Journal of African Earth Sciences最新文献

{"title":"Palaeoproterozoic Kate granitoid suite provides evidence for slab break-off during the assembly of the Tanzania Craton and Bangweulu Block","authors":"Xingyuan Wu ,&nbsp;Xiaoyang Liu ,&nbsp;Kai Sun ,&nbsp;Hongwei Sun ,&nbsp;Kangkang Xu ,&nbsp;Penghui Gong ,&nbsp;Shengfei He ,&nbsp;Zuomin Zhou ,&nbsp;Godfery Machumu","doi":"10.1016/j.jafrearsci.2024.105448","DOIUrl":"10.1016/j.jafrearsci.2024.105448","url":null,"abstract":"<div><div>The Archean Tanzania Craton and the Bangweulu Block are separated by the Ubendian-Usagaran Belt, which developed during the Palaeoproterozoic Eburnean orogeny that produced the Congo Craton during the Columbia Supercontinent Cycle. Voluminous 1.80–1.90 Ga metagranitoids and volcanics were intruded both on the edge of the Bangweulu Block and in the Ubendian-Usagaran Belt in response to this geodynamic process. In recent years, research revealed that the extensive 1.90–1.80 Ga plutonic-volcanic suites exposed in the Ubendian- Usagaran Belt (on the Tanzania Craton side) resulted from widespread crustal anatexis caused by a regional thermal anomaly. However, the heating mechanism remains unclear. On the other (Bangweulu Block) side, high-precision chronological and geochemical data for the coeval Kate-Kipili felsic suite which crops out on the boundary of the Western Ubendian Corridor and the Bangweulu Block are scarce. The origin and tectonic setting of this suite are controversial, but crucial to understanding the crustal evolution during the Paleoproterozoic Ubendian orogeny. To address this issue, this paper is focused on the petrogenesis and tectonic setting of the Kate granitoids. New LA-ICPMS zircon U-Pb ages of the Kate granitoids revealed magmatic episodes from 1.87 to 1.90 Ga. Geochemically, the Kate granitoids belong to the magnesian alkalic-calcic rock series. They exhibit distinctive features including high Ga/Al and K₂O/Na₂O; high concentrations of Nb, Ta, Zr, and Y; and low Eu, Sr, Cr, Co, and Ni. The Kate granitoids could be classified into at least two groups in terms of geochemical characteristics, namely A2-type granites and slab failure plutons, respectively. The Kate-Kipili complex is considered to be related to the process of slab break-off, and the main difference between slab failure magmatism and A-type magmatism is probably the depth of the magma source. Slab break-off is the most likely mechanism for the magmatic intrusions and volcanism that occurred at 1.90–1.80 Ga in SW Tanzania and the Bangweulu Block.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105448"},"PeriodicalIF":2.2,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532556","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":"Crustal evolution of alternating Paleoproterozoic belts and basins in the Birimian terrane in southeastern West African Craton","authors":"Patrick Asamoah Sakyi ,&nbsp;Daniel Kwayisi ,&nbsp;Samuel Nunoo ,&nbsp;Eric Ocran ,&nbsp;Ben-Xun Su ,&nbsp;Sanjeewa P.K. Malaviarachchi","doi":"10.1016/j.jafrearsci.2024.105449","DOIUrl":"10.1016/j.jafrearsci.2024.105449","url":null,"abstract":"<div><div>We present a comprehensive review of available geochemical, geochronological and isotopic data on granitoids from the Paleoproterozoic Birimian terrane of Ghana, aimed at providing an in-depth understanding of the geodynamic evolution of southeastern West African Craton. The focus is on plutonic magmatism, crustal recycling and tectonic setting of the granitoids. The granitoids are mainly TTG suites, calc-alkaline granites, diorites, monzonites, two-mica granites and leucogranites. They are characterized by enrichments in LILE and LREE relative to HREE and HFSE. Their variable positive and negative Eu and Sr anomalies and depletions in Nb-Ta and Ti suggest the presence of residual minerals like hornblende and Fe-Ti oxides (e.g., rutile and ilmenite). The plutons probably formed by partial melting of hydrous basaltic/mafic crust metasomatized by slab-derived melts at different depths. The ɛHf (−14.5 to +7.6) and εNd (−5.3 to +3.5) values and Nd model ages (2.21–2.53 Ga) indicate their crystallization from juvenile magmas derived from a depleted mantle with significant recycling of older crustal material. The older (≥2200 Ma) and younger (&lt;2100 Ma) ages