Mineralogy and geochemistry associated with hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy

A rhyolitic hyaloclastite from Ponza island, Italy, has been hydrothermally altered producing four distinct alteration zones based on XRD and field textures: (1) non-pervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is a volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the non-pervasive argillic zone, characterized by smectite and disordered opal-CT. The other three zones exhibit more complete alteration of the hyaloclastite. The propylitic zone is characterized by mixed-layer illite/smectite (I/S) with 10 to 85% I, mordenite, opal-C, and authigenic K-feldspar (akspar). The silicic zone is characterized by I/S with $\ge$90% I, pure illite, quartz, akspar, and occasional albite. In the sericitic zone the hyaloclastite altered primarily to illitic I/S with $\ge$66% I, pure illite, quartz, and minor akspar and pyrite. K/Ar ages of I/S indicate hydrothermal alteration occurred at 3.32 $\pm$ 0.13Ma.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Geology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Ylagan, Robert Francis

Contributors dc:contributor

• Altaner, Stephen P.

• Geology
• Mineralogy
• Geochemistry

Statement dc:rights

• Copyright 1996 Ylagan, Robert Francis

Language dc:language

eng

Identifier

9780591199765
AAI9712494
(UMI)AAI9712494

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/20089