The oxygen fugacity at which graphite or diamond forms from carbonate-bearing melts in eclogitic rocks

  • V. Stagno
  • D. J. Frost
  • C. A. McCammon
  • H. Mohseni
  • Y. Fei
Original Paper


The oxygen fugacity (fO2) at which carbonate-bearing melts are reduced to either graphite or diamond in synthetic eclogite compositions has been measured in multi-anvil experiments performed at pressures between 3 and 7 GPa and temperatures between 800 and 1,300 °C using iron–iridium and iron–platinum alloys as sliding redox sensors. The determined oxygen fugacities buffered by the coexistence of elemental carbon and carbonate-bearing melt are approximately 1 log unit below thermodynamic calculations for a similar redox buffering equilibrium involving only solid phases. The measured oxygen fugacities normalized to the fayalite–magnetite–quartz oxygen buffer decrease with temperature from ~−0.8 to ~−1.7 log units at 3 GPa, most likely as a result of increasing dilution of the carbonate liquid with silicate. The normalized fO2 values also decrease with pressure and show a similar decrease with temperature at 6 GPa from ~−1.5 log units at 1,100 °C to ~−2.4 log units at 1,300 °C. In contrast to previous arguments, the stability field of the carbonate-bearing melt extends to lower oxygen fugacity in eclogite rocks than in peridotite rocks, which implies a wider range of conditions over which carbon remains mobile in natural eclogites. The raised prevalence of diamonds in eclogites compared to peridotites may, therefore, reflect more effective scavenging of carbon by melts in these rocks. The ferric iron contents of monomineralic layers of clinopyroxene and garnet contained in the same experiments were also measured using Mössbauer spectroscopy. A preliminary model was derived for determining the fO2 of eclogitic rocks from the compositions of garnet and clinopyroxene, including the Fe3+/ΣFe ratio of garnet, using the equilibrium,
$$\mathop { 5 {\text{CaFeSi}}_{2} {\text{O}}_{6} }\limits_{\text{cpx}} + \mathop {1/3{\text{Ca}}_{3} {\text{Al}}_{2} {\text{Si}}_{3} {\text{O}}_{12} }\limits_{\text{garnet}} + {\text{O}}_{2} = \mathop { 2 {\text{Ca}}_{3} {\text{Fe}}_{2} {\text{Si}}_{3} {\text{O}}_{12} }\limits_{\text{garnet}} + \mathop {1/3{\text{Fe}}_{3} {\text{Al}}_{2} {\text{Si}}_{3} {\text{O}}_{12} }\limits_{\text{garnet}} + \mathop {4{\text{SiO}}_{2} }\limits_{\text{coesite}}$$
The model, which reproduces the independently determined fO2 of the experimental data to within 0.5 log units, can be used to estimate the fO2 of ultrahigh-pressure metamorphic eclogites and cratonic eclogitic xenoliths. Although there are very few analyses of garnet Fe3+/ΣFe ratios from eclogite samples, the range in fO2 recorded by available eclogitic xenoliths is similar to that reported for peridotitic xenoliths and generally within the graphite/diamond stability field. Estimates for the average bulk Fe3+/ΣFe ratio of modern basaltic oceanic crust, however, are higher than the values for most of these xenoliths, and upon subduction, crustal carbon is likely to remain in the carbonate stability field to depths of at least 250 km. If eclogite xenoliths originated from subducted oceanic crust, then their generally lower fO2 most likely reflects either lower initial basaltic Fe3+/ΣFe ratios, loss of Fe2O3 through partial melting or the initial presence of organic carbon.


Eclogite Redox Carbonatitic melt Diamond Ferric iron Oxy-thermobarometer Subduction 



V.S. gratefully acknowledges financial support from DFG through the grant “FR1555/5-1” and from the WDC Research Fund at the Geophysical Laboratory. This study was also partially supported by the ERC advanced grant “DEEP” (227893) and by the Alfred P. Sloan Foundation’s Deep Carbon Observatory (DMGC). We thank H. Schülze for sample preparation for Mössbauer measurements. We acknowledge thoughtful comments from the editor C. Ballhaus and A. Rohrbach that improved the quality of our manuscript.

