Late Mesozoic magmatism from the Daye region,eastern China: U–Pb ages,petrogenesis, and geodynamic implications |
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| Authors: | Jian-Wei Li Xin-Fu Zhao Mei-Fu Zhou Chang-Qian Ma Zorano Sérgio de Souza Paulo Vasconcelos |
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| Institution: | 1.State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan,China;2.Faculty of Earth Resources,China University of Geosciences,Wuhan,China;3.Department of Earth Sciences,The University of Hong Kong,Hong Kong SAR,China;4.Pós-Gradua??o em Geodinamica e Geofísica,Universidade Federal do Rio Grande do Norte,Natal,Brazil;5.Department of Earth Sciences,The University of Queensland,Brisbane,Australia |
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| Abstract: | Late Mesozoic dioritic and quartz dioritic plutons are widespread in the Daye region, eastern Yangtze craton, eastern China.
Detailed geochronological, geochemical, and Sr–Nd isotopic studies have been undertaken for most of these plutons, in an attempt
to provide a comprehensive understanding in the age, genesis and geodynamical control of the extensive magmatism. SHRIMP and
LA-ICP-MS zircon U–Pb dating indicate that the plutons were emplaced in the range of latest Jurassic (ca. 152 Ma) to early
Cretaceous (ca. 132 Ma), which was followed by dyke emplacement between 127 and 121 Ma and volcanism during the 130–113 Ma
interval. Both diorites and quartz diorites are sodic, metaluminous, high-K calc-alkaline, and characterized by strongly fractionated,
sub-parallel REE patterns without obvious Eu anomalies. The rocks are enriched in highly incompatible elements and large ion
lithophile elements, but depleted in high field strength elements. Samples of diorite and quartz diorite have similar Sr–Nd
isotopic compositions that are consistent with the early Cretaceous basalts and mafic intrusions throughout the eastern Yangtze
craton. The geochemical and isotopic data, together with results of geochemical modeling, indicate an enriched mantle source
for the plutonic rocks. The quartz diorites have geochemical signatures resembling adakites, such as high Al2O3 (15–19 wt.%), Sr (630–2,080 ppm), Na2O (>3.5 wt.%), negative Nb–Ta anomalies, low Y (7–19 ppm), Yb (0.5–1.8 ppm), Sc (5–15 ppm), and resultant high Sr/Y (45–200)
and La/Yb (31–63) ratios. Genesis of the adakitic quartz diorites is best explained in terms of low-pressure intracrustal
fractional crystallization of cumulates consisting of hornblende, plagioclase, K-feldspar, magnetite, and apatite from mantle-derived
dioritic magmas. Mantle-derived magmatism broadly coeval with that of the Daye region also is widespread in other regions
of the eastern Yangtze craton, reflecting large-scale melting of the lithospheric mantle during the Late Mesozoic. The large-scale
magmatism was most likely driven by lithospheric extension associated with thinning of lithospheric mantle beneath the eastern
China continent. |
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| Keywords: | Adakite Fractional crystallization Partial melting Lithospheric extension Yangtze craton Eastern China |
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