Encyclopedia of Scientific Dating Methods

Living Edition
| Editors: W. Jack Rink, Jeroen Thompson

Uranium-Lead, Zircon

  • Fernando Corfu
Living reference work entry
DOI: https://doi.org/10.1007/978-94-007-6326-5_23-4

Definition

Uranium-lead: Long-lived radioactive isotopes of uranium (235U and 238U) decay to stable lead (207Pb and 206Pb, respectively) at a rate, which is constant but different for the two systems. The ratio of accumulated lead to remaining uranium is a function of time and is a direct measure of the time of formation of minerals and rocks.

Zircon: A mineral consisting principally of zirconium, silicon, and oxygen and with trace amounts of uranium.

Main Characteristics of Zircon

Zircon is an orthosilicate with a tetragonal crystal structure and the chemical formula ZrSiO 4. It occurs as equant to prismatic crystals of various elongations but also as grains with subrounded anhedral shapes due to resorption and grinding during metamorphic and/or sedimentary reworking (see Fig. 1). The mineral has a hardness of 7.5 and a density of 4.7 g/cm 3, decreasing to 3.9 in heavily radiation-damaged (metamict) grains. Uranium is incorporated in the crystal in trace amounts (zero to several...

Keywords

Inductively Couple Plasma Mass Spectrometry Detrital Zircon Geological Time Scale Zircon Population Thermal Ionization Mass Spectrometer 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Department of GeosciencesUniversity of OsloOsloNorway