Tectonic evolution of the WSW Rae craton, Athabasca region, Canada: Laboratory for study of Precambrian crustal processes

加拿大阿萨巴斯卡地区 WSW Rae 克拉通的构造演化：前寒武纪地壳过程研究实验室

• 批准号: RGPIN-2016-05320
• 负责人: Bethune, Kathryn
• 金额: $ 1.75万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=645375
• 关键词: Tectonic; evolution; WSW; Rae; craton

Continents are complex tectonic aggregations that have evolved over hundreds of millions of years. The continents of the earth have coalesced and dispersed several times in earth's history forming ‘supercontinental' landmasses. Whereas the movements of the continents are fairly well known in recent history, knowledge of their positions and roles in ancient landmasses becomes increasingly fragmentary going back in geological time. This proposal deals with a distinctive Archean (greater than 2.5 billion year) crustal block, the Rae craton, located centrally in the Precambrian shield of North America, known as Laurentia. Within Laurentia, the Rae craton is surrounded by five other distinctive Archean blocks that were assembled ~2 billion years ago to form Earth's first supercontinent, ‘Nuna'. Rae craton was once thought to be connected to its nearest neighbour, the Hearne craton, in an even older Archean landmass known as ‘Kenorland'. However, we now recognize that the Rae has special characteristics, distinctive from the Hearne, suggesting that it originated from an independent landmass, ‘Nunavutia'. The Rae therefore appears to have been part of one ancient landmass (2.5 to 2.3 billion year 'Nunavutia') and, following break-up, became incorporated in another (2.0 to 1.8 billion year old 'Nuna'). The proposed research will investigate the tectonic history of Rae craton to better understand its journey from its place of origin within Nunavutia to its later involvement in Nuna about 2 billion years ago. Work will focus along the west-southwest Rae margin in the Athabasca region, an excellent laboratory for study of tectonic events that affected the Rae through time. A major aim is to characterize tectonic activity associated with a 2.5 to 2.3 billion-year-old mountain-building episode, the Arrowsmith orogeny, which sets Rae apart from other Archean blocks. This improved understanding will serve both to verify and better establish steps in Rae's travels from one ancient landmass to the other. On a broader scale, this will help determine whether, and if so how, the supercontinental concept can be applied to the Precambrian. It will also shed light on an important period in early earth development, the early Paleoproterozoic (2.5 to 2.0 billion years ago), when significant changes occurred in the earth system such as the emergence of the continents (above sea level), oxygenation of the atmosphere, the first significant glaciations, as well as fundamental changes in crustal architecture and tectonic style, including the probable onset of modern-style plate tectonics.**

大陆是经过数亿年演化的复杂构造聚合体。在地球历史上，地球的大陆曾多次合并和分散，形成“超大陆”陆地。尽管大陆的运动在近代历史中已广为人知，但追溯到地质时代，关于大陆在古代大陆中的位置和作用的知识却变得越来越零散。该提案涉及一个独特的太古代（超过 25 亿年）地壳块，Rae 克拉通，位于北美前寒武纪地盾的中心，称为劳伦西亚。在劳伦大陆内，雷伊克拉通周围环绕着另外五个独特的太古宙地块，这些地块在约 20 亿年前聚集在一起，形成了地球上第一个超级大陆“努纳”。雷伊克拉通曾经被认为与其最近的邻居赫恩克拉通相连，赫恩克拉通位于一个更古老的太古代大陆，被称为“肯诺兰”。然而，我们现在认识到雷伊河具有与赫恩河不同的特殊特征，这表明它起源于一个独立的陆地“努纳武蒂亚”。因此，雷伊河似乎是一块古老大陆（距今 2.5 至 23 亿年的“努纳武特”）的一部分，并在分裂后并入另一块（距今 2.0 至 18 亿年的“努纳”）。拟议的研究将调查雷伊克拉通的构造历史，以更好地了解其从努纳武特地区的起源地到大约 20 亿年前后来卷入努纳的旅程。工作将集中在阿萨巴斯卡地区的西西南雷伊边缘，这是研究随时间影响雷伊的构造事件的优秀实验室。主要目的是描述与 2.5 至 23 亿年前的造山活动（阿罗史密斯造山运动）相关的构造活动特征，这使雷伊有别于其他太古代地块。这种加深的理解将有助于验证和更好地确定雷伊从一个古老大陆到另一个大陆旅行的步骤。在更广泛的范围内，这将有助于确定超大陆概念是否可以应用于前寒武纪，如果可以的话，如何应用于前寒武纪。它还将揭示地球早期发展的一个重要时期，即古元古代早期（2.5至20亿年前），当时地球系统发生了重大变化，例如大陆的出现（海平面以上）、大气的氧化、第一次显着的冰川作用，以及地壳结构和构造风格的根本变化，包括现代板块构造的可能开始。 **