Single grains, thermal histories, and the 40Ar/39Ar method

A key part in unraveling the history of the physical evolution of the earth is knowledge of the earth's thermal history. 40Ar/39Ar step heating of mineral samples provides a means of defining a local thermal history. to do this accurately the challenge is to extract meaningful diffusion parameters from a mineral's Arrhenius plot. In the case of biotite single grains, where the laboratory release of argon is a complex process, this can be a difficult task. (12 refs., 5 figs.)