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.

现代板块构造的特点是冷（<350°C/GPa）和深（>100公里）俯冲。它的爆发标志着地球历史上的一个重大变化，然而，它的时间是非常有争议的，从中太古代（1.3 Ga）到新元古代（1.0至0.7 Ga）。现代板块构造的一个关键证据是超高压（UHP）岩石的出现，反映了深度超过100公里的地壳物质的深俯冲。寻找超高压岩石是有偏见的臭名昭著的不完整的地质记录，并阻碍了费力和空间效率低下的技术来检测超高压岩石。我们最近开发和测试了一种新的方法，能够跟踪超高压岩石在流域尺度上使用超高压夹杂物碎屑矿物。这种方法将被用来测试我们的中心假设，深俯冲过程导致超高压条件已经运作之前，新元古代。第一阶段的目标是改进新方法，以开发一种高效的技术来筛选存在超高压岩石的区域。将对两个区域的中小型集水区的沉积物样品进行分析，这些样品显示出各种不同的超高压指标，特别是柯石英和/或微金刚石夹杂物，来自几种寄主矿物和岩性。选择德国的厄尔士山脉和挪威的西部片麻岩区是因为大量的前期工作，已经存在的矿物分离，以及已证明的岩性多样性。第二阶段的目的是调查两个古元古代地区，加拿大东北部的Trans-Hudson造山带和西格陵兰的Nagssugtoqidian造山带，其中指示了超高压条件，但尚未通过不可辩驳的证据（例如柯石英和/或微金刚石夹杂物）证明。将采用第一阶段改进的方法，对这些地区河流的沉积物进行超高压指标的碎屑矿物筛选。一个成功的项目将（i）证明深俯冲过程已经在古元古代运作，（ii）允许扩大超高压变质作用的区域和时期，以更好地限制地球上现代风格的板块构造的开始时间。