Insights into gold mineralization in the Arkawit area, NE Sudan: A structural, geochemical, and isotopic approach

Abstract

Gold mineralization within the Haya Terrane (HT) of the Arabian–Nubian Shield (ANS) in NE Sudan remains genetically ambiguous due to unresolved relationships between deformation, fluid sources, and metal transport that occurred during Pan-African tectonism. Specifically, the relative contributions of structurally focused metamorphic fluids in contrast to potential magmatic inputs in gold formation have not been sufficiently constrained. This study employs an integrated approach that encompasses structural analysis, petrography, whole-rock geochemistry, in-situ LA-ICP-MS, and stable oxygen–hydrogen isotope data to establish a robust genetic model for the Arkawit gold deposit. Field and structural investigations have identified four distinct deformation phases (D1–D4). The NE–SW-trending dextral shear zones that developed during the D3 phase serve as primary conduits for hydrothermal fluid flow and the emplacement of auriferous quartz veins. Petrographic observations indicate extensive hydrothermal alteration zones, initially dominated by epidotization, followed by the formation of chlorite–sericite assemblages. Geochemical analyses reveal a moderate positive correlation between Au and Pb, alongside a negative correlation with Cu, thereby suggesting fluid evolution and metal decoupling throughout the mineralization process. Three generations of pyrite (Py1–Py3) have been distinguished based on their morphology, paragenesis, and trace element chemistry. Py1 is interpreted as magmatic, characterized by elevated levels of Ni and Co and reduced levels of Au and As. In contrast, Py2 is identified as hydrothermal in origin, exhibiting enrichment in As, Ag, and Pb. Stable isotope data indicate that the ore-forming fluids were predominantly metamorphic in nature. The δ¹⁸O values of quartz range from + 8.26‰ to + 11.73‰, with an average of + 9.68‰ and the calculated average δ¹⁸O water value is + 3‰, while the δD values of fluid inclusion water average − 44‰. These isotope values fall within the compositional range typical of metamorphic fluids in orogenic gold systems. However, limited overlap with magmatic fields suggests a minor contribution from adjacent intrusions. This study provides novel constraints on the structural and fluid controls governing gold mineralization in the HT. It confirms that structurally focused metamorphic-hydrothermal fluids were the predominant agents of ore formation. The findings present practical criteria for exploration within the ANS, emphasizing NE–SW shear zones, arsenian pyrite, and associated alteration halos as critical targets for orogenic gold exploration.