U th dating on calcite
The U-series laboratory focuses on development and application of U-series dating techniques to provide a robust chronological framework for palaeoclimatology, archaeology and human evolution.
The U-series disequilibrium method is based on the radioactive decay of radionuclides within the naturally occurring decay chains.
Differential solubility between uranium and its long lived daughter isotope Th is measured using MC-ICPMS.
This method has a dating range up to about 600.000 years.
How long this takes depends on the precision and accuracy of our measurements and the size of the original disequilibria (bigger disequilibria last longer).Unlike coralline aragonite, dense calcite cave formations are not as susceptible to diagenesis and have greater potential for preservation through time.Ra dating of igneous materials takes several different forms and usually require a chemical normalization using a stable or long-lived isotope of the daughter isotope, much like is in used other radiometric systems like Rb-Sr and U-Pb. This method is often called an “internal isochron” because the age of one rock is determined from the variations between minerals within it.The differing chemistries and half-lives of these nuclides (with timescales ranging from seconds to billions of years) make them exceptionally useful chronometers for variety of natural processes and materials Perhaps the most important and commonly used isotopes are Ra, the first three of which are commonly used to date the formation of carbonate minerals and skeletal materials (e.g., corals and cave deposits) and the full suite of which are used to date volcanic materials, such as lavas and the crystals they contain.Because these isotopes are related to each other by a radioactive decay chain, a material left chemically untouched for a long period of time (a “closed system”) exhibits a special condition called secular equilibrium, wherein the activity of each isotope in the chain is the same (activity is defined as the numbers of decays per unit time, which is equal to the number of atoms of that element times its decay constant).