Banded iron-formations (BIFs), which provide the world’s main source of iron, accumulated during a restricted Lower Precambrian interval. Their alleged precipitation from mid-ocean hydrothermal ferruginous solutions mixing with down-slope flowing oxygenated water is not possible. No free oxygen could have accumulated in water under the prevailing anoxic conditions. Newly discovered sedimentary structures corroborate very shallow depositional settings. Accordingly, BIFs precipitated in huge lakes of warm hydrothermal solutions undergoing intensive evaporation and mineral concentration in the freezing-cold Polar Regions. As a result of half a year of illumination, cyanobacteria oxygenic photosynthesis deposited iron oxides with silica (geyserite) followed by a lamina of silica only, forming recurrent annual varves. Diamictites on top of BIF successions in Western Australia and South Africa accumulated from melting glaciers when the plates shifted to lower latitudes, as corroborated by paleomagnetic high-latitude paleo-positions. Calcium carbonate precipitated under higher water levels and more diluted solutions. The chemistry of these BliFs and associated carbonates do not represent the Early Precambrian oceans, and the diamictites at the end of their sequence do not attest to global glaciation.

中文翻译：

---

早期前寒武纪带状铁地层：极地湖泊高度蒸发的热液溶液中的生化沉淀

带状铁地层 (BIF) 是世界上铁的主要来源，在受限制的下前寒武纪时期积累。他们所谓的从大洋中热液含铁溶液与下坡流动的含氧水混合的沉淀是不可能的。在普遍的缺氧条件下，水中不可能积累游离氧。新发现的沉积结构证实了非常浅的沉积环境。因此，BIF 沉淀在巨大的温暖热液湖中，在冰冷的极地地区经历了强烈的蒸发和矿物质的浓缩。由于半年的光照，蓝藻含氧光合作用将氧化铁与二氧化硅（间歇泉）一起沉积，然后仅沉积一层二氧化硅，形成反复出现的一年生斑纹。古地磁高纬度古位置证实了当板块向低纬度移动时，西澳大利亚和南非 BIF 层序顶部的混叠岩从融化的冰川中积累。碳酸钙在更高的水含量和更稀的溶液中沉淀。这些 BliF 和相关碳酸盐的化学性质不代表早前寒武纪海洋，其序列末端的混叠岩也不能证明全球冰川作用。