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Volume 11 (1977)
- Issue 4 Pages 183-
- Issue 3 Pages 111-
- Issue 2 Pages 57-
- Issue 1 Pages 1-
Volume 11, Issue 2
Displaying 1-7 of 7 articles from this issue
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Ken Shibata, Sachio Igi, Shigeru Uchiumi1977 Volume 11 Issue 2 Pages 57-64
Published: June 20, 1977
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSK-Ar age determinations have been carried out on 15 hornblendes from the Yakuno Basic Rocks and their affinities in the Inner Zone of Southwest Japan. Gabbroic rocks from the Yakuno Basic Rocks and those from the Sangun Metamorphic Terrane in eastern Chugoku gave ages ranging from 228 to 275 m.y.; more than half of them are concordant with the geologically estimated age of the rocks. Remaining older ages may indicate either the time of plutonism in Early Permian, which might have been contemporaneous and comagmatic with the basic volcanic activity in the same areas, or the existence of inherited argon in hornblendes. Ages of gabbroic rocks from the Sangun Metamorphic Terrane in northern Kyushu are 296-372m.y., all older than those from eastern Chugoku. Hornblendes from gabbroic rocks in the Nagasaki Metamorphic Terrane gave still older ages of 449-472m.y., suggesting that these rocks may be a part of old basement rocks in the Japanese Islands. Graphical presentation of argon and potassium data indicates that most of the hornblende samples contain no significant amount of excess argon.View full abstractDownload PDF (1782K) -
W. P. Leeman, B. R. Doe, Joseph Whelan1977 Volume 11 Issue 2 Pages 65-74
Published: June 20, 1977
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSamples of travertine and siliceous sinter from hot-spring deposits in Yellowstone National Park of northwestern Wyoming have been analyzed for light stable (carbon and oxygen) and radiogenic (lead and strontium) isotopes. The Hillside Springs travertine contains significantly lighter δ13C than the previously studied Mammoth travertine. Although this relation could indicate a component of magmatic carbon, more likely it reflects a higher temperature of precipitation for Hillside Spring travertine. Our data on Mammoth travertine shows it to have been precipitated substantially below the orifice temperature. The oxygen isotope data on the newly analyzed deposits confirm the previous studies that found the hot-spring waters to be dominated by meteoric water. The lead isotope data show that there is a sedimentary component of lead in all the hot-spring deposits analyzed, including those inside the caldera limits. Either long lateral migration of waters are involved in the recharge of the springs or there must be sediments buried at some unknown depth beneath the volcanic rocks inside the caldera because no sediments are known at the surface. The high rainfall inside the limits of the caldera would favor sediments buried at depth.View full abstractDownload PDF (3135K) -
P. K. Kuroda, R. D. Sherrill, K. C. Jackson1977 Volume 11 Issue 2 Pages 75-90
Published: June 20, 1977
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe contents and the isotopic compositions have been measured mass-spectrometrically for neon, argon, krypton and xenon released from four specimens of granites in stepwise-heating experiments. These rocks contained appreciable amounts of 40Ar from the decay of 40K and 131-136Xe from the 238U spontaneous fission. The contents of neon, argon (excluding 40Ar), krypton and xenon in these granites were considerably lower than the estimated rare gas contents of rocks reported by BROWN (1949), except for the Red Rock granite, which contained an abnormally large amount of xenon. The Ne/Xe, Ar/Xe and Kr/Xe ratios in the Red Rock granite were abnormal in that they resembled the relative abundances in meteorites. Moreover, a large fraction of the total xenon released from the Red Rock granite appeared to be a mixture of AVCC xenon and the atmospheric xenon. The Red Rock granite is from the Sudbury structure, Ontario, Canada, which is believed to have been formed by the impact of an asteroid in an event that formed a crater 30 miles in diameter 1, 720 million years ago.View full abstractDownload PDF (3454K) -
Yasuhiro Kiyosu1977 Volume 11 Issue 2 Pages 91-99
Published: June 20, 1977
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSulfur isotopic compositions of sulfide minerals from mesothermal fissure-filling ore deposits of the Taishu mine have been investigated. The δ34S values of 65 sulfide samples range from +2.7 to +6.4 permil, giving an average of +4.4 permil. Sulfide minerals exhibit a decreasing trend of δ34S values: sphalerite > pyrrhotite > galena. Sulfur isotope temperatures estimated from sulfur isotopic fractionation between sphalerite and galena are 300° to 350°C, which agree with the maximum value of fluid inclusion temperature for quartz. From sulfur isotopic evidences and chemical equilibrium concept of ore deposition, it is suggested that the chemical condition of ore-forming fluid was restricted to low fO2 and neutrality. The mean δ34S value of sulfide minerals for each vein was found to increase from the early to the late vein. This progressive 34S enrichment is presumably due to the pH change in ore-forming fluid during ore deposition.View full abstractDownload PDF (2239K) -
Yasutami Oka1977 Volume 11 Issue 2 Pages 101-106
Published: June 20, 1977
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSMixing of Fe and Mg in orthopyroxene crystalline solution can be represented by a multicomponent regular solution model when the molecules (MgM1MgM2Si2O6, FeM1FeM2Si2O6, FeM1MgM2Si2O6 and MgM1FeM2Si2O6) are introduced as its components. In this regular solution model, there are three independent interaction parameters (WM1, WM2 and WM12) which correspond to the cation interactions between M1 and M1 sites, M2 and M2 sites and M1 and M2 sites, respectively. These parameters can not be determined uniquely by site-occupancy measurements only. Some thermodynamic formulations for orthopyroxene are given by using these parameters.View full abstractDownload PDF (1200K) -
Yukihiro Matsuhisa1977 Volume 11 Issue 2 Pages 107-109
Published: June 20, 1977
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSDownload PDF (821K) -
1977 Volume 11 Issue 2 Pages e1
Published: 1977
Released on J-STAGE: February 06, 2009
JOURNAL FREE ACCESSDownload PDF (262K)
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