Pb pb dating method
The Koongarra uranium deposit occurs in a metamorphic terrain that has an Archaean basement consisting of domes of granitoids and granitic gneisses (the Nanambu Complex), the nearest outcrop being 5 km to the north (see Figure 1).Some of the lowermost overlying Lower Proterozoic metasediments were accreted to these domes during amphibolite grade regional metamorphism (estimated to represent conditions of 5-8 kb and 550-630Â¡ C) at 1800- 1870 Ma (million years ago, according to conventional evolutionary dating).In the conclusion to a recent paper exposing shortcomings and criticising the validity of the popular rubidium-strontium (Rb-Sr) isochron method, Zheng wrote: ‘…some of the basic assumptions of the conventional Rb-Sr isochron method have to be modified and an observed isochron does not certainly define a valid age information for a geological system, even if a goodness of fit of the experimental data points is obtained in plotting Sr ratios, even an excellent line of best fit between ratios obtained from good cogenetic samples, and yet the resultant isochron and derived ‘age’ have no distinct geological meaning.Your access to the NCBI website at gov has been temporarily blocked due to a possible misuse/abuse situation involving your site.
But the method does not always give the ‘expected’ results, leading to fundamental questions about its validity.
A thick sequence of essentially flat-lying sandstones (the Middle Proterozoic Kombolgie Formation) was then deposited unconformably on the Archaean-Lower Proterozoic basement and metasediments.
At Koongarra subsequent reverse faulting has juxtaposed the lower Cahill Formation schists and Kombolgie Formation sandstone.
Because no geologically meaningful results can be interpreted from the U-Th-Pb data at Koongarra (three uraninite grains even yield a Pb ‘age’ of 0 Ma), serious questions must be asked about the validity of the fundamental/foundational basis of the U-Th-Pb ‘dating’ method.
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 justifiably ignored.