EXPERIMENTAL DIFFUSION OF HYDROGEN INTO SYNTHETIC FLUID INCLUSIONS INQUARTZ

Quartz-hosted, synthetic CO2-H2O fluid inclusions behave as open syste ms with respect to diffusional transfer of hydrogen during laboratory- simulate metamorphic re-equilibration at 650, 750 and 825 degrees C an d 1.5 kbar total pressure with f(o2) defined by the C-CH4 buffer. Micr othermometry and Raman spectroscopy show that the initial CO2-H2O incl usions become CO2-CH4-H-2-H2O inclusions after diffusive influx of hyd rogen from the reducing confining medium. Measurable changes are obser ved in inclusion compositions after only 15 days of re-equilibration, implying significant hydrogen mobility at still lower temperatures ove r geological time spans. Results of synthetic inclusion re-equilibrium experiments have profound implications for the interpretation of natu ral fluid-inclusion data; failure to account for potential hydrogen mi gration in inclusions from high-temperature geological environments ma y lead to erroneous estimates of P-T, and/or the compositions of metam orphic fluids.