Exploration drilling and reservoir model of the Platanares geothermal system, Honduras, Central America

Goff, Fraser; Goff, S.; Kelkar, Sharad; Shevenell, Lisa; Truesdell, A.H.; Musgrave, John; Rüfenacht, Heinz; Flores, Wilmer

doi:10.1016/0377-0273(91)90025-u

Cited by 24 publications

(6 citation statements)

References 13 publications

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“…In order to extend the study to the northern portion of the Central American volcanic arc, gas data are shown for several hot springs and fumaroles in Guatemala [ Janik et al , 1992; Goff and McMurtry , 2000]. Investigations of the gas chemistry of springs and test wells in Honduras were part of a major geothermal initiative during the mid‐ to late‐1980s [ Goff et al , 1986, 1987, 1991; Kennedy et al , 1991; Janik et al , 1991). Because neon values were not reported in these investigations, air corrections for helium ratios were carried out in a similar fashion, using He/Ar instead of He/Ne.…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

“…The Central American Volcanic Arc has identifiable geochemical gradients which are controlled to some extent by subduction zone parameters [ Leeman and Carr , 1995; Carr et al , 1990], providing a good location to test how these parameters affect the volatile output. Previous investigations of volatiles in Central America have focused on their effect on eruptive style [ Roggensack et al , 1997], in forecasting volcanic activity [ Menyailov et al , 1986], and in determining their potential for commercial geothermal exploitation [ D'Amore and Mejia , 1999; Giggenbach and Soto , 1992; Nieva et al , 1997; Goff et al , 1991; Janik et al , 1992]. Although global flux data are often extrapolated from individual volcanic systems, relatively little work has been done to investigate the variations in 3 He/ 4 He and CO 2 / 3 He ratios that occur within a single island arc, with the exception of the Antilles [ van Soest et al , 1998] and the Sunda and Banda Arca [ Poorter et al , 1991; Hilton et al , 1992].…”

Section: Introductionmentioning

confidence: 99%

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Regional variations in volatile composition: Isotopic evidence for carbonate recycling in the Central American volcanic arc

Snyder

Poreda

Hunt

et al. 2001

Geochem Geophys Geosyst

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[1] Abstract: Gas data were collected from geothermal production fields, fumaroles, and hot springs in Central America in order to investigate the relation between volatile output and spatial distribution of volcanic systems. The 3 He/ 4 He ratios are 6.5 ± 0.7 R a throughout the region, indicating that helium is predominantly of mantle origin and is largely independent of variations in the characteristics of the arc. Lower ratios produced by radiogenic production within the Chortis Block are restricted to the Berlín geothermal field and the region behind the volcanic front. Ratios of CO 2 / 3 He are inversely related to the distance between the volcanic system and the trench. In the southwestern portion of the arc, where the arc-trench gap is short and the subduction angle is shallow (Miravalles, Costa Rica), decarbonation is enhanced relative to the mantle helium flux resulting in higher CO 2 / 3 He. In the northwest, where the gap is greater and the subduction angle steeper (Ahuachapán, El Salvador), decarbonation decreases relative to the helium flux. While variations in the carbon isotopic signature have traditionally been linked to the composition of the subducted sediments, the Central American data provide evidence that other factors within the convergent plate boundary such as arc-trench gap, crustal thickness, and subduction angle play an important role in controlling the flux of CO 2 from the subducting slab. The Central American Volcanic Arc gases show no apparent contribution of carbon dioxide derived from subducted organic sediments. Shallow crustal processes, including partitioning and isotopic fractionation, account for the minor deviations from direct mixing of mantle and carbonate-derived end-members. Given that the Central American arc system is not unique in terms of the composition of the subducted sediments or the volcanic output, previous interpretations of global volcanic flux in terms of carbonate and sediment output should be reconsidered. Carbon-helium relationships in Central America require that only 0.3-3.3% of the subducted carbon is released in volcanic eruptions, while the rest is presumably reintroduced into the deeper mantle. This is generally an order of magnitude lower than global averages and is limited by the availability flux of mineral-bound water and the temperature of release. The d 13 C and CO 2 / 3 He ratios suggest that even though the amount of carbon that is released from the slab and subducted sediments is relatively low in Central America, it still makes up 86-98% of the total carbon released from arc volcanics.

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Section: Sampling and Analytical Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Regional variations in volatile composition: Isotopic evidence for carbonate recycling in the Central American volcanic arc

Snyder

Poreda

Hunt

et al. 2001

Geochem Geophys Geosyst

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“…Such systems are found in various areas of the world such as the Cordillera of western Canada (Grasby et al. 2000), Platanares in Honduras (Goff et al. 1991), the Balcova field in Turkey (Serpen 2004), the Basin and Range Province of the USA (Blackwell et al.…”

Section: Introductionmentioning

confidence: 99%

What do aqueous geothermometers really tell us?

