Potassium argon dating method
The amount of is also measured to assess how much of the total argon is atmospheric in origin. 11) the following assumptions must be true for computed dates to be accepted as representing the true age of the rock: Both flame photometry and mass spectrometry are destructive tests, so particular care is needed to ensure that the aliquots used are truly representative of the sample.Ar–Ar dating is a similar technique which compares isotopic ratios from the same portion of the sample to avoid this problem.(argon), the atom typically remains trapped within the lattice because it is larger than the spaces between the other atoms in a mineral crystal.
In these materials, the decay product is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes).Our editors will review what you’ve submitted and determine whether to revise the article.Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work! This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.Clay minerals are less than 2 μm thick and cannot easily be irradiated for Ar–Ar analysis because Ar recoils from the crystal lattice.
In 2013, the K–Ar method was used by the Mars Curiosity rover to date a rock on the Martian surface, the first time a rock has been dated from its mineral ingredients while situated on another planet.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.