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桐柏造山带高压变质地体主要由两个高压岩片(Ⅰ和Ⅱ)及其北侧的绿片岩相构造混杂岩带和南侧的蓝片岩-绿片岩带构成.高压岩片Ⅰ以北、南两条低温榴辉岩带为代表,构成桐柏山背形构造的两翼;高压岩片Ⅱ以桐柏杂岩中早白垩纪片麻状花岗岩内含有退变榴辉岩的变质岩包体为代表,构成桐柏山背形构造的核部.综合U-Pb,Lu-Hf,Rb-Sr和40Ar-39Ar同位素年代学研究表明,高压岩片Ⅰ的峰期变质年龄为255 Ma,高压岩片Ⅱ的主期变质作用发生在232-220 Ma,北侧构造混杂岩带的变质年龄为256 Ma.这种沿造山带横向上不同岩片的穿时性在红安-大别-苏鲁造山带高压/超高压变质岩中普遍存在,可以用同俯冲拆离/折返的构造模型来解释.不仅如此,桐柏造山带高压岩片Ⅰ的变质时间比红安造山带与之对应的高压岩片约早15 Myr,表明同一岩片在造山带纵向上可能也存在穿时性,采用翘翘板式俯冲/折返模型可以解释这种年代学差异以及华南陆块向西俯冲变浅的原因.
The high-pressure metamorphic terranes of the Tongbai orogen are mainly composed of two high-pressure lithofacies (Ⅰ and Ⅱ) and its associated greenschist facies and the blue-schist-greenschist belt in the south. Two low-temperature eclogite belts represent the two wings of the Tongbai Mountain back-tectonic structure. The high-pressure rock II is represented by the metamorphic rocks inclusions with degenerate eclogites in the Early Cretaceous gneissic granite in Tongbai Complex, The composition of the U-Pb, Lu-Hf, Rb-Sr and 40Ar-39Ar isotopes shows that the peak metamorphic age of high-pressure rock I is 255 Ma and the main period of high-pressure rock II Metamorphism occurs at 232-220 Ma, with a metamorphic age of 256 Ma on the northern side of the melange belt. This transgranularity of the different lithofacies along the orogenic belt in the Hongan-Dabie-Sulu orogenic belt Metamorphic rocks are ubiquitous and can be explained by tectonic models similar to the subduction / reentry of the subduction.In addition, the metamorphic time of the high-pressure rock slice of the Tongbai orogen is about 15 Myr earlier than the corresponding high-pressure rock mass of the Hong-An orogenic belt The same piece of rock in the orogenic belt may also exist in the longitudinal wear time, the use of seesaw Dive / reentry model can explain this difference in school and why South China’s land mass to the west of shallow subduction.