Revealing the hidden Mesozoic exhumation history of the Qinling orogenic belt, Central China: insights from multiple geochronological and geochemical data of the molasse granitic gravels
- 1State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
- 2Department of Geosciences, University of Padova, Padova 35151, Italy
- 3State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China
Qinling Orogenic Belt with its Meso-Cenozoic intracontinental orogeny and uplift, is a key physiographic element that characterized the differential evolution of the geology, geography and climate in continental China (Dong et al., 2022). However, numerous thermochronological dates of the Qinling bedrocks (Dong et al., 2011; Yang et al., 2017) show that there is a wide cooling gap between Triassic and Early Cretaceous. In this study, we studied this gap by multiple geochronology and geochemistry on Lower Cretaceous molasse granitic gravel samples, with the aim to recover the hidden Mesozoic exhumation history. We report the first detailed zircon U-Pb ages, whole-rock major and trace elements and Sr-Nd-Pb isotopic data, which suggest that these clasts derive from Late Triassic I-type granites which were emplaced in a syn-collisional setting during a subduction phase. Their provenances were also determined by comparison with the geochemical fingerprint of Qinling granitic bedrocks. New zircon and apatite U-Pb, (U-Th)/He and fission-track data, as well as biotite 40Ar-39Ar, were performed on the granitic gravels dated between ca. 222 Ma to 110 Ma. Thermal history modeling, based on the multiple geochronological data, shows rapid cooling from ca. 700 °C to 200 °C during Late Triassic-Early Jurassic, then followed by a period of slow cooling from Middle Jurassic to Early Cretaceous.
As a whole, our new multiple geochronological and geochemical data and the related thermal history modeling results provide new insights on the prolonged pre-Cenozoic cooling history as well as the intracontinental deformation of the Qinling, which were mostly related to Paleo-Tethyan subduction and Late Triassic North China-South China Block collision.
Reference:
Dong, Y., Genser, J., Neubauer, F., Zhang, G., Liu, X., Yang, Z. and Heberer, B., 2011. U-Pb and 40Ar/39Ar geochronological constraints on the exhumation history of the North Qinling terrane, China. Gondwana Research, 19(4): 881-893.
Dong, Y., Sun, S., Santosh, M., Hui, B., Sun, J., Zhang, F., Cheng, B., Yang, Z., Shi, X., He, D., Yang, L., Cheng, C., Liu, X., Zhou, X., Wang, W. and Qi, N., 2022. Cross Orogenic Belts in Central China: Implications for the tectonic and paleogeographic evolution of the East Asian continental collage. Gondwana Research, 109: 18-88.
Yang, Z., Shen, C., Ratschbacher, L., Enkelmann, E., Jonckheere, R., Wauschkuhn, B. and Dong, Y., 2017. Sichuan Basin and beyond: Eastward foreland growth of the Tibetan Plateau from an integration of Late Cretaceous-Cenozoic fission track and (U-Th)/He ages of the eastern Tibetan Plateau, Qinling, and Daba Shan. Journal of Geophysical Research: Solid Earth, 122(6): 4712-4740.
How to cite: Peng, H., Wang, J., Liu, C., Li, J., Jiao, X., Zhang, L., and Zattin, M.: Revealing the hidden Mesozoic exhumation history of the Qinling orogenic belt, Central China: insights from multiple geochronological and geochemical data of the molasse granitic gravels, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1262, https://doi.org/10.5194/egusphere-egu23-1262, 2023.
