Iraqi Bulletin of Geology and Mining

Microfacies and environmental analysis of Khurmala Formation (Paleocene – Lower Eocene) was studied in the Zenta area, near Zenta village, Aqra district – Kurdistan region Northern Iraq. The formation is composed of 71 m thick bedded grey dolomitic limestone, partially bituminous with chert nodules and rare chert lenses and medium to thick bedded yellow limestone, interbedded with thin beds of marl and mudstone. The petrographic study showed the majority of the limestones are carbonate mud (micrite). The skeletal grains consist principally of benthonic foraminifera, calcareous green algae, ostracods, gastropods, pelycepods, and rare larvae echinoids. Non skeletal grains include peloids only. Three main microfacies were distinguished in the limestones of the studied section and two different lithological units were recognized, based on field evidence and petrographic study. They are in ascending order: thick bedded dolomitic limestone unit and bedded limestone with marl unit. Evidence derived from petrographic study, facies and textural analyses suggest that the Khurmala Formation was deposited in a shallow marine environment of shelf lagoon with circulation, under quiet and semi restricted conditions.

Ten samples were collected from the Eocene sequence of the Naopurdan Group at the Betwat locality within the Thrust Zone of the Sulaimaniyah area, Kurdistan/ Iraq. The samples covered 120 meters of a succession represented by marlstone/ shale, siltstone and sandstone with limestone interlayers and slightly metamorphosed shale/ slate. This succession unconformably underlies a serpentinite rock bed, which is derived from the Mawat ophiolite complex. A biostratigraphic study is carried out for the first time for the calcareous nannofossils present in this sequence and emphasized the age of Middle Eocene. The nannofossil assemblage identified in this study comprises important species that highlights the NP15 and NP16 Zones of the Lutetian stage of the Middle Eocene in the Naopurdan Group. The Sphenolithus spp. included Sphenolithus furcatolithoides, S. cuniculus, S. spiniger, S. predistentus, S. orphanknollensis, S. kempii, S. Runus, S. perpendicularis, S. richteri, and S. moriformis. The Reticulofenestra spp. included Reticulofenestra erbae, R. westerholdii, R. bisecta, R. reticulata, R. minuta, and R. dictyoda. The Toweius spp. included Toweius gammation and T. callosus, together with species like Blackites spinosus, Blackites tenuis and Cyclicargolithus floridanus.

The Qara Dagh anticline is located south of Sulaimaniyah city in the High Folded Zone of the Zagros Fold – Thrust Belt, within the Outer Platform of the Arabian Plate. It is about 116 Km long with a NW – SE trend. The oldest exposed rocks in the anticline are of Paleocene age and belong to the Kolosh Formation; whereas, the limestone beds of the Pila Spi Formation form the flanks of the anticline. The Pila Spi Formation locally forms the carapace of the mountain giving whale-back nature to the anticline. We have conducted in this work a structural – geomorphological study of the Qara Dagh anticline using existing features and form of the anticline, observed and checked by field work; different types of satellite images and updated geological maps (scale of 1: 100 000). Structural, geomorphological and stratigraphic data confirm the lateral growth of the anticline in a NW direction, complemented by the presence of: fork-shaped valleys, axial valleys, radiated valleys, abandoned alluvial fans, and the presence of water and wind gaps. The present study indicates that the Qara Dagh anticline was originally comprised of six smaller anticlines that exhibited lateral and vertical growth leading to the development of one major anticline. The NW propagation of the six segments of Qara Dagh anticline is supported by the presence of two en-échelon plunges within the main anticline. The rate of the lateral growth was higher than the rate of the incision of the streams; therefore, the streams were shifted around the tips of the segments; meanwhile abandoning the water gaps to wind gaps and development of new water gaps around the tips.

