Insight of enriched basalts into the nature and evolution of mantle lithosphere beneath craton margins

Refractory lithospheric deep roots are the cornerstone for the prolonged stability of cratons and mantle xenoliths are normally the key targets for study on the evolution of such deep roots. In regions with few mantle xenoliths discovered, the basalts enriched in radiogenic isotopic compositions due to marked lithospheric mantle contribution are crucial to unmask the lithospheric mantle evolution based on comprehensive study involving petrology, geochemistry and thermodynamic modelling. Here, the Early Cretaceous basaltic suites from the northwest North China Craton are taken as an example to show the significance of enriched basalts on the study of lithospheric mantle. These basalts with few mantle xenoliths are characterized by high silica and alkali contents (SiO₂ = 45.8 – 59.8 wt.%, K₂O+Na₂O = 4.81 – 9.88 wt.%), arc-type trace-element patterns and enriched radiogenic isotope compositions (e.g., εNd = -2.64 – -12.88, ⁸⁷Sr/⁸⁶Sr = 0.7063 – 0.7093). The TiO₂ and Fe₂O₃ (total) contents are higher than those of natural and experimental melts from refractory mantle peridotite but comparable to those of partial melts of fertile mantle rocks. The high contents of fluid-loving elements are suggestive of source metasomatism by aqueous fluids. Combined with thermodynamic modelling and regional tectonic history, these enriched basalts likely record concurrent melting of the asthenosphere and hydrated fertile lithospheric lower boundary. The inferred lithospheric mantle contrasts with the coeval thick and refractory one supporting the eastern NCC, and highlights that the craton destruction, especially the loss of its ancient refractory mantle root, should take place in a diachronous manner related to the craton-girded subduction episodes. Our study illustrates the potential of enriched basalts to recover the nature and evolution of mantle lithosphere beneath craton margins and associated tectonic histories.

Related papers:

1. Dai, H.-K., Zheng, J.-P., Xiong, Q., Hu, L.-L, & Zhou, X. (2024). Insight of enriched basalts into the nature and evolution of mantle lithosphere beneath craton margins. Science China Earth Sciences, 67, 3128–3142.

2. Dai, H.-K., Zheng, J.-P., Xiong, Q., Griffin, W. L., & O’Reilly, S. Y. (2023). Continental thermal blanketing explains the compositional dichotomy of the diffuse basaltic province across central-eastern Asia. Geophysical Research Letters, 50, e2023GL104951.

3. Dai, H.-K., Oliveira, B., Zheng, J.-P., Griffin, W. L., Afonso, J. C., Xiong, Q., & O'Reilly, S. Y. (2021). Melting dynamics of Late Cretaceous lamprophyres in central Asia suggest a mechanism to explain many continental intraplate basaltic suite magmatic provinces. Journal of Geophysical Research: Solid Earth, 126, e2021JB021663.

4. Dai, H.-K., Zheng, J.-P., Xiong, Q., O'Reilly, S. Y., & Griffin, W. L. (2021). Deep lithosphere of the North China Craton archives the fate of the Paleo-Asian Ocean. Earth-Science Reviews, 215, 103554.