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Journal of African earth sciences 37건

  1. [해외논문]   An integrated approach to evaluate the Aji-Chai potash resources in Iran using potential field data   SCIE

    Abedi, Maysam (Department of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran)
    Journal of African earth sciences v.139 ,pp. 379 - 391 , 2018 , 1464-343x ,

    초록

    Abstract This work presents an integrated application of potential field data to discover potash-bearing evaporite sources in Aji-Chai salt deposit, located in east Azerbaijan province, northwest of Iran. Low density and diamagnetic effect of salt minerals, i.e. potash, give rise to promising potential field anomalies that assist to localize sought blind targets. The halokinetic-type potash-bearing salts in the prospect zone have flowed upward and intruded into surrounded sedimentary sequences dominated frequently by marl, gypsum and alluvium terraces. Processed gravity and magnetic data delineated a main potash source with negative gravity and magnetic amplitude responses. To better visualize these evaporite deposits, 3D model of density contrast and magnetic susceptibility was constructed through constrained inversion of potential field data. A mixed-norm regularization technique was taken into account to generate sharp and compact geophysical models. Since tectonic pressure causes vertical movement of the potash in the studied region, a simple vertical cylindrical shape is an appropriate geometry to simulate these geological targets. Therefore, structural index (i.e. decay rate of potential field amplitude with distance) of such assumed source was embedded in the inversion program as a geometrical constraint to image these geologically plausible sources. In addition, the top depth of the main and the adjacent sources were estimated 39 m and 22 m, respectively, via the combination of the analytic signal and the Euler deconvolution techniques. Drilling result also indicated that the main source of potash starts at a depth of 38 m. The 3D models of the density contrast and the magnetic susceptibility (assuming a superficial sedimentary cover as a hard constraint in the inversion algorithm) demonstrated that potash source has an extension in depth less than 150 m. Highlights Geophysical responses of the potash resource. 3D models of density contrast and magnetic susceptibility. Mixed-norm regularization technique to create sharp and compact model. Proposing a plausible geological model.

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  2. [해외논문]   Geochemical mapping of radioactive elements using helicopter-borne γ-ray spectrometry (Tiouit, Eastern Anti-Atlas, Morocco): Or occurrence and environmental impact  

    Miftah, Abdelhalim , El Azzab, Driss , Attou, Ahmed , Manar, Ahmed , Rachid, Ahmed , Ramhy, Haytam
    Journal of African earth sciences v.139 ,pp. 392 - 402 , 2018 , 1464-343x ,

    초록

    Abstract This work presents an integrated application of potential field data to discover potash-bearing evaporite sources in Aji-Chai salt deposit, located in east Azerbaijan province, northwest of Iran. Low density and diamagnetic effect of salt minerals, i.e. potash, give rise to promising potential field anomalies that assist to localize sought blind targets. The halokinetic-type potash-bearing salts in the prospect zone have flowed upward and intruded into surrounded sedimentary sequences dominated frequently by marl, gypsum and alluvium terraces. Processed gravity and magnetic data delineated a main potash source with negative gravity and magnetic amplitude responses. To better visualize these evaporite deposits, 3D model of density contrast and magnetic susceptibility was constructed through constrained inversion of potential field data. A mixed-norm regularization technique was taken into account to generate sharp and compact geophysical models. Since tectonic pressure causes vertical movement of the potash in the studied region, a simple vertical cylindrical shape is an appropriate geometry to simulate these geological targets. Therefore, structural index (i.e. decay rate of potential field amplitude with distance) of such assumed source was embedded in the inversion program as a geometrical constraint to image these geologically plausible sources. In addition, the top depth of the main and the adjacent sources were estimated 39 m and 22 m, respectively, via the combination of the analytic signal and the Euler deconvolution techniques. Drilling result also indicated that the main source of potash starts at a depth of 38 m. The 3D models of the density contrast and the magnetic susceptibility (assuming a superficial sedimentary cover as a hard constraint in the inversion algorithm) demonstrated that potash source has an extension in depth less than 150 m. Highlights Geophysical responses of the potash resource. 3D models of density contrast and magnetic susceptibility. Mixed-norm regularization technique to create sharp and compact model. Proposing a plausible geological model.

