Geothermal Exploration Of La Soufriere Volcano, St Vincent, West Indies

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Conference Paper: Geothermal Exploration Of La Soufriere Volcano, St Vincent, West Indies

Geothermal exploration in the northern half of the island on St. Vincent, West Indies revealed a possible geothermal system centered in the vicinity of the La Soufriere volcano. Mapping has shown abundant pyroclastic and other volcanic deposits throughout the island, indicating a prolific volcanic history, one which has included two eruptions of La Soufriere within the past 40 years. Almost all eruptions are of the central vent type, providing a spatial constraint on the extent of a related geothermal system. Geothermal exploration included geologic mapping, remote sensing and geochemical sampling and analysis of surface manifestations of the geothermal and hydrological system. Three areas were selected for a detailed, controlled source audiomagnetotellurics survey of which two were surveyed. A regional study was completed to evaluate the electrical structure of the volcano. Limited surface manifestations of the potential geothermal system in the vicinity of La Soufriere included: fumaroles discharging from the center of the La Soufriere carter; warm waters discharging along the Wallibou River; and possible evidence of geothermal influx in other springs. Results of chemical and isotopic analysis of fumarolic steam and gas samples suggest that the fumarolic steam is locally recharged by rainwater boiling at approximately 170°C and is discharged along with an influx of geothermal gases from high-temperature sources above 250 "C. Chemical analysis of warm spring waters that discharge as a series of high volume, warm springs occurring along the northern bank of Wallibou River suggest that these springs are a mixture between meteoric water and geothermal brine. The geothermal brine appears to be characterized as a neutral, hot (>150 "C), and low TDS (e1000 mgkg) with a magmatic influx. Results of the initial exploration effort suggest that a potential geothermal system underlies the La Sourfriere volcano consisting of a deeper geothermal brine, which flows up along fractures or other permeable zones on the southern flanks of the volcano, mixes with meteoric water and discharges along the Wallibou River. A small amount of shallow local boiling in the immediate vicinity of the volcanic vent discharges as fumaroles with higher temperature geothermal gases along with stearn. The hot-water vicinity of the La Soufriere volcano which occupies the northern third of the island. Field activities were completed under contract to EGS Inc of Santa Rosa between June 1997 and July 1998, at which time initial drilling targets had been identified. No further work has been completed on the project due to political and economic conditions. The objective of the exploration project was to identify geothermal resources sufficient to supply the islands with its electrical power needs. Currently the island has an approx~ate10 -12 megawatts ( W e ) load which is met primarily by imports of diesel fuel, supplemented by local hydro-electric power (- 4MWe)

Paul Brophy and Jill Haizlip

GRC, 2003

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Paul Brophy,Jill Haizlip. 2003. Geothermal Exploration Of La Soufriere Volcano, St Vincent, West Indies. In: (!) ; (!) ; (!) . (!) : GRC; p. (!)