Regional and local trends in helium isotopes, Basin and Range province, Western North America: Evidence for deep permeable pathways

B. Mack Kennedy, Matthijs Van Soest

Research output: Contribution to journalConference article

3 Citations (Scopus)

Abstract

Fluids from the western margin of the Basin and Range have helium isotope ratios as high as ∼6-7 Ra, indicating a strong mantle melt influence and consistent with recent and current volcanic activity. Moving away from these areas, helium isotope ratios decrease rapidly to 'background' values of around 0.6 Ra, and then gradually decrease toward the east to low values of ∼0.1 Ra at the eastern margin of the Basin and Range. Superimposed on this general regional trend are isolated features with elevated helium isotope ratios (0.8-2.1 Ra) compared to the local background. Spring geochemistry and local geology indicate that these "He-spikes" are not related to current or recent magmatic activity, suggesting that the spikes may reflect either localized zones of deep mantle melting or deep permeable pathways (faults) with high vertical fluid flow rates. A detailed study of one of the He-spikes (Dixie Valley and the Stillwater Range Front Fault system), indicates that features with high 3He/ 4He ratios are confined to the range front normal faults characteristic of the extensional regime in the Basin and Range, suggesting that these faults are deep permeable pathways. However, not all range front fault systems transmit fluids with a mantle signature, implying that not all have deep permeable pathways.

Original languageEnglish (US)
Pages (from-to)263-267
Number of pages5
JournalTransactions - Geothermal Resources Council
Volume29
StatePublished - Dec 1 2005
Externally publishedYes
EventGeothermal Resources Council 2005 Annual Meeting - Reno, NV, United States
Duration: Sep 25 2005Sep 28 2005

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helium isotope
helium isotopes
isotope ratios
spikes
Isotopes
Helium
Earth mantle
trends
margins
mantle
basin
Geochemistry
Fluids
fluids
geochemistry
Geology
geology
fluid flow
valleys
fluid

Keywords

  • Basin and Range
  • Dixie Valley
  • Exploration
  • Fault hosted permeability
  • Helium isotopes

ASJC Scopus subject areas

  • Geology
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

Cite this

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title = "Regional and local trends in helium isotopes, Basin and Range province, Western North America: Evidence for deep permeable pathways",
abstract = "Fluids from the western margin of the Basin and Range have helium isotope ratios as high as ∼6-7 Ra, indicating a strong mantle melt influence and consistent with recent and current volcanic activity. Moving away from these areas, helium isotope ratios decrease rapidly to 'background' values of around 0.6 Ra, and then gradually decrease toward the east to low values of ∼0.1 Ra at the eastern margin of the Basin and Range. Superimposed on this general regional trend are isolated features with elevated helium isotope ratios (0.8-2.1 Ra) compared to the local background. Spring geochemistry and local geology indicate that these {"}He-spikes{"} are not related to current or recent magmatic activity, suggesting that the spikes may reflect either localized zones of deep mantle melting or deep permeable pathways (faults) with high vertical fluid flow rates. A detailed study of one of the He-spikes (Dixie Valley and the Stillwater Range Front Fault system), indicates that features with high 3He/ 4He ratios are confined to the range front normal faults characteristic of the extensional regime in the Basin and Range, suggesting that these faults are deep permeable pathways. However, not all range front fault systems transmit fluids with a mantle signature, implying that not all have deep permeable pathways.",
keywords = "Basin and Range, Dixie Valley, Exploration, Fault hosted permeability, Helium isotopes",
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T1 - Regional and local trends in helium isotopes, Basin and Range province, Western North America

T2 - Evidence for deep permeable pathways

AU - Kennedy, B. Mack

AU - Van Soest, Matthijs

PY - 2005/12/1

Y1 - 2005/12/1

N2 - Fluids from the western margin of the Basin and Range have helium isotope ratios as high as ∼6-7 Ra, indicating a strong mantle melt influence and consistent with recent and current volcanic activity. Moving away from these areas, helium isotope ratios decrease rapidly to 'background' values of around 0.6 Ra, and then gradually decrease toward the east to low values of ∼0.1 Ra at the eastern margin of the Basin and Range. Superimposed on this general regional trend are isolated features with elevated helium isotope ratios (0.8-2.1 Ra) compared to the local background. Spring geochemistry and local geology indicate that these "He-spikes" are not related to current or recent magmatic activity, suggesting that the spikes may reflect either localized zones of deep mantle melting or deep permeable pathways (faults) with high vertical fluid flow rates. A detailed study of one of the He-spikes (Dixie Valley and the Stillwater Range Front Fault system), indicates that features with high 3He/ 4He ratios are confined to the range front normal faults characteristic of the extensional regime in the Basin and Range, suggesting that these faults are deep permeable pathways. However, not all range front fault systems transmit fluids with a mantle signature, implying that not all have deep permeable pathways.

AB - Fluids from the western margin of the Basin and Range have helium isotope ratios as high as ∼6-7 Ra, indicating a strong mantle melt influence and consistent with recent and current volcanic activity. Moving away from these areas, helium isotope ratios decrease rapidly to 'background' values of around 0.6 Ra, and then gradually decrease toward the east to low values of ∼0.1 Ra at the eastern margin of the Basin and Range. Superimposed on this general regional trend are isolated features with elevated helium isotope ratios (0.8-2.1 Ra) compared to the local background. Spring geochemistry and local geology indicate that these "He-spikes" are not related to current or recent magmatic activity, suggesting that the spikes may reflect either localized zones of deep mantle melting or deep permeable pathways (faults) with high vertical fluid flow rates. A detailed study of one of the He-spikes (Dixie Valley and the Stillwater Range Front Fault system), indicates that features with high 3He/ 4He ratios are confined to the range front normal faults characteristic of the extensional regime in the Basin and Range, suggesting that these faults are deep permeable pathways. However, not all range front fault systems transmit fluids with a mantle signature, implying that not all have deep permeable pathways.

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