The Eoarchaean foundation of the North Atlantic Craton

The Archaean North Atlantic Craton underpins much of North America, Greenland and northern Europe, and incorporates the Earth's oldest extant continental crust. This paper reviews the current understanding of the region's crustal evolution, and considers our ability to investigate interrelationships between different fragments of the North Atlantic Craton. Detrital zircons from Mesoproterozoic to Cambrian basal sediments in NW Scotland have been re-examined in light of new data from the Archaean Tarbet supracrustal unit and the Palaeoproterozoic Rubha Ruadh granite. Hf model ages are recorded from 4160 to 1410 Ma, peaking at <em>c.</em> 3350 Ma, and are associated with U–Pb crystallization ages from 3670 to 1070 Ma, peaking at <em>c.</em> 2700 and 1700 Ma. The Rubha Ruadh granite is consistent with partial melting of Northern Region basement without contamination by juvenile magmas or supracrustal material, while the Tarbet Supracrustals record a minimum model age of <em>c.</em> 3200 Ma. Each of these units records Hf model ages that imply remelting of Eoarchaean (4000–3600 Ma) crust. Similar distributions of crystallization and model ages have been identified around the North Atlantic Craton, suggesting that Eoarchaean crust was once extensive in the region and constitutes the foundation of both Scotland and the North Atlantic Craton.

太古宙北大西洋克拉通（Archaean North Atlantic Craton）支撑着北美、格陵兰与北欧的大部分区域，赋存着地球已知最古老的现存大陆地壳。本文综述了当前对该区域地壳演化的认知，并探讨了我们研究北大西洋克拉通不同碎块间相互关系的可行性。针对苏格兰西北部中元古代至寒武纪基底沉积岩中的碎屑锆石，结合太古宙Tarbet表壳岩单元（Archaean Tarbet supracrustal unit）与古元古代Rubha Ruadh花岗岩的新数据，本文对其进行了重新厘定。其Hf同位素模式年龄记录区间为4160 Ma至1410 Ma，峰值约为3350 Ma；同时对应的U-Pb结晶年龄区间为3670 Ma至1070 Ma，峰值分别约为2700 Ma与1700 Ma。Rubha Ruadh花岗岩符合北地块基底发生部分熔融、且未受新生岩浆或表壳物质污染的特征，而Tarbet表壳岩的最小模式年龄约为3200 Ma。上述各单元的Hf同位素模式年龄均表明，始太古代（Eoarchaean，4000–3600 Ma）地壳曾发生过重熔融。北大西洋克拉通周边已发现类似的结晶年龄与模式年龄分布特征，这暗示始太古代地壳曾在该区域广泛分布，构成了苏格兰与北大西洋克拉通的基底。