The most common hydrothermal alteration products of the basalts with spindle, in São Gabriel / Planalto Village, are clay-minerals, zeolites, calcite and silica (quartz, opal and chalcedony). The petrographic observation and the geochemical data allowed to identify the secondary phases of filling of the shaft. This filling occurs from the periphery to its center by: a) brown clay-mineral (ferri-montmorillonite), b) prismatic zolite (heulandite) and / or fibro-radiated interlayer saponite / chlorite and c) saponite / chlorite.
