MacArgon

MacArgon allows simulation of argon retention in minerals and rocks, and modelling and simulation of the results of argon geochronology. Arbitrary pressure-temperature-time paths can be input, and calculations are performed as how the diffusion of argon would take place from the mineral grains in question. 

Argon accumulates through radiogenic decay but is lost by diffusion, or as the result of microstructural events such as recrystallisation or diffusion domain reduction at individual control points along the pressure-temperature-time path.

Parametric inversion considers the variation obtained in families of pressure-temperature-time paths. Manual inversion takes advantage of the highly interactive nature of the graphical user interface. Monte Carlo inversion allows comparison with control points selected by the user from an observed age spectrum input in a standard XML format. 

Both Parametric Inversion and Monte Carlo simulations attempt to match the simulated spectrum with selected steps in a reference age spectrum.  A sensitivity analysis can then be performed for individual simulations. A "MacArgon document" is used to store data in XML format, allowing later retrieval and FAIR data use.

Different types of parametric inversion are facilitated by inclusion of options for flash heating or analytical solutions for cooling near igneous bodies. The temperature history above and below a compressional thrust or an extensional detachment can also be simulated prior to being applied to a mineral to generate an apparent age spectrum. 

The program allows distributions of diffusion domain size and volume that allow replication of data obtained from temperature-controlled furnace-step-heating experiments in an ultra-high-vacuum mass spectrometer designed to measure the concentration of the isotopes of argon. By considering bulk fusion the program also replicates the answers likely to be obtained using laser-spot analysis, or laser-step-heating by pulse-heating the crystals.