Thermal Models of Granite Generation in Collisional Orogens
The current research is aimed toward understanding processes that promote granite production in continental collisional orogens. The research applies metamorphic, structural and igneous petrology data from collisional terranes as the basis for numerical computer modeling of heat flow during various tectonic conditions. Recently we have focused our modeling on granite generation in the Black Hills part of the Trans-Hudson orogen, the Himalayas, and northern Maine.
Calculated model pressure-temperature-time paths for several sections of thickened crust during combined thrusting and unroofing during Proterozoic Trans-Hudson Orogeny in the Black Hills. The model involves shear-heating around a thrust fault initially at 35 km. Dots show 10 My intervals. Dashed portions of paths indicate garnet growth in metamorphic rocks prior to granite generation at dehydration-melting reactions.
Related Publications
Nabelek, P.I. and Liu, M. (1999) Leucogranites in the Black Hills of South Dakota: The consequence of shear heating during continental collision. Geology, 27, 523-526. PDF
Nabelek, P.I., Liu, M., and Sirbescu, M. (2001) Thermo-rheological, shear-heating model for leucogranite generation, metamorphism, and deformation during the Proterozoic Trans-Hudson orogeny, Black Hills, South Dakota. Tectonophysics, 342, 371-388. PDF
Nabelek, P.I. and Liu, M. (2004) Petrologic and thermal constraints on the origin of leucogranites in collisional orogens. Transactions of the Royal Society of Edinburgh: Earth Sciences. 95,73-85. PDF
These diagrams show two models for evolving geotherms in thickened crust. The one on the left has a normal distribution of heat-producing radioactive elements in the crust whereas the one on the right has also a shear zone at the 25 km depth. Shear-heating (or strain-heating) contributes to elevated temperatures at the shear zone and below. In both models the lithosphere is 130 km thick with temperature at the bottom 1300°C.
