Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Carbon concentration increases with depth of melting in Earth’s upper mantle


Carbon in the upper mantle controls incipient melting of carbonated peridotite and so acts as a critical driver of plate tectonics. The carbon-rich melts that form control the rate of volatile outflux from the Earth’s interior, contributing to climate evolution over geological times. However, attempts to constrain the carbon concentrations of the mantle source beneath oceanic islands and continental rifts is complicated by pre-eruptive volatile loss from magmas. Here, we compile literature data on magmatic gases, as a surface expression of the pre-eruptive volatile loss, from 12 oceanic island and continental rift volcanoes. We find that the levels of carbon enrichment in magmatic gases correlate with the trace element signatures of the corresponding volcanic rocks, implying a mantle source control. We use this global association to estimate that the mean carbon concentration in the upper mantle, down to 200 km depth, is approximately 350 ppm (range 117–669 ppm). We interpret carbon mantle heterogeneities to reflect variable extents of mantle metasomatism from carbonated silicate melts. Finally, we find that the extent of carbon enrichment in the upper mantle positively correlates with the depth at which melting starts. Our results imply a major role of carbon in driving melt formation in the upper mantle.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: CO2 content in mafic melts from plume-related and continental rift volcanoes.
Fig. 2: Time-averaged volcanic gas CO2/ST ratios versus mean WR Sr/Sm and Sr/Nd ratios.
Fig. 3: C content in source mantles of plume-related (OIB and Iceland) and continental rift volcanoes.
Fig. 4: Composition of natural carbonatites and kimberlites.
Fig. 5: Modelling the gas–rock association.
Fig. 6: Schematic representation of vertical distribution of carbon in upper mantle.

Data availability

All data generated or analysed during this study are included in this published article (Extended Data Tables 14). The dataset is also publicly available in the EarthChem data repository106 ( Source data are provided with this paper.

Code availability

The code that supports the findings of this study and that was used to generate Figs. 1 and 5 and Extended Data Fig. 6 is available from G.T. ( upon request.


  1. 1.

    Hauri, E. H. et al. in Deep Carbon, Past to Present (eds Orcutt, B. N. et al.) 237–275 (Cambridge Univ. Press, 2020).

  2. 2.

    Le Voyer, M., Kelley, K. A., Cottrell, E. & Hauri, E. H. Heterogeneity in mantle carbon content from CO2-undersaturated basalts. Nat. Commun. 8, 14062 (2017).

    Article  Google Scholar 

  3. 3.

    Saal, A. E., Hauri, E. H., Langmuir, C. H. & Perfit, M. R. Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth’s upper mantle. Nature 419, 451–455 (2002).

    Article  Google Scholar 

  4. 4.

    Dasgupta, R. et al. Carbon-dioxide-rich silicate melt in the Earth’s upper mantle. Nature 493, 211–215 (2013).

    Article  Google Scholar 

  5. 5.

    Dasgupta, R. Volatile-bearing partial melts beneath oceans and continents – where, how much, and of what compositions? Am. J. Sci. 318, 141–165 (2018).

    Article  Google Scholar 

  6. 6.

    Yaxley, G. M. et al. in Deep Carbon, Past to Present (eds Orcutt, B. N. et al.) 129–162 (Cambridge Univ. Press, 2020).

  7. 7.

    Shirey, S. B. et al. in Deep Carbon, Past to Present (eds Orcutt, B. N. et al.) 89–128 (Cambridge Univ. Press, 2020).

  8. 8.

    Pearson, D. G., Canil, D., & Shirey, S. B. in Treatise on Geochemistry, The Mantle and Core 2nd edn (ed. Carlson, R. W.) 169–253 (Elsevier, 2014).

  9. 9.

    Wallace, P. J. et al. The Encyclopedia of Volcanoes (eds Sigurdsson, H. et al.) (Academic Press, Elsevier, 2015).

  10. 10.

    Javoy, M., Pineau, F. & Allegre, C. J. Carbon geodynamic cycle. Nature 300, 171–173 (1982).

    Article  Google Scholar 

  11. 11.

    Dasgupta, R. & Hirschmann, M. M. The deep carbon cycle and melting in Earth’s interior. Earth Planet. Sci. Lett. 298, 1–13 (2010).

    Article  Google Scholar 

  12. 12.

    Marty, B. et al. An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: geochemical and cosmochemical implications. Earth Planet. Sci. Lett. 551, 116574 (2020).

    Article  Google Scholar 

  13. 13.

