Paleoproterozoic reworking of ancient crust in the Cathaysia Block, South China: Evidence from zircon trace elements, U-Pb and Lu-Hf isotopes |
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Authors: | Rui Liu HanWen Zhou Li Zhang ZengQiu Zhong Wen Zeng Hua Xiang Song Jin XinQian Lu ChunZhong Li |
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Affiliation: | (1) State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences (Wuhan), Wuhan, 430074, China;(2) State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, 710069, China;(3) The 7th Geological Team of Zhejiang Province, Lishui, 323000, China |
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Abstract: | A combined study of zircon LA-ICP-MS U-Pb dating, trace elements and Hf isotope was carried out for gneissic granite from
the Sanzhishu area in Jingning, SW Zhejiang Province. Nearly all the zircons separated from the granite exhibited oscillatory
zoning and high Th/U ratios (>0.1). The REE profile showed a pronounced positive Ce anomaly, negative Eu anomaly and an enrichment
of HREE, which are typical characteristics of magmatic zircon. Thirteen concordant or nearly concordant analytical data yielded
a weighted mean 207Pb/206Pb age of 1860±13 Ma (MSWD=0.084), representing the formation age of the granite. The magmatic zircons had negative εHf(t)
values of −15.6 to −10.0 and two-stage Hf model ages of 3.1 to 3.4 Ga, indicating that the granites were formed by reworking
of ancient crust. The major- and trace-element data indicate that the gneissic granites are metaluminous high-K calc-alkaline
rocks and exhibit the same geochemical characteristics as aluminous A-type granites, implying the emplacement of the granite
in a post-orogenic extensional tectonic setting. We conclude that the Paleoproterozoic crustal reworking event in the Cathaysia
Block of South China marked the transition from assembly to break-up of the Columbia supercontinent.
Supported by National Natural Science Foundation of China (Grant No. 40873004), Special Funds for National Scientific Research
of Commonweal Industries, the Ministry of Land and Resources of China (Grant No. 2008110015), 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: | zircon U-Pb age Hf isotope Paleoproterozoic crustal reworking southwestern Zhejiang Province |
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