Carbonatites and Nepheline Syenites of the Kpong Complex, Ghana: Agronomic Value, CO₂ Removal Potential, REE Prospectivity, and Environmental Considerations

The Kpong Alkaline Complex (KAC), southeastern Ghana, comprises carbonatitic rocks and nepheline syenites whose contrasting chemistries offer complementary agronomic, CO₂-removal, and rare-earth element (REE) potentials. Although the geology is described, applied potential remains under-evaluated. We integrate petrography, mineralogy, and major–trace geochemistry from new and published data to evaluate these potentials. Mineralogy shows dominant calcite, nepheline, plagioclase, alkali feldspar, and biotite with some apatite. Nepheline, which is a highly reactive in enhanced rock weathering (ERW), supplies K and Na; calcite contributes Ca that raises soil pH, supports plant nutrition, and facilitates carbonate formation; apatite supplies P. Major elements show large CaO variability, with some carbonatites >30 wt% and nepheline syenites ~3 wt%. Stoichiometric calculations from oxides indicate theoretical CO₂ drawdown up to ~300 kg CO₂ t⁻¹ rock, consistent with basaltic feedstocks in scalable ERW/carbon-dioxide removal (CDR) applications. REE data indicate total LREE to ~700 ppm. Potentially toxic elements (PTEs) in rocks and nearby soils are low (Ni <25 ppm, As <5 ppm, Pb <34 ppm), below commonly cited WHO and USEPA soil guideline ranges, within relevant EU limits for inorganic soil improvers, and at or below typical upper-crustal backgrounds. Collectively, these lines of evidence indicate minimal PTE loading at agronomic application rates and support the KAC as a locally available, low-toxicity resource with tripartite utility: (1) improving soil fertility, (2) contributing to climate mitigation via CO₂ removal, and (3) offering potential REE feedstocks, pending techno-economic validation.