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Global sea-level rise during the Early Turonian-Late Cenomanian Bonarelli event resulted in oceanic anoxia and deposition of organic-rich source rocks across Northern Africa, such as the Late Cretaceous Abu Roash-F carbonates. Here, using thin sections, SEM, XRF, standard core analysis, and Rock-Eval pyrolysis data, we examine the petrographic and geochemical properties of the Abu Roash-F (AR-F) carbonate source rocks. These deep marine carbonates consist of dominantly planktonic foraminifera and calcispheres and are classified as wackestone. Extensive micritization, calcite cementation, and ferroan dolomite cement replacement (filling the bioclastic tests and chambers) are identified as the principal diagenetic factors. Core measurements indicate that these carbonates have very low porosity below 3% and horizontal permeability of 0.003 mD (3x10-18 m2), which is also supported by the observed isolated nanopores in SEM. The elemental concentration from the XRF data confirms a highly reducing depositional environment that facilitated the organic richness during the Early Turonian Oceanic Anoxia Event 2 (OAE2). The studied carbonate interval consists of Type-II kerogen in the oil window with a Tmax of about 440 °C and up to 4.2 wt.% TOC indicating 'fair' to 'excellent' organic richness and a very high probability of active oil generation and expulsion. Following the wireline logs and core data, the self-sourcing unconventional reservoir potential of the AR-F carbonates has been emphasized. • AR-F is dominantly composed of planktonic foraminifera deposited in a marine environment during OAE2. • XRF data indicates a reducing depositional environment that facilitated the organic richness. • Carbonates exhibit poor porosity and permeability due to extensive micritization. • AR-F is organic-rich, composed of type-II kerogen in the oil generation window. • The studied interval is a potential self-sourcing unconventional reservoir. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive reservoir characterization of the channel sandstones of the Pliocene El Wastani Formation from the deepwater Scarab field, in Egypt. Routine core analysis, wireline logs, petrographic thin sections, X-ray diffraction, and drilling data were integrated to characterize the petrographical, petrophysical and geomechanical properties of the studied gas reservoirs to infer the implications for reservoir development. The petrographic analysis indicates fine to medium-grained glauconitic subfeldspathic wacke with dominantly primary intergranular porosity and minor secondary porosity contributed by feldspar dissolution. The reservoir facies exhibit pore-filling detrital clay (dominantly illite, smectite mixed-layer clay) along with minor carbonate and silica cementation. These reservoirs are megaporous and consist of an isotropic pore system, with 20–35 % porosity, 2400–3400 mD horizontal permeability, and 1300–2900 mD vertical permeability. Wireline log-based petrophysical assessments indicate excellent reservoir qualities with low shale volume (9–23%) and high hydrocarbon saturation of about 65–85%. Based on the geomechanical analysis, rock-mechanical properties, pore pressure, vertical stress, and minimum horizontal stress magnitudes were interpreted. The production and depletion-related risks were analyzed by utilizing geomechanical modeling which provided a quantitative assessment of drawdown and depletion limit to ensure sand-free hydrocarbon production without the risk of shear slippage on pre-existing weak planes. Considering the average unconfined compressive strength of 14 MPa, the Pliocene reservoir will require a 9.2 MPa depletion or 16.9 MPa drawdown to reach the onset of sanding, while the reservoir can be depleted to a pore pressure level of 4 MPa before it induces shear slippage on the optimally oriented fractures or fault planes. Inferences are drawn on reservoir quality, and reservoir development strategies are discussed accordingly. • The Pliocene gas reservoirs are composed of fine to medium-grained glauconitic subfeldspathic wacke. • Reservoirs exhibit dominantly primary intergranular porosity and minor secondary porosity contributed by feldspar dissolution. • The reservoirs are highly porous and permeable with high hydrocarbon saturation. • The El Wastani sandstone reservoirs have a gas gradient of 0.07–0.08 PSI/ft. • Solid production risk and depletion-induced reservoir stability are inferred from geomechanical characterization. [ABSTRACT FROM AUTHOR]

Petrographic, mineralogical and whole-rock geochemical investigation of siliciclastic and interbedded carbonate rocks from the Devonian Pirispiki Formation in the Nazdur and Ora sections, extreme northern Iraq, were conducted to assess reservoir potential and to study the effects of Devonian deformation (Middle Paleozoic, Caledonian event) on paleogeography and sediment transport in northern Gondwana. Traditional petrographic and scanning electron microscopy, X-ray diffraction and X-ray fluorescence were used. The main results are: sandstones from the Ora section contain significantly more quartz and less lithic fragments than those from the Nazdur section. This variation in sandstones composition may reflect uplifting effect due to Middle Paleozoic event and/or different provenance. The most notable feature of the major and trace elements distribution in the studied mudstones and sandstones is that they are significantly enriched in U but significantly depleted in Zr and Hf. The relative absence of zircon in the samples could account for the depletion of Zr and Hf, two elements linked to zircon. The extremely high U concentrations seen in mudstones and sandstones may relates to precipitation by circulating groundwater where it transported into the sediment prior to cementation. No fauna or flora have previously been reported from the Pirispiki Formation at outcrop in Iraq. The widespread occurrence of shell fragments in sandstones from the Nazdur section combined with the presence of eight dolomite and dolomitic marl beds suggest that the lower and middle parts of this section were deposited in a marine environment. This has not previously been recognized. Previous correlations between the Chalki basalts in the Chia Zinnar anticline and conglomerates in the Ora anticline are not supported by our data. We propose a new correlation between the sections in northern Iraq and those from southern Turkey and western Iraq that suggests that the Pirispiki Formation was deposited during a relative sea-level fall. The paleo-shoreline advanced northward through the study area during the Late Devonian. The Pirispiki Formation has been proposed as a potential reservoir for hydrocarbons sourced in underlying Paleozoic units. However, the sandstones and carbonates investigated during this study have no potential as a reservoir due to pervasive carbonate cements. • First detailed work on Devonian Red Beds. • Establishing Regional Stratigraphic Correlations. • Reconstruction of Reservoir Characteristics. • Detailed investigation of Depositional Environments (traditional microscopy and SEM). [ABSTRACT FROM AUTHOR]

