Journal
SCIENCE IN CHINA SERIES D-EARTH SCIENCES
Volume 51, Issue 11, Pages 1545-1559Publisher
SCIENCE PRESS
DOI: 10.1007/s11430-008-0126-0
Keywords
Pengguan tectonic dome; Neoproterozoic magmatic arc; Mesozoic denudation
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Funding
- NSFC [40621002]
- MOE [IRT0546]
- National Natural Science Foundation of China [40472106]
- 111 Project [B07011]
- China Petrochemical Corporation [09-01]
- University of Hong Kong
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Neoproterozoic igneous and metamorphic complexes occur as tectonic domes in the Longmen Mountains of the western margin of the Yangtze Block, and are important in reconstructing the Rodinian supercontinent and constraining the timing and mechanism of tectonic denudational processes. The Pengguan dome consists of granitic intrusions and metamorphic rocks of the Huangshuihe Group and is tectonically overlain by ductilly deformed Sinian to Paleozoic strata. The plutonic intrusions consist of granites with abundant amphibolite enclaves. New LA-ICP-MS zircon U-Pb dating yielded an emplacement age of 809 +/- 3 Ma and a protolith age of 844 +/- 6 Ma for the granite. The granitic rocks have geochemical signatures typical of A-type granites, indicating their formation under an extensional environment, by melting of newly formed tonalite-trondhjemite-granodiorite (TTG) rocks. A detachment fault, characterized by variable ductile shear deformation of S-C fabric and ESE-ward kinematics, separates the Pengguan dome from the Sinian-Paleozoic cover. 40Ar/39Ar dating of muscovite from the mylonite in the detachment fault of the dome demonstrates that ductile deformation occurred at similar to 160 Ma. This study indicates the existence of a Neoproterozoic magmatic arc-basin system, which was denudated by a Jurassic middle crustal ductile channel flow along the Longmenshan thrust belt.
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