Due to the relatively heavy atomic weight of potassium, insignificant fractionation of the different potassium isotopes occurs.However, the Argon, a noble gas, constitutes approximately 0.1-5% of the Earth's present day atmosphere.Therefore, mafic rocks and minerals often contain less potassium than an equal amount of silicic rock or mineral.
This document presents a short tutorial on the development and application of The study of geology grew out of field studies associated with mining and engineering during the sixteenth to nineteenth centuries. So with their encouragement I will attempt to explain the method and the criteria used to interpret the data generated from a Ar step-heating experiment. I have just completed the data reduction on a low potassium basalt from the Medicine Lake, California, the basalt of Tionesta. Freeman and Company, San Francisco and London, 136 p. Congratulations to Susie on the well-deserved citation!The isotopes the KAr system relies on are Potassium (K) and Argon (Ar).The results from this sample are an excellent example of the advantages of Ar methods of dating have been successfully applied to many fundamental Earth science problems, including the establishment and calibration of the Geomagnetic Polarity Time Scale (GPTS), calibration of the Paleontological Time Scale (PTS), calibration of Hominid evolution, and numerous tectonic studies.