    Hirschmann, M. M. Comparative deep Earth volatile cycles: the case for C recycling from exosphere/mantle fractionation of major (H2O, C, N) volatiles and from H2O/Ce, CO2/Ba, and CO2/Nb exosphere ratios. Earth Planet. Sci. Lett. 502, 262–273 (2018).

    Article  Google Scholar 

  14. 14.

    Stagno, V. et al. in Deep Carbon: Past to Present (eds Orcutt, B. et al.) 66–88 (Cambridge Univ. Press, 2019).

  15. 15.

    Moore, L. R. et al. Bubbles matter: an assessment of the contribution of vapor bubbles to melt inclusion volatile budgets. Am. Mineral. 100, 806–823 (2015).

    Article  Google Scholar 

  16. 16.

    Tucker, J. M. et al. A high carbon content of the Hawaiian mantle from olivine-hosted melt inclusions. Geochim. Cosmochim. Acta 254, 156–172 (2019).

    Article  Google Scholar 

  17. 17.

    Rosenthal, A., Hauri, E. H. & Hirschmann, M. Experimental determination of C, F, and H partitioning between mantle minerals and carbonated basalt, CO2/Ba and CO2/Nb systematics of partial melting, and the CO2 contents of basaltic source regions. Earth Planet. Sci. Lett. 425, 77–87 (2015).

    Article  Google Scholar 

  18. 18.

    Le Voyer, M. et al. Carbon fluxes and primary magma CO2 contents along the global mid-ocean ridge system. Geochem. Geophys. Geosyst. 20, 1387–1424 (2019).

    Article  Google Scholar 

  19. 19.

    Michael, P. J. & Graham, P. J. The behavior and concentration of CO2 in the suboceanic mantle: inferences from undegassed ocean ridge and ocean island basalts. Lithos 236–237, 338–351 (2015).

    Article  Google Scholar 

  20. 20.

    Cottrell, E., Kelley, K. A., Hauri, E. H., & Le Voyer, M. Mantle Carbon Contents for Mid-Ocean Ridge Segments, Version 1.0 (IEDA, 2019);

  21. 21.

    Hauri, E. H. et al. CO2 content beneath northern Iceland and the variability of mantle carbon. Geology 46, 55–58 (2017).

    Article  Google Scholar 

  22. 22.

    Anderson, K. R. & Poland, M. P. Abundant carbon in the mantle beneath Hawai’i. Nat. Geosci. 10, 704–708 (2017).

    Article  Google Scholar 

  23. 23.

    Boudoire, G., Rizzo, A. L., Di Muro, A., Grassa, F. & Liuzzo, M. Extensive CO2 degassing in the upper mantle beneath oceanic basaltic volcanoes: first insights from Piton de la Fournaise volcano (La Réunion Island). Geochim. Cosmochim. Acta 235, 376–401 (2018).

    Article  Google Scholar 

  24. 24.

    Bureau, H., Pineau, F., Metrich, N., Semet, M. P. & Javoy, M. A melt and fluid inclusion study of the gas phase at Piton de la Fournaise volcano (Réunion Island). Chem. Geol. 147, 115–130 (1998).

    Article  Google Scholar 

  25. 25.

    Métrich, N. et al. Is the “Azores Hotspot” a wetspot? Insights from the geochemistry of fluid and melt inclusions in olivine of Pico basalts. J. Petrol. 55, 377–393 (2014).

    Article  Google Scholar 

  26. 26.

    Longpré, M.-A., Stix, J., Klügel, A. & Shimizu, N. Mantle to surface degassing of carbon- and sulphur-rich alkaline magma at El Hierro, Canary Islands. Earth Planet. Sci. Lett. 460, 268–280 (2017).

    Article  Google Scholar 

  27. 27.

    Foley, S. F. & Fischer, T. P. An essential role for continental rifts and lithosphere in the deep carbon cycle. Nat. Geosci. 10, 897–902 (2017).

    Article  Google Scholar 

  28. 28.

    de Moor, J. M. et al. Volatile-rich silicate melts from Oldoinyo Lengai volcano (Tanzania): implications for carbonatite genesis and eruptive behaviour. Earth Planet. Sci. Lett. 361, 379–390 (2013).

    Article  Google Scholar 

  29. 29.

    Hudgins, T. R. et al. Melt inclusion evidence for CO2-rich melts beneath the western branch of the East African Rift: implications for long-term storage of volatiles in the deep lithospheric mantle. Contrib. Mineral. Petrol. 169, 46 (2015).

    Article  Google Scholar 

  30. 30.

    Lee, H. et al. Massive and prolonged deep carbon emissions associated with continental rifting. Nat. Geosci. (2016).

