Evan J. Ramos*
Dept. of Geological Sciences, University of Texas, Austin, Texas 78712, USA
Jade Star Lackey
Geology Dept., Pomona College, Claremont, California 91711, USA
Jaime D. Barnes
Dept. of Geological Sciences, University of Texas, Austin, Texas 78712, USA
Anne A. Fulton**
Geology Dept., Pomona College, Claremont, California 91711, USA
Abstract
Metamorphic decarbonation in magmatic arcs remains a challenge to impose in models of the
geologic carbon cycle. Crustal reservoirs and metamorphic fluxes of carbon vary with depth in
the crust, rock types and their stratigraphic succession, and through geologic time. When
byproducts of metamorphic decarbonation (e.g., skarns) are exposed at Earth’s surface, they
reveal a record of reactive transport of carbon dioxide (CO2). In this paper, we
discuss the different modes of metamorphic decarbonation at multiple spatial and temporal scales
and exemplify them through roof pendants of the Sierra Nevada batholith. We emphasize the
utility of analogue models for metamorphic decarbonation to generate a range of decarbonation
fluxes throughout the Cretaceous. Our model predicts that metamorphic CO2 fluxes from
continental arcs during the Cretaceous were at least 2 times greater than the present cumulative
CO2 flux from volcanoes, agreeing with previous estimates and further suggesting that
metamorphic decarbonation was a principal driver of the Cretaceous hothouse climate. We lastly
argue that our modeling framework can be used to quantify decarbonation fluxes throughout the
Phanerozoic and thereby refine Earth systems models for paleoclimate reconstruction.
* Corresponding author: ejramos@utexas.edu.
** Now at Dept. of Geology and Geological Engineering, Colorado School of Mines,
Golden, Colorado 80401, USA.
Manuscript received 2 Dec. 2019. Revised manuscript received 11 Feb. 2020.
Manuscript accepted 13 Feb. 2020. Posted 4 March 2020.
© The Geological Society of America, 2020. CC-BY-NC.
https://doi.org/10.1130/GSATG432A.1