CIG WEBINAR: Magnetite-apatite deposits by extrusion of iron-rich melt, T. Keller, ETH


For those of you who are interested in the topic of ore formation, do not forget to register for next week’s CIG Webinar which is a great complement to Anne Glerum’s great talk this week on sediment hosted ore deposits. Recording of both talks will be posted to your YouTube channel.


Thursday 09 February, 2023, 10:00 am - 11:00 am PST - NEW TIME**

Genesis of the El Laco magnetite-apatite deposits by extrusion of iron-rich melt: a modelling perspective. Tobias Keller, ETH

Magnetite-apatite deposits are important sources of iron and other metals. A prominent example are the magnetite lavas at the El Laco volcano, Northern Chile. Their formation processes remain debated. Here, we test the genetic hypothesis that an Fe-rich melt separated from silicate magma and ascended along collapse-related fractures. We complement recent analyses with thermodynamic modelling to corroborate Fe-Si liquid immiscibility evident in melt inclusions at El Laco and present viscometry of Fe- and Si-rich melts combined with scaling analysis of immiscible melt segregation to assess the time and length scales of immiscible liquid separation. Using a 2D numerical rock deformation model combined with scaling analysis of bubbly flow in a fracture, we demonstrate that volcano collapse can form failure zones extending towards the edifice flanks along which the ore liquid ascends towards extrusion driven by vapour exsolution despite its high density. Our results support the proposed magmatic genesis for the El Laco deposits. Geochemical and textural similarities indicate magnetite-apatite deposits elsewhere form by similar processes. [more info ] [register ] [all webinars]