Molybdenum and Copper Isotope Systems as Petroleum and Paleoceanographic Tracers

随着多收集器电感耦合等离子体质谱法的出现，金属同位素系统已成为同位素地球化学的一个新的分支学科。然而，金属同位素作为油气源对比工具的发展尚处于探索阶段。本研究建议利用已充分研究的单一（瑞典Siljan地区）和多个（加拿大西部沉积盆地）烃源岩含油气系统，对钼和铜同位素系统作为油气示踪剂进行全面评价。实验产出的油（来自烃源岩的含水热解）将建立每个烃源岩的端元同位素组成，并揭示烃源岩与其产出的油之间是否发生同位素分馏。来自实验油和天然油以及潜在烃源岩的同位素和多元素数据将确定可追溯到主要烃源岩的油中的多代理地球化学特征。这项开创性的工作将为其他重要但不太了解的加拿大石油系统的应用铺平道路。烃源岩的同位素资料也可用于古海洋学。缺氧和硫化（含氧）黑色页岩的钼同位素组成可以作为古代海洋含氧和缺氧条件程度的示踪剂。然而，铜同位素的古海洋学应用还处于起步阶段。该研究将提供显生宙和前寒武纪黑色页岩铜同位素组成的第一个综合数据集，为评估古代铜生物地球化学循环的性质提供依据。铜和钼同位素数据的比较可能为过去当地和全球海洋氧化还原条件提供新的见解。这些数据将有助于确定元古代海洋中铜的缺乏是否延缓了反硝化作用，导致一氧化二氮引起的温室变暖，和/或减缓了真核生物的进化速度。关于显生宙早期海洋氧合程度的相互竞争的假设将使用钼和铜同位素数据进行测试。

With the advent of multi-collector inductively coupled plasma mass spectrometry, metal isotope systems have emerged as a new subdiscipline of isotope geochemistry. However, development of metal isotopes as an oil-oil and oil-source rock correlation tool is in the exploratory stage. This study proposes to fully assess the molybdenum and copper isotope systems as petroleum tracers using well-studied petroleum systems containing single (Siljan region, Sweden) and multiple (Western Canada Sedimentary Basin) source rocks. Experimentally produced oil (from hydrous pyrolysis of source rocks) will establish end-member isotopic compositions for each source rock and reveal if isotope fractionation occurs between a source rock and its produced oil. Isotope and multi-element data from experimental and natural oil, and potential source rock(s), will identify a multi-proxy geochemical signature in oils that can be traced to the major source rock(s). This pioneering work will pave the way for applications to other important but less-well-understood Canadian petroleum systems.Isotope data from source rocks can also be used for paleoceanography. It is well-established that molybdenum isotope compositions from anoxic and sulfidic (euxinic) black shales can be used as a tracer for the extent of oxygenated versus anoxic conditions in ancient oceans. However, paleoceanographic applications of copper isotopes are in their infancy. This study will provide the first comprehensive dataset of copper isotope compositions for Phanerozoic and Precambrian black shales, which will enable an assessment of the nature of ancient copper biogeochemical cycling. Comparisons of copper and molybdenum isotope data may shed new insights on past local and global ocean redox conditions. The data will help determine if copper scarcity in Proterozoic oceans retarded the operation of denitrification, resulting in nitrous oxide induced greenhouse warming, and/or slowed down the rate of eukaryotic evolution. Competing hypotheses for the extent of early Phanerozoic ocean oxygenation will be tested using molybdenum and copper isotope data.