High-precision Δ′<sup>17</sup>O measurements of geothermal H<sub>2</sub>O and MORB on the VSMOW-SLAP scale: evidence for active oxygen exchange between the lithosphere and hydrosphere

Recent studies have reported slight but definite differences in Δ′17O between the lithosphere and hydrosphere. In present study, we precisely accurately quantify values of geothermal H2O mid-ocean ridge basalt (MORB) with normalization on VSMOW-SLAP scale to further substantiate these discuss isotopic evolution hydrosphere throughout geologic time scale. With a value -60 ± 13 × 10-6, MORB is comparable that other silicates previous studies. However, tended decrease from +31 10-6 -51 which are usual meteoric water silicates, respectively, accordance 18O-enrichment. These results imply an active oxygen isotope exchange under high-temperature conditions at depth. This supported by report 17O-enrichment silicate altered hydrothermal H2O. Considering this direct evidence for depletion 17O, conclude 17O-depleted has been supplied continuously Additionally, low-temperature interaction besides must be assumed explain observed terrestrial We should variable owing various