recorded in both belt- and basin-type granitoids indicate that magmatism in both types was contemporaneous. Nonetheless, the basins recorded younger peak emplacement ages compared to adjacent belts. The presence of inherited older zircon grains (Archean zircon cores?), is widespread in southeastern WAC. The granitoids formed in a continental arc setting via subduction–accretion processes. Furthermore, the magmatic time-span is more prolonged in southern Ghana, with the sedimentary basins recording the longest intervals of magma emplacement. The sub-chondritic ɛHf data and Hf model ages strongly suggest the existence of Neoarchean to Mesoarchean crustal material in eastern Ghana during the Birimian crust formation. We propose that the subduction-accretion processes during the Paleoproterozoic Eburnean orogeny in the WAC contributed to the formation of the Columbia supercontinent in the Late Paleoproterozoic-Mesoproterozoic.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105449"},"PeriodicalIF":2.2,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532555","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 source kinematics and slip distribution of the 2023 Mw 6.8 Morocco earthquake","authors":"Wenqiang Wu,&nbsp;Yongzhi Zhang,&nbsp;Xiaoye Hao,&nbsp;Jiaojiao Liu","doi":"10.1016/j.jafrearsci.2024.105451","DOIUrl":"10.1016/j.jafrearsci.2024.105451","url":null,"abstract":"<div><div>On September 8, 2023, an Mw 6.8 earthquake struck Haouz province (Morocco), in the central Atlas Mountains, causing many casualties. In this study, we obtain the co-seismic deformation field with the D-InSAR and the Pixel Offset Tracking (POT), and three-dimensional displacement with the strain model-variance component estimation method (SM-VCE). The results indicate that this earthquake belongs to a typical thrust earthquake, and the displacement components in the west-east (W-E) and vertical are quite obvious. Besides, the rupture length from the POT method is about 40 km, and the strike is west-north-west (WNW), consistent with that of the Atlas Mountains. According to the slip inversion, the rupture depth of the fault is about 30 km, and the peak slip is approximately 1.6 m at depths of about 22.75 km. Similarly, the strike is 260°, the dip angle is 70° and the rake angle is 75°, respectively. Moreover, the released energy from this earthquake is approximately a Mw 6.8 earthquake. In addition to the earthquake destruction, the local economic foundation and building structure are crucial reasons for the serious casualties. Therefore, the method in this study could provide references for seismic research and the results could help explore the focal mechanism along the High Atlas in Morocco.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105451"},"PeriodicalIF":2.2,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533129","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":"Microtectonics and fluid evolution in the Katanga Supergroup (Tenke Fungurume Mining District): Evidence of pre- to post-orogenic Cu-Co mineralization in the Central Africa Copperbelt","authors":"Pascal Mambwe ,&nbsp;Jessica Torres ,&nbsp;Dominique Jacques ,&nbsp;Stijn Dewaele ,&nbsp;Philippe Muchez","doi":"10.1016/j.jafrearsci.2024.105446","DOIUrl":"10.1016/j.jafrearsci.2024.105446","url":null,"abstract":"<div><div>The sediment-hosted stratiform copper-cobalt deposits in the Central African Copperbelt (CACB) are renowned for their resource potential, encompassing Cu-Co (Ni, U) and Cu-Zn-Pb (Ag, Ge, Mo, Cd) mineralization. Microstructural and microthermometric analyses of carbonate-quartz veins from the Tenke Fungurume mining district, situated in the central part of the Katanga Copperbelt (KCB), have delineated a pre- to post-folding paragenesis of vein formation and hypogene Cu-Co ore mineralization. The mineralization primarily consists of chalcopyrite, chalcocite, carrollite, and bornite.</div><div>Pre-folding veins comprise bedding-normal veins related to the extension stage, occasionally linked with mullion development during the following compressional stage, as well as bedding-parallel beef veins. Syn-folding mineralization manifests as saddle reef veins within fold hinge zones, fracture-filling veins aligned with tangential longitudinal strain in hinge zones of folded bedding-parallel veins, thin veinlets forming parallel to an axial-planar and shear-band cleavage, and bedding-parallel shear veinlets with oblique fiber orientations. The post-folding Cu-Co mineralization consists of veins that cross-cut earlier veins and folds.