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
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.