Displaced cratonic mantle concentrates deep carbon during continental rifting

James D Muirhead; Tobias P Fischer; Sarah J Oliva; Amani Laizer; Jolante van Wijk; Claire A Currie; Hyunwoo Lee; Emily J Judd; Emmanuel Kazimoto; Yuji Sano; Naoto Takahata; Christel Tiberi; Stephen F Foley; Josef Dufek; Miriam C Reiss; Cynthia J Ebinger

doi:10.1038/s41586-020-2328-3

Displaced cratonic mantle concentrates deep carbon during continental rifting

Nature. 2020 Jun;582(7810):67-72. doi: 10.1038/s41586-020-2328-3. Epub 2020 Jun 3.

Authors

James D Muirhead^{1

2}, Tobias P Fischer³, Sarah J Oliva⁴, Amani Laizer⁵, Jolante van Wijk⁶, Claire A Currie⁷, Hyunwoo Lee⁸, Emily J Judd⁹, Emmanuel Kazimoto⁵, Yuji Sano¹⁰, Naoto Takahata¹⁰, Christel Tiberi¹¹, Stephen F Foley¹², Josef Dufek¹³, Miriam C Reiss¹⁴, Cynthia J Ebinger⁴

Affiliations

¹ Department of Earth Sciences, Syracuse University, Syracuse, NY, USA. james.muirhead@fulbrightmail.org.
² School of Environment, University of Auckland, Auckland, New Zealand. james.muirhead@fulbrightmail.org.
³ Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, USA. fischer@unm.edu.
⁴ Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA, USA.
⁵ Department of Geology, University of Dar es Salaam, Dar es Salaam, Tanzania.
⁶ New Mexico Institute of Mining and Technology, Socorro, NM, USA.
⁷ Department of Physics, University of Alberta, Edmonton, Alberta, Canada.
⁸ School of Earth and Environmental Sciences, Seoul National University, Seoul, South Korea.
⁹ Department of Earth Sciences, Syracuse University, Syracuse, NY, USA.
¹⁰ Atmosphere and Ocean Research Institute, University of Tokyo, Chiba, Japan.
¹¹ Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France.
¹² Department of Earth and Environmental Sciences, Macquarie University, North Ryde, New South Wales, Australia.
¹³ Department of Earth Sciences, University of Oregon, Eugene, OR, USA.
¹⁴ Institute of Geosciences, Goethe University Frankfurt, Frankfurt am Main, Germany.

PMID: 32494080
DOI: 10.1038/s41586-020-2328-3

Abstract

Continental rifts are important sources of mantle carbon dioxide (CO₂) emission into Earth's atmosphere^1-3. Because deep carbon is stored for long periods in the lithospheric mantle^4-6, rift CO₂ flux depends on lithospheric processes that control melt and volatile transport^1,3,7. The influence of compositional and thickness differences between Archaean and Proterozoic lithosphere on deep-carbon fluxes remains untested. Here we propose that displacement of carbon-enriched Tanzanian cratonic mantle concentrates deep carbon below parts of the East African Rift System. Sources and fluxes of CO₂ and helium are examined over a 350-kilometre-long transect crossing the boundary between orogenic (Natron and Magadi basins) and cratonic (Balangida and Manyara basins) lithosphere from north to south. Areas of diffuse CO₂ degassing exhibit increasing mantle CO₂ flux and ³He/⁴He ratios as the rift transitions from Archaean (cratonic) to Proterozoic (orogenic) lithosphere. Active carbonatite magmatism also occurs near the craton edge. These data indicate that advection of the root of thick Archaean lithosphere laterally to the base of the much thinner adjacent Proterozoic lithosphere creates a zone of highly concentrated deep carbon. This mode of deep-carbon extraction may increase CO₂ fluxes in some continental rifts, helping to control the production and location of carbonate-rich magmas.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.