Gas Geochemistry Of The Valles Caldera Region, New Mexico And Comparisons With Gases At Yellowstone, Long Valley And Other Geothermal Systems
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Journal Article: Gas Geochemistry Of The Valles Caldera Region, New Mexico And Comparisons With Gases At Yellowstone, Long Valley And Other Geothermal Systems
Abstract
Noncondensible gases from hot springs, fumaroles, and deep wells within the Valles caldera geothermal system (210-300°C) consist of roughly 98.5 mol% CO2, 0.5 mol% H2S, and 1 mol% other components. 3He/4He ratios indicate a deep magmatic source (R/Ra up to 6) whereas Δ13C-CO2 values (-3 to -5‰) do not discriminate between a mantle/magmatic source and a source from subjacent, hydrothermally altered Paleozoic carbonate rocks. Regional gases from sites within a 50-km radius beyond Valles caldera are relatively enriched in CO2 and He, but depleted in H2S compared to Valles gases. Regional gases have R/Ra values <=1.2 due to more interaction with the crust and/or less contribution from the mantle. Carbon sources for regional CO2 are varied. During 1982-1998, repeat analyses of gases from intracaldera sites at Sulphur Springs showed relatively constant CH4, H2, and H2S contents. The only exception was gas from Footbath Spring (1987-1993), which experienced increases in these three components during drilling and testing of scientific wells VC-2a and VC-2b. Present-day Valles gases contain substantially less N2 than fluid inclusion gases trapped in deep, early-stage, post-caldera vein minerals. This suggests that the long-lived Valles hydrothermal system (ca. 1 Myr) has depleted subsurface Paleozoic sedimentary rocks of nitrogen. When compared with gases from many other geothermal systems, Valles caldera gases are relatively enriched in He but depleted in CH4, N2 and Ar. In this respect, Valles gases resemble end-member hydrothermal and magmatic gases discharged at hot spots (Galapagos, Kilauea, and Yellowstone).- Authors
- Fraser E. Goff and Cathy J. Janik
- Published Journal
- Journal of Volcanology and Geothermal Research, 2002
- DOI
- Not Provided
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Citation
Fraser E. Goff,Cathy J. Janik. 2002. Gas Geochemistry Of The Valles Caldera Region, New Mexico And Comparisons With Gases At Yellowstone, Long Valley And Other Geothermal Systems. Journal of Volcanology and Geothermal Research. 116(3-4):299-323.
Related Geothermal Exploration Activities
Activities (20)
- Compound and Elemental Analysis At Fenton Hill HDR Geothermal Area (Goff & Janik, 2002)
- Compound and Elemental Analysis At Fenton Hill HDR Geothermal Area (Janik & Goff, 2002)
- Compound and Elemental Analysis At Jemez Springs Area (Goff & Janik, 2002)
- Compound and Elemental Analysis At Valles Caldera - Redondo Geothermal Area (Janik & Goff, 2002)
- Compound and Elemental Analysis At Valles Caldera - Sulphur Springs Geothermal Area (Janik & Goff, 2002)
- Compound and Elemental Analysis At Yellowstone Region (Goff & Janik, 2002)
- Gas Sampling At Valles Caldera - Sulphur Springs Geothermal Area (Janik & Goff, 2002)
- Isotopic Analysis At Jemez Springs Area (Goff & Janik, 2002)
- Isotopic Analysis At Valles Caldera - Redondo Geothermal Area (Janik & Goff, 2002)
- Isotopic Analysis At Yellowstone Region (Goff & Janik, 2002)
- Isotopic Analysis- Fluid At Fenton Hill HDR Geothermal Area (Goff & Janik, 2002)
- Isotopic Analysis- Fluid At Valles Caldera - Sulphur Springs Geothermal Area (Janik & Goff, 2002)
- Isotopic Analysis- Gas At Long Valley Caldera Geothermal Area (Welhan, Et Al., 1988)
- Surface Gas Sampling At Fenton Hill HDR Geothermal Area (Goff & Janik, 2002)
- Surface Gas Sampling At Jemez Springs Area (Goff & Janik, 2002)
- Surface Gas Sampling At Valles Caldera - Redondo Area (Goff & Janik, 2002)
- Surface Gas Sampling At Valles Caldera - Sulphur Springs Area (Goff & Janik, 2002)
- Surface Gas Sampling At Yellowstone Region (Goff & Janik, 2002)
- Water-Gas Samples At Valles Caldera - Redondo Geothermal Area (Janik & Goff, 2002)
- Water-Gas Sampling At Fenton Hill HDR Geothermal Area (Janik & Goff, 2002)
Areas (8)
- Fenton Hill HDR Geothermal Area
- Jemez Springs Area
- Valles Caldera - Redondo Geothermal Area
- Valles Caldera - Sulphur Springs Geothermal Area
- Yellowstone Caldera Geothermal Region
- Long Valley Caldera Geothermal Area
- Valles Caldera - Redondo Area
- Valles Caldera - Sulphur Springs Area
Regions (0)