HR: 0800h
AN: B31B-0990    [Abstracts]
TI: Alkaline fluid circulation in ultramafic rocks and formation of nucleotide constituents
AU: * Holm, N G
EM: nils.holm@geo.su.se
AF: Stockholm University, Department of Geology and Geochemistry, Stockholm, - 10691 Sweden
AU: Dumont, M
EM: marion.dumont@geo.su.se
AF: Stockholm University, Department of Geology and Geochemistry, Stockholm, - 10691 Sweden
AU: Ivarsson, M
EM: magnus.ivarsson@geo.su.se
AF: Stockholm University, Department of Geology and Geochemistry, Stockholm, - 10691 Sweden
AU: Konn, C
EM: cecile.konn@geo.su.se
AF: Stockholm University, Department of Geology and Geochemistry, Stockholm, - 10691 Sweden
AB: Seawater is constantly circulating through oceanic basement, often at temperatures up to 150(°)C. In cases when ultramafic rocks are exposed to the fluids, for instance during the initial phase of subduction, ferromagnesium minerals are weathered, leading to high pH and formation of secondary magnesium hydroxide - brucite - that scavenges borate and phosphate from seawater. The high pH may promote abiotic formation of pentoses, particularly ribose. Borate is known to stabilize ribose, since cyclic ribose forms a stable, less reactive complex with borate. NMR analysis have shown that borate occupies the 2' and 3' positions of ribose, thus leaving the 5' position available for reactions like phosphorylation. The purine coding elements (adenine, in particular) of RNA as well as amino acids may be formed in the same general hydrothermal environments of the seafloor.
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0456 Life in extreme environments
DE: 0463 Microbe/mineral interactions
SC: Biogeosciences [B]
MN: Fall Meeting 2005