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: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633731
• 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.

大陆是经过数亿年进化而成的复杂构造集合体。地球上的大陆在地球历史上多次合并和分散，形成了“超大陆”大陆块。尽管在近代历史上，大陆的运动已经相当为人所知，但在回溯地质年代时，关于大陆在古代大陆块中的位置和作用的知识却变得越来越零碎。这个建议涉及一个独特的太古宙（超过25亿年）的地壳块，Rae克拉通，位于北美前寒武纪盾的中心，被称为劳伦西亚。在Laurentia内部，Rae克拉通被另外五个独特的太古宙块体所包围，这些块体在大约20亿年前聚集在一起，形成了地球上第一个超大陆“努纳”。Rae克拉通曾经被认为与它最近的邻居，赫恩克拉通相连，赫恩克拉通位于一个更古老的太古宙大陆，被称为“Kenorland”。然而，我们现在认识到Rae具有与Hearne不同的特殊特征，这表明它起源于一个独立的大陆“Nunavutia”。因此，Rae似乎是一个古老大陆（25至23亿年前的“努纳武蒂亚”）的一部分，在分裂之后，成为另一个大陆（20至18亿年前的“努纳”）的一部分。这项拟议中的研究将调查Rae克拉通的构造历史，以更好地了解它从努纳武蒂亚（Nunavutia）的起源地到后来大约20亿年前卷入努纳（Nuna）的过程。工作将集中在阿萨巴斯卡地区的西-西南Rae边缘，这是研究随着时间推移影响Rae的构造事件的绝佳实验室。主要目的是描述与25至23亿年前的造山期（阿罗史密斯造山运动）相关的构造活动，阿罗史密斯造山运动使雷伊岛与其他太古宙地块区别开来。这种更好的理解将有助于验证和更好地确定Rae从一个古代大陆到另一个古代大陆的旅行步骤。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。它还将揭示地球早期发育的一个重要时期，即古元古代早期（25亿至20亿年前），当时地球系统发生了重大变化，如大陆（海平面以上）的出现、大气的氧化作用、第一次重大冰川作用，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。