Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock Efficiency

Evaporites (gypsum and anhydrite) of the middle Miocene age (Fat’ha Formation) form one of the main sulfate cap rocks in the Middle East oilfields. Detailed petrographic and diagenetic investigations accompanied with geochemical analysis of these evaporite rocks in Mosul and Kirkuk areas of northern Iraq have revealed that nodular gypsum is the dominant type, whereas laminated, structureless, and secondary (selenite and satin spar) also are present. Nodular gypsum was deposited in a very shallow, arid, and semi-restricted lagoonal environment which has undergone influx and reflux processes, while laminated gypsum may represent pulses of freshwater into the lagoonal basin of Fat’ha Formation. Low strontium values of the secondary and laminated gypsum may attribute to their secondary origin by hydration processes from the original anhydrite. Based on petrographic, diagenetic, and petrophysical (porosity and permeability) properties, it appears that the efficiency of the Fat’ha sulfates as petroleum cap rocks increases with increasing nodular growth and compaction degree. The occasional presence of bitumen inclusions with both nodular gypsum and host materials relates to early leakage of the hydrocarbons which were being halt due to the growing and packing of nodules and host materials

Natural Pollution By Some Heavy Metals in the Tigris River, Northern Iraq

Twenty samples of the recent sediments were collected from the Tigris River and some of its tributaries of northern Iraq and twelve samples from the Miocene and Quaternary sediments. The study is conducted to define and assess the paleoenvironmental pollution by some heavy metals in these sediments in order to elucidate the probable source rocks and the main mineral phases suggested to be a source of such pollution by using X-ray diffraction, X-ray fluorescence and scanning electron microscopes analyses. The study indicates a polluted level of some heavy metals mainly Cr, Cu, Ni, Pb and Zn. Clay and heavy minerals may form the main sources for this natural pollution. The combined affects of mechanical attrition and chemical etching during the transportation by the river water are indicated through several morphological characteristics on the surface textures of the heavy minerals. The high concentration of some of the studied trace elements could be attributed to incorporation of such elements in the lattice of the heavy and clay minerals

Clay minerals and organic matter from deeply buried Ordovician-Silurian shale in western Iraq: implications for maturity and hydrocarbon generation

The present work is conducted on the Paleozoic (Ordovician) Khabour and the (Silurian) Akkas shales in the Akkas-1 well of western Iraq aiming to determine the implications of clay mineral transformation and organic mineral distribution and maturity for hydrocarbon generation using X-ray diffraction (XRD), scanning electron microscopy (SEM) in addition to organic matter concentrates. In the shale of the Khabour Formation, amorphous organic matter is common and includes various Tasmanite-type organic matter, vitrinite, inertinite and bituminite. The main clay minerals observed include; illite, chlorite, kaolinite, in addition to mixed-layer illite-smectite and rare smectite. In Silurian shale, a lot of organic matter is recorded in addition to abundant vitrinite, some grainy organic matter (Tasmanites) and pyrite with common illite, kaolinite in addition to chlorite and illite-smectite clay minerals. Conversion of smectite to mixed-layer illite-smectite (I-S) and increase in vitrinite reflectance are commonly observed below 2500 m depth in the studied formations and this coincides with oil and gas generation. These results could be used as an indication of higher maturity and hydrocarbon generation in the deeply buried shale of the Khabour and Akkas formations in western Iraq

