Tomoko Ossaka

Boron isotopic compositions of some boron minerals

Abstract Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the 11 B 10 B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher 11 B 10 B ratios than those of nonmarine origin. It has been found that the sequence of decreasing 11 B 10 B values among the minerals with the same geologic origin is; borax, tincal, kernite (Na borates) > ulexite ( Na Ca borate) > colemanite, iyoite, meyerhofferite (Ca borates). This sequence is explainable on the basis of the difference in crystal structure among the minerals. That is, minerals with higher BO 3 BO 4 ratios, (the ratio of the number of the BO3 triangle units to the number of the BO4 tetrahedron units in the structural formula of a mineral) have higher 11 B 10 B ratios.

Determination of rare earth elements in hot spring and crater lake waters by epithermal neutron activation analysis

Determination of the rare earth elements (REEs) in acidic hot spring and crater lake waters by neutron activation analysis (NAA), in which activation was performed mostly by epithermal neutrons (epithermal NAA) was investigated. Nine REEs, La, Ce, Sm, Eu, Tb, Ho, Tm, Yb and Lu, out of fourteen naturally existing REEs were determined at ppb levels with satisfactory precision. The epithermal NAA was found to be more effective in the determination of Sm, Tb, Ho and Yb than normal NAA, in which activation was performed mainly by thermal neutrons. Combined use of the epithermal and normal NAAs enabled the determination of eleven REEs, La, Ce, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu.

Experimental Studies on the Mobility of Lanthanides Accompanying Alteration of Andesite by Acidic Hot Spring Water

Abstract The mobility of lanthanides (Lns) accompanying interactions of powdered andesitic rocks with acidic hot spring water and acidic hot spring water vapor/steam was studied in the experiments set up in the field. At the early stage of rock alteration, light Lns were slightly easier to be leached out by acidic hot spring waters from andesitic rocks than heavy Lns. This result qualitatively agreed with the result obtained in the previous experiments carried out in the laboratory. It was also found that the Ln abundance patterns (Ln patterns) obtained by normalization with Ln contents of the original rock showed slightly positive Eu anomalies at the early stage of rock alteration and turned to show negative Eu anomalies and the extent of negative anomaly monotonously increased as rock alteration proceeded. This trend in the direction of Eu anomaly was correlated to the degrees of decompositions of major rock-forming minerals and interstitial materials in the rock. At the earliest stage of rock alteration in acidic environments, the interstitial materials with relatively low Eu contents were decomposed, which resulted in the positive Eu anomaly. In the following stage, feldspar that had a relatively high Eu content was decomposed, which led to the negative Eu anomaly.

Determination of rare earth elements in hot spring water and crater lake water samples by neutron activation analysis incorporating coprecipitation process using aluminium as a collector

Hot spring water and crater lake water samples were analyzed for their rare earth elements: (REEs) by neutron activation method, which, in the irradiation, sample preparation, incorporated a coprecipitation process in which aluminium was used as a collector. Ten REEs, La, Ce, Sm, Eu, Gd, Tb, Dy, Tm, Yb and Lu, were consequently detected and determined at the ppb level with satisfactory precision. It was shown that the aluminium coprecipitation is effective in enhancing concentrations of the REEs and reducing the amounts of interfering nuclides before neutron irradiation.

Extraction of boron from GSJ rock reference samples and determination of their boron isotopic ratios.

Abstract The extraction of boron from rocks by methyl borate distillation after alkali fushion was studied. Reproducible extraction was obtained when the ratio of the amounts of flux and rock was ⩾5:1. Isotope dilution experiments showed there was no appreciable boron isotope fractionation during the extraction under these conditions. 11 B/ 10 B ratios for three standard rocks were 4.044–4.047.

Determination of the lanthanoids in a neutral hot spring water by neutron activation analysis

Determination of the lanthanoids in a neutral hot spring water has been studied by menas of neutron activation analysis. The aluminium coprecipitation process, which used aluminium as the collector of the lanthanoids, was incorporated in the preparation of a sample for irradiation. Nine lanthanoids, La, Ce, Nd, Sm, Eu, Tb, Tm, Yb and Lu, were determined at ppt levels with satisfactory precision, indicating the effectiveness of aluminium coprecipitation.

DETERMINATION OF PRASEODYMIUM, NEODYMIUM AND ERBIUM IN HOT SPRING AND CRATER LAKE WATERS BY NEUTRON ACTIVATION ANALYSIS INCORPORATING THE STANDARD ADDITION TECHNIQUE

Previously undetermined three rare earth elements (REEs), Pr, Nd and Er, in acidic hot spring and crater lake waters were determined at ppb levels by neutron actavation analysis with the standard addition technique. Errors on final detemined values were 7.1–56%. Combining the present results and the results previously obtained amounts to the determination of all 14 naturally occuring REEs in the waters.

Determination of thorium and uranium in hot spring and crater lake waters by neutron activation analysis

Determination of Th and U in acidic hot spring and crater lake waters was investigated by neutron activation analysis (NAA). Before neutron irradiation, Th and U were preconcentrated and separated from interfering nuclides such as alkali metals and halogens by coprecipitation with aluminium. Irradiation was carried out in two ways, viz., irradiation with Cd foil wrapping (epithermal NAA) and irradiation without Cd foil wrapping (normal NAA). The final determined values of Th and U were at ppb levels. Higher reliability of the determined values was obtained for Th than for U. It was found that epithermal NAA was more effective for the determination of these two actinides than normal NAA and was more effective for the determination of U than that of Th.

Nondestructive neutron activation analysis of rare earth elements in hot spring water samples in Kusatsu-shirane area, Japan

Hot spring water samples have been analyzed for their rare earth elements (REEs) determination by the nondestructive neutron activation method. Five REEs, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REEs, however, some pretreatment of the samples will be necessary.

Natural Boron Isotope Fractionation between Hot Spring Water and Rock in Direct Contact

The boron isotopic ratios, 11B/10B, of a hot spring water and a rock which were expected to have been in direct contact with each other in nature were measured mass spectrometrically. The water showed a larger 11B/10B value than the rock and the value of the separation factor between the two was 1.013. The observed result was consistent with what was theoretically expected.