| U-Pb zircon geochronology and Hf isotope study of metamorphosed basic-ultrabasic rocks from metamorphic basement in southwestern Zhejiang:The response of the Cathaysia Block to Indosinian orogenic event |
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| 摘 要： | A combined study using LA-ICP-MS U-Pb dating, Hf isotopes, trace elements and the Ti-in-zircon geo-thermometer was carried out on zircons from the metamorphosed basic-ultrabasic rocks in the meta-morphic basement of the Cathaysia Block, southwestern Zhejiang Province. The formation and meta-morphic ages of the rocks from the metamorphic basement of the Cathaysia Block were determined based on zircon U-Pb geochronology. The age for the magmatic crystalline zircons from the protolith is about 1.85 Ga. The εHf(t) values of the older zircons were from ?7 to ?3, with two-stage model Hf ages (TDM2LC) of about 2.9 to 3.4 Ga, indicating that the source material was derived from anatexis and recy-cling of the Archean crust. The newly formed metamorphic zircons yielded U-Pb ages of 260―230 Ma. The metamorphic temperature calculated using the Ti-in-zircon geothermometer ranged from 610 to 720℃, consistent with the results from petrographic observations, indicating that the Cathaysia Block experienced an amphibolite facies metamorphism during the Indosinian. Results from this study pro-vided an important timeframe for the tectonic evolution in South China and the Southeast Asia during the Late Permian and Early Triassic times.
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U-Pb zircon geochronology and Hf isotope study of metamorphosed basic-ultrabasic rocks from metamorphic basement in southwestern Zhejiang: The response of the Cathaysia Block to Indosinian orogenic event |
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| Authors: | Hua Xiang Li Zhang HanWen Zhou ZengQiu Zhong Wen Zeng Rui Liu and Song Jin |
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| Institution: | (1) State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, China;(2) State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, 710069, China |
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| Abstract: | A combined study using LA-ICP-MS U-Pb dating, Hf isotopes, trace elements and the Ti-in-zircon geothermometer was carried
out on zircons from the metamorphosed basic-ultrabasic rocks in the metamorphic basement of the Cathaysia Block, southwestern
Zhejiang Province. The formation and metamorphic ages of the rocks from the metamorphic basement of the Cathaysia Block were
determined based on zircon U-Pb geochronology. The age for the magmatic crystalline zircons from the protolith is about 1.85
Ga. The ε
Hf
(t) values of the older zircons were from −7 to −3, with two-stage model Hf ages (T
DM2LC) of about 2.9 to 3.4 Ga, indicating that the source material was derived from anatexis and recycling of the Archean crust.
The newly formed metamorphic zircons yielded U-Pb ages of 260–230 Ma. The metamorphic temperature calculated using the Ti-in-zircon
geothermometer ranged from 610 to 720°C, consistent with the results from petrographic observations, indicating that the Cathaysia
Block experienced an amphibolite facies metamorphism during the Indosinian. Results from this study provided an important
timeframe for the tectonic evolution in South China and the Southeast Asia during the Late Permian and Early Triassic times.
Supported by the National Natural Science Foundation of China (Grant No. 40372094), the Opening Foundation of State Key Laboratory
of Continental Dynamics, Northwest University (Grant No. 06LCD12) and the project of Land and Resources Bureau of Zhejiang
Province (Grant No. 2004005) |
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| Keywords: | U-Pb dating Hf isotopes Ti-in-zircon geothermometer Indosinian orogenics southwestern Zhejiang Province |
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