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Commercial Value Assessment of Newly Discovered Anhydrite Soil in the Coastal Lands of Abu Dhabi Emirate

A unique anhydrite (CaSO4) rich soil has been discovered during the soil inventory of the coastal lands of Abu Dhabi Emirate. The next challenge was to assign a taxonomic name using the world most used Soil Taxonomy of the United States Department of Agriculture (USDA). As anhydrite soil had not been reported previously in the USDA soil taxonomy hierarchy, the closest soil was gypsic (CaSO4.2H2O), and therefore, it was imposed to anhydrite soil, which is far from perfect. Based on this, a proposal for a change in USDA Soil Taxonomy was prepared. The proposal suggests addition of anhydritic diagnostic horizon and mineralogy class, as well as Anhydritic Aquisalids subgroup in Aridisols soil order. The suggested changes are shared in this paper. Both gypsum and anhydrite have commercial value based on composition, purity, mining cost, and extent of deposit. In this paper representative anhydrite samples from five potential locations have been investigated for their physical, chemical, purity and mineralogical composition using standard analytical procedures. The solution chemistry is dominated by cations Ca > Na > Mg > K and anions SO4 > Cl > HCO3. The anhydrite was identified as dominant mineral, occurring as single mineral, and in association with halite and calcite. It has been concluded that four out of five samples have purity ranging from 73 to 98% as required for a commercial product (> 70%), only one sample showed 51% purity which have impurities such as quartz, plagioclase, dolomite, and magnesite. The interesting feature observed is that anhydrite (CaSO4) is not converted to gypsum (CaSO4.2H2O) when coexisting with water in the coastal lands of Abu Dhabi Emirate. The high salinity coupled with high temperature of crystallization in hyper arid coastal lands of Abu Dhabi Emirate could be the reason to favor anhydrite formation over gypsum.

Shahid S. A
Publication type: 
Scientific Paper
Publication Source: 
Geology Day
Page Number: 

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