Platinum Group Element Geochemistry of the Jinchuan <scp>Ni</scp> ‐ <scp>Cu</scp> ‐ <scp>PGE</scp> Deposit, <scp>NW</scp> China: Implication for Its Ore‐Forming Process

ABSTRACT The Jinchuan Ni‐Cu‐platinum‐group elements (PGE) deposit is located at the southern edge of the North China Craton within the Longshoushan Terrane, with mineralization accounting for 47% of the intrusion. The deposit contains abundant net‐textured ore, primarily olivine‐sulfide heteradcumulate, comprising over 50% of the assessed resources. The origin of the deposit is debated, with theories ranging from the formation of olivine‐sulfide mush to sulfide segregation in a single intrusion or multiple ore pulses. This study supports a single intrusion model, with platinum‐group elements (PGE) distribution patterns indicating ore zones derived from a common magmatic source. The copper Pd‐group PGE (Cu‐PPGE)‐rich ores, characterised by coarse net‐textured segregations, occur interstitial to Cu‐PPGEs‐poor oikocrysts and as fault‐localised semi‐massive segregations in Ore Bodies 1 and 24 (central and WNW regions), displaying pronounced Cu‐PPGE‐Au enrichment relative to Fe‐Ni‐Co‐ Ir‐group PGE (IPGE). Sulfide ores are concentrated near the lower section of the intrusion, often along fault zones, with many showing negative Pt anomalies and platinum deficiencies when normalised to primitive mantle composition. The PGE concentrations in the Jinchuan parental magma were estimated using average ore compositions and published partition coefficients, with variations in R factors and monosulfide solid solution (MSS) fractionation explaining the PGE distribution across different ore types. Hydrothermal modification was minimal (&lt; 5% of samples). Ore Bodies 1 and 24 formed at moderate R factors (500–1000) with 0%–80% MSS fractionation, while ore body 2 (SES section) formed at lower R factors (300–700) with 0%–40% MSS fractionation. The negative Pt anomalies and Pd‐Pt fractionation are attributed to early olivine and chromite crystallisation, MSS fractionation (preferentially incorporating Pt over Pd), and limited hydrothermal Pt mobilisation. The varying ∑PGEs 100 values in massive and disseminated sulfide ores reflect their magmatic origins, collectively explaining the complex PGE patterns in the Jinchuan intrusion.