Radiometric dating involves the process of a radioactive element, such as uranium, decaying into another element, such as lead. Uranium-lead radiometric dating would be a good clock for estimating the age of rocks if we knew the following.
(A.) The rate at which uranium decays into lead.
(B.) How much lead was in the rock when it was formed.
(C.) All of the lead that was not in the rock when the rock was formed came from decaying uranium.
(D.) There is no way any extra lead or uranium could have gotten into the rock from the outside.
(E.) There is no way any of the original lead or uranium could have gotten out of the rock, such as by differential leaching.
(F.) The process has always been uniform. In other words, A, C, D, and E have each always remained constant throughout the age of the rock.
I had hoped you would have responded on my previous post addressing your post #878, of which I have quoted only the above portion dealing with the Uranium-Series dating method. Here is some additional information with some specifics I hope you will understand.
What your source probably describes is the uses and applications of U/Pb dating, which are quite outdated (no pun intended). Also, to associate U/Pb dating as a generality of all radiometric dating is a gross miss application and demonstrates ones utter ignorance of not only the Uranium-Series, but all dating methods.
To begin with, note that my last reference mentioned the Uranium-Series. That right, Uranium does not decay directly to Lead. It does not now, never has, and never will, thus the emphasis on "series". Uranium progresses through a series of specific decays involving a number of isotopes, before becoming stable with a Lead isotope. I will explain, which is very important to understand where your source misleads you.
There are "three" basic series. One begins with 238U and progresses through seven daughter isotopes of significantly different half-lives before winding up on the stable isotope 206Pb. Another one begins with 235U and progresses through five daughter isotopes before winding up on the stable isotope 207Pb. A third series involves Thorium witch begins with 232Th, progressing through four daughter isotopes before stabilizing on 208Pb.
Here's a diagram of the process in which I will only include the isotopes involved. If anyone wants to know the half-lives of those isotopes, just let me know and I will provide them.
239U-->234Th-->234Pa-->234U-->230Th-226Ra-->222Rn-->206-Pb
235U-->231Th-->231Pa-->227Ac-->227Th-->207Pb
232Th-->228Ra-->228Ac-->228Th-->208Pb
When the activity of each of the daughter isotopes equal that of the parent isotope, as measured in numbers of disintegration's per unity time per unity weight of rock, it reaches a state of "secular equilibrium". And please note that the term "secular" in no way refers to any difference or relationship between religious or non-religious. NOTHING.
Now, that describes the so-called "assumed" closed state, which is not assumed. As I have stated before the YEC literature misapplies the term "assumes". In all dating methods textbooks, classrooms, and teaching labs; the term "assumed" is used to make the student understand that one cannot in fact "assume" pristine conditions. Once the student learns the process, then the student is taught the methods and processes in which those assumptions may be investigated, determined, and accounted for.
With particular emphasis on the Nasturtium-Series one of the possible problems investigated is "disequilibrium" This is a process known as Uranium-Series disequilibrium dating. This involves two different ways for determining disequilibrium within the series. One is the "daughter deficient" (DD) method and the other is the "daughter excess" (DA) method. In doing this, the ratios of all the series isotopes is examined. Because each of those daughter isotopes has its own unique half-life, it can be determined between ratio comparison if any of the ratios are in excess or deficient. Thus, calculation and adjustments in either of those deficiency's can be made, (if any exist), bringing the sample back into "secular equilibrium".
Additionally, the isochron technique, which I know has also been misrepresented in the YEC literature, but that's another story, can be used to make the same adjustments. And I didn't even mention "thermal ionisation mass spectrometry" or multi-collector inductively coupled-plasma mass spectrometry".
In conclusion, what you see in the YEC literature concerning dating methods is analogous to a high school drop-out performing quadruple bypass heart surgery? It doesn't happen that way. And NO! The YEC literature in describing dating methods is not just another opinion. It is deliberately misrepresented material specifically designed to influence laypeople who have no intention of fact checking anything into believing something that is not true. What's next, a campaign to show that telescopes and probes throughout the solar system are unreliable sources in demonstrating that the sun is the center of the solar system rather than the earth. Ask yourself, would Jesus approve of such practices?