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Volume 76, Issue 5
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Yuzo Kato, Hisanori Iwazawa1981 Volume 76 Issue 5 Pages 147-155
Published: May 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSHashigami granitic mass, one of the Cretaceous granitic intrusives in Kitakami mountains, is divided into three rock types on the basis of observation in the field and under the microscope. Three types are named Hashigamidake, Waza and Akedo, in order of intrusion. In the three types of them, the former two contain both biotite and hornblende, however the last one does biotite only. Rocks of the all types are tonalite or granodiorite.
Fifteen rocks, five hornblendes and five biotites from the mass were analysed chemically. These results show that Si02 content and Na2O/K2O ratio of each rock type increase in order of intrusion. In comparison with the average atomic ratio of hornblende coexisting with biotite in calc-alkaline granities from the world, hornblendes of the mass contain a little higher AlIV, Ti and Na, suggesting slightly higher content of edenite and titanoamphibole moles. The distribution coefficients of Mg-Fe2+ between biotite and hornblende eliminated influence of compositional dependence show evident difference between Hashigamidake and Waza types suggesting that there is difference in temperature and/or pressure conditions between the two types.
The Hashigami granites have many similarities with the Iwaizumi granites in the field and microscopic characteristics as well as the features on petrochemistry and mineral chemistry. These many similarities probably reflect the resemblance in mechanism of intrusion and solidification of the magma in addition to the origin of it. Presence of cumulate of biotite in both two masses supports the possibility that the rocks containing extraordinarily low K2O are originated from elimination of biotite from the magma of ordinary composition.View full abstractDownload PDF (1584K) -
YOSHIMASU KURODA, HIROAKI SHIRAI, TETSURO SUZUOKI, SADAO MATSUO1981 Volume 76 Issue 5 Pages 156-162
Published: May 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSAnthophyllite, biotite, cordierite and muscovite in the metasomatic rocks such as anthophyllite-cordierite rock closely associated with the copper-bearing iron-sulfide ores were separated to determine their δD and XFe values. The δD values of the ambient water in the process of formation of the metasomatic rocks can be estimated to be about -30‰ from these values. Coexisting biotite and hornblende from the Cretaceous granodiorite adjacent to the ore deposit showed the equilibrium relationship on δD-XFe diagram and the estimated δD value of the water equilibrated with both minerals is the same as the value for the metasomatic rocks. Two kinds of water participating in the ore formation and in the granodiorite intrusion seem to be derived from the same origin. On the other hand, δD values of hornblende from the amphibolites of normal chemical composition, which seem to be metamorphosed from basic tuffs and volcanic rocks without metasomatic change of composition are inferred to be in equilibrium to water with δD far lower than -30‰.View full abstractDownload PDF (509K) -
YUKIO IKEDA, MICHIO TAGIRI1981 Volume 76 Issue 5 Pages 163-171
Published: May 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe coarsening of calcite grains in massive white limestone of the contact aureole of the Senmaya granitic body can be described by the equation;
, W3-W03=1.81×1018×[t50exp(-33600/T25)+(t100-t50)×exp(-33600/T75)].
W and W0 are the final and initial grain size (in microns) of calcite, T25 and T75 are the temperatures 25°C and 75°C lower than the highest temperature the sample experienced, and t50 and t100 are the duration (in years) of heating above the temperature 50°C and 100°C lower than the highest temperature experienced by the sample.View full abstractDownload PDF (639K) -
HARUO OHASHI, TOSHIKAZU OSAWA1981 Volume 76 Issue 5 Pages 172-175
Published: May 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESS -
RYUJI KITAGAWA, SATORU KAKITANI1981 Volume 76 Issue 5 Pages 176-179
Published: May 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSTwo mica clay minerals in clay veins developed in Hiroshima granitic rock and Takada rhyolitic rock distributed in Hiroshima Prefecture were dated by K-Ar method. The age of both minerals are 68.4 m. y. and 79.5 m. y. respectively. The ages of mica clay minerals are similar to that of the Hiroshima granitic rocks (70-91 m. y.). This result may be suggested that the mica clay minerals found in both host rocks are formed by hydrothermal solution subsequent to the post granitic activity.View full abstractDownload PDF (852K)
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