The Archaean-Proterozoic transition and iron ore genesis: the Amazon perspective from the world-class Serra Sul iron ore deposit, Carajás, Brazil

带状铁地层和黑色页岩记录了反映海洋大气系统全球化学和生物特征的海洋环境条件。Carajás是巴西亚马逊地区的世界级铁矿区，最近对Serra Sul矿床的勘探发现，目前仍处于原始状态的Serra Sul地区迄今已发现的四个矿体中，只有一个矿体的实测资源量为40亿吨，铁含量为bbbb64 wt%。这些结果使Serra Sul成为世界上最大的铁矿石矿床之一。勘探还发现，黑色页岩位于Serra Sul BIF单元的正下方。地质推断表明这些岩石形成于2.7 Ga左右。黑色页岩和BIF的共存可以重建Serra Sul岩石层序沉积期间海洋-大气系统的演化，这将为涉及太古宙-元古代过渡和大气氧气上升的激烈争论（即大氧化事件）提供新的线索。我们的亚马逊视角将整合钼、硫、铼锇和钐钕同位素的块状岩石分析数据，以及铁和氧同位素的微量分析，并以详细的岩石学和元素地球化学为背景。此外，我们的目标是确定从BIF到高品位铁矿石的沉积后过程。

Banded iron formations (BIFs) and black shales record marine environmental conditions that reflect global chemical and biological features of the ocean– atmosphere system. They host mineral deposits that, in the case of BIF, account for most of the world’s mine production of iron ore. Carajás is a world-class iron ore district in the Amazon region of Brazil, where recent exploration of the Serra Sul deposit has identified a measured resource of 4 billion tonnes at >64 wt% Fe for just one of the four orebodies hitherto recognised in the currently still pristine Serra Sul area. These results place Serra Sul as one of the world’s largest iron ore deposits. Exploration also revealed that black shales occur immediately below the BIF unit at Serra Sul. Geological inference suggests that these rocks formed at about 2.7 Ga. The coexistence of black shales and BIF allows reconstructing the evolution of the ocean–atmosphere system during the deposition of the Serra Sul rock sequence, which will shed new light on the vigorous debate involving the Archaean–Proterozoic transition and the rise in atmospheric oxygen, i.e. the Great Oxidation Event. Our Amazon perspective will integrate data from bulk-rock analysis of molybdenum, sulfur, rhenium–osmium, and samarium–neodymium isotopes, as well as microanalysis of iron and oxygen isotopes on a background of detailed petrography and elemental geochemistry. In addition, we aim at identifying the post-depositional processes which led from BIF to high-grade iron ore.