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Volume :19 Issue : 2 1992
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Relationships between shear zones and mineralization in the Nubian Shield of northeast Sudan
Auther : DAVID C. ALMOND AND ABDULAZIZ A. OSMAN
Department of Geology, University of Kuwait, P.O. Box 5965, Safat 13060, Kuwait
ABSTRACT
The Proterozoic rocks of NE Sudan form part of the Arabian-Nubian Shield. Island arc activity began in this region before 800 Ma, with accretion of the arcs to an older African continental nucleus around 700 Ma. Cratonization and the emplacement of post-tectonic igneous rocks continued until about 500 Ma. Ductile shear along strike-slip zones was an important mechanism of deformation in the Shield and generated a network of broad shear zones. Early shear zones formed before or during accretion contain ophiolite lenses and folds. Early mineralization with Cu, Zn, Fe and Ba was associated with island arc volcanicity and its distribution is to some extent related to the early shear zones whereas subsequent shear zones are not known to contain such deposits. Gold mineralization occurs within both early and late shear zones, and there is a potential for occurrence of Sn-W mineralization associated with post-tectonic intrusions emplaced into the shear zones. The shear zone network and spatially associated Late Proterozoic intrusions are thus primary guides to mineralization. Comparison with some of the young island arcs of SE Asia provides a useful analogy with the pre-accretional development of the Arabian-Nubian Shield. This comparison sheds light upon the tectonic roles of early shear zones, the mechanisms of emplacement of ophiolite lenses, and the absence of S-type granites in this part of the Shield. It also raises questions on the apparent absence of porphyry copper deposits from the Shield.