This does not include dates from minerals that are thought to yield bad dates, or from igneous bodies with wide biostrategraphic ranges, where many dates are acceptable. So this argon that is being produced will leave some rocks and enter others. The fact that they are squashed indicates that part of the decay process began before the material was compressed, so the polonium had to be present before compression. If one is dealing with minerals that exclude parent or daughter, then one cannot get an isochron at all. This is called the biostratigraphic limit of the flow.
More U is found in carbonate rocks, while Th has a very strong preference for granites in comparison.
Research illuminates inaccuracies in radiocarbon dating
But lead is a metal, and to me it looks more likely that lead would concentrate along with the iron. As proof of the unreliability of the radiometric methods consider the fact that in nearly every case dates from recent lava flows have come back excessively large. In addition, the magma chamber would be expected to be cooler all around its borders, both at the top and the bottom as well as in the horizontal extremities, and these effects must also be taken into account. As the plume rises it melts and incorporates other crustal rocks. A professor in Virginia Tech's College of Science wants to power planes and cars using energy stored in their exterior shells. This could move the "ages" to tremendously high values. In a similar way, argon could enter the rock from the air or from surrounding rocks and make it look older.