著者

堤 之恭 沢田 輝 磯﨑 行雄

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.127, no.5, pp.723-734, 2018-10-25 (Released:2018-11-14)

参考文献数

47

被引用文献数

3 3

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Zircon is the only candidate of Hadean terrestrial material that can be collected because it can survive physically and chemically, as well as maintain its U–Pb age system during omnigenous geological events. However, Hadean zircons are rare, so many age analyses of zircons are required to isolate Hadean zircon grains. There are two ways to improve the analyses; decrease the time required for pre-analyzing processes and decrease the time required for age analysis. New equipment, high-voltage pulse power fragmentation device and automatic zircon pick-up system are effective for crushing rock sample and separating zircon grains, respectively, in a short time. Another potential age analysis, the 207Pb/206Pb age screening analysis, shows good performance in selecting old zircons quickly. Integrative operation of equipment and methods will result in successfully finding numerous Hadean zircons.

著者

道林 克禎

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.117, no.1, pp.93-109, 2008-02-25 (Released:2010-02-10)

参考文献数

74

被引用文献数

9 9

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Peridotites derived from the uppermost mantle consist dominantly of olivine and subsequently of pyroxene, spinel, garnet, and plagioclase. Crystal-plastic flow of mantle rocks results in various types of structure within peridotite being developed to varying degrees, depending upon the structure sensitivity of the different mineral phases. Plastic deformation leads to the simultaneous development of shape-preferred orientations and crystal-preferred orientations. A shape-preferred orientation is the expression of the average orientation of flattening (foliation) and elongation (lineation) directions, as defined by the orientations of individual grains. A crystal-preferred orientation (CPO) is the expression of crystallographic orientations of grains within the rock, as developed via dislocation creep and recrystallization. During intense homogeneous plastic deformation of a peridotite composed of minerals with a dominant slip system, the preferred orientation of the slip plane and slip direction tends to coincide with the plane of plastic flow and the flow direction, respectively. Recently, a new olivine CPO classification (A, B, C, D, and E types) has been proposed by Karato and co-workers to illustrate the roles of stress and water content as controlling factors of olivine slip systems. An additional CPO type (AG) has also been proposed in recognition of its common occurrence in nature. Given that olivine and the other constituent minerals in peridotites contain intrinsic elastic anisotropies, the development of CPO within peridotite during plastic deformation gives rise to seismic anisotropy in the upper mantle. Thus, the anisotropic properties of mantle rocks derived from the upper 100 km of the mantle, such as Ichinomegata peridotite xenoliths from the northeast Japan arc, have been calculated and applied with the aim of understanding the seismic anisotropy of the Earth's mantle.

著者

新谷 俊一 田中 和広

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.118, no.3, pp.340-349, 2009-06-25 (Released:2010-03-26)

参考文献数

20

被引用文献数

12 12

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Mud volcanoes are structures formed as a result of the emissions on a land surface or the sea floor of argillaceous material, which is composed of erupting remobilized mud, petroliferous or magmatic gases, and high-salinity water. Recently, large constructions have been planned deep underground besed on the expectation of geological stability. Therefore, it is important to study the origin of erupted mud and groundwater and the depths from which they ascend when evaluating long-term stability. Three active mud volcanoes and a passive mud volcano are found in the Tertiary Shiiya Formation distributed in Tokamachi City, southern part of Niigata Prefecture. Detailed descriptions of the mud volcanoes are provided by Shinya and Tanaka (2005). However, the origin of erupted mud and the formation mechanism of abnormal pore water pressure have not yet been identified. The authors measured the oxygen and hydrogen isotopic ratio of groundwater and vitrinite reflectance of coal fragments separated from erupted mud of an active mud volcano to investigate the origin of erupted mud, particularly the depth of the origin, and the formation mechanism of abnormal pore water pressure. As a result, δ18O and δD values of erupted water are 1.2‰, -5‰ respectively, showing good agreement with those of the Nanatani Formation distributed at a depth of 3400 m in depth in the studied area. Vitrinite reflectance (Ro) shows a bimodal distribution (i.e., 0.3-1.2% and 1.5-1.8%). Ro value of coal fragments sampled from the Shiiya Formation at the outcrop in the studied area are 0.3-0.45%. High Ro (1.5-1.8%) values of coal fragments are obtained in core samples at a depth of 4000 m in the Gimyo SK-1 oil well, which was excavated 2 km NW from the mud volcano. As a result of an investigation of erupted materials at the mud volcano, they were found to have originated at depths of from 3400 m to 4000 m in the studied area. Geothermal temperature of underground at depth of 3400 m to 4000 m in the in the studied area is estimated to be about 120°C to 150°C. Estimated temperature is high enough to cause diagenetic transition from smectite to illite. Transition from smectite to illite results in the release of a large volume of pore water into the sediment. It is concluded that dehydration due to mineral transition might be the major reason for abnormal pore water pressure formation at depths of 3500 m to 4000 m in the study area.

