Argon argon dating problems
So with their encouragement I will attempt to explain the method and the criteria used to interpret the data generated from a Ar step-heating experiment.
The recent development of small volume low-background noble gas extraction systems and low-background high-sensitivity mass spectrometers have improved our ability to more accurately and precisely date geologic events. 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).As with any dating technique, there are some significant limitations. 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.These each have 19 protons and 21 neutrons in their nucleus.If one of these protons is hit by a beta particle, it can be converted into a neutron.For a complete discussion on the development of the Geologic time scale see Berry, (1968). Following the discovery of radioactivity by Becquerel (1896a,b,c) near the end of the nineteenth century, the possibility of using this phenomenon as a means for determining the age of uranium-bearing minerals was demonstrated by Rutherford (1906). As the K-40 in the rock decays into Ar-40, the gas is trapped in the rock.In this simulation, a unit of molten rock cools and crystallizes. Note that time is expressed in millions of years on this graph, as opposed to thousands of years in the C-14 graph.