Skip to Main Content

ABSTRACT

New two-dimensional (2-D) thermomechanical finite-element models are used to test whether thrust advection, particularly at normal (10–20 km m.y.‒1) to high (>50 km m.y.‒1) horizontal slip rates, can substantially influence relatively high metamorphic heating rates (150–250 °C m.y.‒1). Simple beam models that involve a single thrust with a dip of ~30° and geothermal gradients that are initially equal in the hanging wall and footwall yield maximum footwall heating rates of 15, 32, 75, and 150 °C m.y.‒1 for imposed thrust rates of 5, 20, 50, and 100 km m.y.‒1 (5–100 mm yr‒1), respectively. Thrust rates were chosen to represent the possible range of rates interpreted in ancient collisional systems and observed in modern systems. More complex tapered wedge models, which include an elevated geothermal gradient in the hanging wall (with respect to the footwall), are intended to approximate the compressed isotherm sequences resulting from thrust-related hanging-wall exhumation predicted in previously published coupled thermomechanical models that include a strain continuum. In those models, thrust rates of 50 and 80 km m.y.‒1 yield maximum footwall heating rates of 112 °C m.y.‒1 and 170 °C m.y.‒1, respectively. In the immediate footwall of the regional-scale Ben Hope thrust in northwest Scotland, diffusion modeling of quartz inclusions in garnet yields heating rates of ~150–250 °C m.y.‒1. Although advective heating due to mass transfer at relatively high thrust rates cannot account for heating rates as high as those obtained from diffusion models (in Scotland and other orogens), the conduction-advection thrust models presented here suggest that thrust emplacement at relatively high rates (50–80 km m.y.‒1) can contribute substantially to the total heating budget in the footwall of major thrusts. Additionally, the distribution of both footwall heating and hanging-wall cooling due to advective heat transfer along faults may have implications for the distribution of prograde and retrograde metamorphic assemblages in thrust belts. Other mechanisms that may substantially influence the thermal budget near crustal-scale faults may include shear heating, particularly at high rates of movement on thrusts, and pre- to synorogenic magma emplacement.

You do not currently have access to this chapter.

Figures & Tables

Contents

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal