Journal of African Earth Sciences最新文献

{"title":"Hydrological change from space geodetic data and correlation with climate indices in Sudan","authors":"Walyeldeen Godah ,&nbsp;Samuel Milki Yadeta ,&nbsp;Alexander Braun","doi":"10.1016/j.jafrearsci.2025.105608","DOIUrl":"10.1016/j.jafrearsci.2025.105608","url":null,"abstract":"<div><div>Terrestrial hydrological data in Sudan are heterogeneous with a limited quantity and quality that hinders reliable monitoring of natural or anthropogenic hydrological change. Thus, alternative data sources such as satellite observations are essential for monitoring hydrological change in Sudan. Moreover, like many other regions around the world, hydrological change in Sudan is strongly related to climate change presenting an opportunity to analyse the correlation of these processes. The aim of this research is to investigate the usefulness of space geodetic data to monitor hydrological change in Sudan and its relation with climate indices.</div><div>Temporal variations of equivalent water thickness were determined over the area of Sudan using GLDAS dataset and data from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow–On (GRACE–FO) satellite missions. Temporal surface water variations at nine river crossings were obtained from satellite altimetry (Sentinel, Jason-2/3). The correlations between temporal variations of equivalent water thickness and sea surface temperature from both the El Niño–Southern Oscillation and the Indian Ocean Dipole climate indices were investigated. The results indicate good agreement between temporal variations of equivalent water thickness from GRACE/GRACE–FO data and GLDAS dataset. These temporal variations of equivalent water thickness were further correlated with the temporal surface water variations from altimetry data. In addition, there exist clear correlations between hydrology change in Sudan and sea surface temperature from El Niño 1 + 2 and El Niño 3 climate indices. In general, the results revealed the usefulness of space geodetic data for determining hydrological change in Sudan.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"227 ","pages":"Article 105608"},"PeriodicalIF":2.2,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143610151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Northwest africa 16273: 4Vesta's mantle sampled during the giant impact","authors":"Ratiba Kared ,&nbsp;Bertrand N. Moine ,&nbsp;Jean-Luc Devidal ,&nbsp;Abdelmadjid Seddiki","doi":"10.1016/j.jafrearsci.2025.105604","DOIUrl":"10.1016/j.jafrearsci.2025.105604","url":null,"abstract":"<div><div>We report here the results of a comprehensive petrological and geochemical study of Northwest Africa (NWA) 16273. NWA 16273 is classified as a mesosiderite-B2/3 and contains a significant amount of metal and silicates phases. It is composed of pyroxene, olivine, plagioclase, iron-metal + sulfide phases, and minor amounts of phosphate, chromite, phosphide, rutile, ilmenite and quartz. Olivines appear as xenocrysts surrounded by reaction rims composed of pyroxene and chromite. Some pyroxenes occur as xenocrysts and as small grains in the matrix. Pyroxene shows significant variation in composition: Low-Ca pyroxene (Fs_18-36 Wo_3-4; n = 22) and pigeonite Fs_22-26 Wo_12-20 (n = 2). The Fe/Mn ratios of all pyroxenes show a large variation and have molar Fe/Mn rations of 27.6 ± 3.1 (n = 24). Whereas, olivines have molar Fe/Mn ratios of 45.5 ± 4.2 (n = 20). These ratios are compatible with 4Vesta compositions. Plagioclase are bytownites and anorthite (An_87-92 Or_0.2-0.6). Additionally, Olivine displays a bimodal distribution with two populations: olivine-Mg-rich (Fo_72-81 Fa_19-28) and olivine less magnesian (Fo_60-67 Fa_33-40). The combination of an harzburgitic composition and a high metal content in the NWA 16273 suggests a complex origin involving several parent bodies, which may have undergone a collision, melting and ejection to form the mesosiderite. Textural, mineral and geochemical characteristics indicate that a metallic impactor melted an eucritic crust of 4Vesta. The eucritic magma and molten metal were injected into the harzburite mantle prior to ejection. Nickel phosphides oxidized on contact with silicate magma to form secondary phosphates. Olivine underwent a more or less intense peritectic reaction to produce secondary orthoproxenes and chromites. The orthopyroxene xenocrysts are zoned and partially chemically re-equilibrated. These features show that a fraction of 4Vesta mantle was sampled during the giant impact.