Petrography and geochemistry of manganiferous rocks in the Mankwadzi area in the southern Kibi‐Winneba metavolcanic belt,Ghana: Implications for genesis of Mn formations in the Birimian of West Africa     

Kwabina Ibrahim  Frank K. Nyame  Thomas Armah  Johnson Manu  Jeff Baah‐Acheamfour  Jacob Tigme 《Island Arc》2020,29(1)

Manganiferous rocks in the Mankwadzi area in the southernmost portion of the Kibi‐Winneba metavolcanic belt, one of several Mn occurrences in the Paleoproterozoic Birimian of Ghana, are hosted in hornblende schist and amphibolite. These rocks are, in places, intruded by hornblende dyke. In outcrop, the manganiferous rocks appear to be conformable with the host schist and amphibolite, are macroscopically dark, fine‐grained and structurally massive to distinctly banded. Observed alternating light and dark occasionally macro‐folded bands suggest post‐depositional deformation of both light and dark bands. Microscopic observations revealed that the light bands are dominantly Si‐rich and the dark bands mainly of opaque minerals. Whole rock analyses of the manganiferous rocks show high contents of MnO (16.75–27.4 wt%) suggesting that the opaque minerals are likely rich in Mn. The analyzed rock samples show moderate to strong enrichments in light rare earth elements compared to heavy rare earth elements. Whereas the manganiferous rocks show perceptibly negative Eu anomaly, host hornblende schist and hornblende dyke do not. Eu anomaly in amphibolite samples is, however, uncertain as the three samples analyzed gave positive, negative and no Eu anomalies. Based on the field characteristics, microscopic and geochemical features, we suggest that the Mn occurrence in the Mankwadzi area originated via sedimentary deposition and was later modified by metamorphism, hydrothermal and/or supergene processes similar to manganiferous occurrences at Nsuta and Tambao in the Birimian of West Africa.  相似文献   

Inversion-based deblending using migration operators     

Amr Ibrahim  Daniel Trad 《Geophysical Prospecting》2020,68(8):2459-2470

In this paper, we compare the denoising- and inversion-based deblending methods using Stolt migration operators. We use Stolt operator as a kernel to efficiently compute apex-shifted hyperbolic Radon transform. Sparsity promoting transforms, such as Radon transform, can focus seismic data into a sparse model to separate signals, remove noise or interpolate missing traces. Therefore, Radon transforms are a suitable tool for either the denoising- or the inversion-based deblending methods. The denoising-based deblending treats blending interferences as random noise by sorting the data into new gathers, such as common receiver gather. In these gathers, blending interferences exhibit random structures due to the randomization of the source firing times. Alternatively, the inversion-based deblending treats blending interferences as a signal, and the transform models this signal by incorporating the blending operator to formulate an inversion problem. We compare both methods using a robust inversion algorithm with sparse regularization. Results of synthetic and field data examples show that the inversion-based deblending can produce more accurate signal separation for highly blended data.  相似文献   

Variability of water exchanges through the Strait of Hormuz     

Vasou  Panagiotis  Vervatis  Vassilios  Krokos  George  Hoteit  Ibrahim  Sofianos  Sarantis 《Ocean Dynamics》2020,70(8):1053-1065

Ocean Dynamics - The variability of the water mass exchange between the Arabian Gulf and the Indian Ocean is investigated using a high-resolution (1/36°) ocean model. We focus on the period...  相似文献   

International viewpoint and news     

M. Al Ibrahim  D. Govoni 《Environmental Geology》2008,55(2):465-466

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Paleomagnetism of Carboniferous sediments from the West Sudetes (SW Poland)     

Kądziałko-Hofmokl  Magdalena  El-Hemaly  Ibrahim Aly 《Geologie en Mijnbouw》1997,76(1-2):97-104

