Talc mineralization in the SW Fodikwan area, Red Sea Hills, NE Sudan: Geological and geochemical constraints

Abstract

Talc deposits found in the southwestern Fodikwan area of northeastern Sudan exhibit potential economic significance; nevertheless, their geological context, geochemical characteristics, and genesis remain inadequately defined. This study aims to elucidate the origin and formation mechanisms of these deposits, thereby facilitating the development of more effective exploration strategies. An integrated methodology was employed, comprising detailed geological mapping, petrographic investigations, and mineralogical and geochemical assessments utilizing X-ray diffraction (XRD) and X-ray fluorescence (XRF). The study area is characterized by basement rocks comprising a volcanic-sedimentary sequence that has been metamorphosed in the greenschist facies and intruded by syn-to late-orogenic microgranodiorite. Field and petrographic observations indicate that unaltered dolomitic marble predominates in areas distant from microgranodiorite contacts. Conversely, the contact zone between dolomitic marble and microgranodiorite presents a conducive environment for talc mineralization. Geochemical analyses reveal that SiO₂ and MgO are the dominant constituents, whereas CaO exhibits a decreasing trend as SiO₂ increases, reflecting the metamorphism of dolomitic marble into talc. Additionally, a noteworthy depletion of Al, La, Th, Cr, Ni, and Co in talc ores is inconsistent with a mafic or ultramafic protolith. The results suggest that the silica necessary for talc formation was derived from the adjacent microgranodiorite, with dolomitic marble acting as the primary protolith. Furthermore, the presence of quartz within the dolomitic marble may have provided the necessary silica for the formation of talc. This evidence supports a genetic model of contact metasomatism and has significant implications for regional talc exploration, particularly targeting the marble-microgranodiorite contact zones.