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A schematic model demonstrates the Ti isotopes behavior in the laterite formation process. During the intensive chemical weathering process, primary silicates have dissolved. However, Fe-Ti oxides still remained in the residue with light Ti isotope compositions. Dissolved Ti was absorbed onto the Fe (hydr)-oxides and clay minerals which inherited heavy Ti isotope compositions from silicates. And the secondary minerals particles were the mainly form of Ti removal. • The Δ 49 Ti fluid-remained could reach 0.2‰ during intensive weathering processes. • Differential weathering processes controlled the δ 49 Ti variations of the saprolites. • Significant δ 49 Ti gaps have been observed among secondary Ti-bearing phases. • The gaps compounded by physical sorting processes may lead to δ 49 Ti variations in sediments. The titanium (Ti) isotope compositions of bulk saprolites, parent-rock minerals, extracted crystalline Fe (hydr)-oxide phases and residual phases (clay minerals and Fe-Ti oxides) from the Neogene tholeiitic basalt weathering profile on Hainan Island, China, were measured in order to (1) test the hypothesis that Ti isotope compositions are immune to water–rock interactions and (2) elucidate Ti isotope fractionation mechanisms during extreme weathering processes. Relative to the OL-Ti isotope standard, the δ 49 Ti values in the saprolites range from −0.068‰ to +0.076‰, with an average of 0.026‰, which is slightly lighter than the unaltered basalt (0.052 ± 0.051 ‰). A significant Ti isotope fractionation exists between extracted crystalline Fe (hydr)-oxide phases and residual phases, which is up to 0.6‰. The residual phases (they account for 72% to 94% of the Ti) have light Ti isotope compositions (−0.165‰ to 0.043‰), inherited from the primary weather-resistant ilmenite (− 0.200 ± 0.055 ‰), whereas the crystalline Fe (hydr)-oxides (5% to 26% of the Ti) have heavy δ 49 Ti values, ranging from 0.108‰ to 0.540‰, transferred from the primary pyroxene phenocrysts (0.176 ± 0.039 ‰) and groundmass (0.153 ± 0.057 ‰). The Ti isotope composition of this weathering profile was controlled by the formation and dissolution of titaniferous minerals. Given that physical sorting as a result of long-distance transport and deposition changes the mineral assemblages of sediments and combined with significant δ 49 Ti gaps among secondary Ti-bearing minerals, we emphasise that the application of Ti isotopic compositions to sediment provenance studies should be undertaken with caution. [ABSTRACT FROM AUTHOR]