HR: 1340h
AN: V43B-1588    [Abstracts]
TI: Geology and Geochemistry of volcanic hot springs on the island of Dominica, West Indies
AU: * Herlihy, R D
EM: alsmith@csusb.edu
AF: Department og Geological Sciences, California State University, San Bernardino, CA 92407 United States
AU: Smith, A L
EM: alsmith@csusb.edu
AF: Department og Geological Sciences, California State University, San Bernardino, CA 92407 United States
AU: Rheubottom, A N
EM: alsmith@csusb.edu
AF: Department og Geological Sciences, California State University, San Bernardino, CA 92407 United States
AU: Kirkley, J
EM: alsmith@csusb.edu
AF: Department og Geological Sciences, California State University, San Bernardino, CA 92407 United States
AU: Melchiorre, E
EM: emelch@csusb.edu
AF: Department og Geological Sciences, California State University, San Bernardino, CA 92407 United States
AU: Fryxell, J E
EM: jfryxell@csusb.edu
AF: Department og Geological Sciences, California State University, San Bernardino, CA 92407 United States
AU: Roobol, M J
EM: alsmith@csusb.edu
AF: Saudi Geological Society, PO Box 54141, Jeddah, 21514 Saudi Arabia
AB: The island of Dominica, located in the center of the Lesser Antilles island arc, contains at least 8 young volcanic centers. Evidence for the active nature of these centers include two historic phreatic eruptions (1880 AD and 1997 AD), at least 17 historic volcano-seismic crises and the presence of over 30 hot springs. These springs, which have been repeatedly sampled by us over a two-year period (2003-2004), can be divided, based on their geographic locations into at least 5 main groups: Group 1 (T~27‰C; pH ~1.6) are located near the summit of Morne aux Diables in the extreme north of the island; Group 2(T 48-101‰C; pH ~2.5) composed of both subaerial and submarine springs, are located on the western flanks of Morne Diablotins; Group 3 (T 48-102‰C; pH~3.5) are located within the Watten Woven caldera in west-central Dominica; Group 4 (T 74-98‰C; pH~3.5) are located within the Valley of Desolation in east central Dominica, the site of the two historic phreatic eruptions; Group 5 (T 61-106‰C; pH~1.6) composed of both subaerial and submarine springs, are located within the Soufriere Depression, a sector collapse structure in southwest Dominica. Over the period of the study the temperatures of many of the hot springs have shown small but measurable increases. With one exception, all of the springs can be regarded as belonging to the Ca-Mg-SO4 type. δO¹⁸ values of the spring waters range from 5.05 to -2.04 suggesting that significant water-rock exchange and alteration has occurred. Trends of decreasing. δO¹⁸ values at specific sites suggest a increasing volume of meteoric and/or sea water is entering the hydrothermal system, perhaps in response to increasing sub-surface temperature. Silica thermometry gives fluid source temperatures of between 51 and 197‰C depending on the site. Sr/Y versus Si data suggest that deep formation of economic-mineral deposits may be occurring beneath some of the hot spring areas.
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005