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The onset of plate tectonics 3 billion years ago? - New insights from Ca-Sr-Pb-Nd isotopes and implications for large-scale crustal evolution

30亿年前板块构造开始了？

基本信息

批准号：
NE/K008862/1
负责人：
Bruno Dhuime
金额：
$ 65.94万
依托单位：
University of Bristol
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FK008862%2F1
关键词：
onset plate tectonics billion years

项目摘要

The continental crust is the archive of the processes and events that have controlled our planet's evolution for the last 4.4 billion years. Its formation modified the composition of the mantle and the atmosphere, it supports life, and it remains a sink for carbon dioxide through weathering and erosion. The continental crust has therefore had a key role in the evolution of the Earth, and yet the timing of its generation, and the processes that shaped its evolution, remain a topic of considerable debate.Views on the evolution of the continental crust have changed dramatically as ideas on geological processes have evolved and as methods to interrogate the rock record have advanced through developments in stratigraphic analysis, petrography, paleontology, geochemistry, geochronology, geophysics and modelling. Crucially our understanding of the processes involved in the generation and the evolution of the continental crust has grown enormously through the latter part of the 20th and beginning of the 21st centuries following on from the development and acceptance of plate tectonic theory.A fundamental question is to determine when plate tectonics started, and a few studies have recently argued that this major change in Earth's evolution may have happened 3 billion years ago during the Mesoarchaean. This model of Earth's evolution remains highly controversial and much debated by the community. The validation of this model is therefore a key step in understanding the large-scale evolution of the Earth, through repeated interaction between the mantle, the continental crust and the atmosphere. This proposal is to explore the processes of generation, maturation and growth of the continental crust through time, using a new geochemical approach based on the analysis of various isotopes systems with different geochemical properties and decay constants (K-Ca, Rb-Sr, U-Pb and Sm-Nd), in a large range of rocks, minerals and sediments with pre- and post-3 Ga ages. The data will allow to establish the composition of the continental crust at different stages of its evolution, as well as the variation in the balance between subduction-related and intraplate- related magmatism through time, with a confidence that has not been achieved hitherto. A sharp transition from intraplate-related to subduction-related magmas at 3 billion years ago, along with high rates of crust recycling from this time, would constitute clear evidence for the global onset of plate tectonics at this time.

大陆地壳是过去 44 亿年来控制地球演化的过程和事件的档案。它的形成改变了地幔和大气的成分，支持生命，并且通过风化和侵蚀仍然是二氧化碳的汇。因此，大陆地壳在地球的演化中发挥着关键作用，但其生成的时间以及形成其演化的过程仍然是一个颇有争议的话题。随着地质过程观念的演变以及随着地层分析、岩相学、古生物学、地球化学和地质学的发展，询问岩石记录的方法不断进步，关于大陆地壳演化的观点也发生了巨大的变化。地质年代学、地球物理学和建模。至关重要的是，随着板块构造理论的发展和接受，我们对大陆地壳的生成和演化过程的理解在 20 世纪末和 21 世纪初得到了巨大的发展。一个基本问题是确定板块构造何时开始，最近有一些研究认为，地球演化的这一重大变化可能发生在 30 亿年前的中太古代时期。这种地球演化模型仍然备受争议，并受到社会的广泛争论。因此，该模型的验证是理解地球通过地幔、大陆地壳和大气之间的反复相互作用进行大规模演化的关键一步。该提案旨在通过分析具有不同地球化学性质和衰变常数（K-Ca、Rb-Sr、U-Pb 和 Sm-Nd）的各种同位素系统（K-Ca、Rb-Sr、U-Pb 和 Sm-Nd），采用一种新的地球化学方法，探索大陆地壳随时间的生成、成熟和生长的过程，这些同位素系统存在于 3 Ga 年龄之前和之后的大范围岩石、矿物和沉积物中。这些数据将有助于确定大陆地壳在其演化的不同阶段的组成，以及俯冲相关和板内相关岩浆作用之间的平衡随时间的变化，其可信度迄今为止尚未实现。 30亿年前从板内相关岩浆到俯冲相关岩浆的急剧转变，以及此时地壳的高回收率，将构成此时全球板块构造开始的明确证据。