Reconstruction of Earth's surface environments in the Late Archean based on the scientific drilling of the Dharwar Craton, south India

本研究的目的是以印度南部达尔瓦尔盆地的科学钻探为基础，重建晚太古代的地球表面环境。主要研究成果如下：包括达尔瓦尔盆地在内的主要盆地前寒武纪条带状铁建造的稀土元素地球化学制约了全球环境变化。在晚太古代达尔瓦尔BIFs中存在明显的负Ce异常表明，像今天这样的强氧化海洋条件出现在2.9-2.7 Ga。这一建议是一致的地质证据，小，但广泛的锰矿床形成于晚太古代。哈默斯利和德兰士瓦IF的Ce异常不太明显。这些生物IFs沉积在一个不断演变的裂谷上，该裂谷位于一个内陆海洋中，由于强烈的热液活动而变得缺氧。2.2- 2.1Ga的通道型IFs表现出明显的负Ce异常，而2.2- 2.1Ga的通道型IFs表现出明显的负Ce异常。1.9如果和ca。0.7 Ga IF具有不太明显的Ce 关于我们 异常Ce/Ce* 值的后2.7 Ga BIFs的这些变化可能反映了全球地幔柱活动，创造局部缺氧盆地的episodicity。太古代Algoma型BIFs具有明显的正Eu异常，但变化很大。其强烈的正Eu异常表明热液流体对BIF沉淀所涉及的海水有很大的贡献。藻类型BIFs中Eu异常的大变化反映了不同沉积地点热液流体和环境海水混合比例的大变化。然而，2.7Ga掺杂后的BIF表现出低得多且恒定的Eu/Eu* 值（0.7-1.9）。这意味着，稀土元素化学的盆地水，承载大量的走廊型BIFs的影响，从周围大陆的河流流入，由于全球地幔柱活动迅速增长，除了强烈的热液流入。这些重要发现发表在《美国地质学会回忆录》上。其他研究成果发表在许多著名的国际期刊上，包括地球和行星科学快报，前寒武纪研究，岩石和海洋地质学。少

The aim of our study was to reconstruct Earth's surface environments in the Late Archean based on the scientific drilling of the Dharwar Craton, south India. We have gained research results as follows.Global environmental changes have been constrained from rare earth element geochemistry of Precambrian banded iron formations in the major cratons including the Dharwar Craton. The presence of pronounced negative Ce anomalies in Late Archean Dharwar BIFs suggests that strongly oxygenated oceanic conditions like today emerged by 2.9-2.7 Ga. This suggestion is consistent with geologic evidence that small but widespread Mn deposits formed during Late Archean time. The Hamersley and Transvaal IFs have less noticeable Ce anomalies. These BIFs were deposited on an evolving rift in a land-locked ocean that became anoxic due to intense hydrothermal activity. The 2.2-2.1 Ga Superior-type IFs exhibit distinct negative Ce anomalies, but the ca. 1.9 Ga Ifs and the ca. 0.7 Ga IFs have less distinct Ce … More anomalies. These variations in Ce/Ce* values of the post-2.7 Ga BIFs may reflect the episodicity in global mantle plume activity that created locally anoxic basins. The Archean Algoma-type BIFs have distinctly positive but variable Eu anomalies. Their strong positive Eu anomalies suggest large contributions of hydrothermal fluids to the seawater involved in BIF precipitation. The large variation in Eu anomalies in Algoma-type BIFs reflects the large variation in mixing ratios of hydrothermal fluids and ambient seawaters at various depositional sites. However, the post-2.7 Ga Superior-type BIFs exhibit much lower and constant Eu/Eu* values (0.7-1.9). This implies that the REE chemistry of the basin water that hosted voluminous Superiortype BIFs was influenced by a riverine influx from the surrounding continent that grew rapidly due to global mantle plume activity, besides the intense hydrothermal influx. These important findings were published in Geological Society of America Memoir. Other research results were published in many prestigious international journals including Earth and Planetary Science Letters, Precambrian Research, Lithos and Marine Geology. Less