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Key new insights into controls on magmatic ore fertility through melt inclusions at the Parinacota volcano

Iván Mateo Espinel Pachón1, Michael Schirra1, Alexandra Tsay1, Mara Miranda1, Cristóbal González Rodriguez2, Zoltan Zajacz^1 ^

  • Affiliations: 1 Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, 1205 Geneva, Switzerland.   2Department of Geological Sciences, Universidad Católica del Norte, Millennium Institute on Volcanic Risk Research---Ckelar Volcanoes, Casa Central. Angamos 0610, Antofagasta, Chile. 

  • Presentation type: Talk

  • Presentation time: Tuesday 15:00 - 15:15, Room S160

  • Programme No: 4.1.4

  • Theme 4 > Session 1

Abstract

The redox state of magmas significantly affects their physical properties, differentiation , ore-forming potential, and the emission of sulfur-bearing gases into the atmosphere. Oxidized, sulfur-rich magmas are prevalent in convergent plate margins and are responsible for forming large porphyry Cu-(Mo-Au) deposits, the primary sources of copper and molybdenum for modern society. This study investigates the origin of these key characteristics through the analysis of silicate melt inclusions, hosted in olivine and clinopyroxene, in volcanic rocks from the Parinacota volcano, located in the Central Andes. The findings reveal oxidized, near-primitive mantle melts that exhibit co-enrichment in sulfur, strontium, barium, thorium, and light rare earth elements. Importantly, no evidence was found to suggest further oxidation during magma differentiation. These results suggest that the oxidized state of arc magmas is predominantly attributed to the flux of sulfate-rich sediment melts derived from the subducting slab. This process enriches the magmas not only in sulfur but also in strontium and light rate earth elements. This mechanism may be integral to explaining the elevated Sr/Y and La/Yb ratios commonly associated with magmas that generate porphyry-type ore deposits. These insights provide a clearer understanding of the processes driving the redox evolution and metallogenic potential of arc magmatic systems.