Samples from Sarki, Sehkaniyan, Sargelu, Naokelekan, and Chia Gara formations in Bekhme-1 Well, Akri-Bijeel Block about 10 Km northwest of Harir town, Erbil Governorate have been analysed for organic geochemistry. The hydrocarbon potentiality parameters, including type and amount of kerogen and thermal maturity of 34 samples were assessed using Rock-Evalpyrolysis technique. In general, the samples from Sarki and Sehkaniyan formations have production index values of 0.41 – 0.46 (average 0.44) and Tmax values varying between 437 °C and 453 °C (average 445 °C), suggesting early to late thermal maturity stage, but they are considered as poor source rocks, because the total organic carbon (TOC) content ranges from 0.22 to 0.33 wt.% (average 0.28 wt.%). The samples from Chia Gara, Naokelekan, and Sargelu formations can be considered good source rocks with average TOC content of 1.50, 2.86, 1.44, and 0.63 wt.%, respectively. They contain kerogen types II and III, indicating marine and non-marine organic matter proposing oil and gas prone sources.

The carbonate-clastic succession in the studied wells is represented by the Nahr Umr and Mauddud formations deposited during the Albian Sequence. This study includes petrophysical properties and reservoir characterization of this succession in 5 wells within the Nasiriyah oil field. According to values and shape of gamma ray logs and shale values, the studied formations were subdivided into five zones named; A, B, C, D, and E. Three types of rocks were identified in these zones according to their total porosity: Type I: High-moderate active porosity rocks; Type 2: High-moderate inactive porosity rocks and Type 3: Low-non porous rocks. According to the relationship of resistivity-porosity and hydrocarbon saturation two reservoir horizons have been identified in this study within the Nahr Umr Formation. The Mauddud Formation, on the other hand, does not show any hydrocarbon in the studied succession, due to the overwhelming presence of shale strongly affected by diagenetic processes such as cementation and compaction. Horizon 1 appears in the upper sand member of Nahr Umr Formation, encountered in wells No.1, No.2, and No.3. This type of rocks is characterized by high-moderate porosity (effective porosity) with low volume of shale and high deep resistivity. The thickness of this type ranges from 21 m to 48.5 m. Horizon 2 is represented by breaded river lithofacies, occurring in all the studied wells except No.3. It is divided into two sub-horizons in well No.5. This type of rocks is 12.25 – 57 m thick and characterized by high-moderate porosity with low volume of shale and high deep resistivity.

A collection of 11 crude oil samples from 11 oil exploratory wells in 5 oilfields in northern Mesopotamian basin were subjected for geochemical analysis of trace metals and sulfur. The crude oil samples were collected from Guwear, Kirkuk, Tawke, Khurmala, and Taq Taq oil fields. The mean values of vanadium and nickel were 20 and 15 ppm, respectively. Trace metals configurations and constraints helped to explore the depositional environments and used in the geochemical grouping the oils. Based on nickel to vanadium ratio, the crude oils were differentiated into five groups: 1) Tawke-3, Tawke-4, Guwear-2, Shiwashok, and Taq Taq-6; 2) Khurmala-1 and Kirkuk-247; 3) Khurmala-2 and Kirkuk-331; 4) Guwear-3; and 5) Guwear-1. The low ratio of nickel to vanadium (Ni/V<1) in the crude oils of Guwear-2; Shiwashok; Tawke-3; Kirkuk-331; Khurmala-2; Guwear-3; Kirkuk-247; and Khurmala-1 oils indicates oil source of marine environment, whereas, the crude oil source of Guwear-1; Tawke-4; and Taq Taq-6 is non-marine and probably deposited in lacustrine or land. The oils can be arranged from older and more mature to younger and less mature based on V/Ni as Guwear-2, Shiwashok, Tawke-3, Guwear-1, Tawke-4, Taq Taq-6, Kirkuk-331, Khurmala-2, and Guwear-3.

