【91962106】Geoscience Frontiers: Integration of zircon and apatite U–Pb geochronology and geochemical 1 mapping of the 2 Wude basalts (Emeishan Large Igneous Province): a tool for a better understanding of the 3 tectonothermal and geodynamic evolution

Author:Jia-Nan Fu, Franco Pirajno, Fan Yang, Espine Shivute, Yi-Zhan Sun, Ning Ai, Kun-Feng Qiu

Abstract

Radiogenic isotopic dating and Lu–Hf isotopic composition usinglaser ablation-inductivelycoupledplasma-massspectrometry(LA-ICP-MS)oftheWudebasalt in the Yunnan province from the Emeishan large igneous province (ELIP) yielded timing of formation and post-eruption tectonothermal event. Holistic lithogeochemistry andelements mappingofbasalticrockswerefurtherreevaluatedtoprovideinsightsintocrustal contamination and formation of the ELIP. A zircon U–Pb age of 251.3 ± 2.0 Ma ofthe Wude basalt recorded the youngest volcanic eruption event and isconsistent with the age span of 251–263 Ma for the emplacement of the ELIP. Such zircons have ε_Hf(t)values ranging from –7.3 to +2.2, identical to those of magmatic zircons from the intrusive rocksof the ELIP, suggesting that crust-mantle interaction occurredduring magmatic emplacement, orcrust-mantlemixingexistedinthedeepsourceregionpriortodeepmelting.Theapatite U–Pb age at 53.6 ± 3.4 Ma records an early Eocene magmatic superimposition of aregional tectonothermal event, corresponding to the Indian–Eurasian plate collision. Negative Nb,Ta,TiandPanomaliesoftheEmeishanbasaltmayreflectcrustalcontamination.Theuneven Nb/La and Th/Ta values distribution throughout the ELIP supporteda mantle plume model origin.Therefore,theELIPwasformedasaresultofamantleplumewhichwaslater superimposedbyaregionaltectonothermaleventattributedtotheIndian–Eurasianplate collision during earlyEocene.

Keywords: Emeishan basalt; Zircon and apatite; Geochronology; Lu–Hf isotope; Early Eocene superposition; Indian–Eurasian plate collision

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