DEEP SEISMIC STRUCTURE AND THERMOMECHANICAL MODELING OF CONTINENTAL COLLISION ZONES

A series of 2D thermo-mechanical models are presented which quantify c rustal thickening and the resulting temperature perturbations associat ed with thrusting in an attempt to constrain the existence of temperat ures responsible for the generation of anatectic granites in a compres sional environment. Deformation is assumed to occur in the crust by a simple thrusting mechanism, the Moho acting as a detachment surface, a s has been observed on deep seismic reflection data, while the more du ctile sub-crustal lithosphere is assumed to behave elastically and def orm in a pure shear manner. Investigated are the relative effects of t he rate of crustal shortening, the distribution of radioactive element s within the crust, the reduced heat flow from the mantle, isostasy an d erosion. Our results show that previous oversimplified 1D models sig nificantly overestimate the elevated temperatures in lower crustal reg ions caused by radiogenic heating, and that this mechanism will only h ave a significant effect in regions of relatively thin lithosphere, or where there are unusually high rates of radiogenic heating in the cru st. Generation of synthetic P-T-t data for locations deep down in the lower crust enables us to quantify the temperatures produced following a period of compressional deformation, providing insight into the tim e scales involved for the generation of crustal melt granites within a n orogenic belt.