Nitric oxide profiles measured in situ during the Globus '85 campaign

Nitric oxide profiles obtained from three flights of chemiluminescent instruments during the Globus '85 campaign held in France in the autumn of 1985 are reported. When the profile obtained in the early morning of 20 September is compared with the flight made the previous afternoon, an average morning to midday NO ratio of 0.7 for the region between 26 and 33 km is obtained. This value is in good agreement with theoretical studies involving the photolysis of N₂O₅ and the establishment of the NO₂–NO equilibrium.     

Carbon dioxide emissions in a methane economy

Increasing reliance on natural gas (methane) to meet global energy demands holds implications for atmospheric CO₂ concentrations. Analysis of these implications is presented, based on a logistic substitution model viewing energy technologies like biological species invading an econiche and substituting in case of superiority for existing species. This model suggests gas will become the dominant energy source and remain so for 50 years, peaking near 70 percent of world supply. Two scenarios of energy demand are explored, one holding per capita consumption at current levels, the second raising the global average in the year 2100 to the current U.S. level. In the first (efficiency) scenario concentrations peak about 450 ppm, while in the second (long wave) they near 600 ppm. Although projected CO₂ concentrations in a methane economy are low in relation to other scenarios, the projections confirm that global climate warming is likely to be a major planetary concern throughout the twenty-first century. A second finding is that data on past growth of world per capita energy consumption group neatly into two pulses consistent with longwave theories in economics.     

Late Quaternary record of sea-level changes in the Antarctic

The Late Quaternary sediment sequence of the continental margin in the eastern Weddell Sea is well suited for palaeoenvironmental reconstructions. Two cores from the upper slope, which contain the sedimentary record of the last 300 ky, have been sedimentologically investigated. Age models are based on lithostratigraphy and are correlated with the stable isotope record. As a result of a detailed analysis of the clay mineral composition, grain size distributions and structures, this sedimentary record provides the first marine evidence that the Antarctic ice sheet extended to the shelf edge during the last glacial.The variations in volume and size of the ice sheet were also simulated in numerical models. Changes in accumulation rate and ice temperature are of some importance, but the model revealed that fluctuations are primarily driven by changes in eustatic sea-level and that the ice edge extended to the shelf edge during the last glacial maximum. This causal relationship implies that the maximum ice extension strongly depends on the magnitude and duration of the sea-level depression during a glacial period. The results of the sedimentological investigations and of the numerical models show that the Antarctic ice sheet follows glacial events in the northern hemisphere by teleconnections of sea level. Correspondence to: H. Grobe     

Polarized single-crystal FTIR-spectra of natural staurolite

Polarized infrared absorption spectra of thin single-crystal slabs parallel to (010) and (001) of a staurolite from Pizzo Forno, Ticino, with analyzed composition (Fe_2.9Mg_0.9Zn_0.1Mn_0.1)Al_17.5Ti_0.1(Si_7.7Al_0.3)O₄₈H₃ have been measured in the range of 3000–4000 cm^?1. From the pleochroitic behaviour of the OH-vibrations three groups of bands can be distinguished: the bands of group I, a strong band at 3445 cm^?1 plus a weak shoulder at 3358 cm^?1, and the bands of group II, a weak band centered at 3677 cm^?1 plus a shoulder at 3635 cm^?1, are assigned to the H1 and H2 protons, respectively. The bands of group III, a weak band at 3577 cm^?1 plus a shoulder, cannot be interpreted on the basis of the proton positions known so far. We assign them to an additional proton H3, which is bonded to O1 and shows a bifurcated hydrogen bridge to two O5 in a vacant T2 site.     

