Eclogites, “Arclogites” and the Oxidation State of the Continental Crust

Geosciences Colloquium Speaker Series
Megan Elizabeth Holycross, Assistant Professor
Cornell University

4:00 - 5:00 p.m.
22 Deike Building
Zoom link: https://psu.zoom.us/j/93577641760?pwd=b0RMS3ZtNjJMWWR5QldUSnlMc3FUZz09 

Summary:
Arc magmas, the building blocks of continental crust, are depleted in total Fe, have higher ratios of oxidized iron to total iron (Fe3+/∑Fe) and record higher oxygen fugacities (fO2) compared to magmas erupted at mid-ocean ridges. Melting of garnet-bearing eclogites on the subducting slab or crystallization of deep garnet pyroxenites (“arclogites”) could explain these observations if Fe2+, but not Fe3+, is compatible in garnet, yet this model for continental crust generation has never been tested experimentally. In this talk I’ll detail the results of a series of experiments to measure the partitioning of Fe-species between garnet and silicate melts to determine the contributions of both high-pressure cumulate crystallization in thick-crusted arcs and melting of subducted oceanic crust in creating Fe-depleted, oxidized arc magmas.
 
About Megan:
Megan Elizabeth Holycross joined Cornell’s Department of Earth and Atmospheric Sciences in July 2020 as an assistant professor. Her research seeks to understand the processes that have differentiated the chemistry of Earth’s solid interior, mostly through laboratory experiments. Prior to joining Cornell, Megan was a National Science Foundation Postdoctoral Fellow with appointments at the Smithsonian Institution and Yale University.