Role of horizontal thermal conduction and finite time thrust emplacement in simulation of pressure-temperature-time paths

Comparison of metamorphic thermal histories produced by (1) one- vs. two-dimensional conductive models and (2) instantaneous vs. finite emplacement time thrusting indicates that the simple 1D or instantaneous models applied by many petrologists generally produce pressure-temperature (PT) paths with topologies similiar to those generated by 2D, time-transitive models. However, maximum temperatures attained by footwall rocks are significantly lower in 1D than in 2D conductive models, leading us to recommend that 2D thermal effects be incorporated into models whenever possible. PT paths produced by instantaneous and finite-duration thrust emplacement differ significantly during the synthrusting period, but the peak metamorphic conditions (T_MAX and pressure at T_MAX) eventually attained by footwall rocks during erosional unroofing are the same within minimum analytical uncertainties ( ± 50 K, ± 100 MPa) on geothermobarometric data. Thus, if erosion begins only after the end of the thrusting event, instantaneous thrusting is a reasonable simplifying assumption that introduces relatively little inaccuracy into PT models devised to examine peak metamorphic conditions.