Die elektrische Ladung eines Flugzeuges bei Vereisung in Quellwolken

Zusammenfassung Es wurde die Aufladung eines Flugzeuges beim Flug durch Quellwolken gemessen. Es ergab sich, dass beim Einflug in die Wolke und bei einsetzender Vereisung das Flugzeug stark negativ aufgeladen wurde, nach dem Abtauen blieb eine kleine positive Restladung zurück. Das maximale Potential des Flugzeugs betrug ca. 35 KV/m. Das Vorzeichen der Aufladung steht im Einklang mit den vonWorkman im Laboratorium ermittelten Werten.

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Summary The charge of an airplane flying through thunderclouds has been measured. It was stated that icing caused a heavy negative charging of the plane, whilst after deicing a weak positive charge remained. The maximum amount of the potential was found to be about 35 KV/m, limited by spray discharging. The sign of the charge agrees with the tests, made byWorkman in laboratory.

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Résumé On a remarqué qu'un avion était chargé négativement lors de son entrée dans une nuage orageuse et cela par suite de la formation de glace. Après que la glace ait disparu on peut noter encore une petite charge positive. Le signe de la charge produite s'accorde avec les observations faites en laboratoire parWorkman.

     

Early Palaeozoic evolution of Libya: perspectives from Jabal Eghei with implications for hydrocarbon exploration in Al Kufrah Basin

This paper presents new stratigraphic and sedimentological data of the Ordovician, Silurian, and Mesozoic succession exposed on the western flank of Al Kufrah Basin. Field data (logged sections, photographs, palaeocurrent analyses) are presented from the Jabal Eghei region. This region lies ca. 200 km E of the closest stratigraphic tie point at Mourizidie on the eastern flank of the Murzuq Basin. The succession starts with the Hawaz Formation (Middle Ordovician) comprising >100 m of cross‐bedded and bioturbated sandstones that are interpreted as deposits of tidal currents in an open shelf setting. The contact between the Hawaz and Mamuniyat formations is an erosional unconformity, incised during advance of Late Ordovician ice sheets towards the NE. The Mamuniyat Formation comprises >150 m of massive and graded sandstones tentatively assigned to the Hirnantian, and contains an intraformational, soft‐sediment striated surface that is interpreted to record re‐advance of ice sheets over Jabal Eghei. The outcrop section suggests the sandstone would form an excellent reservoir in the subsurface. The Mamuniyat Formation is overlain by the Tanezzuft Formation (uppermost Ordovician–lowermost Silurian). This includes sandy limestone/calcareous sandstone, a Planolites horizon, and then 50 m of interbedded shale, silt and fine‐grained, graded and hummocky cross‐stratified sandstone recording deposition from both shallow marine turbidity currents and storm flows. A striated pavement in the lower part of this sequence is overlain by calcareous lonestone‐bearing intervals (interpreted as ice‐rafted debris). These features testify to late phases of glacial advance probably post‐dating the regional Hirnantian glacial maximum. The basal Silurian ‘hot shale’ facies is not developed in this area, probably because late glacial advance suppressed the preservation of organic matter. The upper part of the Tanezzuft Formation is truncated by an unconformity above which palaeosol‐bearing fluvial deposits (undifferentiated Mesozoic) occur.     

Palaeotethys-related sediments of the Karaburun Peninsula,western Turkey: constraints on provenance and stratigraphy from detrital zircon geochronology

International Journal of Earth Sciences - Detrital zircon U–Pb geochronology of 15 Late Palaeozoic to Early Mesozoic siliciclastic sandstones from the Karaburun Peninsula in western Turkey...     

