The Sulu UHP terrane: A review of the petrology and structural geology

Petrological and isotopic evidence suggests that the protolith of the Sulu ultrahigh-pressure (UHP) terrane was Precambrian continental crust consisti ng of granite, granodiorite, gabbro, marble, and basic dikes, with local gr anulite-facies assemblages. Around 220 Ma this unit of continental rocks wa s buried to depths up of similar to 120 km within the mantle. Structures fo rmed during exhumation suggest highly mobile behavior of acidic rocks, even under conditions of very low water activity. Petrological studies show tha t the Sulu terrane underwent isothermal decompression, which implies relati vely rapid exhumation, and suggests that the role of melting during exhumat ion may have been underestimated. The later stages of exhumation are associ ated with NW-SE-directed tectonic transport and the formation of at least o ne major normal detachment.