Silica coatings on young Hawaiian basalts: Constraints on formation mechanism from silicon isotopes

Abstract

Young basalts from Kilauea, on the big island of Hawai'i, frequently feature visually striking, white, orange and blue coatings, consisting of a 10-50 μm layer of amorphous silica, capped, in some cases, by a ~1 μm layer of Fe-Ti oxide [1]. The coatings provide an opportunity to study the early onset of acid-sulfate weathering, a process common to many volcanic environments. Silicon isotopes fractionate with the precipitation of clays and opaline silica, and have been demonstrated to be an indicator of weathering intensity [2,3]. Here we report in situ measurements of δ^(30)_Si of the silica coatings and their implications for coating formation.

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