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Spatial and depth‐dependent variations in magma volume addition and addition rates to continental arcs: Application to global CO_2 fluxes since 750 Ma

Ratschbacher, Barbara C. and Paterson, Scott R. and Fischer, Tobias P. (2019) Spatial and depth‐dependent variations in magma volume addition and addition rates to continental arcs: Application to global CO_2 fluxes since 750 Ma. Geochemistry, Geophysics, Geosystems, 20 (6). pp. 2997-3018. ISSN 1525-2027. https://resolver.caltech.edu/CaltechAUTHORS:20190510-112548998

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Abstract

Magma transfer from the mantle to the crust in arcs is an important step in the global cycling of elements and volatiles from Earth's interior to the atmosphere. Arc intrusive rocks dominate the total magma mass budget over extrusive rocks. However, their total volume and rate of addition is still poorly constrained, especially in continental arcs. We present lateral (forearc to backarc) and depth‐dependent (volcanics to deep crust) magma volume additions and arc‐wide magma addition rates (MARs) calculated from three continental arc crustal sections preserving magma flare‐up periods. We observe an increase in volume addition with depth and less magma added in the forearc (~15%) and backarc (~10% to 30%) compared to the main arc. Crustal‐wide MARs for each section are remarkably similar and around 0.7–0.9 km^3/km^2/Ma. MARs can be used to estimate CO_2 fluxes from continental arcs. With initial magma CO_2 contents of 1.5 wt.%, global continental arc lengths, and MARs, we calculate changes in C (Mt/year) released from continental arcs since 750 Ma. Calculated present‐day global C fluxes are similar to values constrained by other methods. Throughout the Phanerozoic, assuming equal durations of flare‐up and lull magmatism, calculated continental CO_2 flux rates vary between 4 and 18 Mt C/year with highest values in the Mesozoic. These fluxes are considered minima since the intake of mantle and/or crustal carbon is not considered. Magmatic episodicity in continental arcs and changes in arc thickness and width are critical to consider when calculating MARs through time.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2018gc008031DOIArticle
ORCID:
AuthorORCID
Ratschbacher, Barbara C.0000-0002-2112-7225
Fischer, Tobias P.0000-0002-3467-0649
Alternate Title:Spatial and depth‐dependent variations in magma volume addition and addition rates to continental arcs: Application to global CO2 fluxes since 750 Ma
Additional Information:© 2019 American Geophysical Union. Received 23 OCT 2018; Accepted 5 MAY 2019; Accepted article online 9 MAY 2019; Published online 25 JUN 2019. B. R. thanks CIDER (EAR‐1135452) for the possibility to participate in the 2017 summer workshops, which lead to the introduction to T. P. F. and the idea for this paper. We thank Pablo Alasino and Mariano Larrovere for their discussion on the Famatinian arc. S. P. acknowledges NSF support through EAR 1624847 and 0948680. We also thank Marie Edmonds for the editorial handing and Sabin Zahirovic and two anonymous reviewers for their thoughtful comments. Information about studied areas including map compilations, estimates on depth of exposed sections, and age constrains can be accessed in the supporting information.
Funders:
Funding AgencyGrant Number
NSFEAR-1135452
NSFEAR-1624847
NSFEAR-0948680
Subject Keywords:magma addition rates; continental arcs; CO_2 degassing
Issue or Number:6
Record Number:CaltechAUTHORS:20190510-112548998
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190510-112548998
Official Citation:Ratschbacher, B. C., Paterson, S. R., & Fischer, T. P. ( 2019). Spatial and depth‐dependent variations in magma volume addition and addition rates to continental arcs: Application to global CO2 fluxes since 750 Ma. Geochemistry, Geophysics, Geosystems, 20, 2997–3018. https://doi.org/10.1029/2018GC008031
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95397
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:10 May 2019 20:36
Last Modified:04 Dec 2019 18:27

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