Zeolitization of tuffs at Quinamávida, central southern Chile

• Published in: Clays and clay minerals Vol. 55; no. 5; pp. 524 - 533
• Main Authors: Bascuñan, Sophía, Kelm, Ursula, Sanhueza, Vilma, Alfaro, Guillermo
• Format: Journal Article
• Language: English
• Published: Boulder, CO Clay Minerals Society 01.10.2007; The Clay Minerals Society
• Subjects: Cenozoic; Chile; Clinoptilolite; Colbun Formation; Earth sciences; Earth, ocean, space; Exact sciences and technology; framework silicates; Heulandite; igneous and metamorphic rocks; igneous rocks; metasomatism; Mineralogy; Mordenite; Petrology; pyroclastics; Quinamavida Chile; Silicates; South America; south-central Chile; Tertiary; transformations; Tuff; volcanic rocks; Zeolite; zeolite group; zeolitization; Chile; South America; thickness; fine-grained materials; mineralogy; feldspar; hydrogen; mordenite; volcanism; clinoptilolite; heulandite; sheet silicates; silicates; ions; framework silicates; heat flow; lakes; Cenozoic; Chile; zeolitization; cations; lenses; volcanic rocks; Tertiary; quartz; igneous rocks; climate; plagioclase; smectite; pyroclastics; zeolite; tuff; clay minerals; lapilli; Phanerozoic
• ISSN: 0009-8604; 1552-8367
• DOI: 10.1346/CCMN.2007.0550507

Tuffs of the Tertiary Colbun Formation near Quinamavida in central southern Chile have been mapped and their mineralogy analyzed. The pyroclastic rocks present a maximum outcropping thickness of 120 m and are dominated by vitreous lapilli and minor lithic tuffs, the products of active volcanism nearby. About 10% of the tuffs consist of lenses of fine banded tuffs with a high leaf content that were deposited in shallow lakes during quiescent periods between periods of volcanic activity. This tuff sequence is pervasively transformed to clinoptilolite/heulandite and mordenite with variable amounts of plagioclase, minor quartz and smectite. Factors thought to have influenced this conversion to zeolites are a humid climate following deposition combined with a slightly elevated heat flow. Local hydrogeological conditions have modified the cation-hydrogen ion ratios across the study area favoring the formation of clinoptilolite/heulandite and mordenite with medium-minor smectite in the center and south, and a more abundant presence of smectite in the north of the study area.