We use zircon U-Pb, Hf and O isotopes to constrain the depositional ages and provenance of metasedimentary rocks of the Paleoproterozoic Karrat Group of West Greenland and to understand the tectonic processes leading to basin development on the eastern Rae craton. An older supracrustal assemblage (Qeqertarssuaq complex) deposited after ca. 2.6 Ga is separated by an unconformity with a younger supracrustal assemblage (the Karrat Group). The Qaarsukassak Formation at the base of the Karrat Group was deposited after ca. 2.0 Ga, with dominantly Archean age modes. The youngest siliciclastic rocks (Nûkavsak and Mârmorilik formations) in the Karrat Group have maximum depositional ages ranging from ca. 1980 to 1950 to 1900 Ma and contain dominant detrital zircon age modes between ca. 2.50 and 1.93 Ga. A ca. 1.92 Ga supracrustal assemblage referred to as the northern domain (Karrat Group, sensu lato) is geographically separated from the Karrat Group (sensu stricto) by the Prøven igneous complex. The stratigraphy and detrital zircon profiles are compared to broadly coeval sedimentary units on the Rae craton and a unifying model of their deposition is presented. The Rae craton is the dominant detritus source; initially these sources were mostly local, changing to a mix of local and distal sources including the western Rae craton. The tectonic setting of the Karrat basin transitioned from extensional to convergent to collisional during its basin evolution, reflecting Wilson cycle phases within an epeiric sea. Accordingly, zircon Hf isotopes in our dataset track the evolution of the opening and closing of the Manikewan Ocean. Detrital zircon Hf isotopes in our dataset reveal a greater proportion of juvenile detritus (especially ca. 2.15–1.95 Ga) than is known from the currently exposed crustal record, pointing to the importance of the detrital zircon record for understanding Paleoproterozoic crustal and tectonic evolution.

中文翻译：

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西格陵兰古元古代卡拉特群和 Rinkian 褶皱带表壳岩石的地质年代学（锆石 U-Pb、Hf、O 同位素）、物源分析和构造环境


我们利用锆石 U-Pb、Hf 和 O 同位素来约束西格陵兰古元古代卡拉特群变沉积岩的沉积时代和物源，并了解导致 Rae 克拉通东部盆地发育的构造过程。一个较古老的表层组合（Qeqertarssuaq 复合体）大约在 1970 年之后沉积。 2.6 Ga 被一个不整合面与较年轻的表壳组合（卡拉特群）分开。卡拉特群 (Karrat Group) 底部的卡苏卡萨克 (Qaarsukassak) 地层是在大约2.0 Ga，以太古宙年龄模式为主。卡拉特群中最年轻的硅质碎屑岩（Nûkavsak 和 Mârmorilik 地层）的最大沉积年龄约为 100 年。 1980年至1950年至1900 Ma之间，包含主要的碎屑锆石年龄模式。 2.50 和 1.93 Ga.A 约1.92 Ga 上地壳组合被称为北域（Karrat 群，sensu lato），在地理上被 Prøven 火成杂岩与 Karrat 群（sensu stricto）分开。将地层学和碎屑锆石剖面与 Rae 克拉通上大致同时代的沉积单元进行比较，并提出了其沉积的统一模型。 Rae 克拉通是主要的碎屑来源；最初这些来源大多是本地的，后来变成本地和远端来源的混合，包括西雷伊克拉通。卡拉特盆地的构造环境在其盆地演化过程中从伸展过渡到汇聚再到碰撞，反映了陆海内的威尔逊旋回阶段。因此，我们数据集中的锆石 Hf 同位素追踪了马尼科湾海洋打开和关闭的演变。我们数据集中的碎屑锆石 Hf 同位素揭示了更大比例的幼年碎屑（尤其是约 2.15-1.95 Ga）比目前暴露的地壳记录已知的要多，这表明碎屑锆石记录对于了解古元古代地壳和构造演化的重要性。