Ovaj rad govori o parametrima koji utječu na izgled i kvalitetu šava. To su pređa za šivanje, vrsta i duljina uboda, debljina igle, oblik vrha igle te smještaj i stanje šivaćeg stroja.
•U–Pb detrital zircon ages from Neoproterozoic sediments of the ANS are presented.•The Wadi Igla Formation in the Eastern Desert of Egypt was deposited at ≤628±6Ma.•The Thalbah Group sediments span a ...depositional period between ca. 635 and 596Ma.•The Thalbah Group has a multi-phase Cryogenian-early Ediacaran tectonic evolution.•Detrital zircon age distributions may reflect the onset of collision at ca. 596Ma.
Detrital zircon U–Pb SIMS dating is used to evaluate the provenance of two correlative basins in the Arabian-Nubian Shield (ANS). The Wadi Igla Formation in the Central Eastern Desert (CED) of Egypt and the Thalbah Group in the Midyan Terrane (MT) of NW Saudi Arabia are considered to be post-amalgamation terrestrial basins, developed during closure of the Mozambique Ocean and amalgamation of the ANS in Cryogenian-early Ediacaran time. The analytical results indicate that the upper-part of the Wadi Igla Formation has a maximum depositional age of 628±6Ma, contains 98% Neoproterozoic zircon with ages between 815 and 628Ma, and has two distinct peaks at 690Ma and 652Ma. A rhyolite clast from the upper-part of the Wadi Igla Formation gives a U–Pb age of 700±6Ma. This age significantly pre-dates Dokhan volcanism, indicating that the dominant rhyolitic clasts within the Wadi Igla Formation are not from the Dokhan Volcanics, as previously believed. Analytical results from the Thalbah Group suggest multiphase basin formation and development. The lower part of the Thalbah Group is intruded by monzogranites of the Liban complex, has a minimum depositional age of 635±5Ma, resembling that of the Wadi Igla Formation. Its middle part has a maximum age of 612±7Ma and is comprised of 90% Neoproterozoic zircon with ages ranging from 820 to 612Ma. The upper part of the Thalbah Group has a maximum age of 596±10Ma and contains a wider range of Neoproterozoic detritus with ages between 985 and 596Ma. The basement of the Thalbah Group is represented by metasediments and metavolcanics of the Zaam Group. The sample collected from the uppermost part of the Zaam Group (Um Ashsh Formation) contains zircon of mostly Cryogenian age (ca. 812–697Ma) and has a maximum age of 700±4Ma, suggesting that the Zaam Group might be correlative with the subduction-related metavolcanic and metasedimentary rocks that are overlain unconformably by the Wadi Igla Formation in the CED.
The Wadi Igla basin and the lower and middle parts of the Thalbah basin have similar provenance, record a Cryogenian-early Ediacaran age, and represent syn-subduction (rather than post-amalgamation) basins. The upper part of the Thalbah Group, in contrast, has a distinct provenance representing an Ediacaran syn-collisional basin. The narrow age range of the Wadi Igla Formation and the lower and middle parts of the Thalbah Group indicates a restricted source from the CED and MT island arc basement, whereas the wide age range for the upper part of the Thalbah Group indicates a contribution from other parts of the ANS. The sediment sources and the age patterns of detrital zircons change abruptly at ca. 596Ma. This may coincide with the onset of collision of the CED and MT basements with the older Hijaz-Gebeit terrane (850–680Ma) to the south along the Yanbu-Onib-Sol Hamed-Gerf-Allaqi-Heiani (YOSHGAH) suture in the ANS during the East African Orogeny.
•Percentage of blade-shaped pebbles in Hammamat conglomerates is sensitive to pebble strains.•Existing finite strain estimates in gneisses need to be confirmed using markers other than metamorphic ...grain shapes and grain centres.•Dilatation via pressure solution or microveining is likely to be a more common condition that currently thought.•Strain maps and identification of regional strain gradients are in great need for the ENS.
More than seventy strain studies in the Egyptian Nubian Shield (ENS) are reviewed in this contribution. For the Hammamat basin strain studies, Rf/ϕ and Fry methods have been applied to pebble sections, mudcracks and raindrop prints. Consideration of pebble fabrics in undeformed outcrops suggests that RXZ estimates of less than 1.7 based on pebble ellipse data are doubtful. Extracted pebbles are also popular strained objects for analysis. Average Wadell sphericity and percentage of blades assist recognition of pebble strains in the Kareim, Queih, Igla and Seleimat basins. Feiran gneissic complex strains, measured using boudins and folds are much higher (X/Z > 15) than the reported strains for the Hafafit gneissic complex (X/Z usually < 2.5) that used metamorphic grain shapes and centres. The low Hafafit strains may result from progressive resetting of grain shapes and relocation of grains by diffusional effects during HT metamorphism. The Barramiya-Mubarak thrust belt provides a good example of focused study on ENS shear zones strain, with variable correlations between Rf/ϕ and Fry results, but consistently low k values. South Eastern Desert (SED) shear zone prolate strain ellipsoids record the effects of multiple deformation. The extensional shear zone overlying the Meatiq complex shows extreme strain and strongly prolate strain ellipsoids. ENS vorticity studies, applying PAR and RGN methods, have yielded higher Wm (> 0.5) for transpressional shears (Barramiya-Mubarak belt and Atalla shear zone) than for transtensional shears (Wm < 0.5). Volume strains have rarely been considered in the ENS, though evidence exists for negative (due to pressure solution) and positive (due to microveining) volume change during deformation. The ENS strain database can be improved by better documentation of sampling methods; better knowledge of primary fabrics; and by testing strain results using a range of materials. AMS-strain studies may broaden the range of lithologies suitable for strain measurement.
