Start What is potassium argon dating

What is potassium argon dating

those in very ancient volcanic rock, by using potassic minerals in the same strata as a reference: a natural radioactive isotope of potassium, K-40, decays steadily into argon, which accumulates in the minerals and is measured to determine age Each sentence in English provides some type of information.

The rock sample to be dated must be chosen very carefully.

Any alteration or fracturing means that the potassium or the argon or both have been disturbed.

Finally, ​the argon atoms are counted in a mass spectrometer, a machine with its own complexities.

Three argon isotopes are measured: Ar is determined by comparison to it.

The target mineral is separated using heavy liquids, then hand-picked under the microscope for the purest possible sample.

This mineral sample is then baked gently overnight in a vacuum furnace.

The mineral sanidine, the high-temperature form of potassium feldspar, is the most desirable.

But micas, plagioclase, hornblende, clays and other minerals can yield good data, as can whole-rock analyses.

Young rocks have low levels of Ar, so as much as several kilograms may be needed.

Rock samples are recorded, marked, sealed and kept free of contamination and excessive heat on the way to the lab.

These steps help remove as much atmospheric Ar from the sample as possible before making the measurement.