Iraqi Bulletin of Geology and Mining

Karstification is a common phenomenon in different parts of Iraq, where large areas are involved, causing severe damages to infrastructures and occasionally life losses. The main Karstified rocks are limestone and gypsum. The latter is restricted to the Fat`ha Formation, which covers considerable parts of Iraq, especially in the Al-Jazira vicinity. Whereas, the former is exposed in different formations that are exposed almost every where. Among the involved formations are Euphrates, Anah, Dammam, Ratgah, Pilaspi, Aqra – Bekhme, Qamchuqa… etc. Among Quaternary deposits, the gypcrete is another potential deposits that are highly karstified after being in contact, shortly, by water. The gypcrete also covers considerable parts in Iraq.

Beside the economic lost caused due to karstification, some death causalities are also recorded. Moreover, in the Western Desert, karstification plays big role in miss leading the stratigraphic position of different horizons within different Jurassic and Cretaceous formations, making them in very complex situation, although they are in horizontal (not folded) position.

The radioactivity of the marine sedimentary phosphorites of Iraq is investigated and found to be due to uranium. The Late Cretaceous – Early Tertiary phosphorite deposits are generally poor in uranium relative to other Tethyan deposits; they generally contain (20 – 50) ppm U and up to 100 ppm U in the francolite concentrates.
Strong positive correlation exists between uranium with P2O5 and F. Most of uranium is believed to be present in the francolite structure as U4+ substituting for Ca2+. Uranium in the Iraqi phosphorties seems to be generally in equilibrium with its daughter products with minor scattering around the equilibrium line. Secondary uranium minerals are found as metatyuyamunite in phosphorite and limestone, and as carnotite in shale.
It seems that the source of uranium is terrigenous, supplied by U-rich sandstones of older rock units and transported by rivers to shallow marine environments. Geochemical affinity of U towards phosphates and reducing conditions facilitated uranium incorporation in the francolite structure in the early stages of crystallization. The radioactivity of phosphorties provides excellent tool for surface and subsurface prospecting and exploration. But, the presence of uranium in the phosphate fertilizers represents an environmental hazard.

The present study aims to re-study the Qulqula Conglomerate Formation that is mentioned in the previous studies to be about 500 m thick in Halabja – Avroman area. Those studies considered the Qulqula Conglomerate Formation as a part of Qulqula Group which overlies Qulqula Radiolarian Formation and claimed Albian – Cenomanian age and deposited due to the Hercynian Orogeny. They also mentioned that it is deposited in a deep basin of high tectonic activity in which the flysch is deposited and represented by thick succession of conglomerate and shale. In the present study, all the previously mentioned characteristics concerning tectonic, age and facies of the formation in the Avroman – Halabja area are not observed. More than that, the occurrence of the conglomerate that can be called “Qulqula Conglomerate Formation” is doubtful, in this area. The authors have found a thick accumulation of conglomerate but it does not belong to Qulqula Conglomerate Formation. This is achieved according to following four facts: The first fact is that the observed conglomerate beds have dip angles nearly the same as that of the slope of the southwestern side of Avroman and Suren mountains. The second fact is that they are not covered by any strata, except soil. The third fact is that almost all clasts are derived from Avroman Limestone, which is located at higher elevation. The fourth fact is that the conglomerates overlie Qulqula Radiolarian Formation in an angular unconformity. From these four facts it was inferred that the conglomerate has the origin of proximal alluvial fan (fanglomerates), talus and slide blocks and debris that are deposited during Quaternary. It was also ascertained the absence of so called wildflysch in previous studies.

Detailed subsurface sedimentological study had shown that the sediments of Injana Formation (Late Miocene) in the area extended from Baiji to Samarra cities, central part of Iraq were deposited in fluviatile meandering channels system. These sediments represented by several large scale fining-upward cycles. In each cycle, two main facies were recognized; coarse grained sediments (facies 1) and fine grained sediments (facies 2). The coarse grained sediments facies represent channel deposits and are divided into two subfacies; intraformational conglomerates and sandstones. The fine grained sediments facies represent overbank environment and are divided into four subfacies; alternated claystone and/ or mudstone and siltstone sediments, mudstone and claystone sediments, coarsening-upward and small scale fining-upward sequences and carbonates.
It is believed that vertical crustal movements during Miocene were an important factor in the repetition of large scale fining-upward cycles. However, the coarsening-upward and the small scale fining-upward subfacies, which are random in nature and interrupted the flood plain sediments might be related to the overbank sedimentation produced by crevasse splays.

