Genesis and Ore-Forming Process of the No.Ⅳ Intrusion of Jinchuan Super-Large Ni-Cu Magmatic Sulfide Deposit

The No. Ⅳ mining area, situated at the easternmost of the Jinchuan magmatic sulfide deposit, has not been previously investigated for its genesis and mineralization processes. This gap limited the understanding of the deposit's overall mineralization model and exploration potential. In this study, it's conducted systematic core logging and compared macroscopic geological features, incorporating analyses of electron probe data, whole-rock major and trace elements, and platinum-group elements (PGEs). Our results indicate that the olivine Fo values and Ni contents in the ore-bearing rocks of the No.Ⅳ mining area range from 78.3% to 83.9% and 660×10⁻⁶ to 2593×10⁻⁶, respectively. Variations in major element chemistry suggest that the No. Ⅳ area primarily underwent fractional crystallization of olivine and pyroxene. The ore-bearing bodies are slightly enriched in light rare earth elements (LREE) and significantly enriched in large-ion lithophile elements (LILE), while being depleted in high-field-strength elements (HFSE). The PGE content of the IV-1 ore body is notably lower than that of the No. 24, No. 1, and No. 2 ore bodies, with the relatively low PGE content in its host magma identified as the main contributing factor. A synthesis of the macroscopic geological features, olivine composition, and PGE characteristics leads to the conclusion that the No. IV mining area was formed by an independent intrusion of ore-bearing magma. While part of the deposit is controlled by relatively evolved end-member magma, deeper regions may still hold significant exploration potential.