Even a claimed near-concordant U-Pb ‘age’ of 862 Ma on one uraninite grain is identical to a false Pb-Pb isochron “age,” but neither can be connected to any geological event.
The other problem is that uranium is particularly susceptible to weathering.
Now since all rocks are somewhat porous, and since we are pretty much obliged to date rocks from near the surface, it's hard to find instances in which uranium has not been lost.
Yet U-Th-Pb isotopic studies of the uranium ore, host rocks and soils have produced an array of false “isochrons” that yield “ages” which are geologically meaningless.
Even a claimed near-concordant U- Pb “age” of 862 Ma (million years) on one uraninite grain is identical to a false Pb-Pb isochron “age” but neither can be connected to any geological event.
The open system behaviour of the U-Th-Pb system is clearly the norm, as is the resultant mixing of radiogenic Pb with “common” or background Pb, even in soils in the surrounding region, apparently even up to 17 km away!
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.
The reader will find this article much easier to grasp if s/he has already mastered the material in the articles on K-Ar dating, Ar-Ar dating, and Rb-Sr dating.
Pb (lead-204), which is neither unstable nor radiogenic.
We can always try U-Pb dating using the isochron method, but this often doesn't work: the compositions of the minerals involved, when plotted on an isochron diagram, fail to lie on a straight line. First of all, the straight-line property of the isochron diagram is destroyed when the isotopes involved get shuffled between minerals.
Now lead and uranium are particularly susceptible to such shuffling in the event of even mild metamorphism.
497–504 (1994) and is reproduced here with the permission of the Creation Science Fellowship of Pittsburgh.