    Article  Google Scholar 

  31. 31.

    Werner, C. et al. in Deep Carbon, Past to Present (eds Orcutt, B. N. et al.) 188–236 (Cambridge Univ. Press, 2020).

  32. 32.

    Muirhead, J. D. et al. Displaced cratonic mantle concentrates deep carbon during continental rifting. Nature 582, 67–72 (2020).

    Article  Google Scholar 

  33. 33.

    Brune, S., Williams, S. E. & Muller, R. D. Potential links between continental rifting, CO2 degassing and climate change through time. Nat. Geosci. 10, 941–946 (2017).

    Article  Google Scholar 

  34. 34.

    Tappe, S., Smart, K. A., Torsvik, T. H., Massuyeau, M. & de Wit, M. C. J. Geodynamics of kimberlites on a cooling Earth: clues to plate tectonic evolution and deep volatile cycles. Earth Planet. Sci. Lett. 484, 1–14 (2018).

    Article  Google Scholar 

  35. 35.

    Aiuppa, A. et al. Forecasting Etna eruptions by real-time observation of volcanic gas composition. Geology 35, 1115–1118 (2007).

    Article  Google Scholar 

  36. 36.

    Edmonds, M. New geochemical insights into volcanic degassing. Philos. Trans. R. Soc. A 366, 4559–4579 (2008).

    Article  Google Scholar 

  37. 37.

    Aiuppa, A., Fischer, T. P., Plank, T., Robidoux, P. & Di Napoli, R. Along-arc, interarc and arc-to-arc variations in volcanic gas CO2/ST ratios reveal dual source of carbon in arc volcanism. Earth Sci. Rev. 168, 24–47 (2017).

    Article  Google Scholar 

  38. 38.

    Aiuppa, A., Fischer, T. P., Plank, T. & Bani, P. CO2 flux emissions from the Earth’s most actively degassing volcanoes, 2005–2015. Sci. Rep. 9, 5442 (2019).

    Article  Google Scholar 

  39. 39.

    Plank, T. & Manning, C. E. Subducting carbon. Nature 574, 343–352 (2019).

    Article  Google Scholar 

  40. 40.

    Gerlach, T. M. Interpretation of volcanic gas data from tholeiitic and alkaline mafic lavas. Bull. Volcanol. 45, 235–244 (1982).

    Article  Google Scholar 

  41. 41.

    Zindler, A. & Hart, S. Chemical geodynamics. Annu. Rev. Earth Planet. Sci. 14, 493–571 (1986).

    Article  Google Scholar 

  42. 42.

    Miller, W. G. R. et al. The carbon content of the deep mantle with Icelandic melt inclusions. Earth Planet. Sci. Lett. 523, 115699 (2019).

    Article  Google Scholar 

  43. 43.

    Bekaert, D. V. et al. Subduction-driven volatile recycling: a global mass balance. Annu. Rev. Earth Planet. Sci. 49, 37–70 (2021).

    Article  Google Scholar 

  44. 44.

    Gibson, A. A. & Richards, M. A. Delivery of deep-sourced, volatile-rich plume material to the global ridge system. Earth Planet. Sci. Lett. 499, 205–218 (2018).

    Article  Google Scholar 

  45. 45.

    Rohrbach, A. & Schmidt, M. W. Redox freezing and melting in the Earth’s deep mantle resulting from carbon–iron redox coupling. Nature 472, 209–212 (2011).

    Article  Google Scholar 

  46. 46.

    O’Reilly, S. Y. & Griffin, W. in Metasomatism and the Chemical Transformation of Rock (eds Harlov, D. E. & Austrheim, H.) 471–533 (Springer, 2013).

  47. 47.

    Walter, M. J. et al. Primary carbonatite melt from deeply subducted oceanic crust. Nature 454, 622–625 (2008).

    Article  Google Scholar 

  48. 48.

    Smith, E. M., Kopylova, M. G., Nowell, G. M., Pearson, D. G. & Ryder, J. Archean mantle fluids preserved in fibrous diamonds from Wawa, Superior Craton. Geology 40, 1071–1074 (2012).

    Article  Google Scholar 

  49. 49.

    Stagno, V., Ojwang, D. O., McCammon, C. A. & Frost, D. J. The oxidation state of the mantle and the extraction of carbon from Earth’s interior. Nature 493, 84–88 (2013).

    Article  Google Scholar 

  50. 50.

    Cartigny, P., Pineau, F., Aubaud, C. & Javoy, M. Towards a consistent mantle carbon flux estimate: insights from volatile systematics (H2O/Ce, δD, CO2/Nb) in the North Atlantic mantle (14°N and 34°N). Earth Planet. Sci. Lett. 265, 672–685 (2008).