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"227 ","pages":"Article 105604"},"PeriodicalIF":2.2,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Miocene–Quaternary stratigraphy and sedimentation along EL Daba'a Plateau, Northwestern coast of Egypt","authors":"Hesham M. El-Asmar,&nbsp;Mahmoud Sh. Felfla,&nbsp;Zaki A. Abdel-Fattah,&nbsp;Ehab M. Assal","doi":"10.1016/j.jafrearsci.2025.105603","DOIUrl":"10.1016/j.jafrearsci.2025.105603","url":null,"abstract":"<div><div>The current research investigates the stratigraphy, sedimentation, and neotectonics of the Miocene–Quaternary succession along El Daba'a Plateau, northwestern coast of Egypt. In order to unveil the environments of deposition in connection with paleoclimate and sea-level variations, the stratal architecture, including bed geometries, orientation, and field relationships, is highlighted. The field observations of five sections at El Daba'a Plateau reveal two formations: the lower one is the Marmarica Formation of Middle Miocene age, and the upper one is the Alexandria Formation of Quaternary carbonate aeolianites and inter-aeolianite deposits. The Marmarica Limestone Formation is subdivided into two members: the lower is the Oasis Member, and the upper is the Siwa Escarpment Member. A distinct disconformity separates the two formations, with the recognition of twelve lithofacies units (L1–L12) and thirteen microfacies associations (<em>Mf1</em>–<em>Mf13</em>). The Oasis Member belongs to the inner carbonate ramp siliciclastic-carbonate facies association (<em>Mf1</em>–<em>Mf3</em>), while the Siwa Escarpment Member belongs to the mid-ramp carbonate-dominated facies association (<em>Mf4</em>–<em>Mf6</em>). Seven microfacies (<em>Mf7</em>–<em>Mf13</em>) are tied to the Quaternary carbonate aeolianites and inter-aeolianite deposits. Evidence of Late Pleistocene normal faults, trending WNW-ESE, ENE-WSW, and NNW-SSE, has moulded the coastal geomorphology, with a general vertical uplift of up to 15 m. Results of the current work contribute to understanding the geology of the Mediterranean margin at the NW part of Egypt, which needs further studies.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"227 ","pages":"Article 105603"},"PeriodicalIF":2.2,"publicationDate":"2025-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural controls on the talc mineralization at El Nasr mining company concession, Wadi Allaqi district, South Eastern Desert, Egypt: Insights from remote sensing, field investigation and geological traverses","authors":"Zakaria Hamimi ,&nbsp;Wael Hagag ,&nbsp;Samir Kamh ,&nbsp;Zeinhom El-Alfy","doi":"10.1016/j.jafrearsci.2025.105600","DOIUrl":"10.1016/j.jafrearsci.2025.105600","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The current work is an integrated study utilizing remote sensing and field-structural data to better understanding of the origin, structural framework and tectonic evolution of the talc ore exploited by El Nasr Mining Company at its concession in Wadi Allaqi district, South Eastern Desert, Egypt. Exploring the best sites in the environs of the currently working mine for future working is also one of the important objectives of the study as well. Processing of Landsat- 8, ASTER and Sentinel- 2 images resulted in mapping of a large elongated NW-oriented and NE-dipping zone of talc-bearing highly-sheared metaultramafics and talc carbonate schists enclosing variably-sized masses of amphibolites and surrounded by highly-sheared metavolcanics and metavolcaniclastics which are tectonically intermingled. Such zone is structurally representing a part of (the hanging wall) of a major left-lateral transpressive zone. The present working talc mine is utterly located along a large lense of highly-sheared metaultramafics (trending N30°-40°W and dipping 55°–78° NE) which is extended northwestward to include the ‘‘Nawal Game’’ mine but