U pb dating minerals
Among them is the presence of non-radiogenic Pb of unknown composition, often referred to as common or initial Pb.
There is also primordial Pb that the earth acquired when it formed, its isotopic composition determined as that of troilite in the Canyon Diablo iron meteorite.
The U–Pb age profiles on single apatite grains presented here are characteristic of Pb loss by volume diffusion with core–rim age differences of up to 300 Ma.
These data explain the scatter and poor precision of earlier U–Pb apatite age determinations on Akilia apatite.
The key feature of the method is that it can correct for methods, and the approach can be applied to raw data files from all widely used modern multi-collector and single-collector ICPMS instruments.
Zircon does incorporate initial Pb when it crystallizes. It cannot be proven that the Pb in apparently cogenetic U- or Th-free minerals is only initial Pb, and that it is identical to the initial Pb in the mineral being dated.
Nor can the measured Pb isotope ratios be used to somehow decide what proportions of them are the initial Pb without recourse to unprovable assumptions about the mineral or rock’s history or their interpreted U-Th-Pb ages within an assumed deep time history.
Mc Clure Mountain (523.51 ± 1.47 Ma) yielded a U–Pb TW concordia intercept age of 524.5 ± 3.7 Ma (MSWD = 0.72) while the Fish Canyon Tuff (28.201 ± 0.046 Ma) and Khan (522.2 ± 2.2 Ma) titanite standards yielded U–Pb TW concordia intercept ages of 28.78 ± 0.41 Ma (MSWD = 1.4) and 520.9 ± 3.9 Ma (MSWD = 4.2) respectively.
The suitability of the -corrected TW concordia age of 448.6 ± 4.5 Ma (MSWD = 1.4) on a c.
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Other LA–ICPMS dating applications include U–Pb apatite dating as a rapid method for determining the age of mafic intrusions, U–Pb titanite and apatite dating of ash fall tuffs, determining temperature–time histories using multiple U–Pb thermochronometers and improving concordance in LA–ICPMS primary zircon standard datasets by analysing young, common Pb-bearing primary zircon standards that have not accumulated significant radiation damage.