The formation of the continental crust in the early Earth, and the geodynamics that drove it, are fundamental to understanding the evolution of our planet, but remain intensely debated. Here, we analysed 148 archived zircon separates of magmatic rocks for in-situ zircon U-Pb-Hf-O-trace element data, and compiled published geochronological, whole-rock geochemical and Sm-Nd isotopic data from across the south-east Superior Craton, Canada. We combine these data spatially and temporally to investigate the crustal evolution of this part of the craton in the Neoarchean, with a view to understanding its tectonic setting. In terms of zircon data, at >2704–2695 Ma, the central and north-west Abitibi demonstrate more juvenile εHf, light to mantle-like δ¹⁸O, lower (Eu/Eu*)/Y (drier/shallower crust), reduced ΔFMQ, less continental initial-U (U_i)/Yb, and more mantle-like U_i/Nb, relative to surrounding crust, which contains older, ca. 2800–2750 Ma inherited and magmatic zircon ages. Furthermore, whole-rock Sr/Y and La/Sm demonstrate the presence of a high Sr/Y TTG component (mainly intrusive) surrounding zones of low Sr/Y (mainly volcanic) component, the latter of which shows contamination trends with Mesoarchean crust. We interpret this to represent a continental-rift setting, driven by plume magmatism as represented by multiple komatiite suites. At ca. 2704–2695 Ma, there is a marked transition in multiple datasets, including; increases in δ¹⁸O, (Eu/Eu*)/Y, ΔFMQ, U_i/Yb and U_i/Nb data, together with more distinct arc-like trace element trends, suggesting a transition to north-dipping subduction. This process closed the rift system and initiated orogenesis. Subsequently, this study constrains the geodynamic setting which formed the majority of Neoarchean continental crust in the south-east Superior Craton, and the timing at which it transitioned to subduction. If these findings are replicated in other cratons, it suggests that plate tectonics was active by, or started at, ca. 2.7 Ga.

早期地球大陆壳的形成，以及推动其发展的地球动力学，对于理解我们星球的演化至关重要，但仍存在激烈的争论。在这里，我们分析了148个已归档的岩浆岩锆石分离物，以获取原位锆石U-Pb-Hf-O-痕量元素数据，并汇总了来自东南上等地区的已出版的地质年代学，全岩地球化学和Sm-Nd同位素数据加拿大克雷顿。我们将这些数据在空间和时间上结合起来，以研究新纪元时期克拉通这部分的地壳演化，以期了解其构造背景。在锆石的数据而言，在> 2604至95年马，所述中央阿比提和西北部证明更少年εHf，光到地幔状δ ¹⁸O，相对于周围的地壳，其（Eu / Eu *）/ Y（干燥的/浅地壳），ΔFMQ减小，大陆初始U（U _i）/ Yb减少，而地幔样U _i / Nb则更多年长的 2800–2750 Ma继承了锆石和岩浆时代。此外，全岩Sr / Y和La / Sm证实了低Sr / Y（主要是火山岩）成分周围存在高Sr / Y TTG成分（主要是侵入性），后者显示出中初生地壳的污染趋势。我们将其解释为代表大陆裂谷背景，这是由羽状岩浆作用驱动的，该岩浆作用由多个科马蒂岩组代表。约于 2704–2695 Ma，多个数据集中存在明显的过渡，包括：增加δ ¹⁸ O，（EU /铕*）/ Y，ΔFMQ，U_我/镱和U_i / Nb数据以及更明显的弧状痕量元素趋势，表明向北倾俯冲转变。这个过程关闭了裂谷系统并开始造山。随后，这项研究限制了东南上克拉顿地区形成大部分新阿尔巴西亚大陆壳的地球动力学环境及其过渡到俯冲的时间。如果将这些发现复制到其他克拉通中，则表明板块构造是在大约20年前就开始活动的。2.7加仑