Abstract:This paper presents a combined petrologic, geochemical and geochronological study and Lu- Hf isotopic analysis of granitic plutons and metamorphic rocks in Hainan Island. Two- stage (270~259 Ma and 242 Ma) magmatic events and a 251~248 Ma tectonothermal event are identified. The 270~259 Ma magmatic rocks include quartz diorites, granodiorites and garnet- bearing granites. Quartz diorites and granodiorites are metaluminous I- type granitoids with variable zircon εHf(t) values, high Mg# and CaO/Na2O ratios, and low Rb/Sr ratios. They are interpreted to form by partial melting of basaltic lower crust with minor involvement of mantle- derived melts. The garnet- bearing granites are strongly peraluminous S- type granites. They display negative zircon εHf(t) values and high CaO/Na2O ratios, indicating a crustal clay- poor, plagioclase- rich, psammitic source. All 270~259 Ma magmatic rocks are enriched in LREEs and LILEs, and depleted in HFSEs, sharing the common features of arc- related magmatic rocks. They are interpreted to be formed in the continental arc setting associated with the subduction of oceanic plate. The 251~248 Ma tectonothermal event, combined with coeval crust- derived S- type granites and ductile shearing deformation, is interpreted to be caused by arc- continent collision. The ~242 Ma granites are A2- type granites with positive zircon εHf(t) values. They were generated by partial melting of juvenile basaltic crustal material at high- temperature conditions in the post- orogenic setting. During late Permian to early Triassic, the Hainan Island experienced a tectonic transition from oceanic subduction to arc- continent collision, which was closely associated with the evolution of the Paleo- Tethys Ocean.