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Volume 71, Issue 1
Displaying 1-4 of 4 articles from this issue
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Y. KURODA, T. SUZUOKI, S. MATSUO, H. TANAKA1976 Volume 71 Issue 1 Pages 1-5
Published: January 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSTabito composite mass consists of two groups of intrusions, e.g. the older (Myojin-ishi quartz-diorite and gabbro) and the younger (Komuro quartz-diorite and Iritabynto grano-diorite). The equilibrium relationship is recognized on δD-XFe plots of coexisting biotite-hornblende pairs. δD value of water in magma coexisted with biotite and hornblende in the younger group is estimated to be almost similar to that for the granitic masses in the Kitakami mountaineous district (-29 to -37‰), while that in the older group is clearly lighter (-40 to -55‰)View full abstractDownload PDF (209K) -
AKIRA ONO1976 Volume 71 Issue 1 Pages 6-17
Published: January 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSZircons from granitic intrusive rocks and pyroclastic flows were analysed by means of an electronprobe microanalyzer. The Hf02 contents of zircons coexisting with plagioclases more calcic than An30 are 1.5 to 1.6 by weight per cent. Zircons coexisting with less calcic plagioclases range from 1.5 to 2.5 wt% in Hf02 content. The Hf/Zr ratio in liquid phase of a felsic magma increases by progress in crystallization of zircon crystals. A study of the luminescence of polished zircon crystals revealed oscillatory and sector zonings which were not observable under optical microscope.View full abstractDownload PDF (1123K) -
Matsuo Nambu, Shimpei Kano, Yôichi Muramatsu1976 Volume 71 Issue 1 Pages 18-26
Published: January 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSTroilite was detected from the pyrrhotite-chalcopyrite massive ores of the Akagane and Kamaishi Mines by means of the optical, electron probe microanalyses and x-ray powder diffraction. The mineral occurs as the exsolution lamellae oriented in one or two directions in the grain of hexagonal pyrrhotite up to 200 microns in diameter; in certain specimen of the Kamaishi Mine, it occurs also as the grain up to 200 microns in diameter containing the irregular shaped hexagonal pyrrhotite, and is associated with the hexagonal pyrrhotite grain.
X-ray powder diffraction of troilite gives d(102)=2.0928_??_2.0932Å, which closely corresponds to the stoichiometric composition of FeS in reference to the published data. The hexagonal pyrrhotite constituting a groundmass contains always 47.7 atomic percent of iron and is thought to have reached an equilibrium with lamellar troilite at the earth-surface temperature. Calculated bulk composition of troilite-hexagonal pyrrhotite assemblage, 48.1 atomic percent Fe for the Akagane and 49.3 for the Kamaishi, indicates that the homogeneous parent Fel-xS phase begin to exsolve troilite nearly at 50° and 130°C in respective specimens. The parent Fe1-xS phase is believed to have been formed at an earlier stage of sulfide mineralization, and the difference in its composition to reflect differences in temperature and/or oxygen fugacity at genesis.View full abstractDownload PDF (1620K) -
KAZUO YOSHIKAWA1976 Volume 71 Issue 1 Pages 27-36
Published: January 05, 1976
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe phase relations in the join acmite - Ca-Tschermak's molecule at high pressures from 10 to 30 kb were studied. The amount of Ca-Tschermak's molecule soluble in acmite is between 5 and 7 wt % at 1 atm. (Yoshikawa and Onuma, 1975). CaA12SiO6 solubility in NaFeSi2O6 increases with increasing pressure and attains at least 70 wt % at 950°C and 18 kb. The solubility of CaAl2SiO6 in acmite is also affected not only by pressure but also by temperature and is facilitated under higher pressure and higher temperature conditions. At 1250°C there is a complete series of solid solutions between these two endmembers. The phase assemblages change with increasing pressure as follows: pyroxeness+nepheliness+plagioclasess (ss=solid solution), pyroxeness, and pyroxeness+garnetss+corundumss. Associated with these changes, the compoition of pyroxeness in this join also changes from lower pressure to higher as follows: NaFeSi2O6+CaAl2SiO6+CaFeAlSiO6, NaFeSi2O6+CaAl2SiO6, and NaFeSi2O6+CaA12SiO6+NaA1Si2O6. The composition of garnet solid solutions becomes richer in andradite molecule with increasing pressureView full abstractDownload PDF (411K)
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