東亞地體構造演化整合研究計畫(I)─(總計畫及子計畫三)紅河－哀牢山斷裂帶附近地區熱事件及地塊運動研究(III)
Other Title
Cenozoic Thermal Events and Block Movements along the
Ailaoshan – Red River Fault Zone (III)
Ailaoshan – Red River Fault Zone (III)
Date Issued
2000
Date
2000
Author(s)
DOI
892116M002017
Abstract
Paleogene southeastward extrusion of the
Indochinese block with respect to the South China
block transported some basement complexes from
eastern Tibet to northern Vietnam in accommodating
the India-Asian continental collision. One of those
transported basement complexes, the Posen complex
in northern Vietnam, was studied
thermochronologically by U-Pb and 40 Ar/39 Ar methods.
Zircon U-Pb dating yields an upper intercept date of
885 ± 96 Ma, corresponding to the emplacement age
of the protolith and a lower intercept age of 490 ± 66
Ma, which may indicate a thermal event in early Paleozoic age. 40 Ar/39 Ar results for micas and K-feldspars
in the range of 30 to 36 Ma suggest a rapid
cooling and exhumation history of the Posen complex during the Paleogene. The time span for
exhumation/cooling recorded in the Posen complex is
surprisingly coincident with the earlier stage of the
rapid uplifting (40 to 30 Ma) in the eastern Tibetan
plateau, but clearly older than the age range for the
left-lateral shearing of the Ailao Shan-Red River (ASRR) shear zone (27-17 Ma). Given the fact that
the Indochinese block was once attached to eastern
Tibet in SW China prior to the extrusion, the present
results would not only be a good constraint for the
early rapid uplifting of the eastern Tibet during the
Paleogene, but also provide an independent evidence
for the initiation for the left-lateral movement along the ASRR shear zone.
Subjects
eastern Tibet
U-Pb dating
39 Ar-40 Ar
dating
dating
thermochronolog
Publisher
臺北市：國立臺灣大學地質科學系暨研究所
Type
report
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