Mobilizing aluminum in crustal and mantle fluids

Aluminum is a major rock-forming element, but its low solubility in H2O at upper crustal conditions has led to the assumption that it is effectively immobile during fluid–rock interaction in the deep crust and upper mantle. However, new experimental results on Al solubility in H2O–SiO2–NaCl fluids at high pressure and temperature challenge this view. The combined effects of temperature, pressure, dissolved SiO2 and NaCl yield increases in corundum (Al2O3) solubility at 800°C, 1GPa of N10 3 or 10 relative to that at b0.3GPa in pure H2O. Enhancement of Al solubility is best explained by formation of polynuclear Na–Al–Si–O clusters and/or polymers. Aluminum should not be assumed to be immobile during fluid–rock interaction in deep environments. © 2006 Elsevier B.V. All rights reserved.