JOURNAL OF MINERALOGY, PETROLOGY AND ECONOMIC GEOLOGY
Online ISSN : 1881-3275
Print ISSN : 0914-9783
ISSN-L : 0914-9783
Volume 85, Issue 4
Displaying 1-4 of 4 articles from this issue
  • Jun Aizawa
    1990 Volume 85 Issue 4 Pages 145-154
    Published: April 05, 1990
    Released on J-STAGE: March 18, 2008
    JOURNAL FREE ACCESS
    Homogenization temperatures of fluid inclusions in quartz and/or calcite that coexist with carbonaceous material in sedimentary rocks from selected Tertiary coalfields have been measured. A correlation between these fluid inclusion temperatures and vitrinite reflectance as a rank parameter of coal is presented. All mineral samples analyzed here were collected outside of high coal rank regions adjacent to intrusive rocks in each coalfield. The minimum values of homogenization temperatures obtained in this study are at least regarded as representing temperatures attained by the sedimentary rocks during burial metamorphism.
    This study indicates a direct relationship between minimum value of homogenization temperature (T in °C) and vitrinite reflectance (Rmax, in %) with a regression equation of the form; Rmax=0.352 exp 0.00976•T. Previous works on the temperature of Rmex are based mainly on present temperatures such as present geothermal gradients or pyrolysis experiments. As the reaction rate of thermal maturation of carbonaceous material differs in diagenesis, geothermal systems, and contact metamorphism, the equation obtained here may be employed as a useful tool to estimate paleotemperatures in Tertiary sedimentary basins.
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  • Koichi Tazaki, Jiro Takahashi, Tetsumaru Itaya, R. H. Grapes, Naruhiko ...
    1990 Volume 85 Issue 4 Pages 155-160
    Published: April 05, 1990
    Released on J-STAGE: March 18, 2008
    JOURNAL FREE ACCESS
    Many andesitic intrusions are exposed along the Median Tectonic Line (MTL) in northwestern Shikoku, Japan. Three dikes along the MTL and one intrusion occurring close to it were dated by the K-Ar method to estimate when the fault movement ceased. The dikes and intrusion are not deformed by the movement. The results give 15.1 to 15.4 Ma excluding severely altered one. The MTL in northwestern Shikoku region has not been active since about 15 Ma. Although a similar attenuation of active movement of the MTL during middle Miocene has been reported, the fault movement has continued in the other areas of southwestern Japan as demonstrated by Active Fault Research Group (1980). This may suggest that block displacement has been dominant since middle Miocene in the studied area. The age of the samples also indicates that the volcanic activity of Seto-uchi region started 15 Ma in northwestern Shikoku.
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  • JOHN S. MACKENZIE, SACHIRO TAGUCHI, TETSUMARU ITAYA
    1990 Volume 85 Issue 4 Pages 161-167
    Published: April 05, 1990
    Released on J-STAGE: March 18, 2008
    JOURNAL FREE ACCESS
    An axial-planar cleavage associated with folded sedimentary rocks of the Paleogene Shimanto Belt of eastern Kyushu was sampled and a < 2μ clay fraction separated and dated by K-Ar isotopic analysis. Experimental results yield a K-Ar age of 48.4±1 Ma. The cleavage minerals sampled, being axial-planar to the folds, are assumed to be syn-tectonic, their crystallization age thus corresponding to the age of the folds themselves.
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  • 1990 Volume 85 Issue 4 Pages 168-196
    Published: 1990
    Released on J-STAGE: July 13, 2012
    JOURNAL FREE ACCESS
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