著者

増田 隆一

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.105, no.3, pp.354-363, 1996-06-25

参考文献数

29

被引用文献数

1

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The richness of fauna diversity is seen on the Japanese Islands, which range through 3, 000 km. When and from where have theanimals immigrated to Japan? Also, for understanding natural history of the Japanese Islands, it is very importantto investigate evolutinary history and origin of animals distributed on each island. While the evolutionary questions have been paleontologically and geologically examined so far, some of them are still unclear. Recent development of molecular phylogenetic study provides a reliable sight to understanding evolutionary history and origin of species. Advantageously, molecular study can analyze phylogeny of living species without fossil data.<BR>In Japan, two wildcats, the Iriomote cat and the Tsushima cat, live on the Iriomote Island and the Tsushima Island, respectively, where land bridges between the Asian continent and the Japanese Islands were present in the past time. To know evolution of these wildcats gives us useful information for better understanding of natural history of the Japanese Islands. Moreover, because both the wildcats are now endangered, it is now strongly needed to understand phylogenetic status of them for conservation and management. For the reason, we investigated molecular phylongeny of the two wildcats based on mitochondrial DNA sequences, and revealed that both the wildcats are very closely related to the leopard cat <I>Felis bengalensis</I>, which is widespread throughout Asia. Furthermore, from the DNA data, the Iriomote cat and the Tsushima cat were estimated to have diverged from the continental leopard cat approximately 200, 000 and 100, 000 years before present, respectively. The dates estimated by molecular data were in concordance with formation dates of the Ryukyu Arc and the Tsushima Island, respectively. These results suggest that geographic barrier has led fixation of some unique morphological characters into each cat population, while the two Japanese wildcats are still genetically close to the continental leopard cat.

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.49, no.9, pp.443, 1937-09-15 (Released:2010-12-22)

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.3, pp.Cover03_01-Cover03_02, 2022-06-25 (Released:2022-07-08)

参考文献数

2

---

西南日本から連続する中央構造線(MTL)は,群馬県西部下仁田地域を通過し,北側に領家帯の白亜紀花崗岩類や美濃・丹波帯(=足尾帯)のジュラ紀付加体が,南側に三波川帯の白亜紀高圧型片岩が広く露出する.MTLのすぐ南側には,低角度断層を介して三波川変成岩の上に特異な岩石・地層群がクリッペとして累重する.「跡倉クリッペ」はペルム紀花崗岩やホルンフェルス,非変成の白亜系–古第三系礫岩・砂岩など,どれも少量だが多様な岩石から構成される.1950年代から研究されはじめたが,その起源は長らく謎であった.写真は,下仁田南方の南牧川沿いに露出する逆転した跡倉層の下部白亜系砂岩・泥岩交互層である.近年,同層を含む関東山地の白亜紀砂岩中の砕屑性ジルコンのU–Pb年代が測定され(中畑ほか, 2015, 2016),跡倉層には原生代(25-15億年前)粒子が大量に含まれることが判明した.同じ関東山地でも約10 km南方の秩父帯の同時代砂岩とは大きく異なる後背地をもつこと,また西南日本では飛騨帯と舞鶴帯にのみ知られるペルム紀花崗岩を随伴することから,跡倉クリッペは関東でできた岩石群ではなく,もともと中生代日本の大陸側に起源をもち,二次的に長距離(最大100 km程度)移動してきた岩体と推定される.こんにゃくとネギで有名な下仁田地域の地質には,日本列島のルーツに関する秘密が隠されている.地元を走る上信電鉄の車体に大きくペイントされた「跡倉クリッペ」の文字をみて嬉しくなるのは「撮り鉄」ファンだけではないだろう.(写真・解説:磯﨑行雄)

