Scott J. Mooney HBSc thesis abstract

Thesis Title: 
Geochemistry of Mica From Some Australian Lamproites and Some MARID-Suite Xenoliths, Bultfontein, South Africa
Scott J.

Phlogopite mineral separates from five samples of lamproite, three MARID suite rocks, and a sample of metasomatized lherzolite were studied with respect to major and trace elements as determined by instrumental neutron activation analysis.

High K/Cs ratios and similar K/Ba and Rb/Cs ratios were found in lamproitic samples whereas lower K/Cs and more variable ratios were found in MARID suite micas.  The elements Rb, K, Mn, and Co were similar but Sc, Cr, Cs, and Ba were significantly different for phlogopites from these two rock suites.  Most noteworthy are Cs and Ba, the former being less abundant in lamproites due to its large ionic radius and volatile nature, which is believed to be indicative of source differences between these rocks and those of MARID suite composition.  Any possible relationship must be complex in order to account for variations in geochemical nature found with respect to phlogopite mineral separates.

In addition, amphibole and clinopyroxene mineral separates were prepared from the MARID suite samples.  These were analysed for REE by radiochemical neutron activation analysis using the oxalate precipitation method.  Instumental neutron activation analysis data was used in the determination of chemical yield for this experiment.

Similar REE distribution patterns were produced to those determined by Kramers et al. (1983).  The clinopyroxenes contain a much higher absolute abundance of the REE and define a much wider range of REE enrichment than was obtained by Kramers et al. (1983).  Two liquids of different REE content but with similar elemental ratios are thought to have generated the MARID suite composition.  This is believed to have occurred by open system crystallization with loss of a fugitive phase from an intital melt approximating kimberlite composition (Kramers et al., 1983).