UNDERSTANDING KINEMATIC DISPLACEMENT RATE EFFECTS ON TRANSIENT THERMAL PROCESSES: A COMPARISON OF ANALYTICAL (TI-DIFFUSION) AND NUMERICAL (FINITE-ELEMENT) SOLUTIONS TO FOOTWALL HEATING IN THRUST BELTS

Modeled thermal processes in collisional systems are generally considered as: 1) instantaneous thrust models (as in most 1-D models of thrust emplacement with discrete kinematic boundaries), 2) a thermo-mechanical continuum that ignores kinematic discontinuities, or 3) as transient-state processes that are considered to be relatively slow. However, geochronologic and metamorphic studies from a number of recent (e.g. Papua New Guinea) and ancient (NW Scottish Caledonides) collisional systems indicate that cooling and heating rates, respectively, may be much faster than those often considered by modeling studies. Additionally, kinematic (fault) boundaries are critical to characterizing the thermal architecture of orogenic and exhumational systems. For example, in the NW Scottish Caledonides, analysis of Ti diffusion profiles of quartz inclusions in garnet indicate heating rates up to 500° C Myr^-1, and in Papua New Guinea, analysis of eclogite facies assemblages yields cooling rates at >100 °C Myr^-1. In this contribution, we use 2D coupled mechanical (explicit) and thermal (implicit) finite element models (Elfen FE Software) of thrusting and erosion at different rates (1 km Myr-1 to 50 km Myr-1) to determine boundary thermal conditions for these systems.