The fate of ammonium in phengite at high temperature

Yang, Yongying; Busigny, Vincent; Wang, Zhongping; Xia, Qunke

doi:10.2138/am-2017-6094

Cited by 14 publications

(22 citation statements)

References 73 publications

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“…4a) observed here reflects the lengthening of the N-H interatomic distance of the NH + 4 molecule with increasing T up to 600 • C. This expansion is reversible upon cooling back to room temperature. Similar shifting to lower wave numbers and lengthening of the N-H bond was also observed in the in situ T -dependent study performed by Yang et al (2017) but only up to 500 • C on natural samples containing few parts per million of NH + 4 . At T s higher than 500 • C, they observed no further N-H bond lengthening and they proposed that one hydrogen atom is detached from the NH + 4 molecule and linked to one of the basal oxygen atoms in the tetrahedral sheets, initiating the devolatilisation processes.…”

Section: In Situ High-p Ftir Spectroscopysupporting

confidence: 82%

“…Furthermore, we studied its vibrational response to compression up to 42 GPa at ambient T in diamond anvil cell (DAC) experiments. These data are compared with recent studies on the devolatilisation of natural phengite containing trace amounts of NH + 4 (Liu et al, 2019;Yang et al, 2017) and with our own experimental results as well as with existing data (Goryainov et al, 2017;Zhang et al, 2010) on the dehydration of synthetic and natural ammonium-free phengite. NH 4 -endmember phengite is not reported from natural rocks so far.…”

Section: Introductionmentioning

confidence: 72%

“…The splitting of the NH + 4 −ν 3 stretching and NH + 4 −ν 4 bending vibrations at 3291 and 1430 cm −1 respectively with decreasing T observed here in in situ experiments (Figs. 3, 4a, S2 and S3) has also been observed at low T s in the IR spectra of other NH + 4 -bearing micas like synthetic tobelite (Mookherjee et al, 2002a), synthetic phlogopite (Mookherjee et al, 2002b) and in natural NH + 4 -bearing phengites (Yang et al, 2017). This splitting as well as the sharpening of the NH + 4 −ν 3 , ν 4 , the overtone (2ν 4 ) and the combination bands (ν 2 + ν 4 ) is attributed by the formerly mentioned studies to a low-T ordering process of the NH + 4 molecule based on the proposal by Pauling (1930), who first suggested such orientational ordering of tetrahedral molecules (like NH + 4 ) and the possibility of its transition from free rotation on cooling.…”

Section: In Situ High-p Ftir Spectroscopymentioning

confidence: 80%

“…Previous studies of NH 4 -bearing silicates (e.g. Busigny et al, 2003;Liu et al, 2019;Vennari et al, 2017;Watenphul et al, 2009;Wunder et al, 2015;Yang et al, 2017) show that the band at 3610 cm −1 is assigned Table 1. Lattice parameters of the main NH 4 -phengite (Ph) polytypes produced in different runs (NAD1 and NAD2), calculated from Rietveld refinements.…”

Section: Ambient Ftir Spectroscopymentioning

confidence: 98%

“…This decrease in the integral absorbance of the NH + 4 −ν 3 band despite no loss of NH + 4 can be explained by (i) the NH + 4 molecule in the interlayer cation site getting disordered with increasing T and/or (ii) a T -induced decrease in the molar extinction coefficient of the NH + 4 molecule. Yang et al (2017) has assigned this to a change in molar extinction coefficient 2 with T . We, both looking at the whole T -dependent spectral series from −180 to 600 • C and observing the reversible expansion of the NH + 4 molecule (discussed below), rather assign this to a Tdependent order/disorder mechanism changing/reducing the local tetrahedral (T d ) symmetry of the NH + 4 molecule and additionally changing the molar extinction coefficient.…”

Section: In Situ High-p Ftir Spectroscopymentioning

confidence: 99%

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In situ micro-FTIR spectroscopic investigations of synthetic ammonium phengite under pressure and temperature

