Nitrogen recycling at the Costa Rican subduction zone: The role of incoming plate structure

作者：Lee Hyunwoo^*; Fischer Tobias P; Maarten de Moor J; Sharp Zachary D; Takahata Naoto; Sano Yuji

来源：Scientific Reports, 2017, 7(1): 13933.

DOI：10.1038/s41598-017-14287-y

Efficient recycling of subducted sedimentary nitrogen (N) back to the atmosphere through arc volcanism has been advocated for the Central America margin while at other locations mass balance considerations and N contents of high pressure metamorphic rocks imply massive addition of subducted N to the mantle and past the zones of arc magma generation. Here, we report new results of N isotope compositions with gas chemistry and noble gas compositions of forearc and arc front springs in Costa Rica to show that the structure of the incoming plate has a profound effect on the extent of N subduction into the mantle. N isotope compositions of emitted arc gases (9-11 N degrees) imply less subducted pelagic sediment contribution compared to farther north. The N isotope compositions (delta N-15 = -4.4 to 1.6 parts per thousand) of forearc springs at 9-11 N degrees are consistent with previously reported values in volcanic centers (delta N-15 = -3.0 to 1.9 parts per thousand). We advocate that subduction erosion enhanced by abundant seamount subduction at 9-11 N degrees introduces overlying forearc crustal materials into the Costa Rican subduction zone, releasing fluids with lighter N isotope signatures. This process supports the recycling of heavier N into the deep mantle in this section of the Central America margin.

• 出版日期2017-10-24