Natural Sciences >> Geology

Uranium-Lead Radiometric Dating

by 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. Uranium-lead dating is an example of the isotopes used in 


the radiometric dating that corresponds to the parent element uranium-238 (U-238) and the 


decaying daughter element lead-206 (Pb-206). According to Marshak (2008), the half-life of 


U-238 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 U-238 and Pb-206. 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 half-life 


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.                       




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Advisors :
Arcadii Grinshpan, Mathematics and Statistics
Liana Boop, Geology
Suggested By :
Yamil Jimenez