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Smith Lecture: Probing Surface-Interior Mass Exchange in the Earth Using Nitrogen

Ananya Mallik, University of Arizona
Friday, October 30, 2020
3:30-4:30 PM
Virtual
Zoom Meeting ID: 97208617457
Volatile exchange between the Earth’s surficial and deeper reservoirs due to subduction determines the dynamics and evolution of the reservoirs through geological time. In spite of being a ubiquitous volatile element in the Earth and abundantly present in the Earth’s mantle, the behavior of nitrogen (N) in the mantle and exchange of N between the surficial and deeper terrestrial reservoirs have only gained attention recently. Previous studies have estimated the recycling efficiency of N (the percentage of incoming N in subduction zones surviving the arc filter and entering the deep mantle) by difference of incoming and volcanic outgassing fluxes; these have obtained disparate estimates ranging between 0% to 80-92%. Also, such an approach ignores the possibility that a fraction of the N released from the subducted slab may not be outgassed but rather sequestered in the overriding plate. Here I empirically constrain the recycling efficiency of N by focusing on the mechanism of N transfer from slabs by aqueous fluids and/or hydrous partial melts, addressing a broad range of thermal regimes applicable in modern-day subduction zones. I find that globally 45-74% of incoming N in subduction zones survives past the arc magmatism filter and enters the deep mantle. I will briefly discuss the possible implications of such recycling efficiency on the evolution of the atmosphere and the mantle through time.
Building: Off Campus Location
Location: Virtual
Event Link:
Event Type: Lecture / Discussion
Tags: Lecture
Source: Happening @ Michigan from Earth and Environmental Sciences