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Petrogenesis of the Late Mesozoic gabbros in the eastern Jiangnan Orogen, South China: Characteristics of the lithospheric mantle
Author(s) -
Wang Sinuo,
Yan Jun,
Li Quanzhong,
Liu Jianmin,
Xie Jiancheng,
Yang Chao
Publication year - 2021
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3964
Subject(s) - geology , geochemistry , mafic , petrogenesis , zircon , mantle (geology) , pluton , fractional crystallization (geology) , felsic , petrology , peridotite , gabbro , basalt , tectonics , paleontology
As we know, mantle‐derived mafic rocks can be used to effectively trace the nature of the mantle source and constrain the regional tectonic setting and evolution. Recently, a Late Mesozoic mafic intrusive body (Huangmao pluton) has been found in the eastern Jiangnan Orogen (EJO). In this study, we investigate this pluton using petrography, whole‐rock geochemistry, Sr–Nd–Pb isotopes, and geochronology. The Huangmao pluton is primarily composed of a fine‐grained gabbro‐diabase, which is characterized by consistent SiO 2 , MgO, Fe 2 O 3 T , and TiO 2 contents. These gabbros exhibit continental crust‐like trace element signatures, i.e., enriched in large‐ion lithophile elements (LILE), Pb, and light rare earth elements (LREE), but depleted in high‐field‐strength elements (HFSE). In addition, the Huangmao gabbros have moderate initial 87 Sr/ 86 Sr ratio (0.7065–0.7080) and slightly negative to weakly positive ε Nd ( t ) value (−2.06 to +0.84). Finally, U–Pb zircon dating confirms that the Huangmao pluton was emplaced in the Late Jurassic (152.6 ± 3.1 Ma). Through an integrated geochemical analysis, these Late Mesozoic gabbros were genetically originated from an enriched lithospheric mantle source, which formed by a metasomatic reaction between mantle peridotite and sediment‐derived felsic melt. Consequently, the lithologies of the metasomatite were predominantly pyroxenites with a small amount of pyroxene‐rich peridotites. Considering the large distance between the modern trench and the EJO, the flat‐slab subduction and rollback model of the palaeo‐Pacific Plate is the most reasonable interpretation of the geodynamic setting that resulted in Late Mesozoic magmatism in the EJO.