Hydrothermal reaction of Columbia River basalt and Hanford groundwater

This report presents results of experiments in which an artificially prepared Grande Ronde ground-water was reacted with Grande Ronde Columbia River basalt at 200 and 300 degree C, 300 bars, and water: rock mass ratios of 5 and 10. Duration of the experiments were as much as 4000 hours. Secondary reaction products formed during the experiments include: potassium feldspar, illite, smectite, scapolite, zeolite, wairakite, and a silica phase. Solutions composition was appreciably modified during the experiments, silica, potassium, aluminum, and sulfide increased; wherease sulfate, fluoride, sodium, and total dissolved carbonate decreased. The pH initially decreased as low as 6.5 from an initial value of about 8.2. The pH then rose during the experiments and stabilized near 7.5. Solution composition was still changing slowly at the end of the experiments, indicating that the experiments had not come either to equilibrium or to steady state. At 300 degree, the calculated solution Eh was ca -0.7, calculated f02 was 10-31. 38 refs., 23 figs., 7 tabs