This study presents the first-ever preliminary assessment of the potential reservoir intervals from the Cambro-Ordovician Shifah Formation of the Shushan Basin, Western Desert. Seismic data, thin sections, XRD, XRF, and wireline logs were integrated to characterize the potential intervals. The study area is characterized by E-W and ENE-WSW trending steeply dipping normal faults creating a series of horsts, grabens, and half-graben structures. Based on the wireline logs-based petrophysical assessment, three potential reservoir intervals are identified with the Shifah Formation below 15000 ft depth. All the promising intervals show little shale volume (10–20 %) and 70–80 % hydrocarbon saturation, but the porosity is dominantly below 10%. The two potential sandstone intervals are composed of quartz arenites affected by silica cementation and mechanical compaction. These glauconite-bearing sandstones exhibit low-angle cross-lamination and planar lamination, likely deposited in a fluvial to shallow marine depositional environment. Both the tight sandstone intervals exhibit E-W, and NW-SE striking, closed, and partially open fractures which can contribute to the reservoir flow capacity. The third potential reservoir interval is an igneous intrusive body, composed of alkali syenite and exhibits secondary intraparticle porosity due to partial feldspar dissolution and minor fractures. The preliminary assessment presented in this work shed critical insights into the reservoir potential of the Shifah Formation. • Fist preliminary assessments of potential Shifah reservoirs are presented. • Out of three potential targets, two are quartz arenite and third one is alkali Syenite igneous body. • Identified intervals are tight but exhibits high hydrocarbon saturation. • Presence of partially open fractures confirmed from the image log. [ABSTRACT FROM AUTHOR]

The Rosh Pinah Zn–Pb–Ag deposit in southern Namibia comprises a significant sulphidic Zn–Pb resource (19.94 Mt @ 7.3 wt% Zn, 1.83 wt% Pb and 27.7 g/t Ag) occurring mainly as sphalerite and galena. The ore minerals as well as pyrite are hosted by the Ore Equivalent Horizon (OEH), a part of the Neoproterozoic Rosh Pinah Formation. Details on original rock types and depositional environment of the OEH units remain unclear despite past work. Here, we combine detailed drillhole logging data, drillhole logging database and drillcore photographs, underground and near-mine outcrop observations coupled with detailed petrographic observations to elucidate original rock types and depositional environments. The OEH is comprised of three mappable lithofacies (carbonaceous argillite and siltstones, volcanic/volcaniclastic rocks, and carbonate rocks) enclosed within a sequence of arkose. The lateral transition from coarse-grained arkose to the fine-grained carbonaceous rocks of the OEH reflects subaqueous fan type deposition. The presence of diagenetic textures in the carbonate rocks in form of cloudy, isopachous fibrous dolomitic cements point to subaqueous depositional environments. The geometry of carbonate bodies in the OEH at the Rosh Pinah mine and in nearby surface outcrop exposures suggest local accumulations with a pronounced topographic relief above the surrounding sediments, reminiscent of carbonate buildups. The OEH appears to represent a limited interval of marine or lacustrine deposition that may be related to syn-sedimentary extensional conditions. • Integrated logging, mapping, facies correlation, and petrographic work at the Rosh Pinah Zn-Pb Deposit, Namibia. • Host rocks form lenticular bodies, lateral transition from coarse-grained arkose to a variety of fine-grained rocks. • Additional depositional insights from newly described carbonate diagenetic textures and morphologies. • Ore mineralisation controlled by limited intervals of marine/lacustrine deposition related to syn-sedimentary extension. [ABSTRACT FROM AUTHOR]

Petrographic studies, geochemistry, δ13C and δ18O isotopes have been used to characterize the well-preserved carbonate depositional environments of the Bobassa and Ndimba unit in the 640-565 Ma Ombella-M'poko Formation, Central African Republic. The carbonate facies are mainly composed of calcite, dolomite and quartz with some accessory minerals (opaque minerals, muscovite and pyrite). The Ca/Mg ratios show that the Bobassa carbonates are slightly metamorphosed dolomitic limestones, while those of Ndimba correspond to slightly metamorphosed highly dolomitic limestones and cipolins. The Bobassa unit recorded a depositional evolution from fluvial to peritidal environments in a possible tectonically active platform as evidenced by changes of lithology and slump structures. The Ndimba was deposited in a tidal-influenced fluvio-lacustrine environment under dry conditions. Geochemistry revealed that the Bobassa and Ndimba units recorded variable redox conditions from anoxic to oxic. The PAAS-normalized REE + Y distributions indicate that the both units were slightly altered by freshwaters and detrital materials in reduced and acidic environments. The lowest δ18O and highest δ13C values suggest warm surface waters and deeper water column respectively. The carbon isotope profiles of Bobassa and Ndimba units show values varying between −0.89 and −0.34‰ that are not stratigraphic coeval with the cap carbonates δ13C profiles deposited in the aftermath Marinoan Glaciation, but rather are correlated to the middle to upper part of the Schisto-Calcaire Group in Gabon and Republic of Congo and the time-equivalent Lukala Subgroup in DRC. • The carbonate facies are mainly composed of calcite, dolomite and quartz. • The study reveals a quiet shallow paleoenvironment with variable redox conditions. • The Bobassa and Ndimba units preserved their primary isotopic signatures. • The O.M.-Fm is not stratigraphic coeval with the cap carbonates. • δ13C and δ18O values express warm surface waters. [ABSTRACT FROM AUTHOR]

