Zeolite associated with silicification in a volcano-sedimentary context, southern Brazil

Abstract

In the Paraná Basin context, a volcano-sedimentary interaction is noticeable and some remarkable zeolite aggregates appear in the sediments deposited inside volcanic cavities (mega vesicles). Silicification is likewise associated with sediments. Consequently, analysis such as petrography, X-ray diffraction, Scanning Electron Microscopy, and mainly electronic microprobe confirmed the clinoptilolite. This type of zeolite, under the given conditions, is attributed to low temperatures and appears in a feature known as geodes with sediments. Clinoptilolite is formed from the alteration of the volcanic host rock. This alteration develops by dissolution, remobilization, and precipitation and can form silicification and zeolitization. The study of this association contributes to the understanding of post-magmatic processes, sedimentary processes, dissolution of the volcanic host rock, remobilization of silica, and then precipitation of silica and zeolite as cementation in the sediments. Since this feature is in the context of volcanic alteration rocks and intense fracturing, the framework suggests a permeable and porous system that contributed to processes like infiltration, transportation, silicification, and zeolitization as cementation. Furthermore, a formation and deposition model for the geodes with sediments feature is also suggested for this context.