Edward Sabine,ein großer Geophysiker des 19. Jahrhunderts

Zusammenfassung Das soeben beendete dritte Internationale Geophysikalische Jahr, bisheriger Höhepunkt in der Erforschung der uns zugänglichen Hydro- und Atmosphäre der Erde, führt notwendigerweise zu der Frage nach der Vorgeschichte unserer heutigen geophysikalischen Erkenntnisse und Arbeitsmethoden. Als repräsentativ für die erste Hälfte des 19. Jahrhunderts dürfen wir den englischen Forscher Sir Edward Sabine ansehen, der als erster moderner All-round-Geophysiker gravimetrisch in den Tropen und in der Arktis tätig war, besonders hochgeschätzt von A. v. Humboldt, dessen erdmagnetisches Werk er ausbaute; auch durch wertvolle ozeanographische und meteorologische Untersuchungen rühmlich bekannt.

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Edward Sabine, a great geophysicist of the nineteenth century

Summary The past third International Geophysical Year, up to now culminating point in the research for the hydrosphere and the atmosphere of the earth, makes us, necessarily, desirous to learn something about the early development of to-day's geophysical knowledge and working methods. As representative of the first half of the nineteenth century we may regard the English explorer and scientist Sir Edward Sabine, who as the first all-round geophysicist in the modern sense of the word carried out gravimetric measurements in the tropics and in the arctic regions. Alexander von Humboldt whose geomagnetic work he has been developing, held him in high esteem; besides, he is famous for his research work in the oceanographic and meteorological fields.

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Edward Sabine, grand géophysicien au dix-neuvième siècle

Résumé La troisième Année géophysique internationale écoulée, jusqu'ici point culminant des recherches sur l'hydrosphère et l'atmosphère de la terre, fait nécessairement naître en nous le désir d'étendre nos connaissances du développement primaire de la science et des méthodes de travail de la géophysique actuelle. Nous sommes tenus de considérer l'explorateur et le savant anglais Sir Edward Sabine comme le représentant de la première moitié du dix-neuvième siècle. Il fut le premier à effectuer des mesures gravimétriques dans les tropiques et dans les zones arctiques en qualité de géophysicien universel au sens moderne de ce mot. Il jouissait de l'estime profond d'Alexander von Humboldt, dont il a développé l'uvre géomagnétique. De plus, Sabine est fameux pour ses études dans les domaines de l'océanographie et de la météorologie.

     

Ist der Fischfluß-Cañon in Südwestafrika (Namibia) durch eine Grabenstruktur vorgezeichnet?

Zusammenfassung Der Cañon, in welchem der Fischfluß verläuft, folgt einer Bruchstruktur, die kein einfacher Graben ist, sondern von Aufschiebungen statt von Abschiebungen begrenzt wird. Hinzu kommen auf beiden Seiten des Flußverlaufs große Flexurfalten, vermutlich durchgepauste Aufschiebungen. Das hat zur Bildung eines Rampgrabens geführt. Diese Einengungstektonik paßt nicht ohne weiteres zu der Vorstellung eines zerdrifteten Gondwana-Landes, das im Sinne von A.Wegener in Einzelkontinente zerrissen ist.

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The canyon of the Fischfluss follows a fracture zone, which is not a normal graben as often is supposed. The so called Fisch River Graben has been formed by overtthrusting fractures instead of normal faults on both sides of the graben. Besides there exist folding structures (flexure-folds) on both sides of the graben. Theses compression structures have formed a Ramp-Graben, which was firstly discribed by B.Willis (1928). Theses compression structures do not agree with A.Wegeners hypothesis of the old Gondwana continents destruction by drifting and tension, by which the old African block broke up into the African and the American block.

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Résumé Le cañon du Fischfluss suit une zone de fractures qui n'est pas un graben normal ainsi qu'on l'a souvent supposé; elle est limitée, non par des failles d'affaissement, mais par des chevauchements. En outre viennent, sur les deux côtés du cours de la rivière, de grands plis-flexures, espéces de chevauchements refoulant le scole cristallin sous les sédiments plissés. Il s'agit d'un «Rampgraben», (= fossé poussé) qui est le résultat d'une tectonique de resserrement. Celle-ci ne répond pas à l'idée d'un continent de Gondwana qui, fissuré et dérivant, s'est subdivisé en continents isolés, selon l'hypothèse de A.Wegener.

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Orbicular lamprophyre from Vestby,southeast Norway

A pyroxene-amphibole lamprophyre of Permian age intersecting Precambrian gneiss, etc., contains domains of pyroxenite breccia and of closely packed single- and multi-shelled orbicules. The multi-shelled orbicules have inner medium-grained, radial and outer aphanitic, laminated shells. The outer shells are explained as having formed by direct precipitation from the magma. The inner shells most probably underwent a recrystallization at magmatic temperatures, their original composition being like that of the outer shells. Shells of single-shelled orbicules are similar to the inner shell of the multi-shelled ones and contain relicts of aphanitic, laminated material.The cores, composed of Permian pyroxenite or more rarely Precambrian pegmatite quartz, were originally formed by volcanic fragmentation of the country rock.     

