| Summary: | Degree: Doctor of Philosophy Abstract: Different laser ablation and mass spectrometry techniques and FTIR spectroscopy have been used to investigate elemental impurities, defects, and stable and radiogenic isotope compositions in natural diamond and ruby, with the aim of expanding previous research into diamond and ruby genesis, aiding exploration efforts and developing techniques to “fingerprint†a gemstone’s origin. First I use FTIR and SIMS techniques to evaluate the basis for using microdiamonds as grade predictors for diamond deposits. Predictions of the macrodiamond grade of newly discovered kimberlites are commonly obtained using size frequency distributions of microdiamonds, based on the implicit assumption of a genetic relationship between all diamonds across the entire size range. Despite the success of this approach, such a genetic relationship between microdiamonds and macrodiamonds has not been placed on a sound scientific footing. In contrast to previous comparative studies on microdiamonds and macrodiamonds from single deposits, here all diamonds analyzed – from the Misery deposit, Northwest Territories, Canada - originate from the same microdiamond bulk sample (558 diamonds; ranging in size from 0.212 to 3.35 mm). The diamonds were analyzed for their carbon isotopic compositions and nitrogen aggregation and concentration characteristics, and based on this dataset statistical comparisons were conducted across the size range to assess cogenesis. Overall, a general geochemical similarity of diamonds from across the different size fractions was established, reinforcing the use of size-frequency analysis to predict diamond grade in kimberlite diamond deposits. A novel off-line laser sampling technique has been applied to analyzing high purity diamonds. Quantitative trace element data from high-purity gem diamonds from the Victor Mine, Ontario, as well as near-gem diamonds from peridotite and eclogite xenoliths from the Finsch and Newlands mines, South Africa, acquired using an “offline†...
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