What problems are encountered in dating metamorphic rocks Chat gratis uncensored


19-Jan-2019 18:44

If all components of a rock are of primary origin and completely unaltered, a whole-rock sample may be suitable for dating.In practice, only non-prophyritic volcanic rocks have been found to be suitable, and of these, the commonest variety dated is basalt.The determination of the ages of rocks and minerals by the measurement of radioactive elements and their decay products, and the measurement of the isotopic abundances of strontium and lead have become accepted tools for mappers, researchers and exploration geologists in oil and metals exploration.Age control is vitally important in geological, petrogenetic, tectonic and geomorphological studies and for stratigraphic correlations.This technique, sometimes referred to as the common lead method, relies on the assumption that lead-rich (or uranium poor) phases preserve the lead isotopic signatures of their source U/Pb and Th/Pb ratios.These ratios are dependent both on geological age, due to the different rates of radioactive decay of Pb, and also on geological evolution, as uranium and thorium are mobile elements during fractionation in crustal processes.Even though lead may be lost from the system, in most cases a cogenetic suite of zircons will preserve the age of crystallization.

The relatively high abundance and widespread distribution of potassium in the earths crust enables the potassium-argon (K-Ar) technique of age determination to be applied to common rocks and minerals.there is no loss or gain of either parent or daughter nuclide except that produced by the radioactive decay of one to the other.