Artigo Revisado por pares

Late Paleoproterozoic to Early Mesoproterozoic Mafic Magmatism in the SW Yangtze Block: Mantle Plumes Associated With Nuna Breakup?

2020; Wiley; Volume: 125; Issue: 7 Linguagem: Inglês

10.1029/2019jb019260

ISSN

2169-9356

Autores

Gui‐Mei Lu, Wei Wang, Peter A. Cawood, Richard E. Ernst, Massimo Raveggi, Si‐Fang Huang, Er‐Kun Xue,

Tópico(s)

Geochemistry and Geologic Mapping

Resumo

Abstract Numerous late Paleoproterozoic to early Mesoproterozoic mafic magmatic rocks are exposed in the southwestern Yangtze Block, corresponding to early breakup of the Nuna supercontinent. Geochronological data reveal three episodes of mafic magmatism at ~1,740, 1,700, and 1,500 Ma. The two older generations have MORB‐like Nb/Ta ratios and superchondritic Nd‐Hf isotopes, indicating that they were likely derived from partial melting of asthenospheric mantle. In contrast, the ~1,500 Ma mafic rocks possess OIB‐like Nb/Ta (16.7–19.1) and Zr/Hf (41.0–45.1) ratios, ε Nd ( t ) values (−0.8 to +0.1), and ε Hf ( t ) values (−3.3 to +8.4), suggesting that they originated from a mantle plume. These three pulses of mafic magmatic activity in the Yangtze Block have geochemical features (such as TiO 2 contents, Nb/Y, and La/Yb values), similar to coeval mafic rocks in Siberia and Laurentia, consistent with detrital zircon provenance studies, which show a spatial linkage of the Yangtze Block with northern Laurentia in the Nuna configuration. Taking all synchronous mafic magmatism into account, a mantle plume beneath southern Siberia was considered to be initiated at ~1,750 Ma forming a broad region of mafic magmatism that extended into the Yangtze Block as well as beneath northern Laurentia and resulted in lithospheric extension. The Yangtze Block was possibly the nearest neighbor to northwestern Siberia at ~1,500 Ma and subsequently drifted from the Nuna supercontinent induced by the ~1,500 Ma Kuonamka mantle plume, heralding a period of limited magmatic activity and tectonic quiescence in the Yangtze Block that extended throughout the remainder of the Mesoproterozoic.

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