Rubidium-Strontium dating

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The rubidium-strontium dating is a method for determining the absolute age of rocks and minerals, in which the radioactive decay of rubidium to strontium is used.

Basics

The beta decay from 87 Rb to 87 Sr with a half-life of 48.8 billion years in minerals such as mica or amphiboles enables the method to be applied to ancient metamorphic and igneous rocks.

The isochronous technique is a refinement of the method . It allows the dating of a rock without information about the initial concentration of the daughter isotope (here: 87 Sr). The condition for the applicability of the technique is the existence of another stable isotope of the daughter isotope (here: 86 Sr), which is called the reference isotope, as well as the same ratio of daughter isotope to reference isotope in all minerals of a rock sample at the time the rock was formed. The ratios of the daughter isotope to the reference isotope to be determined for the various minerals of a sample are plotted against the ratio of the mother isotope to the reference isotope. Ideally, the data points lie on a straight line, the isochronous, from the slope of which the age of the rock can be derived. The point of intersection of the isochrones then indicates the ratio of the daughter isotope to the reference isotope at the dated point in time.

application

The method was used to determine the age of rocks from the moon , which is around 4.5 billion years old.

See also

literature

  • Mebus A. Geyh: Handbook of physical and chemical age determination . Scientific Book Society, Darmstadt 2005. ISBN 3-534-17959-5 .
  • Wegmann, M., J. (2006): The development of the Rb / Sr isotope system in metamorphic microstructures as a function of temperature, pressure and mineral composition using the example of high pressure metamorphic rocks from Südevia, Greece. Dissertation, FU Berlin

Individual evidence

  1. ↑ Heuel-Fabianek, B. (2017): Natural radioisotopes: the “atomic clock” for determining the absolute age of rocks and archaeological finds. Radiation Protection Practice, 1/2017, pp. 31–42
  2. ↑ Carlson, RW; Borg, LE; Gaffney, AM; Boyet, M. (2014): Rb-Sr, Sm-Nd and Lu-Hf isotope systematics of the lunar Mg-suite: the age of the lunar crust and its relation to the time of Moon formation , Phil. Trans. R. Soc. A., 372