The Fe-C-O-H-N system at 6.3-7.8 GPa and 1200-1400 degrees C: implications for deep carbon and nitrogen cycles

The Fe-C-O-H-N system at 6.3-7.8 GPa and 1200-1400 degrees C: implications for deep carbon and nitrogen cycles Full article

Journal

Contributions to Mineralogy and Petrology
ISSN: 0010-7999 , E-ISSN: 1432-0967

Output data

Year: 2018, Volume: 173, Number: 6, Article number : UNSP 47, Pages count : DOI: 10.1007/s00410-018-1472-3

Tags

Mantle; Metal; Fluid; Carbon; Nitrogen; Hydrocarbons; Gas chromatography-mass spectrometry

Authors

Sokol Alexander G. ^1,2 , Tomilenko Anatoly A. ¹ , Bul'bak Taras A. ¹ , Kruk Alexey N. ^1,2 , Zaikin Pavel A. ³ , Sokol Ivan A. ¹ , Seryotkin Yurii V. ^1,2 , Palyanov Yury N. ^1,2

Affiliations

1	(Данные Web of science) Russian Acad Sci, Siberian Branch, VS Sobolev Inst Geol & Mineral, 3 Koptyug Ave, Novosibirsk 630090, Russia
2	(Данные Web of science) Novosibirsk State Univ, 2 Pirogov Str, Novosibirsk 630090, Russia
3	(Данные Web of science) Russian Acad Sci, Siberian Branch, NN Vorozhtsov Novosibirsk Inst Organ Chem, 9 Lavrentiev Ave, Novosibirsk 630090, Russia

Interactions in a Fe-C-O-H-N system that controls the mobility of siderophile nitrogen and carbon in the Fe-0-saturated upper mantle are investigated in experiments at 6.3-7.8 GPa and 1200-1400 A degrees C. The results show that the gamma-Fe and metal melt phases equilibrated with the fluid in a system unsaturated with carbon and nitrogen are stable at 1300 A degrees C. The interactions of Fe3C with an N-rich fluid in a graphite-saturated system produce the epsilon-Fe3N phase (space group P6(3)/mmc or P6(3)22) at subsolidus conditions of 1200-1300 A degrees C, while N-rich melts form at 1400 A degrees C. At IW- and MMO-buffered hydrogen fugacity (fH(2)), fluids vary from NH3- to H2O-rich compositions (NH3/N-2 > 1 in all cases) with relatively high contents of alkanes. The fluid derived from N-poor samples contains less H2O and more carbon which mainly reside in oxygenated hydrocarbons, i.e., alcohols and esters at MMO-buffered fH(2) and carboxylic acids at unbuffered fH(2) conditions. In unbuffered conditions, N-2 is the principal nitrogen host (NH3/N-2 ae<currency> 0.1) in the fluid equilibrated with the metal phase. Relatively C- and N-rich fluids in equilibrium with the metal phase (gamma-Fe, melt, or Fe3N) are stable at the upper mantle pressures and temperatures. According to our estimates, the metal/fluid partition coefficient of nitrogen is higher than that of carbon. Thus, nitrogen has a greater affinity for iron than carbon. The general inference is that reduced fluids can successfully transport volatiles from the metal-saturated mantle to metal-free shallow mantle domains. However, nitrogen has a higher affinity for iron and selectively accumulates in the metal phase, while highly mobile carbon resides in the fluid phase. This may be a controlling mechanism of the deep carbon and nitrogen cycles.

Sokol A.G. , Tomilenko A.A. , Bul'bak T.A. , Kruk A.N. , Zaikin P.A. , Sokol I.A. , Seryotkin Y.V. , Palyanov Y.N.
The Fe-C-O-H-N system at 6.3-7.8 GPa and 1200-1400 degrees C: implications for deep carbon and nitrogen cycles
Contributions to Mineralogy and Petrology. 2018. V.173. N6. UNSP 47 . DOI: 10.1007/s00410-018-1472-3 WOS Scopus РИНЦ

Published online:	May 21, 2018
Published print:	Jun 1, 2018

Web of science	WOS:000433207600002
Scopus	2-s2.0-85047405082
Elibrary	35514307
OpenAlex	W2803281966