This thesis concerns the application of a new technique for measuring the stable isotopes of Sr, specifically pertaining to mass dependent fractionation in high temperature processes on the Earth and Moon. Processes such as mantle melting and differentiation on Earth and the formation of the Lunar Magma Ocean are investigated by the application of a double-spike TIMS method to terrestrial and lunar material to obtain high-precision <sup>87</sup>Sr/<sup>86</sup>Sr, <sup>88</sup>Sr/<sup>86</sup>Sr and <sup>84</sup>Sr/<sup>86</sup>Sr data. Measurements of mantle-derived mafic material provide insights into the <sup>88</sup>Sr/<sup>86</sup>Sr composition of the silicate mantle. Ocean Island Basalts possess restricted δ<sup>88</sup>Sr compositions, whilst Mid-Ocean Ridge Basalts from the Pacific, Atlantic and Indian ridges reveal variations in δ<sup>88</sup>Sr, the majority of which is seen within the FAMOUS section of the Mid-Atlantic Ridge. These variations are attributed partly due to the effects of plagioclase crystallisation and partly due to mantle source heterogeneity. Analyses of mineral separates from three different igneous systems provide an understanding of δ<sup>88</sup>Sr fractionation at a mineral-scale. The possibility of δ<sup>88</sup>Sr fractionation as a result of magmatic differentiation has also been assessed, and found to occur between the basalt and rhyolitic end-members of the Icelandic Hekla suite. Variations in the <sup>87</sup>Sr/<sup>86</sup>Sr ratios of these rocks are also found, and considered most likely to be due to contamination. Analyses of lunar rocks indicate that the highland suite appears to be relatively uniform in δ<sup>88</sup>Sr, whilst significant fractionation to light δ<sup>88</sup>Sr compositions occurs in the mare basalts. Such variations are thought to be associated with the crystallisation of plagioclase during the differentiation of the lunar magma ocean. Lastly, precise <sup>87</sup>Rb/<sup>86</sup>Sr and <sup>87</sup>Sr/<sup>86</sup>Sr data yield a model age for the Moon of 4.523 ± 0.019 Ga.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:618436 |
| Date | January 2013 |
| Creators | Sutcliffe, Nadine C. |
| Contributors | Burton, Kevin W.; Halliday, Alex N.; Porcelli, Don |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:826ae843-3115-4a3e-975a-f6306f923d4e |
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