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Volcanoes as windows into metal processing pathways in the crust

Marie Edmonds1 , Olivia Hogg1, Emma Nicholson2, Frances Jenner3

  • Affiliations: 1Earth Sciences Department, University of Cambridge, UK 2University of Waikato, Hamilton, New Zealand 3School of Environment, Earth and Ecosystem Sciences, The Open University, UK

  • Presentation type: Talk

  • Presentation time: Tuesday 16:15 - 16:30, Room S160

  • Programme No: 4.1.7

  • Theme 4 > Session 1

Abstract

Crustal enrichments in chalcophile metals and metalloids such as copper, selenium and gold are of interest because of increasing global demand for these elements related to the energy transition.  These elements are, under certain conditions, enriched in porphyry magmatic systems located in subduction zone settings. Understanding pathways of metal enrichment through silicate melts, sulfide and exsolved volatile phases is key to understanding how these enriched porphyry systems form. Volcanoes provide us with a means of examining and understanding these pathways through study of exsolved fluids (gases and aerosols), textures of erupted rocks, as well as melt inclusions and whole rock element abundances. The abundance of Cu (and other sulfide-loving elements) in silicate melts, for example, is strongly influenced by sulfide saturation and volatile degassing during fractionation. Here I present a range of datasets from volcanoes in different settings and use them to generate generic models to quantify the impact of magmatic water content on Cu pathways during crustal evolution of arc magmas and the implications for the abundance and distribution of sulfur and Cu in saline magmatic fluids. Ubiquitous sulfide saturation is a critical limitation on the chalcophile element and sulfur load of exsolved magmatic fluids. However, reactive flow through mush zones involving sulfide-undersaturated melts may resorb accumulated sulfides and this may be an important way to generate Cu (and other chalcophile element)-rich fluids.