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Molybdenum isotopic evidence for the initiation of a big mantle wedge beneath eastern Asia.

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Title: Molybdenum isotopic evidence for the initiation of a big mantle wedge beneath eastern Asia.
Authors: Fang, Wei1 (AUTHOR), Dai, Li-Qun1,2 (AUTHOR) lqdai@ustc.edu.cn, Zhao, Zi-Fu1,2 (AUTHOR), Chen, Qi1,2 (AUTHOR), Yan, Jun3 (AUTHOR), Zhang, Dayu3 (AUTHOR), Jiang, Ding-Sheng1,2 (AUTHOR)
Source: Chemical Geology. Sep2024, Vol. 662, pN.PAG-N.PAG. 1p.
Subjects: Slabs (Structural geology), Mafic rocks, Subduction zones, Wedges, Subduction, Molybdenum, Geodynamics, Igneous rocks
Geographic Terms: Asia
Abstract: The subduction of the Paleo-Pacific plate and the formation of a big mantle wedge have influenced the tectonic-magmatic evolution of eastern Asia. However, the timing and mechanism of big mantle wedge formation remain obscure. Here we report molybdenum (Mo) isotope compositions of Mesozoic-Cenozoic mafic rocks in eastern China, which provide constraints on the geodynamics of Paleo-Pacific subduction. The >125 Ma rocks have high δ98Mo values of −0.27‰ to 0.17‰ and arc-like features, whereas the <125 Ma rocks have low δ98Mo values of −0.67‰ to −0.04‰ and ocean-island basalt (OIB)-like features. The mantle sources of these two types of rocks contain subducted Paleo-Pacific slab components at sub-arc and mantle transition zone depths, respectively. Therefore, the Paleo-Pacific subduction involves shallow subduction yielding a small mantle wedge in the early stage and deep subduction yielding a big mantle wedge in the late stage. The dramatic change in Mo isotopes reveals that the big mantle wedge beneath eastern Asia was initiated at ∼125 Ma. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The subduction of the Paleo-Pacific plate and the formation of a big mantle wedge have influenced the tectonic-magmatic evolution of eastern Asia. However, the timing and mechanism of big mantle wedge formation remain obscure. Here we report molybdenum (Mo) isotope compositions of Mesozoic-Cenozoic mafic rocks in eastern China, which provide constraints on the geodynamics of Paleo-Pacific subduction. The >125 Ma rocks have high δ98Mo values of −0.27‰ to 0.17‰ and arc-like features, whereas the <125 Ma rocks have low δ98Mo values of −0.67‰ to −0.04‰ and ocean-island basalt (OIB)-like features. The mantle sources of these two types of rocks contain subducted Paleo-Pacific slab components at sub-arc and mantle transition zone depths, respectively. Therefore, the Paleo-Pacific subduction involves shallow subduction yielding a small mantle wedge in the early stage and deep subduction yielding a big mantle wedge in the late stage. The dramatic change in Mo isotopes reveals that the big mantle wedge beneath eastern Asia was initiated at ∼125 Ma. [ABSTRACT FROM AUTHOR]
ISSN:00092541
DOI:10.1016/j.chemgeo.2024.122244