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Mantle helium in the groundwater of the Mirror Lake Basin, New Hampshire, USA, 1994

By: , and 

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Abstract

Helium isotope analyses of ground waters from the Mirror Lake drainage basin in central New Hampshire (USA) show helium in excess of air-saturated water by up to 200x. The freon ages of these waters are younger than 50 years, consistent with the local hydrology. This excess helium has an isotope ratio of ^3He/^4He = 1.65 ± 0.10 x 10^(-6). It is shown that this component cannot be the result of cosmogenic production or mixing with young water containing ^3He from the decay of (bomb) tritium. Measurements of the helium isotope ratio of local rocks indicate that they cannot be the source of this excess component. This strongly suggests that the excess helium component is the result of the addition of some external source of mantle helium. The generally accepted view suggests that mantle helium in continental environments is the result of active volcanism and extensional tectonics. The latest episodes of volcanism in this region of New England are related to the New England hot spot track (95-190 Myr) and the closure of the Iapetus (> 300 Myr). Thus, either the timescale for helium transport through the crust is of the order of 100's of Myr or the signature of mantle helium can be preserved in (e.g.) fluid inclusions for significant periods of time. 

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Mantle helium in the groundwater of the Mirror Lake Basin, New Hampshire, USA, 1994
Year Published 1994
Language English
Publisher Terra Scientific
Publisher location Tokyo, Japan
Contributing office(s) Toxic Substances Hydrology Program, National Research Program - Eastern Branch
Description 14 p.
Larger Work Type Book
Larger Work Title Noble gas geochemistry and cosmoschemistry
First page 279
Last page 292