</div><div>Microthermometric analysis of fluid inclusion assemblages from the pre-, syn-, as well as post-folding veins reveals the presence of different fluid types. A high-temperature (180–340 °C) and high-salinity (27–52.5 wt% NaCl + (KCl) eq.) fluid was responsible for the Cu-Co mineralization during the pre- to syn-folding stages. A hypersaline fluid (27.0–42.1 wt% NaCl eq.) with a broad range in temperature (45–387 °C) circulated during the post-folding stage of the Lufilian orogeny. A fluid exhibiting low to moderate homogenization temperatures (28–215 °C) and low to moderate salinity (3.4–23.0 wt% NaCl eq.) is related to fluid circulation during the post-Lufilian epoch. The wide range and variations in salinity of these three fluid types associated with Cu-Co mineralization provide evidence for a multistage fluid flow and a complex hydrothermal system linked to the deposition of Cu-Co ores within the Tenke Fungurume Mining District and the broader Katanga basin. This hydrothermal system has operated during diagenesis, the basin development stage to the Lufilian orogeny and the subsequent post-Lufilian period.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105446"},"PeriodicalIF":2.2,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572189","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":"Architecture of the post-obductional Sunub Structure, northeastern Sultanate of Oman: Based on mapping, 3D gravity inversion and shale migration","authors":"Andreas Scharf ,&nbsp;Nikos Economou ,&nbsp;Frank Mattern ,&nbsp;Bader Al-Shaqsi ,&nbsp;Said Al-Abri ,&nbsp;Al-Moatasim Al-Saidi ,&nbsp;Mohammed Al-Aamri ,&nbsp;Yousuf Al-Darai ,&nbsp;Mazin Al-Dihani ,&nbsp;Malik Al-Rawahi","doi":"10.1016/j.jafrearsci.2024.105445","DOIUrl":"10.1016/j.jafrearsci.2024.105445","url":null,"abstract":"<div><div>We examined the structural evolution of the poorly understood Sunub Structure, which is associated with the northern margin of the Saih Hatat Dome and the extensional Frontal Range Fault (northeastern Oman). The Sunub Structure is located at a dextral transtensional segment and on the hanging wall of the NNE-striking Frontal Range Fault. The fault was active during the Campanian(?)/Maastrichtian to early Eocene (Interval I) and mid-/late Eocene to early Miocene (Interval II). Gravitational inversion using 175 stations and mapping shows: (1) The Sunub Structure is possibly &gt;1200–1350 m deep and filled mostly with the &gt;900-m-thick Campanian(?)/Maastrichtian siliciclastic Al-Khod Formation, including shale, and some overlying Paleogene limestones. (2) The bottom of the basin cannot be depicted. (3) The lower part of the structure is a basin (Sunub Sedimentary Basin), bounded by sub-vertical to steep contacts. (4) The upper part of the Sunub Structure is a basin fold displaying a bowl-shape down to ∼300 m below the surface, referred to as the Sunub Bowl. (5) The bowl is cut by radial faults and five ∼E/W-striking transverse faults. The Sunub Structure formed during Interval I as a deep transtensional, syn-depositional basin. Gentle post-depositional tectonics during Interval II and visco-plastic shale movements produced the present-day bowl-shape that is visible at the surface. Gravitational inversion depict possible evidence for shale migration within the Al-Khod Formation. Although no hydrocarbons are present, the Sunub Structure can serve as an analogue for hydrocarbon migration and storage in similar structures.