Nitrogen incorporation in silicates and metals: results from SIMS, EPMA, FTIR, and laser-extraction mass spectrometry

Jed L Mosenfelder1, Annette von der Handt1, Evelyn Füri2, Celia Dalou1,2, Richard L Hervig3, George R. Rossman4, Marc M. Hirschmann1

1Department of Earch Sciences, University of Minnesota, Minneapolis, Minnesota, 55455

2Centre de Recherches Pétrographiques et Géochimiques, CNRS-UL, 54501 Vandœuvre-lès Nancy,France

3Schoolof Earth & Space Exploration, Arizona State University, Tempe, AZ 8528701404

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, USA 91125-2500


A quantative understanding of nitrogen incorporation in Earth materials is important for constraining volatile evolution in planetary bodies. We used a combination of chemical (SIMS< EPMA, and laser-extraction mass spectrometry) and spectroscopic (FTIR) data to study nitrogen contents and speciation mechanisms in silicate glasses, metal alloys, and a N-bearing silicate mineral (hyalophane). One suite of Fe-free basaltic glasses was studied by all four methods. Concentrations of N in these glasses determined by EMPA are systematically higher than those measured by laser extraction, but agree within mutual 2 sigma uncertainties, demonstrating the general veracity of the EPMA method. SIMS calibrations based on measurement of 14N+ and 14N16O- as a function of N content determined by EPMA (or laser extraction) are best fit with exponential curves rather than the linear regressions that are most commonly applied to SIMS data. On the other hand, a calibration based on 12C14N-  for C-poor, Fe-free glasses is exceptionally well fit to a linerar regression (r2 = 1), in contrast to expectations from previous work on glasses with lower N contents. Matrix effects associated with Fe or H2O content are ot justified by the SIMS data, but volatile data (both N and H) for hyalophane, which contains 20 wt% BaO, reveal matrix effects possibly induced by its high average molar mass. A combination of FTIR and chemical data, together with a thorough review of the literature, was used to determine incorpation mechanisms for N in the Fe-free glasses. We infer that under reducing conditions at high pressure and temperature N is dissolved in basaltic melts chierly as NH2- and NH2- with N2 and/or nitride (X-N3-) complexes becoming increasingly important at lof fO2, increasing N content, and decreasing H content. Our results have implicationsf for future studies seeking to accurately measure N by SIMS and for studies of N partitioning at high pressure relevant to planetary accretion and differentiation.