High-pressure mafic granulites in the Trans-North China Orogen: Tectonic significance and age |
| |
| Authors: | Jian Zhang Guochun Zhao Min Sun Simon A Wilde Sanzhong Li Shuwen Liu |
| |
| Institution: | aDepartment of Earth Sciences, James Lee Science Building, The University of Hong Kong, Pokfulam Road, Hong Kong, China;bDepartment of Applied Geology, Curtin University of Technology, Bentley 6102, Western Australia;cCollege of Marine Geosciences, Ocean University of China, 266003, Qingdao, China;dSchool of Earth and Space Sciences, Peking University, Beijing 100871, China |
| |
| Abstract: | High-pressure mafic granulites (including retrograded eclogites) have been reported from the Trans-North China Orogen, a Paleoproterozoic orogenic belt along which two discrete continental blocks, referred to as the Eastern and Western Blocks, were amalgamated to form the North China Craton. Extensive metamorphic investigations and geochronology carried out over the last few years provide important insights into the age and significance of these high-pressure granulites, which are critical in understanding of the timing and tectonic processes involved in the assembly of the North China Craton.Most high-pressure mafic granulites in the Trans-North China Orogen preserve the high-pressure granulite facies assemblage garnet + plagioclase + clinopyroxene + quartz, the medium-pressure granulite facies assemblage garnet + plagioclase + clinopyroxene + orthopyroxene ± quartz, the low-pressure granulite facies assemblage orthopyroxene + clinopyroxene + plagioclase ± quartz, and the amphibolite facies assemblage hornblende + plagioclase. Minor high-pressure granulites preserve the early eclogite facies mineral assemblage of garnet + quartz + omphacite pseudomorph (clinopyroxene + Na-rich plagioclase), indicating that they are retrograded eclogites. These mineral assemblages and their P–T estimates define a clockwise P–T path involving near-isothermal decompression and cooling following the peak high-pressure metamorphism, which suggests that they formed during continent–continent collision. Field mapping and geochronology indicate that the precursors of these high-pressure granulites were mafic dykes which were emplaced at  1915 Ma and underwent high-pressure granulite facies metamorphism at 1.85 Ga. Taken together, the high-pressure granulites in the Trans-North China are considered to have resulted from final collision between the Eastern and Western Blocks to form the North China Craton at 1.85 Ga, not at 2.5 Ga as recently proposed by some authors. |
| |
| Keywords: | High-pressure granulite Trans-North China Orogen P– T paths North China Craton Paleoproterozoic tectonics |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
