The laboratory albitization of mid-ocean ridge basalt

Complete alteration of fresh mid-ocean ridge basalt to albite + actinolite + smectite took place in the presence of quartz and 3.4m NaCl at 350°C and 400 bars. Significant Na-metasomatism occurred in exchange for Ca + Fe + Mn. In contrast, alteration of the basalt/quartz mixture with a synthetically prepared "natural brine," and basalt with 3.4m NaCl or "natural brine" did not produce significant albitization. Based on these and previous experiments that reacted basalt with a variety of fluids, it is concluded that excess silica, a high Na/Ca ratio, and an absence of strong acidity (dissolved Mg) in the altering fluid are important for the albitization of basalt.