Supplementary material

410_2015_1111_MOESM1_ESM.doc (46 kb)
Supplementary material 1 (DOC 46 kb)
410_2015_1111_MOESM2_ESM.xls (282 kb)
Supplementary material 2 (XLS 282 kb)


  1. Ballhaus C, Berry RF, Green DH (1991) High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle. Contrib Miner Petrol 107:27–40CrossRefGoogle Scholar
  2. Bezos A, Humler E (2005) The Fe3+/ΣFe ratios of MORB glasses and their implications for mantle melting. Geochim Cosmochim Acta 69(3):711–725CrossRefGoogle Scholar
  3. Bianchini G, Beccaluva L, Bonadiman C, Nowell GM, Pearson DG, Siena F, Wilson M (2010) Mantle metasomatism by melts of HIMU piclogite components: new insights from Fe–lherzolite xenoliths (Calatrava Volcanic District, Central Spain). Lond Geol Soc Spec Publ 337:107–124CrossRefGoogle Scholar
  4. Canil D, O’Neill H, Pearson DG, Rudnick RL, McDonough WF, Carswell DA (1994) Ferric iron in peridotites and mantle oxidation states. Earth Planet Sci Lett 123(1–4):205–220CrossRefGoogle Scholar
  5. Cartigny P (2005) Stable isotopes and diamond origins. Elements 1:79–84CrossRefGoogle Scholar
  6. Cartigny P, Harris JW, Javoy M (1998) Eclogitic diamond formation at Jwaneng: no room for a recycled component. Science 280:1421–1424CrossRefGoogle Scholar
  7. Dasgupta R, Hirschmann MM (2010) The deep carbon cycle and melting in Earth’s interior. Earth Planet Sci Lett (Front) 298:1–13CrossRefGoogle Scholar
  8. Dasgupta R, Hirschmann MM, Withers AC (2004) Deep global cycling of carbon constrained by the solidus of anhydrous, carbonated eclogite under upper mantle conditions. Earth Planet Sci Lett 227:73–85CrossRefGoogle Scholar
  9. Dasgupta R, Hirschmann MM, Dellas N (2005) The effect of bulk composition on the solidus of carbonated eclogite from partial melting experiments at 3 GPa. Contrib Miner Petrol 149:288–305CrossRefGoogle Scholar
  10. Dasgupta R, Hirschmann MM, Stalker K (2006) Immiscible transition from carbonate-rich to silicate-rich melts in the 3 GPa melting interval of eclogite + CO2 and genesis of silica-undersaturated ocean island lavas. J Petrol 47(4):647–671CrossRefGoogle Scholar
  11. Dasgupta R, Mallik A, Tsuno K, Withers AC, Hirth G, Hirschmann MM (2013) Carbon-dioxide-rich silicate melt in the Earth’s upper mantle. Nature 493:211–215CrossRefGoogle Scholar
  12. Eggler DH, Baker DR (1982) Reduced volatiles in the system C–O–H: implications to mantle melting, fluid formation, and diamond genesis. High-Press Res Geophys 12:237–250Google Scholar
  13. Elkins LJ, Sims KWW, Prytulak J, Elliot T, Mattielli N, Blichert-Toft J, Blusztajn J, Dunbar N, Devey C, Mertz DF, Schilling JG, Murrell M (2011) Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses. Geochim Cosmochim Acta 75:6300–6329CrossRefGoogle Scholar
  14. Ellis DJ, Green DH (1979) An experimental study of the effect of Ca upon garnet-clinopyroxene Fe–Mg exchange equilibria. Contrib Miner Petrol 71:13–22CrossRefGoogle Scholar
  15. Evans KA (2012) The redox budget of subduction zones. Earth-Sci Rev 113:11–32CrossRefGoogle Scholar
  16. Fabrichanaya O, Saxena SK, Richet P, Westrum EF (eds) (2004) Thermodynamic data, models and phase diagrams in multicomponent oxide systems. Springer, BerlinGoogle Scholar
  17. Frost DJ, Poe BT, Tronnes RG, Liebske C, Duba A, Rubie DC (2004) A new large-volume multianvil system. Phys Earth Planet Int 143–144:507–514CrossRefGoogle Scholar
  18. Ganguly J, Cheng C, Tirone M (1996) Thermodynamics of aluminosilicate garnet solid solutions: new experimental data, an optimized model, and thermometric applications. Contrib Mineral Petrol 126:137–151CrossRefGoogle Scholar
