Figure 5
From: Natural glass alteration under a hyperalkaline condition for about 4000 years
Lifetime of spherical glass grain at a given dissolution rate. The solid lines represent the lifetime of spherical glass as function of the grain radius (rad) and dissolution rate. The numbers above the lines denote the dissolution rates log rgeo (in mol m−2 s−1). Rates are cited from the following: rhyolite dissolution rates under near neutral pH at field, assuming a roughness factor of[a] 10 and [b] 100, respectively48. Rates were determined by experiments conducted at pH 10.6 at 25 °C46 [c], as well as at pH 11.2 at 28 °C47 [d]. The dissolution rate at pH 9.5, 28 °47 [e] is also shown as a gray line. In this study, the values for [c] were converted to match the volcanic glass composition, and the values for [d] and [e] were interpolated from the rates at different pH and temperatures. The broken line across the green square denotes the lifetime estimated at the maximum dissolution rate. Arrows A and B indicate constraints on grain radius and lifetime (see text for details); more realistic radius and lifetime are plotted in the upper left area of the square (shaded orange).
