Evolution of the precambrian earth system through progressive oxidation of surface environments

前寒武纪地球系统通过表面环境的渐进氧化而演化

• 批准号: 342384-2007
• 负责人: Bekker, Andrey
• 金额: $ 1.72万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=365588
• 关键词: Evolution; precambrian; earth; system; through

The redox states of the atmosphere and ocean changed dramatically in the Precambrian.  The rise of atmospheric oxygen has been constrained, based on geological and geochemical evidence, to have occurred between ca. 2.45 and 2.32 Ga, during the assembly of the first supercontinent and a series of ca. 2.48-2.42 Ga mantle plume breakouts.  This sequence of events led to several perturbations in Earth's surface environment, including global glaciations followed by extreme greenhouse conditions, carbon isotope excursions in seawater composition, the rise of seawater sulfate content, and changes in the ocean redox state. Since these events affected surface environments globally, they have implications not only for the understanding the history and stability of the Earth System, but also for correlation between Paleoproterozoic basins that otherwise lack high precision geochronologic constraints.   On an applied level, understanding the redox evolution of the global Precambrian ocean may shed light on the development of uniquely Precambrian mineralization processes.  Giant sedimentary mineral deposits (e.g. iron formations, Mn-deposits, phosphorites, sulfates, and sedex deposits) reflect these non-actualistic states of the ocean redox state.  The deeper understanding of changes in redox state of the atmosphere and ocean will provide a predictive tool to search for giant sedimentary mineral deposits.   The funding will be used to support graduate-student work to develop a better temporal control and stratigraphic resolution over the evolution of surface environments in the Proterozoic.  By combining detrital zircon and xenotime geochronology with high-resolution chemostratigraphy, we will establish the temporal framework required to reliably correlate Paleoproterozoic successions, understand the evolution of the Earth System, and predict temporal distribution of giant sedimentary mineral deposits.   The results of this research will appeal to astrobiologists (Earth System stability), economic geologists, Precambrian geologists and stratigraphers.

大气和海洋的氧化还原状态在前寒武纪发生了巨大的变化。根据地质和地球化学证据，大气氧的上升被限制在大约2.45-2.32Ga之间，发生在第一个超大陆组装期间和一系列大约2.48-2.42Ga的地幔热柱爆发期间。这一系列事件导致了地球表面环境的几次扰动，包括全球冰川和极端温室条件，海水中碳同位素漂移，海水硫酸盐含量的上升，以及海洋氧化还原状态的变化。由于这些事件影响了全球地表环境，它们不仅对了解地球系统的历史和稳定性，而且对缺乏高精度地质年代学约束的古元古代盆地之间的对比也具有意义。从应用层面上讲，了解全球前寒武纪大洋的氧化还原演化可能有助于揭示独特的前寒武纪成矿作用的发展。以及大型沉积矿床(如铁建造、锰矿、磷矿、硫酸盐、和Sedex沉积物)反映了海洋氧化还原状态的这些非现实状态。更深入地了解大气和海洋氧化还原状态的变化将为寻找巨大的沉积矿床提供预测工具。这笔资金将用于支持研究生工作，以开发更好的时间控制和地层分辨率，以控制元古界地表环境的演化。通过将碎屑锆石和Xen-time年代学与高分辨率化学地层学相结合，我们将建立可靠地关联古元古代序列、了解地球系统演化所需的时间框架。并预测巨大沉积矿藏的时间分布。因此，这项研究的结果将吸引天体生物学家(地球系统稳定性)、经济地质学家、前寒武纪地质学家和地层学家。