  19. Gréau Y, Huang JX, Griffin WL, Renac C, Alard O, O’Reilly SY (2011) Type I eclogites from Roberts Victor kimberlites: products of extensive mantle metasomatism. Geochim Cosmochim Acta 75(22):6927–6954CrossRefGoogle Scholar
  20. Gudmundsson G, Holloway JR (1993) Activity-composition relationships in the system Fe-Pt at 1300 & #xB0;C and 1400°C and at 1 atm and 20 kbar. Am Mineral 78:178–186Google Scholar
  21. Gudmundsson G, Wood BJ (1995) Experimental tests of garnet peridotite oxygen barometry. Contrib Mineral Petrol 119:56–67CrossRefGoogle Scholar
  22. Hammouda T (2003) High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle. Earth Planet Sci Lett 214:357–368CrossRefGoogle Scholar
  23. Holland T, Powell R (2011) An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids. J Metamorph Geol 29:333–383CrossRefGoogle Scholar
  24. Huang J-X, Gréau Y, Griffin WL, O’Reilly SY, Pearson NJ (2012) Multi-stage origin of Roberts Victor eclogites: progressive metasomatism and its isotopic effects. Lithos 142–143:161–181CrossRefGoogle Scholar
  25. Jacob DE (2004) Nature and origin of eclogite xenoliths from kimberlites. Lithos 77:295–316. doi: 10.1016/j.lithos.2004.03.038 CrossRefGoogle Scholar
  26. Kelley KA, Cottrell E (2012) The influence of magmatic differentiation on the oxidation state of Fe in a basaltic arc magma. Earth Planet Sci Lett 329–330:109–121CrossRefGoogle Scholar
  27. Kessel R, Beckett JR, Stolper EM (2003) Thermodynamic properties of the Pt–Fe system. Am Mineral 86:1003–1014Google Scholar
  28. Kiseeva ES, Yaxley GM, Hermann J, Litasov KD, Rosenthal A, Kamenetsky VS (2012) An experimental study of carbonated eclogite at 3.5-5.5 GPa—implications for silicate and carbonate metasomatism in the cratonic mantle. J of Petrology 53:727–759. doi: 10.1093/petrology/egr078 CrossRefGoogle Scholar
  29. Komabayashi T, Fei Y (2010) Internally consistent thermodynamic database for iron to the Earth’ s core conditions. J Geophys Res 115:B03202CrossRefGoogle Scholar
  30. Li YL, Zheng YF, Fu B (2005) Mossbauer spectroscopy of omphacite and garnet pairs from eclogites: application to geothermobarometry. Am Mineral 90:90–100CrossRefGoogle Scholar
  31. Liu Y, Taylor LA, Sarbadhikari AB, Valley JW, Ushikubo T, Spicuzza MJ, Kita N, Ketcham RA, Carlson W, Shatsky V, Sobolev NV (2009) Metasomatic origin of diamonds in the world’s largest diamondiferous eclogite. Lithos 112:1014–1024CrossRefGoogle Scholar
  32. Llovet X, Galan G (2003) Correction of secondary X-ray fluorescence near grain boundaries in electron microprobe analysis: application to thermobarometry of spinel lherzolites. Am Mineral 88:121–130Google Scholar
  33. Lowry D, Mattey DP, Harris JW (1999) Oxygen isotope composition of syngenetic inclusions in diamond from the Finsch Mine, RSA. Geochim Cosmochim Acta 63:1825–1836. doi: 10.1016/S0016-7037(99)00120-9 CrossRefGoogle Scholar
  34. Luth RW (1993) Diamonds, eclogites and the oxidation state of the Earth’s mantle. Science, New Series 261(5117):66–68Google Scholar
  35. Luth RW, Stachel T (2014) The buffering capacity of lithospheric mantle: implications for diamond formation. Contrib Mineral Petrol 168:1083. doi: 10.1007/s00410-014-1083-6 CrossRefGoogle Scholar
  36. Luth RW, Virgo D, Boyd FR, Wood BJ (1990) Ferric iron in mantle-derived garnets. Contrib Miner Petrol 104:56–72CrossRefGoogle Scholar
  37. Martin AM, Hammouda T (2011) Role of iron and reducing conditions on the stability of dolomite + coesite between 4.25 and 6 GPa—a potential mechanism for diamond formation during subduction. Eur J Mineral 23(1):5–16. doi: 10.1127/0935-1221/2010/0022-2067 CrossRefGoogle Scholar
  38. Matveev S, Ballhaus C, Fricke K, Trunckenbrodt J, Ziegenbein D (1997) CHO volatiles under upper mantle conditions. I. Experimental results. Geochim Cosmochim Acta 61:3081–3088CrossRefGoogle Scholar
