Geochronology and Sr-Nd-Pb-Hf isotopic geochemistry of middle-late Permian granitic and volcanic rocks within the eastern margin of the Khanka Massif: petrogenesis and implications for the tectonic nature

ABSTRACT

The Khanka Massif forms the easternmost part of the Central Asian Orogenic Belt (CAOB) and represents an ideal location for examination of the timing and processes involved in the transition from the Palaeo-Asian to Palaeo-Pacific Ocean tectonic systems. However, it is obstructed because the late Palaeozoic tectonic attributes of the eastern margin of this massif remain unclear. In this paper, we provide zircon U-Pb ages and Hf isotopic, as well as the whole-rock Sr-Nd-Pb-Hf isotopic data for Permian granitic and volcanic rocks within the eastern margin of the Khanka Massif, with the aim of exploring the petrogenesis and their geodynamics significance. These data suggest that the Permian magmatism within the eastern margin of the Khanka Massif, composed of monzogranites and rhyolites, can be split into two stages; i.e. middle (ca. 264 to ca. 263 Ma) and late (ca. 252 Ma) Permian. The highly fractionated middle Permian monzogranites are formed in an N-S extensional setting and represent the magmatic response to the amalgamation of the Khanka and Jiamusi massifs. Middle-late Permian rhyolites with decoupled Nd-Hf isotopic compositions were derived from partial melting of metasedimentary crustal rocks. Their moderate-high zircon saturation temperatures (796–817°C) are thought to represent the involvement of ridge subduction of the Palaeo-Asian Ocean beneath the western margin of the Khanka Massif. Our findings further reinforce the existence of the ridge subduction of the Palaeo-Asian Ocean at the western margin of Khanka Massif in the Permian, while excluding the possibility of Permian Palaeo-Pacific oceanic plate subduction occurred beneath the eastern margin of the Khanka Massif in the Permian.

KEYWORDS:

• Central Asian Orogenic Belt
• Khanka Massif
• Permian
• tectonic nature
• zircon U-Pb dating
• Sr-Nd-Pb-Hf isotopes

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (Grants 42022013) and Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (Grant GML2019ZD0202).

Research Highlight

• Permian felsic rocks were identified in the eastern margin of Khanka Massif.

• P₂ monzogranite was related to the collision of Khanka-Jiamusi massifs in the north.

• P_2-3 rhyolites were related to the ridge-subduction in the west.

• The subduction of Palaeo-Pacific plate was excluded in the Permian.

Disclosure statement

No potential conflict of interest was reported by the author(s).

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Funding

This work was financially supported by the National Natural Science Foundation of China (Grants 42022013) and the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (Grant GML2019ZD0202).