Dear listmembers,

could you, please, provide me with some references to papers, describing a negative correlation between del18O and del13C values of hydrothermal carbonates ?
        I have observed such a puzzling trend in calcite crystals from hydrothermal karst caves. The crystals have grown from low salinity (0-2.5 wt. percent) aqueous fluids at 120-80 deg C. The del18O (SMOW) regularly increase from +10 to +13 permil, while the del13C (PDB) decrease from -3 to -12 permil from core to rim of the crystals.
        I am not able to interpret these data in terms of any known fractionation mechanisms. A mixing between two fluids is also unlikely, because the trends are linear, i.e. both potentially mixing fluids should have to have the same carbon concentration (highly unlikely).
        Thanks in advance for any help !
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Dr. Vratislav Hurai
Dept. of Isotope Geology
Geological Survey of Slovakia
817 04  Bratislava, Slovakia
tel.: (00421-7)59375140, fax: (00421-7)54771940
e-mail: [log in to unmask]