C. E. Manning S. E. Ingebritsen 1999 <div id="15578928" class="article-section-wrapper js-article-section js-content-section " data-section-parent-id="0"><p>The decrease in permeability (<i>k</i>) of the continental crust with depth (<i>z</i>), as constrained by geothermal data and calculated fluid flux during metamorphism, is given by log<span>&nbsp;</span><i>k</i><span>&nbsp;</span>= −14 − 3.2 log z, where<span>&nbsp;</span><i>k</i><span>&nbsp;</span>is in meters squared and z is in kilometers. At moderate to great crustal depths (&gt;∼5 km), this curve is defined mainly by data from prograde metamorphic systems, and is thus applicable to orogenic belts where the crust is being thickened and/or heated; lower permeabilities may occur in stable cratonic regions. This<span>&nbsp;</span><i>k-z</i><span>&nbsp;</span>relation implies that typical metamorphic fluid flux values of ∼10⁻¹¹<span>&nbsp;</span>m/s are consistent with fluid pressures significantly above hydrostatic values. The<span>&nbsp;</span><i>k-z</i><span>&nbsp;</span>curve also predicts that metamorphic CO₂<span>&nbsp;</span>flux from large orogens may be sufficient to cause significant climatic effects, if retrograde carbonation reactions are minimal, and suggests a significant capacity for diffuse degassing of Earth (10¹⁵–10¹⁶<span>&nbsp;</span>g/yr) in tectonically active regions.</p></div> application/pdf 10.1130/0091-7613(1999)027<1107:GIOAPD>2.3.CO;2 en Geological Society of America Geological implications of a permeability-depth curve for the continental crust article