Experimentos de crecimiento de anhidrita en reactor cerrado a 80 ºC

Zusammenfassung

Calcium sulfate occurs in nature in three different mineral phases: gypsum (CaSO4·2H2O), bassanite CaSO4·1/2H2O and anhydrite (CaSO4). These phases can transform between them through dissolution-precipitation and hydration-dehydration processes. However, a possible primary origin of anhydrite in evaporitic rocks is a controversial issue. There are numerous evidences that anhydrite fails to precipitate under conditions within its stability field. In this work we undergo an experimental study of anhydrite growth at condition under which this phase is calcium sulphate stable phase. The experimental method has involved the use of closed reactors and natural anhydrite fragments as seeds. The physicochemical evolution of the aqueous solution has been monitored. The solid phase recovered after finishing the experiments mainly consisted each of hydrated phases of calcium sulfate. These results seem to indicate that anhydrite does not grow even when anhydrite seeds are present in the system. In order to explain the inhibition of anhydrite crystallization specific characteristics of anhydrite structure and how these characteristics influence the growth mechanisms operating on anhydrite surfaces are taken into consideration.