LAUSR

Abstract The volcanic zircons, inherited pre-magmatic core domains and hydrothermal zircons in felsic meta -volcanic rocks and Cu–Zn orebodies from the Neoarchean Hongtoushan deposit in China were distinguished according to their texture, 207 Pb/ 206 Pb ages, Th/U and oxygen isotopic ratios. Their respective element compositional and Lu–Hf isotopic features were studied using LA–(MC)–ICP–MS methods, showing that the compositions of the pre-magmatic core domains are intensely modified by hydrothermal processes, exhibiting no differences with hydrothermal zircons. All zircons show a linearly decreasing trend in the ZrO 2 vs SiO 2 plot, but similar REE patterns, with steep slopes, Ce and Eu anomalies and enrichments of HREE, indicating their common petrologic origin. Nevertheless, compared with volcanic zircons, pre-magmatic core domains underwent compositional modification in the hydrothermal accretion processes by P and Y substitution mechanisms. Therefore, these core domains are highly enriched in P 2 O 5 , Y 2 O 3 , REE total , and Hf 2 O as well as some incompatible elements, such as Rb, Sr, Nb, Ta and Pb, similar to the hydrothermal zircons. Moreover, the Lu/Hf ratios are elevated by almost an order of magnitude, which is associated with the addition of Lu rather than changes in Hf, leading to increased 176 Lu/ 177 Hf ratios and decoupling of Hf–O isotope systematics. Nevertheless, the hydrothermal influence on the 176 Hf/ 177 Hf ratios seems to be undetectable, rising by 0.022% when compared with the ratios of the volcanic zircons. All 176 Hf/ 177 Hf ratios plot between depleted mantle and modern known plumes suggest a mantle plume setting corresponding to the ∼2.6 Ga crustal growth in the Qingyuan district.