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105445"},"PeriodicalIF":2.2,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532552","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":"Sequence stratigraphy and metre-scale cyclicity of Neoarchean dolomite strata at Bushy Park, Griqualand West Basin, Transvaal, South Africa","authors":"William Baugaard ,&nbsp;Jay M. Gregg ,&nbsp;Bruce A. Ahler","doi":"10.1016/j.jafrearsci.2024.105447","DOIUrl":"10.1016/j.jafrearsci.2024.105447","url":null,"abstract":"<div><div>Deposition of Neoarchaean carbonate platform sediments of the Campbellrand Subgroup (Transvaal Supergroup) are cyclic and exhibits a full range of facies, which extend from subtidal to supratidal deposition. The strata are host to Mississippi Valley-type lead-zinc deposits including the Pering mine and Bushy Park prospect, the latter of which is the focus of this study. Core spanning the top of the Klipfontein Heuwel Formation to the top of the Kogelbeen Formation where described in terms of the sedimentary environments that likely prevailed at the time. Key facies were identified that were used to identify parasequences and depositional sequences, which were based on stacking patterns of shoaling upward sequences and flooding surfaces. Progradational facies indicate sea level rise and retrogradational facies mark sea level fall of different magnitudes. Multiple breccia types were observed including early diagenetic, karst related breccias, slump breccias, as well as structurally controlled collapse breccias. Although an autocyclic origin for the 4th and 5th order parasequences cannot be ruled out, sedimentary parasequences in the Neoarchaean strata at Bushy Park are very similar to those recognised in Phanerozoic carbonate sections where deposition and accommodation space is believed to be controlled by orbitally forced eustatic sea level rise and fall (Milankovitch cycles). This work identifies a need to test the possible effects of Milankovitch cycles not only on other tectonic basins of similar Archean age but also other rocks through time to account for the possibility that Archean cycles are longer in duration than those of the Phanerozoic Eon.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105447"},"PeriodicalIF":2.2,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445696","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":"Integration of multivariate statistical analysis, geochemical modeling, and irrigation water quality assessment in the aquifers of the South-Atlas Tinghir-Errachidia-Boudenib basin (Pre-African Trough, Morocco)","authors":"Fadoua Laghrib ,&nbsp;Sahar Elkasmi ,&nbsp;Tarik Bahaj ,&nbsp;Azddine Barbot ,&nbsp;Mostapha Bouzekraoui ,&nbsp;Mohamed Hilali ,&nbsp;Youssef Touiss ,&nbsp;Mohamed Draoui ,&nbsp;Othmane Hammani ,&nbsp;Fatima Benammi ,&nbsp;Rachid Ben Aakame ,&nbsp;Myrieme Walid","doi":"10.1016/j.jafrearsci.2024.105444","DOIUrl":"10.1016/j.jafrearsci.2024.105444","url":null,"abstract":"<div><div>Irrigation development commonly results in the onset of salinization and soil alkalinization, to different degrees, and the irrigation water quality index (IWQI) is the main method utilized globally to assess water quality. This study aims to investigate the hydrogeochemical characteristics and irrigation suitability of groundwater in the South-Atlas region, one of the arid regions in the southeastern part of Morocco, using Principal Component Analysis (PCA) was applied to identify the main factors influencing groundwater quality and Hierarchical Cluster Analysis (HCA) was then used to classify the water samples into distinct groups based on their hydrogeochemical properties. The research also evaluates groundwater suitability for irrigation using several irrigation water quality indices (IWQIs) such as irrigation water quality index (IWQI), Sodium Adsorption Ratio (SAR), Percent Sodium (Na%), Permeability Index (PI), magnesium hazard (MH), and Potential salinity (PS) assisted by geochemical modeling and the Piper trilinear diagram. Fifty groundwater samples were systematically collected in February 2023 from various aquifers (Senonian, Infracenomanian, Quaternary, and Paleozoic) based on their geographical distribution and hydrogeological significance. The Piper diagram reflecting Ca-Mg-Cl-SO4 followed by Na-K-Cl-SO4 and Ca-Mg-HCO3 water facies under the stress of evaporation, saltwater intrusion and reverse ion exchange processes.</div><div>The results of the IWQI indicated that, roughly speaking, 0% of the samples fell into the unrestricted category, 46% had leaching restrictions ranging from low to moderate, and 54% of the samples were classified as high to severely limited, meaning that only high salt tolerance plants can be irrigated with groundwater.