Iraqi Bulletin of Geology and Mining

Al-Salman Depression is one of the largest karst forms in the Southern Desert of Iraq. It is of doline type, being formed in carbonates of Dammam Formation of Eocene age. The length of the depression is 20 Km, whereas, the width is variable, it is (6.5, 10 and 4.5) Km, in the northern, central and southern parts, respectively, whereas, the depth ranges from (5 – 35) m.
The Iraqi Southern Desert is one of the most extensive karstified areas in Iraq. Different types and forms of karst were developed with different sizes. Among the karst forms is Al-Salman Depression. The main reason of karstification is the presence of the carbonates of the Dammam Formation, which are underlain by the Rus Formation (Early Eocene); it consists mainly of anhydrite with limestone interlayers.

The Pleistocene Period witnessed wet climate in the studied area, which had contributed in the karstification of the Iraqi Southern Desert, in which karst forms have played a big role in development of special landscape, which is characterized by special drainage system and enormous amount of closed depressions and blind valleys. Originally, Al-Salman Depression was consisting of three main depressions, which merged together due to karstification, head ward erosion and collapsing parts of the rims. The presence of the sediments of Zahra Formation (Pliocene – Pleistocene) in the Salman Depression indicates Pliocene and most probably uppermost Late Miocene age for the depression that has developed due to karstification and collapsing, which are still active processes. This age and genesis hold good for all those large depressions in the Iraqi Southern Desert.

Some of the cities in Kurdistan Region of Iraq depend completely on the groundwater, as a main source of water in their water supply systems, where the cities are too far from surface water resources, and because the mountainous topography of the land makes the transformation of surface water for long distances, too difficult. One of those towns, which depends on the groundwater, as one of the main sources in water supply is Koi Sanjak, located in Erbil Governorate, north of Iraq.

In this study, the groundwater is carefully investigated by evaluating the performance of water wells, which are located within Haibat Sultan Mountain; to the east of the city. From the previous geological investigations, the study area includes four geological formations, which are from oldest to the youngest, Kolosh, Gercus, Pila Spi and Fatha formations. The deep wells are drilled within Pila Spi Formation, the lithology consists of fissured marly limestone, thickness of the aquifer ranges between (149 – 188) m, this type of formation is considered as a good aquifer for the groundwater accumulation. For the study of the hydraulic characteristics of the aquifer, five deep wells were selected. The single well test method was used for analyzing the well characteristics; since observation wells are not available in the studied area. Pumping test data are analyzed to obtain the hydraulic properties of the aquifer, such as transmissivity, coefficient of permeability, specific capacity and specific yield. The pumping test also gives information about hydro-geological properties of the aquifer, such as the type and thickness of the aquifer.

The previous geological investigation in Haibat Sultan Mountain exhibits, that Haibat Sultan aquifer is of unconfined type; while the results of the current study exhibit that the aquifer varies from unconfined, at some location to leaky aquifer in others. This may give an expectation that the slope sediments on the overlying layer may act as aquitard and causing the aquifer to behave as a leaky aquifer. The current total yield of Haibat Sultan aquifer is 1194 m3/day.

The studied area, which includes the Nukhaib Depression extends from Wadi Ubaiyadh in the south to Wadi Ghadaf in the north. The depression is marked by the outcrops of a N – S strip of alluvial fans. The gravity field as observed on the Bouguer anomaly map, scale 1: 500 000, is found to decrease by 8 mGal over the area. This reduction in gravity is argued to be related to a widespread subsurface solution, which has reduced the average density of subsurface rocks. The gravity map further shows local undulations, which when isolated, produce positive and negative anomalies that are distributed irregularly over the whole area including the depression strip. These anomalies are interpreted as due to variations in the intensity of subsurface solution, which reflects the local nature of rocks. Intense solution at some locations forms local subsurface basins of dissolved, broken and collapsed rocks of average low density. It was found that these basins cause topographic down warping. Some of these basins occur below parts of the depression. The alluvial fans are thought to have been formed over these depressed topographic locations. It is emphasized that solution basins are not confined to the depression's outlines only and, as such, these outlines should be reviewed and so should the naming of Nukhaib graben.

The present study aims to verify the aeromagnetic shallow source anomaly that appears at Bahr Al-Najaf Depression and to determine its source. The studied area is completely covered by Quaternary sediments, which are almost composed of sandy sediments. A ground magnetic survey includes 557 magnetic measuring points, distributed mainly on five profiles ranging in their lengths from (0.7 – 16) Km, have been measured in the area. The comparison between aeromagnetic profile and geomagnetic profile has shown a coincidence between them in the regional field. On the other hand, local magnetic anomalies (LMA) have been well recognizable on geomagnetic profiles. The combination of the effect of these LMA seems as similar as that of the aeromagnetic anomaly. Accordingly, the residual aeromagnetic anomaly of Bahr Al-Najaf Depression, which appears related to deep source, can be interpreted as due to accumulations of sediments containing little amounts of magnetic minerals. The source of the LMA has been defined by collecting samples from three separated sites. Results of XRD identifications and heavy minerals laboratory showed the presence of magnetite particles among the sandy sediments.

