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的出现，金属同位素体系已成为同位素地球化学的一个新的分支学科。然而，金属同位素作为一种油-油和油源岩对比工具的开发还处于探索阶段。这项研究建议利用研究充分的含单一(瑞典锡尔扬地区)和多(加拿大西部沉积盆地)源岩的石油系统，全面评估作为石油示踪剂的钼和铜同位素系统。实验生产的石油(来自源岩的水合热解)将建立每一源岩的端元同位素组成，并揭示源岩与其产出油之间是否发生同位素分馏。来自实验石油和天然石油以及潜在源岩(S)的同位素和多元素数据将识别石油中可追溯到主要源岩(S)的多代理地球化学特征。这项开创性的工作将为应用于其他重要但鲜为人知的加拿大石油系统铺平道路。来自源岩的同位素数据也可以用于古海洋学。众所周知，来自缺氧和硫化(正辛酸)黑色页岩的钼同位素组成可以作为古代海洋中氧化与缺氧条件的示踪剂。然而，铜同位素在古海洋学中的应用还处于初级阶段。这项研究将提供显生界和前寒武纪黑色页岩铜同位素组成的第一个全面数据集，这将使评估古代铜生物地球化学循环的性质成为可能。铜和钼同位素数据的比较可能会对过去当地和全球海洋的氧化还原条件提供新的见解。这些数据将有助于确定元古界海洋中铜的稀缺是否延缓了反硝化作用的进行，导致了一氧化二氮引起的温室效应变暖，和/或减缓了真核生物的进化速度。关于早期显生界海洋氧化程度的相互竞争的假设将使用钼和铜同位素数据进行验证。

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.