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Identification of excess 40Ar by the 40Ar 39Ar, age spectrum technique

M. A. Lanphere·G. Brent Dalrymple
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Abstract

40 Ar/ 39 Ar incremental heating experiments on igneous plagioclase, biotite, and pyroxene that contain known amounts of excess 40 Ar indicate that saddle-shaped age spectra are diagnostic of excess 40 Ar in igneous minerals as well as in igneous rocks. The minima in the age spectra approach but do not reach the crystallization age. Neither the age spectrum diagram nor the 40 Ar/ 36 Ar versus 39 Ar/ 36 Ar isochron diagram reliably reveal the crystallization age in such samples.

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BibTeXRIS

M. A. Lanphere, G. Brent Dalrymple. 1976. Identification of excess 40Ar by the 40Ar 39Ar, age spectrum technique. https://doi.org/10.1016/0012-821x(76)90052-2

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