Subduction fluxes of water, carbon dioxide, chlorine, and potassium

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doi: 10.1029/2002GC000392
Author(s): Jarrard, Richard D.
Author Affiliation(s): Primary:
University of Utah, Department of Geology and Geophysics, Salt Lake City, UT, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 4(5). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 269 refs.; illus., incl. 2 tables
Summary: The alteration of upper oceanic crust entails growth of hydrous minerals and loss of macroporosity, with associated large-scale fluxes of H2O, CO2, Cl-, and K2O between seawater and crust. This age-dependent alteration can be quantified by combining a conceptual alteration model with observed age-dependent changes in crustal geophysical properties at DSDP/ODP sites, permitting estimation of crustal concentrations of H2O, CO2, Cl-, and K2O, given crustal age. Surprisingly, low-temperature alteration causes no net change in total water; pore water loss is nearly identical to bound water gain. Net change in total crustal K2O is also smaller than expected; the obvious low-temperature enrichment is partly offset by earlier high-temperature depletion, and most crustal K2O is primary rather than secondary. I calculate crustal concentrations of H2O, CO2, Cl-, and K2O for 41 modern subduction zones, thereby determining their modern mass fluxes both for individual subduction zones and globally. This data set is complemented by published flux determinations for subducting sediments at 26 of these subduction zones. Global mass fluxes among oceans, oceanic crust, continental crust, and mantle are calculated for H2O, Cl-, and K2O. Except for the present major imbalance between sedimentation and sediment subduction, most fluxes appear to be at or near steady state. I estimate that half to two thirds of subducted crustal water is later refluxed at the prism toe; most of the remaining water escapes at subarc depths, triggering partial melting. The flux of subducted volatiles, however, does not appear to correlate with either rate of arc magma generation or magnitude of interplate earthquakes.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; Alkali metals; Benioff zone; Carbon dioxide; Chlorine; Crust; Dehydration; Dikes; Gabbros; Geochemical cycle; Halogens; Hydrothermal alteration; Igneous rocks; Intrusions; Mass transfer; Metals; Metasomatism; Ocean Drilling Program; Oceanic crust; Peridotites; Permeability; Plate tectonics; Plutonic rocks; Porosity; Potassium; Sea water; Sediments; Seismicity; Subduction; Subduction zones; Ultramafics
Record ID: 2005069342
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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