Clay-Hosted Lithium in Aluminous Laterites of NW Himalaya: Petrographic and Paleoenvironmental Evidence from the Salal-Reasi Area

The Jangalgali Formation of the Salal–Reasi area, Jammu and Kashmir (NW Himalaya), hosts Li-bearing karst-type aluminous laterites formed during the Cretaceous–Eocene, representing an important example of clay-hosted lithium enrichment in a lateritic weathering system. Although anomalous Li concentrations have been reported earlier, the host phases, enrichment mechanisms, and paleoenvironmental controls on Li mineralization remained poorly constrained. This study integrates petrography, X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM–EDS), whole-rock geochemistry, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to evaluate mineralogical and geochemical controls on Li enrichment. The laterites occur as pisolitic to non-pisolitic horizons with thicknesses of ∼1–6.7 m and are enriched in Al₂O₃ (17.61–69.69 wt.%), TiO₂ (1.03–6.80 wt.%), and Li (15–2847 ppm). Mineralogical data show dominance of kaolinite, diaspore, boehmite, illite, and anatase/rutile, with Li primarily hosted in clay minerals (kaolinite ± smectite), whereas Ti is retained in refractory Ti-oxide phases. Petrographic and geochemical observations confirm strong mineralogical control on Li–Al–Ti enrichment during lateritization, accompanied by deferruginization and desilication. Geochemical proxies indicate acidic conditions of formation, while MgO/Al₂O₃ (1.07 × 10⁻³–8.61 × 10⁻³) and Rb/K (1.0 × 10⁻³–8.7 × 10⁻³) ratios suggest a marine–continental transitional to continental setting. Redox-sensitive ratios (Th/U = 1.45–20.40; V/Cr = 0.55–4.34) indicate predominantly dysoxic to oxic conditions, whereas very high Chemical Index of Alteration (92.23–99.79) and C-values (0.53–19.07) support formation under a hot and humid paleoclimate. These results highlight intense lateritic weathering and clay-controlled Li enrichment in karst-type aluminous laterites of the NW Himalaya.