Conference Proceedings

THE SURFACE OF LABRADORITE FELDSPAR AFTER ACID-HYDROLYSIS

WH CASEY, HR WESTRICH, T MASSIS, JF BANFIELD, GW ARNOLD

CHEMICAL GEOLOGY | ELSEVIER SCIENCE BV | Published : 1989

Abstract

After reaction with a pH < 4, the surface of labradorite is extensively enriched in Si and H, and depleted in Al, Ca and Na relative to an unreacted crystal. However, the amount of hydrogen measured in the reacted surface is less than that predicted on the basis of exchange of hydrogen (or hydronium) ions for cations in the feldspar. By analogy with studies of silicate glass, this low concentration of hydrogen suggests that some silanol groups in the reacted surface repolymerize subsequent to ion-exchange and depolymerization reactions. The net result is a relatively porous, Si-rich leached layer which is amorphous to electron diffraction, and which allows rapid diffusion of unreactive solut..

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