Argon argon dating method
represents primordial Ar carried from source areas in the earth's mantle by the parent magmas, is inherited by the resultant volcanic rocks, and thus has no age significance.However, are all other rocks in the earth's crust also susceptible to "contamination" by excess emanating from the mantle?Dating of movement on fault systems is also possible with the Ar method.Different minerals have different closure temperatures; biotite is ~300°C, muscovite is about 400°C and hornblende has a closure temperature of ~550°C.
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.
Ar) dating is a radiometric dating method invented to supersede potassium-argon (K/Ar) dating in accuracy.
The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes. The sample is then degassed in a high-vacuum mass spectrometer via a laser or resistance furnace.
K-Ar dating has played a key role in unraveling the temporal patterns of hominid evolution as far back as the first significant discovery of East African australopithecines at Olduvai Gorge in 1959.
It was in large part due to the desire to understand the age of the Olduvai hominid remains that pioneering attempts were made to date geologically young materials using the K-Ar method.