes, and Pagadian lava domes (monogenetic volcanoes) trends northeast-southwest, in parallel with the trenches and main arcs. The association of the volcanoes with the trenches and arcs suggests that the volcanic chain is a marginal sea ridge between Sulu Sea and Celebes Sea and that the back-arc basin ridge might have extended under Mindanao Island from Moro Gulf to the northern part of Mindanao Island.

著者

柳田 誠 藤原 治 後藤 憲央 佐々木 俊法

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.113, no.6, pp.835-847, 2004-12-25 (Released:2009-11-12)

参考文献数

22

被引用文献数

5 4

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The authors re-examine conventionally used terms for hills on the basis of a morphometric study of landforms in Japan. Relative relief and drainage density are calculated for every 250 m grid on topographic maps.Figure 2 shows relative relief on the vertical axis and drainage density on the horizontal axis. Hills are clearly delineated from mountains by these parameters. The relative relief for hills is smaller than 110 m120 m, and the drainage density is greater than 4050 streams/km2. The Shiranuka Hills in Hokkaido should more appropriately be called the Shiranuka Mountains, because of their high mean relative relief (134.3 m) and lower drainage density.Figure 2 also indicates a possible subdivision of hills into 2 types, or 'flat topped hills' with a relative relief of less than 60 m, and 'ridge hills' with a relative relief of 60 m 120 m. The standard deviation of relief energy can also be taken as a criterion to distinguish the 2 types of hill, namely, the flat topped hills have a standard deviation of 8.120.6, in contrast to the ridge hills, which have a standard deviation of 21.029.8.The drainage density generally increases corresponding to the length of time through which terraces are transformed into hills and the amount of uplift. Therefore, hills have greater drainage density than terraces. But, it is worthy of note that the drainage density is never greater than 7080 streams/km2. The greatest density is found in the Oku-Noto Hills, one of the ridge hills 480, 000780, 000 years old. Indications are that the development of a drainage system culminates at some stage between flat-topped hills and ridge hills, and then valleys are gradually unified, resulting in a lower drainage density.Both flat-topped hills and ridge hills may be derived from various origins such as terraces, depositional surfaces of pyroclastic flows, dissected Tertiary or early Quaternary soft rocks, or degradation of mountains with medium relief. But, the formation of ridge hills requires a greater speed of uplift, and rocks that are hard enough to sustain steep slopes with a relative relief of 80 m120 m. The conditions being the same, ridge hills are older than flat-topped hills.

著者

長沼 佐枝 荒井 良雄

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.121, no.6, pp.1030-1042, 2012-12-25 (Released:2013-01-07)

参考文献数

24

被引用文献数

1 1

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Seaside-Momochi, now an affluent residential area in the waterfront district of Fukuoka City, Kyusyu, Japan, was originally designed for middle-class inhabitants. This paper examines why the government of Fukuoka City changed the original concept of the residential development plan for Seaside-Momochi to cater for higher-income households. At the initial stages of the planning process in 1984, the Fukuoka City government focused on the welfare of middle-class inhabitants. However, the government found it difficult to find buyers for the land due to a decrease in housing demand among the middle class, and the project was in danger of stalling. A few years later, land prices in the city rose in the context of a property boom. This suddenly increased the development potential of the Seaside-Momochi area, and several private housing companies became interested in the Seaside-Momochi development project. However, the companies joining the project proposed modifying the original development plan to focus more on attracting affluent buyers. Despite this being a departure from its original intentions, the Fukuoka City government decided to alter the plan in order to avoid losing the development plan. The government modified the original plans and land-sale strategies. This resulted in a development plan that focused not on middle-class inhabitants but on higher income households.

