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| Titel |
Uranium-lead dating of perovskite from the Afrikanda plutonic complex (Kola Peninsula, Russia) using LA-ICP-MS. |
| VerfasserIn |
E. Reguir, A. Camacho, P. Yang, A. R. Chakhmouradian, N. M. Halden |
| 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 |
250030305
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| Zusammenfassung |
| Perovskite (CaTiO3) is a common early crystallizing accessory phase in a variety of alkaline
rocks, and has been shown to contain enough U and Th for U-Pb dating. U and Pb analysis of
perovskite has been primarily carried out using the SHRIMP or ID-TIMS techniques, and
the resulting U-Pb dates commonly yield the emplacement age of the host rock.
To our knowledge, only one U-Pb study of perovskite has been done using the
LA-ICP-MS (Cox and Wilton, 2006). Some of the advantages of this method over
the SHRIMP and ID-TIMS techniques include greater speed and lower cost of
analysis.
In this work, the U-Pb ages of perovskite from the Afrikanda plutonic complex (Russia)
were obtained in situ using the LA-ICP-MS. The measured 238U/206Pb and 207Pb/206Pb
ratios were corrected for time-dependent mass-bias using the well-calibrated zircon standard
GJ-1 (608.5 ± 0.4 Ma; Jackson et al., 2004). On a Tera-Wasserburg diagram (Tera and
Wasserburg, 1972) the analyses of perovskite from two magmatic phases (clinopyroxenite
and carbonatite) plot in separate clusters. Although the variations in the 238U/206Pb
and 207Pb/206Pb ratios within each group are small, there is enough dispersion
between the two clusters to obtain a reasonably precise age of 375 ± 13 Ma (2Ï;
MSWD = 0.23), which strongly suggests that the carbonatitic rocks are broadly
coeval with the clinopyroxenite. The only other isotopic study on the Afrikanda
Complex was done on a clinopyroxenite using the Rb-Sr method and yielded a whole
rock-mineral (perovskite, biotite, augite and apatite) isochron age of 364.0 ± 3.1 Ma (2Ï;
MSWD = 0.72). This age is within error of our U-Pb date, which demonstrates that
LA-ICP-MS-based U-Pb dating of perovskite can serve as a reliable geochronological
tool.
References
Cox, R.A. and Wilton, D.H.C. (2006) U-Pb dating of perovskite by LA-ICP-MS: An
example from the Oka carbonatite, Quebec, Canada. Chem. Geol., 235, 21–32.
Jackson, S.E., Pearson, N.J., Griffin, W.L. and Belousova, E.A. (2004) The application of
laser ablation-inductively coupled plasma-mass spectrometry to in situ U-Pb zircon
geochronology. Chem. Geol.,211, 47-69.
Kramm, U., Kogarko, L.N., Kononova, V.A. and Vartiainen, H. (1993) The Kola alkaline
province of the CIS and Finland. Lithos, 30, 33-44.
Tera, F. and Wasserburg, G.J. (1972) U-Th-Pb systematics in three Apollo 14 basalts
and the problem of initial Pb in lunar rocks. Earth Planet. Sci. Lett., 14, 281-304. |
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