Corrosion of Natural Glasses in Seawater

Abstract

Chemical alteration of basalt glasses in seawater ranks as one of the most important global Earth processes, playing a significant role in the terrestrial carbon cycle, the chemical composition of the oceans, and the cycling of major, minor and trace elements between the crust and the mantle. This chapter examines abiotic and biotic processes that drive seafloor alteration of basaltic glasses.Biotic alteration depends on specific metabolic processes that supply energy to microorganisms, and at the same time, serve to breakdown the glass structure. Several representative studies illustrate current models of abiotic and biotic basalt glass dissolution. In most cases, the predominant alteration product is palagonite, a secondary surficial phase that grows at the expense of the glass. Its physical and chemical properties indicate how it forms, which in turn is linked to the glass corrosion mechanism. Each study is discussed in light of the two currently accepted corrosion mechanisms: the cation-depleted leached layer model and the coupled interfacial dissolution-reprecipitation (CIDR) model.