Deep subduction in Earth history: Seeking for traces in the sedimentary record

地球历史中的深俯冲：寻找沉积记录中的痕迹

• 批准号: 428738884
• 负责人: Professor Dr. Hilmar von Eynatten
• 金额: --
• 依托单位: Abteilung Sedimentologie und Umweltgeologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/428738884?language=en
• 关键词: Deep; subduction; Earth; history; Seeking

Modern-style plate tectonics are characterized by cold (<350°C/GPa) and deep (>100 km) subduction. Its onset marks a major change in the history of planet Earth, the timing of which, however, is highly controversial ranging from Mesoarchean (3 Ga) to Neoproterozoic (1.0 to 0.7 Ga). A key evidence for modern-style plate tectonics is the occurrence of ultrahigh-pressure (UHP) rocks reflecting deep subduction of crustal material down to depths >100 km. Searching for UHP rocks is biased by the notoriously incomplete geological record and hampered by laborious and spatially inefficient techniques to detect UHP rocks. We have recently developed and tested a new approach capable to trace UHP rocks at the catchment scale using UHP inclusions in detrital minerals. This approach will be used to test our central hypothesis that deep subduction processes leading to UHP conditions already operated prior to the Neoproterozoic.The project is subdivided into two phases. The first phase is aimed at improving the new approach in order to develop a highly efficient technique to screen a region regarding the presence of UHP rocks. Sediment samples draining small to medium sized catchments will be analyzed from two regions, which show a variety of distinct UHP indicators, in particular coesite and/or microdiamond inclusions, from several host minerals and lithologies. The Erzgebirge in Germany as well as the Western Gneiss Region in Norway has been chosen because of extensive previous work, already existing mineral separates, and the demonstrated lithological diversity.The second phase is aimed at investigating two Paleoproterozoic regions, the Trans-Hudson Orogen in North-East Canada and the Nagssugtoqidian Orogen in West Greenland, where UHP conditions are indicated but not yet proven by irrefutable evidence such as coesite and/or microdiamond inclusions. Sediments from streams draining these regions will be screened for detrital minerals with UHP indicators applying the approach refined during the first phase. A successful project will (i) demonstrate that deep subduction processes already operated in the Paleoproterozoic, and (ii) allow for expanding regions and periods considered for UHP metamorphism in order to better constrain the timing of onset of modern-style plate tectonics on Earth.

现代风格的板块构造的特征是冷（<350°C/gpa）和深（> 100 km）俯冲。它的发作标志着地球历史上的重大变化，但是，从中间人（3ga）到新神经元（1.0至0.7 ga），其时机的争议性高度引起争议。现代板块构造的主要证据是发生了超高压（UHP）岩石，反映了地壳材料的深俯冲，深度> 100 km。臭名昭著的地质记录偏见，搜索UHP岩石是偏见的，并受到实验室和空间效率低下的技术来检测UHP岩石的障碍。我们最近开发并测试了一种能够在碎屑矿物中使用UHP夹杂物在集水量表中追踪UHP岩石的新方法。这种方法将用于检验我们的中心假设，即导致Neoperolosoic之前已经运行的深层俯冲过程。该项目被细分为两个阶段。第一阶段旨在改善新方法，以开发一种高效的技术来筛选有关UHP岩石存在的区域。从两个区域中分析了两个区域的沉积物样品，这些区域将分析来自几种宿主矿物质和岩性的两个不同的UHP指标，尤其是Coesite和/或Microdiamond夹杂物。由于先前的工作，已经存在了很小的较小分离和所证明的岩性多样性。诸如Coesite和/或Microdiamond夹杂物之类的证据。绘制这些区域的流中的沉积物将筛选用于使用UHP指标的碎屑矿物，并在第一阶段应用了该方法。一个成功的项目（i）将证明已经在古元古代中运行的深层俯冲过程，（ii）允许扩大对UHP变质化的区域和期间，以便更好地限制地球上现代板块构造的发作时间。