Elsevier

Chemical Geology

Volume 112, Issues 1–2, 25 January 1994, Pages 179-191
Chemical Geology

Research paper
(Uranium + thorium)/helium dating of apatite: experience with samples from different geochemical environments

https://doi.org/10.1016/0009-2541(94)90113-9Get rights and content

Abstract

U-He dating, which during its history has been very problematic, might find special application in the field of hydrothermal mineralizations where other methods generally fail. The mineral apatite is a potential candidate for this method. In order to shed light on various aspects of apatite dating by the (U + Th)/He method, two samples each from different geochemical environments (plutonic, pneumatolytic and hydrothermal) were probed. Isotope dilution techniques were used for concentration analyses from which 4He model dates, also called “helium indices” after N.B. Keevil, were calculated. 4He diffusion measurements were carried out for comparison of the 4He retentivities between the samples. Comparisons of the apatite He indices with plausible reference ages of the sampling locations in combination with results obtained from diffusion experiments show that the (U + Th)/He dating method applied to apatite yields an age of cooling rather than an emplacement age. The calculated closure temperatures are similar to those obtained by the fission-track method (∼ 100°C). Our results suggest that the high-temperature apatites (plutonic and pneumatolytic) may be more suitable for He dating than hydrothermal apatite. Important criteria for the dating of apatite by (U + Th)/He are the presence of moderate radionuclide concentrations (tens of ppm) and a minimum abundance of inclusions.

References (39)

  • H.J. Lippolt et al.

    4He diffusion in 40Arretentive minerals

    Geochim. Cosmochim. Acta

    (1988)
  • E.B. Watson et al.

    Diffusion of Sm, Sr and Pb in fluorapatite

    Geochim. Cosmochim. Acta

    (1985)
  • P.K. Zeitler et al.

    U-Th-He dating of apatite: A potential thermochronometer

    Geochim. Cosmochim. Acta

    (1987)
  • H. Ahrendt et al.

    Kalium-Argon Altersbestimmungen an schwach metamorphen Gesteinen des Rheinischen Schiefergebirges

    Z. Dtsch. Geol. Ges.

    (1978)
  • R. Bähr et al.

    The reliability of uranium-thorium/helium ages of kidney-type hematite

    Terra Cognita

    (1987)
  • G. Binder

    Die Diadochie von Fluor, Chlor und Hydroxyl in Apatiten aus magmatischen und metamorphen Gesteinen

  • W. Boschmann Käthler

    Uran und Helium in Erzmineralien und die Frage ihrer Datierbarkeit

  • W. Boschmann Käthler et al.

    Eignungsprüfung von Erzmineralien für (U + Th)/He-Datierungen

  • M.H. Dodson

    Closure temperature in geochronological and petrological systems

    Contrib. Mineral. Petrol.

    (1973)
  • N. Fechtig et al.

    The diffusion of argon in potassium bearing solids

  • F. Felix et al.

    Rare gas releases from solids with special attention to nuclear fuel materials

  • G. Frenzel

    Die Erzparagenese des Katzenbuckels im Odenwald

    Heidelberger Beitr. Mineral. Petrol.

    (1953)
  • L. Fruth

    Mineralfundstellen, Vol. 1. Tirol-Salzburg-Südtirol

  • E.K. Gerling

    Diffusionswärme des Heliums als Kriterium für die Brauchbarkeit von Mineralien für Altersbestimmungen nach der Heliummethode

    C.R. Acad. Sci. U.R.S.S.

    (1939)
  • M. Hanel

    Einteilung und geologische Entwicklung der Metamorphite des zentralen Groβen Kaukasus aufgrund neuerer Literatur und neuer Daten

  • T.M. Harrison et al.

    40Ar39Ar results for alkali feldspars containing diffusion domains with differing activation energy

    Geochim. Cosmochim. Acta

    (1991)
  • P.M. Hurley

    The helium age method and the distribution and migration of helium in rocks

  • N.B. Keevil

    Terminology in age work

    Am. J. Sci.

    (1941)
  • N.B. Keevil

    The distribution of helium in rocks, V

    Am. J. Sci.

    (1943)
  • Cited by (0)

    α

    Present address: Institut für Radiologie, D-91054 Erlangen, Germany.

    β

    Present address: Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) m.b.H., D-50667 Köln, Germany.

    View full text