  39. McCammon CA, Chinn LL, Gurney JJ, McCallum ME (1998) Ferric iron content of mineral inclusions in diamonds from George Creek, Colorado determined using Mossbauer spectroscopy. Contrib Mineral Petrol 133(1–2):30–37CrossRefGoogle Scholar
  40. O’Neill HStC (1987) Quartz–fayalite–iron and quartz–fayalite–magnetite equilibria and the free energies of formation of fayalite (Fe2SiO4) and magnetite (Fe3O4). Am Mineral 72:67–75Google Scholar
  41. Pertermann M, Hirschmann MM (2003) Anhydrous partial melting experiments on MORB-like eclogite: phase relations, phase compositions and mineral–melt partitioning of major elements at 2–3 GPa. J Petrol 44:2173–2201CrossRefGoogle Scholar
  42. Prescher C, McCammon C, Dubrovinsky L (2012) MossA—a program for analyzing energy-domain Mossbauer spectra from conventional and synchrotron sources. J Appl Crystallogr 45:329–331CrossRefGoogle Scholar
  43. Purwin H, Lauterbach S, Brey GP, Woodland AB, Kleebe HJ (2013) An experimental study of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the system CaO–FeO–Fe2O3–MgO–Al2O3–SiO2: implications for garnet–clinopyroxene geothermometry. Contrib Mineral Petrol 165:623–639CrossRefGoogle Scholar
  44. Rohrbach AC, Schmidt MW (2011) Redox freezing and melting in the Earth’s deep mantle resulting from carbon–iron redox coupling. Nature. doi: 10.1038/nature09899 Google Scholar
  45. Schulze DJ (1989) Constraints on the abundance of eclogite in the upper mantle. J Geophys Res 94:4205–4212CrossRefGoogle Scholar
  46. Schwerdtfeger K, Zwell L (1968) Activities in solid iridium–iron and rhodium–iron alloys at 1200 & #xB0;C. Trans Metall Soc AIME 242:631–633Google Scholar
  47. Shirey SB, Cartigny P, Frost DJ, Keshav S, Nestola F, Nimis P, Pearson DG, Sobolev NV, Walter MJ (2013) Diamonds and the geology of mantle carbon. In Hazen RM, Jones AP, Baross JA (eds) Carbon in earth, reviews in mineralogy and geochemistry, vol 75, pp 355–421. doi: 10.2138/rmg.2013.75.12
  48. Simakov SR (2006) Redox state and peridotites from sub-cratonic upper mantle and a connection with diamond genesis. Contrib Mineral Petrol 151:282–296CrossRefGoogle Scholar
  49. Smart KA, Chacko T, Stachel T, Tappe S, Stern RA, Ickert RB (2012) Eclogite formation beneath the northern Slave craton constrained by diamond inclusions: oceanic lithosphere origin without a crustal signature. Earth Planet Sci Lett 319–320:165–177CrossRefGoogle Scholar
  50. Smyth JR (1980) Cation vacancies and the crystal chemistry of breakdown reactions in kimberlitic omphacites. Am Mineral 65:1257–1264Google Scholar
  51. Snyder GA, Taylor LA, Jerde EA, Clayton RN, Mayeda TK, Deines P, Rossman GR, Sobolev NV (1995) Archean mantle heterogeneity and the origin of diamondiferous eclogites, Siberia: evidence from stable isotopes and hydroxyl in garnet. Am Mineral 80:799–809Google Scholar
  52. Sobolev VN, McCammon CA, Taylor LA, Snyder GA, Sobolev NV (1999) Precise Mossbauer milliprobe determination of ferric iron in rock-forming minerals and limitations of electron microprobe analysis. Am Mineral 84:78–85Google Scholar
  53. Sobolev AV, Hofmann AW, Kuzmin DV, Yaxley GM, Arndt NT, Chung SL, Danyushevsky LV, Elliott T, Frey FA, Garcia MO, Gurenko AA, Kamenetsky VS, Kerr AC, Krivolutskaya NA, Matvienkov VV, Nikogosian IK, Rocholl A, Sigurdsson IA, Sushchevskaya NM, Teklay M (2007) The amount of recycled crust in sources of mantle-derived melts. Science 316:412–417. doi: 10.1126/Science.1138113 CrossRefGoogle Scholar
  54. Stachel T, Harris JW (2008) The origin of cratonic diamonds—constraints from mineral inclusions. Ore Geol Rev 34(1–2):5–32CrossRefGoogle Scholar