Abnormal concentrations of fresh olivine and pyroxene grains are reported and studied for the first time in the sandstone beds of the Kolosh Formation in the Dyana area, NE Iraq.
The petrologic study revealed relatively high concentrations of fresh pyroxene grains (18.26%), olivine (8.3%), igneous rock fragments of various compositions (11.35%), altered (17.4%), argillaceous rock fragments (3.5%), carbonate fragments (2.45%), chert (2.3%), serpentine and chlorite (6.18%), plagioclase cf. anorthite and labradorite (5.15%), alkali feldspar cf. sanidine (1.02%), quartz and cristobalite (2.56%), opaque minerals including chrome-spinel (4.0%), argillaceous matrix (16.53%) and carbonate cement (1.2%).
These mineralogical assemblages refer to ultrabasic and basic plutonic igneous sources associated with basic volcanic rocks. The ultrabasic and basic source is suggested to derived from mantle and oceanic crust origin, represented by the ophiolite sequence of Hasan Beg, Rayat, Choman and Galalah areas. These ophiolites were thrusted and emplaced during Late Cretaceous and were associated with volcanic island arc. The thrusted ophiolites were subjected to rapid submarine erosion and deposition and/ or subjected to subaerial erosion. Intense wave action accelerated erosion of beach rocks, removing the light fraction and leaving the heavy minerals insitue. Intense tectonism slumped these sediments into deeper margins by the turbidity currents.

The Alanish locality, situated along the northern passive margin of the Arabian Plate, is one of several Zn-Pb-Barite occurrences widespread in northern Iraq (north of Zakho City). The mineralization was emplaced in the Late Permian dolostone of the Chia Zairi Formation and can be seen at the superficial exposures. A scanning electron microprobe coupled with an X-ray energy-dispersive spectrometer (SEM-EDX) was used for the identification of mineral phases. Acanthite (Ag2S) and greenockite (CdS) are reported here as their first occurrence in Iraq within a strata-bound polymetallic sulfide ores of Zn, Pb, Fe, Cu, Ag, and Cd. It is a Mississippi Valley Type (MVT) deposit formed at 120 °C as inferred from Cd fractionation in sphalerite and galena. The metals and sulfur sources are derived from the brines originated from the sedimentary basin rich in evaporate. The average composition of acanthite is 83.9 wt.% Ag and 12.5 wt.% S equivalent to 96.4% acanthite as tiny inclusions of lenticular shape inside galena and smithsonite grains. The remobilization of Cd from the sphalerite lattice resulted in the formation of greenockite with an average composition of 68.9 wt.% Cd and 21.2 wt.% S. The mineralization is dominated by sphalerite and galena with minor amounts of chalcopyrite, pyrite, marcasite, and fewer amounts of acanthite and greenockite associated with dolomite, calcite, barite, and siderite as gangue minerals. The common features of the mineralization are replacement, veins, veinlets, and cavity filling of small paleo-karsts. The fault plane and the secondary permeability formed pathways for the movement of metals-bearing solution into dolostone in which the ore body was accommodated.

The stable isotopes of deuterium (2H) and (18O) together with radioactive values of tritium, enhanced by hydrochemical data were used in the current study to identify the interaction between groundwater and Tigris river water in the city of Baghdad. To achieve this objective, 3 samples of surface water, 3 rainwater samples and 12 samples of groundwater were collected and analysed for 2H, 18O stable isotopes, tritium and hydrochemical analysis. The hydrochemical parameters of both groundwater and surface water samples show similarity in the wells located in the area of Al-Mansour (WK4), Shulah (WK6), Adamia (WR3) Zafarania (WR1) and Diala (WR4), indicating interaction between surface and groundwater in these areas. Moreover, the stable isotopes results show that the difference between the values in groundwater and surface water samples is small and they are close to each other, which also indicates that the surface water in the study area interact with some groundwater, as shown in samples from wells at Al Dora (WK1), Saidia (WK2), Karadha Mariam (WK3), Rahmania (WK7), Zafrania (WR1) and Diala (WR4). The interaction between surface and groundwater in these areas is confirmed by the results of the environmental isotopes (H), where the values are very close in the samples collected from these sites. The present study also showed that the composition of the hydrogen and oxygen isotopes from river water matched with the local meteoric water in the Tigris river basin. This indicates that rainfall has a major contribution to the river water. Therefore, the groundwater might be a mixture of river water and rainwater and the composition of isotopes is controlled by the mixing rates of surface water, internal flow and groundwater components.