</div><div>The Senonian samples demonstrated excellent SAR, Na%, and PI, values, whereas most groundwater samples from other aquifers showed good to permissible suitability for irrigation. The study identified water-rock interactions, particularly in the Infracenomanian aquifer, and the use of agricultural fertilizers as significant factors affecting groundwater composition.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"221 ","pages":"Article 105444"},"PeriodicalIF":2.2,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651972","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":"Remote sensing and magnetic characterization of the Au mineralization and its structural implications: Meatiq dome, Eastern Desert, Egypt","authors":"M. Abdelwahed ,&nbsp;M. Abdelazeem ,&nbsp;A.A. Eldougdoug ,&nbsp;M.M. Gobashy ,&nbsp;Y.M. Abd El-Rahman ,&nbsp;S. Said ,&nbsp;A. Abdelhalim","doi":"10.1016/j.jafrearsci.2024.105442","DOIUrl":"10.1016/j.jafrearsci.2024.105442","url":null,"abstract":"<div><div>This article examines hydrothermally altered ophiolitic ultramafic rocks (HAOU), specifically Listvenite, which are thrust over the Meatiq dome in the context of gold mineralization. These rocks represent gneissic complexes located in Egypt's eastern desert. The analyses presented herein are essential for understanding the distribution of sheared serpentinite on and beneath the surface and the underlying domal structure. This study offers critical insights into the distribution of serpentinite at Meatiq. It combines remote sensing, aerial and ground magnetic data with petrological, geochemical, and geological analyses to create precise geological maps of potential subsurface igneous structures commonly linked to gold mineralization. Remote sensing is used to test for rock differentiation; intensive field geological investigations were conducted along several traverses. Petrographic and geochemical analysis of selected samples confirmed Au content in some localities. Additionally, tomographic inversion of the collected magnetic land profiles has unveiled previously unidentified subsurface distributions of magnetic susceptibilities, which are essential for explaining the observed surface magnetic anomalies and for understanding the subsurface arrangement of various rock units. Results show that the HAOU rocks have a lower magnetic susceptibility signature relative to the adjacent serpentinites, the serpentinite from South Meatiq shows relatively high gold content, and the gold content decreases with carbonation and alteration of the serpentinite into talc-carbonate, as detected geochemically. The procedure followed in the present study can be regionally applied to studying HAOU rocks of similar geologic conditions. The novelty of this study, beyond the introduction of a novel workflow, lies in the revelation that the rocks forming the Meatiq dome are in thrust contact with steeply dipping suprastructure units.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105442"},"PeriodicalIF":2.2,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433490","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 community structure of recent ostracods in the Burullus lagoon, Egypt","authors":"Sherif M. El Baz ,&nbsp;Abdalla Shahin ,&nbsp;Ahmed Al Furjany","doi":"10.1016/j.jafrearsci.2024.105443","DOIUrl":"10.1016/j.jafrearsci.2024.105443","url":null,"abstract":"<div><div>This work concentrates on the recent ostracod community from the bottom sediments of Burullus lagoon (BuL), Egypt. It aims to identify the impacts of the environmental factors such salinity, substrate and pH on the ostracod community. Only four ostracod species are identified, <em>Cyprideis torosa</em>, <em>Leptocythere castanea</em>, <em>Loxoconcha elliptica</em> and <em>Cypridopsis vidua</em>. The results reflect the abundance of a sole tolerant species, <em>C. torosa</em> (79.59–100 %, with an average of 94.18 %), in all sites. Actually, this conclusion reflects the dominance of unfavorable conditions for increasing the biodiversity in the lagoon. Moreover, the associated benthic foraminiferal assemblage suffers from the rarity of species and the abundance of one tolerant species, <em>Ammonia tepida</em>. Therfore, there is an urgent need to understand the environmental conditions in the BuL. The measured low salinities are suitable for the survival of only brackish