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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 108, NO. B2,
2127,
doi:10.1029/2001JB001726,
2003
Direct dating of left-lateral deformation along the Red River shear zone, China and Vietnam
Lisa D. Gilley
Department of Earth and Space Sciences and Institute for Geophysics and Planetary Physics,
University of California,
Los Angeles,
California,
USA
T. Mark Harrison
Department of Earth and Space Sciences and Institute for Geophysics and Planetary Physics,
University of California,
Los Angeles,
California,
USA
P. H. Leloup
Centre National de la Recherche Scientifique,
Institut de Physique du Globe de Paris,
Paris,
France
F. J. Ryerson
Institute of Geophysics and Planetary Physics,
Lawrence Livermore National. Laboratory,
Livermore,
California,
USA
Oscar M. Lovera
Department of Earth and Space Sciences and Institute for Geophysics and Planetary Physics,
University of California,
Los Angeles,
California,
USA
Jiang-Hai Wang
Guangzhou Institute of Geochemistry,
Chinese Academy of Sciences,
Guangzhou,
China
Abstract
Exposures of high-grade, midcrustal rocks within the Red River shear zone (RRSZ), which separates the Indochina and South
China blocks, exhibit clear evidence of left-lateral, ductile deformation. Assuming that the South China Sea represents a
pull-apart basin formed at the southeastern termination of the RRSZ, it has been argued that seafloor magnetic anomalies constrain
the timing of sinistral slip accommodated by the RRSZ between ∼32 and 17 Ma at a rate of ∼4 cm/yr. While 40Ar/39Ar thermochronometry indicates that left-lateral slip occurred along the RRSZ between 25 and 17 Ma, the timing of earlier
high-temperature deformation has not been directly constrained. In situ Th-Pb ion microprobe dating of monazite inclusions
in garnets allows direct assessment of the timing of amphibolite-grade metamorphism and synchronous left-lateral shearing.
Results from northern segments of the RRSZ in Yunnan, China, indicate that synkinematic garnet growth occurred between 34
and 21 Ma and are the first to document late Oligocene metamorphism and left-lateral shearing. Data from the southern RRSZ
within Vietnam are complicated by Tertiary overprinting of rocks that experienced amphibolite facies metamorphism during the
Indosinian orogeny (∼220 Ma). The period during which sinistral deformation is now constrained to have occurred along the
RRSZ (i.e., 34–17 Ma) is essentially coincident with spreading of the South China seafloor (32–17 Ma). This temporal and kinematic
link between left-lateral shearing along the RRSZ and opening of the South China Sea supports the view that Indochina was
extruded from Asia as a block along lithospheric-scale strike-slip faults.
Published 27
February
2003.
Index Terms: 1035 Geochemistry: Geochronology; 1094 Geochemistry: Instruments and techniques; 3660 Mineralogy and Petrology: Metamorphic petrology; 8110 Tectonophysics: Continental tectonics—general (0905); 9320 Information Related to Geographic Region: Asia.
Read Full Article (file size: 2988233 bytes) Cited by
Citation: Gilley, L. D., T. M. Harrison, P. H. Leloup, F. J. Ryerson, O. M. Lovera, and J. Wang
(2003),
Direct dating of left-lateral deformation along the Red River shear zone, China and Vietnam,
J. Geophys. Res.,
108(B2),
2127,
doi:10.1029/2001JB001726.
Copyright 2003 by the American Geophysical Union.
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