Abstract Acoustic velocity and petrophysical parameters of thirteen samples from the Middle Jurassic Ras El-Abd exposure, west Gulf of Suez, Egypt, have been measured and integrated with the petrographical analysis to evaluate the effect of diagenetic processes on the reservoir quality. The average compressional and shear wave velocities of dry (Vp dry) and saturated (Vp sat) sandstone rock samples are lower than those of carbonate samples. The diagenetic processes affected on the acoustic properties of the studied sandstone and carbonate rocks. The neomorphism and cementation processes caused an increase in the compressional and shear wave velocities and a decrease in the reservoir quality as recorded in biomicrite and argillaceous dolomitic quartz arenite microfacies, whereas the dissolution and leaching processes caused a decrease in the acoustic characteristics and an increase in the reservoir quality as represented by quartz arenite and ferruginous quartz wacke microfacies. In order to decrease the cost of acoustic analysis, the estimated empirical equations can be used for the prediction of compressional wave velocity of wet rock samples from the compressional wave velocity of dry rock samples, and the shear wave velocity of wet rock samples can be predicted from the shear wave velocity of dry rock samples. The correlation of the relative sea-level change for the studied section according to facies changes with the global fluctuation revealed that, the lower interval of Bajocian age is dominated by a fall in sea-level manifested by the deposition of quartz arenite microfacies and hence has a higher reservoir quality than the upper part of the succession. Highlights • Impact of facies type and petrophysical characteristics on the reservoir characterization. • Four microfacies type were defined based on the textural and the mineralogical composition. • Lower interval of Bajocian age (regression) has high reservoir quality than the upper one. [ABSTRACT FROM AUTHOR]

Abstract Sandstones of the Qal'eh Dokhtar Formation west of Boshrouyeh, Central Iran, were analyzed for Petrographic and geochemical (major and selected trace elements) to infer their provenance, intensity of palaeoweathering of the source rocks and tectonic setting. This formation is composed mainly of alternating marine sandstones, laminated greenish to light gray shales with well bedded gray limestones. Texturally, these sandstones are fine grained, subangular to subrounded and moderately to well sorted. Based on the petrographic study, modal analysis and geochemical data, they can be classified as quartzarenites and sublitharenites. The provenance and tectonic setting of theses sandstones have been assessed using integrated petrographic and geochemical studies. Petrographic data suggest that the sediments were derived from plutonic rocks. Petrographic analysis reveals recycled origin and craton interior setting were the dominate source. The geochemical investigations are recommended that these rocks were originated from quartzose sedimentary source. Chemically, major and trace element concentrations in the sandstones indicate deposition in a passive continental margin setting. Average CIA, CIW and PIA values (69%, 75%, and 72%, respectively) imply moderately to high degree of chemical weathering, which may reflect humid climate condition in the source area. The petrographic analysis, geochemical data and palaeogeographical models confirm that the Qal'eh Dokhtar Formation sandstones generally consequent from mature recycled continental sedimentary rocks and deposited on the passive margin alongshore setting of the Neotethys Ocean. Highlights • Modal analysis (QmFLt) show the sandstones of Qal’eh Dokhtar Fm. located in the recycled origin and craton interior field. • The geochemical characteristics suggest the passive margin setting for these sandstones. • The CIA, CIW and PIA values are indicative of moderately to comparatively high weathering in the source area. [ABSTRACT FROM AUTHOR]

This study aims to establish the diagenetic evolution of carbonate rocks of the Barremian-Aptian Tirgan Formation (Kopet-Dagh Basin, NE Iran), with special emphasis in their impact on reservoir quality to be used as analog for their equivalent carbonate reservoirs. To achieve this target, basic petrography complemented by elemental and stable isotopic (δ 18 O and δ 13 C) analyses of the studied carbonate rocks was used. In addition, the visible porosity was detected. The recognized carbonate diagenetic processes include micritization, cementation, dolomitization, compaction, dissolution, stylolitization, fracturing, silicification and neomorphism. These diagenetic processes took place in four diagenetic environments: marine-phreatic, meteoric-phreatic, meteoric-vadose and burial. Early dolomitization of lime muds, micritization of skeletal allochems and cementation by isopachous equant calcite represent marine-phreatic diagenesis. The meteoric-phreatic diagenesis was accompanied with the development of granular non-ferroan calcite cement, neomorphosed carbonate matrix and recrystallized bioclasts. The meteoric-vadose diagenesis led to prevalence of dissolution process and sparry calcite infilling the fractures. Late dolomitization, ferroan blocky and poikilotopic calcite cement, stylolitization and silicification processes were developed during burial diagenesis. An integration of the petrographic study with the geochemical analysis confirms that the studied carbonate rocks were originally composed of aragonite, which was eventually recrystallized to calcite and replaced by dolomite during diagenesis. In terms of reservoir quality, the recognized diagenetic alterations and visible porosities show that the diagenetic processes have a direct effect on modification of both inter- and intra-granular/crystalline porosity. In this manner, it is found that the calcite cementation, micritization and compaction decline the pore spaces, whereas the dolomitization, dissolution, formation of moldic pores and fracturing increase the pore volumes. Consequently, prevalence of dolomitization, dissolution, occurrence of moldic pores and fracturing in the Tirgan carbonate rocks gives the Tirgan Formation and its equivalent rocks a good opportunity to be an excellent reservoirs. [ABSTRACT FROM AUTHOR]

