Geology and Gold Mineralization of the Area around Al-bidiya Area, River Nile State, Sudan

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Geology, Mineralization, Volcanosedimentary, Gold
Sadam H. M. A. Eltayib
The study revealed that the area was consisting of basic, ultra-basic cumulates rocks which were considered as part of dismembered of ophiolite, these rocks exposed in the area east of Al Salam Mine. They are structurally overlain by volcanosedimentary sequence that also overlain by granodiorite in the west. The volcanosedimentary sequence of the study area are composed of acid to intermediate volcanics, volcanicalstic derivatives and turbiditic sediments such as andesite , chlorite schist, quartz sericite schist, phyllite, banded chert and graphite schist. All of these rocks are intruded by syn-orogenic granodiorite and aplite dykes and lately intruded by mineralized and non-mineralized gold-bearing quartz and chert veins. The volcanosedimentary sequences have been metamorphosed to low-grade of green schist facies of regional metamorphism. Field observations, kinematic analysis of structural data and subsurface geological cross sections along the diamond drill holes indicates presence of at least six transpressive deformation phases which is characterized by diverse geometries of folds generated cross and multiply folded and refolded and imbricates thrust and reverse faults, strike-slip and dip-slip faults and shearing. Most of these structures trend to the NW-SE direction and the folds slightly plunging to both sides as a result of the progressive deformation of the allochthons related to KSZ. From the study of core samples and polished section two types of gold mineralization of VMS have been identified. The first type is conformable (syn-genetic type) with layering of the country rocks, while the second is epigenetic type associated with quartz veins and stringers that emplaced along the schistossity planes, fold hinges, faults zones, fractures and shear joints. Two groups of gold and associated minerals have been identified; the first with iron sulphides, while the other with cupper sulphides as by product. Surpac program are used to draw the solid block model of the ore body, which appear structurally controlled by the synform folding, while the total volume of the ore body was calculated4818625m³. The program also used to estimate the preliminary ore reserve, which reach to 5494929 kg of gold metal. From the study of other international cases, the general geological characteristic of the mineralization and ore geometry of Al Salam gold Mine is more or less similar to Kuroko deposit in Japan.