Tectonic record and gold mineralization in the central part of the Neoproterozoic Keraf suture, Gabgaba district, NE Sudan
Résumé
The central Keraf suture recorded complex lithospheric-scale deformation associated with the formation of the Neoproterozoic Arabian-Nubian shield and hosts the WG03, Central Zone and UTM gold deposits, Gabgaba district, northeastern Sudan. This study aims at (i) unravelling the tectonic history recorded by the central Keraf suture and (ii) interpreting the spatial and genetic relationships between structural setting and gold mineralization. To this end, we coupled field petrographic observations and structural measurements made along a 50 km-long geological cross-section through the Gabgaba district with macroscopic and microscopic description of mineralized structures. The structural setting of the central Keraf suture is dominated by progressive deformation, from ductile D1a Keraf thrusting to ductile-brittle D1b sinistral shearing in a prolonged northwest-orientated convergence regime. A first mineralization event, leading to a minor gold endowment, relates to magmatic accretion pre-dating D1a Keraf suturing. The second gold episode is characterized by ore veining as a response to progressive late collisional D1b Keraf strike-slip shearing and may be classified as orogenic gold. Most of the gold budget of the Gabgaba district formed at this stage. In summary, the central Keraf suture exemplifies that the Arabian-Nubian shield contains significant polyphase gold mineralization along lithospheric-scale structures. These structures may record a complex tectonic evolution from magmatic accretion to collision, with a strong structural control on gold endowment.
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