Abstract The temporal evolution of the sedimentary source areas of the Armorican Massif, involving Ediacaran to Upper Ordovician strata, is investigated to gain insight into the palaeogeographic affinities and changes that occurred as a result of Cadomian orogenesis. Until now, palaeogeographic reconstructions based on geodynamic, stratigraphic and paleontological data have shown geological continuity between the Armorican Massif and the Iberian and Bohemian massifs and have allowed researchers to locate the Armorican Massif near the West African Craton and the Trans-Saharan Belt. This study goes beyond the interpretations based on lithostratigraphic correlation, which may be influenced by allocyclic factors (e.g., sea-level change) or fauna assemblages that have a wide provincial distribution, to provide a correct assessment of sediment flux. To determine the palaeogeographic location more accurately, the provenance of the siliciclastic sediments was examined in this study using U–Pb LA-MC-ICP–MS geochronology on detrital zircons coupled with whole-rock Sm–Nd and zircon Lu–Hf isotope analysis. This work was carried out on the sedimentary succession of the Medio Armorican Domain. The oldest studied sedimentary rocks were shown to belong to the Brioverian succession, which contains mainly 519–781 Ma old zircons, likely derived from sources that are still present in the Armorican basement. Successively, the lower Paleozoic succession was deposited in the rift stages of the Rheic Ocean, with contributions from a new source of 827–1120 Ma old zircons. A comparison of the zircon populations showed an increase in negative eNd(t) and eHf(t) values of the sedimentary supply in the post-Cadomian samples. Moreover, it revealed that the Medio and North Armorican domains had different locations during the Lower Ordovician, and that some areas of the Iberian Massif and the Medio Armorican Domain close to the Sahara Metacraton and Arabian-Nubian Shield were contiguous.

中文翻译：

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法国西部布列塔尼中阿莫里坎域埃迪卡拉纪-奥陶纪沉积物的来源：来自 U/Pb 碎屑锆石和 Sm Nd 同位素数据的约束

摘要 研究了 Armorican 地块沉积源区的时间演化，包括埃迪卡拉纪到上奥陶统地层，以深入了解由于 Cadomian 造山作用而发生的古地理相似性和变化。迄今为止，基于地球动力学、地层和古生物数据的古地理重建显示，Armorican 地块与伊比利亚和波西米亚地块之间具有地质连续性，并允许研究人员在西非克拉通和跨撒哈拉带附近找到 Armorican 地块。本研究超越了基于岩石地层相​​关性的解释，后者可能受同种循环因素（例如海平面变化）或具有广泛省级分布的动物群组合的影响，以提供对沉积物通量的正确评估。为了更准确地确定古地理位置，本研究使用 U-Pb LA-MC-ICP-MS 碎屑锆石年代学结合全岩 Sm-Nd 和锆石 Lu-Hf 同位素分析来检查硅质碎屑沉积物的来源。这项工作是在 Medio Armorican Domain 的沉积层序上进行的。研究表明，最古老的沉积岩属于 Brioverian 序列，其中主要包含 519-781 Ma 的古老锆石，可能来自仍然存在于 Armorican 基底中的源。随后，下古生界层序沉积在流变洋裂谷阶段，新来源的贡献为 827-1120 Ma 的老锆石。锆石种群的比较显示后 Cadomian 样品中沉积供应的负 eNd(t) 和 eHf(t) 值增加。此外，它还揭示了下奥陶统期间，中阿莫里卡域和北阿莫里克域的位置不同，伊比利亚地块和中阿莫里克域靠近撒哈拉梅克拉通和阿拉伯-努比亚地盾的一些地区是连续的。