Diffusion profiles of ¹⁸O tracer in single crystals of forsterite following anneals at 1100° and 1200°C have been determined by a depth profiling technique using secondary ion mass spectrometry. The diffusion penetration profiles showed error function forms with developed tails. The profiles were analyzed in terms of diffusion in the forsterite lattice together with a contribution from dislocation. The present results of lattice diffusion lie in the range of the extrapolation of lines on Arrhenius plots reported previously for intracrystalline diffusion in forsterite. The dislocation diffusion coefficients are about 10⁴ times faster than the lattice diffusion at the same temperature. Diffusion along the dislocations takes place within a pipe with radius of about 0.1 nm surrounding the dislocation line. Based on the above results, O diffusion along high diffusivity paths, such as dislocations and grain boundaries, play an important role on the diffusional creep in olivine under laboratory condition.

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To investigate a fine structure of the ³He/⁴He ratio distribution in and around a single volcano, fumarolic gases, geothermal gases and waters were collected at 13 sites within the caldera of the Hakone volcano, Japan. The ³He/⁴He and ⁴He/²⁰Ne ratios vary from 6.7 × 10^-6 to 9.6 × 10^-6, and 0.85 to 26, respectively. The ³He/⁴He ratios, corrected for air contamination, of samples within the caldera are uniform and as high as those of magmatic fluids in the Japanese Islands. The ³He/⁴He ratios of two geothermal water samples outside the caldera are significantly lower than those of inside. The observed ³He/⁴He ratio distribution is interpreted as an indication of the presence of source magma with a high ³He/⁴He ratio beneath the volcanic region.

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The stony spherules collected from deep-sea sediments were analyzed for rare earth elements (REE) by direct-loading mass spectrometric isotope dilution together with examination of their petrographic characteristics. Abundances of some major and trace elements including Fe, Co, Ni, Ir, and Au were also determined by instrumental neutron activation analysis. One spherule, which does not show deep-sea alteration, exhibits a flat REE pattern (1.8 × CI chondrite) with no specific anomaly. Relatively high Ni, Ir, and Au abundances in several spherules also confirm that they are of extraterrestrial origin. On the other hand, the altered spherules show highly fractionated, light REE enriched patterns with large negative Ce and minor negative Eu anomalies. Most of the stony spherules extracted magnetically from deep-sea sediments are extraterrestrial in origin and may have been derived from unfractionated chondritic material, but they are affected by deep-sea alteration during residence on the seafloor.

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Concentrations of uranium and other elements in bauxite deposit from Yangwa mine at Jiaozuo area in Henan Province, China, were determined, and geochemical behavior of ²³⁴U and sedimentation process were studied by leaching experiments. An inverse correlation between two major components, Al₂O₃ and Fe₂O₃, was observed. Al₂O₃ has a distinct correlation with Ti, Cr, U and V, while Fe₂O₃ correlated with Mn, Ca and Cu. Cr, V and U were enriched in the deposit compared with crustal abundance, while SiO₂, MnO, MgO, CaO, Na₂O, Cu, Sr and Ba were depleted. In phase extraction experiments, the Fe, Mn, Mg, Ca, and Sr were predominantly in the “HCl soluble fraction”. With one exception, most of the U in the bauxite was in the “HF soluble fraction” (∼60%), and ∼30% of the U was in the “resistate fraction”. The ²³⁴U/²³⁸U activity ratios in these fractions were less than unity, and have a good correlation with the fractional U content. This relation suggests that ²³⁴U was leached out from the surface of the U-containing mineral grains. In comparison, the activity ratios of HCl soluble U were more than unity, and are inversely correlated with the fractional U contents. This suggests that an almost constant amount of mobile ²³⁴U was present in the deposits. The principal bauxite ore body could be thought to be sedimentary in origin: A terra rossa was formed on the karstic Ordovician limestone. It was rich in Fe₂O₃, which suggests relatively oxidative sedimentary condition. The clay minerals, fine-grained materials originated from Pre-Cambrian basement were then transported and deposited repeatedly on the terra rossa. The deposition of the clay minerals changed the sink from oxidative to reducing condition, favoring for the deposition of U. The original clay minerals in the bauxite deposit were kaolinite and gibbsite. As the reversible change from kaolinite to gibbsite depends on the H₄SiO₄ concentration, the alteration degree of gibbsite might have been controlled by the movement of H₄SiO₄. ²³⁴U was estimated to have been ejected from the surface of U-containing minerals and migrated through the ore deposits, then adsorbed by iron hydroxides at the bottom of the ore body.

