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Title: RE–OS and PGE geochemistry of organic-rich sedimentary rocks and petroleum
Author: Finlay, Alexander James
ISNI:       0000 0004 2684 8413
Awarding Body: Durham University
Current Institution: Durham University
Date of Award: 2010
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The research in this thesis is presented in paper format with each of four chapters representing one complete study. Chapter two presents Re–Os and geochemical fingerprint data for UK Atlantic margin oils. organic and δ13C geochemical data demonstrate that the oil is sourced from Upper Jurassic marine shales and the Re–Os data yields an age of 68 ± 13 Ma. Comparison of this date with published basin histories and Ar-Ar geochronology demonstrate that Re–Os ages correspond with the timing of oil generation. Furthermore the similarities between oil and source rock 187Os/188Os at the time of oil generation (Osg) indicates that Osg can be used to identify oil source units. Chapter three demonstrates, through the analysis of Kimmeridge Clay Fm. core and North Sea oil, that unradiogenic mantle like values within oils from wells in the Viking Graben and East Shetland Basin cannot be inherited from source. It is hypothesised that they are caused by contamination by a hydrothermal fluid sourced from either Cenozoic intrusive units or the mantle. Strain localisation is suggested to have caused the main basin bounding faults within the Viking Graben and East Shetland Basin to be of sufficient depth to act as conduits for hydrothermal fluid to propagate through and contaminate oils within reservoirs. Chapter four investigates how Osi values across the Ordovician/Silurian boundary GSSP at Dob’s Linn, Scotland, tracks the Hirnantian glaciation within a globally important source unit: the Ordovician/Silurian “Hot” Shales. During the Late Katian, Osi values increase from 0.28 – 1.08, providing evidence for increased silicate weathering of radiogenic continental crust. A decrease to less radiogenic Osi (~0.60) occurs at the base Hirnantian and marks the onset of the Hirnantian Glaciation. This is ascribed to Hirnantian ice cover and reduced chemical weathering rates cutting the supply of radiogenic material. In the Late Hirnantian an abrupt increase in Osi values to ~1.1 over 19 cm of stratigraphy, is attributed to the leaching of exposed radiogenic glacial deposits and increased weathering of silicate terrane during deglaciation. Chapter five applies the Platinum Group Elements, specifically Pt/Pd ratios, to identify oil source units. It is demonstrated that asphaltenes from the well constrained UK Atlantic margin petroleum system contain similar Pt/Pd and Osg values to the known source unit. A further study of the poorly constrained West Canadian Tar Sands demonstrates that Pt/Pd ratios in source rocks are not affected by hydrocarbon maturation and are distinct between differing potential source units. Comparison of the Tar Sands with potential source units demonstrates that the Tar Sands are mainly sourced from the Lower Jurassic Gordondale Fm., with minor input from the Devonian/Mississippian Exshaw Fm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available