Petrogenesis of the Mesozoic magmatic rocks in Zijinshan area:constraints from zircon Hf isotope evidence
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    Abstract:

    Zircon in-situ Lu-Hf isotopic analysis of the Mesozoic magmatic rocks in Zijinshan area was carried out by using the laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to reveal their protolith origin. The results show that Middle-Late Jurassic and Early Cretaceous magmatic rocks have different Hf isotopic compositions, suggesting that they originated from different sources. The Middle-Late Jurassic granites exhibit obviously negative εHf(t) values from -13.5 to -2.9, with the peak values of two-stage model ages (tDMC) ranging from 1.7 to 2.0 Ga, indicating that the magma was mainly sourced from the partial melting of Paleoproterozoic basement. The Early Cretaceous intrusive-volcanic rocks include Sifang granodiorite, Zijinshan, Yueyang and Wenwu volcanic rocks. The Sifang granodiorite and Zijinshan volcanic rocks have similar zircon Hf isotopic compositions, with a wide range of εHf(t) values (-2.3~0.4 and -8.9~5.6) and two-stage model ages (1.3~1.4 Ga and 1.1~1.5 Ga), suggesting that they originated from the same source, with the mixing of partial melting of the Mesoproterozoic basement and mantle-derived melts. The negative εHf(t) values from -2.7 to -9.6 and two-stage model ages ranging from 1.4 to 1.7 Ga of Yueyang and Wenwu volcanic rocks indicate that they were derived from partial melting of the Meso-Paleoproterozoic basement with minor mantle components. It is held that the Early Cretaceous intrusive-volcanic rocks of Zijinshan area were derived from the same magma source, and the evolution of magma source with continuous variation of components and compositional content reveals a complex crust-mantle interaction. Therefore, the difference of Hf isotopic compositions between the Middle-Late Jurassic and Early Cretaceous magmatic rocks could be attributed to different magma sources, and these rocks were produced at different stages of the paleo-Pacific Plate subduction beneath the Eurasian continent.

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梁清玲,江思宏,王少怀,刘翼飞,白大明,陈春良,2013,福建紫金山地区中生代岩浆岩成因——锆石Hf同位素证据[J].岩石矿物学杂志,32(3):318~328. LIANG Qing-ling, JIANG Si-hong, WANG Shao-huai, LIU Yi-fei, BAI Da-ming, CHEN Chun-liang,2013,Petrogenesis of the Mesozoic magmatic rocks in Zijinshan area:constraints from zircon Hf isotope evidence[J]. Acta Petrologica et Mineralogica,32(3):318~328.

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  • Received:December 04,2012
  • Revised:March 18,2013
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