Sapphire deposits along the Cameroon Volcanic Line are commonly assumed to be genetically linked to alkaline basalts; however, their primary source remains debated. Alluvial sediment geochemistry can constrain provenance and formation conditions. We investigated the sapphire-bearing alluvial sediments at Addi (Adamawa, Cameroon) to determine their composition, provenance, and the nature of the sapphire source rocks. We combined sedimentological analysis, heavy mineral identification, X-ray diffraction, and major/trace element geochemistry (X-Ray diffraction, Inductively Coupled Plasma-Mass Spectrometry). Sediments are coarse sands with sub-angular to sub-rounded sapphire grains (2-5 mm), indicating short transport distances. Composition is dominated by SiO2 (42-69 wt%), Al2O3 (12-25 wt%), and Fe2O3 (2-11 wt%). Chemical weathering indices indicate moderate weathering in semi-arid conditions. High LREE/HREE ratios, positive Eu anomalies, and trace element patterns (high Ba, Zr, Th contents) point to felsic source rocks with minor basaltic contribution (exceptional high Cr contents). Geochemical proxies consistently indicate derivation from felsic igneous rocks (syenites, granites). The sediments are geochemically immature and deposited in oxic, high-energy fluvial conditions. This study demonstrates that Adamawa sapphires crystallized in syenitic intrusions subsequently uplifted by basaltic flows. Primary basaltic origin is unsupported by the present data. This study is a significant contribution for sapphire alluvial exploration and primary source identification.