Geothermal mineral equilibria Giggenbach, W F 15 GEOTHERMAL ENERGY; GEOTHERMAL FLUIDS; WATER CHEMISTRY; MINERALS; SOLUBILITY; STABILITY; CARBON DIOXIDE; EQUILIBRIUM; EXPERIMENTAL DATA; FELDSPARS; GEOTHERMAL SYSTEMS; THERMODYNAMICS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; DATA; FLUIDS; INFORMATION; NUMERICAL DATA; OXIDES; OXYGEN COMPOUNDS; 150302* - Geothermal Exploration & Exploration Technology- Geochemical Techniques & Surveys The dominant reaction determining the chemistry of fluids in a geothermal system of the New Zealand type consists of the conversion of primary plagioclase by CO/sub 2/ to calcite and clays with log P/sub CO/sub 2// = 15.26 - 7850/(t + 273.2), temperature t in /sup 0/C. Subsequent reactions involving secondary minerals control relative CO/sub 2/-H/sub 2/S-contents. The distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate, metastable phases to a thermodynamically stable, secondary assemblage. The relative stabilities of these phases was evaluated on the basis of their solubilities, the least soluble aluminium-silicate representing the thermodynamically most stable phase under a given set of conditions. Observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral/fluid-interaction conditions to be evaluated on the basis of multi-component mineral stability diagrams. Dept. of Scientific and Industrial Research, Petone, New Zealand United Kingdom 1981-03-01 English Journal Article Journal Name: Geochim. Cosmochim. Acta; (United Kingdom); Journal Volume: 45:3 Medium: X; Size: Pages: 393-410 https://doi.org/10.1016/0016-7037(81)90248-9 [] 45:3 Journal ID: CODEN: GCACA TIC; EDB-81-038249 2010-12-30 6658242