Optimal magmatic oxidation conditions for giant porphyry copper deposits

Article Article scientifique Article Optimal magmatic oxidation conditions for giant porphyry copper deposits eng 2025-01-02 2025-01-02 author Wang Dianzhong 432582 author Zhu Jing-Jing author Hu Ruizhong author Chiaradia Massimo 0000-0003-4943-2480 110575 author Bi Xianwu author Huang Ming-Liang 960-969 10.1016/j.scib.2024.12.048 https://www.sciencedirect.com/science/article/pii/S209592732400985X It is widely accepted that moderately to highly oxidized <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/magma" rel="noopener noreferrer" target="_blank">magmas</a> are needed to form porphyry copper deposits (PCDs). However, only a few studies have attempted to investigate the effects of variable magmatic fO2 values on the formation of PCDs. Based on previously published studies, the magma oxygen fugacity of giant PCDs is mainly concentrated between ΔFMQ −0.5 and ΔFMQ +2.5, with the first quartile, median, and third quartile being +0.8, +1.3, and +1.7, respectively. In this work, we have carried out <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/numerical-modeling" rel="noopener noreferrer" target="_blank">numerical modeling</a>, which shows that the S2− used to precipitate Cu accounts for approximately 90% of total sulfur at ΔFMQ +1 but drops to 33%–38% and 15%–25% at ΔFMQ +2 and ΔFMQ +3, respectively. This leads to a decrease of 88%–96% in Cu precipitation efficiencies from ΔFMQ +1 to ΔFMQ +3. Our petrological model further shows that the maximum Cu precipitation efficiency (and, therefore, Cu endowments) occurs at around ΔFMQ +1. We, therefore, highlight that moderately oxidized magma (ΔFMQ = ∼1) rather than highly oxidized ones (ΔFMQ > ∼2) is optimal for the generation of giant PCDs. Porphyry copper deposits Magmatic oxygen fugacity Precipitation efficiency Dewey 550 42 Département des sciences de la Terre 154 false 663 Isotope Geochemistry, Geochronology and Thermochronology 692 Mineral Resources and Geofluids Science Bulletin 70 6 287380b2-0e94-48fc-9648-5e8555c82acb Article (Published version) Restricted Wang_SciBull_2025.pdf 2428579 application/pdf e1078ba7108198f5aaa3303df88f236a6ff290b60c9f2ba1589db2ed72fffd3f restrictedAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre

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Wang, Dianzhong