The megabreccias in the Katanga part of the Neoproterozoic Central African Copperbelt contain up to several km-long blocks and fragments of the Mines Subgroup which host most of the stratiform Cu-Co deposits. New observations, particularly on cores from boreholes drilled at Luiswishi indicate three types of fracturing: 1) brittle post-folding in the Mines Subgroup; 2) hydraulic; and 3) ductile in soft incompetent siltstones of the R.A.T. and Dipeta subgroups. These fracturing phases dislocated the Roan succession into blocks and fragments and, in particular, clearly showed that there is an evolution from an in situ hydraulic fracturing, to a heterometric brecciation implying some movement and abrasion of the fragments. The process points to significant compression, and was accompanied by fluid expulsion and precipitation of dolomite after decompression. Fluid inclusion microthermometry in dolomite grains shows that the fluids were of high salinity and high temperature, suggesting dissolution of evaporites most likely contained in the Roan sedimentary pile. These saline fluids allowed the fluidization of the breccias, facilitating the displacement of the nappes, pinching out (extrusion-like) megabreccias along thrust-faults, and resulting in intrusion of breccias between the blocks or into large fractures. Breccias between the blocks are clearly identified as friction breccias. They contain a fine material, as part of the matrix, resulting from abrasion of the fragments during transportation. Abrasion and attrition explain the rounding of the fragments. A late cementation phase from less saline and lower temperature fluids suggests the addition of meteoric water in the system, and the mixing with the ambient fluids. The minimum burial depth of the meteoric water incursion is estimated at 2.8 km. Such under-saturated fluids may have contributed to the dissolution of residual evaporites and of the evaporitic material from the Kiubo rocks at the base of the nappes, and led to further brecciation, possibly explaining the multi-phase features of the breccia. The megabreccias occur at the base of the thrusts sheets and are marked by thrust-fault zones. Results of the study support a process of formation of the megabreccias related to a fold-and-trust event, and invalidate a syn-orogenic sedimentary origin as an olistostrome formed by subaqueous conglomeratic debris flows and clastic syn-orogenic sediments. They also contradict a pure salt tectonic hypothesis that propose the extrusions and enlargements of allochthonous evaporites-gigabreccia before the Lufilian deformation. However, the model is compatible with a “fluid behaviour” of pressured saline fluids trapped in folds and/or thrust sheets, and resulting from evaporites dissolution at variable depth. [ABSTRACT FROM AUTHOR]

The Archean spherule layers (SLs) of the Barberton Greenstone Belt (BGB, South Africa) and Pilbara Craton (Australia) are the only known evidence of early, large impact events on Earth. Spherules in these layers have been, alternatively, interpreted as molten impact ejecta, condensation products from an impact vapor cloud, or ejecta from impact craters melted during atmospheric re-entry. Recently, a new exploration drill core (CT3) from the northern BGB revealed 17 SL intersections. Spherules are densely packed, sand-sized, and variably rounded or deformed. The CT3 SLs are intercalated with black and brown shale, and laminated chert. The determination of the original number of impact events that are represented by these multiple SLs is central to the present paper. A comprehensive study of the sedimentary and petrographic characteristics of these SLs involved the determination of the size, shape and types of individual spherules, as well as their mineralogy. CT3 SLs consist of K-feldspar, phyllosilicate, siderite, dolomite, quartz, Ti- and Fe-oxides, as well as apatite. In addition, small amounts of carbonaceous, presumably organic material are observed in several spherules at 145 and 149 m depth. Only Ni-rich Cr-spinel (up to 11 wt% NiO) crystals, rare zircon grains, and alloys of platinum group elements ± Fe or Ni represent primary phases in these thoroughly altered strata. The 0.3 to 2.6-mm-sized spherules can be classified into four types: 1. Spherules crystallized completely with secondary K-feldspar (subtype 1A) or phyllosilicate (subtype 1B); spherules completely filled with Ti- and Fe-oxides (subtype 1C); spherules containing disordered or radially oriented, fibrous and lath-shaped K-feldspar textures (subtype 1D); or subtype 1B spherules that contain significant Cr-spinel (subtype 1E); 2. zoned compositions with these types 1A and/or 1B minerals (subtype 2A); spherules that contain central or marginal vesicles (subtype 2B); subtype 1B spherules whose rims consist of Ti and Fe-oxides (subtype 2C); 3. deformed spherules (subtype 3A) - of all types; (B) subtype 1B spherules are assimilated into groundmass; (C) open spherules or spherules with collapsed rims; and 4. interconnected spherules of type 1A. A few spherules show botryoidal devitrification textures interpreted to result from rapid cooling/devitrification of former melt droplets. SL 15 at a depth of 145 m is unique in being the only grain-size sorted SL; this bed may have been deposited by fallout through a water column. The SL and their host rocks can be easily distinguished by their significant differences in micro-XRF elemental distribution maps. Depending on which aspects of the SLs are primarily considered (such as similar geochemistry, similar layering, SL occurrences abundant at three different depth intervals), the 17 CT3 SLs can be assigned to three or up to 13 individual impact events. Uncertainty about the actual number of impact events represented remains, however, due to the complex folding deformation observed throughout the drill core. [ABSTRACT FROM AUTHOR]

