Cécile Deligny

@article{Fri_etal2021,

title = {In situ quantification of the nitrogen content of olivine-hosted melt inclusions from Klyuchevskoy volcano (Kamchatka) : Implications for nitrogen recycling at subduction zones},

author = {E. F\"{u}ri and M. Portnyagin and N. Mironov and C. Deligny and A. Gurenko and R. Botcharnikov and F. Holtz},

doi = {10.1016/j.chemgeo.2021.120456},

year  = {2021},

date = {2021-01-01},

journal = {Chemical Geology},

volume = {582},

pages = {120456},

abstract = {Assessing the N content of arc magmas and their mantle source remains a challenge because the volatile element composition of melts and gases can be modified during magma ascent, storage, and eruption. Given that melt inclusions (MIs) in Mg-rich olivine represent the best proxies for primary arc melts, we applied, for the first time, an in situ high-resolution secondary ion mass spectrometry (SIMS) method to determine the N concentration in olivine-hosted MIs from Klyuchevskoy volcano in Kamchatka. To reverse the effects of post-entrapment modification processes (i.e., exsolution of volatiles into a fluid bubble), the MIs were partially to completely homogenized at high temperatures (1150--1400 ◦C) and pressures ranging from 0.1 to 500 MPa under dry to H2Osaturated conditions at variable oxygen fugacities (CCO to QFM + 3.3). After the experiments, N concentrations in water-rich MI glasses correlate positively with H2O and CO2 contents as well as with N/CO2 ratios, and negatively with the volume of the remaining fluid bubble. Glasses of completely homogenized (fluid bubble-free) MIs contain up to 25.7 textpm 0.5 ppm N, whereas glasses of three unheated (natural, bubble-bearing) MIs have significantly lower N concentrations of 1 textpm 0.3 ppm. The N-CO2-Nb characteristics of completely homogenized MIs indicate that melts feeding Klyuchevskoy volcano have high absolute concentrations of both N and CO2, as well as large excess of these volatiles relative to Nb, compared to primary mid-ocean ridge melts. This implies that large amounts of N and CO2 in Klyuchevskoy melts and their mantle source are derived from the subducting slab, and that these subducted volatiles are (partially) returned to the crust and atmosphere by arc-related magmatism.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dalou_etal2019,

title = {Redox control on nitrogen isotope fractionation during planetary core formation},

author = {C. Dalou and E. F\"{u}ri and C. Deligny and L. Piani and G. Caumon and B. Laumonier and J. Boulliung and M. Ed\'{e}n},

doi = {10.1073/pnas.1820719116},

year  = {2019},

date = {2019-01-01},

journal = {Proceedings of the National Academy of Sciences of the United States of America},

abstract = {The present-day nitrogen isotopic compositions of Earthtextquoterights surficial (15N-enriched) and deep reservoirs (15N-depleted) differ significantly. This distribution can neither be explained by modern mantle degassing nor recycling via subduction zones. As the effect of planetary differentiation on the behavior of N isotopes is poorlyunderstood, we experimentally determined N-isotopic fractionations during metal--silicate partitioning (analogous to planetary core formation) over a large range of oxygen fugacities ($Delta$IW −3.1 \< logfO2 \< $Delta$IW −0.5, where $Delta$IW is the logarithmicdifference between experimental oxygen fugacity [fO2] conditions and that imposed by the coexistence of iron and wüstite) at 1 GPa and 1,400 textdegreeC. We developed an in situ analytical method to measure the N-elemental and -isotopic compositions of experimental run products composed of Fe--C--N metal alloys and basaltic melts.Our results show substantial N-isotopic fractionations between metal alloys and silicate glasses, i.e., from −257 textpm 22texttenthousand to −49 textpm 1texttenthousand over 3 log units of fO2. These large fractionations under reduced conditions can be explained by the large difference between N bonding in metal alloys (Fe--N) and in silicate glasses (asmolecular N2 and NH complexes). We show that the $delta$15N value of the silicate mantle could have increased by �`u20texttenthousand during core formation due to N segregation into the core.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}