The Montecristo mining district, northern Chile: the relationship between vein‑like magnetite‑(apatite) and iron oxide‑copper–gold deposits Mateo, Laura Delgado Huertas, Antonio MtAp deposits IOCG deposits Mineral chemistry Isotope geochemistry Geochronology Coastal Cordillera Andes Chile The Montecristo district, northern Chile, is one of the few places worldwide where there is a direct relationship between magnetite-(apatite) (MtAp) mineralization and iron oxide-copper–gold (IOCG) mineralization. The MtAp mineralization includes Ti-poor magnetite, fluorapatite, and actinolite and is crosscut and partially replaced by a younger IOCG mineralization that includes a second generation of actinolite and magnetite with quartz, chalcopyrite, pyrite, and molybdenite. The MtAp stage at Montecristo is interpreted as the crystallized iron-rich melts that used the pre-existing structures of the Atacama Fault System as conduits. These rocks later acted as a trap for hydrothermal IOCG mineralization. Geochronology data at Montecristo indicate that the host diorite (U–Pb zircon 153.3 ± 1.8 Ma, 2-sigma), MtAp mineralization (40Ar-39Ar in actinolite, 154 ± 2 Ma and 153 ± 4 Ma, 2-sigma), and the IOCG event (Re-Os on molybdenite, 151.8 ± 0.6 Ma, 2-sigma) are coeval within error and took place in a time span of less than 3.4 Ma. The εHfi and εNdi values of the host diorite are + 8.0 to + 9.8 and + 4.3 to + 5.4, respectively. The whole-rock 87Sr/86Sri values of the IOCG mineralization (0.70425 to 0.70442) are in the lower end of those of the MtAp mineralization (0.70426–0.70629). In contrast, εNdi values for the IOCG mineralization (+ 5.4 and + 5.7) fall between those of the MtAp rocks (+ 6.6 to + 7.2) and the host diorite, which suggests that the IOCG event was related to fluids having a more crustal Nd (εNdi < + 5.7) composition than the MtAp mineralization. This likely reflects the mixing of Nd from the MtAp protolith and a deep magmatic-hydrothermal source, very likely an unexposed intrusion equivalent to the host diorite. Sulfur isotope compositions (δ34S, + 0.3 to + 3.4‰) are consistent with a magmatic source. 2023-05-17T06:37:03Z 2023-05-17T06:37:03Z 2023-03-23 info:eu-repo/semantics/article Mateo, L., Tornos, F., Hanchar, J.M. et al. The Montecristo mining district, northern Chile: the relationship between vein-like magnetite-(apatite) and iron oxide-copper–gold deposits. Miner Deposita (2023). [https://doi.org/10.1007/s00126-023-01172-0] https://hdl.handle.net/10481/81592 10.1007/s00126-023-01172-0 eng http://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess Atribución 4.0 Internacional Springer Nature