Pb loss in u pb dating
Stacey and Kramers, 1975; section 5.4.3), rather then by direct analysis of the whole-rock sample. Ahrens argued against lead loss from monazites by leaching, since he (erroneously ?
Together they provide two separate decay schemes to determine ages of crystallisation of minerals ranging from about 10 million years, up to and beyond the age of the earth at 4.55 billion years (2) (3) Harris claims that U-Pb data indicates a young earth.
In the laboratory, rock samples are crushed and the zircon grains are separated from the other minerals by heavy liquid and other mineral separation techniques.
After being mounted, the crystals can be analyzed using an instrument such as a SHRIMP (Sensitive High mass Resolution Ion Micro Probe) which focuses a very narrow ion beam onto the grains so that mass spectrometers can measure the ratios of the isotopes vaporized from the targeted spot.
Two-dimensional kernel density estimation of the combined U–Pb data from each map define clear discordia mixing lines between the rim- and core-age components, and also show Pb loss and common Pb vectors.
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.
The mapping-experiment duration for individual zircons was as fast as 10 minutes (Agilent 7900 setup).
91500 zircon was employed as the primary reference material, and secondary-standard data (Temora, Plešovice, WRS-1348, FC-1, Fish Canyon, Tardree) typically reproduce within 1% of their published crystallization ages.