Abstract
Nusab El Balgum mass complex represents one of the alkaline igneous activities in the south Western Desert of Egypt. Petrographic investigations defined some different rock types in south of the complex represented by alkaline volcanics (pyroclastics [rhyolitic crystal tuffs], spherulitic rhyolites, alkaline rhyolite dykes), sub-volcanic peralkaline granites and structurally controlled mylonitic volcanoclastics. These rocks recorded significant concentrations in terms of the two radioactive elements Th and eU, which displayed considerable spatial variations, especially within the peralkaline granites. The abundance of Th and eU is mainly related to favorable combination of structural and pos-magmatic hydrothermal conditions. Paleomagnetic results give well-defined stable remanent magnetization directions of reliable VGP positions, which are presented and discussed in the context of the African APWP. Rock types, magnetization directions and VGP positions with the corresponding ages are as follows: 1) Rhyolitic crystal tuffs; D/I = 340.0°/—19.4°, α95 = 6.8°; VGP Lat./Long. = 51.4°N/240.5°E, A95 = 5.9° (Late Triassic). 2) Spherulitic rhyolites; D/I = 346.7°/—6.6°, α95 = 3.5°; VGP Lat./Long. = 60.4°N/237.0°E, A95 = 3.0° (Late Triassic/Early Jurassic). 3) Alkaline rhyolite dykes; D/I = 341.3°/16.7°, α95 = 5.4°; VGP Lat./Long. = 67.0°N/262.8°E, A95 = 4.2<span style="fo
Highlights
Volcanism is a major contributor to the formation of important uranium (U) deposits [1]
Isothermal Remanent Magnetization Progressive direct magnetic fields up to 1.0 T were applied to representative samples from the different rock types in order to determine the isothermal remanent magnetization (IRM) acquisition patterns
Representative sample from the rhyolitic crystal tuffs showed an initial increase in IRM acquisition and acquired ~80% of the maximum IRM at field of 0.2 T, but did not saturate by the maximum field applied (Figure 11(a))
Summary
Volcanism is a major contributor to the formation of important uranium (U) deposits [1]. The International Atomic Energy Agency (IAEA) tabulation lists 100 volcanogenic U deposits in 20 countries, which amount to 6 percent of the known global resources [2]. Felsic volcanic rocks proximal to U deposits typically contain U concentrations in excess of 10 ppm. Enriched U contents are characteristics of rocks with aluminous and alkaline affinities [3]. In south of Egypt, the alkaline igneous activity can be OPEN ACCESS GM.
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