Single-crystal U-Pb zircon age determination of the Red Mountain Pluton, Laramie anorthosite complex, Wyoming

In order to provide a precise age for the Red Mountain pluton, the youngest of the syenitic bodies of the Laramie Anorthosite complex, Wyoming, zircons were extracted and analysed for U-Pb isotopes. On a concordia diagram, the U-Pb data form a slightly discordant array. A best-fit line intersects concordia at 1439+7/+6 m.y. and 102 +- 64 m.y. (95% confidence level). The upper intercept is interpreted as the crystallization age of the Red Mountain pluton and provides a younger age limit for the rest of the Laramie Anorthosite complex.