A RESEARCH OF MINERAL ASSEMBLAGES IN THE SHELF BASIN OF THE EAST CHINA SEA

The area of the Shelf Basin of East China Sea is about 0.77 million km2 and there are many minor structures in it. The deposits in this Shelf Basin are huge (up to 15000m thick). There would be plenty of oil and gas resource in this area Based on drilling records, two exploring wells have produced, oil and gas Fourty minerals have been identified from 559 samples of five exploring wells. Besides, there are three minerale( Moissanite, Native Lead and minute magntitzed iron ball -the dust in the space ) the sources of which are unknown. The percentages of grain size of heavy minerals have been calculated with statistic method of grain size and the light minerals have been counted with eyes, Several assemblages of heavy minerals have been determined in this paper and the corelation of these assemblages has been made already (fig2-5). The assemblages of heavy minerals of four wells ( fig 1 ) are described as follows: 1. The five assemblages of Lingfeng Well No. 1 from the top to the bottom are Amphibole-Epidote-Pyrite Assemblage(extending 428m and belonging to the Dong-ghai Group ) , Pyrite-Siderite Assemblage ( extending 576m and belonging to the Sa-ntan to the Yuquan Formation), Siderite-Tourmaline-Granet Assemblage (extanding 281m and belon ging to the upper of Oujiang Formation),Sdierite-Pyrite Assemblage ( extending 569m and belonging to the lower of oujiang Formation) , Pyrite-siderite Assemblage(extending 446m and belonging to the Lingfeng Formation ) . 2. The five assemblages of Pinghu Well No. 1 from the top to the bottom are Tourmaline-Zircon-Amphibole Assemblage ( extending 445m aed belonging to the Oonghai Group) , Zircon-Amphibole-Epidote-Siderite Assemblage ( extending 544.5m and belonging to the santan Formation), Tourmaline- Granet-Sidrite Assemblage ( extending 887.5m and belonging to the lower of yuquan Formation to the upper of Hailongjing Formation), Tourmaline-Siderte-Assemblage ( extending 2114.5 and belonging to the lower of Hailongjing Formation to the Pinghu Formation ) . 3. The five assemblage of Yuquan Well No. 1 from the top to the bottom are Pyrite-Epidote-Amphibole Assemblage ( extending 375m and belonging to the Donghai Group) , Epidote-Amphibole-Siderite Assemblage ( extending 666m and belonging to the Santan Formation), Siderite Assemblage ( extending 460m and belonging to the upper of Yupuan Formation), Zircon-Tourmaline-Granet Assemblage( extending 1065m and belonging to the lower of Yuyuan Formation to the upper of Hai-longjing Formation), Siderite Assemblage ( extending 221.5m and belonging to the lower of Hailongjing Formation to the Huagang Formation ) . 4. The five assemblage of Longjing Well No. 2 from the top to bottom are Pyrite-Amphibole-Epidote Assemblage ( extending 413m and belonging to the Dong-hai Group), Epidoteamphibole-Siderite Assemblage ( extending 497m and belonging to the Santan Formation), Siderite Assemblage ( extending 1316.5m and belonging to the Yuquan Formation), Siderite Assemblage ( extending 1316.5m and belonging to the yuquan Formation), Tourmaline-Granet-Siderite Assemblage (exending 869.5m and belonging to the Hailongjing Formation), Zircon-Tourmaline-Siderite-Gra-net Assemblage ( extending 1021.26m and belonging to the Huagang Formation to the upper of pinghu Formation ) . The assemblages of heavy minerals of Pinghu Well No. 1 and Yuquan Well No 1 can be corelated more easyly. The Longjing Well No. 2 located at the north of the Pinghu Well No. 1 and the Yuquan well No. 1 only can be corelated with two wells above from the Donghai Group to the Santan Formation. The assemblage of heavy minerals of Lingfeng Well No. 1 are different from the other wells except the assemblage belonging to the Donghai Group.