Japan Geoscience Union Meeting 2018

Presentation information

[EE] Oral

S (Solid Earth Sciences) » S-GC Geochemistry

[S-GC45] Volatile Cycles in the Deep Earth - from Subduction Zone to Hot Spot

Mon. May 21, 2018 1:45 PM - 3:15 PM A05 (Tokyo Bay Makuhari Hall)

convener:Yuji Sano(Division of Ocean and Earth Systems, Atmosphere and Ocean Research Institute, University of Tokyo), Takeshi Hanyu(Japan Agency for Marine-Earth Science and Technology, Department of Solid Earth Geochemistry), Hirochika Sumino(東京大学大学院総合文化研究科広域科学専攻相関基礎科学系), Chairperson:Sano Yuji, Sumino Hirochika

2:40 PM - 3:00 PM

[SGC45-04] Deep nitrogen recycling enhanced by seamount subduction of the Costa Rican arc

★Invited Papers

*Hyunwoo Lee1,2, Yuji Sano2, Tobias Fischer3 (1.Seoul National University, 2.Atmosphere and Ocean Research Institute, The University of Tokyo, 3.University of New Mexico)

Keywords:Nitrogen recycling, Subduction, Mantle

Sedimentary nitrogen recycling via subduction processes is considered efficient in the Central America margin. Massive addition of subducted nitrogen past the zones of arc magma generation other locations is also explained by mass balance considerations and nitrogen contents of high pressure metamorphic rocks. We measured nitrogen isotope compositions (δ15N), gas contents, and noble gas compositions of forearc and arc front springs in Costa Rica. The δ15N values (−4.4 to 1.6‰) of forearc springs at 9–11 N° are consistent with previously reported δ15N values in volcanic centers (−3.0 to 1.9‰). The δ15N values of emitted volcanic front gases (9–11 N°) imply less subducted pelagic sediment input relative to to the Nicaraguan section. According to the results, the structure of the incoming plate has a profound effect on the extent of nitrogen subduction into the mantle. We suggest that subduction erosion enhanced by abundant seamount subduction at 9–11 N° introduces overlying plate materials into the Costa Rican subduction zone. This process supports the recycling of heavier N into the deep mantle in the Costa Rican arc.