| Rb—Sr and U—Pb Dating of the Daguzhai and Luobuli Granitic Massifs in South China |
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| 摘 要： |
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| 关 键 词： | 铷－锶年代学 铀－铅年代学 花岗岩 华南地区 同位素 火成岩 |
Rb-Sr and U-Pb dating of the Daguzhai and Luobuli granitic massifs in South China |
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| Authors: | Yongfei Zheng Weizhou Shen Guoqing Xu Zuhuan Zhang |
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| Institution: | (1) Department of Earth Sciences, Nanjing University, 210008 Nanjing;(2) Beijing Institute of Uranium Geology, 100029 Beijing;(3) Geochemical Institute, University of Gottingen, Goldschmidtstrasse 1, D 3400 Gottingen, Germany |
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| Abstract: | Rb-Sr and U-Pb isotopic studies of the two contrasting granite types of the Daguzhai and Luobuli massifs in South China provide
new constraints on the interpretation of isotopic age data for plutonic igneous rocks. A Rb-Sr internal isochron age of 146±7Ma
for the Luobuli adamellite is interpreted to represent the age of magma crystallization, whereas the whole rock Rb- Sr isochron
yields an older apparent age of 161±10Ma which is regarded as resulting from contamination processes affecting the petrogenesis
of this adamellite. In the Daguzhai granite the marked scatter of whole- rock Rb-Sr data in isochron diagram is ascribed to
the open system behavior of Rb during postmagmatic autometasomatism. Uniformity of initial87Sr /86Sr ratio in this granite is indicated in a plot of87Sr versus86Sr. The autometasomatism has also affected zircon U-Pb system, resulting in a spread of data along the concordia curve between
165 and 125Ma. This spread is regarded as indicating the duration of the autometasomatism. |
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