Hf isotopes of the 3.8 Ga zircons in eastern Hebei Province, China: Implications for early crustal evolution of the Nort

Zircon U-Pb dating indicates that the fuchsite quartzite in eastern Hebei Province was derived from weathering and erosion of the 3.6-3.8 Ga granitic rocks. In-situ zircon Hf analyses show that the Lu-Hf isotopic system remained closed during later thermal disturbances. Zircons with concordant ages have Hf isotopic model ages of about 3.8 Ga, suggesting a recycling of this ancient crust. The ～3.8 Ga zircons have similar Hf isotopic compositions to those of chondrite, indicating that their source rocks (granitic rocks) were derived from partial melting of the juvenile crust which originated from a mantle without significant crust-mantle differentiation. Therefore, it is proposed that there was no large-scale crustal growth before ～3.8 Ga in eastern Hebei Province. Considering zircon Hf isotopic data from other areas, it is concluded that the most ancient crust in the North China Craton probably formed at about 4.0 Ga, and the possibility to find crust older than 4.0 Ga is very limited.

作 者： WU Fuyuan YANG Jinhui LIU Xiaoming LI Tiesheng XIE Liewen YANG Yueheng   作者单位： WU Fuyuan,YANG Jinhui,LI Tiesheng,XIE Liewen,YANG Yueheng(State Key Laboratory of Tectonic Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China)

LIU Xiaoming(Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China) 

刊 名： 科学通报（英文版）  SCI 英文刊名： CHINESE SCIENCE BULLETIN  年，卷(期)： 2005 50(21)  分类号： P5  关键词： Hf isotope   zircon   ancient crust   North China Craton  

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