Microbially influenced formation of anhydrite at low temperature

Zulfa Ali Al Disi; Fadhil Sadooni; Hamad Al-Saad Al-Kuwari; Tomaso R R Bontognali

doi:10.1016/j.scitotenv.2023.165820

Microbially influenced formation of anhydrite at low temperature

Sci Total Environ. 2023 Dec 1:902:165820. doi: 10.1016/j.scitotenv.2023.165820. Epub 2023 Jul 26.

Authors

Zulfa Ali Al Disi¹, Fadhil Sadooni¹, Hamad Al-Saad Al-Kuwari¹, Tomaso R R Bontognali²

Affiliations

¹ Environmental Science Centre, Qatar University, P.O. Box 2713, Doha, Qatar.
² Environmental Science Centre, Qatar University, P.O. Box 2713, Doha, Qatar; Space Exploration Institute, 68 Faubourg de l'Hopital, 2000, Neuchatel, Switzerland; Physical Geography and Environmental Change Research Group, University of Basel, Klingelbergstrasse 27, 4056 Basel, Switzerland. Electronic address: tomaso.bontognali@space-x.ch.

PMID: 37506898
DOI: 10.1016/j.scitotenv.2023.165820

Abstract

Calcium sulfate minerals are abundant in nature - on Earth and on Mars - and important in several fields of material sciences. With respect to gypsum and bassanite, anhydrite represents the anhydrous crystalline phase in the CaSO₄-H₂O system. Despite years of research, the formation of anhydrite in the laboratory at low temperature remains challenging and, in the geological record, this mineral is mostly interpreted as a secondary phase that form through metamorphic dehydration of gypsum. Here, we present the results of laboratory precipitation experiments showing that anhydrite can form at 35 °C from evaporated seawater through a microbially influenced mineralization process. The experiments were conducted in the presence of extracellular polymeric substances (EPS) produced by bacterial strains isolated from a modern evaporitic environment, the Dohat Faishakh sabkha in Qatar. Without organic molecules, only gypsum formed in parallel control experiments. This finding provides a possible explanation for the origin of several natural occurrences of anhydrite that cannot be satisfactorily explained by existing models and reveals a new precipitation pathway that may have industrial applications.

Keywords: Anhydrite; Bassanite; EPS; Evaporation; Gypsum; Mars.