13:15, Lecture hall C.01

Dr. Barbara Ratschbacher (Bundesanstalt für Geowissenschaften und Rohstoffe Hannover)

Fe³⁺/Fe^T Ratios in Igneous Amphibole Minerals: A Tool to Understand the Redox State of Arc Magmas

Abstract: Volcanic rocks erupting in subduction zone settings are generally more oxidized compared to those erupting from mid-ocean ridges. The process(es) causing these elevated oxygen fugacities in arc settings are controversial but attributed to either source (mantle) and/or crustal differentiation processes. Distinguishing between these processes is challenging due to difficulties constraining the redox state of arc magmas particularly in arc intrusive rocks. Amphibole is an important fractionating phase during calc-alkaline differentiation in arc magmas and incorporates both ferric (Fe³⁺) and ferrous (Fe²⁺) iron in its crystal structure. It has been proposed that amphibole Fe³⁺/Fe^T ratios can record the Fe³⁺/Fe^Tratios, and thus magmatic oxygen fugacity, of the melt from which they crystallized. Thus, making amphibole a promising tool to study the redox state of arc magmas. 

Vita: Barbara Ratschbacher is a Researcher in the Polar Geology group at the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) in Hannover since 2025. Her research focuses on better understanding the temporal, spatial, and chemical evolution of crustal magmatism particularly in subduction zone settings. Barbara obtained a PhD from the University of Southern California in 2017. She was a postdoctoral scholar at the California Institute of Technology until 2020 and worked at the University of California Davis until 2024. 

Link to webpage

Invited by:  Harry Becker

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