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- Title
Geochronology and Sr-Nd-Hf isotopes of the Mesozoic granitoids from the Great Xing'an and Lesser Xing'an ranges: implications for petrogenesis and tectonic evolution in NE China.
- Authors
Hu, Xinlu; Ding, Zhenju; Yao, Shuzhen; He, Mouchun; Shen, Jun; Zhu, Bopeng; Chen, Bin
- Abstract
The Great Xing′an and Lesser Xing′an ranges are characterized by immense volumes of Mesozoic granitoids. In this study, we present major and trace element geochemistry, U-Pb geochronology and systematic Sr-Nd-Hf isotopes for the representative samples, in order to constrain their petrogenesis and the tectonic evolution in NE China. The granitoids generally have high SiO2 (66.5-78.8 wt.%) and Na2O + K2O (7.0-8.9 wt.%) contents and belong to high-K calc-alkaline to shoshonitic series. All of them show enrichment in Rb, Th, U, Pb and light rare earth elements (LREE), and depletion in Nb, Ta, P and Ti. Zircon U-Pb dating suggests that there was continuous magmatism in both the Great Xing′an Range and the Lesser Xing′an Range during the Jurassic-Early Cretaceous interval. Seven Jurassic granitoids have (87Sr/86Sr)i values of 0.704351 to 0.707374, with ϵNd(t) values of −3.4 to 2.4 and ϵHf(t) values of 0.8 to 11.3, indicating that they originated from mixed sources involving depleted mantle and pre-existing crustal components. One Early Cretaceous sample yields (87Sr/86Sr)i value of 0.706184, ϵNd(t) value of 0.6, and ϵHf(t) values of 7.0 to 8.2, which is in accordance with previous studies and indicates a major juvenile mantle source for the granitoids in this period. In the Jurassic, the magmatism in the Great Xing′an Range was induced by the subduction of the Mongol-Okhotsk Ocean, while the contemporaneous magmatism in the Lesser Xing′an Range was related to the subduction of the Palaeo-Pacific Ocean. In the Early Cretaceous, extensive magmatism in NE China was probably attributed to large-scale lithospheric delamination. Copyright © 2014 John Wiley & Sons, Ltd.
- Subjects
LESSER Khingan Range (China); STRONTIUM isotopes; NEODYMIUM isotopes; MESOZOIC Era; PETROGENESIS; GEOLOGICAL time scales; JURASSIC Period
- Publication
Geological Journal, 2016, Vol 51, Issue 1, p1
- ISSN
0072-1050
- Publication type
Article
- DOI
10.1002/gj.2576