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.17, no.8, pp.601, 1905-08-15 (Released:2010-12-22)

著者

小林 貞一

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.87, no.5, pp.274-275, 1978-10-25 (Released:2009-11-12)

著者

早坂 一郎

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.61, no.4, pp.154-156, 1953-01-30 (Released:2009-11-12)

参考文献数

1

著者

小林 貞一

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.95, no.2, pp.143-144, 1986-04-25 (Released:2009-11-12)

著者

松川 正樹

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.130, no.5, pp.653-681, 2021-10-25 (Released:2021-11-17)

参考文献数

90

---

The Tetori Group comprises significant Mesozoic (middle Jurassic–early Cretaceous) marine and terrestrial strata in East Asia. A facies analysis of the group is conducted to reveal the development of the Tetori sedimentary basin. The Tetori Group in the Mt. Hakusan Region is mainly distributed in three areas: the Kuzuryugawa Area in Fukui Prefecture and the Shiramine and Shokawa districts in the Hakusan Area in Ishikawa and Gifu prefectures. Seven lithofacies associations are recognized, which represent the deposition in talus and proximal alluvial fan, gravelly braided river and alluvial fan, sandy braided river, lacustrine delta, estuarine, shoreface, and inner shelf environments. Based on the characters and spatio-temporal distribution of these lithofacies associations across the basin in the three areas, the group is interpreted to have developed in four stages. Stage 1 is represented by the lower part of the Tetori Group in the Kuzuryugawa Area in the southern part of the basin, and shows, in ascending order, talus and proximal alluvial fans, inner shelf, shoreface, and alluvial fan facies. Stage 2 represents the lower middle part of the group in the Shokawa District in the northeastern part of the basin, and shows a change from estuarine, shoreface to inner shelf, and back to shoreface facies. Stage 3 is recognized in the middle part of the group in both the Shiramine and Shokawa districts in the northwestern and northeastern parts of the basin, respectively. Stage 3 was initially formed as talus and proximal alluvial fan, gravelly braided river and alluvial fan, and sandy braided river facies, and was later changed to lacustrine delta, sandy braided river, and gravelly braided river and alluvial fan facies, and back to lacustrine delta and sandy braided river facies in ascending order in the Shiramine District, and was initially formed as estuary and shoreface facies, and was later changed to estuary, lacustrine delta and sandy braided river facies in ascending order in the Shokawa District. Stage 4 is represented by the upper part of the group in all three areas, and shows talus and alluvial fan, gravelly braided river and alluvial fan, and sandy braided river facies. The Tetori basin reflects an upheaval of the basin forming an inter-mountain basin. This supports the hypothesis of a juxtaposition of late Jurassic to earliest Cretaceous accretionary complexes along the eastern margin of the Asia continent during the Hauterivian (Early Cretaceous).

著者

田近 英一

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.1, pp.79-94, 2007-02-25 (Released:2009-11-12)

参考文献数

86

被引用文献数

1

---

Liquid water on the surface of the Earth might have frozen entirely at least 3 times during the history of the Earth (650 Ma, 700 Ma, and 2.2 Ga). Assuming such extreme conditions, the snowball Earth hypothesis explains several unusual geological features associated with glacial deposits in the Proterozoic glaciations. Life should, however, have faced serious crises during these glaciations because liquid water is necessary for life. In particular, survival of photosynthetic algae, which are supposed to have appeared before the Neoproterozoic glaciations, might have been difficult if the surface water froze completely. There would have been refugia for life during the global glaciations. Life could have survived if the equatorial ocean was not completely frozen (soft-snowball condition), or equatorial sea ice might have been very thin (on the order of 10 meters). Even if these conditions were not achieved, life could have survived in shallow hot springs around volcanic islands. It would be much more difficult for eumetazoa to survive such severe conditions if they appeared before the Neoproterozoic glaciations as suggested by molecular clock studies. The appearance of eumetazoa after the last global glaciation (Marinoan glaciation), as suggested by the paleontological record, however, avoids this problem.

