Molybdenum and Copper Isotope Systems as Petroleum and Paleoceanographic Tracers

随着多接收电感耦合等离子体质谱技术的出现，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-油、油-源岩对比工具的开发还处于探索阶段。本研究建议充分评估钼和铜同位素系统作为石油示踪剂使用研究良好的石油系统，包含单一（西尔扬地区，瑞典）和多个（加拿大西部沉积盆地）源岩。实验生产的石油（来自源岩的含水热解）将建立每种源岩的端元同位素组成，并揭示源岩和其生产的石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源岩的同位素和多元素数据将确定可追溯到主要源岩的油中的多代用地球化学特征。这项开创性的工作将为应用于其他重要但不太了解的加拿大石油系统铺平道路。 烃源岩的同位素数据也可用于古海洋学。这是公认的，从缺氧和硫化物（富氧）黑色页岩的钼同位素组成，可用作古海洋的氧化与缺氧条件的程度的示踪剂。然而，铜同位素在古海洋学中的应用还处于起步阶段。这项研究将提供第一个全面的数据集铜同位素组成的古生界和前寒武纪黑色页岩，这将使古代铜地球化学循环的性质进行评估。铜和钼同位素数据的比较可能会对过去的局部和全球海洋氧化还原条件产生新的见解。这些数据将有助于确定元古代海洋中铜的稀缺是否阻碍了反硝化作用的运作，导致一氧化二氮诱导的温室效应，和/或减缓了真核生物的进化速度。将使用钼和铜的同位素数据来检验关于早古生代海洋氧化程度的相互竞争的假设。

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.