Potassium argon k ar dating
The rock samples are crushed, in clean equipment, to a size that preserves whole grains of the mineral to be dated, then sieved to help concentrate these grains of the target mineral.
The selected size fraction is cleaned in ultrasound and acid baths, then gently oven-dried.
Three argon isotopes are measured: Ar is determined by comparison to it.These steps help remove as much atmospheric Ar from the sample as possible before making the measurement.Next, the mineral sample is heated to melting in a vacuum furnace, driving out all the gas.Because Ar has a very short half-life, it is guaranteed to be absent in the sample beforehand, so it's a clean indicator of the potassium content.The advantage is that all the information needed for dating the sample comes from the same argon measurement. This method is commonly called "argon-argon dating."The physical procedure for K.These effects must be corrected, and the process is intricate enough to require computers.Ar-Ar analyses cost around 00 per sample and take several weeks.These dating methods have been under constant improvement for more than 50 years.The learning curve has been long and is far from over today.The site also must be geologically meaningful, clearly related to fossil-bearing rocks or other features that need a good date to join the big story.Lava flows that lie above and below rock beds with ancient human fossils are a good—and true—example.