High grade calcium montmorillonite claystone (calcium bentonite) sample from Wadi Bashira region, Western Desert, Iraq, was activated with sodium by a dry grinding procedure and subsequently evaluated for use as drilling fluids to conform API specifications. Sodium carbonate (Na2CO3) was used to do the activation and convert calcium bentonite to its sodium form. This ion exchange was demonstrated by X-Ray diffraction patterns, wherein the main Ca-montmorillonite d (001) peak changed from 13.6 Å to 11.7 Å. The rheological properties of the activated sample were highly improved, but the sample failed to fulfill API drilling mud requirements. It was observed that certain additives (organic sodium salt and/ or Na-CMC) when added with Na2CO3 can improve the rheological properties of the activated bentonite sample so as it can be used as a drilling mud. The amounts of these additives and that of Na2CO3 were optimized and a bentonite having all API specifications was produced. Experimental results showed that an amount, not exceeding 1 wt.% of these additives with 6 wt.% Na2CO3 is optimal. Accordingly, it can be claimed that the application of this method is economically viable compared to wet activation as it saves water, energy and time.

In this research a preliminary beneficiation study was conducted on a sample from Ardhuma silica-sand deposit in the Iraqi Western Desert, to provide a raw material for silicon industries. The beneficiation processes applied were vibration screening (dry and wet), attrition scrubbing and magnetic separation (dry and wet). These techniques were used individually or in combination to upgrade the sand to produce quartz-sand meeting the requirements of Metallurgical-Silicon production. This would be the base material for silicon materials and Solar-Grade Silicon.
Quartz-sand fulfills the requirements of the State Company for Mining Industries and Aquatic Insulation for the raw materials of MG-Silicon production, which was produced by applying one of the following beneficiation routs: The first consists of autogenesis grinding, dry screening on 150 µ, attrition scrubbing and wet screening on 150 µ. Whereas, the second includes autogenous grinding, dry screening on 150 µ and dry magnetic separation using magnetic field intensity of 16.5 Kilogauss.

This research investigates the hydrogeology and hydrochemistry of the aquifers in Badush Dam site. The area is located in the central northern part of Iraq, about 40 Km south of Mosul Dam in Nainawa Governorate.
Alan anticline is the most prominent geological feature in the studied area. The bulk of the anticline is mainly covered with rocks of Fatha Formation; overlying the Jeribe and Euphrates formations, which form the core of the anticline.

The Jeribe Formation, which is the main water bearing formation in the studied area is composed of recrystallized, dolomitized, porous, fractured, and karstified limestone. The fact that the formation contains several semi-confined beds; isolated by lenses of clay and marl makes it of multi-confined type. It should be mention, however, that the formation is hydraulically continuous. Furthermore, the data indicate that Tigris River has no effect on the aquifer. In addition, the hydrogeological conditions showed existence of a perched aquifer on the left bank of Tigris River with a limited areal distribution.
Karst phenomenon is formed in gypsum and to a lesser extent on dolomitic limestone. Karst areas normally have caves developed as a result of dissolution along joints, bedding planes, or other fractures. Karst phenomenon affects the type of the groundwater, and increases the discharge.
The rock units are affected by many geochemical changing that modified the major anions and cations. The most significant changes are: ionic exchange, escaping of CO2 from the soil, reduction of sulfate by biochemical methods, oxidation of sulfate minerals, replacement, recrystallization, dissolution, dolomitization, and dedolomitization. The groundwater was found to vary considerably in terms of chemical and physical properties before the construction of Badush Dam during 1988 (which has not been accomplished later on) and through the operations of dams drilling through 1989 and 1990. The physical properties include many parameters such as: temperature of water, electric conductivity, pH, ionic strength, and saturated index. Principal component analyses were used to delineate the main chemical constituents. Generally, the water through the year 1988 was neutral to slightly alkaline (pH = 7 − 8.9), low in conductivity, slightly brackish to fresh, hard to very hard and contaminated with H2S gas. Through the years 1989 and 1990, the groundwater constituents became more mineralized, slightly acidic to slightly alkaline (pH = 6.7 − 7.9), higher in conductivity, salinity, and hardness.
The groundwater composition in the Jeribe Formation aquifer is largely controlled by calcite and dolomite dissolution and cation exchange. The caves, sinkholes, and karst forms contribute considerably to the concentration of major ions in the groundwater.

Using the results of the chemical analysis of water samples, the water type proved to be mainly of Ca – HCO3 type, and Ca – SO4 type. In special areas, at the left bank of the river, there was a mix between the carbonated and sulfuric water.