Natural Sciences >> GeologyUraniumLead Radiometric Datingby Yamil Jimenez
Submitted : Spring 2014
In the field of geology the age of rocks can be determined by radiometric dating. This technique
is used to date geological material in years. There are five types of isotopes commonly used for
dating rocks. Isotopes are variants of a certain element which, have the same amount of protons
but differ in neutrons in the nucleus of the element. The use of isotopes to date a rock depends on
the mineral composition of the rock. Uraniumlead dating is an example of the isotopes used in
the radiometric dating that corresponds to the parent element uranium238 (U238) and the
decaying daughter element lead206 (Pb206). According to Marshak (2008), the halflife of
U238 is 4.5 billion years. An example of some uranium bearing minerals are zircon, apatite and
uraninite. Geologists use their knowledge of calculus, chemistry and physics and apply it to the
process of separating, extracting and analyzation of the isotopes. The process takes place in a lab
to avoid contamination from the atmosphere. Geologists use tools such as a mass spectrometer,
which uses a magnet to separate isotopes accordingly to their respective weights and measures
the ratio of parent to daughter in isotopic material. Therefore, the solution for the problem can be
calculated by comparing the abundance of the isotopes of U238 and Pb206. With the use of the
periodic table of elements and the initial concentration of the isotopes given, conversions of
grams to moles and moles to grams can be made that will allow for the concentrations of both
isotopes to be calculated at any given time in grams. To begin, a conceptual plan has to be
established with the use of two equations. The first equation is the order reaction of the halflife
expression which will provide a constant (k). The second equation applies the use of the first
order integrated rate law which will provide the age in time.