U–Pb LA-SF-ICP-MS zircon geochronology of the Serbo-Macedonian Massif, Greece: palaeotectonic constraints for Gondwana-derived terranes in the Eastern Mediterranean

The Pirgadikia Terrane in northern Greece forms tectonic inliers within the Vardar suture zone bordering the Serbo-Macedonian Massif to the southwest. It comprises Cadomian basement rocks of volcanic-arc origin and very mature quartz-rich metasedimentary rocks. U–Pb laser ablation sector-field inductively-coupled plasma mass spectrometry analyses of detrital zircons from the latter reveal a marked input from a Cadomian–Pan-African source with minor contribution from Mesoproterozoic, Palaeoproterozoic and Archaean sources. The metasedimentary rocks are correlated with Ordovician overlap sequences at the northern margin of Gondwana on the basis of their maturity and zircon age spectra. The Pirgadikia Terrane can be best interpreted as a peri-Gondwana terrane of Avalonian origin, which was situated close to the Cadomian terranes in the Late Neoproterozoic–Early Palaeozoic, very much like the Istanbul Terrane. The second unit investigated is the Vertiskos Terrane, which constitutes the major part of the Serbo-Macedonian Massif in Greece. It comprises predominantly igneous rocks of Silurian age and minor metasedimentary rocks of unknown age and provenance. U–Pb analyses of detrital zircons from a garnetiferous mica schist of the Vertiskos Terrane indicate derivation from 550 to 1,150 Ma-old source rocks with a major Cadomian peak. This, combined with minor input of >1,950 Ma-old zircons and the absence of ages between ca. 1.2 and 1.7 Ga suggests a NW Africa source. The protolith age of the garnetiferous mica schist is presumably Early Ordovician. One sample of garnet-bearing biotite gneiss, interpreted as meta-igneous rock, comprises predominantly subhedral zircons of igneous origin with late Middle Ordovician to Silurian ages. We suggest that the rock association of the Vertiskos Terrane is part of an ancient active-margin succession of the Hun superterrane, comparable to successions of the Austro- and Intra-Alpine Terranes. The new data of this study provide evidence of occurrences of Avalonia- and Armorica-derived terranes in the Eastern Mediterranean and moreover help to clarify palaeogeographic reconstructions for the peri-Gondwana realm in the Early Palaeozoic.     

Natural and synthetic leucites studied by solid state 29-Si and 27-Al NMR and 57-Fe Mossbauer spectroscopy

The 29-Si NMR spectra of natural and synthetic leucites (KAlSi₂O₆) are found to contain a number of resonances which are interpreted in terms of the known structure of low-temperature (tetragonal) leucite. Computer simulation of the spectra suggests that the most distorted tetrahedral lattice site T ₁ contains a higher proportion of Al than the other two tetrahedral sites. The occurrence of some ordering of the tetrahedral Si and Al in leucite is confirmed by Mossbauer studies of synthetic iron-containing leucites, including the fully ferric end-member KFeSi₂O₆, in which the three tetrahedral sites can be distinguished. On replacement of about half this Fe by Al, the most distorted of these sites is lost from the spectrum, reflecting the preference of Al for this site. A linear relationship is found between the unit cell dimensions of all these leucites and their iron content.     

Rutile chemistry and thermometry as provenance indicator: An example from Chios Island,Greece

In the present study we focused on detrital rutile separated from 12 psammitic samples that belong to three different sedimentary successions (Carboniferous, Permo-Carboniferous, Permo-Triassic) occurring on Chios Island, Greece. The Ti, Cr, Al, Fe, Nb, Zr, Si, and V contents of the rutiles were obtained by electron-microprobe analyses to trace their provenance.The Cr and Nb concentrations of the analysed rutile grains show a wide range and indicate that this mineral in the Carboniferous succession is mainly derived from metamafic rocks, whereas in the Permo-Carboniferous and Permo-Triassic successions stem from a metapelitic source. The calculated formation temperatures using the Zr-in-rutile thermometer range from ca. 520 to 850 °C with “hotter” rutile being encountered in the Permo-Carboniferous and Permo-Triassic successions. This feature together with the rutile chemistry indicate a change in source-rock lithology through time, which could either reflect an increasing depth of erosion of an exhumed ‘Variscan’ nappe pile of heterogeneous composition in the hinterland or a change in the style of accretion and erosion of different terranes at the southern margin of Laurussia during the subduction of a branch of the Palaeotethys Ocean in the Late Palaeozoic. In general, this study underscores the importance of rutile chemistry and thermometry in quantitative single-mineral provenance analysis and in chemostratigraphic analysis of clastic sedimentary rocks.