Abstrakt: |
Strongly acidic chloride-sulfide hydrothermal solutions altered ejecta from the Central Ebeko crater. The solutions formed by oxidation of magmatic emanations and produced concentric zones of differential alteration in individual blocks known as “cockade” structure. It is postulated that chloride-rich solutions penetrated the core of blocks while chloride-sulfate solutions affected intermediate portions and sulfate-rich solutions were not active around the periphery of blocks. Chemical and mineralogical analyses indicate that Cl, H2O and S were added to the blocks while alumina, the alkali and alkaline earth metals were leached. SiO2 and porosity were relatively increased from the core outward. Alteration products include iron chlorides, hydromicas, zunyite (?), alunite, leucoxene, rutile, sulfur and opal. — R. C. Epis. |