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Volume 12 (1978)
- Issue 4 Pages 201-
- Issue 3 Pages 137-
- Issue 2 Pages 69-
- Issue 1 Pages 1-
Volume 12, Issue 4
Displaying 1-12 of 12 articles from this issue
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Takashi Miyano1978 Volume 12 Issue 4 Pages 201-211
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSMineral assemblages and the Fe/(Fe+Mg) ratio in minnesotaite are evidently different for some low-grade metamorphic Precambrian iron formations in spite of very similar metamorphic conditions (temperature, probably pressure, and rock chemistry). Since carbonates, siderite and ankerite are commonly found, such differences are considered to have been caused by a difference in the degree of the escape of carbon dioxide during metamorphism. In comparison with the iron formations, the greatest degree of the escape is found in the Sokoman and Biwabik Iron Formations, the lowest degree in the Brockman Iron Formation, and the intermediate in the Gunflint Iron Formation. The variation of Fe/(Fe+Mg) in minnesotaite in each iron formation reflects that of oxygen fugacity during metamorphism. The ratio increases with decreasing oxygen fugacity. The fugacity change is probably due to the degree of consuming carbonaceous matters at constant temperature. Fe/(Fe+Mg) in greenalite probably reflects that in a primary one. Greenalite seems to be easily oxidized and to be decomposed to form iron talc with increasing PCO2 at lower temperatures because of very conservative substitution of Fe2+ by Mg. The ratios in siderite and ankerite do not change so significantly as that in minnesotaite, although no sufficient data is available. But they might have resulted from the ratios in carbonates, which were involved prior to recrystallization or ankeritization. It is therefore proposed that Fe/(Fe+Mg) in minnesotaite is a good indicator to reveal the magnitudes of partial pressures of oxygen and carbon dioxide during low-grade metamorphism of Precambrian iron formations.View full abstractDownload PDF (3308K) -
Yoshimasu Kuroda, Tetsuro Suzuoki, Sadao Matsuo, Hitoshi Onuki, Nobuhi ...1978 Volume 12 Issue 4 Pages 213-221
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe D/H ratios of hornblendes, epidotes, zoisites and white micas in the epidote-amphibolites from four localities in Japan have been determined together with the chemical compositions. The order of enrichment for deuterium in these minerals is as follows: epidote > white mica > hornblende > zoisite. A quite different situation for D/H ratios between coexisting zoisite and epidote is pointed out.View full abstractDownload PDF (2236K) -
Masana Morioka, Kunihiko Kigoshi1978 Volume 12 Issue 4 Pages 223-228
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe lead isotopic compositions and the uranium, thorium and lead contents of eclogite and harzburgite inclusions from South African kimberlite-pipes and lherzolite inclusions from Itinomegata crater, Japan and of their main mineral fractions have been determined. The observed 206Pb/204Pb, 207Pb/204Pb and 235U/204Pb in lherzolite samples from Itinomegata range from 17.9 to 18.2, from 15.1 to 15.5 and from 1.9 to 23, respectively. The results suggest that the lherzolites were of recent crystallization. The observed data on eclogite inclusions show no consistent pattern and suggest that they have a complicated history. The observed lead isotopic compositions of harzburgite inclusions from kimberlitepipes are 208Pb/204Pb = 17.3 ∼ 19.0 and 207Pb/204Pb = 15.3 ∼ 15.6. These results are distributed in a wide range on two regression lines, suggesting that they had been formed from the same source material but with different ages or have been formed recently by mixing of two different source materials and host rock of kimberlite.View full abstractDownload PDF (1964K) -
G. P. Glasby, R. R. Keays, P. C. Rankin1978 Volume 12 Issue 4 Pages 229-243
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSFour deep-sea manganese nodules and one fossil nodule from Timor have been analysed for 45 elements (major elements, rare earths and precious metals) by X-ray fluorescence, spark source mass spectrometry and neutron activation analysis. Co-existing sediments from two nodule sites in the Southwestern Pacific Basin have also been analysed. Differences in nodule composition are apparent, particularly for the Timor nodule. The trace metal compositions of this nodule, however, reveals it to be a typical deep-sea nodule, although some element redistribution has clearly taken place since exposure of the nodule on land. The distribution of a number of elements including Tl, Ir, Pd, Au and the rare earth elements between deep-sea nodules and their associated sediments appears to be dependent on a number of factors including the major element composition of the nodule (e.g. dilution by the silicate phase of the nodule), the differing stability of various element complexes in seawater, and the influence of differences in redox states on complex stability. Au and Si, on the other hand, are positively correlated in nodules and sediments possibly because they have a common source, either submarine detritus or basalt-seawater interaction. The rare earth contents of the sediments from the N.E. sector of the Southwestern Pacific Basin are high compared with previous determinations of rare earths in marine sediments and show no evidence of Ce depletion relative to La on a shale-normalised basis. These high contents reflect the well oxidised conditions and low sedimentation rates of this environment.View full abstractDownload PDF (4830K) -
Akimasa Masuda1978 Volume 12 Issue 4 Pages 245-251