Rift sediments are important archives for the evolution of the East African Rift System. We present a source-to-sink study of the Nkondo-Kaiso area in the northern Albertine Rift from a ∼200 m thick late Miocene to early Pleistocene sediment succession. The multi-proxy provenance analysis includes framework petrography, heavy mineral studies and single grain studies of garnet and rutile. Mineral textures and provenance signatures indicate two major stages. Sediment of Stage 1 (late Miocene - late Pliocene; ∼6.5–2.6 Ma) is less mature with quartz contents of 58–81%, K-feldspar of 9–15%, plagioclase of 4–15%, and rock fragments of 1–9%. Heavy mineral spectra are dominated by epidote and amphibole with minor abundances of zircon, sillimanite and garnet. Garnet is almandine-rich and can be grouped according to grossular contents (<10% and >10%). Rutile exhibits a wide range of Nb and Cr concentrations, most of them typical for a metapelitic origin. Zr-in-rutile formation temperatures range between ∼570 and 940 °C. Garnet and rutile geochemistry mainly correspond to amphibolite-to granulite-facies igneous and metasedimentary rocks, which exist in the Mesoarchean Karuma Group and the Neoarchean granitoid gneiss of the North Uganda Terrane. Both are part of the adjacent eastern rift flank of the Albertine Rift. A slight change of the heavy mineral composition at ∼4.5 Ma can be correlated with the onset of the synrift stage ∼0.5–1.0 Ma later than in the southern Albertine Rift. Sediment of Stage 2 (early Pleistocene ∼2.6–1.0 Ma) shows a higher quartz content of 82–93%, and lower contents of K-feldspar of 5–11%, plagioclase of 1–7%, and rock fragments of 1–2%. Stable heavy minerals (ZTR index: 19–63) and epidote dominate with minor amphibole and garnet. Rutile and garnet chemical compositions remain largely unchanged to Stage 1 pointing to the same primary source. Obviously, Pleistocene sediment was mainly recycled from sedimentary rocks of the Neoproterozoic Bunyoro Group, which originate from identical Archean rock assemblages. Ongoing river incision reactivated the primary Archean source in the upper part of Stage 2. In conclusion, Miocene to Pleistocene sediment of the Nkondo-Kaiso region is supplied from local sources of the rift flank and the adjacent Ugandan plateau. Tectonic pulses at ∼4.5 Ma, ∼2.6 Ma, and ∼1.5 Ma led to river incision and moderate expansion of drainage basins towards the east. These pulses are roughly coincident with other parts of the EARS but also show regional time lag and delayed response of the source-to-sink system. [ABSTRACT FROM AUTHOR]

Three outcrops of the Silurian Sharawra Formation at its type locality in Old Qusaiba Village in Central Saudi Arabia were studied for lithofacies distribution, petrographical, and geochemical characteristics. The outcrops were logged and nine different lithofacies were identified in the field. Petrographic analysis shows the Sharawra Formation to be mainly subarkosic associated with increasing mica content near to its contact with the underlying Qusaiba Shale Formation. Major and trace element geochemistry indicates that the sediments of the formation were deposited in a passive continental margin. The source area discriminating plots reveal acidic or felsic rocks such as granites as the probable provenance of the Sharawra sediments. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) indicate a moderate degree of weathering in the source area of these Silurian sediments. This study provides a baseline for future characterization studies of Paleozoic siliciclastic formations in Saudi Arabia and neighbouring countries. [ABSTRACT FROM AUTHOR]

The Late Barremian-Early Aptian of the Jebel Serdj was studied in detail regarding to lithology, microfacies, mineralogy and geochemistry in order to reconstruct the paleoenvironmental change of the Pre-Selli Event. The studied section is about 37 m-thick and it is consisting of limestone and marlstone interbeds spanning the latest Barremian-Early Aptian. During the latest Barremian, kaolinite/illite intensity ratios show high values possibly indicating a warming trend followed then by decreasing values that may indicate a cooling trend. During the Early Aptian, this cooling trend is reverted into humid/warming trend during the Selli event. During the Late Barremian, the low abundance of Ti/Al and K/Al ratios and the enrichment of some elements such as Ba, Cu and Ni suggests that the studied section is characterized by a high productivity, and a minimal detrital inputs. During the Late Barremian, the δ 13 C increases sporadically and is associated with enrichments in some redox-sensitive indices U/Th, V/V + Ni, Ni/Co and V/Cr indicating the presence of intermittent dysoxic to anoxic conditions. [ABSTRACT FROM AUTHOR]

The Kerrouchen Basin is an understudied rift basin in the Middle Atlas of Morocco, where over 600 m of Triassic stratigraphy is well exposed. It was partially inverted during the Atlasic orogeny whilst preserving the original basin geometry. Within the Kerrouchen Basin, two distinct fluvial systems are present. The first, recorded by the K3 Formation, is a braided-meandering fluvial system showing vertical and lateral amalgamation. The K3 is an axial fluvial system that shows a predominant drainage direction towards the north-north-east, parallel to the rift zone axis, ultimately draining towards the Tethys Ocean. The K4 Formation records a secondary, Tributary Fluvial System (TFS), with facies spanning a range of alluvial-fluvial processes. Paleoflows predominantly record drainage to the SSW, transverse to the basin axis. Heavy mineral and petrographic analysis of the two fluvial systems indicates two distinct sedimentary provenances for the depositional system. The K3 system records a higher proportion of sediment sourced from igneous rocks. In contrast, the K4 system records a local provenance signal derived from adjacent low-medium grade metamorphic terranes exposed to the east. Comparison of the provenance and stratigraphic trends within the Kerrouchen Basin with work undertaken in the Central and Western High Atlas suggests a shared source region for the through going axial fluvial systems recorded in the High Atlas and Kerrouchen basins. Our study provides evidence for a linked fluvial system spanning the High and Middle Atlas rifts during the Triassic, indicating that a regional fluvial system was present within Central Pangea from Middle-Late Triassic times. Identifying regional and local drainage networks within the Triassic rift basins has key implications for paleogeographic reconstructions and future exploration efforts for hydrocarbons and CCS sites within Morocco. • Multiple source-to-sink systems within the Triassic of the Middle Atlas rift. • Provenance analysis indicates local and regional drainage systems. • Distinct fluvial styles observed between local and regional systems. [ABSTRACT FROM AUTHOR]

