Paleoproterozoic reworking of ancient crust in the Cathaysia Block, South China： Evidence from zircon trace elements, U-Pb and Lu-Hf isotopes

• Published in: Chinese science bulletin Vol. 54; no. 9; pp. 1543 - 1554
• Main Authors: Liu, Rui, Zhou, HanWen, Zhang, Li, Zhong, ZengQiu, Zeng, Wen, Xiang, Hua, Jin, Song, Lu, XinQian, Li, ChunZhong
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science in China Press 01.05.2009
• Subjects: Articles/Geochemistry; Chemistry/Food Science; Earth Sciences; Engineering; Humanities and Social Sciences; Life Sciences; multidisciplinary; Physics; Science; Science (multidisciplinary); 古元古代; 微量元素; 铪同位素; Paleoproterozoic; Hf isotope; zircon U-Pb age; southwestern Zhejiang Province; crustal reworking
• ISSN: 1001-6538; 2095-9273; 1861-9541; 2095-9281
• DOI: 10.1007/s11434-009-0096-4

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.