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Title: A systematic regional trend in helium isotopes across the northernbasin and range province, Western North America

Abstract

An extensive study of helium isotopes in fluids collectedfrom surface springs, fumaroles and wells across the northern Basin andRange Province reveals a systematic trend of decreasing 3He/4He ratiosfrom west to east. The western margin of the Basin and Range ischaracterized by mantle-like ratios (6-8 Ra) associated with active orrecently 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. Theregional trend is consistent with extensive mantle melting concentratedalong the western margin and is coincident with an east-to-west increasein the magnitude of northwest strain. The increase in shear strainenhances crustal permeability resulting in high vertical fluid flow ratesthat preserve the high helium isotope ratios at the surface. Superimposedon the regional trend are "helium spikes," local anomalies in the heliumisotope composition. These "spikes" reflect either local zones of mantlemelting or locally enhanced crustal permeability. In the case of theDixie Valley hydrothermal system, it appears to be a combination ofboth.

Authors:
;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE. Assistant Secretary for Energy Efficiency and Rene.Solar and Renewable Resource Technologies
OSTI Identifier:
919013
Report Number(s):
LBNL-61338
R&D Project: G32615; BnR: EB4005010; TRN: US200822%%97
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Conference
Resource Relation:
Conference: Annual Meeting of the Geothermal ResourcesCouncil, San Diego, California, 10-13 September2006
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; FLUID FLOW; FUMAROLES; GEOTHERMAL RESOURCES; HELIUM; HELIUM ISOTOPES; HYDROTHERMAL SYSTEMS; LONG VALLEY; MAGMA SYSTEMS; MELTING; PERMEABILITY; SHEAR; STRAINS; VALLEYS; Helium isotopes Basin and Range fault hosted permeabilityexploration Dixie Valley

Citation Formats

Kennedy, B. Mack, and van Soest, Matthijs C. A systematic regional trend in helium isotopes across the northernbasin and range province, Western North America. United States: N. p., 2006. Web.
Kennedy, B. Mack, & van Soest, Matthijs C. A systematic regional trend in helium isotopes across the northernbasin and range province, Western North America. United States.
Kennedy, B. Mack, and van Soest, Matthijs C. Mon . "A systematic regional trend in helium isotopes across the northernbasin and range province, Western North America". United States. doi:. https://www.osti.gov/servlets/purl/919013.
@article{osti_919013,
title = {A systematic regional trend in helium isotopes across the northernbasin and range province, Western North America},
author = {Kennedy, B. Mack and van Soest, Matthijs C.},
abstractNote = {An extensive study of helium isotopes in fluids collectedfrom surface springs, fumaroles and wells across the northern Basin andRange Province reveals a systematic trend of decreasing 3He/4He ratiosfrom west to east. The western margin of the Basin and Range ischaracterized by mantle-like ratios (6-8 Ra) associated with active orrecently 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. Theregional trend is consistent with extensive mantle melting concentratedalong the western margin and is coincident with an east-to-west increasein the magnitude of northwest strain. The increase in shear strainenhances crustal permeability resulting in high vertical fluid flow ratesthat preserve the high helium isotope ratios at the surface. Superimposedon the regional trend are "helium spikes," local anomalies in the heliumisotope composition. These "spikes" reflect either local zones of mantlemelting or locally enhanced crustal permeability. In the case of theDixie Valley hydrothermal system, it appears to be a combination ofboth.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2006},
month = {Mon May 01 00:00:00 EDT 2006}
}

Conference:
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