The exposed formations in the studied area in upward sequence are: Euphrates, Nfayil, Injana, Zahra and Dibdibba. Nfayil Formation consists mainly of two main cycles in the studied area (in some places a third sub cycle is developed); each cycle consists of lower marl unit and upper carbonate unit.
More information has been added to the stratigraphy of the area. A unit consists of alternation of red claystone, siltstone and sandstone which was considered the Upper Member of Nfayil Formation in the previous works has been added to Injana Formation, in the present work based on solid field data. The lower and upper contacts of Injana Formation have been reviewed and defined exactly. In addition, the formation is divided into two units in the present work, these are: the Lower Clastic Unit, which consists of alternation of red to reddish brown claystone, siltstone and sandstone with some thin marly limestone horizon, and the Upper Cave – Forming Claystone Unit, which consists of brown to reddish brown cave –forming claystone, topped by thin marly limestone bed. Clear interfingering between Zahra and Dibdibba Formations is recorded particularly in Lissan area, which indicates that they are of the same age. The contacts between the formations are defined clearly in an area, which is considered to have high economic potential such as celestite, attapulguite and feldspar.

Engineering geological study was carried out to evaluate the slope stability of a road cut in a tourism area, north of Sulaimaniya Governorate. The study involved geotechnical evaluation of the area including engineering and petrophysical tests.
Two formations are exposed in the studied area, Cretaceous in age. These are Kometan and Balambo formations, both of them consist mainly of bedded limestone. The area is affected by tectonic uplift due to Alpine Orogeny, forming two set of joints of NE – SW and NW – SE directions.
For the first time, direct shear test is introduced to get the most important parameters concerning slope stability (cohesion and friction angle). For station No.(1) sliding is more possible along planes of tectonic joints (J1), while that of station No.(2) sliding is along bedding planes. Both slopes are considered unstable, where planner sliding is dominant especially in the second station.

This paper deals with evaluation of the physical, chemical and mineralogical properties of mudstones sediments of Neogene age (Injana and Bai Hassan formations) and their suitability to use them as raw material in manufacturing of building bricks, instead of recent sediments of alluvial plain. The study based on the field reconnaissance for five sites within the Foothill Zone. Twenty channel samples were collected from the best exposures of these sediments and 300 brick samples of laboratory size (7 x 3.72 x 2.5 cm) were evaluated, starting from drying and firing stages to evaluating stage. The results show that the sediments are suitable raw material for manufacturing of building bricks of classes A and B, according to the requirements of specification of the Iraqi standard No.25 for the year 1993. These sediments are characterized by presence of two textural classes: mud and sandy mud, which contain no more than 50% of non-clay minerals and less than 50% of clay minerals. The latter dominated of mixed layer of Palygorskite – Illite, with proper plasticity and exhibited low sensitivity for drying. The best temperature for firing bricks is 950º C for the raw material in the southern parts of the Foothill Zone, which led for appearance of new mineral state represented by Augite and 850º C for the raw material of its northern parts which is attributed for disappearance of the original composition of the raw material and appearance of new minerals state, represented by Wallastonite and Gehlenite – Diopside.

The slag formed from the stainless steel production in electric arc furnace contains 23% Cr2O3 on average. Extraction of chromium and recovery of pure chromium oxide from powdered slag using alkali (NaOH or Na2CO3) roast/ water leach process was investigated on laboratory scale. With NaOH, optimum extraction conditions were roasting a charge containing a mixture of the hydroxide and slag in amount of 2:1 by weight at (400 – 500)º C for 60 min, followed by leaching in water at 3 : 1 (liquid : solid) for 30 min. At these conditions 100% extraction was achieved. NaOH roasting involved transformation of high amount of silica (SiO2) and alumina (Al2O3) present in the slag into materials capable to dissolve in water. This resulted in high level contamination of the extraction solution by these impurities. Optimum conditions for extraction chromium by Na2CO3 roasting were roasting a mixture of Na2CO3 and slag in ratio of 1 : 1 by weight at 850º C for 90 min, followed by water leach at the same condition used with NaOH roasting. The chemical analysis results of the extraction solution (chromate solution) reveals that the solution is almost free from silica and alumina contamination. Chromium extraction of 98.5% was achieved. Recovery of chromium from this solution was about 99.98% Cr in the form of Cr(OH)3,from which green Cr2O3 with purity of 99.96%, was obtained.