Decomposition of kyanite and omphacite occurred during the decompression of kyanite_ bearing eclogite at Rongcheng County, forming coronas around kyanite and symplectite afteromphacite. The coronas are composed of intergrowth of anorthite and radial vermicular Fe-Mg spinel in the inner part (inner corona) and anorthite along the rim (outer corona). The symplectite is made up of intergrowth of myrmekitic diopside and plagioclase (An30). Textural criteria suggest that the corona and the symplectite are coupled. The quantification of material transfer indicates that the formation of the corona gained Ca, Mg and Fe from the breakdown of the omphacite but provided no silica for the symplectization of the omphacite. The formation of the corona included two reactions, which took place simultaneously at different sites: reaction 1: 1Kyanite + 0.096Mg + 0.128Fe + 0.275Ca= 0.275An + 0.224Sp + 0.395Si +0.979Al + 1.778O; reaction 2: 0.451Si + 0.434Al + 0.212Ca + 0.013Na + 1.778O =0.225An. The silica, Al and O in reaction 2 were part of the products of the reaction 1. Two reactions between end_members of the omphacite are assumed, which provided Ca, Fe and Mg for the coronazition of the kyanite, and produced symplectite after omphacite: Na2O·Al2O3·4SiO2+CaO·MgO·2SiO2=2NaAlSi3O8+MgO+CaO (jadeite） (diopside) (Ab) 2CaO·2Al2O3·2SiO2+CaO·FeO·2SiO2)=2CaAl2Si2O8+FeO+CaO Ca-Tsch (hedenbergite） （An） These two coupled-decomposed minerals do not constitute a closed system. The decomposition of both omphacite and kyanite obtained silica from their surroundings.