outside the concession. However, the rest of talc carbonate zone reveals that the origin of talc was related to the alteration or metasomatic processes that are working intensively upon the mafic metavolcanic rocks. Several promising talc sites distributed within the previously mentioned talc zone are documented and checked for further evaluation and preparation of core-sample study (core-sample locations and core-directions are measured) to extend the concession area and mining activities to the approved sites in near future. The remote sensing-based mapping supported by field-structural work indicated that the investigated area (as a whole) represents a tectonic belt oriented NW-SE and dipping steeply to NE and building up of highly sheared and altered ophiolitic mélange rocks intruded in places by metagabbro-diorite and heavily dissected by mafic dykes and quartz veins following the main directions of thrust/shear which are exclusively major NW-SE and minor NE-SW tectonic trends. The study area was practicing three deformation phases where the most important is D&lt;sub&gt;2&lt;/sub&gt; which was producing the NW-trending foliation with NW and SE plunging lineations. During such phase the earlier D1 thrusts were reactivated forming transpressive faults and highly-dipping to subvertical shear zones associated with the alteration/metasomatism of mélange rocks producing talc pockets, lenses and elongated zones of talc-carbonate schists. It is worth mentioning that the talc ore is not recorded along the younger NE- to ENE- tectonic trends (D&lt;sub&gt;3&lt;/sub&gt; deformation) indicating that the talc was predominantly related to D&lt;sub&gt;1&lt;/sub&gt; and D&lt;sub&gt;2&lt;/sub&gt; tectonic events. The structural and tectonic setting of the investigated area can be considered in terms of the tectonic evolution of the greater Wadi Allaqi district (Allaqi suture). Th","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105600"},"PeriodicalIF":2.2,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contribution of geophysics to the stratigraphic, structural, and neotectonic study of the Taroudant region and adjacent areas (Souss basin, southwestern Morocco)","authors":"Sliman Hitouri ,&nbsp;Mohamed Hafid ,&nbsp;EL Arbi Toto ,&nbsp;Ibtissam Rezouki ,&nbsp;Zakaria Srhir","doi":"10.1016/j.jafrearsci.2025.105591","DOIUrl":"10.1016/j.jafrearsci.2025.105591","url":null,"abstract":"<div><div>The Souss Plain, including the urban area of Taroudant and its surrounding region, is primarily composed of Plio-Quaternary deposits, within which Cretaceous Hills emerge as outcrop. These Hills suggest significant neotectonic activity in the region, located at the piedmont of the western High Atlas. To investigate this neotectonic activity, a combination of geophysical, geological fieldwork, and borehole data was employed to analyze and characterize fault systems and geological structures affecting the recent formations.</div><div>This analysis identified three major neotectonic faults (F1, F2, and F3) in the study area, oriented NE-SW and E-W, with dips towards the southeast or South. These major faults are associated with several minor faults (EBF, HMF, TSF, and TSF-1) that exhibit similar orientations and dips, significantly affecting the Plio-Quaternary deposits. Specifically, Fault F1 crosses north of Taroudant, extending southwestward to mark the southeastern boundary of the Aricha Hill. Fault F2 cuts through Taroudant's urban centre, extending southeastward and passing south of Elbouida Hill. Fault F3 extends south of Sidi Bourja Hill and continues westward to the south of Elbouida Hill, where it intersects with F2.</div><div>Further analysis and correlation of lithostratigraphic sections and stratigraphic logs from hydrogeological wells reveal a progressive thickening of Quaternary deposits from north to south. This thickening is interrupted by Fault F2, whose syn-sedimentary activity likely the thinning of the sedimentary sequence near the hinge of the faulted anticline, created by fault movement, and the thickening.in front of the fault.