Determinants of environmental action with regard to climatic change

The study of human dimensions of global climatic change is still in the initial stage of development. Several attempts have been undertaken to define sensible research strategies in the field but until now relatively little empirical work has been undertaken and there is a lack of sound theoretical arguments. The present paper presents a theory-based empirical study of determinants influencing the probability that somebody takes climate-relevant environmental action. Important methodological differences between current models of climate dynamics and models of human reality are discussed in order to build three models of climate-related environmental action. A model focussed on the information transfer from science to the public at large is compared with a model focussed on sociodemographic characteristics and with a model focussed on socio-cultural variables like interpersonal rules and social networks. The hypothesis that the latter model is strongly superior to the former ones is tested and confirmed. Some implications for interdisciplinary cooperation and for policy making are discussed.     

On the dynamics of photochemical smog over the Swiss Middleland — Results of the first POLLUMET field experiment

Summary The Swiss Middleland is a 300×50 km large plain embedded between the Jura, whose highest elevations are between 1000 and 2000m MSL, and the Alps, whose highest peaks are about 400m MSL. Because this plain is the main residence area of Switzerland with a great variety of emission sources, it is also a location with high photosmog concentrations during the summer months.Within the framework of the Swiss POLLUMET (Air Pollution and Meteorology) programme, an initial summer smog field experiment was carried out during July 1990 with the participation of different research groups from Switzerland and Germany. The measurements showed that the ozone concentrations within the atmospheric boundary layer were remarkably variable. The highest concentrations in the upper mixed layer varied between 100 and 130 ppb. The background ozone concentration in the upper atmospheric boundary layer increased from day to day. However, a clear indication of long-range transport could not be found. Remarkable local and regional concentration differences are not only based on the complex structure of the large emission sources (highways, urban plumes). They are also the result of the interaction of convectively driven motion systems like slope and valley winds and mountain-plain circulation.With 14 Figures     

The Kakun igneous cumulate magnetite deposit,SW Nigeria

Summary Field and mineralogical information concerning a Precambrian iron deposit in Kakun, southwestern Nigeria is presented and a genetic model is advanced. The Kakun deposit consists of titaniferous magnetite concentrated at the base of an amphibolite sheet within a large-scale banded metasediment-orthogneiss suite of Eburnean (ca. 2000 Ma) age. The suite is truncated by concordant and discordant Pan-African (ca. 600 Ma) granitic to dioritic intrusives including pegmatites and aplites. The ore-grade zone is marked by preferential concentration of early formed heavy minerals as well as cumulate and ophitic textures, while the host amphibolite exhibits preferred mafic mineral alignment and triple junction mosaic of its felsic mineral matrix. These relationships are here explained in a two-stage model comprising an Eburnean synkinematic magmatic phase and a Pan-African deformation-metamorphic phase. The first stage involved the intrusion of a gabbroic magma as a sill into pre-existing rocks under high grade metamorphic conditions; mineral segregation of the sill into an ore-rich base by crystal settling during consolidation; followed by a post-consolidation pulse of anorthosite melt injection into the ore zone. The second stage occurred under conditions of medium grade metamorphism and heterogeneous deformation. Competence, difference and localised access of water during this stage led to preferential shearing and amphibolitisation of the ore-poor upper part of the sill.

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Die magmatische Cumulat-Magnetit Lagerstatte von Kakun, SW Nigeria

Zusammenfassung Es werden feldgeologische und mineralogische Informationen von einer präkambrischen Eisenlagerstätte in Südwest-Nigeria präsentiert, und ein genetisches Model vorgestellt. Die Kakun Lagerstätte stellt eine Ti-Magnetit Mineralisation dar, die an der Basis einer Amphibolitabfolge konzentriert ist. Die Amphibolite gehören zu einer im Groß-Maßstab gebänderten Metasediment-Orthogneis Serie von Eburnean-Alter (ca. 2000 m.y.). Diese Serie wird von konkordanten und diskordanten granitischen bis granodioritischen Intrusionen und inkludierten Pegmatiten und Apliten (ca. 600 m.y.) durchbrochen. Die vererzte Zone ist durch Konzentration von frühgebildeten Schweremineralien, Cumulat- und ophitischen Texturen gekennzeichnet; die Amphibolitabfolge zeigt Einregelung der mafischen Mineralkomponenten, und ein tripple junction Mosaik der felsischen Gemengteile. Diese Charakteristika der Erz-Zone und der Amphibolite werden mit einem zweiphasigen Model erklärt: eine Eburnean synkinematische, magmatische Phase und eine Pan-Afrikanische, deformative metamorphe Phase. Die erste Phase umfaßt die Intrusion eines gabbroischen Sills unter hochgradigen Metamorphosebedingungen, Mineralsegregation innerhalb des Sills in eine erzreiche Basis, verursacht durch Kristall-Absinken während der Konsolidierung, und schließlich die Injektion eines anorthositischen Magmenpulses in die Erzzone im post-Konsolidierungsstadium. Die zweite Phase hat unter mittelgradigen Metamorphosebedingungen und heterogener Deformation stattgefunden. Kompentenz-Unterschiede und das stellenweise Eindringen von Wasser hat in dieser Phase zu Scherung und Amphibolitisierung des erzarmen, hangenden Anteils des Sills geführt.

