The Imandra/Varzuga Greenstone Belt

The Late Archaean-Early Palaeoproterozoic transition (2500–2000 Ma) represents a hallmark period when the Earth System experienced a series of fundamental upheavals. Among them, the most important was the establishment of an oxygen-rich atmosphere (sometimes referred to as the Great Oxidation Event) and the emergence of an aerobic biosphere. Associated with this, either incidentally or causally, was a cascade of other prominent, global-scale events that considerably modified Earth’s surface environments, either temporarily or permanently; these are reviewed in Parts 1 and 8 in full, and detailed in Part 7. Briefly mentioned here, these include: the severe and global climatic event known as the Huronian glaciation; an unprecedented perturbation of the global carbon cycle, the large-magnitude Lomagundi-Jatuli positive excursion of δ13Ccarb, lasted over 160 Ma; radical changes in the phosphorus and sulphur cycles resulting in accumulation of the first-known massive sulphates and sedimentary phosphates; a radical modification in recycling of organic matter leading to the emergence of a new 13C-depleted carbon reservoir in the form of carbonate concretions; and an unprecedented accumulation of organic-rich sediments and formation of the earliest supergiant petroleum deposits.