Geochrology, Geochemistry of Volcanic-Intrusive Rocks in the Ningwu Basin and Its Geological Implications
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    Abstract:

    This study presents the accurate zircon dating results, Hf isotopic compositions and major-trace element analysis for typical volcanic rocks and intrusive rocks related to Fe and Cu deposits during four volcanism periods in the Ningwu basin. LA-ICP-MS zircon dating results indicates that the volcanic rocks in the Longwangshan, Dawangshan and Gushan formations formed at 134~127 Ma,while the volcanic rock in the Niangniangshan Formation has a younger crystallization age at 118.8±1.6 Ma. A mafic porphyry has an age of 130.6±1.3 Ma, and three moderate-felsic porphyry formed at 124~128 Ma. Zircons from the volcanic rocks and intrusive rocks in the Longwangshan, Dawangshan and Gushan Formations have similar Hf isotopic characteristics, with εHf(t) values of -2~-5, suggesting similar magmatic sources, while the volcanic rocks from the Niangniangshan Formation have zircons with higher εHf(t), suggesting more mantle-derived materials involved in the source . Combing the geochemistry characteristics, it is suggested that these magmatic rocks were derived from an enriched mantle. The fluid/melt in mantle metasomatism could be related to an older subduction event, while the continent-sourced materials were carried in deep mantel by the oceanic plate as oceanic sediments. Similar formation time, geochemistry and Hf isotopic compositions between intrusive rocks and coeval volcanic rocks indicate that they were derived from similar source with different phases. The magmatism in the Ningwu basin was produced from the remelting of enriched mantle at the tectonic setting of lithosphere thinning in eastern China.

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WANG Lijuan, WANG Rucheng, YU Jinhai, YANG Yinghe, HUANG Jianping, ZHANG Shaoqin.2014. Geochrology, Geochemistry of Volcanic-Intrusive Rocks in the Ningwu Basin and Its Geological Implications[J]. Acta Geologica Sinica,88(7):1247-1272

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History
  • Received:May 22,2013
  • Revised:December 11,2013
  • Adopted:December 12,2013
  • Online: July 16,2014
  • Published: