CHEMICAL AND ISOTOPIC INVESTIGATIONS OF FUMAROLIC GASES FROM ISCHIA ISLAND (SOUTHERN ITALY) - EVIDENCES OF MAGMATIC AND CRUSTAL CONTRIBUTION

Authors
Citation
D. Tedesco, CHEMICAL AND ISOTOPIC INVESTIGATIONS OF FUMAROLIC GASES FROM ISCHIA ISLAND (SOUTHERN ITALY) - EVIDENCES OF MAGMATIC AND CRUSTAL CONTRIBUTION, Journal of volcanology and geothermal research, 74(3-4), 1996, pp. 233-242
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary
ISSN journal
0377-0273
Volume
74
Issue
3-4
Year of publication
1996
Pages
233 - 242
Database
ISI
SICI code
0377-0273(1996)74:3-4<233:CAIIOF>2.0.ZU;2-H
Abstract
Chemical and isotopic investigations have been carried out on subaeria l and submarine fumarolic fluids on the island of Ischia, Gulf of Napo li (Southern Italy). Chemical analyses of gases from the hottest fumar ole (117 degrees C) located on Mount Epomeo show a typical geothermal composition. Thermodynamic computations indicate a feeding source temp erature of Mt. Epomeo ranging from 300 to 500 degrees C. Isotopic comp ositions suggest that the island is divided into two parts (East and W est). Fumarole gases on the west side of the island indicate a magmati c source with small crustal contamination, and are characterized by ca rbon isotopic data similar to MORE (delta(13)C ranging from -3.5 to -5 .11 parts per thousand) with about 50% of the helium having a magmatic origin (3.6-3.7 R/R(a)). Fumaroles located on the east side of the is land have carbon isotopic data ranging from + 0.45 to - 0.76 parts per thousand and a lower helium isotopic ratio (from 2.09 to 2.89 R/R(2)) . The east fumaroles seem to be fed by fluids deriving from a reservoi r located in or close to a carbonatic source in the crust.