Bøger af Rafaa Zair Jassim

Shari playa is a closed basin characterized by the development of seven sedimentary facies and five sedimentary subenvironments over the underlying clastic substrata facies. The sediments distribution and geometry indicate that the playa is a subsiding N-S oriented graben. The area show three sets of lineaments oriented NW-SE, NE-SW and N-S directions. A set of N-S step faults, partly affected by the other trends of lineaments, seems to control the subsidence and orientation of the graben. The age of the depression is suggested to be 6000-6500 years B.P. deduced from the palynological studies, assumed rates of precipitation and comparison with palaeoclimatic trends. Saline minerals found in the Shari Playa are: gypsum, glauberite, halite, thenardite and trace amounts of bassanite, natron, trona, huntite, d'ansite and hydrated magnesium brormide. They mainly occur in the facies that occupy the central part of the playa. The main saline minerals in the playa show spatial and vertical distribution reflecting the playa lake brine evolution and concentration following characteristic paths on the system CaSO4 - Na2SO4 ¿ NaCl - H2O.

Calcium sulfate is a group of minerals having different water content in their composition ranging from dehydrate to dihydrate. It is either primary or secondary, the primary were deposited in Iraq in different geological periods in semi restricted basins, only of which the gypsum and anhydrite of Fatha and Dhiban formations are exposed on the surface in the areas of Mosul, Kirkuk, Erbil and Anbar Governorates and became good resource for cement, plaster and djuss industries. The total reserve of the primary gypsum was estimated to be 142 million tons. The secondary gypsum, gypcrete or gypsiferous soil, were formed in the upper few meters of the soil cover by different processes leading to enrichment of calcium sulfate in the soil. Among these processes the upward migration of the sulfate rich water by capillary action is the most important. The gypsiferous soil, according to the latest studies, for the depth 0 ¿ 25 cm is of low gypsum content and covers about 39% of Iraqi soil (except some areas in the northeast and south of Iraq). While for the depth 25 ¿ 150 cm it is of medium gypsum content and covers about 53% of the Iraqi soil.