Radiometric dating applied metamorphic rocks

24-May-2020 13:41

Because the metamorphic complex is poorly dated paleontologically, isotopic dating is the principal means to study the magmatic activities, metamorphic episodes, and crustal movements in the metamorphic rocks.

As radiometric dating laboratories were not operating in this country when this text was prepared, most geo chronologic analyses have been produced in the laboratories in other countries. and French scientists (Yen and Rosenblum, 1964; Juan, Chow and Lo, 1972; Jahn and Liou, 1977; Jahn, Liou and Nagasawara, 1981,; Jahn and others, 1986; Juang and Bellon, 1986).

By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.

Radiometric dating is also used to date archaeological materials, including ancient artifacts.

The possible confounding effects of contamination of parent and daughter isotopes have to be considered, as do the effects of any loss or gain of such isotopes since the sample was created.The present data do not adequately cover the entire extent of the metamorphic terrain, or all significant rock types.Additional radiometric dates of critical rock types and careful stratigraphic analysis will no doubt clarify and modify our present knowledge of the geologic development of the metamorphic complex to a considerable degree.By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay (each radioisotope has its own decay constant), the isotopic age of the sample can be calculated.For dating minerals and rocks, investigators commonly use the following couplets of parent and daughter isotopes: thorium-232–lead-208, uranium-235–lead-207, samarium-147–neodymium-143, rubidium-87–strontium-87, potassium-40–argon-40, and argon-40–argon-39.

The possible confounding effects of contamination of parent and daughter isotopes have to be considered, as do the effects of any loss or gain of such isotopes since the sample was created.

The present data do not adequately cover the entire extent of the metamorphic terrain, or all significant rock types.

Additional radiometric dates of critical rock types and careful stratigraphic analysis will no doubt clarify and modify our present knowledge of the geologic development of the metamorphic complex to a considerable degree.

By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay (each radioisotope has its own decay constant), the isotopic age of the sample can be calculated.

For dating minerals and rocks, investigators commonly use the following couplets of parent and daughter isotopes: thorium-232–lead-208, uranium-235–lead-207, samarium-147–neodymium-143, rubidium-87–strontium-87, potassium-40–argon-40, and argon-40–argon-39.

Isotopic systems that have been exploited for radiometric dating have half-lives ranging from only about 10 years (e.g., , whose decay rate may be affected by local electron density.