     

Pyroxene chemistry and evolution of alkali basaltic rocks from Burgenland and Styria,Austria

Summary The mineral chemistry of several Pliocene alkali basaltic rocks from Burgenland and Styria (Eastern Austria) have been investigated in order to determine the evolution path of the basalt magmas prior to eruption. With their wide range of substitutions, clinopyroxenes provide the best records of the evolution history of rocks. Pyroxene phenocrysts of the investigated basalts show both concentric and sector zoning. The investigation of sector zoned crystals shows, that not only Ti, Al and Fe contents are different in different sectors but there can be significant differences also in their Cr content. This fact apparently suggests that the distribution of Cr between clinopyroxene and melt could be influenced by crystallization kinetics.The depth of crystallization and differentiation of the basalts can be estimated from Ti and Al contents of clinopyroxene phenocrysts. From a combination of data on clinopyroxene composition, compatible trace element contents and mg-values of the rocks, it is concluded, that the alkali basalts of Pauliberg and Steinberg underwent slight olivine and clinopyroxene fractionation in shallow magma chambers prior to eruption, while the nephelinite of Stradnerkogel evolved mainly through clinopyroxene fractionation under high pressure conditions, probably in the upper mantle.

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Chemie der Pyroxene und Entwicklung von Alkalibasalten aus dem Burgenland und der Steiermark, Österreich

Zusammenfassung Einige pliozäne alkalibasaltische Gesteine aus dem Burgenland und der Steiermark wurden mineral-chemisch untersucht, um Aufschluß über ihre Evolution vor der Eruption zu erhalten. Klinopyroxene mit ihren vielfältigen Subtitutionsmöglichkeiten erlauben am besten eine Abschätzung der Evolution der Basalte. Pyroxen-Einsprenglinge der Basalte zeigen sowohl konzentrischen als auch sektoralen Zonarbau. Die von uns untersuchten Einsprenglinge zeigen in den verschiedenen Sektoren nicht nur unterschiedliche Gehalte an Ti, Al und Fe, sondern vielfach auch unterschiedliche Cr-Gehalte. Dies macht es wahrscheinlich, daß die Verteilung von Cr zwischen Klinopyroxen und Schmelze von der Kristallisations-Kinetik beeinflußt wird.Die Tiefe in der die Basalte kristallisierten und differenzierten kann von den Ti- und Al-Gehalten der Klinopyroxen- Einsprenglinge abgeschätzt werden. Die Zusammensetzung der Klinopyroxene im Verein mit den Gehalten an kompatiblen Spurenelementen und denmg-Werten der Gesteine erlauben den Schluß, daß die Alkalibasalte von Pauliberg und Steinberg vor ihrer Eruption eine geringfügige Olivinund Klinopyroxen-Fraktionierung in einer seichten Magmakammer erlebten. Der Nephelinit vorn Stradnerkogel hingegen erfuhr hauptsächlich eine Klinopyroxen Fraktionierung unter Hochdruck-Bedingungen, möglicherweise im oberen Erdmantel.

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With 8 Figures