Abstract Archean to Paleoproterozoic rocks potentially record the evolution of the geodynamo and the tectonic mode of the early Earth. The paleomagnetic intensity and direction data provide important information on the Earth’s core–mantle revolution. Herein, we report the results of paleomagnetic and geochronological studies of a Proterozoic dolerite dyke from southern West Greenland. Clinopyroxene grains from the dyke yielded Ar–Ar plateau ages from 1,808 to 1,887 Ma (1,816.0 ± 14.6 Ma; 2σ). The paleomagnetic direction of the dyke (D = 243.6°, I = 66.3°, α95 = 3.9°) yielded a virtual geomagnetic pole (VGP) of 33.5 °N and 96.4 °W. This 1.8 Ga pole falls in a limited area where Paleoproterozoic poles between 2.5 Ga and 1.7 Ga for southern West Greenland are distributed. Comparison of the Paleoproterozoic poles of southern West Greenland with those of North America suggests that the North Atlantic Craton of southern Greenland could have been an independent stagnant tectonic block, different from the drifting Superior and Slave Cratons in the Early Proterozoic. Thellier experiments on 13 specimens yielded a mean paleointensity value of 14.8 ± 2.3 μT, indicating a virtual dipole moment of 2.88 ± 0.46 × 1022 Am2. This value is approximately one-third of the present-day Earth's field intensity, and is consistent with the value for the period between 1,400 Ma and 2,400 Ma. This small paleointensity value of the Proterozoic rocks is due to a gradual dipole moment change over a long period (∼1 Gyrs) since 4,000 Ma.

中文翻译：

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西格陵兰岛南部元古代辉绿岩脉的古地磁、古强度和年代学

摘要 太古代至古元古代岩石可能记录了地球早期地球动力学和构造模式的演化。古地磁强度和方向数据提供了有关地核-地幔公转的重要信息。在此，我们报告了西格陵兰岛南部元古代辉绿岩脉的古地磁和地质年代学研究结果。岩脉中的单斜辉石颗粒产生了从 1,808 到 1,887 Ma（1,816.0 ± 14.6 Ma；2σ）的 Ar-Ar 高原年龄。岩脉的古地磁方向（D = 243.6°，I = 66.3°，α95 = 3.9°）产生了一个 33.5°N 和 96.4°W 的虚拟地磁极（VGP）。这个 1.8 Ga 极点位于一个有限的区域，其中分布着格陵兰岛南部 2.5 Ga 和 1.7 Ga 之间的古元古代极点。西格陵兰岛南部的古元古代极地与北美的古元古代极地的比较表明，格陵兰岛南部的北大西洋克拉通可能是一个独立的停滞构造块，不同于早元古代漂移的上级和奴隶克拉通。对 13 个样本进行的 Thellier 实验产生了 14.8 ± 2.3 μT 的平均古强度值，表明虚拟偶极矩为 2.88 ± 0.46 × 1022 Am2。该值大约是当今地球场强的三分之一，与 1,400 Ma 至 2,400 Ma 期间的值一致。元古界岩石的这种小的古强度值是由于自 4,000 Ma 以来在很长一段时间内（~1 Gyrs）偶极矩逐渐变化。