Absolute reconstructions of continents for one billion years: developing new quantitative approaches

十亿年来大陆的绝对重建：开发新的定量方法

• 批准号: RGPIN-2019-04780
• 负责人: Kravchinsky, Vadim
• 金额: $ 2.62万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737855
• 关键词: Absolute; reconstructions; continents; billion; years

Our understanding of Earth's plate kinematics and dynamics has evolved greatly in the last half-century, yet plate tectonic reconstructions prior to ~ 200 Ma remain challenging. The calculation of ancient longitudes of continental blocks is the most challenging problem in paleogeography. Conventional methods to determine paleolongitudes prior 200 Ma cannot be applied because ocean floor subduction has entirely erased all the records of marine magnetic anomalies, transform faults, and hotspot tracks that documented pre-200 Ma world kinematics. The estimated paleolongitude of continents for pre-Jurassic time must then be based on comparisons of fossils or lithofacies. These methods, however, can be used only for determining relative longitudes, whereas "true" or absolute positions of continental blocks and actual sizes of ancient oceans can be determined only when we are able to calculate ancient longitudes. My proposal deals with numerical assessments of absolute longitudes using four recent approaches that, although with some limitations, provide the best longitude evaluations: (1) stationary Africa as a longitudinal anchor, however, only since the Permian, (2) the position of subducted slabs in the mantle (only for the last ~ 250 Ma), (3) the hypothetical position stability of large low shear velocity provinces (LLSVPs) in Paleozoic and Neoproterozoic eras, with surficial expressions in large igneous and kimberlite provinces, (4) apparent polar wander path geometrical parameterization method that enables calculation of paleolongitudes but requires reliable paleomagnetic data to build an apparent polar wander path for a continent (such a database still needs to be built for particular ages and continental blocks, especially in Asia). Calculating paleolongitudes will enable me and my group to build a fully quantitative plate tectonic model of the world spanning from 200 to 1000 Ma. Implementation of such a model will ultimately give us the opportunity to further investigate outstanding questions in contemporary Earth sciences: the hypothesis of mantle stability at LLSVPs, the convective turnover of the mantle, which is related to the modulation of geodynamo and mantle degassing by changes in subduction flux, the opening and closing of ocean basins (the Wilson Cycle), the effect of such geological processes on long-term climate changes and geomagnetic field behavior.

在过去的半个世纪中，我们对地球板运动学和动力学的理解已经大大发展，但是在〜200 mA之前的板块构造重建仍然具有挑战性。大陆块的古代纵向计算是古地理学中最具挑战性的问题。确定古统一的常规方法无法应用200 MA，因为海底俯冲已完全消除了所有海洋磁异常的记录，变形故障和记录了200 MA世界运动学前的热点轨道。然后，夏季前时间的大陆的估计古质量必须基于化石或岩性的比较。但是，这些方法只能用于确定相对的纵向，而仅当我们能够计算古代纵向时，才能确定大陆块的“真实”或绝对位置。 我的提议处理了对绝对纵向的数值评估，尽管有一些局限性，这些方法提供了最佳的经度评估：（1）固定的非洲作为纵向锚点，但仅是自二叠纪以来，（2）（2）地幔中俯冲平板的位置（仅是最后一个低调的位置），（3）次数（3），（3）均为（3）的态度（3），（3）均为（3）的态度（3），（3）均为（3）均匀的位置（3）。 （LLSVP）在古生代和新元古代时代中，在大火成岩和金伯利特省具有表面表达，（4）明显的极地徘徊路径的几何参数化方法，可以计算出古征的计算，但需要对临界的范围构建，尤其需要构建的临界范围（尤其是构建的远景）（构建了一个偏极的范围（范围），以构建一个偏极范围（范围内徘徊）（在亚洲）。计算古管将使我和我的小组能够建立一个从200到1000 mA的世界的全定量板块构造模型。 Implementation of such a model will ultimately give us the opportunity to further investigate outstanding questions in contemporary Earth sciences: the hypothesis of mantle stability at LLSVPs, the convective turnover of the mantle, which is related to the modulation of geodynamo and mantle degassing by changes in subduction flux, the opening and closing of ocean basins (the Wilson Cycle), the effect of such geological processes on long-term climate changes and地磁场行为。