Mineral Chemistry of Chalki Basalts in Northern Iraq and Their Petrological Significance

Chalki basalts as a small body of volcanic rocks have green to grayish green color due to their nearly complete alteration to chlorite. The essential minerals of Chalki basalt to andesitic basalts are plagioclase (labradorite, An51–61; andesine, An35 to An42; and oligoclase, An22). Moreover, there is sodic plagioclase (albite, An0.1 to An04) whose coexistence with the other more calcic plagioclase means that albitization had occurred. The other essential mineral is pyroxene (endiopside, en66–68 wo27–28 fs05–06; and subcalcic augite, en72 wo14 fs14). Olivine (Fo80–81) is also present. According to the NiO content (0.11–0.12 wt%) in olivine grains, they are interpreted to be originated tectonically. The prevalent chlorite in all the samples is mainly diabantite and penninite, indicating chloritization after the ferromagnesian olivine and pyroxene. Serpentine (type lizardite and chrysotile) is also recorded as lesser alteration product after the forsteritic olivine. Rare secondary hornblende (type magnesiohornblende) is also found. The spinel group as accessory minerals is defined as magnetite, chromian magnetite, and chromian spinel giving the imprints of their metamorphic origin due to low temperature sub-sea metamorphism and also of alpine type

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

المعادن الثقيله ومصدرها في وحدة صوفي - الباليوزوى الصحراء الغربية - العراق

Heavy minerals analyses were carried out on 10 samples from the clastic Suffi Formation (the Ordovician-Carboniferous unit in the western Iraqi desert). The suite of minerals consists mainly of opaque minerals including pyrite, ilmenite, magnetite and hematite and the non-opaques is represented by zircon, tourmaline, cutile, garnet, epidote, kyanite, staurolite, leucoxene, chlorite and biotite. The nature and occurrence of the above heavy minerals association reflect a source area of the crystalline basement rocks of Iraq. These basement rocks are coomposed of metamorphic rocks and granites complexes. They belong to the Arabian part of African (Nubio Arabian) Precambrian platform.تم تحليل المعادن الثقيلة لعشر عينات من وحدة صوفي القتاتية (وتتبع الاردفين - الكربوني لمنطقة الصحراء الغربية في العراق ) . ويشتمل نطاق التمعدن على معادن معتمة وبتكون من بيريت ، المنبت ، ماجنتيت وهيماتيت وكذلك معادن شفافة تشتمل على الزيركون ، النورمالين الروتيل ، الجارنت ، الابيدوت ، الكيانيت والستروليت ، ليوكسين كلورايت وبيوتيت . ان طبيعة وتواجد هذه المعادن يدل على مصدر صخور تتبع صخور القاعدة في العراق والتي تتكون من صخور متحوله وجرانيت وتتبع الدرع العربي الأفريقي (العربي - النوبي ) من الزمن البريكاميري

Solid bitumen in shales from the Middle to Upper Jurassic Sargelu and Naokelekan Formations of northernmost Iraq: implication for reservoir characterization

Petrographic, organic, and inorganic geochemical analysis of the solid bitumen and host shales from the Middle and Late Jurassic-age Sargelu and Naokelekan Formations of the Banik section, northernmost Iraq, was undertaken. The aim was to understand their derivation and preservation, as well as examine the carbon and oxygen isotopes, and paleoredox proxies under which the solid bitumen and host sediments were deposited. Petrographic analysis of both formations revealed the presence of solid bitumen high reflectance (first phase) and solid bitumen low reflectance (second phase). The equivalent vitrinite reflectance indicates that the solid bitumen of the two formations probably accumulated within the shale reservoirs following oil migration from source rocks located within the same formations. Mineralogical study (XRD and SEM - EDX) revealed that the shales hosting the solid bitumen also contain clay minerals (illite, rectorite, chlorite, montmorillonite, and kaolinite) as well as carbonate minerals, quartz, alkali feldspar, and pyrite. Carbon and oxygen isotope data along with paleoredox indicators suggest that both the solid bitumen sources and host shales in both formations formed within a shallow-marine setting, most probably under anoxic conditions where water circulation was restricted.Open Access funding enabled and organized by Projekt DEAL. This study is supported by the Arab-German Young Academy of Sciences and Humanities (AGYA) grants (AGYA_2020_AP_01).Peer reviewe

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..

Depositional and burial history controls on the diagenetic evolution of interbedded sandstone and shale: application to the Ordovician Khabour Formation, Iraq

Petrographic (optical, scanning, and backscattered electron microscopy), mineralogical (X-ray diffraction) compositional analysis of interbedded sandstones and shales from the Ordovician-age Khabour Formation of western Iraq were investigated in order to determine the diagenetic evolution of these units. The Khabour sandstones are generally quartzarenites with subordinate sublitharenites and subfeldsarenites which were deposited in a range of shelf environments (offshore shelf through tidal-storm regressive middle shelf to near-shore inner shelf). Several diagenetic events have affected the Khabour sandstones including compaction, cementation, replacement, dissolution and alteration. Early diagenetic events were closely related to the composition of depositional water (especially in terms of oxygen and sulphate content), Fe and organic content of the sediments, rate of sedimentation, and proximity to the shoreline. Shales interbedded with the sandstones contain evidence of authigenic illite, chlorite, kaolinite and mixed-layer illite-smectite. The later diagenetic events within the Khabour Formation were related to the burial history of the sandstone and shale succession as it was deposited on the slowly-subsiding shelf. Typical features include quartz overgrowths, the development of authigenic kaolinite, chlorite and illite, albitization, as well as Fe-dolomite and titanium and ferruginous cementation that resulted in decreased permeability by reducing pore-throat openings in the studied sandstones

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

Depositional environment of the late Paleocene-early Eocene Sinjar Formation, Iraq: Implications from facies analysis, mineralogical and geochemical proxies

Reconstruction of the depositional environment of the Paleocene-Eocene Sinjar Formation from two outcrop sections in northwestern and northeastern Iraq has been evaluated using the traditional petrographic and facies analysis supported by X-ray diffraction and scanning electron microscopy with a focus on the Paleocene-Eocene (P-E) transition boundary. To this end, major and trace elemental geochemistry was conducted and various paleoenvironmental proxies for the paleoredox, paleoclimate, paleosalinity and paleoproductivity were determined in order to evaluate the changes in widely acknowledged environmental and climatic indicators and the elemental enrichment/depletion across the P–E boundary. The redox-sensitive trace element enrichment and the ir ratios (V/V + Ni, V/Cr, and U/Th) indicate that normal oxygenated circumstances prevailed during the late Paleocene deposition, and that anoxic conditions and a gradual commencement of oxygen depletion occurred during the early Eocene deposition. The coeval increase in the P2O5 content, P/Ti, and P/Al ratios in the Eocene sediments suggests an increase in nutrients and primary productivity due to the effect of upwelling currents during early Eocene. The conditions can be verified by observing a small change in salinity levels from low to high across the P-E boundary, which can be indicated by the Sr/Ba ratios. In addition, certain minerals such as Mg-calcite, dolomite, and palygorskite are commonly present, and paleoclimatic changes can be observed across the P-E transition from arid to semiarid and then to humid conditions, which can be recorded from C-values, Sr-Cu, Rb/Sr ratios, and clay mineralogy. These conditions were noted in the Sinjar Formation, which is made up of many microfacies such as lime mudstone, wackstone, packstone, grainstone and boundstone. These microfacies were deposited in a shallow marine environment that extended from tidal flats to reef slopes, with a developed reef environment that included back reef, reef core, and fore reef environments