أغناء معدن الكرومايت في الترسبات النهرية الحديثة، شمال العراق

The Recent sediments from North Iraq are characterized by a higher content of chromite. This paper deals with the mineralogy and geochemistry of chromite in the heavy mineral assemblages from Recent fluvial sediments in an attempt to elucidate its distribution and source rock. The heavy fraction is composed of iron oxides and chromite forming about 50% of the total heavies. Chromite forms up to 80% of the opaque minerals at some areas in North Iraq. The non-opaque heavy minerals are composed of epidote, garnet, tourmaline, rutile, staurolite, kyanite, zircon, olivine, chlorite, muscovite, pyroxene and am-phibole. XRD analysis revealed that chromites are mainly aluminian chromite. Geochemical study shows that chromite is depleted in Fe and enriched in Al, such enrichment being related to the effect of alteration that leaches iron from chromite in the presence of suitable conditions assisting this alteration. Chromite is akin to podiform Alpine-type chromites. Higher concentration of chromite favours the addition of ophiolite complex of the Zagros-Taurus belt as well as recycling of chromite from older formations in North Iraq. Another factor controlling this obvious enrichment of chromite is the hydraulic equivalent and meandering morphology of the rivers.تمتاز الترسبات النهرية الحديثة في شمال العراق بزيادة نسبة معدن الكرومايت ضمن مجموعة المعادن الثقيلة فيها . يهدف البحث الحالي إلى دواسة معدنية وجيوكيميائية معدن الكرومايت في محاولة لمعرفة توزيعه وعوامل اغناءه ومصدره تشتمل المعادن الثقيلة على مجموعتي المعادن المعتمة وغير المعتمة . تؤلف المجموعة الأولى حوالي 50% من مجموع المعادن الثقيلة كما يمثل الكرومايت نسبة أكثر من 85% من مجموع معادنها في شمال العراق . كما تشتمل المعادن غير المعتمة على : ابيدوت، كارنيت، تورمالين، روتايل، ستورولايت، كايانايت، زركون، أوليفين، كلورايت، مسكوفايت، بايروكسن وامفيبول. لقد أوضحت دراسة معدن الكرومايت، بحيود الأشعة السينية أنه من النوع المنيوم كرومايت، كما أظهرت نتيجة تحليله الجيوكيميائي بأنه غني بالألمنيوم وفقير في نسبة الحديد مما قد يعزي إلى تأثير عمليات التغير على الكرومايت ، بفعل عوامل النقل وإعادة الترسيب (دهك الرواسب) الأمر الذي يؤدي إلى زيادة تركيز الالمنيوم على حساب الحديد. إن إغناء الكرومايت في الترسبات الحديثة في شمال العراق قد يعزي إلى تواجده ضمن معقد الاوفيولايت في طوروس - زاجروس وإعادة نقله وترسيبه من عدة تكاوين فتاتية قديمة في شمال العراق ، كما قد تؤدي بعض العوامل الترسيبية والمورفولوجية للأنهار في تركيز وإغناء هذا المعدن

Early Cretaceous calciturbidites facies from Zagros Fold–Thrust belt: a key to paleogeography and environment of northeast Arabian Platform Passive Margin, examples from Kurdistan Region, Northeast Iraq—discussion

Many studies have been undertaken on the structure, origin and geodynamic evolution of the Zagros region and the Arabian Platform Passive Margin (Alavi, 1980, 1994, 2004, 2007; Agard et al. 2005; Ali et al., 2012, 2013, 2014, 2017, 2019, Al Qayim et al. 2012, Lawa et al. 2013; Omar et al. 2015; Mohammad and Cornell 2017; Lawa 2018). Karim (2020) provided an outcomes in his definition of the paleogeography and tectonic setting of Early Cretaceous Arabian Passive Continental Margin. The same thing is true for the Neo-Tethys basin plain and the present Zagros Orogenic Belt. However, Karim (2020) based his findings on the local occurrence of a calciturbidites facies (50 km) within the Balambo Formation-Qamchuqa transitional lateral boundary, thus refining the depositional model along the Arabian Platform and deep basin of Neo-Tethyan sea during the Early Cretaceous in Kurdistan Region of Iraq..

Early Jurassic–Early Cretaceous Calcareous Nannofossil Biostratigraphy and Geochemistry, Northeastern Iraqi Kurdistan: Implications for Paleoclimate and Paleoecological Conditions

Early Jurassic- to Early Cretaceous-age calcareous nannofossils from the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations are investigated for the first time from the Warte area, northeastern Iraqi Kurdistan. A range of isotopic and inorganic geochemical analyses are carried out in order to reconstruct the paleoecological and paleoclimatic conditions during which the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations were deposited. The age of the Sargelu Formation was determined as Bajocian–Callovian based on the first occurrence of Cyclagelosphaera margerelii, Watznaueria britannica, W. fossacincta, W. manivitiae, Watznaueria barnesiae and Watznaueria ovata. Geochemical proxies (Sr, Ca, Al, Rb/Sr, Sr/Cu and Sr/Ba) for paleoclimate and paleoecological conditions, along with oxygen isotopes (δ18O) data, suggest that warm and arid climatic conditions were predominant during the Early Jurassic–Early Cretaceous period