The Nabeba high-grade iron deposit (Republic of the Congo) is hosted by banded iron formation (BIF) in the Ivindo Basement Complex, which lies in the northwestern part of the Congo Craton. The Nabeba BIF is intercalated with chlorite-sericite-quartz schist and comprises two facies (oxide and a carbonate-oxide). In this study, whole-rock and LA-ICP-MS magnetite geochemistry of the BIF was reported. Magnetite samples from both BIF facies had fairly similar trace element compositions except for the rare earth element plus yttrium (REE + Y) distribution patterns. The high V, Ni, Cr, and Mg contents of the magnetite in the Nabeba BIF could be ascribed to the involvement of external medium-high temperature hydrothermal fluids during their deposition in relatively reduced environment. The Post-Archean Australian Shale (PAAS)-normalized REY patterns of the Nabeba BIF magnetite were characterized by LREE depletion coupled with varying La and positive Eu anomalies. Processing of the information gathered from the geochemical signatures of magnetite and the whole-rock BIF suggested that the Nabeba BIF was formed by the mixing of predominantly anoxic seawater (99.9%) with 0.1% of high-temperature (>250 °C) hydrothermal vent fluids, similar to the formation mechanism of many Archean Algoma-type BIFs reported elsewhere in the world.

The Nabeba iron ore deposit is located at the northern part of Congo Craton, Republic of Congo. The ore deposit consists of supergene and hypogene ores, both of which are hosted in the Precambrian Nabeba banded iron formation (BIF). This study focuses on the hypogene iron ore mineralization associated with quartz veins in the Nabeba deposit, for which two hypogene ore stages have been recognized based on geologic and petrographic observations: early-stage high-grade hematite-rich ore (HO-1) and late-stage magnetite-rich ore (HO-2). Based on microthermometric measurements and laser Raman spectroscopy of the fluid inclusions, the H₂O-NaCl ± CO₂ fluids interacting with the Nabeba BIF at the HO-1 stage evolve from high-to-moderate temperatures (203–405 °C) and contrasting salinities (moderate-to-low: 1–15 wt. % NaCl equiv.; high: 30–35 wt. % NaCl equiv.) to H₂O-NaCl fluids of moderate-to-low temperatures (150–290 °C) and salinities (1–11 wt. % NaCl equiv.) for the HO-2 ore stage. Assuming equilibrium oxygen isotopic exchange between quartz and water, the δ¹⁸O_fluid values range from 4.7–8.1‰ for the HO-1 stage and −2.3‰ to −1.5‰ for the HO-2 stage. This implies the ore-forming fluid of initially-mixed metamorphic–magmatic origin, later replenished by seawater and/or meteoric water during the formation of the HO-2 stage. These mixtures of different fluids, coupled with their interaction with the BIF lithology followed by phase separation, are responsible for the enrichment of hypogene iron ore in the Nabeba deposit.

Despite the significant discovery of hydrocarbon in the Cretaceous Deep-Water Tano Basin of Ghana, detailed molecular characteristics and paleo-depositional environment of the Basin are insufficiently documented in peer-reviewed works. Therefore, in our study, gas chromatography-mass spectrometric (GC-MS) and gas chromatographic (GC) analyses were used to characterize biomarkers obtained from organic matter (oils and rock extracts) to determine the organic matter source, the environment of deposition, and maturity. Sixteen (16) oil and ninety-eight (98) rock samples from seven wells were studied. The work has indicated that distributions of these biomarkers suggested that Cretaceous oils were derived from a mixed kerogen source (marine and terrestrial) deposited in anoxic to suboxic paleo depositional conditions. CPI, T_s/T_m and C₂₉ ββ/(ββ + αα) sterane ratios plotted against C₂₉ 20S/(20S + 20R) sterane ratios indicates that the studied samples are relatively low to medium level maturity.

The Kraaipan and Amalia greenstone belts in South Africa occur in the western part of the Kaapvaal Craton. The two belts stretch discontinuously in an approximately north–south orientation over a distance of about 250 km from southern Botswana in the north to the Vaal River near Christiana in the south and are separated by a distance of about 90 km. Gold mineralization is hosted in banded iron formation at both the Kalahari Goldridge deposit (Kalgold) in the Kraaipan greenstone belt in the north and the Amalia deposit in the Amalia greenstone belt in the south, with the mineralization associated with quartz–carbonate veins. The footwalls of these deposits are generally composed of mafic volcanic schist and the hanging walls consisting of graywackes, schist and shale units. The Kalgold and Amalia gold deposits show some variation in the redox condition of the mineralizing system and fluid chemistry. The ore mineral assemblage is characterized by magnetite–pyrrhotite–pyrite at Kalgold, which is indicative of reducing conditions, and a magnetite–hematite–pyrite assemblage at Amalia that suggests a relatively oxidizing environment. Average mineralizing temperatures determined from chlorite geothermometry were relatively higher at the Kalahari Goldridge deposit ranging from 350 to 400 °C compared to the slightly cooler range of 330 to 390 °C at Amalia. The composition of the fluids derived from fluid inclusions is indicative of low salinity H₂O--CO₂±CH₄-rich fluids at Kalgold against relatively H₂O-CO₂-rich fluids at Amalia. Evidence from strontium–carbon–oxygen isotopic ratios from carbonates suggests that differences in redox conditions in the deposits could be attributed to different flow pathways by an evolving fluid from a common source (with minimum ⁸⁷Sr/⁸⁶Sr = 0.70354) to the sites of gold deposition, with a significant ore fluid interaction with a thick sequence of carbonaceous meta-pelitic rock units at the Kalahari Goldridge deposit that is absent in the Amalia deposit.