Or, was there some argon trapped in the rocks originally? K since their formation, or if some or all of it came from the mantle or from other crustal rocks and minerals.
Finally in 1976, it was discovered that the earth is "really" 4.6 billion years old What happened?Following the discovery of radioactivity by Becquerel (1896), the possibility of using this phenomenon as a means for determining the age of uranium-bearing minerals was demonstrated by Rutherford (1906).One year later Boltwood (1907) developed the chemical U-Pb method. By combining Von Weizsackers argon abundance arguments with Kohlhorsters observation that potassium emitted gamma-radiation, Bramley (1937) presented strong evidence that potassium underwent dual decay.These first geochronology studies yielded the first absolute ages from geologic material, which seemed to indicate that parts of the Earth's crust were hundreds of millions of years old. There is, of course, one radiometric dating method that appears to overcome the vital "zero date problem".The isochron dating method theoretically overcomes the need to know the initial ratio of parent and daughter isotopes. For now, we will look at those methods that do fall under the above assumptions.