et al. 2020

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Abstract. Phengite is known to be an important mineral in the transport of alkalis and water to upper mantle depths. Since ammonium (NH4+) can substitute for K+ in K-bearing minerals, phengite is thus a potential host to transport nitrogen into the mantle. However, the temperature and pressure conditions at which devolatilisation of NH4-bearing phengite occurs are not well constrained. In this study, NH4-phengite (NH4)(Mg0.5Al1.5)(Al0.5Si3.5)O10(OH)2 was synthesised in piston-cylinder experiments at 700 ∘C and 4.0 GPa. Its devolatilisation behaviour was studied by means of in situ micro-FTIR (Fourier transform infrared) spectroscopy under low and high temperatures from −180 up to 600 ∘C at ambient pressure using a Linkam cooling–heating stage and pressures up to 42 GPa at ambient temperature in diamond anvil cell (DAC) experiments. In addition to these short-term in situ experiments, we performed quenched experiments where the samples were annealed for 24 h at certain temperatures and analysed at room conditions by micro-FTIR spectroscopy. Our results can be summarised as follows: (1) an order–disorder process of the NH4+ molecule takes place with temperature variation at ambient pressure; (2) NH4+ is still retained in the phengite structure up to 600 ∘C, and the expansion of the NH4+ molecule with heating is reversible for short-term experiments; (3) kinetic effects partly control the destabilisation of NH4+ in phengite; (4) ammonium loss occurs at temperatures near dehydration; (5) NH4+ in phengite is apparently distorted above 8.6 GPa at ambient temperature; and (6) the local symmetry of the NH4+ molecule is lowered/descended/reduced by increasing pressure (P) or decreasing temperature (T), and the type and mechanism of this lowered symmetry is different in both cases. The current study confirms the wide stability range of phengite and its volatiles and thus has important implications for the recycling of nitrogen and hydrogen into the deep Earth. Moreover, it is considered as a first step in the crystallographic determination of the orientation of the NH4+ molecule in the phengite structure.

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Section: In Situ High-p Ftir Spectroscopysupporting

confidence: 82%

Section: Introductionmentioning

confidence: 72%

Section: In Situ High-p Ftir Spectroscopymentioning

confidence: 80%

Section: Ambient Ftir Spectroscopymentioning

confidence: 98%

Section: In Situ High-p Ftir Spectroscopymentioning

confidence: 99%

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In situ micro-FTIR spectroscopic investigations of synthetic ammonium phengite under pressure and temperature

et al. 2020

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Earth’s Nitrogen and Carbon Cycles

Halama

Bebout

2021

Space Sci Rev

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Understanding the Earth’s geological nitrogen (N) and carbon (C) cycles is fundamental for assessing the distribution of these volatiles between solid Earth (core, mantle and crust), oceans and atmosphere. This Special Communication about the Earth’s N and C cycles contains material that is relevant for researchers who are interested in the Topical Collection on planetary evolution “Reading Terrestrial Planet Evolution in Isotopes and Element Measurements”. Variations in the fluxes of N and C between these major reservoirs through geological time influenced the evolution and determined the unique composition of the Earth’s atmosphere. Here we review several key geological aspects of the N and C cycles of which our understanding has significantly advanced during the last decade through field-based, experimental and theoretical studies. Subduction zones are the most important pathway of both N and C from the Earth’s surface into the deep Earth. A key question in the flux quantification is how much of the volatile elements is stored in the downgoing slab and introduced into the mantle and how much is returned back to the surface and the atmosphere through arc magmatism. For N, the retention of N as $\text{NH}_{4}^{+}$ NH 4 + in minerals has a major influence on fluxes between reservoirs. The temperature-dependent stability of $\text{NH}_{4}^{+}$ NH 4 + -bearing minerals determines whether N is predominantly retained in the slab to mantle depths (in subduction zones with a low geothermal gradient) or devolatilized (in subduction zones with a high geothermal gradient). Several lines of evidence suggest that the mantle is regassing with respect to N due to a net influx of subducted N over time, but this issue is highly debated and evidence to the contrary also exists. Nevertheless, there is consensus that the majority of the planetary N budget is stored in the Earth’s mantle, with the continental crust also constituting a significant N reservoir. For C, release from the subducting slab occurs through decarbonation reactions, dissolution and formation of carbonatitic liquids, but reprecipitation of C in the slab or the forearc mantle wedge may limit the effectiveness of direct return of C into the atmosphere. Carbon release through regional metamorphism in collision zone orogens also has potentially profound effects on C release into the atmosphere and consensus has emerged that such orogens are sources rather than sinks of atmospheric CO2. On shorter timescales, contact metamorphism through interaction of mantle-derived magmas with C-bearing country rocks, and the resulting release of large quantities of CH4 and/or CO2, has been linked to global warming events.

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Ammonium Impacts on Vibrations of Hydroxyl and Lattice of Phengite at High Temperature and High Pressure

Huang

Yang

et al. 2021

J. Earth Sci.

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The fate of ammonium in phengite at high temperature

Cited by 14 publications

References 73 publications

In situ micro-FTIR spectroscopic investigations of synthetic ammonium phengite under pressure and temperature

In situ micro-FTIR spectroscopic investigations of synthetic ammonium phengite under pressure and temperature

Earth’s Nitrogen and Carbon Cycles

Ammonium Impacts on Vibrations of Hydroxyl and Lattice of Phengite at High Temperature and High Pressure

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