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TcGa crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Tc3- is bonded to six equivalent Tc3- and six equivalent Ga3+ atoms to form a mixture of distorted corner, edge, and face-sharing TcGa6Tc6 cuboctahedra. All Tc–Tc bond lengths are 2.90 Å. All Tc–Ga bond lengths are 2.64 Å. Ga3+ is bonded in a 6-coordinate geometry to six equivalent Tc3- atoms.
Here, this study combines recirculated flow-through experimental results conducted for 17 days at 90C and 200 PSI with reactive transport modeling to estimate fluid-rock interactions occurring in a sandy mudstone using an interbedded sandstone-shale sample from the Cacapon Member of the upper Tuscarora Sandstone/lower Rose Hill Formation for the purpose of geothermal exploration. Results suggest that the fluid and rock are likely to be in or near partial-equilibrium after approximately one year. In addition, after >400 h of continuous injection at 0.05 mL/min (5*10 −8 m 3 /min) the reactive front is restricted to the first ∼13% of the 4 cm*1.6 cm experimental rock length, whereas after >9100 h (∼1 year), the reactive front extends to 30% total length. The rate of changes in dissolution or precipitation are however, very minimal, with all major rock-forming minerals having rates <10 −11 mol/L porous media/s. Reservoir rock in the presence of dilute brine as may be the case during operation of an enhanced geothermal system would experience little alteration during the shut-in phase, and possibly up to one year. These results have utility in geothermal exploration for reservoirs at similar temperatures as well as general fluid-sandy mudstone rock interaction geochemistry.