Gas Geochemistry Of The Valles Caldera Region, New Mexico And Comparisons With Gases At Yellowstone, Long Valley And Other Geothermal Systems

Jump to: navigation, search


OpenEI Reference LibraryAdd to library

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
Check for DOI availability: http://crossref.org


Online 
Internet link for Gas Geochemistry Of The Valles Caldera Region, New Mexico And Comparisons With Gases At Yellowstone, Long Valley And Other Geothermal Systems

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)


Areas (8)
  1. Fenton Hill HDR Geothermal Area

  2. Jemez Springs Area

  3. Valles Caldera - Redondo Geothermal Area

  4. Valles Caldera - Sulphur Springs Geothermal Area

  5. Yellowstone Caldera Geothermal Region

  6. Long Valley Caldera Geothermal Area

  7. Valles Caldera - Redondo Area

  8. Valles Caldera - Sulphur Springs Area
Regions (0)