Granite batholith radiometric dating
Various types of gneisses, migmatites and granites dominate the outcrops of the Bavarian Forest, in the southwestern Moldanubian Sector of the Bohemian Massif, providing evidence for the geological characteristics of a crustal root zone.Fourteen granite intrusions from this area have been dated by the single-zircon Pb-evaporation technique.
James Joly calculated that the Earth’s age was 89 million years on the basis of the time required for salt to accumulate in the oceans.
In geology, an absolute age is a quantitative measurement of how old something is, or how long ago it occurred, usually expressed in terms of years.
Most absolute age determinations in geology rely on radiometric methods. The most useful methods for measuring the ages of geologic materials are the radiometric methods-the ones that make use of radioactive parent isotopes and their stable daughter products, as preserved in rocks, minerals, or other geologic materials.
When the geochemical and isotopic compositions of the granites are examined, supplemented by data from previous geochemical studies, it becomes evident that the Bavarian Pfahl Zone, which runs diagonally across the Bavarian Forest, is a terrane boundary that separates two regions of peraluminous S-type plutons predominantly of crustal anatectic origin but with distinct compositional features.
Plutons located in the SW and along the Pfahl Zone (Bavarian Terrane) define a high Ca–Sr–Y suite, whereas plutons from the NE and neighbouring crystalline units (Ostrong Terrane) constitute a low Ca–Sr–Y suite.