Phosphorites are an essential natural resource for producing phosphoric acid, phosphate fertilizers, and phosphate-based products. Detailed characterization and an appropriate assortment of phosphate resources are necessary to identify rocks that are chemically suitable for the phosphate industry. In the present study, we investigated the chemical composition and petrographic characteristics of phosphorites from three phosphate fields located in the same syncline, Zin Negev, Israel. At each site, the succession of pristine and reworked phosphorite layers along 10 m of the section was observed. Based on the chemical and petrographic analysis of phosphorites, it can be concluded that even though all the studied phosphorites were deposited in the same basin under suboxic conditions, the sedimentary settings are varied at each site. These variations resulted in differences in sedimentary structures and chemical composition, including the concentrations of major and trace elements and the abundance of the organic matter fractions. In all studied samples, a decrease in total organic carbon and redox-sensitive trace elements was observed upon the transition from a pristine to a reworked phosphorite phase, while the relative abundance of organic matter fractions remained nearly constant. The results of the present study indicate that, in addition to high-quality phosphorites at anticlinal heights, phosphorites with low organic matter contents in synclines can also be suitable for industrial applications. However, in phosphates, where humic substances represent the main fraction of OM that is located inside carbonate-fluorapatite grains, difficulties in the separation of OM from carbonate-fluorapatite grains during the production process cannot be excluded. • Petrographic and chemical analysis of adjacent phosphorite sections indicates differences in their sedimentary environments. • Humic substances in Negev phosphorites are preserved due to the entrapment inside apatite grains at early diagenesis stage. • Syncline phosphorites with low content of organic matter may be suitable for industrial use. [ABSTRACT FROM AUTHOR]

The Bocaranga pluton, in the northern domain of the Central African Orogenic Belt (CAOB) in the Central African Republic (CAR), is located in the Adamawa-Yadé domain, near the Mbéré Shear Zone (MBSZ). This study provides new results of the satellite image processing, the detailed structural and petrographic studies of Bocaranga pluton which helps to understand the emplacement mechanism of this pluton. Image processing of the satellite data and field showed the occurrence and spatial distribution of (1) amphibole-pyroxenites, (2) garnet-biotite rich amphibolite, (3) migmatite, (4) hornblende-biotite and hornblende-garnet gneiss, (5) hornblende-biotite granite (HBG), (6) two micas granite (TMG), (7) fine-grained biotite granite (FBG), and (8) coarse-grained biotite granite (CBG) rock types. The mapping of regional lineaments was carried out by automatic and manual lineament extraction methods. NE-SW direction corresponds to the direction of S2 and S3 foliations, faults, mineral lineation, quartz vein, dyke (aplitic granitic or pegmatitic). NW-SE direction also corresponds to the direction of S1 foliation, F1 folds, faults, quartz veins, dykes (aplitic granitic or pegmatitic). In the absence of absolute geochronological data in study area, it has been possible to propose a polyphase structural evolution, deduced from the relative chronology of the Bocaranga granitoid. Three phases of deformation can be defined in this study. D1 phase is represented by early NW-SE trending foliation (S1) that has been progressively rotated parallel to S2 overprinting foliation occurring in gneiss, amphibolites and hornblende-biotite granite (HBG) intrusion as well. D2 phase of ductile sinistral sense from NE-SW to ENE-WSW is responsible for an emplacement of Bocaranga granitic pluton. The scarcity of structure orientation in the TMG and FBG (except the contact zones), would imply that these granites would have been crystallized in the absence of any stress. D3 is a phase of brittle deformation with three main directions corresponding to the main direction of the shear zones in the Northern domain of the CAR Pan-African fold belt. The mylonitic deformation observed in study area illustrates the intensity of the deformation. The dominance of ellipsoidal structures observed in Bocaranga area suggests that the shear mechanism is the main controlling structure of Bocaranga granite emplacement, which can be correlated with the emplacement of Tamkoro-Bossangoa granitoid in CAR and the Adamawa-Yadé domain in Cameroon, Chad and NE Brazil. These results imply a syntectonic emplacement of Bocaranga pluton during sinistral simple shear regime related to deformation along the Central Cameroon Shear Zone (CCSZ). [Display omitted] • New litho-structural map of Bocaranga using remote sensing. • New petrographic and structural data in Adamawa-Yadé domain in Central African Republic (CAR). • The syntectonic emplacement of the Bocaranga pluton in the sinistral shear zone is related to deformations along the Central Cameroon Shear Zone (CCSZ) also called Mbéré Shear Zone (MBSZ) in Central African Republic (CAR). [ABSTRACT FROM AUTHOR]

The Jilh Formation (late Anisian to Carnian) was deposited on the southwestern margin of the Neotethys Ocean recording the flooding of a broad shallow marine platform, and is characterized by restricted clastic-prone mudrocks and sabkha anhydrite with interbedded shallow marine dolomitized carbonates. Within the Lower Jilh Formation, deposits encompass tidal flat to low-energy inner ramp thrombolytic microbial deposits with local anhydrite nodules and fenestrae structures interbedded with ft-scale intraclast-rich floatstones with desiccation surfaces. Within the interbedded mudrocks, land-derived miospores (including common Lunatisporites spp. and other taeniate bisaccate pollen) and clastic material are common. During the Carnian, the higher sea level resulted in a change to tidal flat bioturbated and microbially induced mudstones, along with inner ramp subtidal peloidal sand banks and skeletal wackestones with benthic foraminifera within the Upper Jilh Formation. Terrestrially derived miospores are still common (assemblage including common Camerosporites secatus , Conipollenites arabicus , Duplicisporites spp., Samaropollenites speciosus), but an increasing marine influence is also noted during the Carnian from the presence of marine palynomorphs such as acritarchs and prasinophytes (including acanthomorphic acritarchs, Veryhachium spp. and Dictyotidium spp.). The backstepping of the platform is marked by the progressive flooding of the tidal flats and the deposition of open marine facies culminating in a regional 2nd order maximum flooding surface. Petrographic and geochemical analyses show the development of fabric-replacive planar-s to planar-e dolomite fabrics associated with negative δ18O values and positive δ13C values, suggesting precipitation of the dolomite on top of 3rd and 2nd order sequences from possible transgressive reflux syn or post deposition of the Jilh Formation. Zoned dolomite rhombs lining macropores might be related to burial diagenesis and pore-filling anhydrite and calcite are locally common. The local presence of native sulfur replacing primary anhydrite nodules, along with the minor calcitization of the anhydrite also suggest the onset of thermochemical sulfate reduction during the burial history at possibly high temperature. • The Jilh Formation in Saudi Arabia encompasses four 3rd order sequences. • Palynology data confirm a late Anisian to Carnian age. • Depositional environments range from intertidal to moderate-energy inner ramp. • Isotopes and petrography suggest dolomitization by transgressive reflux. [ABSTRACT FROM AUTHOR]

