For example the amount of Rb in mantle rocks is generally low, i. First of all, the straight-line property of the isochron diagram is destroyed when the isotopes involved get shuffled between minerals. If they do not fit, it is assumed that it signifies a large geological event . Education, discipline that is concerned with methods of teaching and learning in schools or school-like…. This temperature makes the zircon hard to pull out substances out of it.