The Nagssugtoqidian orogen (NO), which forms the northern margin of the North Atlantic craton in West Greenland, is largely comprised of ~2870 to 2720 Ma juvenile continental crust reworked during Paleoproterozoic orogenic events. Sparse evidence of components older than 3100 Ma in the area (U–Pb zircon ages and bulk-rock Sm–Nd isotopes) have hinted at a unit called the Qorlortoq gneiss but were not substantiated by regional studies. Here we report the “rediscovery” of the Qorlortoq gneiss, documented through a new geochemical and geochronological dataset of this orthogneiss and related components, which include ultramafic cumulate enclaves and late basaltic dykes. Laser Ablation Split Stream (LASS) U-Pb/Lu-Hf isotopic analyses of zircon from the gneiss give a U–Pb concordia upper-intercept age of 3177 ± 12 Ma and weighted mean εHf(t) of 1.7 ± 0.5, indicating a juvenile protolith extracted from a depleted mantle source.

Ultramafic enclaves of cumulate origin make up a key component of the Qorlortoq gneiss. Their trace element systematics indicate a parental melt with tholeiitic affinities, sourced from depleted mantle beneath relatively thin lithosphere (<80 km), that was subsequently contaminated by crustal assimilation. Re–Os isotope systematics of the cumulates and their relationship with the younger Qorlortoq dykes place the age of these cumulates close to that of the Qorlortoq gneiss.

The age of the Qorlortoq gneiss makes it the oldest known component in the NO by ~300 Ma. The extended timescale between episodes of crustal production in this area, could indicate a geodynamic environment characterized by stagnant-lid or episodic mobile-lid tectonics, at least on a regional scale. These constraints provide important information about the diversity and nature of Archean geodynamic environments.

Nagssugtoqidian造山带（NO）形成了西格陵兰岛北大西洋克拉通的北缘，主要由古元古代造山过程中经过重造的约2870至2720 Ma幼年大陆壳组成。该地区（U–Pb锆石年龄和块状岩石Sm–Nd同位素）年龄大于3100 Ma的稀疏证据暗示了一个名为Qorlortoq片麻岩的单元，但并未得到区域研究的证实。在这里，我们报告了Qorlortoq片麻岩的“重新发现”，这是通过该正片麻岩和相关成分（包括超镁铁质聚积飞地和晚玄武岩脉）的新地球化学和年代学数据集记录的。片麻岩锆石的激光烧蚀分流（LASS）U-Pb / Lu-Hf同位素分析显示，U-Pb concordia的截距上限年龄为3177±12 Ma，加权平均εHf（t）为1.7±0.5，

累积的超镁铁质飞地构成了Qorlortoq片麻岩的关键组成部分。他们的痕量元素系统表明，具有亲和力的母体熔体来自相对薄的岩石圈（<80 km）下的枯竭地幔，随后被地壳同化污染。–的Re-Os同位素系统及其与年轻的Qorlortoq岩脉的关系使这些堆积物的年龄接近Qorlortoq片麻岩的年龄。

Qorlortoq片麻岩的年龄使其成为NO中最古老的已知成分，距今约300 Ma。该地区地壳生产事件之间时间尺度的延长，可能表明至少在区域尺度上以停滞的盖层或偶发的活动盖层构造为特征的地球动力学环境。这些约束条件提供了有关太古宙地球动力学环境的多样性和性质的重要信息。