This article discusses in detail the ability of Landsat-8 remotely sensed data to recognize and map Neo-proterozoic basement rocks in the Igla area. The Igla area in the Central Eastern Desert of ...Egypt is covered by a variety of Neo-proterozoic rocks comprising three tectonostratigraphic assemblages: ophiolitic, island arc, and late-to-post-tectonic assemblages. Lithological and structural mapping was achieved using Landsat-8 image data analysis, field verification, and microscopic studies. Image enhancement techniques have been applied using correlation coefficient and optimum index factor for selecting the best false-color composite, principal component analysis (PCA), and band ratio images. Based on spectral signatures, the supervised classification provided useful information and substantially improved geological mapping. The spectral measurements of the rock samples from the study area were integrated with previously obtained data, and the improved and enhanced methods were used to yield good results. Principal component analysis (PCA) (PC4, PC1, and PC3) and band ratio (6/5, 4/3, and 2/1) and (4/2, 6/7, and 5/6) in RGB with supervised classification techniques have been proven to be the best for distinguishing between the different rock units. A comparison between the map in the current study and the published geologic maps of the Igla area and field verification indicates that the present mapping, identification, and discrimination of lithological units are more accurate and much better. Accordingly, we recommend the present processing enhancement using remote sensing techniques for geological studies in the Eastern Desert of Egypt and similar arid areas worldwide.
Lightning striking on power system may lead to severe accident and huge losses, which is the reason why line arresters are needed. During operation, the electrical field concentration in line ...arrester may lead to ablation and accelerated aging of insulation materials, and furthermore, cause mal-operation. A type of line arresters with internal series air gap (IGLA) is chosen by this study, which is distinguished from the previously used metallic oxide arrester, with better characteristic on anti-flashover when icing, but with worse characteristic on anti-flashover when polluted. This paper aims at studying the probable variation of power-frequency electric field of this new kind of IGLA under polluted and icing situation, and making further analysis on the reason why the electric field strength change like this.
The geological and geophysical data primarily on the structure of the upper sedimentary sequence of the northern Knipovich Ridge (Norwegian-Greenland Basin) that were obtained during Cruise 24 of the ...R/V
Akademik Nikolai Strakhov
are considered. These data indicate that the recent kinematics of the northern Knipovich Ridge is determined by dextral strike-slip displacements along the Molloy Fracture Zone (315° NW). This stress field is superimposed by a system related to rifting and latitudinal opening of rifts belonging to the ridge proper. Thus, the structural elements formed under the effect of two stress fields are combined in this district. Several stages of tectonic movements are definable. The first stage (prior to 500 ka ago) is marked by the dominant normal faults, which are overlain by the lower and upper sedimentary sequences. The second stage (prior to 120–100 ka ago) is characterized by development of normal and reverse faults, which displace the lower sequence and are overlain by the upper sequence. Both younger and older structural features reveal peaks of tectonic activity separated by intermediate quiet periods 50–60 ka long. The stress field of the regional strike-slip faulting is realized in numerous oblique NE-trending normal and normal-strike-slip faults that divide the rift valley and its walls into the segments of different sizes. Their strike (20°–30° NE) is consistent with a system of secondary antithetic sinistral strike-slip faults. The system of depressions located 40 km west of the rift valley axis may be considered a paleorift zone that is conjugated at 78°07′ N and 5°20′ W with the NW-trending fault marked by the main dextral offset. The stress field that existed at this stage was identical to the recent one. The rift valley axis migrated eastward to its present-day position approximately 2 Ma ago (if the spreading rate of ∼0.7 cm/yr is accepted). The obtained data substantially refine the understanding of the initial breakup of continents with the formation of oceanic structural elements. The neotectonic stage is characterized by combination of different stress fields that resulted in the formation of a complex system of tectonic structural units, including those located beyond the recent extension zone along the rift axis of the Knipovich Ridge. The tectonic deformations occurred throughout the neotectonic stage as discrete recurrent events.
