HR: 0800h
AN: T21C-0514    [Abstracts]
TI: Thermal Evolution of a Simple Thrust Sheet: Two-dimensional Modeling and Application to Thrust Kinematics
AU: Rodgers, D W
EM: rodgdavi@isu.edu
AF: Idaho State University, Department of Geosciences, Pocatello, ID 83209 United States
AU: * Huerta, A D
EM: ahuerta@geosc.psu.edu
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AB: To better understand the transfer of thermal energy in collisional orogens, and thus better interpret thermochronologic and structural data, we have developed a 2D finite difference thermal model of a simplified thrust system. In particular, we examine the modeled evolving thermal structure and PTt evolution of hanging wall rocks that experience fault bend folding due to transport over a blind footwall ramp with coeval stream-power-style erosion. Model results show that thickening of heat-producing crust can raise the geotherm of the hanging wall and result in heating of rocks as they pass over a footwall ramp and onto the upper flat. In all cases, modeled rocks cool as they move over the footwall ramp, potentially providing a common pin-point for determining thrust rates. The timing of subsequent cooling of rocks is highly dependent on the location of the sample in the hanging wall (both depth and horizontal location) as well as relative rates of thrusting and erosion. These model results suggest cooling ages of rocks in real thrust belt systems may occur during thrusting over a footwall ramp or may occur millions of years later when the sample has moved on further into the foreland. The combination of directed sample transects and thermal modelling can provide quantitative constraints on kinematic and erosion rates. In the simplest case, low-temperature thermochronology of minerals that pass through their closure temperature over the ramp will yield details on thrust kinematics (thrust rate, timing of initiation and duration of thrusting). Additional cooling ages of a more comprehensive sample suite may capture late-stage cooling due to erosion after movement over the thrust ramp. In these latter cases, model results can place constraints on erosion rates.
DE: 1140 Thermochronology
DE: 3652 Pressure-temperature-time paths
DE: 8108 Continental tectonics: compressional
SC: Tectonophysics [T]
MN: Fall Meeting 2005