Abstract:Based on the major and trace element analysis of garnet, omphacite, and amphibole in three coesitebearing eclogite samples from the Bixiling area, central Dabie Mountains, the distribution of trace elements (especially high field strength elements) in eclogite during peak metamorphism and subsequent amphibolite facies retrograde metamorphism has been studied. Garnet and omphacite grains, which represent the peak metamorphism, are selected from eclogite. Their Eu anomalies show a correlation with a linear fitting slope of 0.75, which is similar to previous conclusions, indicating that the distribution of trace elements between them has reached an equilibrium. The contents of Na2O in omphacite grains are 6.14%~7.92%, and the contents of jadeite are more than 50%. The average metamorphic temperature obtained by garnetclinopyroxene geothermometer is T=699℃, which indicates that these omphacite crystals are formed during ultrahighpressure eclogite facies metamorphism. During UHP metamorphism, Zr (Kd=0.18~0.91) tends to enter garnet, while Hf (Kd=0.60~3.92) is more likely to enter omphacite than Zr. The content of Zr in omphacite is positively correlated with the sum of contents of Mg and Fe2+, indicating that Zr occupies the octahedral M1 site in omphacite. The content of Zr in omphacite is negatively correlated with the content of jadeite. The reason is that with the decrease of jadeite content, the M1O bond length in omphacite is shortened, which is more suitable for the entry of Zr. The jadeite content of omphacite in mantlederived eclogites in the middle Alps is low (28.4%~42.8%), and the jadeite content of omphacite in eclogites in the Bixiling area is high (44%~55%). This is the reason why Zr in the mantlederived eclogite xenoliths from the middle Alps tends to enter omphacite, while Zr in eclogite from the Dabie Mountains tends to enter garnet. It also shows that the chemical composition of host minerals is the main factor affecting the distribution behavior of high field strength elements. The trace element compositions of omphacite and amphibole show that LREE and HREE are separated during the retrograde metamorphism of amphibole facies. LREE tends to enter secondary amphibole, while HREE tends to be preserved in omphacite. Although trace elements do not reach equilibrium between amphibole and omphacite, Zr and Ba tend to enter amphibole, while Sr tends to be preserved in omphacite.