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Cenozoic deformation-metamorphic evolution of the Diancang Shan metamorphic complex and regional tectonic implications

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Authors:Zhao Chunqiang; Zhao Li; Cao Shuyun; Liu Junlai
Author Affiliations:Primary:
China University of Geosciences, State Key Laboratory of Geological Processes and Mineral Resources, Beijing, China
Volume Title:Yanshi Xuebao Acta Petrologica Sinica
Source:Yanshi Xuebao = Acta Petrologica Sinica, 30(3), p.851-866. Publisher: Science Press, Beijing, China. ISSN: 1000-0569
Publication Date:2014
Note:In Chinese with English summary. 53 refs.; illus., incl. 2 tables, geol. sketch maps
Summary:The Diancang Mountain complex is one of four metamorphic complexes along the Ailao Shan-Red River (ASRR) ductile shear zone. The complex experienced a long-term history of multiple deformations and metamorphisms during its tectonic evolution since the Proterozoic. By focusing on the Cenozoic deformation-metamorphic evolution, this paper mainly examines high-grade metamorphic aluminous rocks (sillimanite-garnet-biotite gneiss) and a fine-grained granite intruding the high-grade metamorphic rocks. Through a microstructural analysis and paragenetic association study, an upper amphibolite facies assemblage of garnet+sillimanite+K-feldspar+biotite+plagioclase±quartz and a lower pressure amphibolite facies assemblage of sillimanite+muscovite+biotite+quartz were recognized in the high-grade metamorphic aluminous rocks. SHRIMP U-Pb dating of metamorphic zircons from the high-grade gneiss reveals the Cenozoic growth of zircons during three stages of metamorphism at 54.2±1.7Ma, 31.5±1.5Ma, and 27.5±1.2Ma. At the same time, a mylonitized fine-grained granite hosted in the high-grade metamorphic rocks was studied macro- and microscopically to constrain the metamorphism timing and shear deformation of the high-grade gneisses, and therefore the shearing along the ASRR shear zone. LA-ICP-MS U-Pb dating of magmatic zircons gives an age of 24.4±0.89Ma, which represents the magmatic crystallization of syn-shearing granite. Based on the apparent age populations of metamorphic zircons in the high-grade gneiss, we find that the metamorphic rocks from the Diancang Mountains have multiple stages of Cenozoic thermal-tectonic evolution attributed to the Indian-Eurasian plate convergence and collision (54 Ma), post-collisional extension (43-30 Ma), and large-scale left-lateral shearing along the Ailao Shan-Red River shear zone (27-21 Ma).
Subjects:Amphibolite facies; Cenozoic; Deformation; Facies; Faults; High-grade metamorphism; Lateral faults; Left-lateral faults; Metamorphic core complexes; Metamorphic rocks; Metamorphism; Mineral assemblages; Neotectonics; Polyphase processes; Shear zones; Tectonics; Ailao Shan; Asia; China; Far East; Yunnan China; Ailao Shan-Red River ductile shear zone; Diancang Shan metamorphic complex
Coordinates:N260000 N260000 E0995000 E0995000
Record ID:767691-23
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute.
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