Abstract

The mineralogy and major element distribution of selected samples from 13 localities, comprising sedimentary and felsic volcanic rocks, are evaluated using Scanning Electron Microscopy Equipped with An Energy-Dispersive X-ray Spectrometry (SEM-EDS). This study aimed to characterize clay textures, identify mineral phases, and determine elemental composition and distribution. Precambrian pelites and tuffs show a composition dominated by illite, quartz and feldspar. Paleozoic sedimentary rocks show variations in clay composition: the Cordobés Formation is predominantly composed of kaolinite, while the Yaguarí Formation is characterized by montmorillonite. Rhyolites from the Lower Cretaceous Arequita Formation are composed of quartz, sanidine, volcanic glass and alteration product such as kaolinite and illite-smectite. The summatory of SiO₂+Al₂O₃+Fe₂O₃ above 70%, combined with the fineness and mineralogy of all analyzed rocks, when compared to similar examples from the literature, suggests their potential use as natural pozzolans after thermal treatment.

Keywords:SEM-EDS; Mineralogical characterization; Natural pozzolans; Felsic volcanic rocks; Sedimentary rocks; Uruguay