Meaning of Tera–Wasserburg diagram | Babel Free

Definitions

A type of concordia diagram, used in the context of uranium–lead dating, whose axes are the ratios ²⁰⁷Pb/²⁰⁶Pb and ²³⁸U/²⁰⁶Pb.

Equivalents

Examples

“The axes of the Tera–Wasserburg diagram are the amounts of ^{₂₀₇}Pb (a stable, radiogenic isotope unconnected with uranium series decay) and ^{₂₃₈}U (the start of the uranium series decay chain), each adjusted and expressed as ratio to the amount of ^{₂₀₆}Pb (the stable end product of the uranium series).”

“One feature of the Tera–Wasserburg diagram is that for samples whose original lead content was both high and of unknown isotopic composition, the plotted points may lie on an isochron whose intersection with the ^{₂₀₇}Pb/^{₂₀₆}Pb axis gives the original lead composition and whose intersection with the concordia curve yields the age.”

“Unfortunately, zircons that have high common Pb contents often also display Pb loss. This can be checked in a Tera–Wasserburg diagram, provided that the zircons belong to a single population, since common-Pb correction should reduce the data to a single point on the concordia.”

“For all practical purposes, such distinctions are generally significant more for the specialist geochronologists rather than the geologists who are interested in using the geochronological data; however, it is important to be aware that there are subtle differences between the types of Tera–Wasserburg diagrams that can be plotted and hence how the ages can be interpreted.”

“Fig. 5.32 Meteorite mineral data on (a) Pb–Pb isotope and (b) Tera–Wasserburg diagrams, representing the back and front faces of the total-Pb/U isochron diagram.”

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