F. Kluger

Rare earth element determinations at ultratrace abundance levels in geologic materials

The geochemically very important group of rare earth elements (REE) has frequently been analyzed with activation techniques. The importance of easy and quick techniques which are able to provide reliable data at very low abundance levels has been frequently discussed. We present three different methods using activation techniques yielding REE data at very low abundance levels in geologic materials. With proper selection of counting conditions and irradiations it is possible to use pure instrumental neutron activation analysis at ppb abundance levels (depending on the type of the material). A second method involves group separation of the REEs before irradiation, which yields data for all REEs, but is rather time consuming. The best results were obtained with a group separation after activation and several counting cycles, giving data for 8 REEs. This method has the advantage of providing results even in the sub-ppb range.

Synthese und Strukturanalyse von Na3SbSe3·3Sb2O3·0,5Sb(OH)3

Investigations in the “system” Sb-Se-NaOH-H2O, hydrothermal conditions, yielded crystals of the compound Na3SbSe3·3Sb2O3·0,5Sb(OH)3. The structure of this compound (a=14.40 Å,c=5.568 Å; space group P 63-C66;Z=2) was determined from 985 independent X-ray intensities — collected on an automaticWeissenberg type diffractometer — by thePatterson method and refined by the least squares method toR=8.3% (with σ-weighting 5.9%). The structure consists of SbO3 pyramids which are connected via common oxygen corners to “tubes” parallel [001]. These “tubes” and SbSe3 pyramids are combined by Na atoms to a framework. The Sb(OH)3 groups are statistically located within the channels of the “tubes”.

DETERMINATION OF BORON AT LOW ABUNDANCE LEVELS IN GEOLOGICAL MATERIALS WITH A TETRAFLUOROBORATE-SELECTIVE ELECTRODE

Abstract A modified procedure based on the tetrafluroborate-selective electrode is presented for the determination of low amounts of boron in geological materials. The main modifications are the use of hexamethylenetetramine as the buffer solution and a reduction of the temperature during measurement to 1–2°C to prevent hydrolysis; the latter precludes application of the usual method to solutions with low boron levels at very high total ionic strength. Satisfactory results can be obtained in the 10–200 μg g −1 range (by using up to 250 mg of sample) without much sample handling. The method was tested for the analysis of terrestrial rhyolites (from Lipari/Italy, and Iceland) and tektites (thailandite, and Muong Nong-type tektites).

A comparison between terrestrial impact glasses and lunar volcanic glasses: The case of fluorine

Abstract The genetic relationship between tektites (and several other terrestrial impact glasses) and lunar volcanic glasses has long been a point of discussion. With the aid of new fluorine data we try to furnish new evidence for the view that tektites are distinct from and bear no chemical relationships to lunar volcanic glasses. Since fluorine analyses are only rarely made for the kind of material in question, we discuss here our procedures of fluorine determinations with reference to methods newly developed in our laboratory. The first method involves ion sensitive electrode techniques, while the second uses rapid instrumental neutron activation analysis (RINAA). The results of our determinations of fluorine in tektites and other terrestrial impact glasses are presented and discussed together with data of lunar glasses acquired from the literature. The difference between the chemical behaviour of tektites and lunar glasses is also found in the fluorine data. It is shown that the expectation of high fluorine contents of tektites as it may be inferred from well documented high fluorine contents of lunar volcanic glasses as well as a possible connection between tektites and these glasses could not be sustained with the aid of chemical data. Thermodynamical data, calculated for conditions of lunar volcanoes, leads to the conclusion that several volatile elements are abundant during lunar lava fountaining and should correlate in volcanic glasses. Tektites fail to show these correlations, as it is pointed out with the aid of correlation analyses. Our data leads consequently to the conclusion that there are severe chemical differences between tektites and lunar volcanic glasses.