Alkaline fluid circulation in ultramafic rocks and abiotic formation of nucleotide constituents
by
Prof.Nils G. Holm(Department of Geology and Geochemistry, Stockholm University)
→
Europe/Stockholm
Department of Geology and Geochemistry
Department of Geology and Geochemistry
Description
Serpentinization of olivine and pyroxene in ultramafic mantle rocks is a process that has attracted much attention during recent years. This is a complex series of reactions that occurs at temperatures below 500°C in several active tectonic settings. Biogeochemically the process is important because it leads to reduction of H2O to H2. At the same time, catalytically active compounds like magnetite are formed. H2 may be used together with CO2 and magnetite as a catalyst in Fischer-Tropsch Type (FTT) reactions. FTT processes may lead to the formation of CH4 as well as heavier hydrocarbons and other abiotic organic compounds. Serpentinization at temperatures below 300°C is associated with high pH (pH 10-12). It is possible that the high pH may promote the formose reaction in natural environments and the abiotic formation of pentoses like ribose, the carbohydrate constituent of RNA. Pentoses, and ribose in particular, are stabilized by borate that is scavenged from seawater by brucite – magnesium hydroxide that is yet another product of serpentinization reactions.
