Potassium (K) is one of the most abundant elements in the Earth's crust (2.4% by mass).
One out of every 10,000 Potassium atoms is radioactive Potassium-40 (K-40).
With 18 protons and 22 neutrons, the atom has become Argon-40 (Ar-40), an inert gas.
For every 100 K-40 atoms that decay, 11 become Ar-40.
From June 6-8, 2017, our New Mexico Geochronology Research Laboratory will host 35 geochronologists from 7 countries to discuss multiple topics that impact radiometric dating of rock samples and noble gas measurements.
The isotopes the KAr system relies on are Potassium (K) and Argon (Ar).
Potassium occurs in two stable isotopes (Ar atoms trapped inside minerals.
The potassium-argon age of some meteorites is as old as 4,500,000,000 years, and volcanic rocks as young as 20,000 years old have been measured by this method.That is, a fresh mineral grain has its K-Ar "clock" set at zero.The method relies on satisfying some important assumptions: Given careful work in the field and in the lab, these assumptions can be met.The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.Developed in the 1950s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale.Because it is present within the atmosphere, every rock and mineral will have some quantity of Argon.