This study was undertaken to determine the depositional environment, provenance and tectonic setting for the Turonian Amasiri Sandstone, southern Benue Trough, Nigeria, using lithofacies analysis and re-appraisal of petrography of the sandstones. Local stratigraphy and field relationships show a thick succession of shales alternating with elongate/parallel sandstone ridges extending eastwards from Akpoha to Amasiri through Itigidi and Ugep to Apiapum areas. Lithofacies analysis reveals 9 lithofacies suggestive of storm (mass flow) and tidal shelf processes. These include dark grey to black laminated shale/silty mudstones, bioturbated mudstones, coquinoid limestones, very fine-grained bioturbated sandstones with shell hash/debris in places and limestone rip-up clasts, massive and chaotic sandy conglomerate with rip – up clasts, fine to medium-grained, parallel laminated sandstone, hummocky cross-stratified, massive, medium to coarse-grained sandstones, medium to very coarse-grained, planar cross-bedded sandstone, with clay-draped foresets and Ophiomorpha burrows, and coarse-grained trough cross-bedded sandstone. Petrofacies analysis identifies the sandstones as feldspathic and arkosic arenites. Ternary plot of framework mineralogy indicates derivation from an uplifted continental block related to the nearby Oban Massif and Cameroon Basement Complex. [ABSTRACT FROM AUTHOR]

The Temple of Kom Ombo is a huge ancient Egyptian temple in Upper Egypt. It was built by Ptolemy VI Philometor (180-145 BC) and added to by subsequent Ptolemys. The structure of the temple is built of local sandstone attributed to the Quseir Formation of “Nubian Sandstone” group at Gebel el-Silsila. Sandstone samples from Kom Ombo temple were taken to verify the source rock of the quarried material. Optical Polarizing Microscope (OPM) and Scanning Electron Microscope (SEM) were used to determine the microstructure and physical properties of the sandstone. X-Ray diffraction (XRD) was carried out for the Sandstone samples to identify its mineralogical composition. The sandstone samples were treated with six polymeric products to determine changes in their physical and mechanical properties after penetration, consolidation of polymers within them. This sandstone is composed mainly of three quartz arenite microfacies (feldspathic, sublithic and calcareous) that are interpreted to have been deposited in fluvial to fluvial-marine environment. Silane polymers is showing a good penetration and filling pores between grains and recommended for treatment and conservation of the sandstone. Acrylic polymer shows random penetration of polymer and formation of a film of polymer on the surface of sandstone. Silo11 gave the best result in consolidation of sandstone samples then primal AC33. Wacker BS29 gave the best result in isolating process of sandstone samples, then wacker BS 290. [ABSTRACT FROM AUTHOR]

Penjween ophiolite is one of the ophiolitic complexes of northeastern Iraq. The serpentinites within the Penjween Ophiolite hosts many pods of hornblendite and amphibolite, and dikes of diorite among many other igneous bodies. These pods have very sharp contacts with the surrounding mantle serpentinized harzburgites. The hornblendites and amphibolites are usually intimately intergrown together as extremely hard, dark green to black colored, fine-to medium-grained pods with ∼2 x ∼2 x ∼(0.5–1) m dimensions. This study presents petrography, mineral chemistry, whole-rock major and trace element geochemistry, and electron probe microanalyses (EPMA) for the major minerals in the studied rocks. The hornblendite is composed entirely of amphiboles (>99% vol.), meanwhile the amphibolite consists of comparable amounts of amphibole and plagioclase which occasionally occurs as layered rocks with banded texture. The diorite dikes are white in color and consist dominantly of coarse-grained plagioclase and less amphiboles. The amphiboles of these rocks belong to pargasite (Mg# 0.69–0.77) ─ edenite (Mg# 0.74–0.79) endmembers where pargasite is by far the predominant mineral; meanwhile the plagioclase is albite (Ab 93.4 An 6.4 Or 0.2). The amphiboles are replacement products of pyroxenes indicated from the relict pyroxene within their crystals. The amphiboles are abnormally rich in various dust-like inclusions of transparent minerals like REE-rich epidote, rutile, zircon, apatite, titanite, and ore minerals like ilmenite, and pyrrhotite, oriented along the crystallographic axes and form distinct zones in the core of amphibole crystals. The geochemical characteristics of the studied hornblendite (MgO = 13.07%, Ni = 260 ppm, Mg# = 66.57) as well as the high Sc (33 ppm) and V (254 ppm) concentrations are collectively consistent with a mantle-derived, igneous origin. The primitive-mantle normalized trace elements spidergram showed enrichment (hump) in Ba, Th, U, La, Ce, Pb, and Sr, and depletion (trough) in Nb, Ta, K, and Ti. The chondrite-normalized REE diagram showed enrichment of LREE relative to HREE, indicated from the smooth and steady decrease in the negative slope from LREE towards HREE with a negligible Eu-anomaly. Various tectonic discriminating diagrams showed that the studied hornblendite, amphibolite pods and diorite dikes are of igneous fore-arc origin, formed from calc-alkaline and/or tholeiitic magma within an active continental margin setting. The 40Ar/39Ar laser age of hornblendite is late Paleocene (Thanetian) (57.8 ± 5.1 Ma) which might represent an event during the obduction between the oceanic fore-arc Island and the Arabian Plate during the Late Cretaceous/Paleocene period. [Display omitted] • The studied rocks are hornblendite, amphibolite and diorite rocks. • The hornblendite is monomineralic and consists of amphiboles. • The amphibolite and diorite consist of comparable amounts of amphibole and plagioclase. • These rocks are calc-alkaline island arc basalts, •The 40Ar/39Ar laser age of the hornblendite is late Paleocene (Thanetian) (57.8 ± 5.1 Ma). [ABSTRACT FROM AUTHOR]

