Early Mesozoic retrograded eclogite and mafic granulite from the Badu Complex of the Cathaysia Block, South China: Petrology and tectonic implications

被引:30
作者
Zhao, Lei [1 ,2 ]
Zhai, Mingguo [1 ,3 ]
Santosh, M. [4 ,5 ]
Zhou, Xiwen [2 ]
机构
[1] Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
[2] Chinese Acad Geol Sci, Inst Geol, 26 Baiwanzhuang Rd, Beijing 100037, Peoples R China
[3] Chinese Acad Sci, Inst Geol & Geophys, Key Lab Mineral Resources, Beijing 100029, Peoples R China
[4] China Univ Geosci, Sch Earth Sci & Resources, 29 Xueyuan Rd, Beijing 100083, Peoples R China
[5] Univ Adelaide, Dept Earth Sci, Ctr Tecton Resources & Explorat, Adelaide, SA 5005, Australia
基金
中国博士后科学基金;
关键词
Retrograded eclogite; Mafic granulite; Petrology and phase equilibria; Tethyan oceanic domain; Cathaysia Block; HIGH-PRESSURE GRANULITES; U-PB GEOCHRONOLOGY; FLAT-SLAB SUBDUCTION; A-TYPE GRANITES; LU-HF ISOTOPES; NORTH CHINA; ULTRAHIGH-PRESSURE; ZIRCON GEOCHRONOLOGY; OVERTHRUST TECTONICS; CONTINENTAL-CRUST;
D O I
10.1016/j.gr.2016.10.002
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
The high-grade metamorphic terrane in the Badu region along the northeastern Cathaysia Block in South China preserves retrograded eclogites and mafic granulites. Here we present the petrology, mineral phase equilibria and P-T conditions based on pseudosection computations, as well as zircon U-Pb ages of these rocks. Mineral textures and reaction relationships suggest four metamorphic stages for the retrograded eclogite as follows: (1) eclogite facies stage (M1), (2) clinopyroxene retrograde stage (M2), (3) amphibole retrograde stage (M3), and (4) chlorite retrograde stage (M4). For the mafic granulite, three stages are identified as: (1) plagioclase-absent stage (M1), (2) granulite facies stage (M2) and (3) amphibolite facies stage (M3). Metamorphic evolution of both of the rock types follows clockwise P-T path. Conventional geothermometers and geobarometers in combination with phase equilibria modelling yield metamorphic P-T conditions for each metamorphic stage for the eclogite as 500-560 degrees C, 23-24 kbar (M1), 640-660 degrees C, 14-16 kbar (M2), 730-750 degrees C, and 11-13 kbar (M3). The chlorite retrograde stage (M4) is inferred to have occurred at lower amphibolite to greenschist facies conditions. Phase equilibria modelling of the mafic granulite shows P-T conditions for each metamorphic stage as 600-720 degrees C, >13 kbar (M1) and 860-890 degrees C, 5-6 kbar (M2) and M3 at amphibolite facies conditions. LA-ICPMS zircon U-Pb dating and trace element analysis show that the high pressure metamorphism occurred at 245-251 Ma. Protolith age of the mafic granulite is 997 Ma, similar to that of the mafic to ultramafic rocks widely distributed in the Cathaysia Block and also along the Jiangnan belt. Subduction of ancient oceanic lithospheric materials (or crustal thickening) during Mesozoic and formation of eclogites suggest that the Cathaysia Block was perhaps in the Tethyan oceanic domain at this time. The granulite formation might have been aided by Mesozoic mafic magma underplating associated with lithospheric delamination, heating and retrogression of the eclogite accompanied by rapid uplift. (C) 2016 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
引用
收藏
页码:84 / 103
页数:20
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