Last night (July 20, 2024), I received the final acceptance letter for our manuscript from Alison Hunt, the editor-in-chief of Nature Geoscience. While I am thrilled, I also feel a profound sense of calm. This moment reminds me of the numerous challenges and efforts I’ve endured—both in the field and at my computer. It brings back memories of countless sleepless nights, weekends, and holidays spent working. I recall the numerous failed simulations and subsequent retries, the physical exhaustion, and injuries from fieldwork. This research, spanning a decade, includes detailed geological mapping, testing, and simulation, representing a comprehensive and collaborative interdisciplinary study.

The trigger mechanisms of craton deformation are indeed a global challenge. Our comprehensive understanding presented in the paper is based not only on our long-term research in North China but also on my earlier research in the Western Interior Basin of North America during my visits to the University of Wyoming and the Colorado School of Mines (2001-2010) with Professor Dag Nummedal. During that time, I gained deep insights into the migration of dynamic subsidence centers induced by Farallon flat-slab subduction and the resulting basement-involved deformation. However, I was puzzled why such flat-slab subduction did not lead to the complete destruction of the North American craton. This suggests that flat-slab subduction is not the sole cause of craton destruction. The flat-slab subduction during the Laramide orogeny in western North America differs from the deep flat-slab subduction and rollback in the North China craton. As one of our paper's reviewers commented, "I actually only have one point of concern, and that is its ‘leaning on’ or confirming similarities with the Laramide western U.S. I do not think that we fully understand the western U.S. flat subduction period, …”. “I think the manuscript is stronger on its own focusing on China, but leave this to the authors." The North China craton is a typical example of studying decratonization.

Some scholars believe that the deep flat-slab subduction in North America experienced rollback during the Cenozoic. If this is the case, the subduction process of the Farallon plate should be consistent with that in the western Pacific region. According to our published findings in Nature Geoscience, the Colorado-Wyoming craton should have been completely destroyed like the North China craton, rather than attributing the ultimate decratonization of the Wyoming craton to the impingement of the Yellowstone plume upon the craton's base. Our latest research suggests that the deep flat-slab subduction in North America did not experience rollback in the later stages; perhaps only the trench retreated. We are currently documenting our findings on this topic.

The trigger mechanisms of craton deformation fully reflect the coupling and dynamics of the plate-mantle and deep-shallow Earth systems. The breakthrough in this field is a result of integrating CitcomS and GPlates developed by Gurnis and Müller et al. forming a unified global four-dimensional geodynamic modeling system. Through this comprehensive 4-D geodynamic modeling of the plate-mantle system, incorporating constraints from lithospheric deformation, mantle seismic tomography, and the evolution of surface topography, we found that craton deformation primarily arises from the evolution of the large mantle wedge due to oceanic flat-slab subduction and its subsequent rollback. Omitting either component results in incomplete craton destruction.

Future advancements in this field rely on leveraging insights from deep mantle structures revealed by seismic tomography, crustal deformation observations, and dynamic topography assessments of the Earth's surface. Constructing four-dimensional plate-mantle dynamic models represents a crucial step in enhancing our comprehension of this intricate phenomenon (Fig. 1). This involves accurately reproducing the evolution of surface topography under the influence of deep mantle and lithospheric processes. This requires extending research to the coupling of deep and surface processes, accurately recreating mountain uplift, basin subsidence, and sea-level changes.

Through this project's research, we discovered that craton destruction areas generally coincide with regions of flat-slab subduction and rollback. However, in areas where the slab has not yet arrived, the surface primarily exhibits large-scale uplift and subsidence. This uplift and subsidence can occur even before the main period of craton destruction, as seen in the Triassic of the North China craton. Because these regions have not yet undergone complete craton destruction, they form giant intracratonic basins rich in energy resources. The surface topography's response to deep processes can influence basin subsidence and sedimentation centers and control the evolution of intracratonic basins by altering sea level changes. This, in turn, affects the enrichment of significant energy resources. Therefore, geodynamic research is crucial for understanding the genesis of intracratonic basins near oceanic plate subduction zones and has significant implications for resource exploration. We plan to submit our findings in this area in the near future.

Reference

Liu, S., Ma, P., Zhang, B. & Gurnis, M. The horizontal slab beneath East Asia and its subdued surface dynamic response. Journal of Geophysical Research: Solid Earth 126, e2020JB021156 (2021).