Open AccessCarbon Fluxes and Primary Magma CO 2 Contents Along the Global Mid‐Ocean Ridge System
Author(s) -
Le Voyer Marion,
Hauri Erik H.,
Cottrell Elizabeth,
Kelley Katherine A.,
Salters Vincent J. M.,
Langmuir Charles H.,
Hilton David R.,
Barry Peter H.,
Füri Evelyn
Publication year - 2019
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2018gc007630
Subject(s) - geology , basalt , flux (metallurgy) , ridge , magma , mid ocean ridge , geochemistry , magma chamber , volcano , chemistry , paleontology , organic chemistry
The concentration of carbon in primary mid‐ocean ridge basalts (MORBs), and the associated fluxes of CO 2 outgassed at ocean ridges, is examined through new data obtained by secondary ion mass spectrometry (SIMS) on 753 globally distributed MORB glasses. MORB glasses are typically 80–90% degassed of CO 2 . We thus use the limited range in CO 2 /Ba (81.3 ± 23) and CO 2 /Rb (991 ± 129), derived from undegassed MORB and MORB melt inclusions, to estimate primary CO 2 concentrations for ridges that have Ba and/or Rb data. When combined with quality‐controlled volatile‐element data from the literature ( n = 2,446), these data constrain a range of primary CO 2 abundances that vary from 104 ppm to 1.90 wt%. Segment‐scale data reveal a range in MORB magma flux varying by a factor of 440 (from 6.8 × 10 5 to 3.0 × 10 8 m 3 /year) and an integrated global MORB magma flux of 16.5 ± 1.6 km 3 /year. When combined with CO 2 /Ba and CO 2 /Rb‐derived primary magma CO 2 abundances, the calculated segment‐scale CO 2 fluxes vary by more than 3 orders of magnitude (3.3 × 10 7 to 4.0 × 10 10 mol/year) and sum to an integrated global MORB CO 2 flux of 1.32 0.85 + 0.77 × 10 12 mol/year. Variations in ridge CO 2 fluxes have a muted effect on global climate; however, because the vast majority of CO 2 degassed at ridges is dissolved into seawater and enters the marine bicarbonate cycle. MORB degassing would thus only contribute to long‐term variations in climate via degassing directly into the atmosphere in shallow‐water areas or where the ridge system is exposed above sea level.