Absolute chronometric dating

03-Nov-2017 16:23

Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks.Radioactive potassium-40 is common in micas, feldspars, and hornblendes, though the closure temperature is fairly low in these materials, about 125°C (mica) to 450°C (hornblende).

This scheme is used to date old igneous and metamorphic rocks, and has also been used to date lunar samples.When an organism dies, it ceases to take in new carbon-14, and the existing isotope decays with a characteristic half-life (5730 years).