Genesis and evolution of the San Manuel iron skarn deposit (Betic Cordillera, SW Spain) González Pérez, Igor González Jiménez, José María Gervilla Linares, Fernando Abad Ortega, María del Mar Moreno Abril, Antonio Jesús Magnesioferrite Magnetite Mg-skarn Ronda peridotites Spinel exsolution LA-ICP-MS This study was funded by the Spanish project RTI2018-099157-A-I00, granted by the “Ministerio de Ciencia, Innovación y Universidades”, the grant PRE2019-088262 “Ayudas para contratos predoctorales para la formación de doctors” (FPI), defrayed by the “Ministerio de Ciencia, Innovación y Universidades. The Mexican research program “CONACYT-Ciencia Básica” A1-S-14574 is also thanked for proving additional funding for standards employed in LA-ICP-MS analysis. J.M. González-Jímenez also acknowledge funding provided by the Ramón y Cajal Fellowship RYC-2015-17596. We would like to thank X. Llovet from “Serveis Cientifico-Técnics” (CCiTUB) of the Universidad de Barcelona for his invaluable assistance with the electron probe micro-analyzer, and to C. Ortega-Obregón from the “Laboratorio de Estudios Isotópicos of the Centro de Geociencias” (UNAM, Mexico) for his help with the LA-ICP-MS analyses on magnetite. Moreover, we would like to express our gratitude to I. Sánchez from the “Centro de Instrumentación Científica “(CIC-UGR) for her supporting of the scanning electron microscope. The authors would like to acknowledge the use of “Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza”, particularly the help of C. Gallego and L. Casado Zueras from the “Advanced Microscopy Laboratory” (LMA) for their careful preparation of the EBSD maps and FIB samples, respectively. The San Manuel magnesian skarn is an iron deposit hosted in dolomitic marbles from a tectonic slice imbricated within the Ronda peridotites, in the westernmost part of the Betic Cordillera, Spain. According to the dominant mineral assemblage, the skarn is subdivided into three different zones, (1) forsterite ± calcite skarn, (2) calcite ± chlorite ± serpentine skarn, and (3) Ca-amphibole skarn. The main ore in the skarn is a ∼ 2.5 m thick, massive ore body situated in the middle of the sequence. In this paper, we firstly report a comprehensive major to trace element composition, texture, microstructure, and mineralogy characterization for zoned magnesioferrite-magnetite grains of the San Manuel deposit using a combination of (1) laser ablation inductively coupled plasma mass spectrometer, (2) focused ion beam combined with transmission electron microscopy, and (3) electron back-scattered diffraction. We have defined four different magnesioferrite-magnetite generations. A complete sequence of zoning includes cores of magnesioferrite (Mag-1; MgO up to 10.6 wt%) overprinted by three successive generations of magnetite, namely Mag-2, Mag-3, Mag-4. Mag-2 (MgO < 4 wt%), hosts composite forsterite ± calcite ± chlorite inclusions, consistently with high Si, Ca, and Sr (average: 8204 ppm, 8980 ppm, and 49 ppm respectively) contents detected by in situ laser ablation inductively coupled plasma (LA-ICP-MS). Mag-3 replacing former Mag-1 and Mag-2 includes nanometric spinel and gahnite exsolutions detected by focused ion beam combined with a transmission electron microscope (FIB-TEM), which is consistent with its high Al, Ti, V, and Ga (average: 5073 ppm, 368 ppm, and 20 ppm, respectively) trace element concentration. Mag-4 is the Fe-richest magnetite (up to 94.16 wt% FeOtotal) forming the outermost rims in magnetite grains, and exhibiting the lowest total trace element contents. Approaches in temperature estimations employing magnetite-spinel exsolutions in Mag-3 suggest that the minimum temperature of the prograde stage reached temperatures below 700 °C, whereas Mag-4 should be formed during the retrograde stage. Magnetite microstructure studied by electron backscatter diffraction (EBSD) suggests Mag-4 formation under fluid-assisted dynamic conditions, which is consistent with the tectonic evolution of the emplacement. We propose that the San Manuel deposit formed by pulsed hydrothermal fluids derived from anatexis of crustal rocks during peridotite emplacement, promoting re-equilibration processes that led to the magnesioferrite-magnetite zoning. 2022-02-02T11:05:11Z 2022-02-02T11:05:11Z 2022-02 info:eu-repo/semantics/article I. Gonzalez-Pérez et al. Genesis and evolution of the San Manuel iron skarn deposit (Betic Cordillera, SW Spain). Ore Geology Reviews 141 (2022) 104657. [https://doi.org/10.1016/j.oregeorev.2021.104657] http://hdl.handle.net/10481/72609 10.1016/j.oregeorev.2021.104657 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España Elsevier