Alteration of glass as a possible source of clay minerals on Mars

Abstract

Thermodynamic calculations show that, under present Martian surface conditions, favorable gas‐solid weathering products of feldspar glasses should include beidellites (clays of the montmorillonite series) + carbonates + quartz. The gas‐solid weathering of mafic Silicate glass (of volcanic or impact origin) may similarly favor the production of metastable Fe‐rich montmorillonite clays. Simple mass‐balance calculations suggest that gas‐solid weathering of a Martian proto‐regolith containing 10% glass could conceivably produce a global blanket of clays at a rate ≥ 0.4 cm/109 yr. The production rate should be expected to increase significantly with the glass content and rate of reworking of the proto‐regolith and with the availability of water. Complete extraction of altered glass from a lunar‐like proto‐regolith might yield a global Martian clay blanket ∼10‐100 cm in thickness. Copyright 1978 by the American Geophysical Union.