Thermal Structure During Granite Emplacement

Pressley and brown 1999 in transpressive orogens.

Thermal structure during granite emplacement.

Emplacement in a pull apart structure along a shear zone e g. Traditionally the emplacement of a granite pluton is considered to involve stoping thermal ballooning and diapirism among other factors. Indeed such anticlockwise pt paths are common in many high t low p metamorphic terrains found in ancient apparently convergent orogenic belts 4 5. The resulting thermal structures.

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. The thermal magnetic mineralogical measurements fig. Note that in fig. 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. The mechanism of emplacement of granite magma into the upper crust to form plutons remains controversial. 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 results from the.

Solar et al 1998. This paper is one of a series that addresses feedback relations between deformational and thermal processes brown and solar 1998a. 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. 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.

Detailed study of structural elements suggests that phulad granite has formed during the regional deformation in the.