MINERAL RESOURCES OF SODIUM SULFATE IN IRAQ: AN OVERVIEW

Abstract

Sodium sulfate is an evaporate minerals that precipitates from sulfate-rich water and brines mainly in the inland salterns or sabkhas and found naturally as economic deposits in many places in the world. It is used in detergent, glass, paper, sodium silicate and some pharmaceutical industries. In Iraq, the only economic sodium sulfate deposit is found in the Shari Saltern near Samarra City. The sodium sulfate reserve in the Shari Saltern was estimated by about 22 Million tons. Other potential resources of sodium sulfate are found in the salterns of the Jazera area, but they need detailed work to estimate their economic potential. The Shari Saltern is a longitudinal closed basin originated in a subsiding N – S graben, filled with different types of sediments and solutes supplied by the ephemeral streams and seepages. The evaporite minerals found in the Shari Saltern are gypsum, glauberite, thenardite, mirabilite (in winter at low temperatures) and halite with trace amounts of bassanite, natron, trona, huntite, dʼansite and hydrated magnesium bromide. The sequential precipitation of the evaporite minerals in the Shari Saltern starts with gypsum and clay; mirabilite (in winter); gypsum, glauberite and clay; glauberite and clay; glauberite, thenardite and clay then glauberite, thenardite, halite as salt crust over the black mud slurry towards the center of the saltern and the uppermost part of the sediments column. Mirabilite crystalizes as almost pure sodium sulfate with long transparent crystals at low temperatures in winter. While glauberite precipitates by the effect of organic matter and anaerobic bacteria present in the black mud slurry which occupies the lowest part of the saltern. The mineral facies are concentric horizontally and vertically in the Shari Saltern so that the clay and gypsum facies lies below the clay and glauberite layer at depth and around it at the surface. Upward movement of groundwater from the underlying Mukdadiya Formation aquifer, formed seepages through the graben faults. These seepages feed the saltern with sulfate-rich water and precipitate gypsum, which results in a change of water composition to become suitable for glauberite precipitation. The isoconcentration maps of the Shari Saltern show the highest concentration of sodium sulfate is in the lowest part which is occupied by glauberite.