Ferguson¹,

Grasby²,

Hindle³

2009

Geofluids

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The application of chemical geothermometry to shallow groundwaters or spring discharge assumes that there is minimal mixing or re-equilibration of water as it travels from depth to the surface. In this study, we examine the potential for mixing and re-equilibration by examining heat and fluid flow along crustal-scale faults in tectonic geothermal systems. Numerical modeling results indicate that maximum in situ temperatures could be underpredicted by up to 30% due to mixing of fluids that enter the fault at different depths. This, coupled with the depression of isotherms by downward groundwater flow in the hanging wall, could cause underestimates of maximum circulation depth of greater than 80% in extreme cases. Kinetics does not favor re-equilibration in the shallower portions of faults due to low temperatures and higher fluid velocities. However, in areas of deeper circulation or higher heat flow such reactions are possible.

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“…This indicates that the spring waters are probably older than about 50 years based on tritium-age relations presented in Goff et al (1991). Ixtatlala, whose water type appears to be the most geothermal in character, has an apparent maximum mean residence time of about 400 years.…”

Section: Tritium and Relative Agementioning

confidence: 88%

Geochemistry of summit fumarole vapors and flanking thermal/mineral waters at Popocatepetl Volcano, Mexico

Werner¹,

Goff²,

Janik³

1997

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Popocatepetl Volcano is potentially devastating to populations living in the greater Mexico City area. Systematic monitoring of fumarole gases and flanking thermaVmineral springs began in early 1994 after increased fumarolic and seismic activity were noticed in 1991. These investigations had two major objectives: 1) to determine if changes in magmatic conditions beneath Popocatepetl might be reflected by chemical changes in fumarolic discharges and 2) to determine if thermaVminera1 spring waters in the vicinity of Popocatkpetl are geochemically related to or influenced by the magmatic system. This report summarizes results from these two discrete studies.Chemical and isotopic compositions of gases were monitored by placing alkaline traps containing 4N KOH around the crater and by collecting the trap solutions at near-monthly intervals until the volcano erupted on December 21,1994. Absolute abundances of volatile constituents (ppdday of C1, &tal, F, COz, Hg, and As) show general increases during the June-July 1994 and 0ct.-Dec. 1994 time periods. These increases correlated with increased SO2 output measured by correlation spectrometry (COSPEC). The full range of sulfur isotope compositions measured during this study is 1.5 to 6.4%0; the lower values generally occurred in the 0ct.-Dec. samples. These values are very close to that of mantle sulfur (-O%O). The higher values occurred in samples from the June-July period, suggesting possible incorporation of hydrothermal sulfate or underlying Cretaceous evaporitic rocks (roughly 16 to 19%0) into the magma during that time. Carbon isotope compositions measured on the trap solutions were not as useful because of contamination with atmospheric C02. Bulk chemistry and sulfur isotope variations of the volatiles can be explained by injection of mafic magma into a silicic magma chamber beneath the volcano, ascent of magma in the conduit or chamber, and incorporation of small volumes of altered rocks or older strata into the evolving melts.The flanking thermdmineral waters, which were collected periodically from May 1994 until June 1995, show no apparent geochemical changes with time, indicating that increased volcanic activity did not affect these springs. These fluids are relatively low in Si02, B, Br, Cs, Li, and Rb compared with those from known geothermal systems, indicating that Popocatepetl springs are not derived from a high-temperature reservoir. Chemical geothermometry of the waters and feeble gas emissions suggest equilibration temperatures of 160°C. The waters show chemical equilibrium with carbonate and evaporite minerals (calcite and gypsum), which are known to occur in regional Cretaceous strata. Limited stable isotope data on the waters indicate recharge at elevations considerably lower than Popocat6petl summit, whereas tritium contents indicate that the waters have maximum mean residence times of approximately 1000 years.

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Exploration drilling and reservoir model of the Platanares geothermal system, Honduras, Central America

Cited by 24 publications

References 13 publications

Regional variations in volatile composition: Isotopic evidence for carbonate recycling in the Central American volcanic arc

Regional variations in volatile composition: Isotopic evidence for carbonate recycling in the Central American volcanic arc

What do aqueous geothermometers really tell us?

Geochemistry of summit fumarole vapors and flanking thermal/mineral waters at Popocatepetl Volcano, Mexico

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