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Subject: search.filters.subject.Iron meteorites

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    Quantification of gallium, indium and thallium in meteorites and other geological materials by graphite furnace atomic absorption spectrometry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1993) Guo, Xun
    Methods of solvent extraction have been developed for the determination of gallium, indium, and thallium in meteorites and other geological materials. The extraction of gallium is based on forming a chloro complex in HCl solution and extraction into MIBK. Indium was extracted into the same solvent as an iodo complex in an HBr + KI medium to which KOH had been added. Thallium was also extracted as an iodo complex from a H2SO4 + KI medium with addition of K2HPO4 as a salting out agent. Serious interference from iron(III) was eliminated by adding KI to reduce this element to its divalent state that was not extractable into the organic phase. Graphite furnace atomic absorption spectrometric techniques were employed to determine these three elements in the MIBK phase after extraction from the aqueous phase. Very low limits of detection (l.o.d.) were obtained with these methods. It was possible to lower the l.o.d for these elements either by increasing the aqueous/organic phase ratio before extraction, or by multiple loading injections. Using the developed methodology, gallium, indium, and thallium were quantified in iron and chondritic meteorites as well as in Cretaceous/Tertiary boundary clays, and some volcanic emissions. The data for thallium abundances in 49 iron meteorites were the first ever recorded for this type of meteorite and allowed for taxonomic separation of the various groups of irons. Indium abundances were only recorded in six chondrites because of the very low concentrations in iron meteorites. My data for thallium and other elements were used to classify the previously non-studied Manitouwabing iron meteorite. All three Group IIIA elements were determined in Cretaceous/Tertiary boundary clays and it was shown that these and other chalcophile elements have an abundance greater than that which would have been expected from either a volcanic or impact-derived source. Possible sources of this enrichment are discussed.
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    The platinum group metals in iron meteorites : thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry, Department of Chemistry and Biochemistry, Massey University, Palmerston North, New Zealand
    (Massey University, 1990) Hoashi, Maki
    Solvent extraction methods have been developed for the determination of Ru, Pd and Pt in iron meteorites. The method for Ru is based on the oxidation of this element in HCl solutions with sodium periodate followed by extraction of the tetroxide into CHCl3. The CHCl3 phase is then removed to a HNO3-NaIO4 "keeper" solution for storage up to 17 hours prior to analysis. The method for Pd and Pt entails simultaneous extraction of their stable iodocomplexes into methylisobutyl ketone after removal of Fe(III) as the chlorocomplex. The digestion of the samples with reference to these elements has also been investigated. All three elements were determined by the graphite furnace atomic absorption spectrometry technique. The limit of detection was lowered by increasing the volume of organic phase placed in the graphite furnace. The lowest absolute detection limits achieved in this study were 0.5 ng for Ru, 0.5 ng for Pd and 5 ng for Pt. The platinum group metal values for 108 authentic iron meteorites were subjected to Principal Components Analysis and Discriminant Analysis. These procedures confirmed the validity of the classification of iron meteorites developed over the past 25 years, but highlighted poor fits for some individual iron meteorites within a group. Possible reclassification of these members was evaluated after consideration of the meteorite's morphological features. The cases for the merging of some groups were investigated and discussed with reference to the chemical features of those groups. The data obtained also revealed several cases of meteorite pairings (related members of a single meteorite shower catalogued as separate meteorites), instances of the mislabelling of museum fragments and two putative meteorites which proved to consist of man-made materials.