    Article  Google Scholar 

  51. 51.

    Commission for the Geological Map of the World (CGMW) Geological Map of the World, Scale 1:25,000,000 (UNESCO, 2000).

  52. 52.

    Laske, G., Masters., G., Ma, Z. & Pasyanos, M. Update on CRUST1.0 - A 1-degree Global Model of Earth’s Crust. Geophys. Res. Abstracts 15, abstr. EGU2013-2658 (2013).

    Google Scholar 

  53. 53.

    Ekström, G., Nettles, M. & Dziewonski, A. M. The global CMT project 2004−2010: centroid-moment tensors for 13,017 earthquakes. Phys. Earth Planet. Inter. 200, 1–9 (2012).

    Article  Google Scholar 

  54. 54.

    Symonds, R. B., Rose, W. I., Bluth, G. J. S. & Gerlach, T. M. Volcanic-gas studies: methods, results and applications. Rev. Mineral. 30, 1–66 (1994).

    Google Scholar 

  55. 55.

    Oppenheimer, C., Fischer, T. P. & Scaillet B. in Treatise on Geochemistry, The Crust 2nd edn (eds Holland, H. D. & Turekian, K. K.) 111–179 (Elsevier, 2014).

  56. 56.

    Fischer, T. P. & Chiodini, G. in Encyclopaedia of Volcanoes 2nd edn, 779–797 (2015);

  57. 57.

    Hartley, M. E., Maclennan, J., Edmonds, M. & Thordarson, T. Reconstructing the deep CO2 degassing behaviour of large basaltic fissure eruptions. Earth Planet. Sci. Lett. 393, 120–131 (2014).

    Article  Google Scholar 

  58. 58.

    Fischer, T. P. Fluxes of volatiles (H2O, CO2, N2, Cl, F) from arc volcanoes. Geochem. J. 42, 21–38 (2008).

    Article  Google Scholar 

  59. 59.

    Wallace, P. J. Volatiles in subduction zone magmas: concentrations and fluxes based on melt inclusions and volcanic gas data. J. Volcanol. Geotherm. Res. 140, 217–240 (2005).

    Article  Google Scholar 

  60. 60.

    Symonds, R. B., Gerlach, T. M. & Reed, M. H. Magmatic gas scrubbing: implications for volcano monitoring. J. Volcanol. Geotherm. Res. 108, 303–341 (2001).

    Article  Google Scholar 

  61. 61.

    Di Napoli, R. et al. Reaction path models of magmatic gas scrubbing. Chem. Geol. 420, 251–269 (2016).

    Article  Google Scholar 

  62. 62.

    Smith, W. H. F. & Sandwell, D. T. Global seafloor topography from satellite altimetry and ship depth soundings. Science 277, 1957–1962 (1997).

    Google Scholar 

  63. 63.

    Aiuppa, A., Giudice, G. & Liuzzo, M. Volcanic Gas Plume Data Etna Volcano (Italy), Version 1.0 (IEDA, 2017);

  64. 64.

    Ilanko, T. Geochemistry of Gas Emissions from Erebus Volcano, Antarctica. PhD dissertation, Cambridge Univ. (2014).

  65. 65.

    Bobrowski, N. et al. Plume composition and volatile flux of Nyamulagira volcano, Democratic Republic of Congo, during birth and evolution of the lava lake, 2014–2015. Bull. Volcanol. 79, 90 (2017).

    Article  Google Scholar 

  66. 66.

    Koepenick, K. W. et al. Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania. J. Geophys. Res. 101, 13819–13830 (1996).

    Article  Google Scholar 

  67. 67.

    Oppenheimer, C., Burton, M. R., Durieux, J. & Pyle, D. M. Open-path Fourier transform spectroscopy of gas emissions from Oldoinyo Lengai volcano, Tanzania. Opt. Lasers Eng. 37, 203–214 (2002).

    Article  Google Scholar 

  68. 68.

    Javoy, M., Pineau, F., Cheminee, J. L. & Krafft, M. The gas magma relationship in the 1988 eruption of Oldoinyo Lengai (Tanzania). Eos Trans. AGU 69, 1466 (1988).

    Google Scholar 

  69. 69.

    Hernández, P. A. et al. Chemical composition of volcanic gases emitted during the 2014-15 Fogo eruption, Cape Verde. Geophys. Res. Abstracts 17, abstr. EGU2015-9577 (2015).

    Google Scholar 

  70. 70.

