The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 59, Issue 691
Displaying 1-5 of 5 articles from this issue
  • Sachio IGI
    1953 Volume 59 Issue 691 Pages 111-121
    Published: April 25, 1953
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    In Hokkaido, there are many ultra-mafic igneous bodies along the two parallel tectonic zones which are named the Kamuikotan zone and the Hidaka zone respectively., These tectonic zones compose the geological back-bone of Hokkaido, and are regarded as the product of a Cretaceous orogenic movement which is called "Hidaka Orogeny"., It is believed that the Hidaka zone may be an orogenic deep core and the Kamuikotan zone its westward over-thrusting zone., Many common characters have been noticed in the ultra-mafic igneous rocks of both tectonic zones., But contrasting features have also been observed in them., One of the most contrasted features is that the ultra-mafic rocks of the Kamuikotan zone are almost wholly serpentinized, on the other hand, those rocks are always in the unaltered peridotitic state in the Hidaka zone., In the Horoman region, at the southern end of the Hidaka tectonic zone, occurs the largest peridotite intrusive mass of the zone., The rock-forming minerals of this peridotite have an orientated arrangement, so the flow structure or layered structure are well marked in all parts of the mass., Judging from the arrangement of these flow structures, it seems that a large dome structure has existed at the centre of this peridotite mass, as presented in Fig 1., There are various kinds of rock facies in this peridotite mass, such as dunitic, pyroxene-peridotitic, and plagioclase-peridotitic facies etc., and each rock facies is developed in accordance with the flow structure., So, in a cliff, obvious appearance caused by the alternation of different kinds of rock facies seem clearly to be stratifications., (Plate 1)., -And their mineralassemblodges in each facies follow., 1., Olivine -(dark brown spinel) 2., Olivine -rhombic pyroxene-monoclinic pyroxene-(light brown spinel) 3., Olivine -rhombic pyroxene-monociinic pyroxene -(green spinel) 4., Olivine -monoclinic pyroxene-plagioclase-(black spinel) Optical characters of each mineralare given in Table 1., In this paper, the writer described the petrographical characters of each rock facies as a basis for further development of the knowledge about the Horoman peridotite mass., Further studies, especially concerning the intrusive tectonics, will be published in the near future by collaborators of the present writer.,
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  • Takeo BANBA
    1953 Volume 59 Issue 691 Pages 122-128
    Published: April 25, 1953
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    Two belts of spinel-bearing ultra-mafic rocks are known along the central mountain range of Hokkaido., On account of their geological environments and lithological properties, the ultra-mafic rocks in the western belt are named "Serpentinites in the Kamuikotan Zone", and the rocks of the eastern belt are called "Peridotites in the Hidaka Zone"., The spinels associated with the serpentinites in the Kamuikotan Zone are often euhedral and show usually reddish brown in thin section., In chemical composition the spinels are always rich in chromium, and they are never beyond the limits of chromite., The mode of occurrences and chemical components of the spinels associated with the peridotites in the Hidaka Zone are quite different from those of the Kamuikotan type., In general, the Hidaka Zone spinels show anhedral and brownish or greenish tenor in thin sections., The Cr2O3 contents are less than 50% while in the Kamuikotan Zone the Cr2O3 contents of the spinels are usually in excess of 55%., In several localities in the Kamuikotan Zone, peridotite scarcely serpentinized is found ; the spinels associated with such rocks show intermediate character between the spinels of the Hidaka type and those of the Kamuikotan type., Judging from the properties of the spinels, the peridotites in the Kamuikotan Zone may not be the relict of original rocks of the serpentinites.,
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  • Tadao SAITO
    1953 Volume 59 Issue 691 Pages 129-137
    Published: April 25, 1953
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The Yakumo mine is working lead-zinc-manganese deposits which are developed in the Neogene Tertiary formation and their mineralization in the deposits are recognized to occur in three stages from the mineral association of the ore., Quartz, rhodochrosite, galena, zincblende, pyrite and chalcopyrite etc., occur in each stage., The author studied minor elements contained in each of the ore minerals in the different stage, and the following results are obtained: 1) 24 elements (Si, Fe, Mn, Pb, Mg, Zn, Al, Cu, Ag, Au, Ba, Sb, As, Ca, Ti, Sr, Ru, Rh, Cd, Be, Ce, V, Ge and Se) are detected in the minerals from the deposits., Among those elements, Si, Fe, Mn, Al, Mg, Cu, Pb and Zn are discovered in all specimens, while another elements present in some specimens and they are sometimes absent., But no Ni, Co, Pt, Mo, W and Sn are found., 2) Above cited elements distribute differently in different stage of the mineralization., a) In case of minor components in the same minerals which crystallized in differents stages, variation (increase or decrease) of the following 4 groups of minor elements are observed: The groups are 1., Pb., Sb., Mg and Zn., 2., Al, Cu, Au and Ag., 3., Si, Mn, Fe, Ti, and Ca., 4., Ru, Cd, Be, Se, V, Rh, Ge, Sr, Ce and As : Contents of several minor elements vary in the same minerals in the different stages, with a few exception., But as some group tends to increase in the later stage, nevertheless in other minerals it may be not increase., According to circumstances it varies in the middle stage., b) In case of minor elements in different minerals in the same stage, minerals crystallized in earlier stage are apt to contain Si, Fe, Mg, Al, Ti, Cu, Pb and Zn, while the later crystallized mineals have As, Ag, Sb, Au, Mn, and Ca., But there are also exceptions in a few elements., Those minor elements have been found in minerals of epithermal origin., They may be considered to have some relation not only to the chemical character of the ore solution, but also to the condition of the ore-formation under which those minerals crystallized.,
