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摘要
Many investigators emphasis that the high-pressure (HP) and ultrahigh-pressure (UHP) massif, as a key region, in the southeastern area of Dabie Shan is composed of two terranes with different metamorphic grade. And on the basis of this conclusion, the mechanism of subduction and exhumation of Dabie collision have been discussed in detail. However, up to now, the metamorphic attribution and age in the Dianqian-Siqian-Luoxi areas in the central region of Dabie Shan still are ambiguous due to lack of any researches, so that the exact architecture of Dabie collision can not be established, which disturb the understanding of the formation of Dabie collision, In this study, the detail regional metamorphic and geochronological analysis has been carried out, and the architecture of HP-UHP terrane in the southeastern area of Dabie Shan have been surveyed and analyzed. The results indicate that the HP-UHP terrane consists of two UHP and one HP units, which pile as litho-tectonic slices each other. Their P-T conditions are: (1) Unit-I: (T) over bar =723 /- 22 degrees C and (P) over bar = 3. 90 /- 0. 43GPa (diamond stability field); (2) Unit-II: (T) over bar = 630 /- 45 degrees C and (P) over bar = 3. 10 /- 0. 23GPa (coesite stability field); (3) Unit-III: (T) over bar = 545 /- 24 degrees C and (P) over bar = 2. 48 /- 0. 11GPa (quartz stability field), respectively. The zircon U-Pb age has reveal that these units have the diachronous characters and formed in different interval, their metmophic age are 226.4 /- 2. 6Ma -> 230.1 /- 3. 5Ma -> 235. 2 /- 4. 2Ma (Xu et al., 2013) from Unit-I, II to Unit-III, respectively. In spatial distribution, the general metamorphic grade decrease and metamorphic age increase from north to south respectively. Due to erosion, the Unit-I in MalongShima area occur as tectonic window, which result in the abruption of P-T conditions.
- 出版日期2013-5
- 单位合肥工业大学; 江苏省地质调查研究院
