Silurian Gas-Rich “Hot Shale” from Akkas Gas Field, Western Iraq: Geological Importance and Updated Hydrocarbon Potential and Reservoir Development Estimations of the Field

The Silurian hot shale is encountered in the Akkas field, which is regarded as one of the largest gas fields in Iraq. It contains 5.68 tscf of initial gas in place of which 4.55 tscf is estimated to be recoverable. There is also the potential of condensate and other prospects in deeper formations. The well test confirmed the presence of natural gas with a flow rate of 6–8 MMscfd. Silurian shale contains two organic-rich black hot shale beds that are fissile with high-gamma uranium radiation. Silurian hot shales are geologically important from different sides. Stratigraphically, Silurian graptolites are used to delineate the time transgressive depositional advance of marine clastics across the Arabian Peninsula after the melting of Ordovician glaciers. For assessment of the hydrocarbon generation in the Paleozoic of Iraq, the hot shales of the Akkas Formation are low-sulfur, high-gravity oil, condensate, and gas and are considered as an important gas-rich formation in the region. From petrological and mineralogical view, the presence of distinctive minerals and some elements are important to interpret the depositional and climatic situation at Silurian time. This chapter also sets out assumptions about Akkas gas field development

Lead-, Zinc-, and Iron-Sulfide Mineralization from Northern Iraq

The samples of the mineralization of Pb-, Zn-, and Fe-sulfides were collected from three localities (Dure, Lefan, in the northern Thrust zone; and Sinjar, in the Foothill zone) in Northern Iraq. The geochemical recognition using X-ray diffraction (XRD) affirms the presence of the ore deposit sulfides (pyrite, sphalerite, galena, smithsonite, and cerussite). The characterization of mineral chemistry using electron microprobe analysis (EMPA) gives a clear and exact percentage of each element in each mineral. Fluid inclusions are mostly liquid H2O and/or water vapor, which may also contain lesser soluble salts and slightly ore elements. Some fluid inclusions contain CO2 vapor. This occurrence suggests the presence of two immiscible phases due to boiling at the time of their trapping. They are of epithermal system. The homogenization temperatures and salinities obtained for fluid inclusions can be comparable to those reported for the Mississippi Valley Type (MVT) lead-zinc deposits. It is concluded from the petrographic evidence, fluid inclusions and stable isotope data that lead-zinc mineralization was formed due to deeply circulating high-temperature fluids (brines) within the source basin, or later on by tectonic processes, which possibly contribute in leaching metals from either the diagenesis of host rocks or dewatering of deeper buried siliciclastic beds

Contributions to Mineralization

Contributions to Mineralization provide some new aspects on economically important mineral deposits from various locations in Asia, Africa, and Europe in terms of their genesis, geochemical, and age considerations. Mining industry and mineral engineering issues are also discussed in the book through some new statistical approaches and economic aspects. The book represents a useful guide for specialists in the fields of mineralogy, economic geology, mining engineering, environmental impacts, and mining industry

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