W. Kiesl

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.

Determination of trace elements by chemical analysis and neutron activation in meteorites of the collection of the viennese museum of natural history

In the present paper a thorough analysis is described of six olivine-hypersthene chondrites, one pyroxene-plagioclase-achondrite, one medium and one coarse octahedrite as well as of an ataxite of high nickel content.

Wet-chemical analysis and determination of trace elements by neutron activation in meteorites

As a contribution to the cosmochemical distribution of elements, 35 meteorites of the collections of the Museum of Natural History in Vienna, the Mineralogical-Petrographical Institute and the Analytical Institute of the University of Vienna were analyzed. In the meteorites main and minor constituents were determined by wet-chemical methods, whereas for the determination of about 16 trace elements neutron activation analysis was employed.

Neutronenaktivierungsanalytische Bestimmung einiger Spurenelemente in meteoritischen Phasen

ZusammenfassungDie Verteilung von Spurenelementen über die vier Hauptphasen von Eisenmeteoriten (Metall-, Phosphid-, Graphit- und Sulfidphase) wurde mittels Neutronenaktivierung untersucht. Aus den Verteilungsverhältnissen ergibt sich ein stark chalkophiles Verhalten für Se und Cr, hingegen stark siderophiles Verhalten für die Elemente Sb und As. Überraschenderweise ist der Hauptteil des Mo im Schreibersit vertreten. Mit Ausnahme der Elemente Cr und Mo sind im übrigen alle von uns untersuchten Elemente in jenen Phasen vertreten, die auch in Chondriten auftreten. Aus den von uns erstmals durchgeführten umfassenden Analysen ergeben sich somit gewisse Konsequenzen für die Affinitätsänderungen dieser Elemente während der Entstehung und Genesis des meteoritischen Materials.SummaryThe distribution of trace elements over four main phases of iron meteorites (metallic-, phosphidic-, graphitic- sulfidic phases) was investigated by means of neutron activation.A strong chalcophilic behavior for selenium and chromium was deduced from the distribution circumstances, as opposed to strong siderophilic behavior for the elements antimony and arsenic. Most surprisingly, the main part of the molybdenum is present in the form of schreibersite. With the exception of the elements chromium and molybdenum, all of the other elements studied by the writers are represented in those phases that also occur in chondrites Hence certain consequences with regard to the affinity changes of these elements during the creation and genesis of the meteoritic material are disclosed by the comprehensive analyses conducted for the first time by the authors.

Chemical and microprobe investigations of the Allende-meteorite

SummaryResults of chemical and radiochemical bulk-analysis of main-, minor- and trace elements in the Allende meteorite are with the only exception of Hg in good agreement with respect to mean values characteristic for C III chondrites. Mineralogical and petrographical investigation shows three distinct components: chondrules and irregular white aggregates embedded in a fine grained black matrix. Electron microprobe analyses were performed on silicate, metal, sulfide and oxide grains. The chondrules consist mainly of Mg-rich olivine, furthermore of clinoenstatite, anorthite, Ca-Al-rich glass and minute amounts of metal and sulfide. A marked feature is the separation of metal into kamacite and taenite, the presence of awaruite- (∼ Ni3Fe) and of taenite-grains, which are surrounded of a goethitelike oxide. The white aggregates are a fine grained agglomeration of Ca-Al-rich minerals, e. g. spinel, augite, gehlenite, anorthite, and diopside. Informations about the composition of matrix were obtained by analysis using a defocused electron beam. The Allende meteorite belongs to the not- or only slightly equilibrated chondrites and has not been metamorphosed by action of shock or temperature during history. The white aggregates represent primary condensation products of the solar nebula. The conversion of troilite by the action of water vapor is suggested as a possible mechanism for the formation of the goethitelike mineral.ZusammenfassungDie chemische und radiochemische Analyse des Allende-Meteorits auf Haupt- und Nebenbestandteile sowie Spuren ergibt mit Ausnahme von Hg gute Übereinstimmung mit den Werten, die für C III Chondrite charakteristisch sind. Eine mineralogissh-petrographische Untersuchung zeigt Chondren und sogenannte weiße Aggrsgate, die in eine feinkörnige Matrix eingebettet sind. An den silikatischen, metallischen, sulfidischen und oxydischen Bestandteilen wurden Analysen mit der Elektronenstrahl-Mikrosonde ausgeführt. Die Chondren bestehen hauptsächlich aus Mg-reichem Olivin, ferner aus Klinoenstatit, Anorthit, Ca-Al-reichem Glas sowie etwas Metall und Sulfid. Ungewöhnlich ist die Trennung des NiFe in Kamazit und Taenit, das Auftreten von Awaruit (∼ Ni3Fe) und Taenitkörnern, die von einem goethitähnlichen Oxid umgeben sind. Die weißen Aggregate sind eine feinkörnige Agglomeration von Ca-Al-reichen Mineralen, hauptsächlich Spinell, Augit, Gehlenit, Anorthit und Diopsid. Informationen über die Zusammensetzung der Matrix wurden durch Analyse mit einem defokussierten Elektronenstrahl erhalten. Der Allende-Meteorit gehört zu den nicht äquilibrierten Chondriten und hat im Verlaufe seiner Geschichte keine thermische oder Schockmetamorphose erlitten. Die weißen Aggregate sind primäre, schnell abgekühlte Kondensate aus dem solaren Urnebel. Für die Entstehung des goethitähnlichen Minerals wird eine Reaktion von Troilit mit Wasserdampf vorgeschlagen.

