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大别山东部超高压变质带北侧的花岗片麻岩有下列特征。（１）化学成分富硅、富碱，一般ＳｉＯ２＜７５％，Ｋ２Ｏ＋Ｎａ２Ｏ＞８％，且Ｋ２Ｏ＞Ｎａ２Ｏ。（２）与变质表壳岩有侵入接触关系，有异源、深源包体。（３）主要为鳞片花岗变晶结构，有残留的岩浆结构，普遍具片麻状构造，钾长石常以眼球状巨晶出现，剪切带中发育Ｌ＞Ｓ型变形组构。（４）变质作用为角闪岩相，变质矿物为黑云母、角闪石以及少量石榴石、白云母、绿帘石等。。（５）锆石的乙—Ｐ６同位素年龄值为６２９Ｍａ。上述特征与超高压变质带中的含霓石变质花岗岩有明显的区别，因此，它可能是杨子大陆板块的俯冲基底。
The granitic gneiss on the north side of the UHP metamorphic belt in the eastern part of the Dabie Mountains has the following characteristics. (1) silicon-rich chemical composition, alkali-rich, generally SiO2 <75%, K2O + Na2O> 8%, and K2O> Na2O. (2) Intrusive contact with metamorphic crustal rocks, with heterogeneous and deep-sourced inclusions. (3) It is mainly composed of scale-like granodiorite structure with residual magmatic structure, generally with gneiss structure. Potash feldspar often appears with spherical giant crystals, and L> S-shaped deformation structure is developed in shear zone. (4) Metamorphism is amphibole facies, metamorphic minerals are biotite, hornblende and a small amount of garnet, muscovite, epidote. . (5) B-P6 zircon age of 629Ma. The above characteristics are obviously different from those of metamorphic granite in the UHP metamorphic belt. Therefore, it may be the subducted basement of the Yangzi continental plate.