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前人工作认为北大别榴辉岩在榴辉岩相变质后,经历了麻粒岩相退变质作用,因此获得的Sm-Nd矿物等时线年龄代表了麻粒岩相变质时代。本文对北大别安徽洪庙百丈岩榴辉岩相岩石(辉石石榴石岩)的研究表明,该岩石经历了三叠纪超高压变质作用,经历了角闪岩相退变质。所研究样品在峰期变质之后是否经历了麻粒岩相退变质尚不能明确界定。结合矿物氧同位素体系平衡判据,辉石石榴石岩在峰期变质时达到了Sm-Nd同位素体系的均一化和平衡,并且在后期角闪岩相退变质中该同位素体系未出现明显的扰动,因此其Sm-Nd矿物等时线年龄犤(225±14)Ma和(229±13)Ma犦代表了榴辉岩相变质时代。同时,样品中矿物的同位素组成表明,在俯冲板块折返和退变质过程中,岩石受到外来和内部流体的不均匀作用,造成退变的单斜辉石在同位素组成上的不均一。
Previous work suggests that the North Dabie eclogite experienced the metamorphism of granulite after metamorphism of eclogite. Therefore, the obtained isochron age of Sm-Nd mineralization represents the era of granulite-facies metamorphism. In this paper, a study on the eclogites (pyroxenite rock) of the Baizhangyan eclogite in Anhui Province, Anhui Province, shows that the rock underwent the Triassic UHP metamorphism and underwent the metamorphism of the amphibolite. Whether the studied samples undergo metamorphic retrogradation of granulite after the peak metamorphism can not be clearly defined. Based on the equilibrium criterion of mineral oxygen isotope system, the pyroxene-garnet rock reaches the homogeneity and balance of the Sm-Nd isotopic system during peak metamorphism, and there is no obvious perturbation in the late metamorphism of amphibolite , The Sm-Nd mineral isochron ages 225 (225 ± 14) Ma and (229 ± 13) Ma 犦 represent the era of eclogite facies metamorphism. At the same time, the isotopic composition of minerals in the samples indicates that the rocks are subjected to inhomogeneous external and internal fluids during the reentrancy and retrogressive metamorphism of the subducted slabs, resulting in the heterogeneity of the degenerated clinopyroxenes in the isotopic composition.