A 1:5000 scale mapping was performed in the Isukasia area of the ca. 3.8‐Ga Isua supracrustal belt, southern West Greenland. The mapped area is divided into three units bounded by low‐angle thrusts: the Northern, Middle, and Southern Units. The Southern Unit, the best exposed, is composed of 14 subunits (horses) with similar lithostratigraphy, bound by layer‐parallel thrusts. Duplex structures are widespread in the Isua belt and vary in scale from a few meters to kilometers. Duplexing proceeded from south to north and is well documented in the relationship between link‐ and roof‐thrusts. The reconstructed lithostratigraphy of each horse reveals a simple pattern, in ascending order, of greenstone with low‐K tholeiitic composition with or without pillow lava structures, chert/banded iron‐formation, and turbidites. The cherts and underlying low‐K tholeiites do not contain continent‐ or arc‐derived material. The lithostratigraphy is quite similar to Phanerozoic “oceanic plate stratigraphy,” except for the abundance of mafic material in the turbidites. The evidence of duplex structures and oceanic plate stratigraphy indicates that the Isua supracrustal belt is the oldest accretionary complex in the world. The dominantly mafic turbidite composition suggests that the accretionary complex was formed in an intraoceanic environment comparable to the present‐day western Pacific Ocean. The duplex polarity suggests that an older accretionary complex should occur to the south of the Isua complex. Moreover, the presence of seawater (documented by a thick, pillow, lava unit at the bottom of oceanic plate stratigraphy) indicates that the surface temperature was less than ca. 100°C in the Early Archean. The oceanic geotherm for the Early Archean lithosphere as a function of age was calculated based on a model of transient half‐space cooling at given parameters of surface and mantle temperatures of 100° and 1450°C, respectively, suggesting that the Archean oceanic lithosphere was rigid. These conclusions—rigidity and lateral plate movement—support the idea that the modern style of plate tectonics was in operation only 0.7–0.8 G.yr. after the formation of the Earth.

中文翻译：

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3.8-3.7 Ga 的板块构造：来自格陵兰西南部 Isua 增生杂岩的现场证据

在约的 Isukasia 地区进行了 1:5000 比例尺测绘。3.8-Ga Isua 上地壳带，西格陵兰岛南部。测绘区域以低角度逆冲断层划分为三个单元：北单元、中单元和南单元。出露最好的南部单元由具有相似岩石地层的 14 个亚单元（马）组成，受层平行逆冲断层约束。伊苏阿带中普遍存在复式构造，规模从几米到几公里不等。双工从南到北进行，并且在连接和屋顶推力之间的关系中有很好的记录。每匹马的重建岩石地层显示了一个简单的模式，按升序排列，绿岩具有低 K 拉斑岩成分，有或没有枕状熔岩结构、燧石/带状铁层和浊积岩。燧石和下伏的低 K 拉斑岩不包含大陆或弧形衍生材料。岩石地层学与显生宙的“海洋板块地层学”非常相似，只是浊积岩中含有丰富的镁铁质物质。双重构造和大洋板块地层的证据表明，Isua 上地壳带是世界上最古老的增生杂岩。主要的基性浊积岩组成表明增生杂岩形成于与当今西太平洋相当的洋内环境中。双极性表明一个较老的增生复合体应该出现在 Isua 复合体的南部。此外，海水的存在（用厚厚的枕头记录，大洋板块地层底部的熔岩单元）表明地表温度低于约。太古代早期 100°C。根据表面和地幔温度分别为 100° 和 1450°C 的给定参数下的瞬态半空间冷却模型，计算了作为年龄函数的早期太古代海洋岩石圈的海洋地温，表明太古代海洋岩石圈是死板的。这些结论——刚性和横向板块运动——支持现代风格的板块构造仅运行 0.7-0.8 G.yr 的观点。地球形成后。分别表明太古代海洋岩石圈是刚性的。这些结论——刚性和横向板块运动——支持现代风格的板块构造仅运行 0.7-0.8 G.yr 的观点。地球形成后。分别表明太古代海洋岩石圈是刚性的。这些结论——刚性和横向板块运动——支持现代风格的板块构造仅运行 0.7-0.8 G.yr 的观点。地球形成后。