Recycling of Graphite During Himalayan Erosion: A Geological Stabilization of Carbon in the Crust
Valier Galy,1,2*
Olivier Beyssac,3
Christian France-Lanord,2
Timothy Eglinton1
At geological time scales, the role of continental erosion in
the organic carbon (OC) cycle is determined by the balance between
recent OC burial and petrogenic OC oxidation. Evaluating its
net effect on the concentration of carbon dioxide and dioxygen
in the atmosphere requires the fate of petrogenic OC to be assessed.
Here, we report a multiscale (nanometer to micrometer) structural
characterization of petrogenic OC in the Himalayan system. We
show that graphitic carbon is preserved and buried in marine
sediments, while the less graphitized forms are oxidized during
fluvial transport. Radiocarbon dating indicates that 30 to 50%
of the carbon initially present in the Himalayan rocks is conserved
during the erosion cycle. Graphitization during metamorphism
thus stabilizes carbon in the crust over geological time scales.
2 Centre de Recherches Pétrographique et Géochimiques, CNRS, Institut National des Sciences de l'Univers (INSU), Nancy Université, BP 20, 54501 Vandœuvre-lès-Nancy, France.
3 Laboratoire de Géologie, Ecole Normale Supérieure, CNRS-UMR 8538, 24 Rue Lhomond, F-75005 Paris Cedex 5, France.
* To whom correspondence should be addressed. E-mail: vgaly{at}whoi.edu
