U pb dating minerals

Previous determinations of the cooling rates of equilibrated (metamorphosed) chondrites of ca. An increase in precision of the 207Pb/206Pb dates to ±0.1-0.3 Ma due to use of the Pb isochron dating of multiple pyroxene and Ca-phosphate fractions from the plutonic angrite NWA 4590 yielded the ages of 4558.69±0.28 Ma and 4558.14±0.07 Ma, respectively, and cooling rate of ca.500±300°C/Ma (the uncertainty of the cooling rates is mainly controlled by uncertainty in the closure temperatures of Pb diffusion).Precise and accurate U–Pb LA–ICPMS dating of many U-bearing accessory minerals (e.g.-corrected age channels can be calculated for user-specified initial Pb ratio(s).All other conventional common Pb correction methods (e.g.Madagascar apatite, OLT1 titanite and R10 rutile were used as primary standards and were corrected for variable common Pb using the new Vizual Age_Ucom Pbine DRS.The secondary Durango (31.44 ± 0.18 Ma) apatite standard yielded a U–Pb TW concordia intercept age of 31.97 ± 0.59 Ma (MSWD = 1.09; primary standard corrected by the Pb-method).apatite, allanite, titanite and rutile) is often compromised by common Pb.LA–ICPMS dating of these U-bearing accessory phases typically requires a matrix-matched standard, and data reduction is often complicated by incorporation of common Pb not only into the unknowns but also particularly into the reference material.Vizual Age_Ucom Pbine first applies a common Pb correction to the user-selected age standard integrations and then fits session-wide “model” U–Pb fractionation curves to the time-resolved U–Pb standard data.This downhole fractionation model is applied to the unknowns and sample-standard bracketing (using a user-specified interpolation method) is used to calculate final isotopic ratios and ages.


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