Daughter element

In these cases what is usually measured is not the time of the original formation of the rocks, but the time at which the parent and daughter elements were last separated. That is, if the rocks were remelted at some point in their history in a manner that removed the daughter elements, this would be the age measured. For the measurements this is especially important. The daughter is a gas and thus could escape at any time when it was not sealed in. The decay sequences of Th, and all have gaseous members in their decay chains (see Tables 1 and 2), but the final members are solids. 

All of these daughter isotopes occur naturally thus it is always necessary to show that in the rocks of interest the daughter element present originated only from the decay of the parent, or the fraction of the daughter isotope that is from the decay of the parent must be separately determined. 

The bulk of both monazite and bastnaesite is made up of Ce, La, Nd and Pr (in that order) but, whereas monazite typically contains around 5-10% Th02 and 3% yttrium earths, these and the heavy lanthanides are virtually absent in bastnaesite. Although thorium is only weakly radioactive it is contaminated with daughter elements such as Ra which are more active and therefore require careful handling during the processing of monazite. This is a complication not encountered in the processing of bastnaesite. 

In magmatic processes, both parent and daughter nuclides are usually present in the solid sources, magmas and crystallizing minerals, so that (N2), which is a priori unknown, cannot be neglected. In order to solve Equation (I) for t, the age of fractionation, both terms of this equation are divided by the concentration of a stable isotope (or the activity of a long-lived isotope) of the daughter element. Such a normalization, similar to those used in other classical radiometric methods (Rb-Sr, Sm-... 

The radioactive nature of uranium and associated daughter elements adds an additional dimension to geochemical... 

The event to be dated must fractionate the parent and daughter elements, and homogenize the daughter isotopic ratios so that the ratio was the same in every mineral at the beginning of the system. Only an event that results in identical isotopic ratios and the differentiation of parent and daughter nuclides can be dated. 

The failure to discover francium earlier is easy to understand when it is remembered that the half-life of the longest lived isotope is only 21 minutes. This gives the element the distinction of being the most unstable to radioactive disintegration of all elements up to number 98 (38). It is also noteworthy that this is the only element in the group discussed in this chapter which was not discovered by artificial preparation in the laboratory. Nevertheless, the rarity of actinium in nature is so great that this element is best prepared artificially when its properties or those of its daughter elements are to be studied. 

As with the Sm- Nd and Re- Os systems, careful chemistry is required to cleanly separate the parent and daughter elements because mass spectrometry cannot resolve 176Lu from 176Hf. The ion-exchange chemistry is similar to that for samarium-neodymium. In fact, fractions of samarium, neodymium, lutetium and hafnium are often produced in a single procedure. Mass spectrometry is done by ICPMS because this is the only method that effectively ionizes hafnium. 

The other is the ratio of the abundance of the reference isotope of the parent element to the abundance of the reference isotope of the daughter element ... 

Three types of isochron diagrams are used in discussions of short-lived radionuclides. An internal isochron is one based entirely on measurements from the object being dated. By measuring several minerals with different parent/daughter elemental ratios, one can obtain an array of data that gives both the initial ratio (NR/Ns)a and the initial isotopic ratio of the daughter element Figure 8.25 shows an example of an internal isochron for an... 

Often, however, the sample does not lend itself to measurements of multiple phases. In these cases, one can create a model isochron in which the initial isotopic ratio of the daughter element (D(/Dref) is assumed and is used to anchor the -intercept. With this assumption, a single measurement can provide the initial ratio [(NR/Ns)o of an object. A third type of isochron diagram makes the assumption that a group of bodies all formed from the same homogeneous isotopic reservoir at the same time. This whole-rock isochron is constructed from bulk measurements of each sample, and the resulting slope and initial ratio describe the reservoir from which all of the samples formed. 

Theoretical Considerations. For a nuclear pair, the number of daughter element nuclei (N2) formed by the decay of parent nuclei (N1) varies as a function of time (t) as shown in equation (1), where X and X2 are the respective decay... 

Radium is a daughter element, the result of the radioactive decay of long-lived uranium. 

DECAY PRODUCT. A nuclide resulting from the radioactive disintegration of a radionuclide, being formed either directly or as the result of successive transformations in a radioactive series. Also called daughter, or daughter element. A decay product may be either radioactive or stable. 

The geological separation of the parent and daughter elements at the time of foimation of the mineral was sufficient to make the determination of the decay products unambiguous. For example, if a uranium mineral does not exclude all lead at the time it is formed, the isotopic abundance of the lead at the time of formation cannot be calculated with certainty. 

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