Letter | Published:

Massive and prolonged deep carbon emissions associated with continental rifting

Nature Geoscience volume 9, pages 145149 (2016) | Download Citation

Abstract

Carbon from Earth’s interior is thought to be released to the atmosphere mostly via degassing of CO2 from active volcanoes1,2,3,4. CO2 can also escape along faults away from active volcanic centres, but such tectonic degassing is poorly constrained1. Here we use measurements of diffuse soil CO2, combined with carbon isotopic analyses to quantify the flux of CO2 through fault systems away from active volcanoes in the East African Rift system. We find that about 4 Mt yr−1 of mantle-derived CO2 is released in the Magadi–Natron Basin, at the border between Kenya and Tanzania. Seismicity at depths of 15–30 km implies that extensional faults in this region may penetrate the lower crust. We therefore suggest that CO2 is transferred from upper-mantle or lower-crustal magma bodies along these deep faults. Extrapolation of our measurements to the entire Eastern rift of the rift system implies a CO2 flux on the order of tens of megatonnes per year, comparable to emissions from the entire mid-ocean ridge system2,3 of 53–97 Mt yr−1. We conclude that widespread continental rifting and super-continent breakup could produce massive, long-term CO2 emissions and contribute to prolonged greenhouse conditions like those of the Cretaceous.

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References

  1. 1.

    , & Deep carbon emission from volcanoes. Rev. Mineral. Geochem. 75, 323–354 (2013).

  2. 2.

    & CO2 fluxes from mid-ocean ridges, arcs and plumes. Chem. Geol. 145, 233–248 (1998).

  3. 3.

    et al. Sulphur geodynamic cycle. Sci. Rep. 5, 8330 (2015).

  4. 4.

    et al. Global CO2 emission from volcanic lakes. Geology 39, 235–238 (2011).

  5. 5.

    & Hydrothermal CO2 emission from the Taupo Volcanic Zone, New Zealand. Earth Planet. Sci. Lett. 139, 105–113 (1996).

  6. 6.

    et al. Carbon dioxide Earth degassing and seismogenesis in central and southern Italy. Geophys. Res. Lett. 31, L07615 (2004).

  7. 7.

    & in Tectonics of Sedimentary Basins: Recent Advances (eds Busby, C. & Azor, A.) Ch. 9 (John Wiley, 2012).

  8. 8.

    , , , & Investigation into magma degassing at Nyiragongo volcano, Democratic Republic of the Congo. Geochem. Geophys. Geosyst. 9, Q02017 (2008).

  9. 9.

    & Measured carbon dioxide emissions from Oldoinyo Lengai and the skewed distribution of passive volcanic fluxes. Geology 23, 933–936 (1995).

  10. 10.

    et al. Methane sources and sinks in Lake Kivu. J. Geophys. Res. 116, G03006 (2011).

  11. 11.

    , , , & Structural controls on fluid pathways in an active rift system: a case study of the Aluto volcanic complex. Geosphere 11, 542–562 (2015).

  12. 12.

    , , , & Fluid-triggered earthquake swarms in the Rwenzori region, East African Rift—evidence for rift initiation. Tectonophysics 566, 95–104 (2012).

  13. 13.

    et al. Carbon isotopic composition of soil CO2 efflux, a powerful method to discriminate different sources feeding soil CO2 degassing in volcanic hydrothermal areas. Earth Planet. Sci. Lett. 274, 372–379 (2008).

  14. 14.

    & CO2 degassing along the San Andreas fault, Parkfield, California. Geophys. Res. Lett. 27, 5–8 (2000).

  15. 15.

    et al. Distinguishing contributions to diffuse CO2 emissions in volcanic areas from magmatic degassing and thermal decarbonation using soil gas 222Rn–δ13C systematics: application to Santorini volcano, Greece. Earth Planet. Sci. Lett. 377–378, 180–190 (2013).

  16. 16.

    & Origin of carbon in fumarolic gas from island arcs. Chem. Geol. 119, 265–274 (1995).

  17. 17.

    et al. Upper mantle volatile chemistry at Oldoinyo Lengai volcano and the origin of carbonatites. Nature 459, 77–80 (2009).

  18. 18.

    , , , & The origin of hydrothermal and other gases in the Kenya Rift Valley. Geochim. Cosmochim. Acta 59, 2501–2512 (1995).

  19. 19.

    & in The Encyclopedia of Volcanoes (eds Sigurdsson, H., Houghton, B., McNutt, S., Rymer, H. & Stix, J.) Ch. 45 (Academic, 2015).

  20. 20.

    et al. The influence of pre-existing structures on the evolution of the southern Kenya rift valley—evidence from seismic and gravity studies. Tectonophysics 278, 211–242 (1997).

  21. 21.

    , , & Tectonic development of the northern Tanzanian sector of the east African rift system. J. Geol. Soc. 154, 689–700 (1997).

  22. 22.

    , & The role of fluids in lower-crustal earthquakes near continental rifts. Nature 446, 1075–1079 (2007).

  23. 23.

    , & EAGLE Working Group, Three dimensional seismic imaging of a proto-ridge axis in the Main Ethiopian Rift. Geology 39, 949–952 (2004).

  24. 24.

    et al. Aseismic strain accommodation by slow slip and dyking in a youthful continental rift, East Africa. Nature 456, 783–787 (2008).

