Integrated geological, petrological, mineralogical, and mineral chemistry investigations of the Neoproterozoic Buem Structural Unit, eastern Ghana: Implications for Fe and Ni-Cu mineralization

• Neoproterozoic Fe-Si sedimentation produced BIF and ferruginous cherts. • Serpentinization-driven fluids upgraded iron and mobilized Ni-Cu. • The BSU is a Pan-African analogue for Fe-dominant metallogenic system. The mechanisms controlling Fe and Ni-Cu enrichment within the Neoproterozoic Buem Structural Unit (BSU) of eastern Ghana remain poorly understood, particularly in relation to regional Pan-African tectono-magmatic processes. This study integrates field geology, petrology, mineralogy, and mineral chemistry to constrain the evolution and metallogenic significance of ferruginous cherts, banded iron formations (BIF), serpentinites, gabbros, and associated ultramafic to mafic rocks. BIF and stratigraphically overlying ferruginous cherts are dominated by hematite ± magnetite with minor apatite and Cr-spinel, consistent with primary chemical sedimentation in an oceanic or marginal basin setting, subsequently modified by deformation, veining, and fluid-mediated recrystallization during Pan-African tectonism. Serpentinites host Ni-rich pentlandite with subordinate chalcopyrite, sphalerite, and pyrite, occurring as intergrowths within pentlandite and associated with magnetite-hematite developed in lizardite mesh textures, indicating redistribution of Ni, Fe, and S during serpentinization and later hydrothermal alteration. Cr-spinel compositions from both ferruginous units and serpentinites display systematic zoning from Cr-spinel through ferritchromite to magnetite, reflecting progressive oxidation and Fe-enrichment linked to fluid-rock interaction. Gabbros and melteigites preserve magmatic Fe-Ti oxide assemblages (ilmenite-titanomagnetite) with magnetite exsolution and Fe-bearing rutile, together with F- and LREE-bearing apatite, pointing to volatile-influenced magmatism followed by late- to post-magmatic hydrothermal modification. Sulfide assemblages in both ultramafic and mafic rocks are volumetrically minor but chemically coherent, suggesting limited primary sulfide accumulation and instead reflecting localized metal redistribution during fluid circulation. In this contribution we infer that the BSU records a multistage evolution involving Neoproterozoic chemical sedimentation of Fe-rich units, subsequent mafic–ultramafic magmatism, and Pan-African tectono-hydrothermal overprinting that facilitated remobilization and upgrading of Fe and Ni-Cu-Co. The gabbros, which represent the plutonic component of an ophiolitic oceanic crustal sequence contributed to the thermal and permeability architecture of the system, promoting hydrothermal fluid circulation and metal redistribution, and underscoring the Buem Structural Unit as a prospective analogue to other Pan-African terranes with Fe-dominant and subordinate Ni-Cu mineralization potential.