巻号一覧
28 巻, 1 号
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河内 洋佑, 渡辺 暉夫原稿種別: 本文
1974 年 28 巻 1 号 p. 1-10
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスACF and similar other triangular and tetrahedral diagrams have been used widely to analyze mineral parageneses of metamorphic rocks. Listed parageneses, however, are contradictory to the accompaying diagrams in many papers; that is, they result in crossing tie lines and/or more number of phases than each compositional triangle/tetrahedron of the diagram can show. This contradiction has been commonly ignored or explained as such that the rock consists of far more numbers of components than the diagram can show or that the rock is in disequilibrium, However, as long as the assumptions employed to reduce the number of components into three or four are valid, the diagram should show perfectly the parageneses under consideration. When we take minerals in mutual contact under the microscope as paragenetic, but exclude minerals not in contact however closely they occur, an ACF diagram constructed from phases occurring side by side can represent successfully all the parageneses observed in the same metamorphic grade. This leads to a result that a series of ACF diagrams obtained from a progressively metamorphosed terrane can be arranged so as to represent a series of univariant reactions (WATANABE, in press; WATANABE & KAWACHI, in preparation). Thus each metamorphic isograd will be denned by respective univariant reaction. In low grade rocks, as the equilibrium is reached only within a few to several tens of microns, a grain of mineral should often be considered to represent a domain having bulk composition of that mineral. A wide variety of metamorphic mineral assemblages occur in basaltic lava flows in contrast to much simpler variety in tuffs intercalating with the former in the Mesozoic rocks of the Akaishi Mts. in Shimanto belt, central Japan (SEKINE & MATSUURA, in preparation): lava consisting of many small domains (phenocrysts and groundmass etc.) of different bulk compositions while tuff a few domains (laminations with small chemical difference). HASHIMOTO (1972) stressed that an actinolite overgrowth on relict clinopyroxene does not represent actinolite isograd while actinolite in a matrix of mafic rock does. This seems to be a matter of definition rather than an equilibrium as HASHIMOTO has claimed: either an isograd is based on a rather unusual bulk composition represented by relict clinopyroxene or an ordinary bulk composition represented by mafic tuffaceous matrix.抄録全体を表示PDF形式でダウンロード (1263K) -
宮島 圭司原稿種別: 本文
1974 年 28 巻 1 号 p. 11-21
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスThe purpose of this study is to try an analysis for rock slope stability which is not well established and consider geological meanings of the results of analysis. The data of reck slope failures of road cuts in Shikoku are used for the investigation. Three thpes are distinquished as rock slope failures and roke slope stability is studied restrictedly based on the failure of " type 2" by the author's definition which is considered to reflect rock slope strength. He improves a kind of statistical slope stability analysis proposed by MURAKAMI and MIYAUCHI (1967), and an apparent shear strength and a critical slope height of weathered sedimentary and metamorphic rocks (ranging Paleozoic to Mesozoic in Shikoku) slope, are estimated respectively applying soil mechanics technique. The significance of estimation are confirmed comparing the results with the actual conditions of corresponding stable rock slopes and slope protection methods in Shikoku. As the case study to find geological meanings of slope stability analysis, Cretaseous Izumi Group which shows rather simple geological structures is minutely investigated the relation between the results of analysis and geological condition of rock slopes covering wide areas. Estimated shear strength of rock slopes seems to represent local characteristics of geological structure and sedimentary conditions and is affected considerably by the degree of crushing for Izumi Group caused by the Median tectonic line. Preliminary research for other Paleozonic and Mesozoic rock slope stability also indicates that these rock slope are effected by the inherent geologic developments characterized zonal strutures of Shikoku. Thus, engineering geology may contribute to study of geologic history, especialy to tectonic movements in this case.抄録全体を表示PDF形式でダウンロード (1283K) -
星野 通平原稿種別: 本文
1974 年 28 巻 1 号 p. 22-26
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスPDF形式でダウンロード (632K) -
鈴木 堯士, 黒田 吉益原稿種別: 本文
1974 年 28 巻 1 号 p. 27-36
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスOphiolite associations of Middle Asia develop in the Variscan folded belts and are exposed in the form of separate bodies in the ranges of the Southern Tien Shan and the Kizil-Kum ranges. The total length of the ophiolite belt is over 1,800 km. These ranges are composed of sedimentary, volcanic and plutonic rocks of Precambrian and Paleozoic ages, which are folded complicatedly with overthrust and nappe structures. On the other hand, ophiolite associations of Lesser Caucasus are observed in the Alpine folded belts along the Terter river. They are overlain with a sharp unconformity by the Upper Jurassic-Cretaceous deposits. The inner structures of the ophiolite zones in Middle Asia and Lesser Caucasus are very similar except age of formation. Both serpentinite melange and tectonized olistostrome are formed in the process of tectonic movement. There is no intrusive contact between ultramafic and gabbroic complexes of the ophiolites. Blocks of various ages and rocktypes in serpentinite melange are recognized; ultramafics, gabbro, diabase, spilite, jasper, chert, limestone, sandstone, green-schist and glaucophane-schist. According to A.V. Peive, eugeosynclines originated on the basement composed of oceanic crust, and the former oceanic crust is tectonically squeezed out along the faults; it is altered to the melange and often occurs at the base of major allochthonous slabs. His negation of Stille's eugeosynclinal "initial" magmatism and Steinmann's trinity of the ophiolites brings forward a new problem as to the genesis of ophiolites.抄録全体を表示PDF形式でダウンロード (1312K) -
衣笠 弘直原稿種別: 本文
1974 年 28 巻 1 号 p. 37-40
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスPDF形式でダウンロード (392K) -
長谷川 力原稿種別: 本文
1974 年 28 巻 1 号 p. 41-46
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスPDF形式でダウンロード (432K) -
日本の第四紀層の14C年代(91)池田 芳雄原稿種別: 本文
1974 年 28 巻 1 号 p. 47-48
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスPDF形式でダウンロード (284K) -
日本の第四紀層の14C年代(92)関東第四紀研究会原稿種別: 本文
1974 年 28 巻 1 号 p. 49-50
発行日: 1974/01/20
公開日: 2017/07/26
ジャーナル オープンアクセスPDF形式でダウンロード (288K)
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