A systematic regional trend in helium isotopes across the Northern Basin and Range Province, Western North America

B. Mack Kennedy, Matthijs C. Van Soest

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

An extensive study of helium isotopes in fluids collected from surface springs, fumaroles and wells across the northern Basin and Range Province reveals a systematic trend of decreasing 3He/4He ratios from west to east. The western margin of the Basin and Range is characterized by mantle-like ratios (6-8 Ra) associated with active or recently active crustal magma systems (e.g. Coso, Long Valley, Steamboat, and the Cascade volcanic complex). Moving towards the east, the ratios decline systematically to a background value of ∼0.1 Ra. The regional trend is consistent with extensive mantle melting concentrated along the western margin and is coincident with an east-to-west increase in the magnitude of northwest strain. The increase in shear strain enhances crustal permeability resulting in high vertical fluid flow rates that preserve the high helium isotope ratios at the surface. Superimposed on the regional trend are "helium spikes", local anomalies in the helium isotope composition. These "spikes" reflect either local zones of mantle melting or locally enhanced crustal permeability. In the case of the Dixie Valley hydrothermal system, it appears to be a combination of both.

Original languageEnglish (US)
Title of host publicationGeothermal Resources Council Transactions - GRC 2006 Annual Meeting
Subtitle of host publicationGeothermal Resources-Securing Our Energy Future
Pages429-433
Number of pages5
StatePublished - Dec 1 2006
EventGRC 2006 Annual Meeting: Geothermal Resources-Securing Our Energy Future - San Diego, CA, United States
Duration: Sep 10 2006Sep 13 2006

Publication series

NameTransactions - Geothermal Resources Council
Volume30 I
ISSN (Print)0193-5933

Other

OtherGRC 2006 Annual Meeting: Geothermal Resources-Securing Our Energy Future
CountryUnited States
CitySan Diego, CA
Period9/10/069/13/06

Keywords

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

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Geophysics

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  • Cite this

    Kennedy, B. M., & Van Soest, M. C. (2006). A systematic regional trend in helium isotopes across the Northern Basin and Range Province, Western North America. In Geothermal Resources Council Transactions - GRC 2006 Annual Meeting: Geothermal Resources-Securing Our Energy Future (pp. 429-433). (Transactions - Geothermal Resources Council; Vol. 30 I).