Sandstone petrography and geochemistry (major, trace and rare earth elements) of the Aptian–Albian siliciclastic Massylian flysch from the Chouamat Nappe (central Rif Morocco) are used to highlight the chemical weathering conditions in the source area and to infer their provenance. Petrographic studies show that the studied samples are mostly quartzarenite, sublitharenite and subarkose generally composed of quartz (up to 99%), K-feldspar (less than 5%) and scarce fragments of sedimentary rocks. The samples plot in the continental block provenance field of the QtFLt diagram. Thus, the compositional maturity of analyzed sandstones is typical of cratonic environments. The sandstone samples shows high SiO 2 content (up to 96%) and strong depletion in mobile components such as Na 2 O, CaO as well as in ferromagnesian minerals, which are mainly related to intense chemical weathering processes in the source area, as confirmed by high Chemical Index of Alteration values (mean = 79.8). Recycling is shown by the Th/Sc vs. Zr/Sc plot, where the studied sandstones fall along a trend involving zircon addition and thus sediment recycling. Several geochemical ratios, such as La/Sc, Th/Sc, Th/Co and Th/Cr, of the studied samples are similar to those of Post-Archean Australian Shales and of the Upper Continental Crust, and suggest a provenance from source area(s) mainly composed of plutonic and felsic metasedimentary and sedimentary rocks, which were most probably the basement rocks of the adjacent African plate. These source rocks are related to a large cratonic source region of Eburnean and Pan-African belts, Precambrian (?) and/or Variscan basements of the southeastern margin of the African plate. [ABSTRACT FROM AUTHOR]

The ironstone lenses of Ga'ara area are enclosed within the uppermost part of the clastic succession of Permocarboniferous Ga'ara Formation. This succession is composed mainly of sandstones (sometimes with pebbles), siltstones, and kaolinitic claystones. The ironstones are classified according to their lithology and texture into two types: massive and pisolitic-oolitic ironstones. The later is restricted to the southern rim of Ga'ara Depression. The enclosure of ironstone lenses within the fining upward cycle, predominance of colloform and pisolitic oolitic textures and the low Cu, Pb, Zn, and Mn contents are good evidences for the shallow sedimentary environment of deposition. There is no convincing evidence to suggest any serious role of lateritization process in the formation of the studied ironstones. The most probable source rocks that consist of plutonic metamorphic complexes of Arabian Shield were subjected to deep chemical weathering and erosion under humid and tropical climate. These products dominated by amorphous iron oxyhydroxides, kaolinite, and quartz were transported by rivers to be deposited in fluviatile and lacustrine environments in Ga'ara area. Iron was carried as colloids and/or associated with clay fractions. The massive clayey ironstone and pisolitic oolitic ironstone were formed by the deposition of iron oxyhydroxide-bearing clays within small lakes associated with flood plain river overbanks; while the massive sandy ironstone was formed by the deposition of water laid detrital quartz grains cemented by goethite and hematite. [ABSTRACT FROM AUTHOR]

The Bou Skour copper deposit is located in the western part of the Saghro massif (Eastern Anti-Atlas), about 50 km East of the city of Ouarzazate. It is subdivided into several areas that are, from North to South: "Panthère", "Chaigne", "Anne Marie", "Chapeau de fer" and "Patte d'Oie". The latter is economically the most important and is the object of this study. The "Patte d'Oie" district consists mainly of extrusive and intrusive igneous rocks. The extrusive rocks are represented by andesites spatially associated with pyroclastic terms (ignimbrites and pyroclastic breccias). This volcanic unit is intruded by a pink granite pluton and a I-type granodiorite with equigranular texture (Bou Skour granodiorite) showing to the border a microgranular facies (microgranodiorite). All these magmatic formations are intersected by rhyolitic dykes (NNE-SSW) and doleritic dykes (WNW-ESE to NW-SE). The granodiorite and andesite have undergone a polyphase hydrothermal alteration: (i) potassic alteration, (ii) phyllitic alteration, (iii) silicification, (iv) argillic alteration and (v) propylitic alteration. The analysis of geochemical data of granodiorite, granite, andesite and dolerite confirmed: (i) their petrographic natures, (ii) the medium-K calc-alkaline affiliation of andesite and granodiorite, which would have been set up into an active geotectonic environment, probably of island arc or collision, during the Pan-African orogeny, (iii) The high-K calc-alkaline character of granite indicating a post-collision development during the Pan-African orogeny and (iv) The alkaline affinity of the dolerite which is linked to an extensive post-orogenic setting (post-Pan-African). The copper mineralization of "Patte d'Oie" area is hosted, exclusively, in the andesitic and granodioritic facies. It is represented, essentially, by chalcopyrite and bornite minerals and is, probably, related to a porphyry system (disseminated and stockwork mineralization) remobilized late, in Hercynian structures (vein mineralization). [ABSTRACT FROM AUTHOR]