Thermal Structure During Granite Emplacement

The thermal magnetic mineralogical measurements fig.

Thermal structure during granite emplacement.

Inverse modeling of geochemical data from postcollisional granites generated during thermal relaxation of overthickened crust is consistent with drainage. The mechanism of emplacement of granite magma into the upper crust to form plutons remains controversial. This paper is one of a series that addresses feedback relations between deformational and thermal processes brown and solar 1998a. Solar et al 1998.

Emplacement of granite plutons in areas of local extension associated with strike slip faults and shear zones is a mechanism consistent with the main structural and petrological features of many. Note that in fig. Granite emplacement results from the. Solar and brown 1999a the mechanisms of granite ascent and emplacement brown and solar 1998b and the internal structure and composition of individual plutons brown and pressley 1999.

The generation of large granite migmatite complexes by crustal melting during orogeny is a process still discussed in particular because of the deep inaccessible location of their production sites clemens 1990 brown 1994 moreover the development of a partially molten middle crust during collision tectonics implies a major change in the rheology of the thickened crust and largely control. The characteristic metamorphic imprint of the thermal weakening effect at crustal levels near the emplacement of the granite is rapid near isobaric heating during crustal thickening and subsequent cooling at constant or slightly increasing pressure. 7 part of the results involves emplacement rates that are above the critical emplacement rate for convection as discussed above. Pressley and brown 1999 in transpressive orogens.

5 a c show a gradual drop in magnetic susceptibility at 350 400 c and a rapid drop at 580 c for all three granite samples indicating the existence of magnetite and probably maghemite in the shibei granites. Detailed study of structural elements suggests that phulad granite has formed during the regional deformation in the. Figure 7 shows the width of the thermal aureole w t in the granite overlying sediments for a granite roof at 10 km and sill thickness of 50 m for a total granite thickness of 5 km. Granite emplacement is related with the development of major structures so the location of syn to post orogenic granitoids are a valuable indicator of an inherited large scale crustal.

Indeed such anticlockwise pt paths are common in many high t low p metamorphic terrains found in ancient apparently convergent orogenic belts 4 5.