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  3. [해외논문]   Geochemical mapping of radioactive elements using helicopter-borne gamma-ray spectrometry (Tiouit, Eastern Anti-Atlas, Morocco): Or occurrence and environmental impact   SCIE

    Miftah, Abdelhalim (Research Team of Geology of the Mining and Energetics Resources, Faculty of Science and Technology, University Hassan 1, BP 577, Settat, Morocco ) , El Azzab, Driss (Laboratory of Geo-resources and Environment, Faculty of Science and Technology, University Sidi Mohamed Ben Abdellah, BP 2202, Fez, Morocco ) , Attou, Ahmed (Research Team of Geology of the Mining and Energetics Resources, Faculty of Science and Technology, University Hassan 1, BP 577, Settat, Morocco ) , Manar, Ahmed (Ministry of the Energy, Mines and Sustainable Development, BP Rabat Instituts, 6208, Haut Agdal, Morocco ) , Rachid, Ahmed (Research Team of Geology of the Mining and Energetics Resources, Faculty of Science and Technology, University Hassan 1, BP 577, Settat, Morocco ) , Ramhy, Haytam (Research Team of Geology of the Mining and Energetics Resources, Faculty of Science and Technology, University Hassan 1, BP 577, Settat, Morocco)
    Journal of African earth sciences v.139 ,pp. 392 - 402 , 2018 , 1464-343x ,

    초록

    Abstract The spectrometric prospection is a direct geophysical method based on the analysis of the radioactive elements spectra, due to three principal radioactive elements 4 0 K, 238 U and 232 Th. In order to measure the content of radioactive elements a geophysical helicopter survey was carried out to a flight altitude of 60 m from the subsoil, covering the geological map of Tiouit 1/50000 with an extent of 45.5 × 29 km 2 . In this paper, we propose an application in the environment and or occurrence by the production of maps concentration in K, U and Th to delimit the areas with purely natural radioactive risk by the calculation of the dose rate in mSv, the found values show a variation of 0,3 to 1.649 mSv with a median value of 0,831 mSv. Moreover, data processing as the horizontal gradient filter which allowed to amplify the spectrometric signatures, this one coupled to the upward continuation, lead us to a better location of the abrupt changes, which materialize by spectrometric lineaments, reflecting the change of the geochemical properties of the basement. Highlights High-resolution helicopter-borne gamma-ray spectrometry. Or occurrence and environmental impact of Tiouit, Eastern Anti-Atlas, Morocco. Delimitation of purely natural radioactive risk from the rate of exposure. Data processing by the horizontal gradient coupled to upward continuation filter. Structural cartography of spectrometric lineaments.

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  4. [해외논문]   Paleomagnetism of the Cretaceous Galula Formation and implications for vertebrate evolution   SCIE

    Widlansky, Sarah J. (Department of Earth Sciences, University of New Hampshire, Durham, NH, 03824, USA ) , Clyde, William C. (Department of Earth Sciences, University of New Hampshire, Durham, NH, 03824, USA ) , O'Connor, Patrick M. (Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, 228 Irvine Hall, Athens, OH, 45701, USA ) , Roberts, Eric M. (Department of Geosciences, James Cook University, Townsville, Queensland, Australia ) , Stevens, Nancy J. (Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, 228 Irvine Hall, Athens, OH, 45701, USA)
    Journal of African earth sciences v.139 ,pp. 403 - 420 , 2018 , 1464-343x ,

