Modelling white mica pressure-temperature-time (P-T-t) paths using thermobarometric and ⁴⁰Ar/³⁹Ar thermochronologic data

White micas are major rock forming minerals in igneous and metamorphic rocks, and their chemical and isotopic variations can be used to determine pressure, temperature and time (P-T-t) histories. We apply ⁴⁰Ar/³⁹Ar multi-diffusion domain modelling to white micas from blueschists blocks in serpentinite matrix mélange from the exhumed Baja California subduction complex. Thermal history models yielded T-t paths suggesting that ⁴⁰Ar* resides within multiple diffusion domains with varying ⁴⁰Ar* retentivity. Modelled white mica thermal histories and thermobarometric data were used to forward model continuous P-T-t paths. P-T-t paths are consistent with previous studies and are interpreted to constrain blueschist block exhumation paths within the Baja accretionary wedge. Our P-T-t models use temperature controlled ⁴⁰Ar/³⁹Ar step heat data in which argon loss by volume diffusion can be demonstrated, and for which the white mica petrogenesis is known.