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A refractory mantle protolith in younger continental crust, east-central China: Age and composition of zircon in the Sulu ultrahigh-pressure peridotite

¹ State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China, and GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney NSW 2109, Australia
² GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney NSW 2109, Australia, and Commonwealth Scientific and Industrial Research Organisation (CSIRO) Exploration and Mining, North Ryde, NSW 2113, Australia
³ GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney NSW 2109, Australia
⁴ Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
⁵ Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA

Zircons have been extracted from garnet peridotite and its wall rock (gneiss), which was intersected by the pre–pilot hole of the Chinese Continental Scientific Drilling project (CCSD-PP1) in the Sulu ultrahigh-pressure (UHP) metamorphic belt. The peridotitic zircons record early Mesozoic UHP metamorphism (²⁰⁶Pb/²³⁸U age of 223.5 ± 7.5 Ma), but their Hf isotope compositions indicate that the protolith of the peridotite is at least Mesoproterozoic in age (minimum depleted-mantle ages [T_DM] of 1.4 Ga). Zircons from the gneiss also reflect the Mesozoic metamorphism, with a cluster of ²⁰⁶Pb/²³⁸U ages at 224.5 ± 11.5 Ma; a trail of discordant grains indicates a protolith age older than 800 Ma, consistent with T_DM model ages of younger than 1.2 Ga. The peridotitic zircons have trace-element patterns similar to kimberlitic and/or carbonatitic zircons, while those from the gneiss have affinities with zircons from syenites/monzonites. The differences suggest that the metasomatic agents that affected the peridotitic zircons were derived from the asthenospheric mantle rather than from subducted continental crust. The strong depletion of the CCSD-PP1 peridotite in basaltic components, and the relatively unradiogenic Hf isotopic compositions (e.g., –16.3 to –13.8 _Hf) of the peridotitic zircons, indicate that the peridotitic body is a fragment of refractory Archean mantle that experienced Mesoproterozoic metasomatism and represents a tectonic intrusion into younger crust.

Key Words: peridotitic zircon • Hf isotope • trace element • U-Pb dating • Sulu UHP terrane • China

This article has been cited by other articles:

				H.-Y. TANG, J.-P. ZHENG, and C.-M. YU Age and composition of the Rushan intrusive complex in the northern Sulu orogen, eastern China: petrogenesis and lithospheric mantle evolution Geological Magazine, March 1, 2009; 146(2): 199 - 215. [Abstract] [Full Text] [PDF]

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