The cation exchange capacities (CEC) and extractable cations in smectite, corrensite and palagonitized glass from hydrothermally-altered pillow lavas and hyaloclastite breccias were measured by both bulk wet chemical and in situ microanalytical techniques. Smectite has CEC's between 60 and 120 meq/100 g, palagonitized glass between 30 and 60 meq/100 g, and corrensite approximately 35 meq/100 g as determined by the in situ CsCl-exchange method. These experiments generally verify that Cs exchanges for those cations that are presumed (from the stoichiometry implied by microprobe analyses) to occupy interlayer sites in sheet silicates. Results of conventional CEC determinations are consistent with those determined by the in situ experiments: the individual microanalytical values for smectite and palagonitized glass bracket the bulk CEC values. The in situ experiments imply that Mg is the major extractable cation in smectite, Ca in corrensite, and both Mg and Ca in the palagonitized glass. We speculate that discrepancies between the equivalents of extractable cations predicted from elemental analysis and the equivalents of Cs sorbed may be due to the presence of charge-balancing protons that are not detected by the microprobe analyses. The sum of equivalents of cations extracted by NH4-acetate is about the same as the CEC determined by both the in situ and the bulk methods. Cation proportions indicated by NH4-acetate extractions from bulk samples are also generally consistent with the in situ results for all elements except Mg, which is a minor leachate of the NH4-acetate extractions in all the samples. To explain this discrepancy, we propose that 1) Mg may occupy structural sites within palagonitized glass, which inhibit its extraction by NH4 or Cs, and/or 2) there is a significant quantity of smectite, unsampled by the electron microprobe analyses, which contains insignificant interlayer Mg.

Three petrographically distinct styles of altered glasses in two hyaloclastites and one hyalotuff were studied. The texture and chemistry of these samples were investigated using electron probe microanalysis, scanning electron microscopy and transmission electron microscopy in order to understand better the mechanism by which alteration of sideromelane and formation of palagonite occurred in these samples. The results show that clay minerals (primarily smectites) are present in three different microenvironments: (1) coating the surfaces of glass and crystals or vesicle walls; (2) as a relatively heterogeneous, but well crystallized, replacement product (i.e. reddened smectite grain replacement or RSGR) of glass or; (3) as a relatively homogeneous, amorphous to poorly crystalline replacement product (i.e. palagonite). Both the grain size and composition of these smectite-like materials vary considerably.

Crystalline smectites occur in both hyaloclastites and have an intermediate composition between the two end-members nontronite and saponite. This composition could correspond to a mechanical intergrowth and/or an interstratification of two different smectites: one dioctahedral (i.e. nontronite) and one trioctahedral (i.e. saponite or stevensite) or simply to a true di-trioctahedral smectite. The coating smectite appears to have precipitated by a paragenetically-early, dissolution-precipitation mechanism prior to the formation of the RSGR. The high Ti content found in RSGR is attributable to an amorphous Ti-rich material which is intergrown with smectite and which behaves as a sink for immobile elements and those not included in smectite.

Palagonite from both hyaloclastites and hyalotuff is poorly to non-crystalline and more aluminous than the coating smectites. Palagonite from the hyalotuff has an Fe-rich montmorillonite-like composition. The TEM images show a 30–50 nm thick leached layer formed by selective (non-stoichiometric) dissolution that takes place in the fracture domain. The hydration and replacement of glass during the palgonitization process is accompanied by the loss of Fe, Mg and Ca with a concomitant gain of Al. Both palagonites (from hyaloclastites and hyalotuff) show smilar textural and chemical characteristics.

Layers of volcanic ash and Andosol soils derived from the ash may play an important role in preserving snow and ice as well as in the development of permafrost conditions in (a) the immediate vicinity of volcanoes at high elevations or at high latitudes and (b) land areas that are often distant from volcanic activity and are either prone to permafrost or covered by snow and ice, but have been affected by subaerial ash deposition. The special properties of volcanic ash are critically reviewed, particularly in relation to recent research in Kamchatka in the Far East of Russia. Of special importance are the thermal properties, the unfrozen water contents of ash layers, and the rate of volcanic glass weathering.Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite), but occurs at a much slower rate under cold compared to warm climate conditions. Existing data reveal (1) a strong correlation between the thermal conductivity, the water/ice content, and the mineralogy of the weathered part of the volcanic ash, (2) that an increase in the amounts of amorphous clay minerals (allophane, palagonite) increases the proportion of unfrozen water and decreases the thermal conductivity, and (3) that amorphous silica does not alter to halloysite or other clay minerals, even in the Early Pleistocene age (Kamchatka) volcanic ashes or in the Miocene and Pliocene deposits of Antarctica due to the cold temperatures. The significance of these findings are discussed in relation to past climate reconstruction and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.

Massive to lobate volcanic flows and brecciated hyaloclastite units in the Abitibi greenstone belt allow investigation of Late Archæan seafloor alteration and associated incorporation into these rocks of nitrogen (N) biogeochemical signatures. In this suite (the Blake River Group), hyaloclastite units containing putative microbial ichnofossils are particularly enriched in large-ion lithophile elements (K, Rb, Ba, Cs), B, and Li, consistent with their having experienced the greatest fluid–rock interaction during subseafloor hydrothermal alteration. Similarly, silicate-δ18O and δ15N values for samples from the hyaloclastites show the greatest shifts from plausible magmatic values. The chemical and isotopic patterns in these tholeiitic igneous rocks greatly resemble those in modern altered seafloor basalts, consistent with the preservation of an Archæan seafloor alteration signature. The N enrichments and shifts in δ15N appear to reflect stabilization of illite and interaction with fluids carrying sedimentary/organic signatures. Enrichments of N (and the δ15N of this N) in altered glass volcanic rocks on Earth's modern and ancient seafloor point to the potential utility of N for tracing past and present biogeochemical processes in similar rocks at/near the Mars surface.