3H-3He dating: A case for mixing of young and old groundwaters

I. L. Kamensky, I. V. Tokarev, I. N. Tolstikhin

    Research output: Contribution to journalArticlepeer-review

    15 Scopus citations

    Abstract

    3He 4He and 20Ne 4He ratios were measured in shallow underground waters (opened by water-supplying wells) of the Large Vud-Javr intramountain artesian basin in the Khibiny alkaline massif, the Kola Peninsula. The ratios vary from 1.321 × 10-6 to 2.065 × 10-6 and from 1.412 to 2.941, respectively, and a well-defined correlation is observed between them. Both these ratios in aquifers are known to be time-dependent, the former increases with time due to accumulation of 3He, produced in waters by 3H β-decay; the latter decreases due to migration of helium from water-bearing rocks into the waters. The correlation is interpreted as a result of the mixing of two different types of waters. The approximation line enables us to estimate the isotopic ratios for the endmembers participating in the mixing and the mean residence time (τ) of tritigenic helium-3 in the water: 1. (1) 3He 4He = 3.655 × 10-6, 20Ne 4He = 4.03, and taking into consideration 3H concentrations in the well waters, 3H = 31.1 TU (practically the same for all samples), τ = 15.8 ± 1.5 years for the young water; 2. (2) 3He 4He = 0.20 × 10-6, 20Ne 4He = 0.18 and T = 0.11 Ma for the old one, the contribution of the old water being less than 10%. In one well a considerable contribution of modern-day meteoric water, about 16%, is observed.

    Translated title of the contribution3H-3He датирование: случай смешения молодых и древних вод
    Original languageEnglish
    Pages (from-to)2895-2899
    Number of pages5
    JournalGeochimica et Cosmochimica Acta
    Volume55
    Issue number10
    DOIs
    StatePublished - 1991

    Scopus subject areas

    • Geochemistry and Petrology

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