The studied Carboniferous flysch and molasse sediments from the Intra-Sudetic Basin correspond to the period from Middle Visean to Early Autunian. Main magnetic minerals carrying the natural remanent magnetization (NRM) are goethite, magnetite, maghemite and hematite, all usually secondarily formed and/or remagnetized due to several tectonometamorphic events. In most samples several NRM components were isolated. One of them is usually a Jurassic-Triassic overprint. Some others define the Westphalian-Early Permian segment of the declination and inclination trajectory for the Sudetes calculated according to the reference apparent polar wander path for the Baltica plate. The Sudetic path is slightly shifted to the east compared to the reference path, suggesting the possibility of independent movements of the Sudetes during this time. The majority of isolated NRM components are secondary and related to the Sudetic orogenic phase and later tectonometamorphic activity.  相似文献   

Effect of hot dry summer tropical climate on forage intake and milk yield in Holstein–Friesian and indigenous zebu cows in Sudan     

Muna Mahjoub M Ahmed  Adam Ibrahim El Amin 《Journal of Arid Environments》1997,35(4):737-746

The effects of dry summer ambient temperature on some physiological and productive responses were studied in an exotic European breed (Holstein–Friesian) and a local zebu breed (Butana ecotype) of cattle in Sudan. Rectal temperature and respiration rate were positively correlated, and dry matter intake and milk yield were negatively correlated with variation in ambient temperature. However, significant adverse effects on high ambient temperature were only observed in the exotic breed.  相似文献   

The Southern Sudanese migration to Khartoum and the resultant conflicts     

F. N. Ibrahim Prof. Dr. 《GeoJournal》1991,25(1):13-18

Today, more than one third of the population of Khartoum are southerners who migrated to the capital mainly in the last eight years because of the civil war. Their conditions are very bad. They are starving in the town, for most of them are unemployed and have no means of living. Their housing conditions in the shanty towns are deplorable. The development of squatter settlements and the struggle for the demarcation of quarters are delineated in this paper. In Khartoum the southerners develop a strong sense of solidarity and develop a growing supra-southern-Sudanese identity replacing the former ethnic and local identities.  相似文献   

Tracking the hydrodynamic behavior of fine sediment using particle image velocimetry     

Masoumeh MoayeriKashani  S. H. Lai  S. Ibrahim  N. M. N. Sulaiman  F. Y. Teo 《Environmental Earth Sciences》2016,75(8):676

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Middle Miocene ostracods from Wadi Sudr,westcentral Sinai,Egypt: systematic,biostratigraphy and palaeobiogeographic affinity with the Mediterranean realm     

Ibrahim M. Ied  Abdelmoneim S. A. Ismail 《Arabian Journal of Geosciences》2016,9(5):406

The investigation of the exposed middle Miocene strata from Wadi Sudr yielded well-preserved ostracod carapaces. Detailed taxonomic and paleontological studies led to the recognition of 36 ostracod species belonging to 25 genera, 4 species of them were considered new which fully described. Three assemblage biozones were recorded as follows: Actinocythereis spinosa–Actinocythereis hystrix zone, Chrysocythere cataphracta muricata-Cytheretta africana zone, and Disopontocypris schweijeri-Bythocypris tripolensis zone. The recorded biozones were calibrated with the previously studied middle Miocene planktonic foraminiferal biozones on the same samples and also correlated with the Miocene ostracod biozones from the neighboring countries. Our ostracod assemblages present in the lower and upper parts of the studied section (section II) indicated an inner neritic marine environment of moderate energy of currents and rapid sedimentation, while the assemblages in the middle part showed more deeper (outer neritic) environments with low energy of currents and low rate of sedimentation. The palaeobiogeographic distribution of the studied ostracods showed high affinity with the ostracod assemblages of the southern Mediterranean and moderate to low affinities with that of the northern and eastern Mediterranean respectively. The highly ornamented ostracod species with structures on the carapace were recorded from both Northern and Southern Mediterranean, while the smooth ones were found in the Southern Mediterranean only. The highly ornamented species are more widely distributed in both Southern and Northern Mediterranean than the smooth species. This may indicate that the ornamented species are more able to migrate than the smooth ones.  相似文献   

Biodegradation of Remazol Black B in sequential microaerophilic–aerobic operations by NAR-2 bacterial consortium     

S. Nazanin Kardi  Noor Aini Abdul Rashid  Norahim Ibrahim  Azura Ahmad 《Environmental Earth Sciences》2016,75(16):1172

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