Letter | Published:

Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks

Nature Geoscience volume 7, pages 2528 (2014) | Download Citation

Abstract

Some graphite contained in the 3.7-billion-year-old metasedimentary rocks of the Isua Supracrustal Belt, Western Greenland1, is depleted in 13C and has been interpreted as evidence for early life2. However, it is unclear whether this graphite is primary, or was precipitated from metamorphic or igneous fluids3,4. Here we analyse the geochemistry and structure of the 13C- depleted graphite in the Isua schists. Raman spectroscopy and geochemical analyses indicate that the schists are formed from clastic marine sediments that contained 13C-depleted carbon at the time of their deposition. Transmission electron microscope observations show that graphite in the schist occurs as nanoscale polygonal and tube-like grains, in contrast to abiotic graphite in carbonate veins that exhibits a flaky morphology. Furthermore, the graphite grains in the schist contain distorted crystal structures and disordered stacking of sheets of graphene. The observed morphologies are consistent with pyrolysation and pressurization of structurally heterogeneous organic compounds during metamorphism. We thus conclude that the graphite contained in the Isua metasediments represents traces of early life that flourished in the oceans at least 3.7 billion years ago.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1.

    , & Detrital zircon sedimentary provenance ages for the Eoarchaean Isua supracrustal belt southern West Greenland: Juxtaposition of an imbricated ca. 3700 Ma juvenile arc against an older complex with 3920–3760 Ma components. Precambrian Res. 172, 212–233 (2009).

  2. 2.

    13C-depleted carbon microparticles in >3700-Ma sea-floor sedimentary rocks from west Greenland. Science 283, 674–676 (1999).

  3. 3.

    , , & Non-biogenic graphite in 3.8-Ga metamorphic rocks from the Isua district, Greenland. Chem. Geol. 133, 251–260 (1996).

  4. 4.

    , & Reassessing the evidence for the earliest traces of life. Nature 418, 627–630 (2002).

  5. 5.

    et al. Evidence for life on Earth before 3,800 million years ago. Nature 384, 55–59 (1996).

  6. 6.

    & Metasomatic origin of quartz–pyroxene rock, Akilia, Greenland, and implications for Earth’s earliest life. Science 296, 1448–1452 (2002).

  7. 7.

    , , & Carbon isotope geochemistry of the 3.7×109-yr-old Isua sediments, West Greenland: Implications for the Archaean carbon and oxygen cycles. Geochim. Cosmochim. Acta 43, 189–199 (1979).

  8. 8.

    , , , & Ion microprobe analysis of graphite from ca. 3.8 Ga metasediments, Isua supracrustal belt, West Greenland: Relationship between metamorphism and carbon isotopic composition. Geochim. Cosmochim. Acta 66, 1257–1268 (2002).

  9. 9.

    , & The origin of metacarbonate rocks in the Archaean Isua supracrustal belt, West Greenland. Am. J. Sci. 96, 1004–1044 (1996).

  10. 10.

    , , & Earliest part of Earth’s stratigraphic record: A reappraisal of the >3.7 Ga Isua (Greenland) supracrustal sequence. Geology 24, 43–46 (1996).

  11. 11.

    & The Continental Crust: Its Composition and Evolution (Blackwell, 1985).

  12. 12.

    & Constraints on graphite crystallinity in some Spanish fluid-deposited occurrences from different geologic settings. Miner. Deposita 34, 215–219 (1999).

  13. 13.

    & Thermal anomalies in a regional metamorphic terrane: An isotopic study of the role of fluids. J. Petrol. 29, 1215–1232 (1988).

  14. 14.

    Carbon isotopic variations in fluid-deposited graphite: Evidence for multicomponent Rayleigh isotopic fractionation. Int. Geol. Rev. 51, 45–57 (2009).

  15. 15.

    , , & Carbon redistribution processes in nanocarbons. Carbon 42, 1057–1061 (2004).

  16. 16.

    & Conversion of carbonaceous material to graphite during metamorphism. Geochim. Cosmochim. Acta 49, 2003–2016 (1985).

  17. 17.

    , & Poorly crystalline carbonaceous matter in high-grade metasediments—implications for graphitization and metamorphic fluid compositions. Contrib. Mineral. Petrol. 116, 108–116 (1994).

  18. 18.

    , , & Graphitization of Korean anthracites as studied by transmission electron microscopy and X-ray diffraction. Int. J. Coal Geol. 8, 375–393 (1987).

  19. 19.

    & Structure, microtexture, and optical properties of anthracene and saccharose-based carbons. Carbon 27, 517–529 (1989).

  20. 20.

    , & Mechanisms of graphite formation from kerogen: Experimental evidence. Int. J. Coal Geol. 28, 1–36 (1995).

  21. 21.

    et al. Graphitization in a high-pressure, low-temperature metamorphic gradient: A Raman microspectroscopy and HRTEM study. Contrib. Mineral. Petrol 143, 19–31 (2002).

  22. 22.

    et al. Mineral-templated growth of natural graphite films. Geochim. Cosmochim. Acta 83, 252–262 (2012).

  23. 23.

    et al. High resolution TEM of chondritic carbonaceous matter: Metamorphic evolution and heterogeneity. Meteorit. Planet. Sci. 47, 345–362 (2012).

  24. 24.

    et al. Inexpensive, upscalable nanotube growth methods. Curr. Appl. Phys. 6, 135–140 (2006).

Download references

Acknowledgements

We thank E. Aoyagi for technical assistance with STEM and HRTEM observations. The isotope ratio mass spectrometer (infrared-MS) analyses were carried out with support from T. Watanabe and F. W. Nara. The manuscript was improved by discussions with Y. Furukawa and T. Otake. This study was supported by the Japan Society for the Promotion of Science (grants 17403011 and 21403009).

Author information

Affiliations

  1. Natural Resources and Environmental Geochemistry Research Group, Division of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, 980-8578, Japan

    • Yoko Ohtomo
    • , Takeshi Kakegawa
    • , Akizumi Ishida
    •  & Toshiro Nagase
  2. Nordic Center for Earth Evolution, Natural History Museum of Denmark, University of Copenhagen, 1350, Denmark

    • Minik T. Rosing

Authors

  1. Search for Yoko Ohtomo in:

  2. Search for Takeshi Kakegawa in:

  3. Search for Akizumi Ishida in:

  4. Search for Toshiro Nagase in:

  5. Search for Minik T. Rosing in:

Contributions

Y.O., T.K. and M.T.R. conducted the geological surveys and collected rock samples. Y.O. carried out the geological and petrographical analyses, carbon stable isotope analyses of graphite using the graphite combustion method, XRD analyses, HRTEM observations and thermodynamic/isotopic calculations. A.I. and T.N. contributed to sample preparation and HRTEM observations. T.K. carried out carbon stable isotope analyses of graphite using the in situ Nd–YAG laser microprobe technique, STEM observations and Raman microspectroscopic analyses.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Yoko Ohtomo.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Information

Excel files

  1. 1.

    Supplementary Information

    Supplementary Information

  2. 2.

    Supplementary Information

    Supplementary Information

  3. 3.

    Supplementary Information

    Supplementary Information

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/ngeo2025

Further reading