Establishing the positions of continents during the initial stages of Earth's evolution is one of the most important challenges in geosciences today. This challenge is mainly due to the severe limitations in obtaining geological and/or geophysical data from early Earth time, particularly robust paleomagnetic data. Here, we report the first paleomagnetic data from an Archean block in the Amazonian craton, the Carajás Province, for ∼2.76–2.74 billion years ago (Ga), when extensive dominantly mafic volcanism (Parauapebas Formation) covered an area of ∼18,000 km². The paleomagnetic investigation was conducted on fresh drill cores drilled into the Carajás iron ore mine and cutting across the Parauapebas Formation. After rotating the drill core segments to geographic coordinates using the viscous magnetic component, two characteristic components, Carajás 1 and 2 (C1 and C2) were identified and further used to calculate paleomagnetic poles: C1 (∼2759 Ma; 40.5°E, −44.6°S, N = 5 A₉₅ = 6.5°, K = 18.5) and C2 (∼2749 Ma; 342.4°E, −54.3°S, N = 28, A₉₅ = 14.8°, K = 27.8). Pole C2 is based on a bigger number of sites, passes a reversal test and is considered robust. A baked contact test was attempted for this component, but it is not conclusive. Our results, integrated with geological evidence reveals that the Carajás block occupied low latitudes at the time, and could have been part of the Superia supercraton during the Neoarchean (∼2.75 Ga) at equatorial latitudes. Finally, a consistent succession of six magnetic reversal events was identified in the lava flow sequence from the Parauapebas Formation, pointing to an already dynamic geodynamo pre-2.7 Ga.

在地球演化的初始阶段确定大陆的位置是当今地球科学中最重要的挑战之一。这一挑战主要是由于从地球早期获取地质和/或地球物理数据的严重限制，特别是强大的古地磁数据。在这里，我们从亚马逊克拉通的卡拉加斯省的太古代块报告第一古地磁数据，~2.76-2.74十亿年前（GA），当大量的显性镁铁质火山（帕劳阿佩巴斯组）覆盖~18,000公里，面积². 古地磁调查是对钻入 Carajás 铁矿并切割 Parauapebas 地层的新鲜钻芯进行的。使用粘性磁分量将钻芯段旋转到地理坐标后，识别出两个特征分量 Carajás 1 和 2（C1 和 C2）并进一步用于计算古磁极：C1（~2759 Ma；40.5°E，-44.6 °S, N = 5 A ₉₅  = 6.5°, K = 18.5) 和 C2 (∼2749 Ma; 342.4°E, -54.3°S, N = 28, A ₉₅ = 14.8°，K = 27.8）。Pole C2 基于更多的站点，通过了反向测试，被认为是稳健的。对该组件进行了烘烤接触测试，但不是结论性的。我们的结果与地质证据相结合，表明 Carajás 地块当时处于低纬度，并且可能是赤道纬度新太古代（~2.75 Ga）期间 Superia 超级克拉通的一部分。最后，在来自 Parauapebas 地层的熔岩流序列中确定了连续连续的 6 个磁反转事件，表明在 2.7 Ga 之前已经是动态的地球发电机。