The spatial variation of the hydrogeological and hydrochemical characteristics of the main upper aquifers in southwestern part of the Mesopotamia is investigated, based on sampling from sixteen groundwater wells of different depths and locations, drilled by Iraq Geological Survey (GEOSURV) during dry season of 2011. Pumping tests were conducted to evaluate the hydrogeological parameters in these wells. The suitability of groundwater for different uses and the hydrochemical evolution of groundwater were evaluated using the field measurement of the physiochemical parameters (pH and EC) and analyzing the groundwater samples for major cations and anions. The hydrochemical and hydrogeological results were compared with previous hydrogeological data in the area and found them compatible. The Quaternary sediments cover most of the study area and represent the main intergranular-type aquifer, whereas the carbonate rocks of the Euphrates Formation (Lower Miocene) and the Dammam Formation (Upper Eocene) represent the main fracture-type aquifers in the southwestern parts of the area. In general, the groundwater quality in the shallow aquifer of the Quaternary sediments is saline to brine water of chloridic type, except for the zones along the rivers and stream where the groundwater is brackish. The groundwater in the fracture aquifer in the southwestern parts is of sulfate type, brackish to highly brackish water. There is a significant spatial variation in the hydrogeological parameters due to the lateral variation in the Quaternary sediments and the variation in the permeability of the pre-Quaternary sediments. This variation influences the hydrochemical properties of the groundwater in the study area. The main factor that affects the evolution and quality of chloride-type groundwater in the Quaternary aquifer is evaporation, while in Pre-Quaternary fracture-type aquifer the chemical evolution of the groundwater is controlled by the dissolution of the evaporate rocks (gypsum and anhydrite) and the weathering of the carbonate rocks. The groundwater in the Quaternary sediments is not suitable for any use due to the high salinity; whereas the groundwater of the Pre-Quaternary fracture-type aquifer can be used for livestock drinking and to irrigate some salt tolerant crops especially when considering the high infiltration capacity of the sediments.

The study area is located to the west of Makhul hills between north of Baiji City and south of Sharqat City covering a total area of about 526 Km2. Two wells have been sampled in the present study by taking one sample at (1 – 2) m. interval. A total of 19 samples were collected (13 samples from the first well and 6 samples from the second well), taking into account the lithological variations during the drilling process. The samples were characterized as clastic (sand and mud) brown in color and friable. The grain size analysis processes, using dry and wet sieving, revealed that samples of the first well can be classified as sandy mud and mud, while the second well samples are classified as sandy mud, and sandy silt. The sedimentary facies were described according to their fabric and lithology and found that the majority belong to the Injana Formation and Quaternary sediments, occurring in the southwestern part of the area. The order and overlap of these facies in lenses has led to the formation of multi aquifers. The presence of sand layers, with high connected porosity, has enhanced the hydraulic characteristics, and therefore, they worked as aquifer beds or host of ground water. The grain-size cumulative curves showed that the sediments were transported by saltation and suspension which are common mechanics of transportation in fluvial environment. The cumulative curves show a unimodal distribution, which indicates lack of changes in sedimentary environment during deposition. A bimodal distribution was noticed in some samples, whereas limited multi-distribution (polymodal) was found in some samples from the first well, which indicates lack of regularity in the transport energy and result in grain size variation. The chemical properties of the water extracts from the sediments indicate an increase in salinity and calcium concentration at the upper parts due to evaporation with increasing concentrations of organic matter due to human activity. Neutral pH was found throughout the section of the well.