著者

長井 雅史 小林 哲夫

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.1, pp.65-99, 2015-02-25 (Released:2015-03-11)

参考文献数

43

被引用文献数

10 11

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Ioto (Iwo-Jima; Sulphur Island) is a volcanic island located at the volcanic front of the Izu-Bonin arc about 1250 km south of Tokyo. The island consists of a central cone and southwest rim of a submarine caldera with a diameter of about 10 km. The rocks of the volcano are trachyandesite and trachyte, which are seldom found at a volcanic front. High rates of geothermal activity and crustal uplift have been observed, which are considered to be related to magma intruding at a shallow depth. Therefore, Ioto volcano is considered to be an active resurgent dome. However, eruptive history, including the process and timing of caldera formation, has not been clarified. Eruptive history based on our recent field survey, dating, and chemical analysis is as follows. A pre-caldera edifice was formed by volcanic activity of trachyandesite-trachyte magma in a subaerial and subaqueous environment. The magma composition and types of eruption were similar to those of the post-caldera edifice. It is still unclear when the caldera was formed. The caldera floor, which was a sedimentary basin with shallow marine sediments and a subaqueous lava flow, has been present at least since 2.7 cal kBP. Furthermore, a small volcanic island covered with trees used to exist in the Motoyama area. The complicated sequence of the Motoyama 2.7 cal kBP eruption is described as follows. First, on the volcanic island or in the surrounding shallow water, an explosive phreatomagmatic eruption occurred that formed subaqueous welded tuff (Hinodehama ignimbrite) and a subsequent thick subaqueous lava flow (Motoyama lava). While the Motoyama lava was still hot, the eastern part collapsed. The collapsed mass was quenched to form large blocks similar to pillow lava. A subsequent large phreatomagmatic eruption occurred, destroying the hot Motoyama lava, the older edifice, and the marine sediment. The resultant subaqueous pyroclastic flow generated the Motoyama pyroclastic deposit. Then, the eruption center shifted to the Suribachiyama area, which is just outside the southwest caldera rim. Deposits from three different eruption periods have been identified—lower, middle, and upper pyroclastic deposits—and a lava flow that erupted during the middle pyroclastic period. The lower unit was formed by a subaqueous eruption at a deeper level; the middle deposit was formed by a phreatomagmatic explosion at a shallow depth; and, the following lava emission generated a lava island. The upper pyroclastic deposit was generated by a combination of phreatomagmatic and Strombolian eruptions. Although the ages of these eruptions are not obvious, the first phase of the eruption occurred during the period between 2.7 cal kBP and 0.8-0.5 kBP, which is estimated from the age of the upper marine terrace X (Kaizuka et al., 1983). The eruption of the upper deposit occurred before AD 1779 (ca. 0.2 kBP). The eruptive products described so far are covered with younger sediment from marine terraces and spits. Recently, small-scale deposits from phreatic explosions accompanied by geothermal and uplift activities have been found distributed throughout the island, but juvenile material has not been confirmed to exist in the products.

著者

片山 郁夫 平内 健一 中島 淳一

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.2, pp.205-223, 2010-04-25 (Released:2010-07-06)

