U and Th are found on the extremely heavy end of the Periodic Table of Elements. Furthermore, the half life of the parent isotope is much longer than any of the intermediary daughter isotopes, thus fulfilling the requirements for secular equilibrium Section 2. We can therefore assume that the Pb is directly formed by the U, the Pb from the U and the Pb from the Th. The ingrowth equations for the three radiogenic Pb isotopes are given by: 5. The corresponding age equations are: 5. This assumption cannot be made for other minerals, young ages, and high precision geochronology.
The Institute for Creation Research ICR has recently completed their multi-year project dealing with a scientific evaluation of the age of the earth and produced two book publications and an accompanying DVD. Within their research, the ICR research team makes many claims that geological evidence, including their findings dealing with dating rocks using the fission track dating method, provides substantial evidence for a young earth. In order to evaluate ICR's findings, one must first establish a proper methodology for fission track dating and compare ICR's methodology and finding to previous results. Fission tracks, as physical structures, are simply linear tracks in rock crystals usually about meters long. Fission tracks are most often caused by the spontaneous fission of the parent Uranium atom into two daughter atoms of palladium Fission track dating is somewhat of an anomaly in the field of radiometric dating.
Uranium—lead dating , abbreviated U—Pb dating , is one of the oldest  and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4. The method is usually applied to zircon. This mineral incorporates uranium and thorium atoms into its crystal structure , but strongly rejects lead when forming.
Isotopical Studies on Zircons. Larsen et al. They proposed the so-called lead-a method, or Larsen method, a non-isotopic method of age determination. Tilton et al.