ostracod species. Moreover, the distribution and structure of the ostracod assemblage are mainly controlled by the type of bottom sediments. Actually, as the content of sand increases, particularly at sites near the connection to the sea, low numbers of individuals are recorded, whereas the number of living species increases in muddy substrate. Furthermore, the sites with sandy substrate display thick-walled carapaces, while the others with muddy substrate possess thin-walled carapaces. Also, the occurrence of <em>Cypridopsis vidua</em> is restricted only to the muddy substrate. In terms of the hydraulic conditions, the highest abundance of living species is recorded in the southern part, where the quiet conditions prevail. The lagoon water is alkaline, so pH has no observed effects on the ostracod community. Accordingly, salinity, sediment types and hydraulic conditions play the major role in controlling the abundabce, diversity and distribution of ostracods in the study area. Geographically, the identified ostracod species are broadly distributed in the brackish lagoons of the Mediterranean region.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105443"},"PeriodicalIF":2.2,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433491","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":"Constraints of the regional deformation on the hydrothermal veins in Ousdrat and Aït Ahmane ore deposits (Bou Azzer-El Graara inlier, central Anti-Atlas, Morocco): Implications for mineral exploration","authors":"Saber Salmi ,&nbsp;Ezzoura Errami ,&nbsp;Abdellatif Jouhari ,&nbsp;Jamal El Kabouri ,&nbsp;Nasser Ennih ,&nbsp;Omar Outaaoui ,&nbsp;Said Ilmen ,&nbsp;Younes Moundi ,&nbsp;Abdelhak Karfal ,&nbsp;Lhou Maacha","doi":"10.1016/j.jafrearsci.2024.105441","DOIUrl":"10.1016/j.jafrearsci.2024.105441","url":null,"abstract":"<div><div>The overlap of tectonic and magmatic events in the Bou Azzer-El Graara inlier causes a complexity for understanding the absolute and/or relative chronology between the deformation and the hydrothermal system. In the central northern part of the Bou Azzer-El Graara inlier, syn-orogenic ca. 650 Ma Aït Ahmane and Ousdrat plutons have been deformed under NE-SW shortening and with metamorphic conditions. These plutons are affected by fault systems with four mains directions: N015, N090, N140, and N040. The last two fault systems are the most mineralized and they are weakly constrained in the frame of deformation phases affecting the Bou Azzer inlier, and filling style. In addition, Pan-African, WACadomian or Hercynian origin of NE-SW faults is not yet reached. This contribution aims to clarify these issues based on structural, textural and morphological of these faults and veins. Our analyses highlight that most of these structures were formed through open-space filling and crack-seal-slip mechanisms. N140 contacts faults between serpentinite and quartz diorite experienced multiple reactivations during the WACadomian stages. The oldest activation was in ductile condition and later reactivated in a transpression to transtension regime leading to the development of N040 faults as sinistral antithetic faults due to NNE stress evolution. Field observations suggest that N040 structures affect late Ediacaran Ouarzazate Group, but not the Adoudounian Formation, highlight their WACadomian origine. The N040 structures preserve metric to microscopic cataclastic shear zones. This evolution suggests that the hydrothermal system in the Bou Azzer inlier shifted from ductile-brittle hydrothermal style along the N140 foliated contact to a brittle regime along the N040 sinistral-normal faults. Some intra-vein microtextures suggest that this hydrothermal fluid was emplaced in a predominantly extensional and tectonically active environment, as evidenced by extensional relay, syntaxial and antiaxial textures, and elongated grains. Consequently, a detailed analysis of the morphology, textures, filling types, and fault movements is an essential and important tool for establishing the relative chronology of deformation in front of the N140 and N040 veins.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105441"},"PeriodicalIF":2.2,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532553","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}