  25. 25.

    et al. Lower crustal earthquakes near the Ethiopian rift induced by magmatic processes. Geochem. Geophys. Geosyst. 10, Q0AB02 (2009).

  26. 26.

    , , , & Deep crustal earthquakes in North Tanzania, East Africa: interplay between tectonic and magmatic processes in an incipient rift. Geochem. Geophys. Geosyst. 15, 374–394 (2014).

  27. 27.

    et al. Continental arc–island arc fluctuations, growth of crustal carbonates, and long-term climate change. Geosphere 9, 1–36 (2013).

  28. 28.

    & Phanerozoic Large Igneous Provinces (LIPs), HEATT (Haline Euxinic Acidic Thermal Transgression) episodes, and mass extinctions. Palaeogeogr. Palaeoclimatol. Palaeoecol. 295, 162–191 (2010).

  29. 29.

    , , , & On causal links between flood basalts and continental breakup. Earth Planet. Sci. Lett. 166, 177–195 (1999).

  30. 30.

    , , & Volatile fluxes during flood basalt eruptions and potential effects on the global environment: a Deccan perspective. Earth Planet. Sci. Lett. 248, 518–532 (2006).

  31. 31.

    , , , & Soil CO2 flux measurements in volcanic and geothermal areas. Appl. Geochem. 13, 543–552 (1998).

  32. 32.

    & Comparison of carbon dioxide emissions with fluid upflow, chemistry, and geologic structures at the Rotorua geothermal system, New Zealand. Geothermics 35, 221–238 (2006).

  33. 33.

    & Methods for The Collection and Analysis of Geothermal and Volcanic Water and Gas Samples Tech. Rep. CD2401 (Department of Scientific and Industrial Research, Institute of Geological and Nuclear Sciences, New Zealand, 1989).

  34. 34.

    et al. Gas chemistry and nitrogen isotope compositions of cold mantle gases from Rungwe Volcanic Province, southern Tanzania. Chem. Geol. 339, 30–42 (2013).

  35. 35.

    SeismicHandler—programmable multichannel data handler for interactive and automatic processing of seismological analysis. Comp. Geosci. 19, 135–140 (1993).

  36. 36.

    et al. Contrasted seismogenic and rheological behaviours from shallow and deep earthquake sequences in the North Tanzanian Divergence, East Africa. J. Afr. Earth Sci. 58, 799–811 (2010).

  37. 37.

    Hypocenter Location Program HYPOINVERSE Tech. Rep. 78-698 (US Geological Survey, 1978).

  38. 38.

    et al. Images of the East Africa Rift System from the Joint Inversion of Bodywaves, Surfacewaves, and Gravity: Investigating the Role of Magma in Early-stage Continental Rifting Am. Geophys. Union Fall Meeting T51G-3013 107 (AGU, 2015).

  39. 39.

    & A double-difference earthquake location algorithm: method and application to the northern Hayward fault, California. Bull. Seismol. Soc. Am. 90, 1353–1368 (2000).

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Acknowledgements

This work was funded by the NSF EAR Tectonics Program, grant numbers 1113066 (T.P.F.), 1113355 (C.J.E.), and 1113677 (S.A.K.). Additional support was provided by Fulbright New Zealand (J.D.M.). CNRS and INSU-supported CoLIBREA project (C.J.E.). We thank the Tanzania COSTECH and the Kenyan National Council for Science and Technology for granting research permits. We acknowledge M. Songo and the Nelson Mandela African Institute of Science and Technology for support. Aerial photographs were provided by the Polar Geospatial Center, University of Minnesota. Aster GDEM is a product of METI and NASA. We gratefully acknowledge support from the Center for Stable Isotopes, UNM. We thank N. Thomas, S. Goldstein, K. Lehnert, B. Onguso, M. Maqway, K. Kimani and the Masai people for help during fieldwork, and A. Van Eaton for helpful comments. We also thank A. Weinstein for earthquake depth analyses, and N. Thomas for entering the geochemical data into the IEDA EarthChem Library.

Author information

Affiliations

  1. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA

    • Hyunwoo Lee
    • , Tobias P. Fischer
    •  & Zachary D. Sharp
  2. Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844-3022, USA

    • James D. Muirhead
    •  & Simon A. Kattenhorn
  3. Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627, USA

    • Cynthia J. Ebinger
  4. ConocoPhillips, Houston, Texas 77079, USA

    • Simon A. Kattenhorn
  5. Department of Geology, Chiromo Campus, University of Nairobi, PO Box 30197-00100, GPO Nairobi, Kenya

    • Gladys Kianji

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Contributions

H.L., J.D.M., T.P.F. and S.A.K. planned the field campaign to the Magadi–Natron basin; H.L., J.D.M., T.P.F., C.J.E. and G.K. carried out the field work; H.L., J.D.M., T.P.F. and G.K. conducted CO2 flux measurement and collected gas samples; H.L. carried out gas chemistry and carbon isotope analyses; J.D.M. and S.A.K. performed fault analyses to estimate total CO2 flux; C.J.E. analysed broadband seismic data; Z.D.S. supported carbon isotope analyses at the Center for Stable Isotopes, University of New Mexico; H.L., J.D.M., T.P.F., C.J.E. and S.A.K. collaboratively wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Hyunwoo Lee.

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DOI

https://doi.org/10.1038/ngeo2622

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