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Volume 76, Issue 8
Displaying 1-4 of 4 articles from this issue
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YOSHIRO OHTSUKA, YOSHINORI FUJIKI, YOSHIO SUZUKI1981 Volume 76 Issue 8 Pages 253-261
Published: August 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe control effect of PO2 by oxygen buffers was hydrothermally examined, and it was observed that the oxygen buffers of HM and NNO react effectively for longer time 300 hours using an H2O solvent at 530°C under 1000 atm.
The hydrothermal reactions in the system TiO20•nH2O-KF-K2HPO4-H2O produced anatase, potassium hexatitanate and rutile with increasing temperature, and it was not found the effects of PO2 on the temperature range of their formation. Anatase grown by controlled PO2 is characterized by the increase of c parameter with decreasing PO2.
Anatase-rutile transformation was examined under the hydrothermal conditions of controlled PO2. The rate equation of this transition abides by the Avrami model equation. It was found that the kinetic data of pure and stabilized anatase are expressed by the firstorder equation in an H2O buffer. However, the stabilized anatase abides by the higherorder equation than n=1 in the buffers of HM and NNO.View full abstractDownload PDF (1311K) -
RYUJI KITAGAWA, SATORU KAKITANI, SETSUO TAKENO, YOSHIHARU NISHIDA1981 Volume 76 Issue 8 Pages 262-272
Published: August 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSOn clay minerals found in veins developed in the Kumogi granite mass in the vicinity of Hamada city, Shimane Prefecture, the modes of occurrence and mineralogy such as polytypes and crystal forms were investigated. The clay veins are distinctly divided into three types (types I, II and III) based on the mode of occurrence. The clay veins of type I are formed along nearly vertical faults or fissures, type II occurs as replacement products in vein-form and type III are formed along small fissures or joints. The clay veins of types I and II are composed of mainly mica clay mineral and type III are composed of mainly kaolin minerals. The polytypes of mica clay mineral of type I are identified to be 1Md, IM and 2M, while that of type II is only 2M. The modes of occurrence and mineralogy of the clay minerals of types I and III show almost the same mineralogical characteristics to those of clay veins found in Hiroshima granitic rocks (Kitagawa and Kakitani, 1978a, b, c), while the type II is characteristic in the Kumogi granite mass.
Topographical examinations of mica clay (type I) and kaolin (type III) veins show that mica clay veins are mainly distributed in the margin of the granite mass which is situated at the lower level, while kaolin veins in the middle part of the mass is situated at relatively higher level. More detail examination of type I indicats that 2M mica clay minerals are found in the margin of the mass and relatively in the lower than lMd mica clay minerals.
It may be indicated from these results and study of Imaoka et al. (1977) and Ishihara et al. (1980), mica clay minerals in type I veins were formed by hydrothermal solution which interacted with meteoric ground water which intruded from the margin of the granite mass.View full abstractDownload PDF (2063K) -
HARUO OHASHI1981 Volume 76 Issue 8 Pages 273-275
Published: August 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe mean Si-O bond length in M22+SiO4 olivine decreases with an increase of the binding energy of O (1s) electrons.View full abstractDownload PDF (180K) -
AGE DETERMINATION FOR SETOUCHI VOLCANIC ROCKS, NO. 6Toshitsugu Yamazaki, Masayuki Torii, Kyoichi Ishizaka1981 Volume 76 Issue 8 Pages 276-280
Published: August 05, 1981
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSFission track ages were determined on two zircon separates from the Setouchi acidic volcanics occurring in Takamatsu and Shodo-Shima, northeastern part of Shikoku. They yielded concordant ages of 13.9±1.4 Ma and 14.0±1.2 Ma, respectively. A glassy, densely welded acidic volcanic rocks occurring in the northwestern part of Shikoku, referred to the Matsuyama welded tuff, yielded a K-Ar age of 14.2±0.8 Ma. These results indicate, together with the reported identical K-Ar ages for the Setouchi acidic volcanics in the southern part of Oita Prefecture, that the acidic volcanic activity occurred approximately 14 million years ago and was contemporaneous with the acidic igneous activity occurred 14±1 million years ago in the Outer Zone of Southwest Japan. In the Setouchi volcanic belt, mafic volcanic activity, represented by the extrusion of Sanukitoid magma, occurred slightly later than or almost contemporaneously with the acidic volcanic activity.View full abstractDownload PDF (407K)
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