The Chinese Continental Scientific Drilling (CCSD) Main Hole with a depth of 5158m located in the Donghai County, the southern Sulu ultrahigh-pressure (UHP) metamorphic belt, has been penetrated into a UHP metamorphic tectonic slab which consists of eclogite, gneiss, garnet peridotite, and minor quartzite and schist. Minerals from various rocks show large variations of oxygen isotopic composition, with ranges from -7.4 to +6. 2 for garnet, - 5. 2 to + 6. 5 for omphacite, - 4. 4 to + 7.1 for muscovite, - 3.1 to + 7.6 for plagioclase, 4. 8 to 8. 3 for K-feldspar, and - 2.8 to + 9.6 for quartz. Distinct O-isotopic depletions are observed in the frequently alternated layers of eclogite, paragneiss and orthogneiss, in which the variations of delta O-18 values are gradual, regardless of lithologies. Minimum depth of the O-isotopic anomaly has reached down to 3320 m. Eclogite-facies minerals have equilibrium O-isotopic compositions; while minerals from most gneisses have disequilibrium delta O-18 values. High-pressure and low-pressure quartz veins have similar or different O-isotopic compositions to their eclogite or gneiss country rocks. The metamorphic temperatures of 598 to 909 C for eclogites and 550 to 786 C for gneisses are estimated using the quartz-garnet thermometer of oxygen isotope. These facts, considering the distribution characters of O-isotopic depleted rocks in the outcrops and shallow drill holes of the Sulu area, suggest that: (1) a large amount of supracrustal rocks have interacted with the meteoric water during the Neoproterozoic global glaciation; ( 2)some orthogneisses from this drill hole show normal O-isotopic value, and have no any evidence of UHP metamorphism; (3) the channelized water/rock interactions and very limited fluid mobility was present during subduction and exhumation of the continental crust. The fluids related to the retrograde metamorphism of UHP rocks and the formation of some HP and LP veins are of in-situ origin; (4) the bimodal magmatic activities which were formed during the breakup of Rodinia supercontinent have provided the heating source for the rock - cold meteoric water interactions.