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSWhen serial integers are allotted to REE corresponding to differences in their atomic numbers, markedly integral natures emerge for REE patterns of bulk rocks and for effective partition coefficient functions experimentally obtained. In addition, emphasis is placed on the skipping appearance of breaking position from an integer to another one and on ladder-like internal discontinuity of REE partitioning. These observations remind us of a kind of quantum effect. To account for those integral and simply linear features, a bulk-controlling transient stage is suggested to precede development of mineral assemblage as eventually observed in nature. Also it is suggested that the partial solidification and the partial melting cannot always stand in mutually reversible relation in effect.View full abstractDownload PDF (2234K) -
Shohei Banno, Saburo Chii1978 Volume 12 Issue 4 Pages 253-257
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSZonal structure of garnet grown in metamorphism maintaining surface equilibrium was examined on the model system Mn3Al2Si3O12-Fe3Al2Si3O12-H2O. The model assumes that the diffusion of Mn and Fe in both garnet and chlorite is limited, or it is practically negligible in garnet. It is shown that if the rate of temperature change during metamorphism is large in comparison with diffusion rate, a zonal structure, in which the MnO content of garnet decreases from the center of the crystal towards rim and increases again at the rim, giving rise to the minimum MnO content at an intermediate zone, can be formed without accompanying resorption. Two natural examples which support the conclusion on the model system are discussed.View full abstractDownload PDF (1544K) -
Yoshimasu Kuroda, Tetsuo Yamada, Katsuhiko Fujimoto, Tetsuro Suzuoki, ...1978 Volume 12 Issue 4 Pages 259-263
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSeveral specimens of coexisting biotite and hornblende were separated from the rapakivi granites, Svecofennian and Karelian granitic rocks of Finland and subjected to D/H ratio measurements and chemical analyses. D/H distribution between biotite and hornblende in the rapakivi and Svecofennian granitic rocks showed the disequilibrium situation defined by KURODA et al. (1977a). The origin of equilibrium and disequilibrium granites was discussed on the basis of the content and state of water in magmas.View full abstractDownload PDF (1507K) -
W. L. Raines, T. M. Flanders, P. K. Kuroda1978 Volume 12 Issue 4 Pages 265-270
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSA fission xenon component with isotopic composition resembling that of the Renazzo-type fission xenon (CCF) was released at 800 and 1, 200°C from a 17.971-gram sample of norite from Sudbury, Ontario, Canada. The presence of CCF was also noted in Wausau, Wisconsin, granite. The siderophilic superheavy elements (possibly Z = 114, 115, 116) may have decayed in the earth's iron core and the xenon isotopes became trapped in the crustal rocks. The results can also be explained, however, as due to the fact that the xenon isotopes produced by spontaneous fission of 238U were mass-fractionated and heavier xenon isotopes were preferentially released from the rocks at temperatures 800 to 1, 200°C.View full abstractDownload PDF (1302K) -
Surinder Singh, H. S. Virk1978 Volume 12 Issue 4 Pages 271-274
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSFission track geochronology of muscovite samples collected from some pegmatitic mines of Bhilwara and Ajmer districts of Rajasthan state (India) has been discussed. The ages obtained suggest the occurrence of Delhi Orogenic Cycle as the last major metamorphic activity in the region. The atomic fraction of uranium in muscovite samples is less than 1 p.p.b.View full abstractDownload PDF (1043K) -
Lin-gun Liu1978 Volume 12 Issue 4 Pages 275-277
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSPhase behaviours of kalsilite and its related potassium bearing aluminosilicates (orthoclase and leucite) have been investigated in the pressure region between 120 and 300kbar and at about 1, 000°C in a diamond-anvil press coupled with laser heating. Kalsilite, similar to leucite, has been found to decompose into a mixture of the hollandite-type KAlSi3O8 plus a proposed high-pressure form of KAlO2. The transition was observed at loading pressures greater than 170kbar, and it may be accompanied by a 46% increase in the zero-pressure density. Results of this study show that the hollandite-type KAlSi3O8 is the only so-far-known potassium bearing silicate which is stable under the lower mantle conditions.View full abstractDownload PDF (859K) -
N. G. Sumerlin, P. K. Kuroda1978 Volume 12 Issue 4 Pages 279-285
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSIsotopic compositions of xenon and krypton released from a sample of Belgian Congo pitchblende were measured mass-spectrometrically in stepwise heating experiments. Relative contributions from spontaneous fission of 238U, thermal neutron-induced fission of 235U and fast neutron-induced fission of 238U, to the production of fissiogenic xenon found in the ore were calculated to be 64.1, 18.8 and 17.1 percent, respectively.View full abstractDownload PDF (1461K) -
Katsuhiko Matsunaga, Sigeru Montani, Ryusuke Kobayashi, Yoshiaki Maita ...1978 Volume 12 Issue 4 Pages 287-291
Published: December 20, 1978
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSMercury and organic nitrogen were determined in sediment cores taken from the Okhotsk Sea and Funka Bay in northern Japan. The concentrations of mercury and organic nitrogen in the cores decrease from the surface to a nearly constant value below 20-50cm depth. Mercury is strongly correlated with organic nitrogen in each core, showing association of mercury with organic matter. Copper, zinc, iron and lead were also determined in some cores but showed no systematic variation with depth. Methylmercury both in interstitial waters and in solid phases was determined for some Funka Bay cores. The profiles appear to suggest that the mercury is lost from the sediments during early diagenesis by forming methylmercury or its sulfur derivatives.View full abstractDownload PDF (1178K)
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