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ABSTRACT
The petrogenesis and tectonic affinity of late Mesoproterozoic to early Neoproterozoic magmatic records in the Yangtze Block is important to understand its tectonic evolution within the context of the Rodinia supercontinent’s reconstruction. In this paper, our new SHRIMP zircon U-Pb dating results demonstrate that the Luonie granodiorites and Gonghe granites were emplaced at 1019.2 ± 5.3 Ma and 925.0 ± 4.9 Ma, respectively. The Luonie granodiorites show high HFSE and HREE contents and Ga/Al ratios, resembling A-type granites. They exhibit negative εHf(t) values (−1.6 to −3.9) with TDM2 ages of 1980–2125 Ma, suggesting that they were derived from partial melting of pre-existing continental crust. The Gonghe granites are calc-alkaline, slightly peraluminous and have low P2O5 contents, which are typical features of I-type granites. Zircons from Gonghe granites possess positive εHf(t) values (+10.8 to +13.1) with TDM2 ages of 969–1113 Ma, indicating juvenile mafic lower crust source. In conclusion, Luonie granodiorites were formed in an intra-plate rifting environment, whereas Gonghe arc-related intrusion was emplaced into an arc-setting. On the basis of these results, we propose that the rifting-related igneous rocks and subduction-related magmatism in the southwestern Yangtze Block record a tectonic transition from a continental-rifting basin in the passive plate margin to a collisional setting in an active continental margin in the early Neoproterozoic.
Acknowledgments
This research was financially supported by the Geological Survey Projects of China Geological Survey (Nos DD20190370 and 121201111120117).
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary material
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