Record of the oldest vein-type gold mineralization throughout the Neoproterozoic Nubian shield: the Galat Sufar South gold deposit, NE Sudan
Résumé
Despite the booming interest in Nubian shield for gold exploration, much more remains to be done to constrain geodynamical settings favorable for gold mineralization in a mineral system approach. Constraining pressure-temperature-timing-deformation (P-T-t-d) conditions relative to the formation of the structurally controlled Galat Sufar South (GSS) deposit is a case in point and represents a step forward in the understanding of the Pan-African gold mineral system along the westernmost Atmur-Delgo suture. The formation of the GSS gold deposit, hosted in an arc-related volcanosedimentary sequence metamorphosed and deformed by sheath folding, occurred at 738±16 Ma (in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating of hydrothermal apatite coeval to gold mineralization). Additional chlorite-phengite-quartz-water multi-equilibria calculations in ore-hosting meta-volcanosediments suggest that the gold event occurred under lower amphibolite facies conditions (~7.2 kbar - 420 °C), probably during the tectonic accretion of the sedimentary wedge formed during Atmur-Delgo intra-oceanic subduction. To date, the GSS deposit is the oldest lode gold occurrence documented throughout the Nubian shield and the only one formed at regional peak metamorphism conditions in such a setting.