Scientists find reworking of juvenile crust in the late Mesozoic in North Qinling, Central China


Mesozoic granitoids, ranging from the Triassic to the Cretaceous, are widely distributed in Qinling orogen. They provide excellent clues for understanding the crustal evolution and geodynamic evolution of the orogenic belt.

Recently, a research team led by Prof. Sun Weidong from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) and Prof. Chen Fukun from University of Science and Technology of China (USTC) provided a data set comprising zircon Uranium-Lead (U-Pb) dating and elemental and Strontium-Neodymium (Sr-Nd) isotopic geochemistry for Late Mesozoic granite and microgranular enclaves (MME) exposed in the Taibai complex pluton.

The study was published in the Journal of Earth Science.

The researchers found that the granite and MME yielded concordant U-Pb zircon ages of 124 Ma to 118 Ma, indicating roughly simultaneous magmatism in the Late Mesozoic.

The granite rocks were characterized by enrichment in large ion lithophile elements, depletion in high field strength elements, and variable Sr/Y ratios of 7.64 to 63.6. “Low MgO, Cr, and Ni contents imply that the magmas were essentially crustal-derived,” said Xue Yingyu, first author of the study.

They also found that both the granite and the MME showed relative depletion in Sr-Nd isotopic composition, suggesting that the magma(s) originated from juvenile crustal rocks. These Sr-Nd isotopic characteristics were significantly different from those of other Late Mesozoic granitoids exposed elsewhere in the Qinling orogenic belt, which formed from much older and enriched sources and with negligible contributions from mantle or juvenile crust.

“We proposed a reworking event of the juvenile crust during the Late Mesozoic that was triggered by the tectonic extension and subsequent asthenospheric upwelling that occurred in eastern China,” said Prof. Sun.

More information: Ying-Yu Xue et al, Reworking of the Juvenile Crust in the Late Mesozoic in North Qinling, Central China, Journal of Earth Science (2022). DOI: 10.1007/s12583-021-1521-0
Provided by Chinese Academy of Sciences.

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