Abstract: The Wanghaigang pluton, lithologically consisting mainly of quartz syenite, is a typical Late Mesozoic central stock intruded in a caldera in the coastal area of Zhejiang Province. Zircon LA-ICP-MS U-Pb dating for two representative samples yields ages of 98.3±1.2Ma and 98.5±1.3Ma, respectively, indicating that they were generated during the initial stage of Late Cretaceous. The quartz syenites consist mainly of alkali-feldspar (35%~60%), plagioclase (15%~20%, An=13~20), quartz (15%~18%), amphibole (3%~5%) and minor biotite (δEu=0.64~0.76) in the chondrite-normalized REE distribution patterns. The rocks have homogeneous Sr, Nd isotopic compositions with ISr values of 0.7089~0.7090 and εNd(t) values of -6.16~-7.12. However, their zircon Hf isotopic compositions are highly variable with εHf(t) values ranging from -12.2 to -2.9. Using the zircon saturation geothermometer proposed by Watson and Harrison (1983), and the Al-in-hornblende geobarometer of Johnson and Rutherford (1989), the rock-forming temperature and pressure have been estimated. The results have shown that the pluton was crystallized in a high temperature (826~846℃) and hypabyssal (emplacement depth of about 2~3km) environment. The integrated petrology, elemental and isotopic compositions suggest that the pluton was most likely generated under a back-arc extensional setting, and via a process including formation of parental magma by mixing of a underplated mantle-derived magma and an induced crustal-melted magma in the deep crust, then suffered differentiation during magma ascent and at last emplaced at a hypabyssal environment.