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The changes with time in carbon isotopic compositions of CH₄ and CO₂ in steam discharged from wells in the Matsukawa geothermal system were examined. δ¹³C(CH₄) values are comparatively uniform for all wells, and stable over a period of seven years. On the other hand, two groups of wells classified based on gas composition, degree of rock alteration and reservoir pressure have distinct features in δ¹³C(CO₂) values. The δ¹³C(CO₂) values of samples from wells drilled into the north and east regions of the exploitation area, which are weakly altered and have low reservoir pressures, are lower and variable (−4 to −11‰ relative to PDB) as compared with those of the central region (−5 to −7‰ relative to PDB). This is assumed to be caused by the incursion of isotopically light CO₂ of organic origin into the low pressure geothermal reservoir in the peripheral regions. The carbon isotope exchange reaction between CO₂ and CH₄ may not be fast, so that the δ¹³C(CH₄) values remain constant after the mixing with the isotopically light CO₂.

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Isotopic ratios and elemental abundances of rare earth elements (REE), Rb, Sr, Zr, Mo, Ru, Pd, Ag, Te, Ba and U in four samples from two Oklo Reactor Zones 7, 8, 9 and 10 were determined by thermal ionization mass spectrometry. These elements have unusual but reasonable isotopic anomalies due to the effect of fission and/or neutron capture reactions. In order to discuss the retentivity of fissiogenic nuclides, the fission product yield curves covering the wide mass range from 90 to 160 were reconstructed on the basis of our results. We have estimated the behavior of fissiogenic nuclides by means of the differences between the measured curves and empirical ones. From comparison of these two sets of curves, measured and empirical, the behaviors of fissiogenic nuclides were deduced. Our results are in agreement with previous Oklo work at the following points: (I) Ru, Pd, Te and most of a series of REE (except for La and/or Ce) have been well retained in the samples, (II) Rb, Sr and Ba have been lost to a great extent, and their isotopic ratios are nearly the same as those of terrestrial standard values, and (III) Zr, Mo and Ag have been partially removed from the reactors. The behaviors of Zr and Mo seem to have been highly affected by the chemical and geological environments in and around the reactors. The present work reveals that, among REE, La and Ce might have been partially removed in contrast to the good retention of other REE. Also, there is a possible remobilization of ⁹⁰Sr during operation of the Oklo reactors.

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Eleven of the rare earth elements (lanthanide series) have been determined in fifteen Geological Survey of Japan igneous reference samples by high performance ion chromatography (HPIC). Multiple analysis of each reference sample was undertaken to provide the best possible data. The technique, which employs chelating agents to permit the separation of individual rare-earth elements as anionic complexes, has a reproducibility of <4%. With the use of on-line sample solution concentration, detection limits of 0.1 ppb were possible, enabling the satisfactory analysis of rare-earth element impoverished samples such as feldspars JF-1 and JF-2, and peridotite JP-1. The results for the very well characterised sample JB-1 are in close agreement with published recommended values. Whereas our results for JG-1 and thirteen currently available members of the second “Igneous rock series” are generally in broad agreement with published values, in a majority of cases there are significant differences in one or more elements. In each case where significant discrepancy exists, the smooth and highly coherent patterns of the HPIC data when plotted on chondrite-normalised rare-earth element diagrams, contrasts with the more erratic patterns for the published values, suggesting the likely greater accuracy of the HPIC data.

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