Geochemistry Of Ariab VMS Deposit And Significance For Mineral Exploration In Red Sea Hills N E Sudan

It can be concluded after studying the geological setting and features of the Ariab ore deposits,trace and REE geochemistry of volcanic host rocks and altered rocks,and pyrite geochemistry in massive sulphide ore by La-ICP-MS:1.A significant hydrothermal event evolved in the Ariab-Arbaat belt at the end of the Pan-African tectono-thermal event.This hydrothermal event was responsible for the mobilization or remobilization of polymetallic and gold bearing assemblages and is considered to represent a late influx of high temperature?up to 400°C?fluids at the end of the metamorphic?retrograde?event.Early hydrothermal activity started with widespread,quartz-sericite-chlorite alteration with pre-kinematic barite-magnetite impregnation.A second,synkinematic stage of advanced kaolinization,and widespread silicification,sericitization and chloritization follows the earlier stage.2.The study of host rock geochemistry indicates the felsic volcanic rocks?unit C?formed in the calc-alkaline island arc field and the rhyolites show typical characteristics of acid leaching phenomenon associated with volcanogenic massive sulphides.The Ariab volcanic rocks have been slightly enriched in LREE and are characterized by an enrichment in large ion lithophile elements?LILE?over the high field strength elements?HFSE?relative.The geochemical diversity including presence of high-Mg or basic boninitic-andesites,basaltic tholeiitic lava types with transitional major and trace element patterns and adakitic intrusions,suggest that the Ariab series may reflect an arc polarity representing a spatial transition from a zone of crustal-mantle interaction towards a zone of?normal?arc regime.3.Major element abundance is very susceptible to modification during hydrothermal alteration and low-grade metamorphism,and is therefore of limited value for determining magmatic setting of altered rocks.In the Ariab area,concentration of some elements in the primary rocks may have been modified by secondary effects such as metamorphism and concomitant deformation,thus masking the original nature of some of these rocks.4.REE shows the analogy between the early granitoids and rhyolites from?Th/Ta?_N vs.?Tb/Ta?_Ndiagram and the felsic rocks at Ariab,including C₁ and C₂ rhyolites,both closely associated with massive sulphide deposits,form a coherent group compositionally similar to early trondhjemite.5.The results from the trace elements in pyrite of Awateeb and Hassai by LA-ICP-MS indicate that:?1?Co/Ni ratio the pyrite can be used as indicator of VMS metallogenic environment in Ariab area;?2?The ternary plots of trace element in pyrite could be useful to differentiate different mineralizations and even pyrites from mineralized versus noneconomic?i.e.,barren?samples,which can be used as VMS indicators for mineral exploration;?3?The pyrite is rich in Se and similar to the features of pyrite in mafic?'Cyprus-type'?VMS deposits.