Hideo Higuchi

Trace element partition between two pyroxenes and the host lava

Partition coefficients for +1, +2, +3 and +4 valent trace ions between alkaline olivine basalt lava and the coexisting ortho- and clinopyroxene phenocrysts from Takashima, North Kyushu, Japan, have been determined by neutron activation analysis. Substitution of trace elements in crystal lattice sites is proposed for the mechanism of trace element partition by examining the relation between measured partition coefficients and ionic radius and ionic charge.

PARTITION OF TRACE ELEMENTS BETWEEN ROCK-FORMING MINERALS AND THE HOST VOLCANIC ROCKS.

Abstract Partition coefficients for +1 to +4 valent trace ions between ground mass of volcanic rocks and the coexisting phenocrysts of plagioclase, biotite, hornblende and olivine have been determined by neutron activation analysis. The result supports the mechanism proposed by Onuma et al. [1] that the trace element partition between phenocryst and ground mass is determined by crystal structure of the phenocryst.

Rare earths in peridotite nodules: An explanation of the genetic relationship between basalt and peridotite nodules

Rare earth abundances in peridotite (lherzolite) nodules and mineral fractions separated from them were measures by neutron activation analysis. Rare earths in a possible liquid phase which could have equilibrated with the nodules were calculated on the basis of trace element partition. In comparing these calculated patterns with those of the actual basalts, it is suggested that the nodules would have no genetic relationship to host basalts but would be fragments of deep-seated peridotite masses which had once supplied basaltic magma.

Determination of rare-earth elements in rock samples by neutron activation analysis with a lithium-drifted germanium detector after chemical group-separation

Abstract A lithium-drifted germanium detector combined with chemical group-separation has been utilized for the determination of rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb and Lu) in rock samples by neutron activation. This procedure has the advantage of a low background level which cannot be attained in the non-destructive method. The combination of the Ge(Li) detector and chemical group-separation also offers a distinct simplification in the correction of contributions from other nuclides. For optimum utility of a Ge(Li) detector in neutron activation analysis, chemical group-separations are recommended.

Variation of rare earth concentrations in pigeonitic and hypersthenic rock series from Izu-Hakone region, Japan

The abundances of rare earth elements in 5 each of aphyric volcanic rocks of pigeonitic and hypersthenic rock series from Izu-Hakone region have been determined by neutron activation analysis. Pigeonitic rock series show rare earth patterns with relative depletion of lighter rare earths (low lanthanum type) and large increase in rare earth abundances with differentiation. Hypersthenic rock series show higher lanthanum abundances (high lanthanum type) compared with pigeonitic rock series. The differences in rare earth patterns between two rock series are compatible with the theory of independent magmatic generation of these two series. Variation of rare earth patterns in both series have been examined by a model of magmatic differentiation based on the observed rare earth partition coefficients.

RAPID DETERMINATION OF DYSPROSIUM IN ROCK SAMPLES BY NEUTRON ACTIVATION ANALYSIS WITH A Ge(Li) DETECTOR AFTER CHEMICAL SEPARATION.

Abstract A neutron activation method for the rapid determination of dysprosium in rocks, based on simple chemical separation and γ-spectrometry with a lithiumdrifted germanium detector, is described. The 94.7-keV photopeak of dysprosium-165 (2.3 h half-life) was measured. Several geochemical standard rocks covering a variety of rock types were analyzed. The detection limit was 0.005 μg of dysprosium. A precision of ±4.7% was obtained on 7 separate analyses of a basalt standard rock. The accuracy of the method is discussed.

Determination of rare-earth eleemnts in rock samples by neutron activation analysis

A Ge(Li) detector combined with cation exchange separation has been used for the determination of 12 rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, and Lu) in rock samples by neutron activation analysis. After purification by the conventional hydroxide-fluoride precipitation, the rare-earth elements are separated into two fractions, light (La-Tb) and heavy (Ho-Lu), by EDTA cation exchange, and the γ-activities of the two fractions are measured by a Ge(Li) detector. The heavy rare-earths, such as Ho, Er, and Tm, can be easily γ-counted without serious interference from the intense Compton background and photopeaks due to the light rare-earths such as140La,153Sm,152Eu, and160Tb. The chemical yields (60%) for the individual rare-earths are determined by a reactivation technique. The results obtained for the U.S. Geological Survey standard rocks G-1 and W-1 are compared with the previously reported data.

Simultaneous determination of Strontium and Barium by Neutron activation analysis with a Ge(Li) detector

Abstract A method is described for the simultaneous determinations of strontium and barium in rock samples by neutron activation analysis with a Ge(Li) detector after chemical group-separation. The re-activation technique was employed to obtain the chemical yields for both elements without any additional chemical treatment. The values obtained for several geochemical standard rocks (G-1, W-1, G-2, GSP-1,AGV-I and BCR-1) are in reasonable agreement with previously published data.

Determination of sodium and chlorine in pure water by neutron activation analysis

Neutron activation analysis was applied to determine sodium and chlorine in high purity water samples. After irradiation of the sample,38Cl was purified from82Br and other nuclides by carbon tetrachloride extraction and silver chloride precipitation, and24Na was separated from other alkali elements and other nuclides by adsorption of24Na on HAP. The activities of both elements were measured by conventional G.M. counter. The contamination of the elements from container walls during neutron irradiation and the interference with38Ar(n, p)38Cl reaction on argon dissolved in water were also examined. Water samples containing 3 ppb of chlorine could not be determined accurately, owing to the above mentioned interfering reaction.