40Ar/39Ar Thermochronology for Submilligram Samples Using a Ta Platform Microfurnace, With Illustrations From the Bushveld Complex

We present a method for 40Ar/39Ar step‐heating measurements on anhydrous K‐bearing minerals. Samples placed in dimples on Ta foil platforms are heated indirectly with a laser while temperatures are measured with a two‐color pyrometer. The system provides a simple, inexpensive, and reliable means for the heating of samples as small as a few to tens of micrograms. Results for plagioclase separates from the Rustenburg Layered Suite of the circa 2.06 Ga Bushveld Complex closely match previously published data. Key Points Tantalum platforms provide a simple and reliable support for the indirect, reproducible, stepwise laser heating of microgram samples Plagioclase diffusion parameters measured from the Bushveld Complex closely match published data from the complex, validating the method