    Di Muro, A. et al. in Active Volcanoes of the Southwest Indian Ocean (eds Bachelery, P. et al.) 203–222 (Springer, 2016);

  71. 71.

    Allard, P. et al. First measurements of magmatic gas composition and fluxes during an eruption (October 2010) of Piton de la Fournaise hot spot volcano, La Reunion Island. Geophys. Res. Abstracts 13, abstr. EGU2011-13182 (2011).

    Google Scholar 

  72. 72.

    Sutton, A. J. & Elias, T. in Characteristics of Hawaiian Volcanoes. US Geological Survey Professional Paper 1801 (eds Poland, M. P. et al.) 295–320 (USGS, 2014).

  73. 73.

    Gerlach, T. M. & Graeber, E. J. Volatile budget of Kilauea Volcano. Nature 313, 273–277 (1985).

    Article  Google Scholar 

  74. 74.

    Edmonds, M. & Gerlach, T. M. Vapor segregation and loss in basaltic melts. Geology 35, 751–754 (2007).

    Article  Google Scholar 

  75. 75.

    Elias, T., Kern, C., Horton, K. A., Sutton, A. J. & Garbeil, H. Measuring SO2 emission rates at Kılauea Volcano, Hawaii, using an array of upward-looking UV spectrometers. Front. Earth Sci. 6, 214 (2018).

    Article  Google Scholar 

  76. 76.

    Poland, M. P., Miklius, A., J. Sutton, A. & Thornber, C. R. A mantle-driven surge in magma supply to Kilauea Volcano during 2003-2007. Nat. Geosci. 5, 295–300 (2012).

    Article  Google Scholar 

  77. 77.

    Edmonds, M. et al. Magma storage, transport and degassing during the 2008–10 summit eruption at Kılauea Volcano, Hawai’i. Geochim. Cosmochim. Acta 123, 284–301 (2013).

    Article  Google Scholar 

  78. 78.

    Gerlach, T. M. Evaluation of volcanic gas analyses from Kilauea volcano. J. Volcanol. Geotherm. Res. 7, 295–317 (1980).

    Article  Google Scholar 

  79. 79.

    Naughton, J. J., Derby, J. V. & Glover, R. B. Infrared measurements on volcanic gas and fume: Kilauea eruption, 1968. J. Geophys. Res. 74, 3273–3277 (1969).

    Article  Google Scholar 

  80. 80.

    Allard, P., Tazieff, H. & Dajlevic, D. Observations of seafloor spreading in Afar during the November 1978 fissure eruption. Nature 279, 30–33 (1979).

    Article  Google Scholar 

  81. 81.

    Gerlach, T. M. Restoration of new volcanic gas analyses from basalts of the Afar region: further evidence of CO2 degassing trends. J. Volcanol. Geotherm. Res. 10, 83–91 (1981).

    Article  Google Scholar 

  82. 82.

    Gerlach, T. M. Investigation of volcanic gas analyses and magma outgassing from Erta ‘Ale lava lake, Afar, Ethiopia. J. Volcanol. Geotherm. Res. 7, 415–441 (1980).

    Article  Google Scholar 

  83. 83.

    Donovan, A., Blundy, J., Oppenheimer, C. & Buisman, I. The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions. Contrib. Mineral. Petrol. (2018).

  84. 84.

    Sun, S. S. & McDonough, W. F. in Magmatism in the Ocean Basins (eds Saunders, A. D. & Norry, M. J.) 313–345 (Geological Society, 1989).

  85. 85.

    Workman, R. K. & Hart, S. R. Major and trace element composition of the depleted MORB mantle (DMM). Earth Planet. Sci. Lett. 231, 53–57 (2005).

    Article  Google Scholar 

  86. 86.

    Shaw, D. M. Trace element melting models. Phys. Chem. Earth. 11, 577–586 (1979).

    Article  Google Scholar 

  87. 87.

    Casetta, F., Giacomoni, P. P., Ferlito, C., Bonadiman, C. & Coltorti, M. The evolution of the mantle source beneath Mt. Etna (Sicily, Italy): from the 600 ka tholeiites to the recent trachybasaltic magmas. Int. Geol. Rev. 62, 338–359 (2020).

    Article  Google Scholar 

  88. 88.

    Putirka, K. D. Thermometers and barometers for volcanic systems. Rev. Mineral. Geochem. 69, 61–120 (2008).

    Article  Google Scholar 

  89. 89.

    Beattie, P. Olivine-melt and orthopyroxene-melt equilibria. Contrib. Mineral. Petrol. 115, 103–111 (1993).

