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CO 2 transfer between the upper mantle and the atmosphere: temporary storage in the lower continental crust
Author(s) -
Touret J.LR.
Publication year - 1992
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1992.tb00453.x
Subject(s) - geology , underplating , crust , continental crust , mantle (geology) , granulite , geochemistry , volcano , subduction , metamorphic rock , crustal recycling , petrology , earth science , tectonics , geomorphology , seismology , facies , structural basin
The CO 2 atmospheric content has shown large variations over geological times. High contents (up to one order of magnitude more than present‐day values) ultimately correspond to discrete episodes of mantle degassing, either juvenile, or subduction‐related (carbon recycling). A number of arguments (e.g. the continuous volume increase of carbonate‐bearing sediments with time) suggest that, throughout the Earth's history, juvenile CO 2 has formed a major contribution to the global carbon budget of the Earth. The absence of a direct relationship between major volcanic episodes and the average CO 2 atmospheric content suggests that volcanoes might not be the only way by which mantle CO 2 is transported to the surface. It is proposed that large quantities of juvenile CO 2 could temporarily be stored in the lower continental crust during major episodes of granulite formation. These are primarily caused by magmatic underplating and they result in a vertical accretion of the crust by accumulation of CO 2 ‐bearing, mantle‐derived magmas. Most of the CO 2 migrates through the crust during post‐metamorphic evolution and isostatic restoration of the normal continental thickness. However, large quantities of CO 2 can still be present in some areas, notably as high‐density fluids enclosed in minerals.