High T/P metamorphism and granite genesis beneath ophiolite thrust sheets

It is well known that anatexis of sedimentary rocks took place in the dynamothermal aurcoles of some ophiolites, yielding granitic melts which invaded the overlying ophiolite sequences as veins and as granite bodies up to 1 km in maximum dimension. This study of the geological setting, geochemistry and thermal conditions of genesis of the granitic rocks generated during emplacement of three ophiolite complexes, the Semail thrust sheet of Oman, the Guevgueli Complex in northern Greece and the Lizard Complex in southwest Fngland, suggests that: 1) the granites probably represent minimum melts formed by water-saturated melting at about 3-5 kb pressure and 650-750 'C; 2) the protoliths were probably hemipelagic sediments containing a terrigenous component that rendered them fusable although that component varied in composition between the granites studied; 3) the oceanic lithosphere beneath which these sediments were subducted must have been young (< < 10 Ma) and hence hot at the time of subduction; and 4) high shear stresses or deep subduction are needed to account for the heat required to generate the granite bodies