著者

苅谷 愛彦 佐藤 剛 小森 次郎

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.117, no.3, pp.xv-xvi, 2008-06-25 (Released:2010-05-14)

著者

加藤 鉄之助

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.25, no.11, pp.755-768_1, 1913-11-15 (Released:2010-10-13)

著者

代田 寧 大場 武 谷口 無我 十河 孝夫 原田 昌武

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.6, pp.783-796, 2021-12-25 (Released:2022-01-28)

参考文献数

24

被引用文献数

2 2

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Earthquake swarms have occurred with volcanism repeatedly at Hakone volcano in Kanagawa prefecture, Japan. In 2015, a phreatic eruption took place about two months after the start of an earthquake swarm. Hakone volcano is a popular tourist destination. If it is possible to forecast at the early stages of an earthquake swarm whether or not an eruption will occur, the forecast could contribute to preventing disasters involving tourists. At Hakone volcano, increases in the ratio of components (CO2/H2S) contained in the volcanic gas from fumaroles were observed in synchronization with earthquake swarms and ground deformation in 2013 and 2015. Similar increases in CO2/H2S ratio were also observed in 2017 and 2019, although the increases in the CO2/H2S ratio in 2017 and 2019 were not as sharp as those in 2013 and 2015. Furthermore, the maximum values of the CO2/H2S ratio in 2017 and 2019 were lower than the values in 2013 and 2015. These differences in the CO2/H2S ratio may be related to the limited and smaller scale of volcanic activity in 2017 and 2019 relative to 2013 and 2015. Another explanation for the difference is a possible irreversible change in the underground structure of the Owakudani area, which is a geothermal area around Hakone volcano, because the phreatic eruption took place in the Owakudani area in 2015. During all four seismically active periods in 2013, 2015, 2017, and 2019, the CO2/H2S ratio decreased simultaneously with decreases in the number of volcanic earthquakes. The lower limit of CO2/H2S ratios after the peak of the CO2/H2S ratio time series was about 20 in all periods. This implies that subsequent unrest would not start until the CO2/H2S ratio drops to about 20. The CO2/H2S ratio might be an effective tool for forecasting activity at Hakone volcano. During the active periods in 2013, 2015, 2017, and 2019, extensions of the baseline across Hakone volcano were observed by GNSS with increases in the CO2/H2S ratio. A good correlation was found between the extensional velocity of the baseline length and the increasing rate of the CO2/H2S ratio. These variations could be examined at the early stage of unrest. The findings argue that the CO2/H2S ratio is a promising tool for predicting and evaluating volcanic activity at Hakone volcano.

著者

宮田 雄史

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.275-288, 2022-04-25 (Released:2022-05-13)

参考文献数

20

被引用文献数

2

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Gems must meet three requirements: be beautiful, be durable, and be rare. The concept beauty depends on personal values. It is, therefore, not something that is objective and separate from human society. Gems have relationships with society and have requirements. That is, it must be determined whether a gem is genuine or fake. Gems are essentially natural materials. They are generally minerals that are naturally occurring solids formed by geological processes. However, gems have a cultural aspect depending on how they are used. In a historical review, how these two aspects of gems have become the subject of scholarship is briefly elucidated. Currently, artificial gem materials are classified according to their growth history, and whether they are synthetic, man-made, imitations or composites. The task of defining these categories, in addition to natural gems and treated gems, is gem identification, which is based on gem variety, genesis (natural or artificial), treatments applied, (quality) origin (locality) and individual recognition. The development and current status of gemology is reviewed from the viewpoint of mineralogy.

