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A Study on nature of the basement of the Chinese Altai: Evidences from the zircon Hf-O isotopes (Vol. 40, No.5, 2020) TEXT SIZE: A A A

ZHANG Xin1, QU Zheng-gang2*

(1. College of Resources and Environment Science, Ningxia University, Yinchuan 750021, China;
2. Geological Survey Institute of Gansu Province, Lanzhou 730000, China)

Abstract: The nature of the Chinese Altai’s basement is a critical issue for understanding the tectonic evolution, magmatism, and mineralization of the Central Asian Orogenic Belt. This work reported the detailed zircon Hf-O isotopic data of three typical Paleozoic granite intrusions, including the Jertasi, Daqiaodong, and Keketuohaidong granites, from the Chinese Altai. The results show that zircon crystals commonly have inherited cores, with the U-Pb ages, εHf(t) values, and δ18O values of the inherited cores ranging from 886.1 to 1803.7 Ma, from -15.03 to 1.19, and from 10.87 to 14.78, respectively; and the U-Pb ages, εHf(t) values, and δ18O values of the recrystallized rims ranging from 392.1 to 451.9 Ma, from 1.94‰ to 6.06‰, and from 6.49‰ to 9.09‰, respectively. It is believed that the inherited cores of zircons were products of incomplete melting of the original rock, while the recrystallized rims of zircons were products of the crystallization of magma in late stage. Thus, the different Hf-O isotopic compositions of the rims and cores of zircons indicate that the studied granites were formed by the mixing of magma derived from the partial melting of old crustal materials and relatively young basaltic magma. Therefore, we considered that a Precambrian crustal basement was probably existed beneath the Chinese Altai.

Keywords: Zircon; Hf-O isotopes; granite; basement; the Chinese Altai

ACTA MINERALOGICA SINICA Vol. 40, No.5, 2020, page 529-538 

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