Pb loss in u pb dating
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This provides further information about sediment input pathways to sedimentary basins and, when combined with detrital zircon analysis, provides a powerful tool to identify the provenance of sediments.As with other isochron methods, the U-Pb isochron method has been questioned in the open literature, because often an excellent line of best fit between ratios obtained from a set of good cogenetic samples gives a resultant “isochron” and yields a derived “age” that has no distinct geological meaning.
Chemostrat employ a laser ablation system coupled with an ICPMS to analyse and date zircon crystals.In our efforts to U-Pb date zircons from the late Eocene Caetano caldera by SIMS (SHRIMP-RG: sensitive high resolution ion microprobe, reverse geometry), some grains yielded anomalously young U-Pb ages that implicated Pb-loss and motivated us to investigate with a comparative CA and non-CA dating study.We present CA and non-CA U ages and trace elements determined by SHRIMP-RG for zircons from three Caetano samples (Caetano Tuff, Redrock Canyon porphyry, and a silicic ring-fracture intrusion) and for R33 and TEMORA-2 reference zircons.U-Pb ages do not correlate with U (~ 100–800 ppm), Th (~ 50–300 ppm) or any other measured zircon trace elements (Y, Hf, REE), and CA and non-CA Caetano zircons define identical trace element ranges.No statistically significant difference in U-Pb age is observed for CA versus non-CA R33 or TEMORA-2 zircons.At present, Chemostrat can determine U-Pb ages for zircon and apatite crystals.
Zircon is a robust mineral and so the crystals preserve the age at which they formed or underwent high grade metamorphism.This makes the task of creationists building their model for the geological record much easier, since claims of U-Th-Pb radiometric “dating” having “proven” the claimed great antiquity of the earth, its strata and fossils can be safely side-stepped.This paper was originally published in the Proceedings of the Third International Conference on Creationism, pp.► Titanite grains can remain closed to Pb loss at 750 °C and 3 GPa.► Phase transformations in quartzofeldspathic rocks can be inhibited at these conditions.By determining the U-Pb isotopic composition of a zircon crystal, the age of the crystal can be calculated by utilising a ‘concordia diagram’.