Journal article
Magmatic-hydrothermal evolution of the El Laco iron deposit revealed by trace element geochemistry and high-resolution chemical mapping of magnetite assemblages
Geochimica et Cosmochimica Acta, Vol.330, pp.230-257
2022
Abstract
The Plio-Pleistocene El Laco magnetite ore bodies in the Chilean Altiplano represent an unusual subvolcanic/aerial type of an iron oxide-apatite (IOA) deposit. The textures of these magnetite ore bodies have sustained a long-standing geological controversy on the origin of iron oxide deposits with models spanning the spectrum from purely igneous to magmatic-hydrothermal processes. In particular, the link between the geochemical processes taking place in the source magma and the subsequent evolution of the overlying magmatic-hydrothermal system are still not well understood. Here we address this problem by focusing on microtextural and geochemical features of iron ore and silicate gangue minerals retrieved from drill core samples from El Laco ore bodies, as well as from the andesite volcanic host rocks. We report a comprehensive geochemical dataset of magnetite assemblages at El Laco obtained using a combination of EPMA, LA-ICP-MS, and synchrotron radiation µ-XRF methods. Microtextural and geochemical data of magnetite reveal consistent variations with depth. Magnetite in the andesitic host rocks and from deep/intermediate levels of the ore bodies have a high concentration of trace elements including Ti, V, Ni, Mn, Zn, Cr, Al, Ga, Cu and Co in comparison with magnetite from the upper sections of the ore bodies. Clinopyroxene is present in the andesite host rocks as well as the ore bodies, showing chemical differences between both types, with Mn and Fe contents that are higher in the former, and Na and Ca concentrations enriched in the latter. We interpret the enriched-to-depleted compositional trends in magnetite and clinopyroxene as resulting from a transition from purely igneous conditions to a fluid-dominated, cooling magmatic-hydrothermal system. Detailed microtextural analysis of magnetite and clinopyroxene from the ore bodies support this notion, revealing multiple growth stages punctuated by dissolution-reprecipitation processes. Our data further supports a genetic model that explains the formation of the El Laco iron oxide deposit through the injection, upward migration and venting of magmatically-derived Fe-rich fluids.
Details
- Title
- Magmatic-hydrothermal evolution of the El Laco iron deposit revealed by trace element geochemistry and high-resolution chemical mapping of magnetite assemblages
- Authors/Creators
- J.T. Ovalle (Author/Creator) - University of ChileM. Reich (Author/Creator) - University of ChileF. Barra (Author/Creator) - University of ChileA.C. Simon (Author/Creator) - University of MichiganA.P. Deditius (Author/Creator) - Murdoch UniversityM. Le Vaillant (Author/Creator) - Commonwealth Scientific and Industrial Research OrganisationO.K. Neill (Author/Creator) - University of MichiganG. Palma (Author/Creator) - Universidad MayorR. Romero (Author/Creator) - University of ChileN. Román (Author/Creator) - University of ChileN.L. La Cruz (Author/Creator) - University of MichiganM.P. Roberts (Author/Creator) - The University of Western AustraliaD. Morata (Author/Creator) - University of Chile
- Publication Details
- Geochimica et Cosmochimica Acta, Vol.330, pp.230-257
- Publisher
- Elsevier BV
- Identifiers
- 991005544767507891
- Copyright
- © 2022 Elsevier Ltd.
- Murdoch Affiliation
- Harry Butler Institute
- Language
- English
- Resource Type
- Journal article
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- Citation topics
- 8 Earth Sciences
- 8.8 Geochemistry, Geophysics & Geology
- 8.8.1 Geochemical Petrogenesis
- Web Of Science research areas
- Geochemistry & Geophysics
- ESI research areas
- Geosciences