    Article  Google Scholar 

  90. 90.

    Gualda, G. A. R., Ghiorso, M. S., Lemons, R. V. & Carley, T. L. Rhyolite-MELTS: a modified calibration of MELTS optimized for silica-rich, fluid-bearing magmatic systems. J. Petrol. 53, 875–890 (2012).

    Article  Google Scholar 

  91. 91.

    Putirka, K. D. Mantle potential temperatures at Hawaii, Iceland, and the mid-ocean ridge system, as inferred from olivine phenocrysts: evidence for thermally driven mantle plumes. Geochem. Geophys. Geosyst. 6, 1–14 (2005).

    Article  Google Scholar 

  92. 92.

    Dalton, C. A., Langmuir, C. H. & Gale, A. Geophysical and geochemical evidence for deep temperature variations beneath midocean ridges. Science 344, 80–83 (2014).

    Article  Google Scholar 

  93. 93.

    Gale, A., Langmuir, C. H. & Dalton, C. A. The global systematics of ocean ridge basalts and their origin. J. Petrol. 55, 1051–1082 (2014).

    Article  Google Scholar 

  94. 94.

    Demant, A., Lestrade, P., Lubala, R. T., Kampunzu, A. B. & Durieux, J. Volcanological and petrological evolution of Nyiaragongo Volcano, Virunga volcanic field, Zaire. Bull. Volcanol. 56, 47–61 (1994).

    Article  Google Scholar 

  95. 95.

    Platz, T., Foley, S. F. & Andre, L. Low-pressure fractionation of the Nyiragongo volcanic rocks, Virunga Province, D. R. Congo. J. Volcanol. Geotherm. Res. 136, 269–295 (2004).

    Article  Google Scholar 

  96. 96.

    Chakrabarti, R., Basu, A. R., Santo, A. P., Tedesco, D. & Vaselli, O. Isotopic and geochemical evidence for a heterogeneous mantle plume origin of the Virunga volcanics, Western rift, East African Rift system. Chem. Geol. 259, 273–289 (2009).

    Article  Google Scholar 

  97. 97.

    Foley, S. F. et al. The composition of near-solidus melts of peridotite in the presence of CO2 and H2O at 40–60 kbar. Lithos 112S, 274–283 (2009).

    Article  Google Scholar 

  98. 98.

    Janousek, V., Moyen, J.-F., Martin, H. & Erban, V., Farrow, C. Geochemical Modelling of Igneous Processes – Principles and Recipes in R Language (Springer, 2015).

  99. 99.

    Langmuir, C. H., Vocke, R. D. & Hanson, G. N. A general mixing equation with application to Icelandic basalts. Earth Planet. Sci. Lett. 37, 380–392 (1978).

    Article  Google Scholar 

  100. 100.

    Thomson, A. R., Walter, M. J., Kohn, S. C. & Brooker, R. A. Slab melting as a barrier to deep carbon subduction. Nature 529, 76–79 (2016).

    Article  Google Scholar 

  101. 101.

    Sun, C. & Dasgupta, R. Slab–mantle interaction, carbon transport, and kimberlite generation in the deep upper mantle. Earth Planet. Sci. Lett. 506, 38–52 (2019).

    Article  Google Scholar 

  102. 102.

    Mitchell, R. H., Giuliani, A. & O’Brien, H. What is a kimberlite? Petrology and mineralogy of hypabyssal kimberlites. Elements 15, 381–386 (2019).

    Article  Google Scholar 

  103. 103.

    Pearson, D. G., Woodhead, J. & Janney, P. E. Kimberlites as geochemical probes of Earth’s mantle. Elements 15, 387–39 (2019).

    Article  Google Scholar 

  104. 104.

    Casetta, F. et al. The alkaline lamprophyres of the Dolomitic Area (Southern Alps, Italy): markers of the Late Triassic change from orogenic-like to anorogenic magmatism. J. Petrol. 60, 1263–1298 (2019).

    Article  Google Scholar 

  105. 105.

    Chowdhury, P. & Dasgupta, R. Sulfur extraction via carbonated melts from sulfide-bearing mantle lithologies – implications for deep sulfur cycle and mantle redox. Geochim. Cosmochim. Acta 269, 376–397 (2020).

    Article  Google Scholar 

  106. 106.

