Mapping and analysis of stream sediment heavy mineral fractions for mineral exploration: a case study of a portion of North-Central Nigeria

Although artisanal mining is dominant in the Pan-African Mineral Belt in North-Central Nigeria, there are no known reports of studies detailing the mineralization, type of mineral occurrences, and processes controlling the mineralization in the area. This paper reports on the geochemical evaluation of heavy mineral fractions in stream sediment to understand the mineral occurrences and characteristics in the Lokoja area, Nigeria. The adopted methodology involved delineating the study area based on potential mineralization and collecting stream sediment samples (n = 67) for heavy mineral fractions in a sampling density of 1 per 10 m2. The samples were analyzed for their geochemical and mineralogical compositions using inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), and energy dispersive X-ray fluorescence (EDXRF). The obtained results were subjected to Sequential Binary Partition, followed by appropriate mathematical log-ratio transformations to deal with inherent problems associated with compositional data. The obtained data was then analyzed using descriptive statistics, analysis of Median Absolute Deviation, and threshold mapping was employed to delineate geochemical anomalies. Univariate and multivariate analyses were employed to understand the geochemical associations, dispersion patterns, and geological processes. The result showed that the concentration of elements like Mo, Cu, Zn, Au, Sr, Zr, Ce, W, Nb, Ta, and Be was anomalous in the stream sediment samples. The new anomalies of base and rare metals, precious metals, and gemstone's potential mineralization of the basement terrain were observed towards the south of Lokoja. The mineralogical and ore mineral studies showed the presence of tantalite and beryl indicating the basement terrain potential mineralization towards the southern part of the study area. The constructed geochemical maps provided insights into the distribution of geochemical parameters across the study area. Overall, this study advances our knowledge of the geochemistry of stream sediments and its application in mineral exploration. The results can help identify possible ore resources in the basement terrain of North-Central Nigeria and other similar geological settings elsewhere.