<p>The Dongqiao ophiolite in the central Bangong–Nujiang Suture Zone (Tibetan Plateau) hosts numerous irregular to podiform chromitite bodies formed within a supra-subduction zone mantle setting. Chromite mineral chemistry, platinum-group element (PGE) geochemistry, and Fe–Mg isotope systematics of chromitites and their host peridotites are used to constrain chromitite-forming processes and subsequent mantle modification. Chromitites are dominated by high-Cr chromite (Cr# = 60.7–79.8) with very low TiO₂ contents (≤ 0.13 wt%), indicating chromite saturation from boninitic melts in a forearc mantle wedge. Host dunites and harzburgites are highly depleted in Al₂O₃, CaO, and incompatible elements relative to primitive mantle, consistent with derivation from a previously melt-depleted mantle source. Bulk-rock PGE concentrations are highest in chromitites (ΣPGE = 80–819 ppb) and are characterized by strong enrichment in IPGE (Os–Ir–Ru) relative to PPGE, together with low (Pd/Ir)_N ratios, reflecting chromite-controlled PGE fractionation under reduced, sulfur-poor conditions. Chromitites exhibit lighter Mg and Fe isotope compositions (δ²⁶Mg = − 0.57 to − 0.03‰; δ⁵⁶Fe = − 0.07 to 0.12‰) than their host peridotites (δ²⁶Mg = − 0.59 to 0.19‰; δ⁵⁶Fe = 0.02 to 0.22‰). Systematic covariation among δ²⁶Mg, δ⁵⁶Fe, and chromite Cr# suggests coupled isotope fractionation during chromite crystallization and melt–peridotite interaction. These features indicate that Dongqiao chromitites formed through focused interaction between boninitic melts and a refractory forearc mantle, with chromite exerting a primary control on PGE budgets and Mg–Fe isotope signatures. The Dongqiao chromitites therefore record evolving redox conditions and melt–fluid interactions associated with subduction initiation and Early Jurassic closure of the Meso-Tethyan Ocean.</p>