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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.‎

Authors: 
Shahid S.‎ A
Year: 
۲۰۱۲
Publication type: 
Scientific Paper
Publication Source: 
Geology Day
Page Number: 
۷