    Aiuppa, A., Casetta, F., Coltorti, M., Stagno, V. & Tamburello, G. CO2 in Magmatic Gases, Parental Melts and Mantle Sources from 12 OIB and CR volcanoes, Version 1.0 (IEDA, 2021);

Download references


This work received funding from the Deep Carbon Observatory (subcontract no. 10759-1238; A.A.) and from the Italian Ministero Istruzione Università e Ricerca (Miur, Grant N. 2017LMNLAW; A.A.). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. The authors thank A. Rohrbach for useful comments on an earlier version of the manuscript.

Author information




A.A. devised the study concept. A.A., F.C., M.C., V.S. and G.T. contributed to refinement of the initial concept, and to data analysis and interpretation. A.A. drafted the original version of the manuscript with contributions from all coauthors.

Corresponding author

Correspondence to Alessandro Aiuppa.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Geoscience thanks Arno Rohrbach and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Rebecca Neely, in collaboration with the Nature Geoscience team.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Global map illustrating the location of the 12 hot-spot and continental rift volcanoes.

The base map is a relief and bathymetry Raster called “Natural Earth II with Shaded Relief and Water” file #NE2_HR_LC_SR_W.tiff (Made with Natural Earth. Free vector and raster map data @ The shaded relief is the CleanTOPO2 layer, a modified SRTM30 Plus World Elevation Data also edited by Tom Patterson, US National Park Service (original data source, ref. 62).

Extended Data Fig. 2 Whole-rock compositions.

(a) Total Alkali Silica (TAS) diagram for the 12 volcanoes. The most primitive magmas erupted from Kilauea, Piton de la Fournaise, Erta Ale, Ardoukoba, Surtsey and Holuhraun (Bardabunga) are subalkaline, with Na2O + K2O contents not exceeding 3.5 wt%, at SiO2 comprised between 43 and 50 wt%. They all plot in the basaltic field, except for the one belonging to Piton de la Fournaise, which is a picrite. The most primitive magmas erupted from Etna and Nyamuragira are mildly alkaline (alkali basalts; Na2O + K2O around 4.0 wt%; SiO2 = 45-46 wt%), whereas those belonging to Erebus, Pico do Fogo, Nyiragongo and Ol Doinyo Lengai are alkaline to highly alkaline, with alkali and silica contents up to 7.4 wt% and down to 35 wt%, respectively. They range in composition from tephrites/basanites (Erebus and Pico do Fogo) to melilitites/nephelinites (Nyiragongo and Ol Doinyo Lengai). (b) Chondrite-normalised spider diagram84. The chondrite-normalized incompatible element patterns demonstrate the discrimination between subalkaline and alkaline rocks. The Bardarbunga basalt has the most depleted pattern, with a flat REE profile [(La/Yb)N = 1.7]. Primitive basalts/picrites from Kilauea, Surtsey, Piton de la Fournaise, and Ardoukoba are progressively enriched in LILE and Nb-Ta and are all characterized by Ti negative anomalies, except for Surtsey. They are characterized by variable HREE abundances at comparable LREE contents, resulting in moderately to significantly steep REE profiles. (La/Yb)N vary from 3.6 (Ardoukoba) to 5.0-6.3 (Kilauea and Piton de la Fournaise), testifying for the increasingly important role played by garnet in their mantle sources. With respect to the other subalkaline rocks, Erta Ale basalt is enriched in Th-U, Nb-Ta, and is typified by steeper REE profiles [(La/Yb)N = 6.5]. Etna and Nyamuragira alkali basalts are enriched in Rb, Ba, Th, U and have analogous REE profiles [(La/Yb)N = 15.3-22.1], at HREE abundances comparable to those of Piton de la Fournaise picrite. With respect to Nyamuragira, however, Etna has lower Nb-Ta and Ti concentrations. Erebus basanite and Pico do Fogo tephrites have Rb-Ba enrichments, Nb-Ta positive anomalies and steep REE profiles, at HREE concentrations comparable to Etna, Nyamuragira and Piton de la Fournaise basalts/alkali basalts [(La/Yb)N = 10.1-19.1]. The Nyiragongo and Ol Doinyo Lengai melilitites/nephelinites exhibit the most significant enrichments in incompatible elements, accompanied by Ti negative anomalies and very steep REE patterns, with (La/Yb)N up to 41.9-50.9 at YbN values comprised between 17 and 23.

Extended Data Fig. 3 Gas CO2/ST ratios vs. whole-rock trace element ratios.

Examples of scatter plots contrasting, for the 12 volcanoes, the time-averaged gas CO2/ST ratios with trace-element compositions of the corresponding whole-rocks (trace-element ratios use element Sr as the common reference). The best-fit regression lines (with equations and regression coefficients) are shown in red. The averaged composition of the Depleted MORB Mantle (DMM) is calculated by combining data in ref. 1,20 (C), ref. 3 (S) and ref. 18,85 (trace elements).

