SHRIMP ziron U-Pb geochronology of early Mesozoic felsic igneous rocks from the southern Lancangjiang and its tectonic implications |
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Authors: | Peng Touping Wang Yuejun Fan Weiming Liu Dunyi Shi Yuruo and Miao Laicheng |
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Institution: | (1) Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China;(2) Graduate University of Chinese Academy of Sciences, Beijing, 100039, China;(3) SHRIMP isotope Laboratory, Chinese Academy of Geological Sciences, Beijing, 100037, China;(4) Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China |
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Abstract: | The SHRIMP zircon U-Pb geochronology of three typical samples, including two monzonitic granites from the Lincang batholith
and a rhyolite from the Manghuai Formation are presented in the southern Lancangjiang, western Yunnan Province. The analyses
of zircons for the biotite monzonitic granites from the northern (02DX-137) and southern (20JH-10) Lincang batholith show
the single and tight clusters on the concordia, and yield the weighted mean 206Pb/238U ages of 229.4 ± 3.0 Ma and 230.4 ± 3.6 Ma, respectively, representing the crystallized ages of these granites. The zircons
for the rhyolitic sample (02DX-95) from the Manghuai Formation give a weighted mean 206Pb/238U age of 231.0 ± 5.0 Ma. These data suggest that the igneous rocks from the Lincang granitic batholith and Manghuai Formation
have a similar crystallized age. In combination with other data, it is inferred that both were generated at a narrow age span
(∼230 Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/238U apparent age of 1977±44 Ma is additionally obtained from one zircon from the biotite monzonitic granite (southern Lincang
batholith), indicative of development of the early Proterozoic Yangtze basement in the region. These precisely geochronological
data provide important constraints on better understanding the Paleozoic tectonic evolution of the Tethys, western Yunnan
Province. |
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Keywords: | SHRIMP zircon U-Pb dating Middle Triassic Lincang granitic batholith Manghuai Formation rhyolite southern Lancangjiang |
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