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"227 ","pages":"Article 105591"},"PeriodicalIF":2.2,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The age and source of Cambrian post-orogenic magmatism in the Kuboos-Bremen Igneous Province (Southern Namibia)","authors":"R.F. Zech ,&nbsp;C.T. Onken ,&nbsp;G. Sartori ,&nbsp;S.J. Simon ,&nbsp;A. Shipandeni ,&nbsp;A. Galli ,&nbsp;R.A. Spikings ,&nbsp;M.W. Schmidt","doi":"10.1016/j.jafrearsci.2025.105592","DOIUrl":"10.1016/j.jafrearsci.2025.105592","url":null,"abstract":"<div><div>Post-orogenic complexes in Central and Southern Namibia record the amalgamation of Gondwana along the Pan-African Gariep and Damara Belts. Five complexes of the Kuboos-Bremen Igneous Province in Southern Namibia (Grootpenseiland-Marinkasquellen, Marinkas Carbonatite, Kanabeam, Young Bremen, Garub suite) have been dated with zircon U-Pb and biotite Ar-Ar, while Hf isotopes on zircon were used to characterize the source of the magmatic province. Within errors, nine granites and syenites of the Grootpenseiland-Marinkasquellen, Kanabeam and Young Bremen Complex(es) are contemporary and emplaced between 493 and 509 Ma (with typical errors of ±8 Ma). The Marinkas Carbonatite Complex yields slightly higher ages (508–536, ±10 Ma). Two lamprophyric dykes from the Garub Suite that consists mainly of carbonatite breccia pipes yield an age of 525 ± 3 Ma, contemporaneous with the Marinkas Carbonatite Complex. Negative εHf(t) indicate post-orogenic magmatism resulting from lithospheric thinning and heating of metasomatized mantle. Only one sample, a Si-undersaturated nepheline-sodalite syenite from the Kanabeam complex, has positive, close-to unmetasomatized mantle εHf(t) values, indicating a heterogeneously metasomatized (lithospheric) mantle.</div><div>Monzonite and monzodiorite samples from the Otjisazu Carbonatite Complex in Central Namibia yield U-Pb zircon ages of 521 and 550 Ma (±10 Ma), respectively, sharply contrasting a previous U-Pb titanite age of 840 Ma. The negative zircon εHf(t) in a system that evolves to carbonatites indicates crustal contamination of the mantle source but negligible crustal assimilation during magma ascent.</div><div>In addition, the southern Namibian Haruchas Stock and the Old Bremen Complex were dated. Notably, the heavily Si-undersaturated Haruchas Stock yielded an age of 896 ± 18 Ma, and is hence not akin to the Si-undersaturated rocks of the Kuboos-Bremen Suite but the northernmost extension of the Richtersveld Suite. Our U-Pb ages for the Old Bremen Complex (880–903 ± 18 Ma) confirm previous results. The positive εHf(t) of +1.3 - +7.5 of samples from the Haruchas Stock and Old Bremen Complex indicate that their source had a lesser involvement of crustal components than the Cambrian magmatism, consistent with mantle-derived alkaline magmatism within an extensional setting.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105592"},"PeriodicalIF":2.2,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pore pressure study in the berkine basin, south-east Algeria; characterisation of overpressure intervals and implications for hydrocarbon accumulation and exploration","authors":"Ali Saadaoui ,&nbsp;Riadh Ahmadi ,&nbsp;Chaouki Khalfi ,&nbsp;Riheb Hadji ,&nbsp;Mohamed Salah Laaouar","doi":"10.1016/j.jafrearsci.2025.105587","DOIUrl":"10.1016/j.jafrearsci.2025.105587","url":null,"abstract":"<div><div>In this study, several independent but complementary methods were used to investigate overpressure intervals in the Berkine basin, SE Algeria. The methods used, namely the Eaton sonic method, the drilling D-exponent, and the mud weight, were then correlated and validated with fracture and pore pressure surveys. Pore pressure studies were conducted in 89 wells across the main and the satellite structures of the Berkine basin oilfields. Pore pressure profiles revealed an interval characterised by remarkably high overpressures, situated above the target reservoirs. A north-south stratigraphic and seismic correlation showed that this overpressured interval is hosted in the Upper Triassic to Lower Jurassic succession, which consists mainly of salt, anhydrite, shale, and dolomite thin beds. The overpressure amplitude reached its maximum at the centre of the Berkine basin, exceeding 2.0 equivalent density, and diminishes southwards as the thickness of the host sequence progressively decreases, reaching values of below 1.7 equivalent density.