Extended Data Fig. 4 Comparison between Melt Inclusion (MIs) and whole-rock compositions for Kilauea volcano.

Sr/Nd and Sr/Sm ratios (upper panels) are overlapping for the two datasets, and show no dependence on magma differentiation degree (SiO2, in wt. %). The dashed vertical line indicate 52 wt. % SiO2, the threshold below which data are considered for calculating the “mean” compositions. The bottom panels compare the mean Ba (left) and Nb (right) contents (from averaging of all < 52 wt. SiO2 data; red triangle) with the inferred parental melt contents (from averaging the most primitive products only; yellow triangle). Both data types are listed in Extended Data Table 2.

Extended Data Fig. 5 The composition of natural carbonatites and kimberlites, with the composition of experimental melts formed by incipient melting of mantle peridotites/eclogites.

These are used to constrain the C, S and Sr composition of the mCm(s) (Cb1-2 and, Kb1-3). (a) CO2 vs. Sr global distribution of natural carbonatitic and kimberlitic rocks (source GeoRoc; These define a compositional array overlapping (but extending to more enriched compositions) the compositional array exhibited by our parental CO2 (inferred, Fig. 1 and Extended Table 3) vs. Sr trend for the 12 hot-spot/rift volcanoes (symbols are as in Fig. 1); (b) The derived Sr/Sm ratios are similar in the 5 mCm model scenarios; (c) Global datasets (GeoRoc) demonstrate that Ca and Sr are globally correlated in natural carbonatitic and kimberlitic rocks, suggesting that calcic (dolomitic) incipient mantle melts are very likely to be Sr-rich, too; (d and e) Global correlations of CO2 vs. SiO2 and CO2 vs. S in natural carbonatitic and kimberlitic rocks, compared with the composition of experimentally derived mantle melts4,105. From data in plot (e), we infer a characteristic (GeoRoc mean) S content of 1000-2000 ppm in carbonatitic to carbonated silicate melts in the mantle105.

Extended Data Fig. 6 The procedure used to model our gas (CO2/ST) - trace element volcano relationships.

The original dataset (red symbols) is back-processed using the Batch melting equations to calculate the corresponding ratios in the source mantle, using F values of 0.2, 0.1, 0.05 and 0.025. Each of the 4 newly obtained datasets (1 for each F value) is best-fitted with a mixing equations (eq. 5), in which the mixing end-members are the DMM (with (CO2/ST)DMM and (Sr/Sm)DMM from ref. 1,3,18,20,85) and a C-rich metasomatizing melt (mCm). The C, S and Sr concentration of the mCm are fixed based on results for natural and experimental carbonatitic/kimberlitic melts (Extended Data Table 4), and the Sm concentration is derived from data regression. The same operation, repeated for couples of trace-element ratios, allows the entire trace-element suite of the mCm to be derived for the 5 distinct model scenarios.

Extended Data Table 1 Time-averaged (mean ± 1 standard deviation, SD) CO2/ST ratios in volcanic gases
Extended Data Table 2 Major and trace element composition for volcanic rocks of the 12 volcano sites
Extended Data Table 3 Derived parental melt CO2 and source mantle carbon contents
Extended Data Table 4 Trace element composition of the metasomatic C-rich melts

Supplementary information

Supplementary information

Supplementary discussion and Fig. 1.

Source data

Source Data Fig. 1

Parental melt CO2, Ba and Nb for 14 volcanoes. Melt inclusions CO2, Ba and Nb data from literature. Calculated end-members for metasomatic C-rich melts.

Source Data Fig. 2

CO2/ST, Sr/Nd and Sr/Sm mass ratios of 12 volcanoes and DMM.

Source Data Fig. 3

Source mantle C concentration, melting pressure and melting depth of 12 volcanoes, DMM and from literature.

Source Data Fig. 4

Parental melt CO2 and Sr concentrations, Sr/Nd and Sr/Sm mass ratios of 12 volcanoes, calculated end-members for metasomatic C-rich melts and from literature.

Source Data Fig. 5

CO2/ST, Sr/Nd and Sr/Sm mass ratios of 12 volcanoes, DMM, MORBs and calculated end-members for metasomatic C-rich melts. Calculate PM-normalized trace elements of the end-members for metasomatic C-rich melts.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Aiuppa, A., Casetta, F., Coltorti, M. et al. Carbon concentration increases with depth of melting in Earth’s upper mantle. Nat. Geosci. 14, 697–703 (2021).

Download citation


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing