STRIKE-SLIP TECTONICS AND GRANITE PETROGENESIS

Transpression is a process that thickens the crust and therefore in obliquely convergent orogens as in normally convergent orogens there is the potential to generate granitic melts. Individual transcurrent shear zones may not only control the ascent paths, siting, and emplacement mechanisms of plutons, but they may also cause the genesis of the granitoids themselves. Two contrasting situations are examined. In the Hercynian shear zones of Iberia, thickening together with hydrous fluxing along shear zones created intracrustal wet melting of fertile Gondwanan sediments to produce syntectonic granites. In the northern part of the British Caledonides, the association of compositionally expanded granitoids with a major mantle component and transcurrent shear zones may be explained by melting of continental crust at the lower limits of crustal transpressional faults detaching into the Moho.