著者

赤井 純治

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.131, no.2, pp.213-233, 2022-04-25 (Released:2022-05-13)

参考文献数

62

被引用文献数

2

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One of the most significant developing fields in mineralogy during the last quarter century involves interactions between microbes and minerals in the environment. A mineral evolution has been suggested. The fundamentals of biominerals, interactions between biosphere and minerals, and expanding knowledge of the biosphere are presented. Interactions between minerals and microbes are closely related to the evolution of the Earth's surface environment, and they suggest keys for solving environmental problems on the Earth. They are also related to the search for extraterrestrial life. This review sketches a brief history of mineralogy, referring to TEM methods, concerning regularity, irregularity, and interactions of minerals.

著者

土`山 明 松野 淳也

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.193-211, 2022-04-25 (Released:2022-05-13)

参考文献数

32

被引用文献数

2

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Chondritic-porous interplanetary dust particles (CP IDPs) originating from comet and carbonaceous chondrites of asteroids are primitive materials in the solar system. This paper reviews our recent research by mineralogical approach on the primitive materials, which include reproduction experiments of glass with embedded metal and sulfide (GEMS) in CP IDPs, detailed three-dimensional structures of GEMS, and discoveries of ultra-porous lithology as a “fossil of ice” in primitive carbonaceous chondrites and CO2-rich fluid inclusions in calcites of an aqueously-altered carbonaceous chondrite based on multi-scale three-dimensional observations. From the results, together with recent dynamic models of solar system formation, a new united model of the formation and evolution of primitive materials in the solar system is proposed as a working hypothesis. In this model, GEMS or GEMS-like materials corresponding to matrices of carbonaceous chondrites form due to the evaporation of precursors followed by condensation and chondrules due to melting followed by solidification in the highest temperature and moderately-high temperature regions, respectively, through a single local heating event. These local events occur at different distances from the sun and the high-temperature products were aggregated into comets and parent bodies of carbonaceous chondrites with ice and organic materials.

著者

大谷 栄治

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.131, no.2, pp.179-192, 2022-04-25 (Released:2022-05-13)

参考文献数

63

被引用文献数

2

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Various phase transitions occur in the Earth's interior. They cause discontinuities in seismic velocity and density profiles. The 410 km and 660 km discontinuities are explained by the olivine–wadsleyite transformation and the decomposition of ringwoodite into ferropericlase and bridgmanite, respectively. The major transitions in the lower mantle are the spin transition in mantle minerals containing ferric and ferrous irons, the post-perovskite transition of bridgmanite, i.e., the transformation of bridgmanite into a post-perovskite phase with a CaIrO3 structure. The former transition may occur at the shallow lower mantle, whereas the latter transition occurs at the bottom of the lower mantle, which may correspond to the D″ layer at the core–mantle boundary. There are several important seismic velocity anomalies. These include low-velocity anomalies associated with hot rising mantle plumes and oceanic ridge areas, and high-velocity anomalies associated with cold slab subduction. Ocean water is returned into the mantle by hydrous minerals stored in the slabs. Some hydrous minerals such as the solid solution of hydrous phase δ and phase H, AlOOH-MgSiO4H2 are stable along the normal geotherm to the core–mantle boundary, and bring water into the base of the lower mantle. Another interesting region is located at the base of the lower mantle. These anomalies are called the Large Low Shear Velocity Provinces (LLSVP) and the Ultra-Low Velocity Zones (ULVZ). An LLSVP is considered to be a region with iron enrichment. This region may be caused by accumulations of the high-pressure hydrous phases. A ULVZ with very low compressional and shear velocities and high densities is observed at the core–mantle boundary. This region may contain dense iron rich melts. The Earth's core is composed of a molten outer core and a solid inner core. It consists mainly of iron–nickel alloy with small amounts of light elements, such as Si, O, S, C and H. The inner core is considered to be composed of an hcp phase. However, some enigmatic properties of the inner core, such as low shear velocity and anisotropy, may not be explained only by this phase. Some experimental and theoretical studies suggest the existence of a bcc phase at a high temperature region approaching the melting temperature. Therefore, the inner core may be composed of a bcc phase or a mixture of hcp and bcc (or B2 phase which is an ordered form of the bcc structure). Further studies are necessary to achieve a better understanding of the Earth's core.

