Open AccessBroader Impacts of the Metasomatic Underplating Hypothesis
Author(s) -
Park Jeffrey,
Rye Danny M.
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 - 10.1029/2019gc008493
Subject(s) - metasomatism , geology , underplating , geochemistry , seawater , crust , mantle (geology) , subduction , brucite , peridotite , mantle wedge , carbonate , igneous rock , tectonics , oceanography , paleontology , materials science , metallurgy , magnesium
The “metasomatic underplating” hypothesis argues that crustal fractures develop during hot spot magma ascent to allow seawater to infiltrate and to serpentinize the sub‐Moho mantle. Published seismic velocities and layer thicknesses support estimates that 1 km of seawater could be chemically bound within an underplated layer, which may require 2–4 Myr to mature. If a serpentinized mantle layer underlies hot spot tracks and/or aseismic ridges, their buoyancy can induce flat‐slab behavior within subduction zones (e.g., beneath central Chile and Peru), weaken slab rheology, and foster slab tears. During serpentinization, metasomatic underplating would produce more serpentine and talc and less brucite and magnetite, if seawater equilibrates with silica in the gabbroic oceanic crust as it descends to the Moho. The restricted solubility of carbonate with temperature may induce seawater CO 2 to sequester in the crust as carbonate concretions or intergrowths. Consumption of seawater H 2 O by serpentinization raises its salinity so that Fe cations stabilize in chloride complexes and depart the open system. Alkali cations in seawater contribute to the sodic metasomatism of pyroxenes, analogous to alterations observed in abyssal peridotites.