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Episodic magmatism and crustal reworking in the Kunyang area during Rodinia Breakup: Evidence from zircon and rutile U-Pb-Hf isotopes
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DOI：10.1016/j.precamres.2026.108089.png)
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Abstract
En 中文
The Yangtze Block, as a critical constituent of the Rodinia supercontinent, records a Neoproterozoic tectono-magmatic evolution that holds fundamental implications for deciphering supercontinent breakup processes. This study investigates the phosphorite-bearing rocks of the Meishucun and Qiongzhusi Formations from the Kunyang mining area in the southwestern Yangtze Block. Through integrated petrography, zircon U-Pb geochronology, rutile U-Pb geochronology, and zircon Lu-Hf isotopic analysis, we constrain provenance characteristics and explore their genetic affinity with Rodinia disintegration. The results demonstrate that all samples exhibit comparable zircon U-Pb age populations. The most ancient zircons yield ages of similar to 3.3 Ga, whereas Neoarchean-Paleoproterozoic age clusters are centered at similar to 2699-2494 Ma and similar to 1863-1858 Ma. Synthesizing these data with previously published petrological and geochronological investigations substantiates the widespread occurrence of ancient crystalline basement beneath the Yangtze Block. Metamorphic rutile U-Pb ages of similar to 773-765 Ma closely follow the peak of magmatic activity recorded by zircons at similar to 799 Ma, together reflecting successive metamorphic and magmatic responses during the same intense tectono-thermal event in the early Neoproterozoic. The study area experienced at least three episodic Neoproterozoic magmatic pulses at similar to 818-799 Ma, similar to 748 Ma, and similar to 658 Ma, which constitute a prolonged, multi-stage extensional sequence and record the tectonic response of the Yangtze Block to the breakup of the Rodinia supercontinent. Zircon Lu-Hf isotopes indicate early Neoproterozoic magmas were derived primarily from the remelting of Paleoproterozoic ancient crust (epsilon(Hf)(t) = -13.98--0.03, T-DM(2) = 2.3-1.6 Ga), with a minor contribution from late Mesoproterozoic juvenile components (epsilon(Hf)(t) = 0.90-9.32, T-DM(2) = 1.3-1.0 Ga). Integrated studies suggest that this prolonged, episodic magmatism may have been driven by the combined effects of lithospheric extension in a subduction-related setting and thermal perturbation from mantle plume activity.
Keywords:
Rodinia supercontinent
Yangtze Block
Kunyang
Phosphate
Zircon U-Pb-Hfisotopes
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