著者

宮脇 律郎

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.131, no.2, pp.129-132, 2022-04-25 (Released:2022-05-13)

参考文献数

11

著者

Ritsuro MIYAWAKI

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.125-128, 2022-04-25 (Released:2022-05-13)

参考文献数

11

著者

上野 勝美 Tamara I. NEMYROVSKA

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.117, no.5, pp.919-932, 2008-10-25 (Released:2010-04-27)

参考文献数

22

被引用文献数

7 8

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To better understand and update knowledge of the stratigraphy and foraminiferal and conodont faunal successions of Bashkirian-Moscovian (Pennsylvanian/Upper Carboniferous) boundary intervals in the Donets Basin of Ukraine, we studied the C21 to C26 suites (Limestones F to L) of the following eight stratigraphic sections located in the eastern part of the basin. These are the Karaguz, Volnukhino, Kriven'ky Yar, Rudnya, Zolotaya, and Malonikolaevka sections in Lugansk county and the Soroch'ya and Kholodnaya sections in Donetsk county. Among them, the Malonikolaevka section, which is located about 35km southwest of Lugansk and is documented for the first time in this study, provides important data on the faunal successions of the Bashkirian-Moscovian boundary interval, ranging from Limestones I2 to K3. Both the conodont and fusuline faunas record the appearances in the basal part of the C25 (K) Suite of several new taxa that are more characteristic of the early Moscovian. These forms include Declinognathodus donetzianus at the top of K1 in conodonts and Eofusulina triangula, E. trianguliformis, and a large Neostaffella species (N. vozhgalica) at K2 in fusulines. Thus, the K1-K2 interval is very promising as the potential position of the formal Bashkirian-Moscovian boundary in the Donets Basin. The data from the Malonikolaevka section, together with those from other sections in the present study, would be significant for future investigations of the Task Group to establish a GSSP close to the existing Bashkirian-Moscovian Boundary organized in IUGS Subcommission on Carboniferous Stratigraphy (SCCS).

著者

日野 文雄

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.50, no.2, pp.77-90, 1938-02-15 (Released:2010-10-13)

参考文献数

20

著者

日野 文雄

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.50, no.1, pp.19-30, 1938-01-15 (Released:2010-10-13)

著者

金田 楢太郎

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.5, no.4, pp.189-194, 1893-04-25 (Released:2010-10-13)

著者

山本 真也 中村 高志 芹澤 如比古 中村 誠司 安田 泰輔 内山 高

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.5, pp.665-676, 2020-10-25 (Released:2020-11-13)

参考文献数

40

被引用文献数

3 5

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Lake bottom springs play an important role in maintaining water quality in the Fuji Five Lakes. However, the sources of these springs and the hydrological delivery mechanisms have yet to be identified. To determine the sources of spring water of Lake Kawaguchi, samples were collected directly from lake bottom springs, and oxygen and hydrogen stable isotope ratios were obtained, along with vanadium concentrations. Visual observations and water-quality analyses of the samples reveal that cold and oxygen-rich water is discharged from the lake floor, which is covered by gravel with diameters of 10-50 cm over an area of approximately 9 m (east–west) by about 13 m (north–south). The water temperature of the springs remained relatively constant at around 11.3°C during the stratified period in 2016; however, the temperature fluctuated significantly in 2017, even during the stratified period, suggesting a temporary decrease or stoppage of water being discharged from springs into the lake. Oxygen and hydrogen stable isotopic ratios of lake bottom springs were determined to be higher than those of groundwater in the southern part of Lake Kawaguchi; however, they displayed values close to those of groundwater in the northern part of Lake Kawaguchi, suggesting that spring water primarily originated from groundwater in the Misaka Mountains.