Aktivierungsanalytische Bestimmung von Spurenelementen in Steinmeteoriten

SummaryA method is described for the isolation of trace quantities of selenium, arsenic, antimony, tin, and mercury from meteorites and minerals after preliminary activation of the samples in a reactor core followed by the distillation of the halides from the matrix materials. In the distillate selenium is first precipitated in the presence of strong hydrochloric acid using sulphur dioxide as reducing agent. Further separation is effected on the anion exchanger Dowex 1-X8. On this resin antimony, tin and mercury are retained while in the effluent arsenic is precipitated as trisulphide and then subjected to measurement. For the separation of the adsorbed elements antimony, tin and mercury two different techniques are discussed. In one case antimony is eluted with aqueous 10% ascorbic acid solution 0.4 N in hydrochloric acid and in the other, which appears to be more advantageous, an aqueous 10% solution of ammonium fluoride 0.5 N in hydrochloric acid is employed. Subsequently in both cases tin and mercury are removed from the resin using 22 N orthophosphoric acid and nitric acid (normality not below 7 N), respectively. The recoveries of this separation method have also been determined radiochemically.ZusammenfassungEs wird ein Arbeitsgang beschrieben, der es gestattet, die Spurenelemente Selen, Arsen, Antimon, Zinn und Quecksilber in Meteoriten und Mineralen nach einer vorhergehenden Aktivierung im Core eines Reaktors und nach Destillation ihrer Halogenide aus der Matrix voneinander zu trennen und quantitativ zu erfassen. Aus dem Destillat wird dazu vorerst aus starker Salzsäure das Selen mit Schwefeldioxid gefällt. Die weitere Trennung erfolgt über einen Anionenaustauscher Dowex 1-X8. An diesem werden Antimon, Zinn und Quecksilber adsorbiert, während Arsen im Effluenten als Arsentrisulfid gefällt und gemessen wird. Für die Trennung der am Austauscher adsorbierten Elemente Antimon, Zinn und Quecksilber werden zwei Arbeitsmethoden diskutiert. Nach der einen wird Antimon mit 10%iger Ascorbinsäure in 0,4 n HCl eluiert, nach der anderen weit vorteilhafter mit 10%iger Ammoniumnfluoridlösung, die 0,5 n an HCl ist. Anschließend wird in beiden Fällen Zinn mit 22 n H3PO4 und Quecksilber mit mindestens 7 n HNO3 eluiert. Für den Trennungsgang wurden auch die Ausbeuten radiochemisch bestimmt.

ACTIVATION ANALYTICAL DETERMINATION OF ELEMENTS IN METEORITES.

Abstract A method for neutron activation analysis has been worked out for determination of the elements Mn, Na, Ga, Cu, Au, and Cr, present in seven stony and three iron meteorites. The chemical separation was carried out by means of the anion exchanger Dowex 1, X8. Using finely powdered meteoritic material, about 50-mg samples are sufficient for a single analysis. In the case of iron meteorites, somewhat larger amounts of material are recommended.

Meteorites and the High-Temperature Origin of Terrestrial Planets

In this paper the authors try to relate their own investigations on the chemical composition of meteorites, as well as petrography, mineralogy and age relationships. From these, and from the monistic theory of the origin of the solar system which is today generally admitted, it seems that the planets were condensed or accreted in a period of a fully convective early protosun, which may have had a luminosity of some orders of magnitude higher than the present sun, thus producing very high temperatures in the inner regions of the solar system. A possible mechanism for the origin of carbonaceous chondrites is also given.

Activation analytical determination of elements in meteorites, 2: Determination of manganese, sodium, gallium, copper, gold and chromium in 21 meteorites

Abstract The elements Mn, Na, Ga, Cu, Au and Cr were determined in 21 meteorites using neutron activation analysis. For the chemical separation the anion exchanger Dowex 1,X8 was employed. For each analysis 70–110 mg of the finely ground stony meteorites and 100–150 mg of the iron meteorites, respectively, were used. The results are compared in part with those obtained by other authors.

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.