    초록

    Abstract This study uses magnetostratigraphy to help constrain the age of the paleontologically important Galula Formation (Rukwa Rift Basin, southwestern Tanzania). The formation preserves a Cretaceous vertebrate fauna, including saurischian dinosaurs, a putative gondwanatherian mammal, and notosuchian crocodyliforms. With better dating, the Galula Formation and its fossils help fill a temporal gap in our understanding of vertebrate evolution in continental Africa, enabling better evaluation of competing paleobiogeographic hypotheses concerning faunal exchange throughout Gondwana during the Cretaceous. Paleomagnetic samples for this study were collected from the Namba (higher in section) and Mtuka (lower in section) members of the Galula Formation and underwent stepwise thermal demagnetization. All samples displayed a strong normal magnetic polarity overprint, and maximum unblocking temperatures at approximately 690 °C. Three short reversed intervals were identified in the Namba Member, whereas the Mtuka Member lacked any clear reversals. Given the relatively limited existing age constraints, one interpretation correlates the Namba Member to Chron C32. An alternative correlation assigns reversals in the Namba Member to recently proposed short reversals near the end of the Cretaceous Normal Superchron (Chron C34), a time that is traditionally interpreted as having stable normal polarity. The lack of reversals in the Mtuka Member supports deposition within Chron C34. These data suggest that the Namba Member is no older than Late Cretaceous (Cenomanian-Campanian), with the Mtuka Member less well constrained to the middle Cretaceous (Aptian-Cenomanian). The paleomagnetic results are supported by the application of fold and reversal tests for paleomagnetic stability, and paleomagnetic poles for the Namba (246.4°/77.9°, α 95 5.9°) and Mtuka (217.1°/72.2°, α 95 11.1°) members closely matching the apparent polar wander path for Africa during the Late Cretaceous. These results confidently indicate a Late Creteceous age assignment for the Namba Member of the Galula Formation, a unit that has yielded key crocodyliform (e.g., Pakasuchus ; Rukwasuchus ) and dinosaur (e.g., Rukwatitan; Shingopana ) fossils from eastern Africa. Highlights New paleomagnetic results from the Cretaceous Galula Formation of southwest Tanzania offer additional age constraint. Namba Member consistent with deposition during the Late Cretaceous. Mtuka Member consistent with deposition in the middle Cretaceous during the Cretaceous Normal Superchron.

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  5. [해외논문]   Geochemistry, petrology and geodynamic setting of the Urumieh plutonic complex, Sanandaj–Sirjan zone, NW Iran: New implication for Arabian and Central Iranian plate collision   SCIE

    Jafari, Amin (Department of Geology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran ) , Fazlnia, Abdolnaser (Department of Geology, Faculty of Sciences, Urmia University, Urmia, Iran ) , Jamei, Susan (Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran)
    Journal of African earth sciences v.139 ,pp. 421 - 439 , 2018 , 1464-343x ,

    초록

    Abstract The Urumieh plutonic complex, in the northernmost part of Sanandaj-Sirjan zone (SSZ) of Iran, consists of ten basic-acidic units which formed in response to subduction and continental collision of the SSZ with the Arabian plate to the south during Mid-Late Cretaceous times. Geochemically, the plutonic unit is divided into three distinct groups: I-type, S-type and A-type that mainly belong to calc-alkalic series. The I-type intrusions, especially mafic members, are enriched in LREE and LILE and possibly formed from metasomatized mantle wedge during the subduction of the Neo-Tethys oceanic crust beneath the SSZ. The felsic I-type rocks are depleted in Ba, Sr, Nb, Ta, Ti and Eu, but enriched in Rb, Th, K, Ce, U and La. These data suggest that they formed in deep crustal levels via partial melting of crustal sources by injection of hot mantle magmas. The S-type rocks are characterized by low Na 2 O ( 2 O 3 /(MgO+FeO) and K 2 O/Na 2 O ratios combined with low CaO/(MgO+FeO*) ratios. These features show that the S-type granites originated from partial melting of a metapelitic to metagreywacke source. The A-type alkali feldspar granites formed through the slab break off after the continental collision in northwestern Iran by decompression melting of crustal protolith. The author's new model implies that collision between Arabian margin and north SSZ initiated in the Late Cretaceous and completed until Late Paleocene. In contrast, in the southeast, subduction was active during this period of time, but collision presumably occurred during the Middle to Late Miocene. Highlights The Urumieh plutonic complex is divided into I, S and A types intrusions. The rocks generated from different source rocks. All plutonic rocks from the Sanandaj-Sirjan Zone are related to oblique subduction of neotethys beneath the Central Iran. The collision between Arabian margin and Iranian plate has been different from north to south.

