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Mineralogy, Geochemistry and Genesis of Zeolites in Cenozoic Pyroclastic Flows from the Asuni Area (Central Sardinia, Italy)

Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Via Diocleziano 328, 80124 Napoli, Italy
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Minerals 2020, 10(3), 268; https://doi.org/10.3390/min10030268
Received: 23 December 2019 / Revised: 13 March 2020 / Accepted: 14 March 2020 / Published: 16 March 2020
Natural zeolite occurrences have been recognized in several Cenozoic pyroclastic deposits in central Sardinia. This study concerns the mineralogical and geochemical characterization of the zeolitized tuffites in the Asuni area (Oristano province) and aims to complement information regarding the zeolitization processes developed in the nearby Allai deposits. Optical and scanning electron microscopy, X-ray powder diffraction, qualitative vs. quantitative microanalyses and bulk-rock geochemistry were performed. Analytical results allow defining the mineral distribution, textural relationships and geochemical features of the zeolite-bearing rocks. The most abundant secondary minerals are Ca-Na mordenites. Contrarily to the most common worldwide clinoptilolite + mordenite paragenesis, mordenite is dominant and occurs in different morphologies, rarely coexisting with clinoptilolite in the studied volcanic tuffites. Glauconite and dioctahedral smectite complete the authigenic assemblages. The primary volcanic components mostly include plagioclase, quartz and glass shards, roughly retaining their original appearance. The tuffites range in composition from dacite to rhyolite. The collected dataset shows that zeolitization is most abundant in coarser-grained deposits and points to a genetic process that mainly involves an open hydrothermal environment governed by aqueous fluids with significant marine component, in post eruption conditions. View Full-Text
Keywords: central Sardinia; tuffites; high-silica zeolites; Mordenite; open-hydrothermal system central Sardinia; tuffites; high-silica zeolites; Mordenite; open-hydrothermal system
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Mormone, A.; Piochi, M. Mineralogy, Geochemistry and Genesis of Zeolites in Cenozoic Pyroclastic Flows from the Asuni Area (Central Sardinia, Italy). Minerals 2020, 10, 268.

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