Photomicrographs of selected thin-sections of the four studied lithofacies showing a) recrystallized and argillized groundmass with altered rock fragments and very fractured plagioclases; b) groundmass prevalently composed by deformed glass with some microlites of plagioclase and quartz; c) Inequigranular groundmass with plagioclase and quartz microlites embedded in interstitial glass; d) plagioclase embedded in an argillized groundmass, where some oxides are visible. Abbreviations are: plg = plagioclase, arg = Al-lh = altered lithics, Ar = argillization, Mi = microlites of quartz and plagioclase. 

Contexts in source publication

Context 1

... fine-rich green-ash matrix with small frag- ments of dense lithics (mm in size) (Figs. 4a and 5). The mpa is poorly sorted and with no stratification or grading, sometimes showing orien- tated or lens-shaped pumice fragments. Major constituents are plagio- clase, amorphous silica, and phyllosilicates (montmorillonite) in the groundmass (Table 2, Fig. 6). Thin-sections show a recrystallized groundmass, composed prevalently of glass and some euhedral to sub-euhedral phenocrysts of fractured and corroded plagioclases, quartz, pyroxenes and Fe-Ti oxides (Fig. ...

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... pumice fragments. Major constituents are plagio- clase, amorphous silica, and phyllosilicates (montmorillonite) in the groundmass (Table 2, Fig. 6). Thin-sections show a recrystallized groundmass, composed prevalently of glass and some euhedral to sub-euhedral phenocrysts of fractured and corroded plagioclases, quartz, pyroxenes and Fe-Ti oxides (Fig. ...

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... massive lithic-lapilli lithofacies ( Table 2) is composed of subrounded and vesiculated lithic fragments (light-gray, black, red) and pumice (from mm to cm in size), supported in a fine-rich light- brown-ash matrix (Figs. 4b and 5). Major constituents are plagioclase, amorphous silica, and phyllosilicates (montmorillonite) ( Table 2 and Fig. 6). The groundmass is composed prevalently of deformed glass with some microlites of plagioclase and quartz. Some euhedral and sub-euhedral phenocrysts of plagioclase are observed, together with quartz, Fe-Ti oxides and argillitic stains in the groundmass and within some altered minerals (Fig. ...

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... and phyllosilicates (montmorillonite) ( Table 2 and Fig. 6). The groundmass is composed prevalently of deformed glass with some microlites of plagioclase and quartz. Some euhedral and sub-euhedral phenocrysts of plagioclase are observed, together with quartz, Fe-Ti oxides and argillitic stains in the groundmass and within some altered minerals (Fig. ...

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... fragments (from mm to cm in size), support- ed in a fine-rich brown-ash matrix (Figs. 4c, d, and 5). It presents several layers with specific grain-size, grain shape, sorting, and compositional characteristics (Figs. 4c, d, and 5). Major constituents are plagioclase, amorphous silica, calcite, and phyllosilicates (montmorillonite) ( Table 2 and Fig. 6). The groundmass consists of very argillized glass with some microlites of pyroxenes and a large content of very altered lithics. Samples contain phenocrysts of angular plagioclases, pyroxenes, quartz, and Fe-Ti ( Fig. 6c and d). Due to the stratified structure of this lithofacies, the petrophysical characterization was carried out on ...

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... d, and 5). Major constituents are plagioclase, amorphous silica, calcite, and phyllosilicates (montmorillonite) ( Table 2 and Fig. 6). The groundmass consists of very argillized glass with some microlites of pyroxenes and a large content of very altered lithics. Samples contain phenocrysts of angular plagioclases, pyroxenes, quartz, and Fe-Ti ( Fig. 6c and d). Due to the stratified structure of this lithofacies, the petrophysical characterization was carried out on sam- ples oriented parallel and perpendicularly to layering and named spl-a and spl-b, respectively ( Fig. 4c and ...