北大别饶拔寨榴辉岩早期冷却史研究

Garnet chemical zoning is preserved for Raobazhai eclogite from North Dabie Terrain. It is proposed as cation diffusion exchange between two compounds of garnet during the retrograde metamorphism of eclogite to granulite. Using one dimension plate model, we imitate the zoning by numerable solution. The result indicates that the cooling is take place in about 6-15Ma from highest temperature of granulite facie metamorphism in around 850 down to 500. It is equivalent to cooling rate of 25/Ma at first 6Ma duration. Calculation also shows that garnet zoning of Raobazhai eclogite does not effect Sm-Nd age determination. Whole–multi grains of garnet analysis can represent average Sm-Nd age. The age difference is within the range of analytical error. The different metamorphic ages obtained and its significance to metamorphism for Raobazhai eclogite is depended many factors except closure temperature.