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Structural geology of Abu Sari auriferous veins in Northern Sudan: an example for shear-hosted mesothermal gold mineralization in greenstone belts

Atalar, Erdem
The gold mineralized quartz vein system has been discovered within the Proterozoic Nubian Shield in the Sudan Northern State Dongola city, Abu Sari Region at North East Africa. Northern Sudan forms part of the Proterozoic Nubian Shield and consists of mainly accreted oceanic terranes that were sutured to Gondwana during the Pan-African orogeny  during approximately 810 to 580 My time interval. Mesothermal gold mineralization formed towards the end of ~550 to 600 my interval, during collisional deformation and large-scale strike-slip faulting along the east African margin. Gold mineralization occurs across a wide area of quartz veining (at least 7 x 10 km) near the village of Abu Sari, approximately 650 km north of Khartoum. Rocks exposed in the Abu Sari area consist mainly of deformed and metamorphosed greenschist-facies greywackes, and intruding small granodiorite bodies, felsic and mafic dikes. Mineralized quartz veins are controlled by strike-slip faulting with kinematic indicators occurring along their contacts with the host rock. Understanding the general behaviour of the fault system and the quartz veining will help to understand the invisible continuation of the mineralized quartz veins, and to determine areas of the bending and turning points of the veins. To tackle these questions 1:200-scale wall mapping of the quartz veins is done in the 235 meters level of the open pits of the gold mine. The surface level is 250 meters and the drilling data available in the 235 meters level help to understand the relationship between the mineralization and the structures. The relationships between geological structures in the study area suggest that the region has suffered from five distinct phases of deformation. The first phase is attributed to the emplacement of ophiolites onto the passive margin sediments towards S- to SE, the second phase is represented by N- to NNE-trending open folds and is consistent with ca. EW shortening, the third phase is associated with continuing strike-slip deformation along the Third Cataract Shear Zone, regional extension because of the thickening of the Saharan Metacraton lithosphere is the fourth phase, and final deformation phase is represented by WSW – ENE-trending strike-slip faulting. In this model, the early phase of gold mineralization was associated with regional deformation and prograde metamorphism, the second stage of gold mineralization was induced by crustal-scale shear zone deformation causes E – W and NNE – SSW faulting which has formed the pathways for hydrothermal fluids to move upward and enriched the quartz veins trough the junctions of the strike-slip faulting.