The Eoarchean Isua supracrustal belt (ISB) has been interpreted as one of the earliest records of subduction processes, leading to the conclusion that a plate tectonic geodynamic system was likely operating since the early Archean. However, proposed tectonic models remain difficult to evaluate as our understanding of the metamorphic and structural evolution remains fragmentary. Here, we present a metamorphic study of the supracrustal rocks of the ISB. We used petrographic and microstructural observations, phase equilibria, isopleth geothermobarometry, and conventional thermometry to explore the prograde, peak, and retrograde metamorphic evolution of the northeastern ISB. Our results show that the ISB records a syn‐tectonic, amphibolite facies metamorphic event (M₁) with peak conditions of 550°C–600°C and 0.5–0.7 GPa. M₁ was followed by a static, lower amphibolite facies metamorphic event (M₂; <540°C and <0.5 GPa). Published constraints suggest that M₁ and M₂ occurred in the late Eoarchean (>3.5 Ga) and the Neoarchean (<2.9 Ga), respectively. These events are partially overprinted by late low temperature (<500°C) retrogression (M₃) that is most intensely developed in the northeastern part of the belt; it typically overprints some peak mineral phases while preserving the peak fabric. Our findings are consistent with spatially homogeneous syn‐tectonic amphibolite facies metamorphism and macroscale folding. Such features are predicted by a heat‐pipe tectonic model. Therefore, our findings permit the interpretation of the ISB as a record of early nonuniformitarian tectonic processes.

中文翻译：

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Isua上地壳带的构造1：多变质地层的P‐T‐X‐d约束

Eoarchean Isua上地壳带（ISB）被解释为俯冲过程的最早记录之一，从而得出的结论是，自太古宙早期以来，板块构造地球动力系统很可能正在运行。然而，由于我们对变质和构造演化的理解仍然是零碎的，因此拟议的构造模型仍然难以评估。在这里，我们介绍了ISB上壳岩的变质作用研究。我们使用了岩相学和微观结构观测，相平衡，等值地热气压计和常规测温法来探索东北ISB的前移，峰值和逆行变质演化。我们的结果表明，ISB记录了一个构造，闪石相变质事件（M ₁）的峰值条件为550°C–600°C和0.5–0.7 GPa。M ₁之后是静态的，较低的闪石相变质事件（M ₂； <540°C和<0.5 GPa）。已公布的约束条件表明，M ₁和M _2分别发生在Eoarchean晚期（> 3.5 Ga）和Neoarchean（<2.9 Ga）中。这些事件被低温（<500°C）后期倒退（M ₃）在该带的东北部发展最为迅速；它通常会覆盖某些峰值矿物相，同时保留峰值织物。我们的发现与空间均匀的构造-闪变岩相变质作用和宏观折叠相一致。这些特征可以通过热管构造模型来预测。因此，我们的发现允许将ISB解释为早期非均匀构造过程的记录。