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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709248
• 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变而来的复杂的构造集合体。在地球历史上，地球上的大陆曾几次合并和分散，形成了超级大陆的大陆。虽然大陆的运动在近代史上是众所周知的，但追溯到地质时代，人们对大陆在古代陆地中的位置和作用的了解变得越来越零碎。这项提议涉及一个独特的太古宙(大于25亿年)地壳区块--拉埃克拉通，它位于北美前寒武纪地盾的中央，被称为劳伦蒂亚。在劳伦西亚，拉埃克拉通被另外五个独特的太古宙地块包围着，这些地块在大约20亿年前聚集在一起，形成了地球上第一个超级大陆--努纳。雷克拉通曾被认为与它最近的邻居赫恩克拉通相连，位于一块更古老的太古宙陆地上，被称为肯诺兰。然而，我们现在认识到，RAE具有与赫恩不同的特殊特征，表明它起源于一个独立的陆地，努纳武蒂亚。因此，RAE似乎是一个古老陆地(25亿至23亿年的“努纳武蒂亚”)的一部分，并在解体后并入另一个大陆(2.0至18亿年的“努纳”)。这项拟议的研究将调查拉埃克拉通的构造历史，以更好地了解它从努纳武蒂亚的发源地到大约20亿年前参与努纳的过程。工作将集中在阿萨巴斯卡地区的西南-西部RAE边缘，这是一个研究长期影响RAE的构造事件的优秀实验室。一个主要目的是描述与25亿至23亿年前的造山事件--Arrowsmith造山运动--相关的构造活动，这是Rae有别于其他太古代地块的地方。这种更好的理解将有助于验证和更好地确定RAE从一个古老大陆到另一个古老大陆的旅行步骤。在更广泛的范围内，这将有助于确定超级大陆的概念是否可以应用于前寒武纪，如果是的话，如何应用于前寒武纪。它还将揭示早期地球发展的一个重要时期--早期古元古代(25亿至20亿年前)，当时地球系统发生了重大变化，例如大陆(高于海平面)的出现、大气的氧气作用、第一次重大冰川以及地壳结构和构造样式的根本性变化，包括可能出现现代式板块构造。