Presented By: Earth and Environmental Sciences
Smith Lecture: Probing Surface-Interior Mass Exchange in the Earth Using Nitrogen
Ananya Mallik, University of Arizona
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.
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.
Livestream Information
ZoomOctober 30, 2020 (Friday) 3:30pm
Meeting ID: 97208617457
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