参考文献数

70

被引用文献数

6 8 2

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Water is known to play important roles in earthquake generation and volcanic activity. Consequently, the presence of water and its heterogeneous distribution in subduction zones may contribute to the variability of subduction seismicity and arc magmatism. In this study, we infer water distribution, including aqueous fluids and hydrous minerals, based on the seismic tomography beneath Japan, and discuss subduction processes in terms of water circulation in subduction zones. Two distinct oceanic plates, the Pacific plate and Philippine Sea plate, are subducting beneath Japan. These plates have quite different characteristics. The Pacific plate is old (∼130 Ma) and is subducting beneath northeast Japan as rapidly as 10 cm/year. In contrast, the Philippine Sea plate is relatively young (∼20-50 Ma) and is subducting at ∼3-5 cm/year beneath southwest Japan. The subducting old Pacific plate results in cold environments beneath northeast Japan, whereas the thermal structure beneath southwest Japan is relatively warm as a result of the young Philippine Sea plate subduction. Most water is released by eclogite transformation in the subducting oceanic crust, and the expelled water infiltrates into the mantle wedge, forming hydrous minerals such as serpentine and chlorite. The seismic tomography beneath northeast Japan shows that eclogite transformation occurs at depths of ∼80-100 km, and above these depths, a low-velocity anomaly and high Vp/Vs are detected in the mantle wedge. In southwest Japan, eclogite transformation occurs at much shallower depths (50-60 km) due to a warm subduction geotherm. The down-dip limit of interplate seismicity is likely to be controlled by a brittle-ductile transition in southwest Japan, whereas such a limit beneath northeast Japan coincides with the low-velocity anomaly at depths of 60-70 km, suggesting that the presence of serpentine inhibits earthquake activity at the plate interface. The double plane of intraplate seismicity is probably caused by dehydration of eclogite forming reactions in the upper plane and serpentine/chlorite dehydration in the lower plane, although seismic activity is absent at the mantle wedge where water is released by serpentine breakdown. Low-frequency tremors above the Philippine Sea plate are mostly located at the interface between island arc Moho and subducting plate surface. Abundant aqueous fluids in this region due to permeability contrasts may trigger low-frequency tremors. A slab parallel low-velocity zone beneath northeast Japan is interpreted as a melt-filled upwelling flow in the mantle wedge. Such an anomaly is not detected in southwest Japan, and slab melting of the subducting Philippine Sea plate is probably the source of the arc magmatism in this region.

著者

今岡 照喜 永嶌 真理子

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.131, no.2, pp.235-256, 2022-04-25 (Released:2022-05-13)

参考文献数

98

被引用文献数

3

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The mineralogical characteristics of metasomatic Li-minerals in Iwagi Islet, sugilite, katayamalite, murakamiite, Li-rich pectolite, zektzerite, sogdianite and taeniolite are summarized. These Li-minerals occur in metasomatic albitite, which contains 500 ppm Li. Such a high-Li albitite content is unusual amongst metasomatic rocks in Setouchi Province of SW Japan. Albitite forms small bodies that are several tens of centimeters to tens of meters in size, and are disseminated in a host granite of Late Cretaceous age. It shows conspicuous strain-induced textures. Murakamiite and Li-rich pectolite form a solid solution with Li × 100/(Li + Na) atomic ratios ranging from 44.2 to 60.1, and Na line profiles show a zoning structure in which Na decreases from core to rim. Albitite-normalized element concentrations vary systematically with the ionic radius of the element; normalized concentrations of cations with the same valence roughly form a simple convex parabolic curve when plotted against the ionic radius. This indicates that the element partitioning of murakamiite and pectolite during metasomatism to form albitite took place under the strong control of a crystal structure, quasi-equilibrated with metasomatic fluids and coexisting minerals. The δ7Li values of murakamiite and Li-rich pectolite show a wide range from −9.1 to +0.4‰ (average −2.9‰), and no obvious correlation with Li content is observed. These δ7Li values should have resulted from hydrothermal fluid–rock interactions at temperatures of 300-600°C (hydrothermal stages). The very low δ7Li values down to −9.1‰ may have originated from intra-crystalline Li isotope diffusion, or involvement of deep-seated, Li–Na-enriched subduction-zone fluids with low δ7Li values. The occurrence of porous zircon, dalyite, and mantles of zektzerite and/or sogdianite on resorbed zircon in albitite suggests that those zirconium silicate minerals are the products of metasomatic mineral replacement reactions by dissolution–reprecipitation processes associated with Na-, K-, and Li-rich hydrothermal fluids.