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  6. [해외논문]   Geometric-kinematic characteristics of the main faults in the W-SW of the Lut Block (SE Iran)   SCIE

    Rashidi Boshrabadi, Ahmad (Phd Student, Department of Geology, University of Birjand, Birjand, Iran ) , Khatib, Mohamad Mahdi (Professor (Full), Department of Geology, University of Birjand, Birjand, Iran ) , Raeesi, Mohamad (PhD in Seismology, Independent Researcher, SeisAnalysis AS, Bergen, Norway ) , Mousavi, Seyed Morteza (Assistant Professor, Department of Geology, University of Birjand, Birjand, Iran ) , Djamour, Yahya (Associate Professor, National Cartographic Center of I.R., Tehran, Iran)
    Journal of African earth sciences v.139 ,pp. 440 - 462 , 2018 , 1464-343x ,

    초록

    Abstract The area to the W-SW of the Lut Block in Iran has experienced numerous historical and recent destructive earthquakes. We examined a number of faults in this area that have high potential for generating destructive earthquakes. In this study a number of faults are introduced and named for the first time. These new faults are Takdar, Dehno, Suru, Hojat Abad, North Faryab, North Kahnoj, Heydarabad, Khatun Abad and South Faryab. For a group of previously known faults, their mechanism and geological offsets are investigated for the first time. This group of faults include East Nayband, West Nayband, Sardueiyeh, Dalfard, Khordum, South Jabal-e-Barez, and North Jabal-e-Barez. The N-S fault systems of Sabzevaran, Gowk, and Nayband induce slip on the E-W, NE-SW and NW-SE fault systems. The faulting patterns appear to preserve different stages of fault development. We investigated the distribution of active faults and the role that they play in accommodating tectonic strain in the SW-Lut. In the study area, the fault systems with en-echelon arrangement create structures such as restraining and releasing stepover, fault bend and pullapart basin. The main mechanism for fault growth in the region seems to be ‘segment linkage of preexisting weaknesses’ and also for a limited area through ‘process zone’. Estimations are made for the likely magnitudes of separate or combined failure of the fault segments. Such magnitudes are used in hazard analysis of the region. Highlights A number of active faults are introduced and named for the first time. Investigated are the distribution of active faults and the role that they play in tectonic strain. The main mechanism for fault growth in SW-Lut is ‘segment linkage of preexisting weaknesses’. Estimations are made for the likely magnitudes of combined failure of the fault segments.

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  7. [해외논문]   Lithofacies, paleoenvironment and high-resolution stratigraphy of the D5 and D6 members of the Middle Jurassic carbonates Dhruma Formation, outcrop analog, central Saudi Arabia   SCIE

    Yousif, Ibrahim M. (Corresponding author. P.O Box 8214, Dhahran 31261, Saudi Arabia.) , Abdullatif, Osman M. , Makkawi, Mohammad H. , Bashri, Mazin A. , Abdulghani, Waleed M.
    Journal of African earth sciences v.139 ,pp. 463 - 479 , 2018 , 1464-343x ,

    초록

    Abstract This study characterizes the lithofacies, paleoenvironment and stratigraphic architecture of the D5 and D6 members of carbonates Dhruma Formation outcrops in central Saudi Arabia. The study integrates detailed lithofacies analysis based on vertical and lateral profiles, in addition to thin-sections petrography to reveal the high-resolution architecture framework. Nine lithofacies types (LFTs) were defined namely: (1) skeletal peletal spiculitic wackestone (15%), (2) peloidal echinoderm packstone (19%), (3) fissile shale (36%), (4) peloidal spiculitic echinoderm pack-grainstone (5%), (5) cross-bedded peloidal skeletal oolitic grainstone (7%), (6) oolitic grainstone (2%), (7) intraformational rudstone ( th to 6 th orders magnitude, and thickness ranges from a few centimeters up to 6 m with an average of 1.5 m. Those are stacked to form four high-frequency sequences with thickness range from 1 m up to 14 m. The latter were grouped into a single depositional sequence of 3 rd order magnitude. The architectural analysis also shows that the potential reservoir units were intensively affected by muddy-textured rocks which act as reservoir seals. These variations in the stratigraphic sequences in Middle Jurassic Dhruma Formation and its equivalents could be attributed to the eustatic sea-level changes, climate, tectonics, and local paleoenvironments. This study attempts to provide detailed insight into reservoir heterogeneity and architecture. The analog may help to understand and predict lithofacies heterogeneity, architecture, and quality in the subsurface equivalent reservoirs. Highlights This study integrates sedimentology with stratigraphic results of Dhruma carbonates. Nine lithofacies types were defined in the studied outcrops of the D5 and D6 members. The paleoenvironment ranges from distal-to-proximal carbonate ramp setting. 53 cycles and cycle sets, and four high-frequency sequences were defined.

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