Geology and mineral potential of Ethiopia: a note on geology and mineral map of Ethiopia

This work presents a geoscientific map and database for geology, mineral and energy resources of Ethiopia in a digital form at a scale of 1:2,000,000, compiled from several sources. The final result of the work has been recorded on CD-ROM in GIS format so that the map and the database could be available to users on a personal computer.Metallic resources (precious, rare, base and ferrous–ferroalloy metals) are widely related to the metamorphic meta-volcano-sedimentary belts and associated intrusives belonging to various terranes of the Arabian–Nubian Shield, accreted during the East and West Gondwana collision (Neoproterozoic, 900–500 Ma).Industrial minerals and rock resources occur in more diversified geological environments, including the Proterozoic basement rocks, the Late Paleozoic to Mesozoic sediments and recent (Cenozoic) volcanics and associated sediments.Energy resources (oil, coal, geothermal resources) are restricted to Phanerozoic basin sediments and Cenozoic volcanism and rifting areas.     

Premiers résultats d'une étude géophysique sur le flanc nord des glissements de Storegga (Norvège)

The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroît aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area. To cite this article: H. Nouzé et al., C. R. Geoscience 336 (2004).     

The age and origin of the deepest correlative structures recognized off canada and europe

Arcuate structures in the Avalon zone of Newfoundland and its geophysically inferred extension beneath the Grand Banks are either of Precambrian age, or represent probable reactivation of Precambrian structures. A similar arcuate pattern is followed by structures that can be traced geophysically between Iberia and Prance when they are restored to their pre-Mesozoic relative position. Although the Hercynian orogeny has increased their curvature within Iberia, the arcuate structures did exist in Precambrian time. The Avalonian and Iberian structures show good correlation on pre-Mesozoic paleogeographic reconstructions of the north Atlantic, but the gravity and magnetic expression of the arcs indicates that they have a higher mafic content on the Canadian margin. With evidence for Precambrian volcanism in Newfoundland and Precambrian tension in Iberia, it is possible that both subduction and basin-and-range type rifting occurred in different parts of that Precambrian craton, Mesozoic rifting of it having taken place near the boundary between the two regimes.     

The cluster-ridge pattern of mantled gneiss domes in eastern Finland: Evidence for large-scale gravitational instability of the Proterozoic crust

The Karelian mantled gneiss domes of Finland occur within a band some 100 km wide and at least 400 km long, bordering the Archean basement. Previous field analysis has shown that domes were emplaced during regional deformation. Domes tend to cluster along nine ridges oriented NNE-SSW to NE-SW. Data concerning dome size, shape and distribution are presented. Good correlations are found between shape, orientation and spacing of domes and the regional foliation. The spacing between the ridges is consistent and varies from 27 to 42 km according to their orientation but the dome spacing along the ridges is strongly modified by the regional deformation. The comparison with theoretical and experimental models allows an interpretation in terms of diapiric periodicity. The disposition in ridges could be a boundary effect controlled by the shape of the Archean-Karelian interface. The conservation of the cluster-ridge pattern, in spite of the regional deformation, tends to prove the predominance of gravitational instability over regional shortening in the tectonic evolution of the Karelides.     

Airborne measurements of savanna fire emissions and the regional distributio of pyrogenic pollutants over Western Africa

We measured CO₂, CO, CH₄, H₂, and NO₂ in air masses polluted by savanna fires over Côte d'Ivoire, western Africa. Elevated concentrations of these trace gases were found in fire plumes and also in extensive haze layers. Trace gas mixing ratios ranged as high as 605 ppmv for CO₂, 14.8 ppmv for CO, 2.7 ppmv for CH₄, 4.2 ppmv for H₂, and 25 ppbv for NO₂. We compare our emission ratios to those obtained in previous field and laboratory studies. The emission ratios, expressed as an average and as a range or as an average only, were: dCO/dCO₂ 5.3×10^–2 (3–18×10^–2); dCH₄/dCO 5.3×10^–2; dH₂/dCO 2.4×10^–1 and dNO₂/dCO₂ 1.8×10^–4 (1.5–2.2×10^–4). The values found match those found during similar measurements, though our results point to rather vigorous burning in the savanna of western Africa.     

Spectra of accretion discs around white dwarfs

We present the spectra of accretion discs around white dwarfs calculated with an improved and updated version of Shaviv and Wehrse [Shaviv, G., Wehrse, R., 1991. A&A 251, 117] model. The new version includes line opacities and convective energy transport and can be used to calculate the spectra of hot discs in bright systems (nova-like variables or dwarf novae in outburst) as well as the spectra of cold accretion discs in quiescent dwarf novae.