</div><div>The overpressured interval, which has been observed throughout the Berkine basin, appears to have contributed to the efficient sealing of underlying reservoir units, including the TAGI and the Paleozoic reservoirs. In light of the observed pore pressure distribution, it would be a worthwhile pursuit to investigate the potential for hydrocarbon exploration in the northern region of the Berkine basin, where higher overpressure is being observed. This result will provide added value to all sedimentary basins having overpressure intervals. Conversely, the presence of the overpressured interval poses a challenge to drilling operations, and the results of this study will facilitate the accurate setting of casing point depths and contribute to improving wellbore stability.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105587"},"PeriodicalIF":2.2,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The legacy of the East African rift system in understanding continental rifts worldwide from geophysical studies (with emphasis on gravity and magnetic studies)","authors":"Luelseged Emishaw ,&nbsp;Andrew Katumwehe ,&nbsp;Khumo Leseane ,&nbsp;Zelalem Demissie ,&nbsp;Kevin Mickus ,&nbsp;Mohamed Abdelsalam","doi":"10.1016/j.jafrearsci.2025.105589","DOIUrl":"10.1016/j.jafrearsci.2025.105589","url":null,"abstract":"<div><div>The diverse geology of the African continent has provided the geoscientific community with an unparallel opportunity to examine and understand complex endogenic and exogenic processes that have shaped and are still shaping our Planet Earth. An exemplary illustration of this is the East African Rift System (EARS), which traverses the African continent from its northeastern part in the Afar Depression to its southern part in the Okavango Rift Zone. In this review, we aim to provide an overview of the notable gravity and magnetic studies that have contributed to our understanding of continental rift evolution. Our primary focus is on gravity and magnetic contributions to understanding the rifting processes from their enigmatic nucleation as incipient rift systems to their subsequent progression from continental rifting to seafloor spreading, an aspect that garnered more attention and investigation. We highlight the legacy of gravity and magnetic studies in understanding the evolution of continental rifts from eight studies starting from the most evolved segment of the EARS in the Afar Depression to the most incipient segment of the rift in the Okavango Rift Zone. These include: (1) The transitioning from continental rifting to seafloor spreading in the Afar Depression (The Tendaho graben). (2) Nucleation of a future divergent plate boundary within an overlapping propagating embryonic spreading center (The Dobi graben). (3) Transfer of extension from rift border faults to rift floor through magma-assisted rifting (The Main Ethiopian Rift). (4) The evolution of broadly rifted zones though upwelling of mantle flow resulting in an unstable dynamic topography and subsequent gravitational collapse (The Southern Main Ethiopian Rift). (5) Three-dimensional (3D) crustal density stratification and superimposed rifting events (The Turkana rifted zone). (6) The rifting of cratons that is facilitated by inherited zones of weakness presented by orogenic belts (The Eyasi basin). (7) The role of preexisting lithospheric structures in controlling continental rift evolution (The Albertine – Rhino graben). (8) The role of fluid concentration through lithospheric zones of weakness in continental rift initiation (The Okavango Rift Zone).