Journal of Mineralogical and Petrological Sciences
Online ISSN : 1349-3825
Print ISSN : 1345-6296
ISSN-L : 1345-6296
Volume 96 , Issue 5
October
Showing 1-5 articles out of 5 articles from the selected issue
ORIGINAL ARTICLES
  • Yoji ARAKAWA, Tsugio KOUTA, Yasuhide KANDA
    2001 Volume 96 Issue 5 Pages 175-187
    Published: 2001
    Released: November 21, 2005
    JOURNALS FREE ACCESS
    Geochemical analyses were performed on amphibolites in the Oki metamorphic rocks in Oki-Dogo Island, southwestern Japan. The amphibolites occur as layers or boulders in the pelitic and psammitic gneisses. Major and trace element characteristics suggest tholeiitic or alkaline chemical affinities and are divided into two groups (Group I and II). Group I amphibolites occurring as layers are characterized by low SiO2 (43.5-46.6%) and high TiO2 (>2.6%) and P2O5 (>0.5%), whereas Group II amphibolites by high SiO2 (46.5-47.6%) and low TiO2 (<1.6%) and P2O5 (<0.2%). Relative enrichment of incompatible elements and their high ratios (such as Zr/Y, Ti/ Y, Ta/Yb), and light rare-earth element (LREE) enriched patterns for Group I samples signify that the protoliths of Group I amphibolites correspond to within-plate basalt. In contrast, Group II amphibolites, marked by low contents of incompatible elements and nearly flat REE patterns, are further classified into three sub-groups (IIa, IIb and IIc). Group IIa and IIb amphibolites occur as boulders and the IIc as a layer in the psammitic gneissses. Group IIa and IIc amphibolites resemble tholeiitic basalt in oceanic island-arc tectonic setting, whilst the IIb amphibolite boulder represents chemical similarity to the E-type MORB. With exception of boulder-like amphibolites, the predominance of the Group I amphibolites suggests that the protolith formation of amphibolites (and clastic sedimentation) occurred in an intracontinental tectonic setting.
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  • Norimasa SHIMOBAYASHI, Masao KITAMURA
    2001 Volume 96 Issue 5 Pages 188-196
    Published: 2001
    Released: November 21, 2005
    JOURNALS FREE ACCESS
    The growth habit of needle-shaped crystals in coats of coated diamonds from Zaire was observed using a cathodoluminescence microscope. An aggregate of needle crystals of diamonds coats a single crystal of core in an octahedral shape, and the tips of the needle crystals in the coats are bounded by curved {100} faces (or cuboids) with small {111} facets, showing the distinct sector-zoning in CL brightness. The needle is responsible for ‘random walk model’, which can explain the external morphology of coated stones. This characteristic growth of the needle crystals were interpreted to be formed by the co-precipitation of inclusions and due to the rapid growth controlled by the kinetic roughening of the octahedral faces and the kinetic smoothening of the cuboid faces. Morphology of the needles to those of diamonds by mixed-habit growth suggests that both types of diamonds have grown under similar conditions, except for the co-precipitation of inclusions.
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  • Mohammad ZAFAR, Mamoru MURATA, Arshad ALI, Iffat JABEEN, Tahseenullah ...
    2001 Volume 96 Issue 5 Pages 197-204
    Published: 2001
    Released: November 21, 2005
    JOURNALS FREE ACCESS
    The Garam Chashma granites in the Hindukush Range (Trans-Himalayas) on the southern margin of the Asian plate, northwestern Pakistan, are peraluminous with a restricted SiO2 range and K-Ar biotite ages of 20-18 Ma. Their δ18O values range between 11.48 and 12.72‰, which represent the S-type nature. The K-Ar ages and petrological characteristics of Garam Chashma granites are similar to those of Pakistan, India and Nepal Higher Himalayan S-type granites. Since most of the granitic rocks in the Trans-Himalayas are I-type with ages from 100 to 40 Ma, the Garam Chashma granite are considered to be formed by the similar source and at the same time as the other Higher Himalayan S-type granites.
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  • Yasuyuki BANNO, Michiaki BUNNO, Makoto HARUNA, Masahiro OBA
    2001 Volume 96 Issue 5 Pages 205-209
    Published: 2001
    Released: November 21, 2005
    JOURNALS FREE ACCESS
    Stibiotantalite-group minerals were found from a lithium pegmatite, Nagatare, Fukuoka Prefecture, Japan. Two samples were examined; one is stibiotantalite, compositionally close to the ideal formula SbTaO4 and the other is a member of bismutotantalite-stibiotantalite series. The stibiotantalite grain is homogeneous in composition, and has high Ta/(Ta+Nb) values of 0.91-0.92. The bismutotantalite-stibiotantalite grain is very heterogeneous, and the ranges of Bi/(Bi+Sb) and Ta/(Ta+Nb) values are 0.26-0.54 and 0.71-0.81, respectively. This grain is heavily veined by Bi-poorer stibiotantalite. Compositional variation in Bi/(Bi+Sb) of this grain indicates the existence of solid solution between bismutotantalite and stibiotantalite with relatively wide range. The unit cell parameters of the stibiotantalite and the bismutotantalite-stibiotantalite are; orthorhombic a=4.916(1), b=11.811(1), c=5.536(1) Å and a=4.945(1), b=11.794(2), c=5.592(1) Å, respectively.
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Errata
  • 2001 Volume 96 Issue 5 Pages 214
    Published: 2001
    Released: November 30, 2005
    JOURNALS FREE ACCESS
    The above PDF file shows errata of Table 3 in the paper entitled “Kinoite from Fuka, Okayama Prefecture, Japan” by Isao KUSACHI, Makoto NISHIMURA, Kanako SHIRAGA, Shoichi KOBAYASHI and Junji YAMAKAWA (Vol. 96, no. 1, 29-33, 2001). Wrong:See PDF attached
    Right:See PDF attached
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