Very little water is necessary to make a dry solid silicate system wet

The standard rim-forming mineral reaction olivine + quartz = orthopyroxene (Ol + Qtz + Opx) has been experimentally performed at very dry conditions, i.e., only 20 wt ppm of water present in the sample container as a fluid, and most "water" was hydrogen dissolved within the solid crystals....

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Bibliographic Details
Published in:Geology (Boulder) 2013-02, Vol.41 (2), p.247-250
Main Authors: Milke, Ralf, Neusser, Gregor, Kolzer, Kornelia, Wunder, Bernd
Format: Article
Language:English
Subjects:
chain silicates
chemical reactions
eclogite facies
experimental studies
facies
framework silicates
geochemistry
granulite facies
high pressure
high temperature
hydrogen
igneous and metamorphic rocks
kinetics
laboratory studies
metamorphic rocks
Mineralogy
nesosilicates
olivine group
orthopyroxene
orthosilicates
Petrology
porosity
pressure
pyroxene group
quartz
silica minerals
silicates
solid phase
temperature
water content
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Summary:The standard rim-forming mineral reaction olivine + quartz = orthopyroxene (Ol + Qtz + Opx) has been experimentally performed at very dry conditions, i.e., only 20 wt ppm of water present in the sample container as a fluid, and most "water" was hydrogen dissolved within the solid crystals. Reaction rates and resulting fabrics at Ol-Qtz interfaces mimic reaction features previously known from water-rich conditions (tens of thousands ppm). Our experiment indicates that very small amounts of water (tens of ppm of the entire sample) are highly effective in facilitating mineral reactions where water acts as a catalyst and creates porosity that might start to migrate from the initial centers of self-propagating mineral reaction, if rock deformation allows. The threshold between dry and wet in granulite and eclogite facies rocks is crossed once the nominally anhydrous minerals are saturated with hydrogen.
ISSN:0091-7613
1943-2682
DOI:10.1130/G33674.1