Pathways and Processes of Ocean-Crust-Mantle Nitrogen Cycling

氮同位素系统在追踪有机组分从地表/近地表向地球深部的迁移方面显示出巨大的潜力。研究有机氮在地壳和地幔中的结合和再分配过程是理解现代地幔-海洋挥发物再循环和长期地球脱气和大气演化的关键。 然而，缺乏有关流体和矿物之间的N同位素分馏的信息限制了流体-岩石相互作用及其对大规模N循环的影响的任何定量建模。在这个项目中，P.I.和他的研究生将实验研究云母流体N同位素分馏在一个温度范围内适合脱挥发分和部分熔融，并研究海洋到岩石圈转移的有机N的重要途径，包括沉积岩的部分熔融和以前在海底热液蚀变的玄武岩的深俯冲。这项研究将利用一种载气，利哈伊大学最近开发了一种基于N-S的分析系统，用于分析从硅酸盐矿物和岩石中提取的极少量的N。P.I.正在开发的方法该实验室将促进氮同位素在地球科学学科（特别是研究生物圈-地圈界面的学科）和宇宙化学中的更广泛应用。

The nitrogen (N) isotope system shows great potential for tracing the transfer of organic components from the surface/near-surface realm into the deeper Earth. Study of the processes by which organic N is incorporated into and redistributed within the crust and mantle is key to understanding modern mantle-ocean volatiles recycling and longer-term Earth degassing and atmosphere evolution. However, the lack of information regarding fractionation of N isotopes among fluids and minerals limits any quantitative modeling of fluid-rock interactions and their impact on larger-scale N cycling. In this project, the P.I. and his graduate students will experimentally investigate mica-fluid N isotope fractionation over a range of temperatures appropriate for devolatilization and partial melting, and examine important pathways for the ocean-to-lithosphere transfer of organic N, including partial melting of sedimentary rocks and the deep subduction of basaltic rocks previously hydrothermally altered on the seafloor.This study will utilize a carrier-gas-based analytical system recently developed at Lehigh University for analyses of extremely small amounts of N extracted from silicate minerals and rocks. The methods being developed in the P.I.'s laboratory could facilitate wider application of N isotopes in earth science disciplines (particularly those examining the biosphere-geosphere interface) and in cosmochemistry.