</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105589"},"PeriodicalIF":2.2,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Off-rift volcanism during continental rifting: Observations and models with a focus on the Main Ethiopian Rift, East Africa","authors":"Giacomo Corti ,&nbsp;Daniele Maestrelli ,&nbsp;Marco Bonini ,&nbsp;Federico Sani","doi":"10.1016/j.jafrearsci.2025.105590","DOIUrl":"10.1016/j.jafrearsci.2025.105590","url":null,"abstract":"<div><div>The occurrence of volcanic activity outside a deforming continental rift valley (off-rift volcanism) is a typical feature of rift systems and different hypothesis have been invoked to explain this setting. In this paper, we first summarize observations from off-rift volcanoes in the Main Ethiopian Rift (East Africa) and then we review models -from early conceptual models to modern numerical and analogue experiments-proposed to explain this process. Overall, all these models suggest that off-rift volcanism may be attributed to two main end-member processes: (1) magma migration and (2) off-rift magma production. Magma migration involves extension-parallel lateral transfer of magma from below the rift depression to the rift margins; this process can explain volcanoes formed in the footwall of major boundary faults, in the plateaus close to the rift depression (the so-called flank volcanoes). Off-rift magma generation suggests instead that magma is produced away from the rift depression and is transferred to the surface via steep tectonic structures above the area of production. In both processes, pre-existing structures, inherited from previous tectonic events, are fundamental for controlling (shallow) magma transfer and emplacement, and the final characteristics of off-rift volcanoes.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105590"},"PeriodicalIF":2.2,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143563287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Control of sedimentary and diagenetic processes on the reservoir heterogeneity: A case study of the cretaceous carbonate reservoir in an onshore oilfield, Abu Dhabi","authors":"Yuting Peng ,&nbsp;Yingxiao Fu ,&nbsp;Hangyu Liu ,&nbsp;Kaibo Shi ,&nbsp;Bo Liu ,&nbsp;Rubing Han ,&nbsp;Xili Deng","doi":"10.1016/j.jafrearsci.2025.105575","DOIUrl":"10.1016/j.jafrearsci.2025.105575","url":null,"abstract":"<div><div>To address the issue of pronounced heterogeneity in carbonate reservoirs, this study utilizes core and well log data to identify the microfacies types of the carbonate rocks in XY oilfield, while the reservoir characteristics and heterogeneity genesis were analyzed. The microfacies types and their combinations suggest depositional environments ranging from restricted to open platforms, with a shoaling-upward evolutionary sequence from middle ramp to inner ramp, shoal, and lagoon. These microfacies dictate the reservoir quality: MF3 and MF4 are characterized by ooid grainstone reservoirs where intergranular pores predominate; MF5, MF6, and MF7 feature <em>Lithocodium-Bacinella</em> limestone with reservoir spaces encompassing algal framework pores, intragranular dissolved pores, mold pores, and intergranular dissolved pores. The fluctuating relative sea level resulted in an orderly vertical superposition of the various sedimentary facies belts, with variations in microfacies and diagenetic activities both between different belts and within the same belt being the fundamental causes of reservoir heterogeneity. Meteoric water significantly contributes to pores through selective dissolution of aragonitic components such as <em>Bacinella irregularis</em>, while multi-stage calcite cement during diagenetic evolution markedly damaged the petrophysical properties. Based on these findings, diagenetic facies are categorized, and a genetic classification of reservoir types is established; conventional well logs indicate that GR, RHOB, and NPHI are more sensitive parameters for identifying reservoir types, leading to the development of a logging identification chart for reservoir types. The formation and evolution of the high-permeability layers are influenced by both sedimentation and diagenesis, with the original high-energy shoal environment serving as the foundation; during diagenetic evolution, dissolution increases porosity, and early hydrocarbon charging prevents cementation, thus preserving the pores. The high-permeability layers exhibit lateral stability, predominantly high-energy shoal facies, with occasional laterally discontinuous layers attributed to <em>Bacinella</em> beach facies.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"226 ","pages":"Article 105575"},"PeriodicalIF":2.2,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}