Define absolute dating of fossils

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In some cases the discovery of a rare trace mineral results in a major breakthrough as it allows precise ages to be determined in formerly undatable units.For example, the mineral those composed primarily of one or more ferromagnesian, dark-coloured minerals).A second advantage of the method relates to the fact that under high-temperature conditions the daughter isotopes may escape from the host minerals.In this case, a valid age can still be obtained, provided that they remain within the rock.An ideal mineral is one that has sufficient parent and daughter isotopes to measure precisely, is chemically inert, contains little or no significant initial daughter isotopes, and retains daughter products at the highest possible temperatures.A specific datable mineral like lead of mass 206 relative to that of mass 204 has changed from an initial value of about 10 present when the Earth was formed to an average value of about 19 in rocks at the terrestrial surface today.Similar studies have shown that the samarium–neodymium (Sm–Nd) parent–daughter pair is more resistant to secondary migration but that, in this instance, sufficient initial spread in the abundance of the parent isotope is difficult to achieve.trace minerals may form, each concentrating certain elements and radioactive trace elements within the rock.

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These isotopes did not come from radioactive decay in the system but rather formed during the original creation of the elements.In this case, it is a big advantage to present the data in a form in which the abundance of both the parent and daughter isotopes are given with respect to the abundance of the initial background daughter.The incremental additions of the daughter type can then be viewed in proportion to the abundance of parent atoms. It has already been shown— In practice, the isochron approach has many inherent advantages.Should a point plot below the line, it could indicate that a particular sample was open to migration of the dating elements or that the sample was contaminated and lay below the isochron when the rock solidified.Rubidium–strontium (Rb–Sr) dating was the first technique in which the whole rock isochron method was extensively employed.

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