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| Titel |
40Ar/36Ar geochronology on a quadrupole mass spectrometer: Where are we going? |
| VerfasserIn |
B. Schneider, J. R. Wijbrans, K. F. Kuiper, C. R. Fenton, A. J. Williams |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029312
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| Zusammenfassung |
| 40Ar/39Ar analysis has passed many milestones since its first application (Wänke & König,
1959). From the early all-glass Reynolds-type vacuum system to today’s high quality,
bakeable all-metal piping and valve systems, the evolution of ultra high vacuum systems has
been considerable. Extraction systems have faced similar changes over time. Early furnaces
made partially of glass were later replaced by full metal constructs containing a high
temperature resistant molybdenum alloy tube and heating mechanism, sometimes
contained within an insulating secondary vacuum chamber. Laser extraction techniques
further refined the approach allowing very small samples or sample parts to be
analyzed.
The principal type of mass spectrometer used for 40Ar/36Ar geochronology is the
magnetic sector instrument, which has the resolution and sensitivity necessary for measuring
argon isotopes and achieving high precision over a large age range. We present
40Ar/39Ar data from basalt samples collected from a number of different locations,
all obtained using the Hiden HAL Series 1000 quadrupole mass spectrometer at
Vrije University, Amsterdam. We show that quadrupole technology is not only a
viable option in K-Ar geochronology (Rouchon et al., 2008) but also in 40Ar/39Ar
geochronology. The data was obtained from groundmass hand-picked from 200-500 um size
fractions. Sample amounts of 200 to 500 mg were used for incremental heating
experiments. The quality of the data is demonstrated by convergence of plateau and
isochron ages, replicate analyses and by comparison to results of independent studies.
Sample ages range from 40 ka to 400 ka, demonstrating the potential of quadrupole
instruments for dating even very young rocks using the 40Ar/39Ar incremental heating
technique.
Rouchon, V., Lefevre, J.-C., Quidelleur, X., Guerin, G., Gillot, P.-Y. (2008):
Nonspiked 40Ar and 36Ar quantification using a quadrupole mass spectrometer: A
potential for K-Ar geochronology. International Journal of Mass Spectrometry 270,
52-61.
Wänke H., König H. (1959): Eine neue Methode zur Kalium-Argon-Altersbestimmung
und ihre Anwendung auf Steinmeteorite. Z. Naturforschung, 14a, 860 – 866. |
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