The hydrogeochemistry of strontium in the Ranegras Plain groundwater basin

Abstract

The occurrence, sources, and governing geochemical reactions of strontium in the groundwater of the Ranegras Plain basin, western Arizona, were evaluated by the analysis of basin geology, groundwater quality data, and chemical analyses of basin drill cuttings and potential strontium source rocks from the surrounding mountains. Four potential mechanisms controlling the hydrogeochemistry of strontium were evaluated: (1) celestite and strontianite dissolution; (2) strontium release during the weathering of silicate minerals; (3) the solid solution of strontium in calcite, aragonite, and gypsum; and (4) cation exchange. Evaporite dissolution, aluminosilicate mineral hydrolysis, calcite precipitation, and cation exchange control the basin hydrogeochemistry. Strontium concentrations in groundwater range from 0.060 to 4.4 milligrams per liter and are controlled primarily by pH, gypsum dissolution and calcite precipitation of which strontium is a trace component, and the cation exchange of strontium on aquifer minerals.