TEMPORAL-SPATIAL DISTRIBUTION AND TECTONIC TYPES OF OPHIOLITES IN OROGENIC BELTS OFCHINA

Ophiolites in orogenic belts of China and ultramafic rocks resulting from their disintegrationare mostly exposed along suture zones and deep faults,forming 2 rock belts of differing ages andsizes。In terms of time,ancient ophioites predominate ,Meso- Cenozoic ones come next and Protero-zoic ones are rare. Some major ophiolite belts are usually composite rock belts composed of two ormore ophiolite blocks of different ages and tectonic types. With the southern margin of the Tarim-Sino-Korean platform as the boundary,ophiolites in orogenic belts of western China have a ten-dency to become young from north to south,which might imply that there is an evolution mecha-nism of successive south-directed accretion in the western and southwestern parts of the Chinesemainland.According to the section types of ophiolites and development stages of oceanic basics,ophiolites of China may be divided into four tectonic types:initial oceanic basin type,mature o-ceanic basin type,island are type and relict oceanic basin（non- ophiolite）type of mafic-ultramaficrocks,with the first type prdominating and the others being less important.