Kasno brončano doba istočne obale Jadrana obilježili su složeni i iznimno dinamični kulturni procesi zabilježeni u različitim arheološkim zapisima, a ponajbolje u materijalnoj kulturi. U tom nam ...smislu analize nakita kao dijela nošnje pokojnika nude izuzetan potencijal za razumijevanja i interpretacije djelića spektra onodobnog življenja ljudi i zajednica. Nakit se tijekom različitih povijesnih epoha predstavlja i kao narativ i kao narator, ne samo o osobama kojima je priložen u grob već i o široj zajednici kojoj su pokojnici pripadali. S izričito simboličkom reprezentacijom najčešće je odražavao status pojedinca i bio vrlo dobrim pokazateljem pripadnosti određenoj društvenoj skupini. Arheološka baština Nina obiljem i raznolikošću odražava neizbrisiv trag u njezinoj iznimno dugoj vremenskoj vertikali. Spektar raskošne nošnje i luksuznog nakita oplemenit će noviji nalazi iz položaja Klanice, koji su u analizi i interpretaciji predmet ove studije. Riječ je o fibuli s dva dugmeta na luku i igli s lukovičastom glavicom koje, tipološko-stilski i prostorno, obilježavaju široko rasprostranjen trend brojnih heterogenih zajednica, osobito u transjadranskim sudjelovanjima tijekom prvih faza kasnog brončanog doba kraja 13. i tijeka 12. stoljeća pr. Kr.
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Younger granites (post tectonic) are common throughout the Precambrian igneous/metamorphic terrain of Egypt and they played a significant role in the evolution of the Pan-African crust. The Gabal ...Igla Ahmar pluton comprises two magmatic suites: a calc-alkaline diorite/quartz diorite-granodiorite suite and an aluminous monzogranite-granophyre suite. The calc-alkaline rocks have low K
2O, relatively low LREE and display fractionated HREE (
Tb
Yb
n
= 1.3–2.2
). They appear to represent a suite of andean-type intrusives emplaced in an active continental margin. The monzogranites are metalummous to slightly peralummous, highly differentiated I-type granitoids apparently representing a post-collision phase of intrusion.
Three distinct petrogenetic models for magma genesis are suggested to explain the petrological, major, trace and REE element variations in these magmatic suites:
1.
i) The calc-alkaline quartz diorite was derived by partial melting of garnet amphibolite leaving a homblende-rich residue.
2.
ii) The monzogranites evolved by 75–85% crystal fractionation of the quartz diorite melt. The crystallization took place at depth from a water saturated magma of minimum melt composition. After a further interval, the granitic melt was emplaced at shallow crustal levels at pressures of 1–3 kbar.
3.
iii) Simple mixing of quartz dioritic and granitic melts as two end-member components could explain the origin of the granodiorite.
This model is consistent with the field petrographical and chemical characteristics of the granodiorite. At a late stage of monzogranite crystallization, the water contents in residual, intercrystalline melt became sufficiently high to promote the development of eutectoid intergrowths of quartz and feldspar to form the granophyre.
Les younger granites (post tectoniques) sont abondants dans tous les terrains ignés et métamorphiques d'Egypte et ont joué un rôle important dans l'évolution de la croûte pan-africaine. Le pluton de Gabal Igla Ahmar comprend deux suites magmatiques: une suite calco-alkaline diorite/diorite quartzique/granodiorte et une suite alumineuse monzogranite/granophyre. Les ruches calco-alcahnes ont des teneurs faibles en K
2O, relativement faibles en terres rares, dont les termes lourds sont fractionnés (
Tb
Yb
n
= 1.3–2.2
). Elles semblent représenter une suite d'intrusions de type andin mises en place dans une mange continentale active. Les monzogranites sont métalumineux à faiblement hyperalumineux, fortement différenciés et de type I. Ils représentent une phase d'intrusions post-collisionnelles.
Trois modèles pétrogénétiques distints ont été suggérés pour la genèse de ces magmas afin d'expliquer les variations observées en éléments majeurs et en traces (y compris les terres rares):
1.
i) les diorites quartziques calco-alcalines dérivent par fusion partielle d'une amphibolite à grenat, laissant un résidu riche en hornblende.
2.
ii) Les monzogranites se forment par cristallisation fractionnée (
F = 75–85%) à partir du magma dioritique. La cristallisation se serait déroulée en profondeur à partir d'un magma saturé en eau et de composition eutecticale. Le magma granitique se serait ensuite mis en place à faible profondeur (pression de 1 à 3 kbar).
3.
iii) Un mélange simple entre les magmas dioritique et granitique comme termes extrêmes expliquerait l'origine des granodiorites.
Ce modèle est en accord aver les caractéristiques de terrain, pétrographique et chimiques des granodiorites. Lors d'une étape tardive de la cristallisation du monzogranite, la teneur en eau du magma résiduel intergranulaire devient suffisamment élevée que pour permettre le développement en condition eutectical d'intercroissances de quartz et de feldspath pour former les granophyres.
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