On Earth, carbon cycles through the land, ocean, atmosphere, living and dead biomass and the planet's interior. The global carbon cycle can be divided into the tectonically driven geological cycle and the biological/physicochemical cycles. The former operates over millions of years, whereas the latter operate over much shorter time scales (days to thousands of years). Within the geological cycle, atmospheric carbon dioxide concentration is controlled by the balance between weathering, biological drawdown, size of sedimentary reservoir, subduction, metamorphism and volcanism over time periods of hundreds of millions of years

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Precambrian travertines, tufas and speleothems either formed rarely or they have not been identified in previous studies. In the absence of high pCO 2 soils in Paleoproterozoic, karst solution and speleothem formation occurred by processes distinct from those commonly found in present-day low temperature karst environments. However, the high pCO 2 atmosphere could itself have encouraged karst formation. The Paleoproterozoic Kuetsjärvi Sedimentary Formation of the Pechenga Greenstone Belt, NW Russia, includes abundant terrestrial carbonate precipitates. These precipitates were sampled from a drillcore representing a complete section of the ca. 120-mthick formation and were investigated for C and O isotopes, acid-soluble elemental contents and petrography. The newly obtained results were used to constrain the origins of the precipitates and to illuminate different terrestrial carbonate types. The investigated drillcore includes abundant small-scale cavities and veins, which are commonly filled with dolomite and quartz. Dolomite crusts are found both in the cavities and on 1 bedding/erosional surfaces. Dolomite cements coat uneven surfaces and surficial rock fragments. The surficial dolomite crusts form distinct and discrete layers, whereas the cements do not. The cavity and vein fills are likely post-depositional in origin, whereasthe surficial dolomite crusts and dolomite cements are likely syndepositional precipitates. The investigated precipitates often show δ 13 C values lower than those reported from their host rocks, suggesting the influence of an external carbon source. Petrographic features and geochemical data suggest dissolution and precipitation of carbonate material originating from deep-sourced CO 2-bearing fluids, likely at high earth surface temperatures.

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