  55. Stachel T, Harris JW (2009) Formation of diamonds in the Earth’s mantle. J PhysCondens Matter 21:364206CrossRefGoogle Scholar
  56. Stagno V, Frost DJ (2010) Carbon speciation in the asthenosphere: experimental measurements of the redox conditions at which carbonate-bearing melts coexist with graphite or diamond in peridotite assemblages. Earth Planet Sci Lett 30:72–84CrossRefGoogle Scholar
  57. Stagno V, Tange Y, Miyajima N, McCammon CA, Irifune T, Frost DJ (2011) The stability of magnesite in the transition zone and the lower mantle as function of oxygen fugacity. Geophys Res Lett 38:L19309CrossRefGoogle Scholar
  58. Stagno V, Dickson O, McCammon CA, Frost DJ (2013) The oxidation state of the mantle and the extraction of carbon from Earth’s interior. Nature 493:84–88. doi: 10.1038/nature11679 CrossRefGoogle Scholar
  59. Stosch HG, Lugmair GW (1990) Geochemistry and evolution of MORB-type eclogites from the Munchberg Massif, southern Germany. Earth Planet Sci Lett 99:230–249CrossRefGoogle Scholar
  60. Tappert R, Stachel T, Harris JW, Muehlenbachs K, Ludwig T, Brey GP (2005) Subducting oceanic crust; the source of deep diamonds. Geology 33:565–568CrossRefGoogle Scholar
  61. Taylor LA, Anand M (2004) Diamonds: time capsules from the Siberian Mantle. Chem Erde 64(1):1–74CrossRefGoogle Scholar
  62. Taylor LA, Neal CR (1989) Eclogites with oceanic crustal and mantle signatures from the Bellsbank kimberlite, South Africa, Part I: mineralogy, petrography, and whole-rock chemistry. Jour Geol 97:551–567CrossRefGoogle Scholar
  63. Taylor LA, Milledge HJ, Bulanova GP, Snyder GA, Keller RA (1998) Metasomatic eclogitic diamond growth: evidence from multiple diamond inclusions. Int Geol Rev 40:665–676CrossRefGoogle Scholar
  64. Ulmer P, Luth RW (1991) The graphite-COH fluid equilibrium in P, T, fO2 space. Contrib Mineral Petrol 106:265–272CrossRefGoogle Scholar
  65. Wade J, Wood BJ (2012) Metal-silicate partitioning experiments in the diamond anvil cell: a comment on potential analytical errors. Phys Earth Planet Int 192–193:54–58CrossRefGoogle Scholar
  66. Wade J, Buse B, Kearns S (2014) FEG-EPMA of solid state redox sensors—the effect of secondary fluorescence on analytical precision. Microsc Microanal 20(Supplement S3):728–729CrossRefGoogle Scholar
  67. Walter M, Bulanova G, Armstrong L, Keshav S, Blundy JD, Gudfinnsson G, Lord O, Lennie A, Smith C, Gobbo L (2008) Primary carbonatite melt from deeply subducted oceanic crust. Nature 454:622–625. doi: 10.1038/nature07132 CrossRefGoogle Scholar
  68. Woodland AB, O’Neill HStC (1997) Thermodynamic data for Fe-bearing phases obtained using noble metal alloys as redox sensors. Geochim Cosmochim Acta 61:4359–4366CrossRefGoogle Scholar
  69. Woodland AB, O’Neill HStC (1993) Synthesis and stability of Fe3Fe2 3+Si3O12 garnet and phase relations with Fe3Al2Si3O12–Fe3Fe2 3+Si3O12 solutions. Am Mineral 78:1000–1013Google Scholar
  70. Woodland AB, Seitz HM, Altherr R, Marschall H, Olker B, Ludwig T (2002) Li abundances in eclogite minerals: a clue to a crustal or mantle origin? Contrib Mineral Petrol 143:587–601CrossRefGoogle Scholar
  71. Yaxley GM, Brey GP (2004) Phase relations of carbonate-bearing eclogite assemblages from 2.5 to 5.5 GPa: implications for petrogenesis of carbonatites. Contrib Mineral Petrol 146:606–619CrossRefGoogle Scholar
  72. Yaxley GM, Green DH (1994) Experimental demonstration of refractory carbonate-bearing eclogite and siliceous melt in the subduction regime. Earth Planet Sci Lett 128:313–325CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Geophysical LaboratoryCarnegie Institution of WashingtonWashingtonUSA
  2. 2.Bayerisches GeoinstitutBayreuthGermany

Personalised recommendations