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  • Yokichi TAKAYANAGI
    1953 Volume 59 Issue 691 Pages 139-148
    Published: April 25, 1953
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The Kushiro formation is one of the typical lower Pleistocene formations in Hokkaido., The stratigraphy, paleontology, especially the molluscs and pollen, and the geological age of this formation have been already reported and discussed in detail (Y., Otuka, 1934; Y., Sasa, 1939)., Herein the writer reported the smaller Foraminifera derived from three foraminiferous beds of this formation, namely, the Harutori mud bed of the Basal member, the Harutori shell sand bed of the Lower sand member and the Tenneru shell bed of the Middle sand member., The sedimentary features of these beds are divided into two facies, viz., the mud facies of the Harutori mud bed which occurs as a "rhythmite", and the shell sand of the latter beds., The foraminiferal assemblages of these two facies are characterized by their own particular former., The environment of the mud facies is considered to be Euneritic to Mesoneritic fascia, and that of the sand facies to belongto the Tidal to Euneritic fascia., Comparing the assemblage of 'the Harutori slaell sand bed with that of the Tenneru shell bed, the former indicates a condition rather deeper than the latter., From a comparative study of the fossil foraminifetal assemblage of the Kushiro formation with that of the Recent one off Kushiro, the following features are recognized: 1) Species abundant and common to both assemblages are Nonion japonicum, Pseudononion Nonionella pulchella, Elphidium etigoense, Elphidium kusiroense, Buliminella elegantissima, Eponides frigidus, and Cibicides lobatulus., 2) Species characteristic in the Recent assemblage are Eggerella, advena, Flphidium incertum clavatum, Elphidiella, sibirica and Discorbis baccata, these are common species in Arctic waters., 3) Characteristic species of large frequency in the fossil assemblage of the Kusiro formation are Quinqueloculina costata, Quinqueloculina hasimotoi, Elphidium concinnum, Discopulvinulina bradyi, Dicopulvinulina, of., nitida, Discopulvinulina orbicularis and Cymbalopora bradyi; these are common warm water species whose distributions are restricted to the sea south of the southern end of Hokkaido., 4) The species can be classified into the following 5 groups, namely, species of world wide distribution, species endemic to the seas surrounding Japan, warm water species, cold water species, etc., The respective distributions are shown in Fig., 2., From the above stated reasons, the foraminiferal assemblages of the Kushiro formation are infered to have lived under influence of thermal conditions warmer than at present.,
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  • Rokuro MORIKAWA
    1953 Volume 59 Issue 691 Pages 149-159
    Published: April 25, 1953
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The writer carefully studied the three areas in the Kitakami Mountainous Land shown in the following listed below., 1., Sakamotozawa valley., ., ., ., ., ., Hikoroichi-mura, Kesen-gun, Iwate Pref., (Lat., 39°1O'E., 141°1'45" E., ) 2., Kattizawa valley., ., ., ., ., ., Setamai-machi, Kesengun., 3., Kanokurazawa valley., ., ., ., ., ., A branch of Kattizawa valley., These three places are famous localities for fossils of Permian Period, and some formational names were established after these localities by several senior authors., The writer has divided the formations into the following three series, such as Upper Kofugane, Lower Kofugane, and Yubano-sawa series., Each series consists of limestone, sandstone, slate, and conglomerate., The following is the correlation Minato's stratigraphical table with the writer's., The writer's Minato's Limestone Slate (Toyoma slate) Kohama Stage Series Conglomerate (Usuginu Cg., ) Limestone., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Stage Shishiori Stage? Series Conglomerate ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Yubanosawa Series., ., ., ., Sakamotozawa Series In these localities, twenty-two fossil beds are observed, and these fossil beds may be grouped as the following seven fossil zones from which the writer has identified 11 genera and 34 species., 1., Lepidolina shiraiwensis zone 2., Neoschwagerina douvillei zone 3., Parafususina wanneri? Zone Limestone Sandstone Lower Kofugane Ser., (Upper Permian) 4., Pseudofusulina kraffti zone 5., P., vulgaris zone Limestone., ., ., ., ., ., Yubanosawa Series., ., ., ., ., ., ., ., ., ., ., ., ., 6., Pseudoschwagerina sp., Zone 7., Triticites irregularis zone Mid., Permian Lower Permian Upper Carboniferous It is notable that the Triticites zone is discovered while the absence of so-called Parafusulina ? japonica zone.,
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