著者

圦本 尚義

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.131, no.2, pp.163-177, 2022-04-25 (Released:2022-05-13)

参考文献数

71

被引用文献数

2

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Determining the elemental abundances of the Earth is one of the fundamental interests of the Earth and planetary sciences. The elemental abundances of the bulk solar system, chondrites and bulk Earth are reviewed. The elemental abundances of the bulk solar system resemble those of chondrites, with the exception of atmophile elements. CI chondrite may be most resemblant, but significant improvements in solar photosphere spectroscopy are necessary to reject other chondrites. Volatilities of elements control chemical variations among chondrites. These variations may reflect global thermal structures in the proto-solar disk. Alternatively, the variations may correspond to accretion ratios of chondrite-forming components, which are refractory inclusions, chondrules, and matrix, into the parent bodies. The elemental abundances of bulk silicate Earth can be empirically estimated without referring those of the bulk solar system and chondrites if we use chemical variations of mantle rocks. However, the chemical composition of bulk Earth remains largely uncertain because it is difficult to estimate the chemical compositions of the central core and the lower mantle without formation models of the Earth.

著者

阿部 和俊

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.123, no.2, pp.315-322, 2014-04-25 (Released:2014-05-16)

参考文献数

8

被引用文献数

6 4

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This paper evaluates the status of Tokyo among major cities of Japan and compares Tokyo with major cities of the world in terms of head and branch offices. First, the paper analyzes major cities of Japan from the standpoint of the head offices and branch offices of large private firms. The main focus of this analysis of Japan is the period from 1950 to 2010. Clearly, the largest number of head offices is found in Tokyo. This is followed by Osaka. However, it should be noted that in recent years, more and more firms have adopted the system of having multiple head offices. Including such firms, the number of private firms with head offices in Tokyo is steadily increasing. Tokyo houses the large number of branch offices, as well. As is the case for head offices, the city with the second largest number of branch offices is Osaka. The difference in status between Tokyo and other cities, particularly Osaka, has increased in recent times. The status of Tokyo has become more elevated with Osaka losing ground. Second, the paper compares the situation in Tokyo with major cities of Korea, France, the United Kingdom, Thailand, The United States of America, Germany, and India. Tokyo, Seoul, Paris, Bangkok, and London gravitate to the same category in that these capital cities are strong in terms of office locations. On the other hand, within The United States of America, Germany, and India, capital cities are not so strong in terms of numbers. The important factor affecting these results is the political system. Namely, in the cases of federated states, the status of capital cities is not as high. On the other hand, in the cases of non-federated states, the status of capital cities is very high.

著者

星埜 由尚

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.129, no.2, pp.227-240, 2020-04-25 (Released:2020-05-12)

参考文献数

23

被引用文献数

5 4

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The map of Japan drafted by Inoh Tadataka is considered to be the earliest produced from a scientific survey. The descriptions of longitude and latitude are based on astronomical observations, and Inoh's nationwide survey has been considered to be the origin of modern surveys in Japan. However, he did not succeed in determining longitude. Although he had knowledge of a spherical earth, the results of his survey were projected on a plane, not on a spherical surface. The parallels of latitude drawn on his maps are based on an accurate astronomical survey he carried out, but the meridians on his maps are absolutely inconsistent. His survey method also combined traverse and intersection surveys without control points. Therefore, his nationwide survey cannot be considered to be representative of a survey carried out in the modern period. There are many open traverse lines on his maps. These lines generally extend to temples and shrines, although they are not effective for improving the accuracy of the survey. Because temples and shrines might have been important public facilities at that time, the Tokugawa shogunate government probably requested information concerning their locations. He carried out a nationwide survey ten times, but he could not survey the northern half of Ezo island (Hokkaido). It is said that Mamiya Rinzo, who studied survey technology under Inoh Tadataka, surveyed Ezo island and submitted his survey data to Inoh Tadataka, therefore, Inoh's map of Ezo island might be entirely based on Mamiya's data. Further studies are necessary because Mamiya's survey has not been clarified.