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- Title
Neoproterozoic U‐Th‐REE‐bearing Pegmatites in Wadi Ibib, South Eastern Desert, Egypt: Structural and Geochemical Measures for a Syn‐Tectonic Anatectic Model of Formation.
- Abstract
The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone (HSZ), which is a high strain zone evolved during the late stages of the Pan‐African orogeny, likely as a tectonic escape structure. Amphibolite facies pelitic metasedimentary windows crop out in the axial parts of the HSZ and are noticeably associated with numerous N‐trending pegmatite dikes. Whole‐rock geochemistry of the pegmatites reveals a peraluminous (S‐type) affinity, with low K/Rb ratios and elevated concentrations of U, Th, REE, Rb, Li, Cs, Y, Nb and Ta. Structurally, the pegmatite sets intrude along the shear plane of the HSZ, corresponding to the regional N‐trending tectonic fabrics, such as axial planar foliation and dextral‐shearing in the metasedimentary host rock. Field relationships, including structural context, coupled with geochemical characteristics of the Wadi Ibib pegmatites, do not support their formation as a complementary part of evolved granitic magmas. Space‐localized decompression‐induced partial melting of peraluminous garnet‐bearing metapelites was alternatively the underlying process for formation of these pegmatites. Such decompression was associated with regional escape tectonics and stress axes permutations during the late deformation stage (D3) in the evolution of the south Eastern Desert terrane, due to end‐orogeny system pressure‐release.
- Subjects
EGYPT; PEGMATITES; ALKALI metals; SHEAR zones; DESERTS; GEOCHEMISTRY; AMPHIBOLITES
- Publication
Acta Geologica Sinica (English Edition), 2021, Vol 95, Issue 6, p2045
- ISSN
1000-9515
- Publication type
Article
- DOI
10.1111/1755-6724.14713