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Examination of igneous intrusions and related mineral deposits in eastern Mexico (including the determination of 26 new zircon U-Pb ages, 6 new mineral Ar-Ar ages and 26 new sulphide and feldspar Pb isotope and 61 new whole-rock geochemical data) revealed a spectrum of Eocene to Pleistocene mineral deposits and important aspects of the metallogenic history of Mexico. The synthesis of these data with recent tectonic reconstructions suggest the character of igneous rocks and mineral deposits was controlled by two periods of ocean ridge subduction and contemporaneous slab steepening and flattening. Mineralisation occurred in four epochs: (1) Eocene ~ 43 to 38 Ma Cu (Au) skarn and porphyry deposits in northeastern Mexico; (2) Miocene, ~18 to 9 Ma Cu (Au) porphyry, skarn and high-sulphidation epithermal deposits in the Trans Mexican Volcanic Belt (TMVB) and Oaxaca; (3) Pliocene ~ 4.5 Ma low-sulphidation epithermal deposits in the TMVB; and (4) Pliocene to Pleistocene ~ 2.5-2.0 Ma Cu (Au) skarn and porphyry deposits in Chiapas. The intrusions of the Eocene and Miocene epochs are high-K, have adakite-like geochemistry including Sr/Y up to ~108 and ~85 respectively and La/Yb ratios up to ~38 and ~27 respectively, and were followed by alkaline magmatism. All episodes of mineralisation are interpreted to have occurred above areas of slab steepening following periods of flat slab subduction. Shallow emplacement of Miocene ~ 9.0-8.0 Ma diorite stocks in the TMVB caused flashing of hydrothermal fluids, banded quartz vein formation and Au deposition which overprint potassic alteration and Cu-Au mineralisation. Barren quartz-alunite zones formed contemporaneously with potassic alteration at higher elevations. Later fluids deposited Au in some quartz-alunite zones. There is little difference in Pb isotope compositions of feldspar and sulphides or variation over time, their compositions ranging from 18.3208 to 19.1637 for 206Pb/204Pb, 15.4541 to 15.6675 for 207Pb/204Pb and 38.3096 to 39.2193 for 208Pb/204Pb. This may reflect similar tectonic environments and magma sources for Pb.

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Contamination often occurs as a result of metals and organic chemicals from industrial processes being deposited on land and in water. Quantification of contamination has traditionally involved measuring the concentration of chemicals present. However, this does not necessarily assess toxicity due to chemical interactions or assess that portion that is “bioavailable”. The work presented in this thesis uses the naturally bioluminescent bacterium <i>Vibrio fischeri </i>as the biosensor in bioassays to assess such toxicity. The growth of the bacterium was characterised and the methodology developed for preservation by freeze-drying. Quality control procedures were established. The response of rehydrated cells was investigated under different conditions, and the toxicity of a range of organic compounds and metals was measured under ideal conditions before progressing to environmental samples. This baseline testing was also used to determine the suitability of methanol as a solvent for biosensor testing and chemical analyses. A site where metal amended sludge cake had been added during a long-term field trial was assessed using the bioassay. Toxicity was shown to be attributable to pH and not metal concentrations. Samples from a contaminated foreshore were assessed with the bioassay and by chemical analysis using methanol as an extraction solvent. The <i>V. fischeri </i>bioassay was shown to be a robust procedure for toxicity assessments, vials of the freeze-dried cells were shown to have a 1 year shelf-life and offered a cost effective alternative to Microtox®. The developed bioassay should be specified in legislation for toxicity assessment particularly if future work demonstrates that it is a surrogate for higher organisms.