Geochemical evidence for mixing of magmatic fluids with seawater,Nisyros hydrothermal system,Greece

The chemical and isotopic compositions (δD_H2O, δ¹⁸O_H2O, δ¹⁸O_CO2, δ¹³C_CO2, δ³⁴S, and He/N₂ and He/Ar ratios) of fumarolic gases from Nisyros, Greece, indicate that both arc-type magmatic water and local seawater feed the hydrothermal system. Isotopic composition of the deep fluid is estimated to be +4.9±0.5‰ for δ¹⁸O and ?11±5‰ for δD corresponding to a magmatic water fraction of 0.7. Interpretation of the stable water isotopes was based on liquid–vapor separation conditions obtained through gas geothermometry. The H₂–Ar, H₂–N₂, and H₂–H₂O geothermometers suggest reservoir temperatures of 345±15 °C, in agreement with temperatures measured in deep geothermal wells, whereas a vapor/liquid separation temperature of 260±30 °C is indicated by gas equilibria in the H₂O–H₂–CO₂–CO–CH₄ system. The largest magmatic inputs seem to occur below the Stephanos–Polybotes Micros crater, whereas the marginal fumarolic areas of Phlegeton–Polybotes Megalos craters receive a smaller contribution of magmatic gases.     

Fluid–rock interaction in autoliths of agpaitic nepheline syenites in the Ilímaussaq intrusion, South Greenland

Within the 1.16 Ga old Ilímaussaq intrusion, up to 700 m large autoliths occur in one stratigraphic unit of the layered floor series of agpaitic nepheline syenites (kakortokites). These autoliths consist of two different rock types: augite syenite and naujaite (agpaitic nepheline syenite). All three rock types show a number of alteration features related to the entrapment of the autoliths in the kakortokite magma caused by the interaction with a fluid phase.

In the kakortokites, the oxidation of primary arfvedsonite to aegirine and fluorite is restricted to the close proximity to the autoliths. Close to the surrounding kakortokite, the primary mafic phases of the augite syenites (augite, fayalite, Fe–Ti oxides) are completely replaced by arfvedsonite, aenigmatite, biotite, aegirine and fluorite. The decomposition of primary hastingsite to spectacular aegirine–augite–nepheline–aenigmatite symplectites can be observed up to several meters inside the autoliths. Additionally, fluorite formed at grain boundaries of primary nepheline. In the naujaite autoliths, primary arfvedsonite is replaced by aegirine–biotite intergrowths and abundant aenigmatite is occasionally replaced by Ti-rich aegirine and Fe–Ti oxides.

The mineral reactions in the autoliths are used to decipher details of the late to post-magmatic processes in a peralkaline syenitic intrusion. Mineral equilibria record an evolution governed by falling temperature (620 to ca. 500 °C) and increasing relative oxygen fugacity from FMQ + 1 to above FMQ + 4. Quantification of the observed mineral reactions reveals the infiltration of the autoliths with an oxidizing fluid phase rich in Na and F and minor addition of K. Volatiles (H and F) and in some cases also Fe, Ti and Ca (± Mg) released from primary autolith phases were mainly just relocated within the autoliths.     

Land degradation is not a necessary outcome of communal pastoralism in arid Namibia

In Otjimbingwe, a region of arid south-central Namibia, human population densities are high and these communal pastoralists own large numbers of livestock. Such situations are commonly perceived to lead to the ‘tragedy of the commons'. This region lends itself to a comparison of the effects of communal and commercial farming (with private land ownership) because the communal area is completely surrounded by commercial farms. In spite of far higher stocking densities on the communal areas and the absence of an overall grazing strategy, we found no evidence of the ‘tragedy of the commons' on Otjimbingwe. Indeed, the communal areas did not differ in a number of soil and vegetation parameters from the commercial farms. These results point both to the resilience of arid environments to high stocking levels and the over-riding influence of abiotic variables on environmental quality.     

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O: corrections and additional experimental data

Melting relationships in the system K₂O-CaO-Al₂O₃-SiO₂-H₂O have been reinvestigated using Schreinemakers analysis and hydrothermal experiments. The reaction sanidine+muscovite+zoisite+quartz+vapor =melt has been bracketed at 10, 15, and 20 kbars and 670–680, 680–690, and 690–700° C, respectively and it marks the lowest solidus temperatures in the system investigated.Below 10 kbars, experimental data on the beginning of melting in zoisite- or muscovite-bearing anorthite+sanidine assemblages have been obtained, which are not showing any differences and therefore point to melt compositions close to the feldspar-quartz join.