Abstract:

Chinese continental scientific drilling (CCSD) well is located in Donghai County which lies in the southern part of Sulu ultrahigh pressure metamorphic zone. The seismic survey is one of the multiscientific integrated research projects. The well has been surveyed by world advanced digital seismic instrument (HF300) and three component digital geophone (geochain). Combining the achievement of seismic survey and the information of rock core 5 000 mCCSD, and through detailed analyses of deep structure reflection characteristics of seismic profile, we found that there is a threeunitlayer structure in the deep area. Six strong reflection bands appeared within 11 km in the firstunitlayer with the basically consistent attitudes, the trend is SE and the dip angle is 28 degree. The rock core sample and the VSP exploration data confirmed that the front four reflection bands are mainly the reflections from the eclogite and the ductile shear zone. The eclogite zone and the gneiss are distributed as irregularly alternative layers. Four quite clear reflection bands appeared between approximate 11 km to 30 km in the secondunitlayer, whose energy is weak, and the reflection continuity is poor. There are some weak anomalous reflections among the four bands. Their attitudes are also consistent basically, however, the dip angle is very small and the trend changes gradually to NW from shallow area to deep area. The interaction relation between the firstunitlayer and the secondunitelayer is angular unconformity. Only one quite strong reflection band appeared below approximate 30 km in the thirdunitlayer, whose continuity is good; the attitude is gentle and the trend is still NW. However, the reflections are even and there isnt any anomalous reflection below the reflection band. According to the reflection characteristics and the geologic background mentioned above, we speculate that the firstunitlayer is the turned back terrane from the subduction zone of the Yangzi and SinoKorean plate; the secondunit layer is the Yangzi Craton; the thirdunitlayer is the upper mantle, and the reflection of its top is from the Moho interface.

Key words: Key words: Chinese continental scientific drilling(CCSD), deep structure, seismic survey